Factors Influencing Calving Difficulty in Beef Heifers

Abstract

Records of 547, 2-yr-old heifers of three breed groups were used to evaluate the relative influence of dam's body and pelvic measurements, calf birth weight, sire birth weight and some relative measures (ratios) of calf birth weight and dam weight at calving on calving difficulty. The data were analyzed by regression and least squares procedures. The full model explained 32.5% of the variation in calving difficulty score. The linear effect of calf birth weight was the most important variable, accounting for 17.8% reduction in the coefficient of determination, and together with dam weight at calving and the quadratic effect of calf birth weight it accounted for 92% for all the variation explained by the full model. Dam weight at calving was negatively related to calving difficulty. Breed, year and sex of calf did not influence calving difficulty score, except when the calf birth weight or dam weight or both were excluded from the model. When calf birth weight was expressed as a ratio of the dam's weight at calving, hip height and pelvic measurements, the total model explained 34.8% of the variation in calving difficulty score. The ratio of calf birth weight to dam weight was the most important variable (R2 = 26.8%). Ratios of calf to dam weight at calving and calf weight to the vertical pelvic diameter (R2 = 29.3%) were the only significant factors when the effects of calf birth weight and dam weight were removed from the model. Pelvic measurements, on their own, did not influence calving difficulty score in this study (P greater than .1), but small pelvic dimensions tended to be associated with higher calving difficulty scores.

A comparison of reproductive and growth traits of horned and polled cattle in three synthetic beef lines

“…Pregnancy, calving and weaning rates, were based on the number of females bred, expressed as a percentage. Dystocia was scored on a scale of 0 to 5, where 0 = no difficulty, 1 = light pull, 2 = hard pull, 3 = forceps used, 4 = veterinary assistance and 5 = Caesarian section (Naazie et al 1990 ). The five-point condition scoring system developed by the east of Scotland College of Agriculture was followed (Lowman et al 1986).…”

Genetic parameters for weight, weight adjusted for body condition score, height, and body condition score in beef cows1,2

“…Data from nine purebred and three generations (F 1 , F 2 , and F 3 ) of composite populations from the Germplasm Utilization program at MARC yielded estimates of genetic correlations of 0.74, 0.48, and 0.00 between weight and height, weight and condition score, and height and condition score of 2-yr-old cows, and 0.47, 0.56, and −0.14 at 5 yr of age (Gregory et al, 1995). Least squares estimates of phenotypic correlations between cow weight and height have been reported to be from 0.06 to 0.89 (Brown et al, 1956a,b,c;Nelsen et al, 1985;Thompson et al, 1983;Naazie et al, 1989;Choy et al, 1996Choy et al, , 1998a, but most estimates were intermediate to high, averaging 0.59, the same estimate obtained in the present study. Estimates of genetic correlations have been relatively high (0.68 to 0.79), as reported by Choy et al (1996Choy et al ( , 1998a.…”

Effects of early versus late spring calving on beef cow-calf productivity

“…Pregnancy rate, calving rate and distribution, and weaning rate were based on the number of cows exposed to breeding. Calving difficulty was scored from 0 to 5 where, 0 = no assistance, and the assisted scores were, 1 = light pull, 2 = hard pull, 3 = calf puller used, 4 = veterinary assistance and 5 = Caesarean section (Naazie et al 1989). The Canadian five score system was used to evaluate the BCS.…”