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The effects of udder type, calving assistance (CA) and other factors on preweaning average daily gain (ADG) and weaning weight of beef composites were analysed. Cows with medium or large, well attached udders weaned faster growing and heavier ( P P P P

A dynamic deterministic model for simulating beef cattle production systems is developed to evaluate the effects of production traits and management strategies on the bioeconomic efficiency of beef production systems. The model, named Alberta Beef Production Simulation System (ABPSS), is composed of four major submodels: herd inventory, nutrient requirement, forage production, and economic submodels. The herd inventory submodel is used to simulate population dynamics and feed requirements in the herd. The nutrient requirements submodel is mainly based on the 1996 version of the National Research Council (NRC). It is used to evaluate nutrients and feed requirements for calves and cows depending on their physiological status (maintenance, growth, lactation and gestation) and the climatic condition. The forage production sub-model is used to predict forage growth rate, cattle grazing rate, available forage biomass and total hectares required for grazing. The economic submodel measures bioeconomic efficiency, as net return per cow, by subtracting total cost from total return. The nutrient requirements predicted by ABPSS were compared with those recommended by the NRC for testing. The results that were predicted by the NRC model and ABPSS model were similar, as expected. Sensitivity analyses showed that cow mature weight, milk production, calf weaning weight and feed prices were the most critical input parameters in the model. It must be noted that the model was developed based on available experimental results and data from the literature and, due to the unavailability of a suitable data set, the model could not be validated. We suggest that the ABPSS has the potential for providing a useful method for simultaneous consideration of many factors in an integrated system, which could be helpful to beef cattle extension specialists and cow-calf production managers for assessing the potential effects of different management and selection strategies on bioeconomic efficiency. Key words: Beef cattle, simulation and modelling, production system, optimization

A dynamic simulation model, Alberta Beef Production Simulation System (ABPSS), which includes herd inventory, nutrient requirements, forage production, and economic submodels, was used to compare bioeconomic efficiency in spring and fall calvings and different weaning ages (220, 200, 180, 160, and 140 d). Comparisons were made assuming a mature cow weight of 550 kg and a peak milk yield of 8.2 kg d−1. The first day of calving was assumed to be 28 March and 8 September for spring- and fall-calving cows, respectively. Bioeconomic efficiency was measured as the net return per cow (total return minus total cost). Fall calving in Alberta generally results in longer exposure of young calves to extreme cold weather after calving, and therefore total annual DMI and feed cost were higher in the fall-calving season group than in the spring-calving season group. Bioeconomic efficiency improved as weaning age increased from 140 to 220 d in both calving seasons. For weaning age of 200 d or less, spring calving was more efficient than fall calving. However, at a weaning age of 220 d, fall calving had higher bioeconomic efficiency than spring calving, primarily due to higher market prices for fall-born calves. This indicated that interactions of calving season by weaning age was an important factor affecting bioeconomic efficiency. It must be noted that the model was developed based on experimental results and data from the liteature, and due to the unavailability of suitable data the model could not be validated. We suggest that the ABPSS model has the potential for providing a useful decision-making tool for simultaneous consideration of many factors in an integrated system and for evaluating the effects of alternative management strategies on profitability of beef production systems. Key words: Beef cattle, simulation and modelling, production system, calving season, weaning age, bioeconomic efficiency

A total of 96 weaned bull and heifer calves were allocated by sex, breed and horn status to three management treatments, each with two levels: calves handled every 10 or 20 days; an electric prod used or not used; and calves restrained by the head or not. The behavior responses were measured by five incremental progressive force requirement categories (1=no stimulus applied, 2=voice and hand slap, 3=voice and slap with a PVC tube, 4=tail twist and 5=whatever reasonable force was required to move the animal forward) and Transit Time (TT). These progressive force requirement categories were (Snell) transformed, converted to Maximum Force Scores (MFS) and analyzed as a continuous variable. Transit Time was the time in seconds required for cattle to move a distance of 11 m in the chute. The response measurements were made on all animals on days 0, 20, 40, 60 and 80 and defined as five periods in the analysis. Dehorned and polled cattle responded similarly to being handled more or less frequently, receiving or not receiving a repeated electric prod and being restrained by the head or not. There were no significant (P>0.05) two-way interactions between horn status and the management practices, handling frequency, prod and head gate retainment, nor were the three-way interactions between horn status, management practices and period significant (P>0.05), indicating that the overall and across period, behavior responses of dehorned and polled cattle were similar for the three management practices. Maximum Force Score and TT were higher in the calves handled every 10 days indicating that the calves reacted negatively to more frequent handling but they habituated and MFS and TT were reduced as the study progressed. The response to being restrained in the head gate was significant (P

The data for the study were obtained over an 11 yr period and the number of observations varied from 2663 to 4263 depending on the trait that was studied. The objective was to compare the reproduction and growth traits of genetically horned and polled cattle in three synthetic lines of beef cattle. No differences (P > 0.05) were observed between horned and polled cattle in all lines for pregnancy, calving and weaning rates, calf birth and weaning weights, calf preweaning average daily gains, dystocia score, cow weights and cow condition scores at calf birth and calf weaning. We advocate the use of polled cattle for breeding, which is a welfare friendly alternative and circumvents the need for dehorning. Key words: Horned, polled cattle, dehorning, reproduction, growath

