Linking first lactation survival to milk yield and components and lactation persistency in Tunisian Holstein cows.

Marwa Grayaa,Abderrahman Ben Gara,Sylvie Vanderick,Rodrigo Reis Mota,Boulbaba Rekik,Hedi Hammami,Nicolas Gengler,Siwar Grayaa,Christian Hanzen

doi:10.5194/aab-62-153-2019

Abstract

Genetic parameters were estimated for first lactation survival defined as a binary trait (alive or dead to second calving) and the curve shape traits of milk yield, fat and protein percentages using information from 25 981 primiparous Tunisian Holsteins. For each trait, shape curves (i.e. peak lactation, persistency), level of production adjusted to 305 days in milk (DIMs) for total milk yield (TMY), and average fat (TF %) and protein (TP %) percentages were defined. Variance components were estimated with a linear random regression model under three bivariate animal models. Production traits were modelled by fixed herd test-day (TD) interaction effects, fixed classes of 25 DIMs age of calving season of calving interaction effects, fixed classes of pregnancy, random environment effects and random additive genetic effects. Survival was modelled by fixed herd year of calving interaction effects and age of calving season of calving interaction effects, random permanent environment effects, and random additive genetic effects. Heritability () estimates were 0.03 () for survival and 0.23 (), 0.31 () and 0.31 () for TMY, TF % and TP %, respectively. Genetic correlations between survival and TMY, TF % and TP % were 0.26 (), () and (), respectively. Genetic correlations between survival and persistency for fat and protein percentages were () and (), respectively. Cows that had higher persistencies for fat and protein percentages were more likely not to survive.

Highlights

The cow’s life is divided into two distinct periods: a nonproductive period, from birth to first calving, and a productive period from first calving to death or slaughter
Pedigree and daily milk yield (MY), fat percentage (F %) and protein percentage (P %) test-day (TD) records of 25 981 primiparous Tunisian Holstein cows that participated in the official milk recording in the period from 2000 to 2014 were provided by the Tunisian Genetic Improvement Center (Tunisian Livestock and Pasture Office)
35.34 % of the latter cows left the herd in the first 100 DIMs, 19.87 % left the herd in the middle of lactation and 44.79 % left the herd during the last part of lactation

Summary

Introduction

The cow’s life is divided into two distinct periods: a nonproductive period, from birth to first calving, and a productive period from first calving to death or slaughter. It is closely related to the concept of survival to certain point of life, such as subsequent calving or a certain age (Van Pelt et al, 2016). It results from a combination of characteristics directly associated with the ability of the cow to remain in the herd (Tsuruta et al, 2005; Ahlman et al, 2011), i.e. being able to calve normally, while resisting metabolic disorders, diseases such as mastitis, infertility or lameness, and producing enough and good-quality milk (Weigel, 2006).

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