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The current investigation was conducted at Shandaweel Agric. Res. Station, Sohag governorate, Egypt during 2018/2019 to 2020/2021 seasons. Pedigree selection of grain yield plant-1 was practiced independently from the F2 to F4 generations under normal and late planting dates. Evaluation was under both planting dates in the F4 generation. The phenotypic variance was slightly higher than the genotypic variance, and reduced from the F2 to F4 generation. Broad-sense heritability was 83.47 and 86.73% under normal planting compared to 88.22 and 89.03% under late planting after the first and second cycle of selection, respectively. The realized heritability was 37.75 and 40.63% under normal planting compared to 57.75 and 83.48% under late planting after cycle 1 and 2, respectively. The average observed gain of grain yield plant-1 after two cycles of pedigree selection was 12.59 and 25.33% from bulk sample and 7.45 and 2.69% from the better parent for normal planting selections, while it was 22.05 and 47.18% from bulk sample and 16.48 and 20.59% from the better parent for late planting selections, when the selected families were evaluated under normal and late planting conditions, respectively. The antagonistic selection increased the mean and decreased the sensitivity compared to the synergistic selection either evaluation was under normal or late planting conditions. Based on the path-coefficient analysis, number of spikes plant-1 had the greatest positive direct effect on grain yield plant-1 followed by number of kernels spikes-1 and 100-kernel weight in the base population and cycle two of selection under both planting dates.

Recurrent selection is a cyclical breeding procedure in which selection is made generation after generation, with a reunion of selected plants to produce a new population for the next cycle of selection. Maize (Zea mays L.) base population 'PSEV3' was developed by using selfed progeny recurrent selection in spring and summer crop seasons during 2014 to 2016. During Summer 2017, two improved maize populations [PSEV3-(S1)-C1 and PSEV3-(S2)-C2], original genotype (PSEV3-C0) and three check varieties (two OPV - open-pollinated varieties - Azam and Jalal, and HV - hybrid variety - Kiramat) were assessed for silking and yield traits across four environments including two planting dates and two sites i.e., Cereal Crops Research Institute (CCRI), Pirsabak - Nowshera, and University of Agriculture (UAP), Peshawar, Pakistan. Genotypes and planting dates enunciated significant (p≤0.01) differences for majority of the traits. Maize improved populations (C1 and C2) enunciated comparable values with early flowering and least cob height compared to base population and check genotypes. On average, PSEV3-(S2)-C2 was foremost and exhibited maximum mean values for yield traits with enhanced grain yield with optimum planting at CCRI, followed by PSEV3-(S1)-C1. Base population - C0 and check genotypes were observed with delayed silking and least grain yield across the environments. Selfed progeny recurrent selection was established as an efficient breeding method in improving maize base populations.

The base population for the recent study which is a yellow seed synthetic variety of maize was provided by Dr. M. Abd El-Sattar Ahmed, professor of crop science, Crop Science Department, faculty of Agriculture, Egypt. Two types of families had formulated, as a step before selection for high yielding ability. Those were half-sib (H.S) families and the first generation of self-pollination (S1) families. Variability in the base population gene pool had estimated depending on vari-ance components of the families. Reduction in mean values associated with S1 families relative to half-sib families reached 0.182, 1.18, 0.98, 3.88, 2.75 and 5.72% for leaves percentage, stem percentage, ear percentage, grain percentage, cob per-centage and husk percentage, respectively. Genotypic variances among S1 families was larger in magnitude than the respec-tive value for half-sib families in each measured botanical composition and dry matter partitioning characters. Meanwhile, within family’s variance, (σ2f), environmental variances (σ2e) had reduced in S1 families relative to half-sib families in each measured character. Genotypic variation among half-sib and S1 families were less than 20% of the studied botanical compo-sition and dry matter partitioning characters mean values, except for cob percentage and husk percentage that had a genotyp-ic variation amount to 24% and 26%, respectively. The estimates of additive variance (δ2A) were positive for all studied botanical composition and dry matter partitioning characters. While, the estimates of dominance variance (δ2D) were nega-tive for all characters, the ratio of δ2A/δ2G indicated that additive genetic variance was more effective in controlling all stud-ied botanical composition and dry matter partitioning characters. Estimates of heritability were higher in magnitude when calculated from first selfing generation (S1) compared to half-sib families, for all studied characters. Stem percentage ex-pressed the least estimate heritability among all studied characters in each family type (0.798 and 0.414 for half-sib and S1 families, respectively). This might indicate the influence of environment in the expression of that character. Meanwhile husk percentage had highest genetic control expressed on heritability estimates from the two studied types of families.

The present research was carried out through the three successive seasons from 2016/17 to 2018/19 at Shandaweel Agric. Res. Stat., Sohag Governorate, Egypt, to study the efficiency of pedigree selection in improving grain yield in bread wheat under normal and drought conditions. Two cycles of selection were completed under each condition for F2 to F4-generations. At the last season, the selected F4 families under each condition were evaluated under both conditions. The genotypic variance was slightly less than the phenotypic variance under both conditions and generally decreased from the base population (F2) to F4-generation. Broad-sense heritability was 78.33 and 71.93% under normal irrigation compared to 86.44 and 58.48% under water stress after cycle1 and 2, respectively. The realized heritability was 29.93 and 90.88% under normal irrigation compared to 36.47 and 89.48% under water deficit after cycle1 and 2, respectively. The average observed gains of normal irrigation selections were 40.29 and 66.34% from bulk sample and 29.92 and 35.27% from the better parent, while the average observed gains of water stress selections were 32.89 and 40.42% from bulk sample and 23.07 and 14.19% from the better parent, when evaluation practiced under normal irrigation and water stress, respectively. The results indicated that the synergistic selection was better than antagonistic selection in changing the mean and decreased the sensitivity

The present experiment has been carried out at the Poultry Experimental Farm, Faculty of Agriculture, Menoufia University, Shebin El-Kom, Egypt, during the period from 2013 to 2017 on Norfa chickens. Total number of 475 dams were used in the present experiment in the base population, first and second generations. Independent culling levels (ICL) method of selection has been applied on the selected flock (+0.5sd). The criterion of ICL method of selection was to select hens having at least average EN90d + 0.5 sd on condition that egg size and body weight should be around the average flock. Results obtained and conclusions can be summarized as follows: The heritability estimates (h2) showed that AgeSM had low h2 estimates, both of BWSM and BWM showed moderate h2 estimates, EWSM showed moderate to high h2 estimates while EWM had moderate h2 estimates and the heritability estimates for EN90d and EN42wk were moderate to high. The expected genetic changes for AgeSM, BWSM, BWM, EWSM, EWM, EN90d and EN42WK in the base population were -1.12 d. ، 41.82 g، 22.28 g ، 1.19 g ،0.46g ، 3.57egg and 1.70 eggs respectively. While the actual genetic gains were7.79، 17.9، -0.093، -1.60، -1.60، 5.18 egg and 8 eggs respectively. The expected genetic changes for AgeSM, BWSM, BWM, EWSM, EWM, EN90d and EN42WK) in the first generation of Norfa chicken were 1.69 d ، 22.43 g،31.01 g ، .89 g ،.32g ، 1.8 egg and 1.27 eggs respectively. While the actual genetic gains were -13، -29.9،-38، -1، -1.180،5.8 egg and 5.24eggs, in the same order. The expected genetic changes for AgeSM, BWSM, BWM, EWSM, EWM, EN90d and EN42WK in the first generation of Norfa chicken were 1.31 d., 26.14 g, .27 .73 g ,0 .87 g ,0.26 g , 2.95 egg and 2.91 eggs respectively. While the actual genetic gains were -10، -30، -22،-1.4، 1، 14.05 egg and 19.72 eggs respectively. The actual genetic gains for EN90d and EN42WK were high than the expected genetic changes through the base population, first and second generations by applied the Independent culling levels. The selected line was better than the control line for productive traits in Norfa laying hens.