Early (April) vs. late (May/June) calving was compared over 3 yr at the University of Alberta Ranch at Kinsella, Alberta, Canada. Three synthetic lines, two of which were predominantly beef breeds (BS1 and BS2) and one with approximately 60% dairy breeding (DS) were used and 995 records were analyzed. Cows from each line were randomly allotted to the early or late breeding schedules at the time of breeding. The same bulls bred cows in their own line, beginning in June and in August for two 6-wk periods. Calving season had no significant effect (P > 0.05) on pregnancy rate (%), calving assistance, calving and weaning rate (%), adjusted off-test weight or post-weaning ADG, suggesting that late calving can be a viable management option. Birth weights of all calves were significantly lower in the early group than in the late group (38.9 vs. 41.2 kg, P −1, P −1, P 0.05). The early calves were older at weaning and therefore were expected to have higher pre-weaning ADG. The fact that the late-born calves in the DS line equalled the early calves in pre-weaning ADG indicates that they were growing relatively faster. Late calving DS heifers had significantly higher weights (P

Records on 983 cows born during a period of 10 yr (1966 to 1975) were used to estimate longevity and lifetime productivity of cows raised under range conditions. The cows were from a purebred Hereford and two multibreed synthetic groups, one composed of beef breeds (Beef Synthetic #1) and the other composed of two-thirds dairy breeds and one-third beef breeds (Dairy Synthetic). The cows were raised under a stringent culling system in which all heifers were exposed to bulls as yearlings and were expected to wean a calf each year thereafter or they were culled. Cows were also culled for other reasons, such as severe calving problems, bad udders, and leg and feet problems. The mean longevity was 4.2 yr; cows from the synthetic breed groups produced longer (P < .01) than Hereford cows, due to a relatively faster rate of removal at all ages in the purebred Hereford group. The mean values per cow for lifetime productivity traits were 2.7 and 2.5 for number of calves born and weaned and 101.9 kg and 482.9 kg for weight of calf born and weaned, respectively. Male calves were not castrated, and weights of female calves were adjusted to a male basis. Over their lifetimes, Dairy Synthetic cows were more productive, in terms of number and weight of calves born and weaned, than Beef Synthetic #1 cows, which in turn were more productive than purebred Hereford cows (P < .01).

Data from carcasses of 210 cattle (119 bulls and 91 steers) from four breed-types, serially slaughtered from approximately 200 to 800 kg liveweight were used to test the hypothesis of similar gender dimorphism among breeds in relation to carcass muscle growth and distribution. Relative to total side muscle, breed types tended to have similar growth coefficients for all muscle groups, but differed significantly in the adjusted mean weights of 7 of the 9 muscle groups. Earlier maturing compared to later maturing breed-types had a lower proportion of the early maturing muscle groups and a higher proportion of the later maturing muscle groups. Gender dimorphism in relative growth rate was significant for 2 of the 9 muscle groups. At the same total side muscle, bulls as compared with steers showed a shift in muscle weight distribution towards the forequarter, similar proportion of muscle in the pistol and less proportion of muscle the in distal hindlimb and abdominal wall. Breed × gender interaction were only significant (though minor) for the proportion of muscle in the proximal hindlimb and the distal forelimb.

Reasons for disposal were determined for 983 cows from a purepred Hereford and two multibreed synthetic groups; all were born in the 1966–1975 period. One synthetic group (Beef Synthetic #1) was composed mainly of beef breeds, while the other synthetic group (Dairy Synthetic) had 64% dairy breeding. The cows were managed under a stringent culling policy under which any cow failing to wean a calf each year was culled. Cows were also culled for unsoundness and other defects. The mean longevity was 4.2 yr, with 16 yr being the maximum age attained by any cow. The highest percentage of cows was disposed as 2-yr olds (first calvers). Death losses accounted for 8.8%, while culling for reproductive failure, calf survival problems, calving problems and udder problems accounted for 51.3, 12.1, 10.9 and 7.7% of all disposals, respectively. Culling for reproductive failure was the major reason for disposal at all ages, although its relative importance diminished with advancing age. Culling for udder problems was of greatest significance in 6-yr-old and older cows. Culling for calf survival problems was higher (P

Muscle and bone distribution was examined in 11 mature Double Muscled and 12 mature normal muscled (Beef Synthetic) cows which were slaughtered between 470 and 620 kg liveweight. Expressed as a percentage of total side muscle significant differences between Double Muscled and normal cows were found in 42 of the 95 muscles and in four of the nine anatomical muscle groups. In Double Muscled carcasses there were shifts in muscle weight distribution towards the more fleshy, expensive and superficial muscles. Double Muscled cows had proportionately less muscle in the distal hindlimb, distal forelimb, deep muscles in the thicker parts of the carcass and neck muscles than normal cows. Muscular hypertrophy revealed an increasing inner-outer gradient across the muscle layers, with the superficial and bulkiest muscles being the most hypertrophied. The humerus, carpus and os coxa of the Double Muscled cows formed lower proportions of total bone weight than they did in normal cows. Along the vertebral column Double Muscled cows had greater percentages of lumbar and thoracic vertebrae than normal cows but a smaller percentage of cervical vertebrae though the differences were not significant (P > 0.05).

