GENETIC PARAMETER ESTIMATES FOR FEMALE FERTILITY AND POST WEANING GROWTH AND EFFICIENCY TRAITS IN BEEF CATTLE

Abstract

The purpose of this thesis was to estimate genetic correlations between female fertility and feed efficiency measurements. Fertility data were collected from two Ontario beef herds and feed efficiency data were collected from one station with animals that originally came from five Ontario beef herds. Genetic parameters were estimated for female fertility traits (first-service conception rate, pregnancy rate, number of services per conception, gestation length and days-to-calving) and feed efficiency traits (feed conversion ratio, residual feed intake, average daily dry matter intake, average daily gain and metabolic mid-test body weight). Heritabilities for fertility traits were low to moderate and feed efficiency traits were moderate to highly heritable. Both traits need to be evaluated and considered in selection programs. Results indicate that animals with larger body weight are related to better fertility performance. An unfavourable correlation was found between residual feed intake and days-to-calving.