International audience; AbstractBackgroundA common measure employed to evaluate the efficacy of livestock improvement schemes is the genetic trend, which is calculated as the means of predicted breeding values for animals born in successive time periods. This implies that different cohorts refer to the same base population. For genetic evaluation schemes integrating genomic information with records for all animals, genotyped or not, this is often not the case: expected means for pedigree founders are zero whereas values for genotyped animals are expected to sum to zero at the (mean) time corresponding to the frequencies that are used to center marker allele counts when calculating genomic relationships.MethodsThe paper examines estimates of genetic trends from single-step genomic evaluations. After a review of methods which propose to align pedigree-based and genomic relationship matrices, simulation is used to illustrate the effects of alignments and choice of assumed gene frequencies on trajectories of genetic trends.ResultsThe results show that methods available to alleviate differences between the founder populations implied by the two types of relationship matrices perform well; in particular, the meta-founder approach is advantageous. An application to data from routine genetic evaluation of Australian sheep is shown, confirming their effectiveness for practical data.ConclusionsAligning pedigree and genomic relationship matrices for single step genetic evaluation for populations under selection is essential. Fitting meta-founders is an effective and simple method to avoid distortion of estimates of genetic trends.

We assessed the impact of genetic divergence and the ability to combine corn hybrids used for the production of silage on the agronomic and bromatological traits of silage quality. We evaluated 18 corn hybrids used as genitors in a circulant diallel scheme in which each genitor hybrid participated in 9 hybrid combinations, and evaluated 100 treatments [18 genitor hybrids, 81 diallelic hybrids, and a commercial check hybrid (DKB330)] in a triple lattice 10 x 10 experimental design in two environments in Brazil. Genetic variability was adequate among the corn silage hybrids, and we can recommend the use of genitors 2B688 and P30B39 for the formation of a base population for intrapopulational breeding. The P30P34 hybrid is the best for intrapopulational breeding when aiming for silage with high protein content, low fiber content, and higher in vitro digestibility. Interpopulational breeding directed at improving silage digestibility can use a combination of genitors P30P34 and AS1572, but AS1572 and P30K64 are the most recommended. Hybrids 2B688, P30P34, and SG6015 are considered the most genetically distant of the others hybrids, and have desirable combining potential; therefore, they are important genitors for the formation of new segregated populations for improving corn silage.

Background: Metafounders are pseudo-individuals that encapsulate genetic heterozygosity and relationships within and across base pedigree populations, i.e. ancestral populations. This work addresses the estimation and usefulness of metafounder relationships in single-step genomic best linear unbiased prediction (ssGBLUP). Results: We show that ancestral relationship parameters are proportional to standardized covariances of base allelic frequencies across populations, such as Fst fixation indexes. These covariances of base allelic frequencies can be estimated from marker genotypes of related recent individuals and pedigree. Simple methods for their estimation include naïve computation of allele frequencies from marker genotypes or a method of moments that equates average pedigree-based and marker-based relationships. Complex methods include generalized least squares (best linear unbiased estimator (BLUE)) or maximum likelihood based on pedigree relationships. To our knowledge, methods to infer Fst coefficients from marker data have not been developed for related individuals. We derived a genomic relationship matrix, compatible with pedigree relationships, that is constructed as a cross-product of {-1,0,1} codes and that is equivalent (apart from scale factors) to an identity-by-state relationship matrix at genome-wide markers. Using a simulation with a single population under selection in which only males and youngest animals are genotyped, we observed that generalized least squares or maximum likelihood gave accurate and unbiased estimates of the ancestral relationship parameter (true value: 0.40) whereas the naïve method and the method of moments were biased (average estimates of 0.43 and 0.35). We also observed that genomic evaluation by ssGBLUP using metafounders was less biased in terms of estimates of genetic trend (bias of 0.01 instead of 0.12), resulted in less overdispersed (0.94 instead of 0.99) and as accurate (0.74) estimates of breeding values than ssGBLUP without metafounders and provided consistent estimates of heritability. Conclusions: Estimation of metafounder relationships can be achieved using BLUP-like methods with pedigree and markers. Inclusion of metafounder relationships reduces bias of genomic predictions with no loss in accuracy. Fil: García Baccino, Carolina Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Unidad Ejecutora de Investigaciones en Producción Animal. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Unidad Ejecutora de Investigaciones en Producción Animal; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentina Fil: Legarra, Andres. Institut National de la Recherche Agronomique; Francia. Instituto Polytechnique de Toulouse; Francia. École Nationale Vétérinaire de Toulouse; Francia Fil: Christensen, Ole F.. University Aarhus; Dinamarca Fil: Misztal, Ignacy. University of Georgia; Estados Unidos Fil: Pocrnic, Ivan. University of Georgia; Estados Unidos Fil: Vitezica, Zulma G.. Institut National de la Recherche Agronomique; Francia. Instituto Polytechnique de Toulouse; Francia. École Nationale Vétérinaire de Toulouse; Francia Fil: Cantet, Rodolfo Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Unidad Ejecutora de Investigaciones en Producción Animal. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Unidad Ejecutora de Investigaciones en Producción Animal; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentina

The purpose of this study was to evaluate the cost-effectiveness of the strategy of controlling the contacts of tuberculosis patients with latent tuberculosis infection by means of treatment with rifampin for 4 months or isoniazid for 9 months. The cost was the sum of the cost of treating latent tuberculosis infection in all contacts plus the cost of treating tuberculosis in whom the disease was not avoided. The effectiveness was expressed as cases avoided. The efficacy adopted was 90 % for rifampin for 4 months and 93 % for isoniazid for 9 months. We carried out a sensitivity analysis for efficacies of rifampin for 4 months of 80 %, 75 %, 69 % and 65 %. Of the 1,002 patients studied, 139 were treated with rifampin for 4 months and 863 were treated with isoniazid for 9 months. The cost-effectiveness waseuro436,842.83/50 cases avoided with rifampin for 4 months andeuro692,164.42/40 cases avoided with isoniazid for 9 months. Rifampin for 4 months was dominant. In the sensitivity analysis, rifampin for 4 months was dominant for efficacies of 75 % or greater. The cost-effectiveness analysis favoured the use of rifampin for 4 months when its efficacy was 75 % or greater.

El objetivo fue analizar el pedigrí de cuatro ganaderías mexicanas (Los Encinos=ENC, Montecristo=MCR, Fernando de la Mora=FMO y San José=SJO) a través de estimaciones de parámetros poblacionales tales como el tamaño de población base, tamaño efectivo, número de ancestros, aportaciones porcentuales e intervalos generacionales. Además se analizó el efecto de la consanguinidad sobre el comportamiento de los animales (tienta y lidia al caballo y al torero) con un modelo animal que consideró como efectos fijos a grupo contemporáneo (año-época de nacimiento-sexo, el efecto de sexo sólo en tienta) y las covariables lineales de edad y consanguinidad del individuo; los efectos aleatorios fueron el valor genético del individuo y el error. Los pedigríes incluyeron de 3246 a 8279 animales nacidos entre 1904 y 2006; la información de comportamiento data de 1978 a 2006, variando de 202 a 2776 observaciones. Las consanguinidades promedio variaron entre 2,4% y 12,9%, con máximos individuales de 47,7% en MCR y de alrededor de 40% en las otras ganaderías. El número de ancestros como proporción de la población de referencia en MCR fue 12,3%, mientras que en FMO, ENC y SJO representaron 17,7%, 27,8% y 34,0%, respectivamente. Tres animales explicaron 50% del pedigrí en MCR y 13 o menos en las otras ganaderías. Los tres ancestros de MCR explicaron 22,6% y 20,2% del pedigrí de SJO y ENC, respectivamente. Las ganaderías MCR, SJO y ENC tienen un origen común. Las tendencias anuales de consanguinidad fueron negativas en ENC y SJO (-0,13±0,02 y -0,25±0,02, respectivamente; p

A two-way selection experiment in Lebistes reticulatus is described. The character selected for was weight at 63 days and the experiment was run for nine generations. The selection was started from a base population in which sib analyses did not reveal any significant estimates of the component of additive genetic variation for weight at 63 days. The selection was performed between full sibs within aquaria. A weak response was obtained, but its magnitude was smaller than the differences between generation means. Compared to the high selected line fitness was decreased in the low line.

