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The influence of cytoplasmic effects on weaning weight (WW) and age at first calving (AFC) were investigated in the South African Afrikaner beef breed. A total of 14 535 AFC records (1974 - 2008) and 68 152 WW records (1974 - 2011) were used in the estimation of variance components. Ail cows were assigned to different damlines, using the pedigree information available. The model used for WW include direct additive, maternal additive, the covariance between the animal-, permanent maternal environmental-, herd-year-season x sire- and damline effects, while the simplest model which include only direct- and damline effects were used for AFC. The contribution of the cytoplasmic effects to the total variance was negligible (less than 0.5%) for both traits. These results suggest that cytoplasmic effects can be ignored in genetic evaluations of Afrikaner cattle for the traits investigated. [ABSTRACT FROM AUTHOR]

The purpose of the study was to investigate a possible genotype by environment interaction in first calf South African Holstein cows for both production and reproduction traits. Data from 100 975 cows on a total mixed ration (TMR) and 22 083 pasture based cows were used. These cows were the progeny of 4 391 sires and 84 935 dams produced over a period of 11 generations. Traits analysed were milk production (corrected to a 305-day equivalent) and age at first calving (AFC). Both were recorded over a period of 30 years from 1980 - 2010. Production or AFC in each environment (TMR vs. pasture) was treated as a separate trait. Bivariate analyses, fitting an animal model using the ASREML software, were used to obtain genetic correlations between the traits measured in each environment. The fixed factors included were a concatenation of breeder-keeper-year for both milk production and AFC and age at first calving which was fitted as a linear regression for milk production. The random part consisted of the direct additive effects only. The genetic correlation for milk production measured in the two different environments was 0.90 (0.027) and that of age at first calving 0.28 (0.12). The heritability estimates for milk production were 0.23 (0.008) under the TMR system and 0.32 (0.015) for the pasture based system, while the estimates for AFC were 0.063 (0.005) and 0.055 (0.009), respectively. The rather large-scale effect in the heritability (0.23 → 0.32), as well as the correlation of less than one for milk production between the two environments, indicates that a G x E may exist. However, the low genetic correlation between the two environments for AFC is much more real and indicates that G x E should be taken into account when sire selection is performed. [ABSTRACT FROM AUTHOR]

Pedigree records, maintained from 1978 to 2005 at the Oudtshoorn Research Farm, South Africa, of 40 074 birds of a pair-breeding ostrich flock were used to estimate the effective number of founders (fe ), the effective number of ancestors (fa), the effective population size and the effective genome equivalents (fg) under random mating, to assess the genetic variability present in the population. The average level of completeness of the pedigrees was high (99.3%) in the first generation, and the average level of inbreeding (F), calculated from the pedigrees, was 0.51%. The reference population was defined as the 39 784 birds hatched from 1990 to 2005. The estimated measures of variability were fg = 47.3, fe = 59 and fa = 58, with an fe/fa ratio of 1.02. The numbers of ancestors responsible for 100%, 50% and 20% of the genes in the reference population were 254, 21 and 6, respectively. The largest individual contribution to the population hatched from 1990 to 2005 was from a male that was responsible for 4.85% of the genetic variability. The generation interval for the four selection pathways - calculated as the average age of parents when offspring that were kept for reproduction were born - were sire to son (7.74 ± 4.92), sire to daughter (7.77 ± 5.13), dam to son (7.50 ± 4.29) and dam to daughter (7.90 ± 4.92). The average generation interval of the reference population was 7.72 ± 4.79 years. The linear regressions of mean annual individual rate of inbreeding on year of birth for the two distinct periods 1995-2002 and 2003-2005 were 0.08% and -0.07% per year, respectively. The estimate of effective population size (N e ), computed via the increase in the individual rate of inbreeding, was 112.7. Estimates of N e using the alternative methods of tracing the numbers of generations were 73.6, 177.4 and 95.3 for complete, maximum and equivalent complete generations. The results of this study indicated that the population under study was at an acceptable level of genetic variability. [ABSTRACT FROM AUTHOR]

The genetic relationship between conformation traits and functional herd life of the South African Jersey population was investigated. Data on conformation traits (n = 46 238) and functional herd life (n = 90 530) on registered South African Jersey cows calving between 1989 and 2008 were obtained from the Integrated Registration and Genetic Information System. Conformation traits were scored using a subjective inear scoring system ranging from 1 to 9, except for foot angle, with a maximum score of 8. Conformation raits included stature, chest width, body depth, dairy strength, rump angle, thurl width, rear leg side view, oot angle, fore udder attachment, rear udder height, rear udder width, udder support, udder depth, front teat placement, rear teat placement and front teat length. Genetic correlations between conformation traits and unctional herd life were estimated by a series of bivariate analyses. Significant moderate to strong positive genetic correlations between most udder traits and functional herd life (0.23 to 0.63) were estimated. The most important udder traits related to functional herd life were fore udder attachment, rear udder height and udder depth. Most of the body structure traits had a low to moderate negative correlation with functional herd life (-0.04 to -0.27). However, rump angle and foot angle were estimated to have a moderate positive genetic correlation with functional herd life. The genetic relationships between functional herd life and conformation traits in the South African Jersey breed indicate that conformation traits could be used to enhance the accuracy of genetic evaluation for functional herd life. It is therefore recommended that current national genetic evaluation for functional herd life in the South African Jersey breed should include conformation traits. [ABSTRACT FROM AUTHOR]