Genetic and phenotypic parameters of growth traits from birth to 1 year of age were compared in a multibreed Beef Synthetic (SY) and a purebred Hereford (HE) population managed together under the same environmental conditions and selected for growth rate from 1961 to 1979. Growth traits studied were birth weight, preweaning and postweaning gains. Records of 2077 calves of 70 HE and 100 SY paternal half-sib families were used for analysis. Except for birth weight, phenotypic variances of growth traits were similar for the synthetic (SY) and purebred (HE) populations, but genetic variances were larger in SY than in HE for all growth traits except postweaning gain in males. The coefficients of variation were comparable for all the traits studied in the two populations, indicating that phenotypic variations in the multibreed population and the purebred population were similar. Key words: Variance components, heritability, beef cattle

Phenotypically dehorned (genetically horned) and polled bulls were similar for birth, weaning weight, pre- and post-weaning ADG, carcass weight, grade fat, marbling, rib-eye area, cutability and carcass grade. Polled bulls had higher (P

To elucidate the effect of selection for increased growth upon growth efficiency (gain:feed), growth and feed consumption patterns were studied in three lines of mice. Two of the mouse lines (H lines) had been selected for high 42-d body weight while the third was an unselected foundation (FP) population. The two H lines differed in population size and were designated as the high-large (HL) and high-small (HS) lines. Logistic growth curve analysis revealed that, in terms of growth rate and mature body size, the three lines could be ranked as HL > HS > FP. When considered relative to age, the feed consumption of the H line mice exceeded that of FP mice. When growth efficiency was considered relative to body weight, HL mice exhibited a significantly higher efficiency than either HS or FP mice. However, when considered relative to degree of maturity (body weight/asymptotic body weight), differences in growth efficiency were greatly reduced. This effect of maturity upon growth efficiency is compatible with the previous suggestion (Taylor and Murray 1987) that many growth-related variables are strongly associated with an animal's "target" mature body weight. A corollary of this suggestion is that much of the well characterized selection responses, of "high-growth" selection lines, may be accounted for by genetic differences in a factor associated with the elevation of their target mature body weight. Key words: Growth-selected mice, growth efficiency, mature body weight

Analyse demographique d'un troupeau de race pure Hereford et d'un troupeau synthetique multiracial de bovins a viande. Les enregistrements des carrieres des femelles nees de 1966 a 1975 sont utilises pour estimer et comparer les parametres demographiques d'un troupeau de race pure Hereford (HE) et d'un troupeau synthetique multiracial (SY1) de bovins a viande, soumis tous 2 a une politique de reforme rigoureuse dans laquelle toute genisse ou toute vache ne produisant pas un veau sevre par an etait eliminee. La taille moyenne instantanee de la population etait de 118 vaches et 39 genisses dans le troupeau HE, de 155 vaches et 56 genisses dans le troupeau SY1. Le troupeau SY1 etait un ensemble composite d'origine multiraciale comprenant 33% de Charolais, 33% d'Angus et 20% de Galloway, le reste provenant d'autres races bovines a viande. Les 2 troupeaux etaient conduits de maniere identique. Neuf parametres issus de l'analyse des carrieres des femelles sont etudies : la probabilite, a la naissance, de survivre jusqu'a un âge donne ; le quotient de survie Px (probabilite, a un âge donne, de survivre jusqu'a la classe d'âge suivante) ; l'esperance de vie a un âge donne (nombre moyen d'annees restant a vivre a une femelle atteignant l'âge x) ; le quotient de fecondite (probabilite pour une femelle, a un âge donne, de produire une fille) ; la contribution relative d'une femelle d'un âge donne a la procreation des generations futures ; le taux net de reproduction Ro (nombre moyen de filles de remplacement produites par une femelle) ; le taux instantane d'accroissement de la population (r) et l'intervalle de generation (T). On observe des differences entre les 2 troupeaux sur les parametres demographiques specifiques de l'âge, le troupeau SY1 presentant des valeurs plus elevees que le troupeau HE. Le troupeau SY1 presente des valeurs moyennes plus elevees que le troupeau HE pour le taux net de reproduction Ro (1,57 ± 0,11 contre 1,21±0,15 ; p < 0,07) et pour le taux instantane d'accroissement r (0,09 ± 0,01 contre 0, 03 ± 0,02 ; p < 0,04), ce qui indique un taux d'accroissement de la population plus eleve dans le troupeau SY1. L'intervalle de generation T est plus eleve (p < 0,01) dans le troupeau SY1 que dans le troupeau HE (5,09 ± 0,11 contre 4,25 ± 0,19 annees). Ces resultats montrent qu'une meme conduite et qu'une meme politique de reforme peuvent se traduire par des parametres demographiques differents, phenomene resultant sans doute dans cette etude d'un effet d'heterosis sur la survie des veaux dans le troupeau synthetique d'origine multiraciale SY1. Sur la duree, la politique rigoureuse de reforme entraine une reduction des parametres Ro, r et T jusqu'a un point ou la taille du troupeau HE ne peut plus etre maintenue (Ro < 1 en 1972 et dans les cohortes ulterieures).

Records on 983 cows born during a period of 10 yr (1966 to 1975) were used to estimate longevity and lifetime productivity of cows raised under range conditions. The cows were from a purebred Hereford and two multibreed synthetic groups, one composed of beef breeds (Beef Synthetic #1) and the other composed of two-thirds dairy breeds and one-third beef breeds (Dairy Synthetic). The cows were raised under a stringent culling system in which all heifers were exposed to bulls as yearlings and were expected to wean a calf each year thereafter or they were culled. Cows were also culled for other reasons, such as severe calving problems, bad udders, and leg and feet problems. The mean longevity was 4.2 yr; cows from the synthetic breed groups produced longer (P.01) than Hereford cows, due to a relatively faster rate of removal at all ages in the purebred Hereford group. The mean values per cow for lifetime productivity traits were 2.7 and 2.5 for number of calves born and weaned and 101.9 kg and 482.9 kg for weight of calf born and weaned, respectively. Male calves were not castrated, and weights of female calves were adjusted to a male basis. Over their lifetimes, Dairy Synthetic cows were more productive, in terms of number and weight of calves born and weaned, than Beef Synthetic #1 cows, which in turn were more productive than purebred Hereford cows (P.01).

