Abstract
Aim of study: To estimate the heritability and genetic correlations for lactation curve traits in buffaloes.Area of study: The buffalo cows were raised on properties located in the states of São Paulo, Ceará and Rio Grande do Norte, Brazil.Material and methods: The individual parameters of Wood’s model ( , , and ) were obtained using a non-linear mixed model. Peak yield (PY), peak time (PT) and lactation persistency (LP) were also calculated. These individual parameters were employed in multi-trait analysis with the milk yield (MY) using Bayesian inference.Main results: The heritability estimates were of low to moderate magnitudes, with values ranging from 0.156 ( ) to 0.299 (PY). The estimates for genetic correlation between the Wood’s parameters and MY were of low to high magnitude and ranged from -0.533 ( and MY) to 0.983 (PY and MY).Research highlights: The heritability estimates obtained indicate that the traits studied can be used in animal breeding programs.
Highlights
Buffaloes (Bubalus bubalis) are used in many countries for mozzarella cheese production because of the higher percentage of milk protein and fat
Wood’s model was applied to fit the lactation curves: yytt = θθ1ttθθ2 eeeeee−θθ3tt where yt represents the test-day milk yield in the month t; θ1 has a scale meaning and tends to increase with parity, i.e. according to the production level of animals; θ2 controls the rate of increase to the lactation peak; θ3 expresses the rate of decline after the peak and its absolute value tends to increase with parity (Macciota et al, 2011)
The nonlinear mixed model used in this case can be described as: yyiiii = ff(θθii, xxiiii) + gg(θθii, σσ, xxiiii)εεiiii where yij, xij and εij represent, in this order, milk yield, lactation month and error related to the ith animal and jth test-day; θi is the vector of individual parameters of Wood'syyfiiuii n=ctifof(nθ;θiif,(x.x)iiiia)n+d gg((.θ)θii,aσrσe, xfxuiiini)cεtεiiioii ns that define the structure of the individual effects and the residuals, respectively (Comeytsyiiiei t=alf.f,(2θ0θii1, 7xx)ii.ii)Fo+r gg((.θ)θiwi, σaσs, xcxoiiiin)sεiεidiiiered a function composed of a constant and a parameter dependent on θi and xij
Summary
Buffaloes (Bubalus bubalis) are used in many countries for mozzarella cheese production because of the higher percentage of milk protein and fat. Aim of study: To estimate the heritability and genetic correlations for lactation curve traits in buffaloes. Short communication: Genetic analysis of lactation curves in buffaloes, using Wood’s model.
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