The length of productive life is of major economic importance in dairy cattle production. Simple breeding objectives such as selection for increased production in dairy cattle have led to a significant decline in fitness traits. The objective of the current study was to investigate whether direct selection for production resulted in an undesirable genetic response in longevity in the South African Jersey breed. Longevity was defined as survival in the first three lactations from first calving to culling or death, adjusted for the effect of milk yield. An observation for survival per lactation was denoted by 1 (survived) or 0 (culled) otherwise. Performance and pedigree records on purebred South African Jersey cows that participated in the National Milk Recording and Improvement Scheme were considered. A multiple-trait linear animal model was used to estimate breeding values. A complete (co)variance structure for the additive genetic and residual effects for the three traits were used. Heritabilities used in the current study were 0.034, 0.022 and 0.026 for the 1st, 2nd and 3rd lactations, respectively. Reliabilities were approximated using the effective number of daughters. The estimated breeding values for sires ranged from 79 to 114. The rate of genetic progress per year for the period 1985 to 2002 was statistically non-significant (b = 0.02 ± 0.05 per year). Results from the current study indicate that direct selection for production did not result in an undesirable correlated genetic response in longevity. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effect of inbreeding depression on functional herd life in the South African Jersey population based on individual level and rate of inbreeding. A pedigree file of the South African Jersey breed (n = 912 638) was obtained from the Integrated Registration and Genetic Information System (INTERGIS). The data included registered, grade and imported animals. The percentages of animals in the pedigree file with two, one and zero parents unknown were 22%, 18% and 60%, respectively. The inbreeding coefficient for each animal (Fi) and the rate of individual inbreeding (ΔFi) as an alternative measure of inbreeding that is adjusted for the depth of known pedigree were calculated. The effect of inbreeding on functional herd life in each of the first three lactations was estimated, using a single- trait sire model on data collected from 1985 to 2003. Three analyses for survival in each of the first three lactations were conducted. In the first analysis, in addition to fixed and random effects, an individual inbreeding coefficient (Fi) was fitted as a linear covariate. In the second analysis, the inbreeding coefficient was included as a discrete variable with the following classes of inbreeding: 0 < F ≤ 3.125, 3.125 < F ≤ 6.25, 6.25 < F ≤ 12.5 and F > 12.5. In the third analysis, the individual rate of inbreeding (ΔFi) was included in the model as a linear covariate. The level of inbreeding in the SA Jersey population showed a gradual increase for the period 1985 to 1994, while the period 1995 to 2003 showed a rapid increase. The current mean level of inbreeding (for the year 2010) is 4.85% with a minimum and maximum of 0 and 31.34%, respectively. The rate of inbreeding showed a gradual increase from 0.36% to 0.43% between 1985 and 2003. The average rate of inbreeding is currently (for the year 2010) at 0.55%. There was a significant unfavourable relationship between inbreeding and functional herd life in the first and second lactations. The effect of inbreeding was more pronounced in the second lactation for both measures of inbreeding. Based on the current level of inbreeding, the reduction in functional herd life in the first lactation can be estimated as 0.68%. The corresponding estimate for the second lactation is 1.70%. The results from the current study indicate that the current level or rate of inbreeding has reached levels that are detrimental to functional herd life. Therefore, individual inbreeding coefficients should be considered in addition to genetic merit when breeding decisions are made by Jersey breeders. [ABSTRACT FROM AUTHOR]

Data involving monthly records of egg production (EP), chick production (CP), hatchability (H), mean egg weight (MEW) and mean day-old chick weight (MCW) were analysed using REML procedures. All traits were treated as hen traits. Egg production of young birds increased to reach a peak of approximately 4 to 5 eggs per month relatively late in the breeding season (September to December). Older hens reached a higher peak of 6 to 9 eggs per month earlier in the breeding season (August to September). There was a secondary peak in older birds from November to December. All birds except 2-year olds exhibited evidence of a slump of production during October. Chick production, MEW, MCW and H followed similar trends. The random effects of direct additive genetic, permanent environment (PE), temporary environment (TE -- unique hen-year combinations) and service sire (SS) were estimated from the data. Heritability estimates of the direct additive genetic effect (h²a) of the hen were 0.04 for EP, 0.05 for CP, 0.44 for MEW, 0.67 for MCW and 0.02 for H. The estimates of permanent environment (C²pe) as a ratio of phenotypic variance for the four traits (MCW did not exhibit a significant C²pe effect) were 0.08, 0.08, 0.09 and 0.1 i, respectively. The effect of service sire as a ratio (C²ss) was significant but relatively low for all traits, ranging from 0.04 for MEW and MCW to 0.06 for CP. Monthly EP and CP were highly correlated at all levels, ranging from 0.74 for the TE correlation to unity (1.00) for the genetic correlation. Egg production was favourably correlated with H at a genetic level (0.98). The genetic correlations of EP and CP with MEW and MCW were variable and in some cases antagonistic as is often found in poultry. The genetic correlations of H with MEW and MCW were positive (0.52 and 0.47, respectively). As expected, the genetic correlation of MEW and MCW was very high at 0.94. The results indicate that selection for improved reproduction (reproductive output and product quality traits) in ostriches is possible. Selection is unlikely to be complicated by unfavourable correlations with H, MEW and MCW. [ABSTRACT FROM AUTHOR]