The heritabilities for and the genetic, phenotypic, and environmental correlations among calving difficulty scores (CDS) and measures of size of the pelvic inlet were estimated using 547 records of 2-yr-old heifers from three synthetic breed groups. Calving difficulty score was treated first as a trait of the dam and then as a trait of the calf and was analyzed on three scales: raw scores from 0 to 3 (0 = normal birth, 3 = most difficult delivery requiring a hard pull, veterinary assistance, or surgical intervention), Snell-transformed scores, and a binary (0, 1) scale. Estimates of heritability for CDS as a trait of the dam were similar to those when it was considered a trait of the calf. Heritability estimates for CDS on the raw and transformed scales were similar and moderate in magnitude (.36 +/- .15 to .47 +/- .18) but were higher than most reported estimates. However, on the binary scale the estimates were lower (.26 +/- .17, .28 +/- .14). Estimates of heritability for the horizontal and vertical pelvic diameters and the pelvic area were high, implying that pelvic size in heifers might be readily modified by selection. The genetic and phenotypic correlations between CDS as a dam trait and pelvic dimensions were low, whereas the correlations between CDS and dam weight at calving were moderate. As a calf trait, CDS was highly correlated genetically with calf birth weight, but the phenotypic correlations were moderate.

Long limb bones were dissected from 30 Camborough x Canabrid pigs serially slaughtered at birth, 14, 28, 56, and 84 d of age to determine the growth patterns of long limb bones (humerus and radius for the forelimb and femur and tibia for the hindlimb) in relation to live weight from birth to 84 d of age, weighing up to approximately 31 kg. Relationships between individual long limb bone measurements (Y) and live weight or transformations of live weight (X) were evaluated using allometric analyses. Hindlimb bones tended to have higher growth coefficients than forelimb bones (P.05), suggesting an anterior-posterior gradient of long limb bone growth. However, centripetal gradients of growth for long limb bones were not evidential (P.05). Greater diameter growth compared with length growth of the long limb bones indicated that the differentiation in growth for diameter and length of the long limb bones was an effective response to the functional requirements of standing, walking, and running following birth.

A trial is reported comparing fat distribution in carcasses from bulls and heifers of two breed-types: Hereford (HE) and Dairy Synthetic (DY). Twelve bulls and twelve heifers of each breed were grouped four to a pen at weaning (163 ± 15.1 (SE) days), and serially slaughtered from that time to approximately 16 mo of age. After slaughter, one side of each carcass was broken into eight wholesale cuts, which were separated into fat (subcutaneous fat (SF), intermuscular fat (IF), and body cavity fat (BCF)), muscle and bone. Depot fat accretion in each cut was investigated using the allometric equation with side fat weight as the independent variable. Coefficients for SF were significantly higher in the rib, chuck and flank for HE carcasses than for DY carcasses and higher in the rib and flank for heifers than for bulls. At equal total side fat, HE carcasses had significantly more SF in the brisket and in the loin than DY animals. Heifers had significantly more fat in the loin than bulls. Differences among coefficients for IF relative to total fat were minor for both breed and sex. At equal total side fat, HE carcasses had less fat distributed intermuscularly than DY carcasses and had less IF in the brisket than heifers. The results are discussed in relation to the Canadian beef grading system.

An investigation was carried out to study factors influencing milk yields and milk constituents among range cows. June and September measurements of milk yield and constituent percentages of butterfat (BF), protein (PT) and lactose (LT) were taken using 206 and 222 cows in 1976 and 1977, respectively. The cows, representing four beef and dairy-beef breed groups, were from the University of Alberta beef herd and ranged in age from 2 to 10 years. Regression of milk yield on calf age (CA) demonstrated a negative association over the lactation period measured, although regression coefficients were not statistically significant. Associations between all constituent yields with CA were negative. However, regression coefficients of June and September constituent percentage variables on CA indicated a more positive association as lactation progressed. Cow weight loss during gestation, cow weight at calving and ADG during lactation did not account for a significant proportion of the variation in either milk or constituent yields or constituent percentages over and above main effects. The association between cow ADG during lactation and all yields was negative although not statistically significant. Calf birth-weight was positively associated with all yields, and showed negative association with BF% and PT%. Calf average daily gain measured from birth to September was highly associated with yields of milk and constituents, declining from June to September. Its association with BF% and PT% was negative. Cow calving interval was introduced as a possible factor influencing milk yields of 3- and 4-yr-old and mature cows. Its association with lactation performance was however, not significant. Key words: Lactation, range cows

The eating quality and consumer acceptance of roasts from semitendinosus (ST) muscle and longissimus dorsi (LD) muscle from mature, marbled beef and from regular Canada Choice or Good beef were compared. Cooking losses for ST roasts were similar; however, mature, marbled LD roasts had significantly greater total cooking and drip losses than regular beef LD roasts. Differences in volatile losses of LD roasts were not significant. Sensory evaluation indicated that both types of beef were generally similar. Although significant (P

Eighteen bulls each of double-muscled (DM), Beef Synthetic (SY) and Hereford (HE) breed types, serially slaughtered from about 250 to 800 kg live weight, were used to examine muscle-bone relationships in double-muscled and normal cattle.Relative to total side bone, DM animals differed significantly from the other breed types in relative growth rate of muscles in all regions which exhibited gross muscular hypertrophy. They showed generalized and regionally differentiated muscular hypertrophy. At equal bone weight in the given anatomical region, DM/HE and DM/SY muscle:bone ratios were respectively: proximal hindlimb 1·35 and 1·24; proximal forelimb 1·25 and 117; back and loin 1·20 and 1·10; and the expensive regions 1·30 and 1·20. In the limbs of DM animals, muscular hypertrophy in the proximal region was associated with bone hypotrophy while minimal muscular hypertrophy in the distal parts was associated with relatively heavier bones. Consequently, increased muscle:bone ratios were most pronounced in the proximal region, which suggests that muscles in these animals had increased in weight without proportionate increase of bones, i.e. muscle and bone growth were to some extent independent. Bone response in the distal limbs may have been influenced by a relative increase in weight support function.

