GM 20. Evidence for the existence of a major gene influencing hair Length and heat tolerance in bos taurus cattle

Abstract

A total of 28 calves from Angus sires and Senepol × Hereford or Hereford × Senepol dams were evaluated for hair length, rectal temperatures, respiration rates, and weights. In addition, ten purebred Angus calves were included in the study as control. Measurements were taken on three consecutive weeks during the hot summer months and also during the cooler late fall. Length of the hair was evaluated using a subjective system of classification (1 - 4). The lowest values describe the typical extremely short hair of pure Senepol cattle and of its crossings F1 with Bos taurus. Twelve of the 28 calves were thus coded as slick-haired and 16 as normal-haired; this ratio does not differ significantly from the 1:1 ratio. Rectal temperature (RT) of the yearling calves of short hair was smaller (P<.02) that the one of the A in two of the dates in the summer and two of the dates in fall sessions. The TR of yearling calves 25 % S of short hair was smaller (P<.04) that of its contemporaries of normal hair in two of the three dates in the summer. TR of yearling calves 25 % Senepol calves of bulls A and with normal coat, was not different (P>.07) of the A in any of the dates. A group of 15 yearling calves of Charolais bulls in cows F1 A × S it was classified by length of hair to the end of September. Seven of these yearling calves were classified as short hair and eight like normal hair. These data suggest a greater gene for length of the hair and tolerance to the heat it could exist in the Senepol breed