Fertility and hair coat characteristics of Holstein cows in a tropical environment

Abstract

This experiment deals with the effects of hair coat on the number of inseminations per conception in Brazilian Holstein cows. Data (n = 2446) were collected from 939 primiparous and multiparous Holstein cows in a commercial herd managed under an intensive freestall system and provided with cooling units (fans and sprinklers). The following hair coat characteristics were considered: hair length, coat thickness, hair diameter, coat color (proportion of black hairs), and the number of hairs per unit area. Low correlation values were observed between inseminations/conception and the following hair coat characteristics: coat color (r = -0.06), coat thickness (r = 0.07), number of hairs (r = -0.06), and hair diameter (r = -0.04). Analysis of variance showed significant effects of year, age, parity, dams’ sire within country of origin, and coat thickness. Cows with coats less than 2 mm thick had a lower (P < 0.05) number of inseminations/conception (2.4 ± 1.8) than those with more than 3 mm thickness (2.7 ± 2.1 inseminations/conception). It was concluded that a thick hair coat is associated with a reduced conception rate in Holstein cows in tropical environments because of chronic, high heat stress.