This study was performed in two parts. In the first part, 349 calving records of 2-yr-old heifers in 1979, 1980 and 1981 were analyzed by least-squares to assess the effects of lowering sire birth weight on calf birth weight and ease of calving. The study demonstrated that using sires with lower birth weight in 1981 compared to 1979 and 1980 (31.12 vs. 40.12 and 40.17 kg, respectively), reduced the average calf birth weight (32.65 vs. 36.04 and 34.62 kg, respectively) which in turn improved calving performance of the heifers in 1981 compared to the previous years. In the second part, 128 calving records of 2-yr-old heifers in 1981 were analyzed to study the relative importance of hip height, area of pelvic opening, condition score and weight at calving on calving performance. The results indicated that heifer weight at calving had a significant influence of calving performance (P

Muscle weight distribution was compared by jointing and complete tissue separation of carcasses from 277 young male progeny of eight sire breeds and two dam breeds, serially slaughtered at 300 kg live weight, 12 months and 15 months of age. The sire breeds were Simmental, Charolais, Danish Red and White, Romagnola, Chianina. Hereford, Blonde d'Aquitaine and Limousin; the dam breeds were Danish Red and Danish Black Pied.Growth impetus for muscle in each joint was established from the allometric equation (Y = aXb). Growth coefficients, b, were homogenous among breeds, indicating similar muscle development patterns over the range of weights studied. Growth impetus waves increased centripetally on the limbs, caudocephalically on the whole of the body (being more marked dorsally) and dorsoventrally on the trunk.There were small but significant breed differences in the proportion of muscle in different joints at similar total muscle weight. They probably reflect differences in maturity and other minor functional influences. Chianina and Hereford crosses were the two extremes for muscle distribution with many of the remaining breed groups being very similar. Differences were already established by 300 kg live weight and muscle growth patterns were similar among breeds over the range of the experiment.

Fat growth and distribution were studied by jointing and complete tissue separation of carcasses from 277 young bull progeny of eight sire breeds and two dam breeds, serially slaughtered at 300 kg live weight, 12 and 15 months of age. Growth impetus for fat in each joint was established from the allometric equation (Y = aXb). Differential growth of fat in different joints resulted in marked differences in percentage of fat in various joints as fattening progressed. Growth coefficients,b, for fat in each joint were homogeneous among breed groups, indicating similar fat development patterns over the weight range studied. Growth impetus for fat was lowest in the distal limbs and in the proximal hind limb. Fat growth in the proximal fore limb was proportional to total fat. Along the dorsal line, low impetus was found in neck and rump regions, increasing to a high impetus in the mid-back region. Ventrally the fat of the flank showed the highest growth impetus of all regions with fat in the brisket and flat ribs also showing an increasing proportion with increases in total fat.Small but significant differences among sire breeds were found for the amount of fat in each joint at a standard amount of total fat in the carcass. Differences found among sire breeds in fat distribution were not associated with differences in maturity type.

The effects of liveweight, breed, sex, diet and feeding level on muscle distribution were studied by comparing nine anatomical muscle groups dissected from the half carcasses of pigs from two studies. The first study consisted of 109 pigs representing barrows and gilts of three breed groups, fed two diets differing in energy and protein. The second study consisted of 72 barrows and gilts from two breed groups fed a low-energy diet at one of three feed levels. Animals were slaughtered at 23, 68, 91 or 114 kg liveweight. The results were compared with data from one other study. In pigs, major differentiation in muscle development appears to take place prior to 23 kg liveweight. Muscle differentiation appeared to follow functional demands. Muscles associated with mobility immediately after birth such as the distal limb muscles, developed early while those associated with greater locomotion and propulsion, such as the proximal pelvic limb muscles, developed later in life. Sex had little influence on muscle distribution between 23 and 114 kg liveweight. Proportion of abdominal muscles had apparently increased markedly prior to 23 kg liveweight and continued to be influenced by the level of feeding throughout. Breed differences in muscle distribution were observed for spinal, abdominal and distal thoracic limb muscles. Key words: Swine, muscle growth, muscle distribution

Pregnancy rates and calving dates of beef cows in four multiple-sire breeding herds in 1980 and 1981 were used to evaluate bull fertility. The bulls were from Hereford, Beef Synthetic and Dairy Synthetic breed groups, and were measured for scrotal circumference, scored for libido and evaluated for semen characteristics 1 wk before the commencement of breeding. Three yearling bulls were assigned to approximately 70 cows in each of the four herds (a total of 12 bulls) during a 60-d breeding season. The progeny of each sire were identified by blood typing. There was one bull in each breeding herd which sired at least 50% of the calves. The average age was higher in bulls with the maximum fertility (P

To elucidate the influence of high body weight selection on tissue growth patterns, adipose tissue growth and lipid accumulation were investigated in both a line of mice selected for high 42-day body weight (High line; HL-3) and an unselected (Foundation; FP-3) population. All comparisons between the two lines were performed on a within-sex basis. Logistic growth curve analysis revealed that HL-3 mice exhibited an accelerated growth rate, and reached a higher mature body weight, than FP-3 mice. Employing the allometric equation, Y = aXb, this investigation further revealed that, relative to both body weight and nonadipose tissue weight, adipose tissue and extractable lipid increased slower in HL-3 mice than in FP-3 mice. Only at fixed body and nonadipose tissue weights, which exceeded the maximum weights achieved by the FP-3, did HL-3 adipose tissue and lipid weights exceed those of FP-3 mice. HL-3 mice have previously been demonstrated to exhibit an increased appetite. Therefore, the existing model of selection-mediated compositional changes should be expanded to allow the coupling of an increased appetite with an enhanced relative rate of nonfat tissue growth. Key words: Growth-selected mice, adipose tissue growth, lipid accumulation