A divergent, eight generation selection experiment on uterine capacity in rabbits was performed. Rabbit does were ovariectomized unilaterally before puberty, and selected for increased and decreased litter size by ‘best linear unbiased prediction’ using data from up to four parities. Two different analyses were performed to estimate the response to selection. The first was based on least squares analysis; the second was based on Bayesian methods using Gibbs sampling techniques. Three different priors were used for variance components, but these had little influence on the results. Posterior means of heritabilities for uterine capacity, varied from 0.09 to 0.12, and repeatabilities from 0.18 to 0.22. The response to eight generations of selection was symmetrical and led to a divergence of 0.16 young rabbits per generation, which amounts to about 2% of the average litter size of the base population per generation. The pattern of response however, was not linear: a high initial response was followed by a period where little further response was observed, and a final burst of response was obtained during the last two cycles of selection. Analisis Bayesiona de la Respuesta a la seleccion por capacidad uterina en conejos Se llevo a cabo un experimento de seleccion divergente por capacidad uterina en conejos. Las conejas fueron ovariectomizadas unilateralmente antes de la pubertad, y fueron seguidamente seleccionadas para aumentar y disminuir el tamano de camada mediante un BLUP que incluia datos de hasta el cuarto parto. Se realizaron dos tipos de analisis para estimar la respuesta, el primero basado en minimos cuadrados y el segundo en tecnicas bayesianas con la ayuda de muestreo de Gibbs. Aunque tres a prioris diferentes fueron usados para las componentes de varianza, esto apenas influyo en los resultados, pues las medias posteriores para las heredabilidades variarton de 0.09 a 0.12 y las medias de las repetibilidades variaron de 0.18 a 0.22. La respuesta a ocho generaciones de seleccion fue simetrica y condujo a una diverjencia de 0.16 conejos por generacion, lo que representa un 2% de la media de la poblacion base por generacion. La respuesta no fue, sin embargo, lineal: una fuerte respuesta inicial fue seguida de un periodo de estancamiento y una nueva respuesta en los dos ultimos ciclos de seleccion. Eine Bayes Analyse zu Auswirkungen der Selektion auf uterine Kapazitat beim Kaninchen Ein Selektionsexperiment mit divergierender Selektion wurde uber acht Generationen durchgefuhrt. Die Zibben wurden vor der Geschlechtreife einseitig ovarektomiert und auf hohere und niedrigere Wurfgrose uber Best Linear Unbiased Prediction (BLUP) selektiert. Daten von bis zu vier Trachtigkeiten wurden verwendet. Zwei verschiedene Analysen wurden verwendet um den Selektionserfolg zu bestimmen. Die erste basierte auf der Least Square Analyse, die zweite auf der Bayes Methode des Gibbs Sampling. Drei verschiedene Priors wurden in der Varianzkomponentenschatzung verwendet, aber sie hatten wenig Einfluss auf die Endergebnisse. Die a posteriori Ergebnisse fur die Heritabilitaten der uterinen Kapazitat variierten von 0,09 bis 0,12, die Wiederholbarkeiten von 0, 18 bis 0,22. Die Selektionserfolg uber acht Generationen war symmetrisch und fuhrte zu einem Unterschied von 0,16 Jungtieren pro Generation, was ca. 2% der durchschnittlichen Wurfgrose, bezogen auf die Basispopulation je Generation, entspricht. Das Bild des Zuchtfortschritts war nicht linear: nach einem hohen Anfangserfolg wurde eine Periode geringen Erfolges beobachtet und ein Ende des Zuchtfortschrittes wurde in den letzten zwei Generationen erreicht.

Broilers that survived unilateral pulmonary artery occlusion and lived to maturity comprised the first generation (GEN1) of an ascites-resistant line. Progeny from the GEN1 line previously were shown to tolerate fast growth and cool temperatures with a 50% lower incidence of ascites than chicks from the breeder pullet line serving as the base population for the resistant line. In the present study, progeny from the GEN1 line were subjected to unilateral pulmonary artery occlusion, and survivors were reared to breeding age to serve as the parent stock for the second generation (GEN2) ascites-resistant line. In two experiments (EXP1 and 2), chicks were reared separately by sex but were mixed by line within environmental chambers, where they were grown as rapidly as possible and exposed to cool (14 C) temperatures from 17 to 49 d of age. In EXP1, the ascites incidences in the base population, GEN1, and GEN2 lines, respectively, were 31% (48/157), 15% (8/52), and 4% (3/69) for males and 10% (13/128), 11% (5/46), and 3% (1/36) for females. In EXP2, the ascites incidences in the base and GEN2 lines, respectively, were 44% (71/163) and 6% (7/110) for males and 12% (19/155) and 0% (0/92) for females. The final BW for nonascitic broilers did not differ across lines in EXP1. In EXP2, the final BW was lighter for nonascitic GEN2 males (2,915±43 g) and females (2,382±17 g) than for nonascitic base population males (3,088±42 g) and females (2,493±22), respectively. Right:total ventricular weight ratios were higher for ascitic than nonascitic broilers, confirming the primary role for pulmonary hypertension in the pathogenesis of ascites. These experiments demonstrate ongoing improvement in the ascites resistance of progeny from broiler breeders that, for two consecutive generations, have survived the rigorous selection pressure imposed by unilateral pulmonary artery occlusion.

The aim of this study was to determine the point prevalence of ulceration of the leg in an Australian community. This was a population-based epidemiological study. Two hundred and fifty-nine patients with leg ulceration were identified by health care professionals of all types working in hospitals and private practices, as well as by self referral from patients. The base population in the study area was 238,000. The following data were recorded: age, sex, site of ulceration, duration of ulceration, history of previous ulceration and patient mobility. The point prevalence was 0.11%. The male:female ratio was 1:1.9; however the age related prevalence was similar for both sexes. The age related prevalence of ulceration was similar to that found in two similarly conducted studies in the United Kingdom. The ulcers were a chronic problem with 24% having been present for more than 1 year. Thirty-five per cent of patients had had a problem of ulceration for more than 5 years and 20% had suffered 10 or more episodes of ulceration. Related immobility was a prominent factor with 45% of patients being housebound. Chronic ulceration of the leg is a common recurrent problem in the elderly population and is likely to increase as the population grows. There is a definite need to improve the method of treating this problem.

SummaryMaximum likelihood estimation methods with an individual animal model were used to analyse a bi-directional selection experiment, with control, for cannon bone length in Scottish Blackface sheep. A method is described for partitioning the likelihood to allow within- and between-line estimates of genetic variance. It is concluded that both sources of information made substantial contributions to the precision of the base population heritability estimate. The implications for different experimental designs and varying heritability are discussed.

