Abstract
ABSTRACTWe used data collected on 48,739 cows from 1982 to 2013 from Foka farm in the Isfahan province of Iran to assess the reasons for culling in Iranian Holstein dairy cattle in the context of breeding values of economic traits, and also to study the relationship between longevity and production traits. Estimation of (co)variance components and genetic parameters for studied traits including MY, FY, herd life (HL) and length of production life (LPL) was by AI-REML algorithm in WOMBAT software. The results showed that 27.11% of cows were culled voluntarily under the farmers’ command. The number and reasons for culling animals varied considerably over the years. Also, the results showed that involuntarily culled animals were valuable with significantly higher breeding values for MY and FY (P < .0001) than those of voluntarily culled individuals. The estimates of heritability for longevity traits (HL and LPL) were low (0.11 and 0.09), but their genetic correlation with production traits were high and positive (0.63–0.70). Our results suggest that some opportunity may exist for genetic improvements in fat and milk yield in Iranian Holsteins.
Highlights
A number of female cows in dairy cattle farms are culled and replaced by heifers
The real longevity is strongly dependent on the milk yield and the functional longevity is the ability of the cow to avoid culling for other reasons than low performance
Statistics of culling in many dairy herds show that after low milk production, the main reasons for culling dairy cows are due to infertility and mastitis problems (Caraviello et al 2004)
Summary
A number of female cows in dairy cattle farms are culled and replaced by heifers. In constant conditions of herd size, replacement rates are reduced and higher profitability of heifers is obtained by increasing longevity of female cows which would lead to profitability of the dairy cattle enterprise (Berry et al 2005). Statistics of culling in many dairy herds show that after low milk production, the main reasons for culling dairy cows are due to infertility and mastitis problems (Caraviello et al 2004). Moraveji (2008) through evaluation of the dairy cow culling rates and their causes in a number of dairy farms in several provinces in Iran came up with three main reasons of culling dairy cows in Iran: reproductive disorders, nutritional-metabolic abnormalities and infectious diseases. The objective of this study was to investigate the reasons of culling, compare the genetic capacity of cattle payoff (based on their genetic value) in Iranian Holstein dairy cattle in Isfahan province and for the first time estimate mean of breeding values of economic traits within culling groups in Iranian Holstein dairy cattle
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