A trial is reported comparing the accumulation of lipid in rib cuts from 12 bull and 12 heifer carcasses from two breed types: Hereford (HE) and Dairy Synthetic (DY). Serial slaughter was carried out from weaning (163 ± 15.1 (SD) days) to approximately 16 mo of age. The left side of each carcass was broken in two quarters, and then eight wholesale cuts. Fat samples (subcutaneous, intermuscular, body cavity) and a muscle sample were taken from the rib cut and analyzed for their lipid and energy contents. The rate of accumulation of lipid was estimated from the growth coefficient, b, in the allometric equation (Y = aXb) using total separable fat as the independent variable. Growth coefficients were homogeneous both between breeds and sexes indicating that neither sex nor breed influenced the relative accumulation of lipid. A significant sex difference (P < 0.01) was found when the lipid content of the fat depots and the rib muscle were adjusted to a constant side separable fat. No breed differences (P > 0.05) were found in the lipid content of the fat depots. A significant difference between sexes was also found in the energy content of the fat depots, but no differences were found between breeds, when the data were adjusted to the mean of the total side fat.

A milking experiment with range, single-suckled beef cows was conducted over two lactations in 1976 and 1977 at the University of Alberta Research Ranch. A total of 428 cows were milked, ranging from 2 to 10 yr of age and representing four breed groups of Herefords and crossbreds of traditional beef and dairy breeds. Measurements of milk were taken in June and September each year. Milk was extracted following an intrajugular injection of 20 IU of oxytocin. Samples were analyzed for butterfat percent, protein percent and lactose percent. Age and breed of dam differences in milk yields, constituent percentages and yields were assessed. Least squares means of yields pooled over the two periods each year indicated that dams with Holstein and Brown Swiss breeding (DS) yielded more milk than beef crossbreds and purebred Herefords. Average milk yields estimated over 24 h ranged from 5.7 kg/day for Herefords to 7.8 kg/day for DS dams. Compared to 2-yr olds at 100%, 3-yr olds produced 125%, 4-yr olds 136% and mature cows 139% greater yield. The difference between June and September yields was evident between breed groups. Hereford milk production exhibited the greatest decline over 87 days compared to all other crossbreds and DS were the most persistent. Mature cows maintained milk yields better than younger cows, and 2-yr old milk yields declined most noticeably. All crossbred groups produced less butterfat percent and lactose percent content than the Herefords, yet yielded more total energy. All constituent percentages were higher than those reported for commercial dairy cattle. All constituent percentages increased significantly from June to September at approximately 130 days in lactation. A significant decline was noted for all constituent yields in September. Dairy crossbreds demonstrated the highest persistency for all constituent yields. Beef Synthetic dams were intermediate in yield persistency. Average milk yields had negative (P

Data on 135 young bulls from a two-breed group diallel experiment involving double-muscled (DM) and normal (N) cattle were analyzed to obtain estimates of heterosis, maternal and direct effects for carcass traits. When carcass traits were adjusted to a constant age at slaughter (398.5 d), significant positive heterosis was observed for slaughter and carcass weights, carcass length and s.c. fat thickness. Maternal effect was relatively unimportant for the traits studied. The progeny of N sires and DM straightbreds were heavier at slaughter and had higher carcass weight, s.c. fat thickness and carcass length (P less than .01), whereas DM-sired progeny and DM straightbreds had higher dressing percentage (P less than .05) and cutability (P less than .01). Heterosis was significant for all the 10-11-12th rib joint dissection traits except for percentage of muscle. Although there was negative heterosis for percentage of bone, there was positive heterosis for rib joint weight, fat weight and percentage, muscle weight and muscle:fat and muscle:bone ratios. For direct effect and straightbred differences, N-sired progeny and N straightbreds, respectively, had significantly larger values for rib joint weight, fat weight and percentage and bone weight. The DM-sired progeny and DM straightbreds had larger values for percentage of muscle, muscle:fat and muscle:bone ratios. When the carcass and dissection traits were adjusted to a constant carcass (303.7 kg) and rib joint (4,812 g) weight, respectively, the results were similar to those observed on age constant basis except for rib eye area, for which DM-sired progeny and DM straightbreds had larger values.

Carcass composition and growth patterns for muscle and bone were compared among three breed-types (Hereford crossbred, (HC), beef synthetic (SY) and dairy crossbred (DC)). Sixteen bulls of each breed-type were weaned at about 6 mo and fed a high concentrate ration ad libitum. The bulls were grouped four to a pen and randomly allocated to one of two slaughter weights (500 kg and 600 kg). Breed-types differed (SY vs. HC and DC) in the allometric growth coefficients of hot carcass weight regressed on liveweight indicating that the growth of the hot carcass relative to liveweight in SY bulls was higher than the interbreed average. No significant breed-type differences were found in the regression of sample muscle and bone on various size dimensions. Breed-types differed significantly in amount of bone adjusted to common sample muscle, carcass and liveweight. Since breed-type allometric regressions were in all cases homogeneous, the difference in composition reflected differences already apparent at the first slaughter point (500 kg).

