Thermoregulatory, behavioral, and production traits of ½ and ¾ Holstein/Gir dairy cows

Abstract

The aim of this study was to evaluate thermoregulatory, behavioral, and production traits of Holstein/Gir dairy cows of different genetic compositions. The experiment was carried out in the municipality of Turvânia - GO, Brazil, from July to December 2017. Twenty lactating cows of two genetic groups (½ and ¾ Holstein/Gir [HG]) were used in a completely randomized design where they were subjected to a rotational-grazing system in 24 irrigated Mombasa grass pastures with one day of occupation and 24 days of rest, and fed a 22% CP supplemental concentrate diet. During the experimental period, thermoregulatory, behavioral, and production data were collected on 12 occasions, at 15-day intervals. Environmental data such as ambient temperature, air relative humidity, and temperature-humidity index were recorded. Number of hairs, hair length and thickness, body surface temperature, rectal temperature, and respiratory frequency were analyzed as thermoregulatory traits. The behavioral assessment was undertaken by observing the feeding behavior, rumination, rest, and other activities. To determine production traits, milk yield and composition were analyzed. A higher respiratory frequency was observed in ¾ HG cows compared with ½ HG cows (p<0.05). Cows of the ½ HG group produced milk with higher protein contents (p<0.05). Rectal temperature, body temperature, number of hairs, hair length and thickness, feeding behavior, rumination, rest, and other activities were similar (p>0.05) between the two genetic groups, and the same was true for milk yield, fat and lactose contents, and somatic cell count.