A study was conducted to determine BW, feed intake, feed efficiency, and carcass composition changes following 51 generations of selection for high 4-wk BW in Japanese quail. Quail lines utilized were the P line selected for high 4-wk BW on a normal 28% CP diet and the unselected base population (C line) from which the P line originated. Body weight, feed intake, and feed efficiency data were collected daily from 1 to 28 days, whereas percentage carcass water, ash, protein, and total lipid data were obtained at 0, 4, 7, 10, 14, 21, 28, 42, and 56 days of age. Body weights of P line quail were significantly (P.05) larger than BW of C line quail at all ages with the greatest deviation occurring at the age of selection. Feed intake was significantly greater in the P line and paralleled BW increases. When feed intake was adjusted for differences in BW, P line quail consumed less feed per gram of BW than C line quail and adjusted feed intake declined with age after Week 1. The P line quail had superior feed efficiency compared with C line quail from 1 to 13 days of age with the greatest deviation immediately posthatch. Carcass composition determinations revealed significant (P.05) age and line effects. Both percentage ash and protein increased from hatch to 14 days and thereafter remained constant. However, percentage water and total lipid demonstrated contrasting responses to increasing age; percentage water declined whereas percentage total lipid increased. The P line quail had less carcass water and protein, but had more lipid.(ABSTRACT TRUNCATED AT 250 WORDS)

The effectiveness of selection for hen-days without beak-inflicted injuries was studied. The base population was known to have a high incidence of beak-inflicted injuries when pullets' beaks were intact. Data from the foundation stock yielded nonsignificant family heritability estimates ranging from .05 to .17, depending on length of the test period (varying from 16 to 28 to 16 to 40 wk of age) and number of six-hen cages per family (one to three). Selection was practiced on sire family groups of either 30 or 36 pullets. Birds used for selection were housed six birds per cage and had intact beaks. The criterion of selection was mean hen-days without beak-inflicted injuries from 16 to 40 wk of age. Three selected and three unselected strains were involved. After two generations, mean hen-days without beak-inflicted injuries from 16 to 40 wk of age were 164.8 and 155.3 for selected and unselected stocks, respectively, yielding a realized family heritability of .65 ± .13 (SE). Selection did not appear to alter the relative frequency of beak-inflicted injuries by body regions affected; about 30% of all injuries involved the vent-cloacal area. Egg production traits were measured also. No differences were detected in Generation 1, but selected pullets had higher hen-housed rates of lay and egg mass in Generation 2. It is tentatively concluded that stocks having high levels of cannibalism when kept with intact beaks can benefit from selection against beak-inflicted injuries when evaluated by techniques similar to those used in the present study.

1. After 5 generations of selection on income minus food cost between 21 and 40 weeks of age (SECR), a correlated genetic improvement of 14.5% and 16.3% of the base population mean could be observed for income minus food cost between 41 and 60 weeks (IF60) in two lines of laying hens. The total responses up to 60 weeks amounted to 17.2% and 17.3% of the base population mean. A heritability of 0.30 for IF60 and a genetic correlation of 0.61 between SECR and IF60 were estimated. 2. The correlated relative genetic responses for 5 traits of the period between 41 and 60 weeks of age for the two lines were: 4.3% and 5.2% in egg number, 5.8% and 7.4% in egg weight, 8.4% and 10.8% in egg mass, ‐2.7% and ‐0.6% in body weight at 60 weeks, and ‐5.2% and ‐6.3% in food efficiency. 3. The estimated heritabilities of these 5 traits from the whole data set were 0.36, 0.75, 0.34, 0.71 and 0.17. The estimated genetic correlations between SECR and the same 5 traits were 0.30, 0.46, 0.61, ‐0.22 and ‐0.49. 4. A high ...

SummaryTo simplify the description of selection in two environments the terms ‘ antagonistic’ and ‘synergistic’ are used. Selection upwards in a bad environment or downwards in a good environment is antagonistic, the selection and the environment acting in opposite directions on the character. Synergistic selection is the reverse, upwards in a good environment or downwards in a bad, selection and environment acting in the same direction. Published experiments are reviewed to see how well they agree with two expectations. First, Jinks & Connolly (1973) showed that antagonistic selection reduces environmental sensitivity and synergistic selection increases it. The experiments reviewed showed many exceptions to this rule, but they all showed that sensitivity was less after antagonistic than after synergistic selection. This is shown to be simply the consequence of correlated responses being less than direct responses. Second, I suggested (Falconer, 1989) that antagonistic selection might be the best way to improve the mean performance in the two environments. In the experiments reviewed, antagonistic selection was significantly better than synergistic for changing the mean, but it is now shown that there is no theoretical justification for this expectation; if one type of selection is better in one direction the other ought to be better in the other direction.Expressions are given for the changes of mean performance and of sensitivity resulting from selection in one or other environment; these changes can be predicted from the parameters of the base population. In the experiments reviewed, an increase of mean performance accounted for 49% or more of the upward response. Equations are presented which allow the variance of mean performance, the variance of sensitivity, and the covariance of mean with sensitivity to be derived from parameters estimated in an unselected population, namely the variances in the two environments and the corresponding covariance. The variance of sensitivity that might be ascribed to scale effects is deduced. Directional selection in a single macro-environment is synergistic with respect to the micro-environmental differences, and is expected to increase environmental sensitivity and consequently to increase environmental variance. Stabilizing selection is antagonistic selection in both directions at the same time, and so is expected to decrease environmental variance.

Chicken lines that were either resistant or susceptible to ascites syndrome were developed by using a hypobaric chamber to induce the disease. Birds were reared in a hypobaric chamber that simulated high altitude by operating under a partial vacuum, which thereby lowered the partial pressure of oxygen. Ascites mortality data from birds reared under hypobaric chamber conditions were used to select siblings to be used for breeding. The response to selection for the susceptible (SUS) and resistant (RES) lines of chickens was very rapid from the base population, which exhibited an incidence of ascites of 75.3%. Extremes in the incidence of ascites were observed in generation 8, with line SUS exhibited an average incidence of ascites of 95.1%, and in generation 9, with line RES exhibited an average incidence of ascites of 7.1%. The incidence of ascites in the relaxed line remained relatively stable and currently has a general incidence of ascites of 60%. The heritability estimates ± SE for ascites were estimated to be 0.30 ± 0.05 and 0.55 ± 0.05 for lines SUS and RES, respectively. Changes in the incidence of ascites appeared to be associated with livability. By generation 10, selection for ascites in line RES increased livability by 11.5 d, whereas in line SUS, livability was decreased by 8 d. Although divergent selection for ascites resulted in a reduction in d 42 BW for both the SUS and RES lines, the SUS line was approximately 163 g heavier than the RES line. Negative genetic correlations between ascites and the right ventricle:total ventricle (RV:TV) ratio were observed in both the SUS and RES lines; however, no significant change in the RV:TV ratio was observed for birds reared under normal conditions in either line. The current data raise questions about the validity of using the RV:TV ratio as an indicator trait in a selection program designed to reduce the incidence of ascites. Overall, direct selection for resistance to ascites by using sire family performance appeared to be an effective means of reducing the incidence of ascites. However, simultaneous selection for BW should be applied to counterbalance the losses in correlated BW.