A trial is reported comparing half-carcass fat partitioning in 12 bulls and 12 heifers each of two breed-types: Hereford (HE) and Dairy Synthetic (DY). These animals were serially slaughtered from weaning (163 ± 15.1 (SE) days) to approximately 16 mo of age. After slaughter, one side of each carcass was broken into eight wholesale cuts, which were separated into fat (subcutaneous fat (SF), intermuscular fat (IF) and body cavity fat (BCF)), muscle and bone. The partition of fat was investigated by examining the development of each depot relative to two independent variates (fat percent and fat weight in the side), using the allometric equation. Relative to fat percent in the side, the regression coefficients for depot fat accumulation were all homogeneous for sex, and only one coefficient (SF in the forequarter) was significantly different (P

The eating quality, cooking losses and chemical composition of semitendinosus (ST) and longissimus dorsi (LD) roasts from 48 young steers weighing 475–513 kg and representing Canada Grade A1 to A4, B1 and an unofficial grade of A1X (dairy-type) beef carcasses were determined. There was a tendency for Grade A4 and A1X ST and LD samples to be higher in percent fat (ether extract) than comparable samples from the other grades. In spite of fat differences in the muscles among grades, subjective evaluation of the eating quality of the roasts by a trained panel indicated that ST and LD roasts from all of the grades were acceptable and quite similar. However, judges did note the presence of larger amounts of fat in those beef samples which contained greater amounts of chemically determined fat (A4, A1X). Consumer panel judgements of ST roasts were similar to those of the trained judges. Objective measurements of juiciness (water-holding capacity) and tenderness (Warner Bratzler shear. Kramer shear) for ST and LD roasts supported the findings from sensory evaluation. Cooking losses for ST and LD roasts did not appear to be affected by grade. These studies provide evidence that the cooking and eating quality characteristics of beef from the various categories of the A grade, from the B1 grade and from the unofficial A1X (dairy-type) grade were similar and that all the beef was acceptable.

Seventy-five young, full-fed, Shorthorn-sired cattle (36 heifers, 24 steers, 15 bulls) were slaughtered over a wide liveweight range (150–550 kg) to evaluate the influence of sex on the patterns of fat deposition. Growth coefficients for depot fat relative to half-carcass fat were homogeneous, and there were no differences (P > 0.05) among the adjusted means of depot fat at constant total fat. This indicates that depot fat partitioning among sexes is probably minor, provided comparisons are made at equal fatness. Total rate of fat deposition relative to muscle was similar for heifers and steers, but significantly (P

Calving records of 174 2-yr-old heifers from four breed groups; Hereford (HE), Beef Synthetic (SY), Dairy Synthetic (SD) and Crossbred Hereford (HX) were used in this study. Half of the heifers were exposed to three epididymectomized bulls for 6 wk before the start of the breeding season. While exposure to bulls had little influence (P = 0.51) on pregnancy rate, it advanced the calving date by 5.5 days compared with the control group (P

Two breeds (Hereford (HE), and Dairy Synthetic (DY)), and two sexes (bulls and heifers) were compared for various measures of efficiency in beef production. DY animals had greater (P

Eighteen Double Muscled (DM), 18 Beef Synthetic (SY) and 18 Hereford (HE) bulls were serially slaughtered from approximately 250 to 800 kg liveweight to determine the influence of maturity type and "double muscling" on fat growth, partitioning and distribution. The fatty tissue was dissected into subcutaneous fat (SCF), intermuscular fat (IMF) and carcass cavity fat (CCF); the sum of these depots was used as total side fat (TSF). Relative to TSF, DM did not differ significantly from the other maturity types in growth rates of SCF, IMF and CCF, but relative to fat percent in the side, DM tended to have much lower growth rates for SCF and CCF. The common growth coefficients indicated that as TSF increased the proportion of SCF increased (b > 1; P 0.05). At equal TSF, as expected, HE tended to partition more of their fat to the subcutaneous depot, whereas DM and SY tended to partition more of their fat to the intermuscular and carcass cavity fat depots. Relative to HE, DM followed late-developing fat partitioning patterns. The hypodevelopment of fat depots in the carcasses of the muscular hypertrophied animals followed an inner-outer gradient which was most pronounced in the subcutaneous fat depot. Key words: Cattle, fat growth, double muscling, breed type

The growth and distribution of bone from 179 pig carcasses were compared among five breeds (Duroc × Yorkshire (D × Y), Hampshire × Yorkshire (H × Y), Yorkshire (Y × Y), Yorkshire × Lacombe-Yorkshire (Y × L-Y) and Lacombe × Yorkshire (L × Y)) and two sex-types (barrows and gilts) over a wide range in carcass weight. The growth pattern for each bone relative to total side bone was estimated from the growth coefficient, b, in the allometric equation (Y = aXb). Growth coefficients were homogeneous in this study among breeds and between sexes for each bone, indicating that the different breeds and sexes followed similar patterns of relative bone growth as they increased in size. The lowest growth coefficients (b

Nineteen mature Double Muscled (DM) cattle consisting of 11 cows and eight bulls were slaughtered between 470 and 710 kg to determine the influence of sex on carcass composition and muscle, bone and fat in DM cattle. Expressed as a percentage of the total side weight, DM bull carcasses had 15% more muscle and 55% less total fat. When sides were compared DM bulls showed a 17% increase in the muscle:bone ratio compared with DM cows. In bull carcasses, there were shifts in muscle weight distribution towards the forequarter. The ratio of hindquarter muscle:forequarter muscle was greater in cows than in bulls. Expressed as a percentage of the total side muscle, significant differences between sexes were found in 48 of the 95 muscles. The most striking sexual dimorphism was found in the neck region, particularly among the muscles responsible for secondary sexual features and those which act to elevate and extend the head. Sexual dimorphism was less pronounced in the distal parts of the both limbs. The cervical vertebrae and scapula made up a greater proportion of total side bone in DM bulls than in DM cows. There was a consistent but nonsignificant trend for the cows to have more of their bone caudally and less anteriorly compared with the bulls. Key words: Carcass composition, muscle distribution, bone distribution, mature Double Muscled cattle, double muscling