Records of the Tygerhoek Merino resource flock were used to estimate genetic, phenotypic and environmental parameters between subjective wool and conformation traits with objective wool and live weight traits. The database contained records of 4 495 animals, the progeny of 449 sires and 1 831 dams, and born from 1989 to 2004. On the genetic level (rg) live weight was favourably related to regularity of crimp (ROC) (0.20), woolly face score (WFS) (0.21), general head conformation (GEN) (0.67), conformation of the hind legs (HOCKS) (0.36), conformation of the front legs (FQ) (0.42), topline (TOPL) (0.25) and total fold score (TOT). Estimates of rg were favourable for clean yield with wool quality (QUAL) (0.30), wool colour (COL) (0.45), wool oil (OIL) (-0.44), staple formation (STAPL), belly and points (BANDP) (0.24), face cover score (FCS) (0.18), GEN (0.25), HOCKS (0.19), TOT (-0.26) and FQ (0.18). Clean fleece weight (CFW) was favourable correlated 'to QUAL (0.18), STAPL (0.39), BANDP (0.48) and GEN (0.23). Staple length was favourably related to COL (0.16), BANDP (0.40) and WFS (0.16) and negatively related to OIL (-0.33). Staple strength was favourable correlated to ROC (0.33) and FQ (0.39). Fibre diameter was favourable correlated with QUAL (-0.32), ROC (-0.28), FCS (-0.32), pastern score (PS) (-0.16) and TOPL (-0.18). Coefficient of variation of fibre diameter (CVFD) was favourably correlated with QUAL (-0.50), ROC (-0.73), HOCKS (-0.17), FQ (-0.33) and TOPL (-0.25). In contrast, unfavourable correlations occurred for SS with TOT (0.25), for FD with STAPL (0.59), BANDP (0.37), HOCKS (0.13) and TOT (0.13). Other unfavourable genetic correlations were between CFW and TOT (0.28) and between CVFD and STAPL (0.49). The results showed that selection for LW and objective wool traits will not seriously compromise subjective wool and conformation traits, barring a few exceptions. [ABSTRACT FROM AUTHOR]

Records of the Tygerhoek Merino resource flock were used to estimate genetic, phenotypic and environmental parameters for subjectively assessed wool and conformation traits. The database consisted of records of 4 495 animals, the progeny of 449 sires and 1 831 dams born in the period 1989 to 2004. The pedigree records have been collected between 1969 and 2004. Direct heritability estimates (h²a) for subjective wool traits ranged from 0.15 for face cover score to 0.50 for woolly face score. Corresponding h²a for subjective conformation traits ranged from 0.13 for topline (TOPL) to 0.39 for total fold score (TOT). Maternal heritability estimates were all below 10% where applicable. The proportion of the total phenotypic variance due to the maternal permanent environment variance (c²pe) amounted to 5% for general head conformation (GEN). The genetic correlation between animal effects ranged from -0.70 to 0.21 where applicable. Among the subjective wool traits favourable genetic correlations (rg) were estimated between regularity of crimp (ROC) and wool colour (COL) (0.31), for wool quality (QUAL) with ROC (0.49) and COL (0.26) and between staple formation (STAPL) and belly and points (BANDP) (0.58). The relationships between ROC and STAPL (-0.49) and for QUAL with STAPL (-0.45) and BANDP (-0.20) were unfavourable. The noteworthy relationships among subjective conformation traits were those between the conformation of the hind legs and the conformation of the front legs (0.71) and of GEN and TOPL with TOT (-0.31 and -0.47 respectively). The rg of significance between subjective wool and conformation traits were variable in sign and magnitude. These results indicated the possibility to achieve sustained genetic improvement by selection for subjective wool and conformation traits in South African Merino sheep. [ABSTRACT FROM AUTHOR]

A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976, lines were sub-divided into 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data recorded over approximately six generations of selection (40 years) was analyzed. The direct heritability estimates were moderate for birth weight (0.4), but low (0.1 to 0.2) for the other traits, similarly maternal heritabilities were low (0.1 to 0.2). Permanent environmental effects due to dam were moderate (0.3) for weights at 205 days, weaning and at 12 months, and was still an important effect at 18 months. Relatively large negative (-0.4) direct-maternal genetic correlations were indicated for weaning and yearling weights. There were indications that all post-weaning weight traits evaluated were closely related giving rise to their joint inclusion in joint multivariate analysis. There were no indications of line x environment interactions, however, interaction of sire x year was important for all the traits highlighting the tremendous year to year variations experienced in the sub-tropics. There is a need to evaluate selection for genotypic stability, particularly for the more extensive farming environments. [ABSTRACT FROM AUTHOR]

A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976, after approximately two generations of selection, lines were sub-divided into 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data recorded over approximately six generations of selection (40 years) were analyzed. The average age of sires and dams at the time of birth of their progeny was 5.9 and 7.5 years respectively in the pre-crossover phase and was reduced to 4.4 and 6.5 years respectively in the post-crossover phase. The rate of inbreeding across lines and environments was 1.2%/generation. The cumulative selection differential trends for both the S and NS lines for adjusted weaning weight plotted against generation number were very low, relatively linear and greater for the S line (0.10 s.d./year) compared with the NS line (0.08 s.d./year). Direct and correlated responses were uniformly low, approximating 1% of the trait mean per generation, and indicating that considerable attention was given to secondary characters. These results concur with general findings of effective direct and correlated responses of weight traits to individual selection. [ABSTRACT FROM AUTHOR]

A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at the Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976, after approximately two generations of selection, lines were sub-divided into 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data recorded over six generations of selection (40 years) were analyzed. The average incidence of calving success (the presence or absence of a calf) was 68%. Heritability and repeatability (in parenthesis) estimates for calving success and calving date were 0.08 ± 0.02 (0.10 ± 0.02) and 0.09 ± 0.02 (0.17 ± 0.02), respectively. Favourable genetic trends were shown (-0.8 ± 0.09 days/generation for calving date). Correlation estimates of sires' EBV between measures of fertility and growth were all unfavourable. A significant interaction was manifested for calving success and was due to the markedly poorer performance (10 percentage units) of the S line cows in the NS environment. The interaction serves to reinforce the commonly held principle that cattle, and in particular breeding cows, be reared in a similar environment in which selection takes place advocating antagonistic selection (upwards selection in a poor environment). Calf losses within the first 24 h of birth and pre-weaning were 3.8% and 8%, with heritability estimates of 0.15 ± 0.07 and 0.07 ± 0.03, respectively. It is recommended that fertility and calf survival be included in routine breed evaluations. There is a need to implement data collection strategies to ensure that all calving activities are comprehensively recorded. [ABSTRACT FROM AUTHOR]