Previously, evaluation of the first 2 wk of daily growth velocity with an artificial neural network (ANN) provided an effective noninvasive approach for predicting the susceptibility of broilers to pulmonary hypertension syndrome (PHS). This study was conducted to define the minimum number of days of growth data and the type of ANN required for the best prediction of PHS susceptibility. Four experiments were conducted in which broilers were weighed daily at 0800 h. In Experiment 1, Hubbard male broilers were reared to 50 d of age, with 13 developing PHS and 33 remaining normal (N), for a PHS:N ratio of 13:33. In Experiment 2, ANAK broilers were exposed to cool temperatures (16 to 17 C) from 17 to 42 d of age, resulting in a PHS:N ratio of 16:46 for males. In Experiments 3 and 4, Hubbard male and female chicks from a base population and a PHS-resistant line were exposed to cool temperatures from 17 to 42 d (Experiment 3) or 49 d of age (Experiment 4). The PHS:N ratios were 40:68 for males and 6:96 for females in Experiment 3 and 26:91 for males and 10:58 for females in Experiment 4. Four ANN, back propagation (BP3), Ward back propagation (WardBP), probabilistic (PNN), and general regression (GRNN), were evaluated for their ability to predict PHS in the shortest number of days based on daily growth velocities (BWd+1-BWd). A 100% prediction of PHS and N birds was considered the criterion of success. Starting with 14 d of data, each ANN was trained on daily growth velocity, and the number of predictive days was reduced with each run of the ANN. The best ANN was a GRNN, which correctly diagnosed PHS and N male broilers on 4 and 6 d of growth velocity data for Experiments 1 and 2, respectively. The results were poorer with the BP3, WardBP, and PNN. The diagnostic ability of the neural network was not consistent over all four experiments. In Experiment 2, a minimum of 6 d was required for 100% PHS detection for males. In Experiment 3, the best diagnostic value for males was 93% PHS detection and 100% N detection at 15 d. For females, the 100% PHS detection occurred at a minimum of 8 d. In Experiment 4, males had 100% PHS and N detection at a minimum of 11 d. Females had a 100% PHS and N detection at a minimum of 10 d. An attempt to build a single neural network that would detect PHS susceptibility in Hubbard (Experiment 1) and ANAK (Experiment 2) broilers was unsuccessful. The application (validation) of neural networks between experiments also was not successful (data not presented). However, these studies demonstrate that within a breed or line reared under similar selection pressures for ascites, a GRNN based on the first 14 d of growth velocity can detect, with at least 93% accuracy, broilers susceptible to PHS.

Previous research has shown that a line (F) of turkeys selected long-term for increased 16-wk body weight was more susceptible to challenge with washed Pasteurella multocida than a randombred control line (RBC2), the base population of F. A previous study also indicated that the mortality of the F line following challenge with P. multocida was similar to that of sire lines from two of the three major primary breeders. The purpose of the present study was to compare the resistance of the sire line from the third major primary turkey breeder (C) not previously studied with that of the F and RBC2 lines to determine whether there is variation in resistance among the sire lines from three major primary breeders. The sire lines from all three primary breeders were used in the production of commercial turkeys. Body weights of the F line were greater than those of the C line at the time of challenge with P. multocida. Both the C and F lines were heavier than the RBC2 line. The birds were challenged at 6 wk of age with a field isolate of washed P. multocida (1.2 x 10(7) organism per bird of capsular serogroup A and somatic serotype 3,4). Mortality was recorded daily for 14 d. Mortality following challenge with P. multocida was higher in the F line than in the C line, and both large-bodied lines had higher mortality than the RBC2 line. Based on the present results and those published in the literature, there may be variation in resistance among commercial sire lines from the three major primary breeders.

The effect of long-term genetic selection on physical quality and composition of eggs was determined by analyzing eggs acquired from Agriculture Canada: Ottawa Control Strain 5 (CS5) from a 1950 base population, 7 (CS7) from a 1958 population and 10 (CS10) from a 1972 population. Eggs from the HN "Nick Chick" current commercial strain (CCS) were also included. Eggs were collected monthly over a 62-wk laying period and analyzed for egg, albumen, shell and yolk weight; albumen protein, solids and pH; percentage yolk solids and fat; Haugh units; and specific gravity. Significant (P0.05) differences found between strains included a progressive increase in weight of eggs from the CS5 to CCS. Although the eggs increased in size, no significant differences were found between strains for specific gravity or percentage shell weight. Yolk weights of eggs from the strains examined did not differ. However, the percentage of yolk found in current strain eggs was significantly lower (P0.05), with a subsequent higher percentage albumen due to the increase in egg size of the CCS. Haugh units were significantly higher in the CS10 and CCS strains than in the other strains. No significant differences between strains were seen in albumen protein, solids, pH, or yolk solids. Mean percentage yolk fat assay values for eggs from the CS5, CS7, CS10, and CCS strains were 33.08, 32.68, 32.84, and 32.40, respectively. Percentage yolk fat values obtained from CCS were significantly lower (P0.05) than those obtained from the other strains. The results from this study indicate that genetic selection has produced larger eggs containing a lower percentage of yolk while overall egg quality has been maintained or improved.

The mouse lines were developed by long-term selection for fatness, after which the fat line (F) had about a 5-fold (23% vs 4%) higher fat percentage than the lean (L) line at 14 weeks; but the lines differed little in fat-free body weight. To assess the contribution of genetic changes in leptin hormone level to the selection response, plasma leptin levels were assayed in these lines in generation 60 and in an unselected control (C) from the same base population. With access to food prior to assay, the F, C and L lines had 16·5, 0·91 and 0·26 ng/ml leptin, respectively. In fasted animals these levels were much lower: 2·98, 0·171 and 0·0087 ng/ml, respectively. Thus the leptin levels differ greatly between the lines, with the fattest mice showing the highest level: almost 20 times higher than the control and 60–300 times higher than the L line. These correlated selection effects are an order of magnitude greater than the direct selection response, and believed to be much larger than seen for any hormonal or other trait. Correlations between leptin level and fat amount were high (over 0·86) in fed or fasted animals of the F line, indicative of leptin resistance.

The use of diagnostic ultrasonography has profoundly enhanced the practice of obstetrics. Its use on a routine basis in pregnancy, though, is still debated. We evaluated a policy of routine second trimester ultrasonography in our base population to determine if it improved obstetrical care. In comparison to a historical control group, our study group had fewer patients going beyond 42 weeks and a significantly lower Cesarean section rate for those requiring an induction for post dates. The use of routine antenatal ultrasonography improved obstetrical care in our population.

This paper presents a general expression to predict breeding values using animal models when the base population is selected, i.e. the means and variances of breeding values in the base generation differ among individuals. Rules for forming the mixed model equations are also presented. A numerical example illustrates the procedure. Cet article présente l’expression générale pour prédire les valeurs génétiques par le modèle animal quand la population de base est sélectionnée, c’est-à-dire quand cette population est un mélange de sous-populations à moyenne et variances génétiques différentes. On présente les règles de construction des équations du modèle mixte. La procédure est illustrée par un exemple numérique.

1. Heritabilities and genetic correlations in the base population of a closed strain of Muscovy duck, moderately selected for body weight at 10 weeks of age, have been estimated from the data of 9 successive generations for the following traits: male and female body weight at 10 and 18 weeks of age (BW10m, BW18m, BW10f, BW18f) and length of the 8th primary feather at 10 weeks of age (F110m, F110f). 2. Multivariate REML with an animal model was used, pooling data from the 9 generations (3283 and 3289 male and female offspring respectively). The same trait expressed in male and female was considered as 2 different traits. 3. The 8th primary feather was longer in females than in males by 6% to 22% at 10 weeks of age. Body weight was heavier in males than in females by 42% to 58% at 10 weeks of age and by 57% to 75% at 18 weeks of age. 3. The heritability estimates for body weight traits showed moderate values, being a little higher for females than for males at the same age, increasing with age from h2=0.24 at BW10m to h2=0.43 at BW18f. 4. The heritability estimates for feather length showed that a greater response would be obtained in selection for male feather length (h2=0.37) than for female length (h2=0.14). Both have high genetic correlations with body weight so they could be indirectly improved. 5. Heritabilities of the difference in body weights between males and females at 10 weeks (h2=0.07) and 18 weeks of age (h2=0.10) were small, as well as for feather length (h2=0.10). It would probably be difficult to modify sexual dimorphism in body weight through selection. 6. Genetic correlations between BW10m, BW18m and BW10f, BW18f were respectively r(g)=0.77 and r(g)=0.80. They were larger for body weight at the same ages between males and females, r(g)=0.90 (r(g)=0.88 between F110m and F110f). Body weight in males and females at the same age should be better considered as 2 different traits in a selection programme. 7. The cumulated predicted genetic gains expressed per unity of the genetic standard deviation (sigma(g)) over the 8 generations of selection were 1.3 sigma(g) and 1.4 sigma(g) respectively for the BW10m and BW10f. The predicted correlated responses were 1.2 sigma(g) for body weights at 18 weeks of age, 0.9 sigma(g) and 0.7 sigma(g) for F110f and F110m respectively.

