Behavioral, productive, reproductive and thermoregulatory performance of lactating 3/4 and 7/8 Holstein/Gir cows

Abstract

The aim of this study was to examine the behavioral, productive, reproductive and thermoregulatory performance of 3/4 and 7/8 Holstein/Gir (HG) dairy cows to identify which genetic composition suffers the least heat stress. A completely randomized design was adopted involving 20 multiparous, lactating crossbred cows from a dairy farm located in the municipality of Turvânia - GO, Brazil. During the experimental period, data on behavioral, productive, reproductive and thermoregulatory traits were collected every 15 days. Bioestat (5.0) statistical software was used for statistical analysis. The mean temperature-humidity index, ambient temperature and relative humidity obtained throughout the experimental period were 74.45, 30.51 ºC and 63.64%, respectively. In terms of reproductive performance, there was a significant difference (p < 0.05) between the genetic compositions for the time from calving to first service, with a longer period shown by the animals with greater Holstein breed genetic composition. Service period and calving interval differed significantly (p < 0.05) during the experimental period between the genetic compositions. A significant difference (p < 0.05) was also detected between the compositions for respiratory rate, with higher values observed in the animals with higher European genetic composition. Benezra thermal comfort index also differed significantly (p < 0.05), with the 7/8 HG animals showing a higher value. Lactating cows with a 7/8 HG genetic composition achieved better results in milk production, whereas those with 3/4 HG genetic composition showed superiority in milk fat composition and reproductive and thermoregulatory performance, indicating greater adaptation to the climatic conditions of the region.