A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976 lines were sub-divided into four lines with 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data collected over a 40-year period (1958 to 1997) were analyzed. There were no line differences, however, productivity in the S environment was superior compared with the NS environment. While there were no environment differences in birth weight, calves born early in the S environment were estimated to be 90 kg (33%) heavier at 18 months than calves born late in the NS environment. The performance of calf growth from birth to 18 months in this study has emphasized the importance of matching animal physiological status with seasonal changes in the sub-tropics. The effect of previous lactation status (PLS) increased from 1.2 ± 0.13 kg at birth to 7 ± 0.6 kg at 205 days of age, a difference that persisted to 18 months (5 ± 0.9 kg). Given the significant and consistent detrimental effects of PLS on calf growth, it is recommended that this effect be considered in routine evaluations. [ABSTRACT FROM AUTHOR]

Longevity reflects the ability of a cow to avoid being culled for low production, low fertility or illness. Longevity can be used in breeding programmes if genetic parameters are known. Various measures are used for longevity. In this study survival in each of the first three lactations was analysed. Survival was denoted by a 1 if a cow survived, and 0 otherwise. The primary objective of the current study was to estimate genetic parameters for functional herd life. The secondary objective was to compare estimates of genetic parameters from the linear sire and animal models. Data and pedigree records on purebred Jersey cows that participated in National Milk Recording and Improvement Scheme of South Africa were used to estimate genetic parameters. A total of 181 269 cow records from 636 herds recorded over 16 years were available for analysis. Estimates of genetic parameters for herd life were obtained using REML procedures fitting three-trait (first three lactations as separate traits) linear animal and sire models. Heritability estimates (0.02 to 0.03) from the animal and sire models were somewhat similar for all lactations. However, heritability estimates for lactations 2 and 3 were slightly higher with the sire model compared to the animal model. The genetic correlation between lactations 1 and 2 from both the sire and animal models was higher than that between lactations 2 and 3. Genetic correlations from the sire model ranged from 0.68 to 0.99, compared to 0.76 to 0.99 from the animal model. Results from the current study suggest that genetic variation exists for functional herd life to allow for genetic improvement through selection. The moderate positive genetic correlation between survival in the first and third lactation suggest that early selection for functional herd life is feasible. [ABSTRACT FROM AUTHOR]

Accurate genetic parameter estimates are needed upon which to perform multiple-trait across flock breed analyses. Genetic parameters for yearling body weight (BW), clean fleece weight (CFW) and mean fibre diameter (MFD) were estimated using records of 107 389 individuals (the progeny of 1 530 sires and 45 178 dams) collected between 1992 and 2004 in the South African Dohne Merino population. Fixed effects included in the model were flock-year-season-sex-management group (1 594 classes), type of birth (singles, multiples), age of dam (2 - 7+ years) and age at measurement, fitted as a linear covariate (385 ± 12 days). Six different single-trait animal models were fitted, where different combinations of the following random effects were fitted: direct additive, the sire-flock interaction, the sire-flock-year-season interaction (SFYS), the dam genetic effect, the direct-maternal correlation and the dam permanent environmental effect. These analyses were followed by a three-trait analysis structured according to the log likelihood ratios obtained for the single-trait analysis. This analysis allowed the calculation of relevant correlations among traits together with their respective standard errors. Direct heritability estimates from the three-trait analysis were 0.17 for BW, 0.19 for CFW and 0.45 for MFD. Maternal heritability estimates were 0.01 for BW and 0.006 for CFW, with corresponding dam permanent environmental ratios of respectively 0.03 and 0.02. The genetic correlation between animal effects amounted to 0.48 for BW. Derived proportions of the total phenotypic variance due to SFYS were 0.02, 0.02 and 0.02, respectively. Genetic correlations of BW with CFW and MFD were 0.11 and 0.13, respectively, and of CFW with MFD 0.16. It was concluded that the inclusion of some form of a genotype by environmental interaction as part of the national evaluation is essential, although it controlled only a modest portion of the overall phenotypic variation. [ABSTRACT FROM AUTHOR]

The actual level of inbreeding and the effect of inbreeding depression on yearling body weight and fleece traits in the South African Dohne Merino population were investigated. All available pedigree data, which comprised of 266 268 records (302 169 animals including base parents) for the period 1975 to 2003 were used for calculating individual inbreeding coefficients. Inbreeding depression was estimated as the regression of performance (corrected for fixed effects) on the individual and dam inbreeding coefficients, fitting an animal model. The rate of inbreeding (ΔF) was estimated as the difference between the individual inbreeding (Ft) and the inbreeding of the parents (Ft-1) divided by (1-Ft-1). The level of inbreeding (F) in the SA Dohne Merino sheep population is very low. The proportion of animals that was inbred to some extent increased from 0.00 (average F = 0) in 1980 to 0.38 in 2003 (average F = 0.012). No significant inbreeding depression on body weight and fleece traits could be found. In general the results suggest that inbreeding at present is not a serious problem in the South African Dohne Merino breed. [ABSTRACT FROM AUTHOR]

