Heritability of scrotal circumference adjusted and unadjusted for body weight in nellore bulls, using univariate and bivariate animal models

• Published in: Theriogenology 1998-05, Vol.49 (7), p.1389-1396
• Main Authors: Quirino, C.R., Bergmann, JAG
• Format: Article
• Language: English
• Subjects: Age Factors; ANIMAL MODELS; Animals; BEEF CATTLE; BODY MEASUREMENTS; BODY WEIGHT; BOVIN DE BOUCHERIE; Brazil; BREEDS (ANIMALS); BULLS; Cattle - anatomy & histology; Cattle - genetics; CORRELACION GENETICA; CORRELATION GENETIQUE; DIRECT SIRE COMPARISONS; ESCROTO; EVALUACION DE SEMENTALES; EVALUATION GENETIQUE DES PERES; GANADO DE CARNE; GENETIC CORRELATION; genetic parameters; HEREDABILIDAD; HERITABILITE; HERITABILITY; Male; MEDICION DEL CUERPO; MENSURATION CORPORELLE; MODELE ANIMAL; MODELOS ANIMALES; Models, Biological; PESO CORPORAL; POIDS CORPOREL; RACE (ANIMAL); RAZAS (ANIMALES); scrotal circumference; SCROTUM; Scrotum - anatomy & histology; SIRE EVALUATION; TAUREAU; TORO; VARIANCE COMPONENTS; ZEBU BREEDS; Zebu cattle
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/S0093-691X(98)00085-5

Mixed model methodology under univariate and bivariate animal models was used to estimate genetic parameters of scrotal circumference (SC) unadjusted (h U 2) and adjusted (h A 2) for body weight, from field data on 875 Nellore males sired by 80 bulls. The models included random effect of animal, the fixed effects of age of dam, year of birth, and month and year of measurement, and the covariate age of the animal, in addition, one of the models also included the covariate body weight. Using univariate models, SC estimates of h U 2 were 0.18, 0.65, 0.77 and 0.60, and of h A 2 they were 0.15, 0.60, 0.71 and 0.50, at 9, 12, 18 and 24 mo of age, respectively. Bivariate estimates of heritability ranged from 0.18 to 0.77 for h U 2, and from 0.13 to 0.70 for h A 2. The results suggest that it would be better to consider unadjusted SC rather than adjusted SC in selection programs. Bivariate body weight estimates of heritability ranged from 0.15 to 0.45. Genetic correlations between SC and body weight ranged from 0.58 to 0.71 when body weight was not included in the model, and from 0.33 to 0.64 when body weight was included. These results suggest that simultaneous selection for body weight and SC is possible in Nellore cattle.