EFFECT OF HANDLING AND ENVIRONMENTAL VARIABLES ON THE PREGNANCY RATE OF RECIPIENT COWS

Abstract

This work aimed to verify the effects of the handling and thermal environment on the pregnancy rate of embryo-recipient zebu x European cows (n=94) as well as the behavioral and clinical aspects at the moment of embryo transfer. Cortisol was analyzed by plasmatic samplers collected on D0, D9 and D16 of the hormonal treatment for estrous synchronization; blood was also sampled to analyze progesterone levels at the moment of embryo transfer. There was no difference (p>0.05) between pregnant and not pregnant females for maturation stage and embryo classification, coat, and reactivity between fresh and frozen embryos. The cortisol concentrations decreased (p>0.001) between D0 and D16, and the concentration of progesterone was similar in function of the pregnancy stage. Nevertheless progesterone in D16 for non pregnant cows was lower than for pregnant ones in the same day. Moreover, pregnant cows showed lower skin temperature. The values of Black Globe-Humidity Index were at very high limits, indicating that all animals could be under heat stress. The regression analysis indicated a tendency (p=0.08) to increase the pregnancy probability of 25% between the beginning and end of the afternoon. Thus, low plasmatic concentration of progesterone and high skin temperature represents a factor of thermal discomfort at the moment of the embryo receiving, influencing the pregnancy rate of recipient cows. As observed, heat stress decreased the probability of the pregnancy of recipient cows in tropical environment.

KEYSWORDS: Beef cattle, cortisol, handling, heat stress, pregnancy rate.