Discriminant Analysis for Predicting Dystocia in Beef Cattle. I. Comparison with Regression Analysis

Abstract

Data from 131 calvings of Chianina crossbred cows (2 to 5 yr old) bred to Chianina bulls were used to compare stepwise multiple regression analysis (RA) and stepwise, two-group discriminant analysis (DA) for predicting dystocia. Variables (21) studied in relation to dystocia included both prebreeding and precalving cow and calf effects. Calving was categorized as either unassisted or assisted without regard to the severity of dystocia. During this study, 30 (22.9%) assisted births occurred. All variables were standardized to a mean of zero and a variance of one before statistical analyses. Models were developed based on precalving variables and with both precalving and postcalving variables with both RA and DA. Average discriminant scores (centroids) were different (P less than .01) between assisted and unassisted cows. Significant precalving DA variables were cow age and precalving pelvic height. This model correctly predicted 26 of 30 (86.7%) of the occurrences of dystocia. Significant precalving RA variables were prebreeding pelvic width and precalving pelvic height. The amount of variation accounted for by these two factors was 31.5%. Calf birth weight, calf chest depth, calf height, precalving pelvic area, cow age and precalving cow weight were selected by DA for use in the combined precalving and postcalving prediction model. Calf birth weight was 58% more important than either pelvic size or cow age. Percentage correctly classified with this model was 87.4. Significant postcalving variables selected by RA in order of importance were prebreeding pelvic width, calf birth weight and calf shoulder width (R2 = .399).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of sire, dam traits, calf traits, and environment on dystocia and subsequent reproduction of two-year-old heifers.

“…Our results showed that selecting the heaviest heifers as yearlings did not reduce the incidence of dystocia at calving. Fagg et al (1975), Short et al (1979), and Morrison et al (1985) reported that precalving cow weight was a significant factor influencing dystocia.…”

“…Calf birth weight significantly increased ( P < .05) as CDS increased and was the most important factor of those evaluated for determining CDS. Calf birth weight has been reported to be the most important factor affecting the incidence and severity of dystocia (Meijering, 1984;Morrison et al, 1985;Johnson et al, 1988).…”

Analysis of body measurements of newborn purebred Belgian Blue calves

“…Johanson and Berger (2003) demonstrated that the odds of dystocia increased by 13% by every kilogram increase of BW. Other factors that have been reported to influence the incidence of dystocia are the calf's body conformation (Morrison et al, 1985) and gender, its sire, the dam's age and pelvic area (Laster, 1974;Bellows and Short, 1978), her weight and body condition (Berry et al, 2007), and finally, some environmental effects such as the ambient temperature (Brinks et al, 1973;Anderson, 1990;Colburn et al, 1997). In addition, inadequate heifer growth and development, abnormalities in hormone profiles during pregnancy and at parturition or abnormal position of the calf at the time of birth will also cause dystocia (Berger et al, 1992;Anderson and Bullock, 2000).…”

Bioeconomic factors of beef heifer maturity to consider when establishing criteria to optimally select and/or retain herd replacements

“…Bellows et al (1971) used ordinary least squares (OLS) regression to quantify the effect of physical size on 4 degrees of dystocia. Morrison et al (1985) and Basarab et al (1993) proposed using a discriminant analysis methodology. While similar to OLS, this method optimizes a different objective function giving the estimates of the coefficients an altered meaning and use.…”