Genetic and environmental parameters were estimated for pre- and post-weaning average daily gain (ADG1, ADG2) and Kleiber ratio (KR1, KR2) using the ASREML program. Twelve models, formed with inclusion or exclusion of the maternal genetic, permanent environmental and common (litter) environmental variance components and the covariance between the direct and maternal additive effect on the basic direct additive genetic model, were used. The same models were applied to birth weight (BWT), weaning weight (WWT) and bi-monthly weights to 12 months of age (WT2 to WT12), and weight at 18 months of age (WT18). Two-trait analyses were done among all traits. Maternal genetic and common environmental components were found to be important for ADG1, KR1 and weights up to six-months of age, while the common environmental component was found to be important for ADG2 and KR2. The maternal permanent environmental component was important for WT2 and WWT. Total heritability estimates for ADG1, ADG2, KR1 and KR2 were 0.13, 0.04, 0.13, and 0.01, respectively. Direct genetic correlations of ADG1 with BWT, WWT and WT6 were 0.01, 0.96 and 0.84 while with KR1 they were -0.40, 0.75 and 0.66, respectively. The relatively higher heritability in weight traits and the presence of positive and high correlations of weight traits with daily gain and Kleiber ratio tend to suggest that it would be more practical to select on the weight traits to improve gain and efficiency. [ABSTRACT FROM AUTHOR]

Yearling live weight and fleece trait data were obtained from between 2214 and 2270 yearling SA Mutton Merino progeny of the Elsenburg flock during a 20-year period from 1983 to 2002. Information of (co)variances for these traits in SA Mutton Merinos is exceedingly scarce in the literature. Estimates of (co)variance components and ratios were thus obtained from these data, using an Animal Model. Coefficients of variation, for live weight as well as greasy and clean fleece weight were above 18%. Corresponding values for clean yield and fibre diameter were below 9%. Estimates of heritability were 0.23 for yearling live weight, 0.38 for greasy fleece weight, 0.39 for clean fleece weight, 0.59 for clean yield and 0.67 for fibre diameter. Maternal permanent environmental variance ratios were only significant for live weight, greasy fleece weight and clean fleece weight, amounting to 0.09, 0.06 and 0.06, respectively. Genetic correlations between yearling live weight and wool weight were positive but low (0.14 for greasy fleece weight and 0.13 for clean fleece weight). Those of live weight with clean yield and fibre diameter were zero and 0.22, respectively. The genetic correlation between greasy fleece weight and clean fleece weight was 0.87. The genetic correlations of greasy fleece weight with clean yield and fibre diameter were -0.07 and 0.21, respectively. Corresponding correlations with clean fleece weight were 0.43 and 0.38, respectively. The genetic correlation of clean yield with fibre diameter amounted to 0.33. In most cases, the derived values were in agreement with those derived from Merino data sets. [ABSTRACT FROM AUTHOR]

Genetic parameters for production and reproduction traits in the Elsenburg Dormer sheep stud were estimated using records of 11743 lambs born between 1943 and 2002. An animal model with direct and maternal additive, maternal permanent and temporary environmental effects was fitted for traits considered traits of the lamb (birth and weaning weight and survival). Fixed effects were sex, birth status, year and age of dam. Weaning weights were pre-adjusted to a 100-day equivalent. For reproduction traits (considered as traits of the ewe), which included number and weight of lambs born and weaned, repeatability models were fitted. The random part consisted of direct additive and ewe and sire permanent environmental effects. Direct and maternal heritability estimates were 0.13 and 0.23 for birth weight and 0.07 and 0.09 for weaning weight. Corresponding proportions of total phenotypic variance due to maternal permanent and temporary environment were 0.09 and 0.28 and 0.06 and 0.22 respectively. The genetic correlation between animal effects was -0.23 in the case of birth weight. The results showed that temporary environment (full sibs within a year) generally has a major effect on all pre-weaning traits. The direct heritability estimate of survival was 0.02 while the temporary maternal environmental variance as a proportion of phenotypic variance was 0.10. The estimates obtained for number and weight of lambs born and weaned were generally low, ranging from 0.03 for number of lambs born to 0.11 for total weight at birth. The permanent environmental effect of the ewe accounted for 6-7% of the total phenotypic variance. Genetic correlations of total weight of lamb weaned with the other reproduction traits were generally high (0.64 to 0.92) with low standard errors. The corresponding phenotypic, environmental and ewe permanent environmental correlations were all medium to high and estimated with a fair deal of accuracy according to low standard errors. The genetic... [ABSTRACT FROM AUTHOR]

Breeding of beef cattle is changing, with more emphasis on efficiency of production. Feed cost is the highest expense, and reducing it has the potential to increase profitability. Common measures of efficiency are ratio traits such as feed conversion (feed consumed/weight gain) and feed efficiency (weight gain / feed consumed). Feed conversion ratio is commonly used in South Africa in an attempt to improve feed efficiency. These ratio traits are associated with growth rate. Selection for them would result in higher growth as a correlated response and might also increase the mature size of the cows and their maintenance cost. Thus, alternative efficiency traits such as residual feed intake and residual daily gain have been proposed. In this study, variance components, and genetic parameters for feedlot traits for the South African Simmentaler breed were estimated, with emphasis on the efficiency traits. The focus was to evaluate the use of residual feed intake as an alternative trait. The results indicate non-significant correlations between residual feed intake and body weight and growth traits, implying that residual feed intake should have little effect on the other traits. This is in contrast to the moderate to strong correlations of feed conversion ratio with the same traits. The study demonstrates that considerable genetic variation exists for residual feed intake, which can be exploited. Selection for residual feed intake can reduce the carbon footprint of beef due to the associated lower methane emissions. [ABSTRACT FROM AUTHOR]

Selection for production and reproduction in South African Merino sheep is always combined with selection based on visual appraisal and will, in all probability, remain so for many years to come. Heritabilities for acceptability were estimated using a threshold model to analyse data from two parent Merino studs. Effects included in the analysis were sex, birth status, age of dam and year of birth. An acceptable animal was defined as one that was present in the stud at 18 months of age, implying that such an animal would either be retained or sold for breeding purposes. This provided one threshold and two classes (acceptable or not acceptable). Records from the two studs used comprised 3011 progeny of 31 sires and 6495 progeny of 70 sires. Error variance was taken as unity and heritability estimated as h[sup 2] = 4sigma[sup 2, sub s] / 1 + sigma[sup 2, sub s] where sigma[sup 2, sub s] is the sire variance. Heritability estimates were 0.210 and 0.448. The results suggest that selection improvement for acceptability is possible, and that breeding values for this trait should be supplied for AI sires. [ABSTRACT FROM AUTHOR]

