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ALTERNATIVES FOR GENETIC IMPROVEMENT OF REPRODUCTIVE EFFICIENCY IN BEEF CATTLE (GESTATION LENGTH, CONCEPTION RATE, CALVING DATE, HERITABILITY, LOGISTIC MODEL)
Abstract
Genetic and environmental variability in gestation length, calving date and probability of conception on first service were analyzed using breeding and calving records from a large herd in the midwest. Twelve years (1972 to 1983) of data on cows sired by Simmental, Maine-Anjou, Limousin and Gelbvieh bulls were studied. Statistical analyses were performed separately on first, second and last parity records. Number of records in the three sets were: 4,474, 2,803 and 2,504 for gestation length; 7,049, 3,574, and 3,069 for conception rate; and 5,908, 3,767, and 2,856 for calving date. Year, interaction of year and season, and sex of calf or twin pregnancy affected gestation length. Bull calves were gestated 1.4 to 1.8 d longer and twins 5.4 to 7.2 d longer than heifer calves. Older cows had approximately 3 d longer gestation than heifers. Cow and calf heterosis were non-significant. Paternal half-sib estimates of heritability for gestation length, as trait of the calf, was 36 to 45%. Estimates of heritability of maternal additive effects were 2 to 13%. Estimated correlations between direct and maternal additive effects were -.72, -.46 and .68 in the three parities, respectively. Probability of conception on first artificial insemination was analyzed by weighted least-squares procedures after empirical proportions had been transformed to logits (logistic transforms). Pasture-group and year explained considerable variation in conception rate. Number of cows bred the same day, postpartum interval and average afternoon temperature the week prior to or following breeding were non-significant. Limousin and Maine-Anjou cows had lower conception rate than Simmentals and Gelbviehs. The paternal half-sib estimates of heritability of direct effects for conception rate were 6 to 10%. Estimates of heritability of maternal effects were 7 to 11%. Estimates of the correlation between direct and maternal effects were large and negative. Calving date, adjusted for yearly differences in first day of breeding season, was influenced by the same variables as gestation length. Paternal half-sib estimates of heritability for birth date of calf were 20 to 27%. Estimates of heritability of additive maternal effects for birth date were 6 to 7%, and the estimated correlations between direct and maternal additive effects were -.76 and -.43 in parities 1 and 2.
Subject Area
Livestock
Recommended Citation
AZZAM, SARA MELIN, "ALTERNATIVES FOR GENETIC IMPROVEMENT OF REPRODUCTIVE EFFICIENCY IN BEEF CATTLE (GESTATION LENGTH, CONCEPTION RATE, CALVING DATE, HERITABILITY, LOGISTIC MODEL)" (1985). ETD collection for University of Nebraska-Lincoln. AAI8526585.
https://digitalcommons.unl.edu/dissertations/AAI8526585