Breeding and Genetics: Beef Cattle

Bovine infectious keratoconjunctivitis (BIK, pinkeye) is an economically important illness affecting growth of calves. The primary objective of this study was to estimate genetic parameters for BIK in beef calves prior to weaning. Health records of 47,880 calves born at the Meat Animal Research Center, Clay Center, NE from 1983 through 2001 were evaluated. Cows and calves were monitored daily for health until weaning at approximately 194 d of age. Breed groups consisted of nine purebred breeds (Angus, Braunvieh, Charolais, Gelbvieh, Hereford, Limousin, Pinzgauer, Red Poll, and Simmental), and three composite breeds (MARC I, MARC II, and MARC III). Detection of BIK was by physical examination. If BIK was detected during the preweaning period a score of 100 was assigned and if not the score was 200. Overall average prevalence of BIK was 6.5%. Prevalence was significantly greater in Hereford (22.4%) compared to all other breeds. Pinzgauer and Braunvieh breeds had the lowest incidence rates of 1.3 and 1.8%, respectively. Infections began at approximately 45 d of age and frequency of infections increased until approximately 105 d of age. Variance components for each breed were estimated using REML. Fixed effects included year of birth, age of dam, sex of calf, and birth weight. Calf and dam of the calf (direct and maternal genetic) were random effects. Variance due to maternal permanent environmental effects was not significant. Heritability estimates for the direct effect of the calf ranged from 0.00 to 0.28. Hereford and Angus breeds had the highest heritability estimates, 0.28 and 0.25, respectively. Heritability estimates for the maternal effect were low and ranged from 0.00 to 0.11. Estimates of the direct-maternal genetic correlation were highly variable and ranged from -1.00 to 1.00. Within breed, response to selection to reduce the incidence of BIK in calves would be expected to be slow although breed differences suggest a potential to improve BIK resistance by selection, especially in the Hereford breed.