Subjectively assessed wool and conformation traits are widely used to select breeding ewes and rams in the sheep industry. Data from a Merino flock that is maintained at Elsenburg Research Farm were used to investigate animal model (co)variance components for ewe reproduction traits with subjectively assessed wool and conformation traits. Ewe reproduction traits were assessed at their first lambing opportunity at two years, or over a three-year period from their lambing opportunities at two to four years old. Relationships of ewe reproduction traits with subjectively measured wool and conformation traits were also investigated. All these traits were heritable, with a range from 0.16 ± 0.03 for topline (TOPL) to 0.64 ± 0.04 for woolly face score (WFS). Genetic correlations of number of lambs born (NLB1) with colour (COL), number of lambs weaned (NLW1) with COL and belly and points (BANDP) and total weight of lamb weaned (TWW1) with COL were negative and significant. Significant genetic correlations of ewe reproduction traits over three lambing opportunities were found between number of lambs born (NLB3) and WFS (0.23 ± 0.11) and between total weight weaned (TWW3) and face cover score (FCS) (-0.33 ± 0.16). Among these traits, the noteworthy favourable genetic correlation between total fold score (TOT) and NLB1 suggested that plainer ewes were more reproductive. This is important for the South African Merino industry as plainer sheep are more desirable because of their faster growth and higher lambing percentages and reduced chances of fly strike. Selection for improved ewe reproduction in Merino sheep thus would not result in marked unfavourable correlated responses in most of these subjective wool and conformation traits. [ABSTRACT FROM AUTHOR]

Subjectively assessed wool and conformation traits form part of the selection objective in wool sheep enterprises. The present study investigated the genetic, phenotypic and environmental correlations for nematode resistance (using faecal worm egg count (FEC)) with subjectively assessed wool and conformation traits. The Merino sheep flock (consisting of four lines) maintained on Tygerhoek Research Farm was used. Fixed effects of selection line, birth type, sex, age of dam in years, year of birth, and sex*birth year interaction had a significant effect on all subjective traits. At genetic level, log transformed FEC was significantly related to wool oil only at 0.18 ± 0.09, staple formation at 0.29 ± 0.10, and topline at -0.33 ± 0.11. These correlations suggested that sheep with high FEC are likely to have excessive wool oil, thicker and bulkier staples, and lower scores for topline. Selection for resistance to and resilience against nematodes in Merino sheep thus will not result in marked unfavourable correlated responses in the vast majority of these subjective wool and body conformation traits. [ABSTRACT FROM AUTHOR]

Genetic evaluation systems require the accurate estimation of genetic parameters. The genetic, phenotypic and environmental parameters for live weight and objectively measured wool traits were estimated for a South African Merino flock. Records of the Tygerhoek Merino resource flock were used to estimate these parameters. The database consisted of records of 4 495 animals, the progeny of 449 sires and 1 831 dams born in the period 1989 to 2004. The pedigree records used have been collected between 1969 and 2004. Direct heritability estimates (ha²) for 16-month live weight (LW) and objectively measured wool traits ranged from 0.20 for staple strength (SS) to 0.68 for fibre diameter (FD). Maternal heritability estimates ranged from 0.05 for LW and FD, to 0.10 for clean fleece weight (CFW). The proportion of the total phenotypic variance due to the maternal permanent environment variance (cpe²) amounted to 5% for fleece weights. The genetic correlation between animal effects for LW, greasy fleece weight (GFW) and CFW were -0.28, -0.65 and -0.70 respectively. The genetic correlation between LW and CFW was positive, but low at 0.14. The other important genetic correlations among the wool traits ranged from low to high, and were variable in sign ((for GFW with CFW (0.87) and with staple length (SL - 0.18); CFW with clean yield (CY - 0.33) and with SL (0.29); FD with CY (-0.09), with SL (0.15), with SS (0.40) and with standard deviation of FD (SDFD - 0.38): CY with SL (0.33) and with SDFD (0.10); SS with coefficient of variation of FD (CVFD - 0.57) and with SDFD (-0.28); CVFD with SDFD (0.87)). These results suggested that worthwhile responses in the objectively measured traits can be achieved through direct and indirect selection. [ABSTRACT FROM AUTHOR]

Data were recorded for birth weight, birth coat score and weaning weight of between 2018 and 4235 Merino lambs born over a 17-year interval from 1986 to 2002. The resource population was divergently selected from the same base population since 1986, either for (H line) or against (L line) maternal multiple rearing ability. Direct additive genetic variances - expressed as a ratio of the total phenotypic variance (h², direct heritability) - were estimated at 0.12 ± 0.03 for birth weight, 0.70 ± 0.05 for birth coat score and 0.13 ± 0.04 for weaning weight. Maternal genetic variance ratios (m²) were estimated at 0.23 ± 0.04 for birth weight and 0.10 ± 0.04 for weaning weight. It was not significant for birth coat score. Maternal permanent environmental variance ratios (c²) for the respective traits amounted to 0.08 ± 0.03 for birth weight, 0.04 ± 0.02 for birth coat score and 0.08 ± 0.03 for weaning weight. No consistent phenotypic or genetic differences in favour of either line were found for birth weight or birth coat score. Compared to L line lambs, phenotypic means for weaning weight were heavier in favour of H line lambs from 1995. This trend was confirmed by divergence in yearly averaged direct breeding values in the H and L lines. Expressed as percentage of the overall phenotypic mean for weaning weight, genetic changes amounted to +0.23% in the H line and -0.26% in the L line. A corresponding maternal genetic trend amounting to -0.19% of the overall phenotypic mean for weaning weight was found in the L line, while no maternal genetic change could be discerned in the H line. Divergent selection for multiple rearing ability thus did not influence birth weight and birth coat score, while the correlated response in weaning weight was favourable. [ABSTRACT FROM AUTHOR]

Presents information on a study which evaluated the pelt traits in Karakul sheep. Materials and methods; Results and discussion; Conclusion.

