Open AccessJournal Article
The effects of non-genetic factors and estimation of genetic and phenotypic parameters and trends for milk yield in Ayrshire cattle in Kenya
TLDR
The high variation as indicated by both large standard errors and low heritabilities of the milk trait indicate that much improvement in this trait could be achieved through improved management, and the negative annual genetic changes in milk yield observed could be due to ineffective breeding strategies both at herd and national level.Abstract:
Dairy cattle production in Kenya has been growing into an important agricultural sector, but it still faces numerous difficulties in environmental constraints. The purpose of this study was to identify significant non-genetic effects on milk production to give advices for farm management and estimate genetic and phenotypic parameters for milk traits. Data consisting of 4475 lactation records from 10 large-scale Ayrshire herds collected from 1980 to 2005 were used to evaluate effects of non-genetic factors and determine genetic and phenotypic parameters and trends of 305 d milk yield (305d MY). The data analyses using least square techniques of Proc GLM of SAS identified significant sources of variation by herd, parity and year of calving on 305d MY. The overall mean for 305d MY was 3009.8 ±1098 kg, with the corresponding heritability and repeatability estimates of 0.12 ±0.05 and 0.35 ± 0.01 respectively. Genetic trend for 305d MY was -2.1 kg/yr and statistically significant (P<0.01) indicating annual decrease in breeding values over the study period. The high variation as indicated by both large standard errors and low heritabilities of the milk trait indicate that much improvement in this trait could be achieved through improved management. The negative annual genetic changes in milk yield observed could largely be due to ineffective breeding strategies both at herd and national level.read more
Citations
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Genetic and phenotypic trends of 305-day milk yield of holstein cows raised at commercial farm in egypt
TL;DR: Although the trend in the estimated breeding values found for cows was positive, it still did not lead to change in the average milk production due to the probable reduction in the nutritional and /or management conditions of the herd.
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Modeling heat stress effects on dairy cattle milk production in a tropical environment using test-day records and random regression models.
J.M. Mbuthia,M. Mayer,N. Reinsch +2 more
TL;DR: In this paper, the authors used random regression models to detect heat stress thresholds, milk yield loss and individual animal variations using test-day milk records from the Kenya Livestock Breeders Organization for the years 2000-2017.
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Genetic and environmental parameters and trends for milk production of Holstein cattle in Turkey
TL;DR: In this paper, the influence of genetic and environmental factors on milk production traits as well as genetic trends over 20 years from 1987 to 2006 were studied in three herds of Holstein cattle from three herds in Turkey.
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Effects of Parity on Postpartum Fertility Parameters in Holstein Dairy Cows
MohammedA Elmetwally,Abdelmonem Montaser,N Elsadany,W Bedir,Manal Shawky Hussein,Samy Zaabel +5 more
TL;DR: It is concluded that, the parity numbers, season and month have a significant effects on postpartum fertility parameters.
Estimation of covariance components for the first four lactations in Holstein cattle according to different models
Alejandro Palacios Espinosa,José Luis Espinoza Villavicencio,Dianelys González-Peña,Danilo Guerra Iglesias,Rafael de Luna-de la Peña,Felipe Alonso Rodríguez Almeida +5 more
TL;DR: In this article, three models were established to study the milk production of Cuban Holstein cows for 305 days during each of the first four lactations, and the data showed that for the Holstein breed under these study conditions, th e estimation of covariance components for milk yiel d in the first 4 lactations are best carried out using a multivariate animal model.
References
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Book
Introduction to quantitative genetics
TL;DR: The genetic constitution of a population: Hardy-Weinberg equilibrium and changes in gene frequency: migration mutation, changes of variance, and heritability are studied.
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Restricted maximum likelihood to estimate variance components for animal models with several random effects using a derivative-free algorithm
TL;DR: Estimates are obtained by evaluating the likelihood explicitly and using standard, derivative-free optimization procedures to locate its maximum by the so-called Animal Model, which includes the additive genetic merit of animals as a random effect, and incorporates all information on relationships between animals.
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Genetic and phenotypic parameters for 305-day yield, fertility, and survival in Holsteins.
C.M.B. Dematawewa,P.J. Berger +1 more
TL;DR: Management practices seem to keep mortality rates of high producing cows lower even though those cows have lower genetic potential for survival than do the low producers, as measured by yield, fertility and cow survival estimates.
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Genetics of milk yield and fertility traits in Holstein-Friesian cattle on large-scale Kenyan farms
TL;DR: 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, and there was little genetic control of either lactation length or calving intervals, but there was strong genetic correlations between first lactation milk yield, caling interval, and age at first calving.
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Genetic parameters for yield and reproductive traits of Holstein and Jersey cattle in Florida.
TL;DR: Estimates of genetic parameters and correlated responses in this subtropical environment did not differ appreciably from those that occur in temperate dairy areas.