To The Editor: The report by Huang et al. entitled "Osteolysis in Failed Total Knee Arthroplasty: A Comparison of Mobile-Bearing and Fixed-Bearing Knees" (2002;84:2224-9) was timely because mobile-bearing articulations are becoming increasingly popular as a possible way to avoid or delay polyethylene wear and osteolysis. The authors conclude that "the prevalence of osteolysis was higher in the knees with a mobile-bearing prosthesis than in those with a fixed-bearing prosthesis." Although this is certainly a valid conclusion for the small, specific cohort studied, readers must resist the temptation to infer that mobile-bearing knees in general will have a higher osteolysis rate than fixed-bearing knees. To make this conclusion, some critical information must be supplied. First, what is the base population from which the revisions in each group came? For example, if the sixteen of thirty-four mobile-bearing revisions that were associated with osteolysis came from a cohort of …

SummaryMarker Assisted Selection (MAS) based on additive effects associated with alleles at marker loci, estimated by linear regression of individual phenotype on the markers, was applied to characters with non-additive gene action and non-additive environment. The base population was the F2generation of a cross between two inbred lines. Computer simulations of MAS were conducted for characters with dominance, epistasis and genotype-environment interaction approximated by the ‘additive-multiplicative’ model. MAS was more effective than purely phenotypic selection in all cases. The efficiency of MAS for characters with non-additive gene actionis comparable to (and for negative dominance even higher than) the efficiency of MAS for strictly additive characters. Environmental non-additivity, however, lowers the efficiency of MAS. Almost all results concerning the efficiency of MAS in our previoussimulations of purelyadditive traits are applicable to non-additive traits.

Two experiments were conducted to determine the protein requirement of quail lines (P and T) following selection for increased 4-wk BW under normal-protein (28% CP) and low-protein (20% CP) diets, respectively. Quail progeny from Generation 39 breeders were fed diets containing 18, 21, 24, and 27% CP from 0 to 5 wk of age in Experiment 1, whereas in Experiment 2, quail progeny from Generation 79 breeders were fed diets containing 18, 21, 24, 27, and 30% CP from 0 to 4 wk of age. Quail from the unselected base population (C line) were also included in both experiments. Significant line, diet, and line by diet interactions were present in both experiments. At 2 wk of age, T line quail were significantly (P < .05) larger than P line quail across diets, whereas by 4 wk, BW of P line quail were significantly larger than those of T line quail. Across dietary protein levels, quail receiving diets containing 24% CP or higher were significantly larger than those receiving the 18 and 21% CP diets. Quail in both the P and C lines had larger BW with increasing protein levels and an apparent protein requirement between 24 and 27% CP. However, quail in the T line showed no BW response to increased protein levels, indicating that long-term selection for increased BW on a 20% CP diet had altered the protein requirement in this line.(ABSTRACT TRUNCATED AT 250 WORDS)

Fearfulness was measured as latency to recover from induced tonic immobility using White Leghorn hens from a population originated by crossing three different strains selected for egg number and egg weight. Realized heritability was calculated in a single generation selection experiment with eight replicates, each consisting of 76 40-wk-old females from which 21% were selected for decreased tonic immobility duration. A randomly selected control population was maintained for each replicate. Separately from this experiment, fear differences between ages and sexes were investigated at 1, 2, 4, 8, 12, 16, 20, 24, 28, and 32 wk. The realized heritability (.32 +/- .10) indicates that induced tonic immobility should respond to selection. It was numerically higher than the estimate calculated by half-sib analysis of variance in the base population (.18 +/- .07); the logarithmic transformation did not yield higher heritability estimates. Crossing effects were evaluated in two different crossbreds, i.e., Leghorn x Castellana and Buff Prat x White Prat, which suggested important negative heterotic effects for this fear-related trait (-31% and -54%, respectively). Significant (P < .05) quadratic and cubic variation between 1 and 32 wk of age was obtained in females and males, respectively; the involvement of these age effects make it difficult to generalize about realized heritability for tonic immobility. Tonic immobility increased from 32 to 72 wk. Differences between the sexes were apparent, males showing longer tonic immobility durations than females except in the postjuvenile period before sexual maturity, suggesting a relationship between this trait and hormonal changes.

A breed improvement programme has been initiated at both ADAS Redesdale (Scottish Blackface) and ADAS Pwllpeiran (Welsh Mountain) to improve carcass conformation of hill ewes. From a base population of 1100 Welsh Mountain and 1600 Scottish Blackface ewes, nucleus flocks of 60 ewes have been established. Selection of ewes into the nucleus flock at each site has been based on their ability to consistently produce wether lambs crops with good conformation and above average carcass weights when selected for slaughter at a fat class 2/3L. The next objective is to replicate these ewes through multiple ovulation and embryo transfer (MOET) since theoretical studies (Smith, 1986) indicate that this can substantially increase the rates of genetic improvement through the female line. However, to date little work has been conducted to determine whether this technology can be successfully applied to hill sheep maintained in harsh hill environments in the UK, and this formed the basis of the current study.

SUMMARYIndividual and within-full-sib family selection for low sternopleural bristle number was carried out for 17 generations, with six replicate lines for each selection method. Our results can be summarized as follows: (1) the response to selection was exhausted very quickly, (2) the additive variance of the selected lines declined rapidly, (3) the variation in response to selection decreased as selection progressed, (4) genetic differences among replicates at the selection limit were small, (5) individual selection resulted in a higher initial response than within-family selection, but similar limits were achieved with both procedures. These observations are consistent with the hypothesis that the pattern of response to selection is due to the segregation in the base population of only a few loci with large effects, at intermediate frequencies.

One cycle of divergent sib selection, for or against abdominal fat weight, combined with within-family selection for body weight, was performed in a population of a commercial female grandparent line (White Rock type). Chicks from the first generation (S1 G1) of high-fat (HF) and low-fat (LF) selection lines were raised in three different environmental and climatic conditions. A second generation (S1 G2) of the selection lines was obtained by within-line selection for body weight only. The HF line had about 60% more abdominal fat than the LF line in all three environments. The realized heritability of this trait was calculated to be .73, almost identical to the heritability estimated from the base population. The LF line mean body weight was between 1% and 5% lower than that of the HF line. This difference was not significant and it was almost abolished in S1 G2, after both lines were selected for body weight only. The difference between lines in abdominal fat weight was increased to 80% in S1 G2. It can be concluded that reduction in abdominal fat weight was not associated with a decrease in body weight. Selection for body weight, in a line previously selected against abdominal fat, did not reverse the reduction in fat. The difference between the HF and LF lines had the same magnitude in both sexes and under different environmental conditions that increase or decrease fat deposition.