Preliminary genetic parameters for nodule traits of ostrich skins were estimated to examine whether genetic improvement of skin quality is feasible. Average nodule size and density per dm⊃2 were determined on five localities on each of 439 ostrich skins. An animal model with random animal and skin permanent environmental effects was fitted for the traits considered. Fixed effects were locality on skin, age, year of hatch and gender. Locality significantly influenced nodule size and nodule density. Nodule size increased with an increase in slaughter age, while nodule density decreased. Estimates for heritability were low at 0.10 for both traits, but still differed significantly from zero. The genetic correlation between nodule density and average nodule size was very high at -0.72. The skin permanent environmental correlation was -0.33, the environmental correlation -0.17 and the phenotypic correlation was -0.28. More research into genetic variation within localities and correlations with other easily measurable traits is indicated for genetic improvement of ostrich leather quality. [ABSTRACT FROM AUTHOR]

Genetic parameters for growth traits in the South African Brahman breed were estimated using ASREML from data records of birth weight (BWT) = 41 509, weaning weight (WWT) = 37 705, yearling weight (YWT) = 22 682 and final weight (FWT) = 13 055 collected between 1985 and 2002. The direct additive contribution to BWT, WWT, YWT and FWT were 0.28, 0.14, 0.14 and 0.18 respectively. The corresponding maternal heritability estimates were 0.11, 0.06, 0.05 and 0.03 respectively. The maternal permanent environmental component due to the dam contributed 3-7% of the total phenotypic variances of the traits under consideration. The corresponding contribution of herd-year-season x sire interaction ranges from 5% to 6%. The genetic correlation between animal effects was -0.36 for BWT. The prospects of improvement of these traits by selection seem possible and contribution of maternal permanent environment due to dam is of considerable importance as maternal effects. [ABSTRACT FROM AUTHOR]

The wildlife industry in South Africa has shown immense growth since the 1990s, which was brought about by the private game segment of the industry. In recent years, trophy quality Cape buffalo breeding animals have achieved extremely high prices. Much of the economic value of these animals can be attributed to horn size, which is important for breeding and hunting purposes. The main objective of the study was to estimate variance components for horn traits of economic importance as well as to develop guidelines for recording these traits. To date, no quantitative genetic analysis has been done for any traits in Cape buffalo. The total number of horn measurement records included in the evaluation was n = 945 for outer spread (BHSO), n = 470 for tip to tip (BHTSCI), n = 468 for left boss and n = 479 for right boss. For descriptive statistics, males and females were considered separately while age was divided into clusters of six months. A multi-trait animal model using Monte Carlo Markov Chains methods was used for the estimation of genetic parameters. Results suggest that it is not economically viable to measure horn spread and tip to tip of females after 48 months of age. Horns of the males continue to grow beyond 91 months of age. Boss records were unreliable owing to the applied measurement techniques for female and young animals. An inbreeding coefficient of 0.008 was calculated, suggesting adequate genetic diversity in the studied population. The heritability estimates of the horn traits were low, showing that extreme care has to be taken to develop effective selection programmes for the buffalo game industry using their horn genetic parameters. Further quantitative studies are required to support the results of the current study. [ABSTRACT FROM AUTHOR]

Much of the economic value of wildlife can be attributed to horn size, which is an important trait for trophy hunters. The main objective of the study was to estimate genetic parameters for the economically important horn traits of sable antelope that are currently being measured in the South African industry. To date, no quantitative genetic analysis has been done for any traits in sable antelope. The total number of records included in the evaluation were n = 1713 for horn length (SHL), n = 1503 for circumference (SHC), n = 1486 for tip to tip (SHTT), n = 1505 for tip length (SHT), and n = 1447 for rings (SHR). Males and females were considered separately in six-month age clusters. A Markov chain Monte Carlo (MCMC) multi-trait analysis was used to estimate (co)variance parameters for the horn traits. The results indicate a sex effect for all the traits and suggest that it is not economically viable to measure horn length of either sex after 54 months old. The horns of females are on average 40% shorter compared with bulls at maturity. Continuous horn growth throughout the lifetime of sable is suggested by the formation of ring posts, but is often masked by horn attrition and inadequate measuring techniques. An inbreeding coefficient of 0.0043 suggests adequate genetic diversity in the studied population. Heritability estimates of horn traits varied from 0.085 to 0.52, while genetic correlations ranged from 0.1 to 0.6 with the highest correlation being found between horn length and tip to tip. Further studies are recommended to confirm these results. [ABSTRACT FROM AUTHOR]

Longevity is a major component of the breeding objective for dairy cattle in many countries because of its high economic value. The trait has been recommended for inclusion in the breeding objective for dairy cattle in South Africa. Linear models, random regression (RR) models, threshold models (TMs) and proportional hazard models (PH) have been used to evaluate longevity. This paper discusses these methodologies and their advantages and disadvantages. Heritability estimates obtained from these models are also reviewed. Linear methodologies can model binary and actual longevity, while RR and TM methodologies model binary survival. PH procedures model the hazard function of a cow at time t derived from survival from first calving to culling, death or censoring. It is difficult to compare methodologies for sire evaluation and ranking across countries because of the variation in the definition of longevity and the choice of model. Sire estimated breeding values (EBVs) are derived differently for the models. Sire EBVs from PH models are expressed as deviations of the culling risk from the mean of the base sires, expected percentage of daughters still alive after a given number of lactations, expected length of productive life in absolute terms or as standard deviation units. In linear, TM and RR modelling, sire EBVs for longevity have been expressed as deviations of survival from the mean estimated with Best Linear Unbiased Prediction (BLUP). Appropriate models should thus be developed to evaluate functional longevity for possible inclusion in the overall breeding objective for South African dairy cattle. [ABSTRACT FROM AUTHOR]

