Genetic relationships of fertility traits with test-day milk yield and fat-to-protein ratio in tropical smallholder dairy farms.
The test-day milk fat-to-protein ratio (TD-FPR) could serve as a measure of energy balance status and might be used as a criterion to improve metabolic stability and fertility through genetic selection. Therefore, genetic parameters for fertility traits, test-day milk yield (TD-MY) and TD-FPR, as well as, their relationships during different stages of lactation, were estimated on data collected from 25 968 primiparous Thai dairy crossbred cows. Gibbs sampling algorithms were implemented to obtain (co)variance components using both univariate linear and threshold animal models and bivariate linear-linear and linear-threshold animal models with random regression. Average TD-MY and TD-FPR were 12.60 and 1.15. Heritability estimates for TD-MY, TD-FPR and selected fertility traits ranged from 0.31 to 0.58, 0.17 to 0.19 and 0.02 to 0.05, respectively. Genetic correlations among TD-FPR and TD-MY, TD-FPR and fertility traits, and TD-MY and fertility traits ranged from 0.05 to -0.44, from -0.98 to 0.98 and -0.22 to 0.79, respectively. Selection for lower TD-FPR would decrease numbers of inseminations per conception and increase conception at first service and pregnancy within 90 days. In addition, cow selection based only on high milk production has strong effects to prolong days to first service, days open and calving interval.
The Bureau of Biotechnology in Livestock Production, Department of Livestock Development, Pathumthani, Thailand.
Sayan
S
Buaban
Department of Animal Science, Khon Kaen University, Meaung, Khon Kaen, Thailand.
Monchai
M
Duangjinda
Department of Life Science and Agriculture, Obihiro, Japan.
Mitsuyoshi
M
Suzuki
Department of Life Science and Agriculture, Obihiro, Japan.
Yutaka
Y
Masuda
The Bureau of Biotechnology in Livestock Production, Department of Livestock Development, Pathumthani, Thailand.
Jureeratn
J
Sanpote
Department of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan.
Keigo
K
Kuchida
D000818:Animals; D002417:Cattle / Q000235:genetics* / Q000502:physiology; D003612:Dairying; D005223:Fats / Q000032:analysis*; D005260:Female; D005298:Fertility; D006824:Hybridization, Genetic; D007774:Lactation / Q000235:genetics* / Q000502:physiology; D008297:Male; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis*; D019655:Quantitative Trait, Heritable; D014329:Tropical Climate
D005223:Fats; D008894:Milk Proteins
crossbred; fertility; genetic correlation; milk fat-to-protein ratio; tropics