Physiological parameters, hair coat morphological characteristics and temperature gradients in holstein-gyr crossbred cows

Abstract

ABSTRACT:The aim of this study was to assess physiological parameters, hair coat morphological characteristics and temperature gradients in crossbred Holstein-Gyr cows in the municipality of Tapira, Minas Gerais (MG), Brazil. Forty-nine lactating cows from six Holstein (H) and Gyr (G) genetic groups (1/4H 3/4G, 3/8H 5/8G, 1/2H 1/2G, 5/8H 3/8G, 3/4H 1/4G and 7/8H 1/8G) were distributed in a completely randomized design. The dry-bulb temperature and relative humidity were recorded, and the temperature and humidity index (THI) was calculated. The rectal temperature, respiratory rate and body surface temperature were measured, as were hair thickness, numbers, length and angle. Cows with a greater than 50% Holstein breed ratio (5/8H 3/8G, 3/4H 1/4G and 7/8H 1/8G) showed a higher respiratory rate and greater hair length than animals with genetic composition equal to or greater than 50% Zebu (1/2H 1/2G, 3/8H 5/8G and 1/4H 3/4G). Animals from the 1/2 and 1/4 HG genetic groups showed the greatest hair angle (P<0.05). With respect to climatic characteristics, the examined locality was within the thermoneutral zone and therefore did not impose conditions of thermal stress. The animals exhibited thermoregulation and hair coat characteristics that were within physiological parameters.

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

“…Hair length differed significantly between the genetic groups, with higher values observed in the animals with greater Holstein breed genetic composition. The hair length measured in the ¾ HG animals was similar to the 1.01 cm described by Cruz et al (2016). These authors found, however, lower values in the ⅞ HG cows (0.85 cm), which may be due to European genetics being more evident in the ⅞ HG animals and their predisposition to having longer hairs due to their taurine origin.…”

“…Both genetic compositions exhibited similar values (32.507 and 32.300 ºC for ¾ and 7/8 HG, respectively), as the animals were under the same environmental conditions and had access to sunlight interceptors and natural shading. The average surface temperatures measured in the present study were higher than the 30.64 in ¾ HG animals and 30.97 ºC in ⅞ HG animals (average: 20.25 °C) reported by Cruz et al (2016). However, there were no signs of stress for this trait.…”

“…There was no significant difference between the genetic compositions for RT, with both groups exhibiting values close to 38.3 ºC. These values are similar to the average 38.77 and 38.98 ºC described by Cruz et al (2016) in ¾ HG and ⅞ HG animals, respectively. Ferro et al (2019) found a similar RT value, 38.56 ºC, in ¾ HG animals under similar conditions.…”

“…In the evaluation of thermoregulatory performance, no significant difference was observed for number of hairs (Table 5), whose results were 509,952 and 563,050 for the ¾ and ⅞ HG cows, respectively. These values are higher than those described by Ferro et al (2019) for ¾ HG animals (469.14) and lower than those found by Cruz, Monteiro, Guimarães, Antunes andNascimento (2016) in ⅞ HG animals (1589.79). The number of hairs per square centimeter is important for the protection of the epidermis layer.…”

Copy number variation regions in Nellore cattle: Evidences of environment adaptation

“…The light color hair reflects a large proportion of solar incident radiation and also acts to reduce heat exchange via radiation (Hutchinson and Brown, 1969;Cardoso et al, 2015). To better dissipate the heat, indicine cattle also have a higher hair angle and a low hair density per skin area (Cruz et al, 2016). All these physiological mechanisms are highly associated with the term pointed out, evidencing its better environmental adaptation.…”