Carcass composition of turkeys from a long-term growth-selected line (F), a subline (FL) of F selected only for increased shank width, and a randombred control population (RBC2) that served as the base population for F, were compared. Birds of both sexes were killed at 16 wk of age in the fifth and sixth generations in Line FL. A commercial sire line (C) was also included in the sixth generation. Body weight increased at comparable rates in F and FL males through the 5th generation of selection in Line FL, but the BW of FL males was significantly smaller than that observed in F males in the 6th generation. Body weights of FL females were significantly lower than BW of F females in both the 5th and 6th generations, resulting in a significant line × sex interaction. A similar interaction was also observed in both generations in the actual weight of most leg bones, leg muscles, and breast muscles. When expressed as a percentage of live BW, most of the latter line × sex interactions were not significant. Genetic increases in shank width of the FL line were associated with increases in the relative weight of all leg bones measured and drumstick muscles. This may have contributed to the improved walking ability consistently observed in FL males relative to that of F males. In general, genetic increases in BW in Line F were associated with a decreased amount of relative support (leg muscles and leg bones) in comparison with that observed in Line RBC2. These results support the hypothesis that a portion of the leg problems observed in large-bodied turkeys are attributable to an inherent weakness of body support structures resulting from the slower growth of these structures relative to that of total BW.

Selection for post-weaning weight gain in mice from 21 to 42 days, on either a full or restricted feeding level during this period was carried out for seven generations. Control lines were maintained for each feeding level. The rate of selection response was higher on full feeding due to a higher heritability and a larger phenotypic variance. Realised heritabilities of 0.29±0.05 and 0.19±0.04 for selection on full and restricted feeding respectively, were in close agreement with base population estimates.Selection on full feeding led to positive correlated responses in 21 day weight, 42 day weight, food intake and efficiency between 21 and 42 days, and 42 day tail length, but with little change in reproductive performance.Correlated responses to selection on restricted feeding were reduced 21 day weight, but an increase in 42 day weight and increased efficiency from 21 to 42 days. However, overall reproductive performance fell.

1. Data from 16 inbred lines derived by three generations of full sib mating from a common outbred base population were used to estimate genetic correlations between body weight, abdominal fat content, follicle number, liver weight, egg weight and egg number using between‐line variances and covariances. 2. High genetic correlations were found between body weight, fat content and egg weight. Low genetic correlations were found between follicle number and all traits other than egg weights. 3. Theoretical expectations and low correlations within lines led to the conclusion that environmental correlations among the traits considered were very low.

Genetic differences in body fat, body weight, follicle number, and egg production were found among six inbred lines of White Leghorn hens derived from a common outbred base population. High positive genetic correlations of body fat with body weight were found between inbred lines as well as between inbred parents and line-cross progeny. Heterosis of fatness, body weight, egg production, egg weight, and liver weight were observed. Large follicles and liver weight were unaffected by inbreeding and crossing of lines.

The ontogeny of plasma growth hormone (GH) was determined within and between genetically-related turkey lines selected for differential growth rates. Blood samples were obtained at weekly intervals from hatching through 195 days of age from male and female poults of a slow-growing, randombred line (RBC-2), representing the base population, and a fast-growing line selected over 20 generations from RBC-2 for increased 16-wk body weight (F). Growth rate of the F line exceeded that of RBC-2 during the very early (0 to 14 day) posthatch period (P less than .05), but was not different from that of the RBC-2 line by 77 to 195 days of age. Males of both lines were larger than females at all ages (P less than .05). Plasma GH increased from hatching until 2 wk of age and declined thereafter in both lines. Differences between overall plasma GH concentrations of the lines were not observed during the 0 to 14 day period, but concentrations were higher (P less than .05) in RBC-2 than F birds thereafter (21 to 195 days of age). Plasma GH concentrations initially (0 to 14 days) were higher in females than in males for both lines (P less than .05), but thereafter (21 to 195 days) declined more rapidly and averaged lower overall in females than in males (P less than .05). Correlations between measures of GH and growth rate within lines over age were strongly positive (r = .83 to .93; P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

SUMMARYFor one-, two- andn-locus models of a quantitative trait assumed to be determined by overdominant loci, it is shown that the mean of an inbred line will be equal to or larger than the mean of the base population if the original gene frequencies satisfy a condition which is generally a function of the degree of overdominance and of the genotypic values.

Data has been presented on the loss of alleles from populations of small fixed size. Emphasis has been placed on the effect which the allele frequency distribution and the interlocus distribution of heterozygosity will have on the pattern of allelic loss. Rare alleles are rapidly lost during the initial sampling period, and continue to be lost for several generations following the establishment of small population size. The nonequilibrium nature of the process of loss of genetic variability is stressed. The rapid loss of rare alleles and the preservation of intermediate and high frequency alleles will result in (1) heterozygosity declining much more slowly than allele number, and (2) the establishment of genetically similar populations when sampled from the same base population.

During the years 1973 to 1976 two populations of Pearl millet with wide genetic base, namely, Delhi composite (DC) and Vijay composite (VC) were used to compare the response to selection by the full-sib family method from biparental material and reciprocal recurrent selection (RRS). The results indicated that it was possible to advance grain yield with one cycle of RRS by about 23 percent in the case of population DC and 21 percent in population VC, while for the full-sib selection method, the improvement in grain yield was not so rapid. The studies on the nature of gene action indicated that both additive and dominance gene actions were important for grain yield, ear length and ear girth. The coefficient of variation as a result of RRS was reduced in population DC, while it was comparable to base population in the other population. The correlation studies indicated that the magnitude of favourable correlation of different characters with grain yield were higher in case of RRS compared to the full-sib system. The presence of negative correlation of plant height with grain yield in both the improved populations indicated the possibility of breakage of unfavourable gene combinations through RRS and full-sibs developed from biparental mating.

Responses to single trait selection on individual phenotype and sire-family mean phenotype for survivor's egg weight and rate of lay were measured for a single generation in 13 replicates. Each replicate-selection criterion-trait subclass consisted of eight sire families or 72 females measured and was reproduced from the best 25% of the families or individuals. The realized heritability of egg weight was 0.39 and that of rate of lay was 0.31, both of which were significantly greater than zero but not significantly different from the predicted values based on halfsib correlations in the base population.The standardized response to sire-family selection was less than the response to individual selection for both traits and the difference was significant for rate of lay (0.10; 0.31) but not for egg weight (0.22; 0.39). The predicted responses to sire-family selection were less than those for individual selection for both traits, and the observed responses to sire-family selection were not significantly different from the predicted values for either trait.These experimental results do not disagree with the theoretical expectations of the relative efficiencies of individual and sire-family selection.

The effect of fetal and maternal genotype on embryo survival was studied in two lines of mice from the same base population: line E, selected for high embryo survival, and line CN-, selected for small litter size. Embryos were collected at 3.5 days postcoitus from normally mated donors of both lines and were transferred to the uteri of 2.5-day pseudopregnant recipients from each line. The number of embryos recovered and the proportion of those recovered that had been fertilized were greater in line E donors than in line CN- donors (P < .05). Development into blastocysts was slower for CN- embryos. The proportion of recipient females that were pregnant was higher for line E than for line CN- after transfer of line E embryos (P < .005). The same trend was observed following transfer of line CN- embryos (P < .10). Embryos of both lines showed greater survival when transferred to line E recipients than when transferred to line CN- recipients (P < .005), and, within line E recipients, E embryos tended to survive better than did CN- embryos (P < .10). The results suggest that although the genotype of the embryo may play a role, the maternal genotype has greater influence on embryo survival in the two lines of mice.

Feed intake and feed conversion patterns of meat-type dwarf (dw) and normal contemporaries were investigated in two trials, with the Athens-Canadian randombred line used as the base population. Dwarf chickens consumed significantly less feed than normal ones the first day posthatching and in all subsequent observation periods. The deviation in body weight ratios and feed intake ratios between lines were greatest during week 1. These data indicate that the action of the dw gene is present at hatching and exerts at least part of its influence through feed intake or appetite. Feed conversion ratios (feed/gain) were lower in dwarf birds than in normal birds during week 1, whereas overall differences across 8 weeks were small. The difference in relative growth rate between genotypes was greatest during week 1; by week 4, relative growth rates were similar.