Merino lines that were divergently selected from the same base population from 1986 to 2009 for their ability to rear multiples were assessed for dag score in autumn and spring, breech wrinkle score, and crutching time. Animals in the Low (L) line had higher dag and breech wrinkle scores and took longer to be crutched than High (H) line contemporaries. Expressed relative to H line least squares means, means of L line individuals were respectively 54%, 65%, 42% and 40% higher for autumn dag score, spring dag score, breech fold score, and crutching time. Gender effects for dag score were inconclusive, as ewe hoggets were more daggy than rams in autumn, with an opposite trend in spring. Shearer (n = 6) also affected crutching times, with an almost twofold difference in mean crutching time from the quickest shearer (27.7 ± 3.1 seconds) to the slowest shearer (49.4 ±3.7 seconds). The inclusion of dag score and breech wrinkle score as linear covariates in an analysis on crutching time eliminated the effect of selection line. It thus seems that the quicker crutching times of H line animals may be related to line differences for dag score and, to a lesser extent, for breech wrinkle score. [ABSTRACT FROM AUTHOR]

The utilization of non-linear threshold models and linear animal models to estimate variance components for categorical reproductive traits in beef cattle was investigated. Three traits, retention (RET), stayability (STAY) and calf tempo (CT) were defined. The data set consisted of 36 880 Afrikaner beef cattle measurements recorded over a period of 10 years. After editing, the records of 7 746 females from 473 sires were available for the genetic parameter estimation for RET. The corresponding number of records for STAY and CT were 3 018 (243 sires) and 7 653 (465 sires), respectively. Using GFCAT, sire variances for RET, STAY and CT were estimated as 0.202, 0.072 and 0.114, respectively. With error variances pre-set to one, the heritability estimates on the underlying scale were calculated as 0.67, 0.27 and 0.41 for RET, STAY and CT, respectively. From the three traits analyzed in this study CT probably reflects the true fertility of the bull's female progeny best. [ABSTRACT FROM AUTHOR]

The object of this study was to estimate heritabilities and genetic correlations for reproductive traits in a composite multibreed beef cattle herd using multitrait analysis. A REML procedure fitting a multitrait animal model was used to analyse data. Heritabilities and genetic correlations for calving interval (CI), calving date (CD), calving date with a penalty score (CDP) and age at first calving (AFC) were estimated as traits of the dam. The estimated heritabilities for CI, CD, CDP and AFC obtained in this study were 0.01, 0.04, 0.06 and 0.40 respectively with a repeatability of 0.07, 0.12 and 0.13 for CI, CD and CDP. Genetic correlations between traits varied from low to moderate, except for high correlations between CD and CDP (0.98), CI and CD (0.75) and between CI and CDP (0.79). Heritabilities, genetic correlations and repeatabilities of CD and CDP obtained in this study suggest that CD and CDP are the same traits and that selection for CDP rather then for CD does not have any additional advantages. Due to the additional advantages of CD over CI and the fact that CD is a less biased measurement of the female reproductive complex, CD and AFC (because of its high heritability) may be considered as selection criteria for improvement of reproduction in beef cattle herds. [ABSTRACT FROM AUTHOR]

The object of this study was to estimate heritabilities and sire breeding values for stayability and reproductive traits in a composite multibreed beef cattle herd using a threshold model. A GFCAT set of programmes was used to analyse reproductive data. Heritabilities and product-moment correlations between predicted breeding values for stayability at 36, 48, 60, 72 and 84 months of age, calving success and longevity were estimated. The estimated heritabilities on the underlying scale for these traits were 0.06, 0.10, 0.06, 0.03, 0.11, 0.03 and 0.08 respectively. Product-moment correlations between breeding values for stayability traits were low. The highest correlation of 0.22 was obtained between the ages of 36 and 48 months. Heritability estimates and correlations between traits appear to be of such a low magnitude that selection for these characteristics would result in limited genetic improvement, and also indicate that sires had little influence on the stayability, longevity or calving success of their daughters. [ABSTRACT FROM AUTHOR]

Presents information on a study which estimated the genetic parameters and trends from a South African Mutton Merino nucleus breeding scheme using multiple trait mixed model procedures. Materials and methods; Results and discussion; Conclusions.

An objective was defined for a breeding program in South Africa to improve the female fertility of the national herd. The aim of the study was to change the approach of defining a trait based on female fertility and to define the trait, reproduction merit, as an indicator of the efficiency of male animals as sires in a given population. Reproductive merit reflects the retention of male animals in a given population, but has the added advantage that it will also yield information on the reproduction performance of a sire's female offspring in that population. Data was extracted from the INTERGIS (Integrated Registration and Genetic Information System) for the Afrikaner beef breed in South Africa. Only data of females of sires older than nine years were included in the data to estimate the variance components, in order to give all sires an equal opportunity have female offspring presented in all five categories. Effects included in the models were a breeder*year of birth*season (h*y*s) concatenation. For the linear analysis h*y*s was included as either fixed or random. Sire variances, using non-linear and linear models, were estimated as 0.06 (GFCAT), 0.052 (REML, h*y*s fixed) and 0.063 (REML, h*y*s random). The correlation between the solutions for the two REML models (fixed or random) was 0.73. Correlations between solutions from GFCAT and REML with h*y*s fitted as fixed or random were 0.99 and 0.73 respectively. [ABSTRACT FROM AUTHOR]