Bull fertility, measured as pregnancy rate, percentages of calves born during the first 4 and 6 weeks of calving and means and medians of calving date distributions, was studied in 62 single-sire breeding herds of three breed groups over a 10-year period. Each bull was used as a yearling and then again as a 2-year-old. Average bull-to-cow ratio was approximately 1:20, and the breeding season started on 1 July and extended for approximately 60 days. The average pregnancy rate of cows mated to yearling bulls was similar to that for 2-year-old bulls (83.9% vs. 82.5%, respectively). There was a tendency towards earlier breeding among 2-year-old compared to yearling bulls as shown by 6.8% more ( P = 0.09) calves born during the first 4 weeks of calving and 2.5 days advancement ( P = 0.10) in the median of calving date distribution. Year and breed group of bull had no significant effect on the measures of bull fertility. The repeatability estimates of the measures of bull fertility were low, indicating that the reproductive performance of a 2-year-old bull cannot be accurately predicted from his performance as a yearling.

Data from a two-breed group diallel experiment involving double-muscled (DM) and normal (N) cattle were analyzed to evaluate the importance of heterosis, maternal and direct effects for reproduction and growth traits. The DM cattle were from a composite of primarily Angus, Charolais, Galloway and Hereford breeds, and N cattle were crossbred cattle with at least 50% Hereford breeding. The data comprised a total of 491 matings and 389 calvings in four breeding seasons. Records on calving performance, calving date, calf crop born and weaned, sex ratio of progeny and weight of calves were analyzed using least squares procedures. Significant heterosis of 5 to 12% was observed for all the calf crop and growth traits, except for birth weight. Heterosis resulted in 24% reduction in the incidence of dystocia and perinatal calf mortality (P less than .05). The significant heterosis was due mainly to poor production in DM X DM crosses. The DM cows were superior (P less than .05) to N cows in reciprocal crossing (maternal effect) for all the calf crop traits, but had higher incidence of calving difficulty and a higher proportion of male progeny. Significant direct effect was observed for all the traits except calving date and sex ratio among progeny. The N sires were superior for all the calf crop traits and caused less incidence of dystocia and perinatal mortality compared with the DM sires. Significant differences were obtained between the straightbreds for all the traits except calving date. The N straightbreds were superior to the DM straightbreds for all the significant traits.

Cooking losses and eating quality were determined for semitendinosus (ST) and longissimus dorsi (LD) roasts obtained from bulls and steers fed three levels of dietary roughage (20, 50 and 80% alfalfa–brome hay) and from animals slaughtered at approximately 450 or 580 kg liveweight. Cooking losses of either type of roast did not appear to be affected by level of dietary roughage, but were affected by castration. For either weight group, trained panelists generally determined no significant effects of roughage level on eating quality of either type of roast. However, consumer panelists noted significant differences in the flavor, tenderness, and overall acceptability but not juiciness in ST roasts with those from the animals fed 20% roughage superior to those from the 80% group. Objective measurements of juiciness (water holding capacity (WHC)) and tenderness generally supported the data of the trained panel. Only one objective test for each type of roast, rated roasts from animals fed 80% roughage to be significantly less tender than roasts from animals fed lower roughage levels. All other objective tests detected no differences in tenderness attributable to roughage level. Cooking losses were generally greater for roasts from bulls than from steers. Fat percentage was lower and moisture higher for roasts from bulls than those from steers. A detectable difference in pH, with bull samples higher than steer samples, was found for ST roasts from the heavy weight group, and for LD roasts from both slaughter weight groups. Trained panelists detected few differences in palatability characteristics between ST roasts from bulls vs steers; more differences were detected between bull and steer LD roasts, and the differences were greater for the heavy slaughter weight group. Consumer panelists rated steer ST roasts superior to those from bulls for flavor, tenderness and overall acceptability, but the rating of roasts from bulls was acceptable. Water holding capacity was similar for bull and steer roasts in this study. Objective tests for tenderness did not detect differences between bull and steer ST roasts but did show highly significant differences between bulls and steers for LD roasts. Objective color difference between sexes was found only for ST roasts from the heavy slaughter group. Thus these studies indicate that beef from animals fed roughage levels from 20 to 80% of the diet was similar and acceptable. Differences in eating quality of beef from bulls and steers were detected but generally these differences were small and beef from bulls was judged acceptable.

Sex of calf and age of dam effects on birth weight, preweaning ADG, 180-day weaning weight; and age of dam effects on yearling weight, postweaning ADG in males, and 18-mo weight in females were studied in a Hereford and a beef Synthetic population. The effects of breed, sex of calf, age of dam and year were significant on preweaning traits. The superior milking ability of Synthetic cows over Herefords was more pronounced for male than female calves. Additive and multiplicative adjustment factors were calculated from the least squares analyses. Additive adjustments for age of dam and multiplicative adjustments for sex of calf were found most suitable for preweaning traits. Three methods of application of adjustment factors were studied. Multiplicative sex of calf adjustment followed by additive age of dam adjustment was found to be most effective as indicated by the reductions in mean squares for main effects and interactions. Additive and multiplicative age of dam factors are presented for yearling weight in males and 18-mo weight in females. Use of additive factors is recommended. Extending weaning weight age of dam adjustments for postweaning traits was not found suitable in this study. Key words: Beef cattle, age and sex, adjustment factors