Effect of Body Weight and Growth in Early Life on the Reproductive Performances of Holstein Heifers
Angela Costa | Carlo Boselli | Massimo De Marchi
In Italy most dairy cows produce milk for cheese manufacture and are farmed in intensive systems, with free stall barns, milking parlor or robotic milking, total mixed ration and no (or limited) access to pasture. The main objective for farmers is to maximize farm income and minimize farm costs by adopting strategies and ‘best practices’ in the early life of heifers. Monitoring body weight (BW) and fertility of young stock is fundamental to ensure good performances in future dairy cows and to enhance farm profit. In this study BW (kg) and average daily gain (ADG, kg/d) recorded at different stages in early life of 382 Holstein calves were used to estimate associations with fertility traits. Data consisted of BW at birth (BW<sub>0</sub>), three BWs (BW<sub>1</sub>, BW<sub>2</sub>, and BW<sub>3</sub>) recorded in three phases of calf’s early life, ADG in the three phases (ADG<sub>I</sub>, ADG<sub>II</sub>, and ADG<sub>III</sub>), ADG of the entire period (ADG<sub>I-III</sub>), number of services per pregnancy (NS), and age at first calving (AFC). As expected, the four BWs were positively correlated to each. In general, heavier calves were characterized by better fertility compared to lighter calves. Monitoring BW and ADG in replacement heifers starting from the early age is recommended to improve NS and AFC at farm level and could be useful to set up genetic improvement programs. Future studies will benefit from the addition of milk-related traits and the increase of sample size (number of farms).
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