Genetics of milk yield and fertility traits in Holstein-Friesian cattle on large-scale Kenyan farms.

Imperial College at Wye, Ashford, Kent, UK.
Journal of Animal Science (Impact Factor: 1.92). 08/2001; 79(7):1742-50.
Source: PubMed

ABSTRACT Purebred Holstein-Friesian cows are the main exotic breed used for milk production on large, medium, and small farms in Kenya. A study was undertaken on seven large-scale farms to investigate the genetic trends for milk production and fertility traits between 1986 and 1997 and the genetic relationships between the traits. This involved 3,185 records from 1,614 cows, the daughters of 253 sires. There was a positive trend in breeding value for 305-d milk yield of 12.9 kg/ yr and a drop in calving interval of 0.9 d/yr over the 11-yr period. Bulls from the United States (U.S.) had an average total milk yield breeding value 230 kg higher than the mean of all bulls used; Canada (+121 kg), Holland (+15 kg), the United Kingdom (U.K., 0 kg), and Kenya (-71 kg) were the other major suppliers of bulls. Average breeding values of bulls for calving interval by country of origin were -1.31 (Canada), -1.27 (Holland), -0.83 (U.S.), -0.63 (Kenya), and 0.68 d (U.K.). The genetic parameters for 305-d milk yield were 0.29 (heritability), 0.05 (permanent environment effect as proportion of phenotypic variance) resulting in an estimated repeatability of 0.34. Using complete lactation data rather than 305-d milk yield resulted in similar estimates of the genetic parameters. However, when lactation length was used as a covariate heritability was reduced to 0.25 and the permanent environment effect proportion increased to 0.09. There was little genetic control of either lactation length (heritability, 0.09) or calving interval (heritability, 0.05); however, there were strong genetic correlations between first lactation milk yield, calving interval, and age at first calving.

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    ABSTRACT: The objective of this study was to estimate genetic parameters coupled with genetic and phonotypic trends for age at first calving (AFC) and first and second calving interval (CI1 and CI2) in Iranian Holstein cows. Records of reproduction from 1983 to 2007 for AFC, CI1 and CI2 were 261116, 163234 and 92661, respectively. Single and two trait animal model was used to estimate genetic parameters by restricted maximum likelihood procedures using Average Information algorithm in ASREML software. Estimates of heritability were 0.19±0.005 for AFC, 0.04±0.003 for CI1, and 0.04±0.004 for CI2. Genetic trends for AFC, CI1 and CI2 were -0.75±0.11, 0.004±0.02, -0.02±0.01day per year and phonotypic trends were -2.35±0.38, -1.13±0.39, -0.28±0.23 day per year, for AFC, CI1 and CI2, respectively. The genetic, phonotypic and environmental correlations were – 0.049, 0, 0.002 for AFC and CL1; 0.014, -0.004, -0.004 for AFC and CL2; and 0.877, 0.081, 0.043 for CL1 and CL2, respectively.
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    ABSTRACT: A total of 956 lactation records of Holstein cows kept at Kaa Albon station, Imuran Governorate, Yemen during the period from 1991 to 2003 were used to investigate the effect of some genetic and non-genetic factors (Sire, parity, season of calving, year of calving and age at first calving as covariate) on the Total Milk Yield (TMY), Lactation Length (LL), and Dry Period (DP). Components of variance for the random effects (mixed model) were estimated by Restricted Maximum Likelihood (REML) methodology. Sires were evaluated for the TMY by three methods, Best Linear Unbiased Prediction (BLUP) using Harvey program, Transmitting Ability (TA) according to the Least Square Means of sire progeny (TALSM) and according to Means (TAM). Results showed that TMY and DP were affected significantly (P < 0.01) by all factors except season of calving and age at first calving, while LL was affected significantly (P< 0.01) only by year of calving and parity. The averages of the TMY, LL, and DP were 3919.66 kg, 298.28 days, and 114.13 days respectively. The corresponding estimates of heritability (h²) were 0.35, 0.06, and 0.14 respectively. The highest and lowest BLUP values of sires for the TMY were – 542.44 kg and 402.14 kg, while the corresponding estimates for TALSM and TAM were – 470.38, 380.88 kg and – 370.12, 388.50 kg respectively. The Spearman rank correlation coefficients among BLUP, TALSM and TAM ranged from 0.81 to 0.67. These results provide evidence that the selection of sires will improve the TMY in this herd because of the wide differences in genetic poetical among sires, and a moderate estimation of heritability.

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