Effect of age at first calving and heat stress at parturition on reproductive efficiency and postpartum disorders in Holstein heifers

Miguel Mellado,Vanessa Alba,Leticia Gaytán,Jesús Mellado,José E García

doi:10.5424/sjar/2019172-13544

Miguel Mellado, Vanessa Alba + Show 3 more

Open Access

https://doi.org/10.5424/sjar/2019172-13544

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Abstract

The objective of this study was to evaluate the impact of age at first calving (AFC) and climatic conditions at calving on peripartum disorders and reproductive performance in Holstein heifers in a hot environment. A total of 3000 reproductive records from a large highly technified dairy farm were used; the variables evaluated were temperature humidity index (THI; <77, 77-83, >83) at calving and AFC (<2.0, 2.0-2.2 and >2.2 years). Across age groups, the cases of dystocic parturition increased (p<0.05) when the deliveries occurred with severe heat stress (4.3% vs. 3.3% for THI >83 and <83 units, respectively). Across THI, conception rate at the first postpartum artificial insemination (AI) was lower (p=0.02) for heifers calving for the first time >2.2 years compared to heifers calving between 2.0 and 2.2 and <2.0 years (9.8, 15.3 and 13.7%, respectively). Conception rate at first AI postcalving was higher (p<0.01) in heifers calving with THI less than 83 units than in heifers calving with a THI >83 units (16.8 vs. 5.4%). The conception rate considering all services was affected (p<0.05) by AFC (42.7, 50.4 and 40.9% for AFC <2.0, 2.0-2.2 and >2.2 years, respectively). The interaction AFC × THI at calving was significant (p<0.05). The occurrence of metritis was higher (p<0.05) in heifers <2.0 years of age at calving than those calving after 2 years of age. The presence of ovarian cysts was less common (p<0.05) in heifers with greater AFC. In conclusion, increasing the AFC in Holstein heifers had no benefits in reproduction and health, compared with heifers calving at <2.0 years. These data in a hot climate suggest that heifers should be selected to begin their first lactation before 2 years of age.

Highlights

Age at first calving (AFC) is a greatly important economic trait determining the profitability of intensive dairy operations, one strategy for reducing the costs of milk yield could be the shortening of the rearing period
A reduction in AFC in firstparity Holsteins cows has been associated with a lower first-lactation milk production (Ettema & Santos, 2004; Curran et al, 2013) and increased dystocia (Zaborski et al, 2009; Gaafar et al, 2011), which commonly occurs when the heifers are under 22 months old
In the area where this study took place, heat stress has been identified as an important risk factor for fetal losses in lactating Holstein cows (Mellado et al, 2016)

Summary

Introduction

Age at first calving (AFC) is a greatly important economic trait determining the profitability of intensive dairy operations, one strategy for reducing the costs of milk yield could be the shortening of the rearing period. The optimum AFC in Holsteins for maximum profit and without negative effects on milk yield and health during their lifetime should be 23 to 24.5 months of age (Ettema & Santos, 2004; Nilforooshan & Edriss, 2004). A reduction in AFC in firstparity Holsteins cows has been associated with a lower first-lactation milk production (Ettema & Santos, 2004; Curran et al, 2013) and increased dystocia (Zaborski et al, 2009; Gaafar et al, 2011), which commonly occurs when the heifers are under 22 months old. Dystocia is a negative factor for both reproduction, health and body weight (Moussavi & Mesgaran, 2008)

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