Summary The theoretical and practical implications of population size on selection programmes are reviewed. Short term responses can be predicted from genetic variances and depend little on the distribution of gene effects and frequencies. The main influence of population size (N) is through selection intensity, and is important only if these are reduced to minimize inbreeding. The variability of short term response is approximately inversely proportional to N. As the time scale increases, the mean and variance of the response can not be predicted accurately from the usual genetic parameters estimated in the base population. The probabilities of fixation of favourable genes and thus the limit to selection from genetic variability in the base population increases with N, but not linearly; only for genes initially rare or of small effect does N substantially influence the limit. The long term response from new variation created by mutation is, however, very dependent on N. The fixation probability of additive or dominant mutant genes initially in single copy is independent of N and the number of mutants and thus response is proportional to N. Although it may be many generations before mutants contribute significantly, their contribution to response may eventually be very large. Resume Effets de la grandeur des populations sur selections a court- ou long terme Les resultats des selections a court terme peuvent etre predits des variances genetiques et dependent peu de la distribution des effets des genes et des frequences. L'influence principale de la grandeur de population (N) est pratiquee par l'intensite de selection et devient important uniquement lorsque celle-ci est reduite pour minimiser la consanguinite. Lorsque les laps de temps augmentent, valeur moyenne et variance de la population de base echouent comme ressource pour la prediction exacte du progres. La probabilite de la fixation de genes favorables et, de ce fait, la limite de selection, augmente avec N, cependant pas lineairement; seulement pour les genes initialement rares ou d'effet mediocre, l'influence de N est importante. Le resultats a long terme de variations nouvelles creees par mutation est tout de meme tres dependant de N. La probabilite de fixation des genes additifs ou dominants est independante de N, de ce fait, le succes est proportionnel a N. Bien que beaucoup de generations sont necessaires pour que les mutantes montrent une repercussion significative, leurs contribution au succes peut finalement etre tres large. Resumen Efecto del tamano de la poblacion sobre seleccion a corto y largo plazo Se revisan implicaciones practicas y teoricas del tamano poblacional sobre programas de seleccion. Respuesta de seleccion a corto plazo, pueden ser predecidas a traves de las varianzas geneticas y dependen poco de la distribucien de frecuencias y efectos genicos. La mayor influencia sobre el tamano poblacional (N), es a traves de la intensidad de seleccion y es importante solo si se disminuye mediante la minimizacion de la consaguinidad. La variabilidad de respuesta a corto plazo es aproximadamente inversamente proporcional a N. A medida que el tiempo transcurre, la media y la varianza de la respuesta, no pueden ser predecidas con exactitud desde los parametros geneticos usuales, estimados en la poblacion base. La probabilidad de fijacion de los genes favorables y por consiguiente el limite de seleccion, desde la variabilidad genetica en la poblacion base aumenta con el N., pero no linealmente solamente para genes inicialmente raros o de pequeno efecto, tiene N una influencia sustancial sobre el limite. La respuesta a la seleccion a largo plazo, debido a nueva variacion producida por mutacion, en comparacion, depende fuertemente de N. La probabilidad de fijacion aditiva o dominante de genes mutantes, es independiente de N y del numero de mutantes, y la respuesta por consiguiente es proporcional a N. Sin embargo, pueden transcurrir muchas generaciones antes que los mutantes contribuyan significativamente, su contribucion a la respuesta puede eventualmente ser muy grande. Zusammenfassung Wirkungen der Populationsgrose auf kurz- und auf langfristige Selektion Kurzfristige Selektionserfolge konnen von genetischen Varianzen vorhergesagt werden und hangen nur wenig von der Verteilung von Genfrequenzen und – wirkungen ab. Der Haupteinflus der Populations-grose (N) wird uber Selektionsscharfe ausgeubt und wird dann wichtig, wenn diese wegen Inzuchtminimierung vermindert wird. Mit zunehmenden Zeitraumen versagen Mittelwert und Varianz der Ausgangspopulation als Hilfsmittel zu genauer Vorherschatzung des Fortschrittes. Die Wahrscheinlichkeit der Fixierung erwunschter Gene und damit die Selektionsgrenze, nimmt mit steigendem N zu, allerdings nicht geradlinig; nur bei anfanglich seltenen Genen oder solchen mit geringer Wirkung, ist der Einflus von N bedeutend. Der langfristige Erfolg durch mutationsbedingte neue Variabilitat hangt dagegen stark von N ab. Die Wahrscheinlichkeit der Fixierung additiver oder dominanter Einzelgene ist von N und von der Zahl der Mutanten unabhangig, so das der Erfolg proportional mit N zunimmt. Obwohl viele Generationen verstreichen mogen bevor Mutanten sich signifikant auswirken, kann ihr Beitrag zum Erfolg schlieslich sehr gros sein.

INTRODUCTION FOR several decades geneticists have selected animals for maximum body size and growth rate, but have paid little attention to the physiological changes which underlie, or are correlated with, the observed genetic advances. Since a knowledge of the mechanisms controlling growth is of both scientific and practical interest, development and investigation of experimental and commercial strains of animals selected in divergent directions for growth has begun at a number of stations. At the University of Massachusetts, fifteen generations of breeding have developed, from a single base population, two strains of White Plymouth Rock chickens having vastly different rates of growth. In the twelfth generation, the 8-week body weight of these “high” and “low” lines differed by a factor approaching three (Farrington, 1966). Previous investigation has explored the endocrinological differences which may be related to this drastic divergence in growth rate (Komiyama et al., 1965; Farrington, 1966; Farrington and Mellen,…

INTRODUCTION UNDER floor housing a bird’s position in the peck order, and her aggressiveness are correlated with her egg production (Sanctuary, 1932; Guhl, 1953; McBride, 1958, 1964). This effect is most probably related to her ability to freely obtain food and water. McBride (1958) suggested that selection for egg production under floor housing would lead to an increase in relative aggressiveness. The experiments described in this paper were designed to determine whether the relative aggressiveness of two lines of White Leghorn poultry selected for increased part-record egg production under floor housing had changed relative to that in their unselected base population. MATERIALS AND METHODS The lines of White Leghorns used were S275, S% and O.C.S. (the Ottawa Control strain of Gowe et al., 1959). S275 originated in 1955 from a sample of O.C.S. and has been selected for number of eggs from housing (147 to 156 days of age) till…

KRISTA et al. (1970) reported marked and parallel responses to selection for high and low blood pressure in three strains of Broad White turkeys. The divergence between the means of the high and low populations averaged 10, 17 and 25% for the first three generations. The pooled regression estimate of heritability for the low line was 37% and for the high line 26%. Similar heritability estimates of 25% and 28% for high and low blood pressure, respectively, were reported for chickens by Sturkie et al. (1959). The progress made in diverging the high and low blood pressure populations of turkey selected from the same base population and the high heritability estimates obtained indicate that there is considerable additive genetic variance associated with the blood pressure trait in the turkey. Because of space limitation and other considerations it was necessary to combine the three high blood pressure lines and the three…

SCIENTIFIC literature contains many reports on weights of glands and tissues of young chickens. Due to large variations of both genetical and environmental origin in the data reported, it has been impossible to establish any weight standards for specific tissues at specific ages of the chicken. This report attempts to provide such standards for early growth periods of a population readily available to research workers. The population was developed at Cornell University (King, Carson and Doolittle, 1959) and is being maintained as a base population for the Regional Poultry Breeding Project of the North Central States. Since 1959, the Ohio population of the randombred stock has been reproduced from 40 paired matings according to the design proposed by Gowe, Robertson and Latter (1959) for maintenance of Randombred Controls with a minimum of genetic change. MATERIALS AND METHODS Since age of dam has been proven to affect the relative weight of…