Fit or flabby: Can we simplify the body condition scoring method?
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Date
2023-05
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The Ohio State University
Abstract
Body condition scoring (BCS) on a 1 - 5 scale is a common method of assessing dairy cow body fat reserves, serving as a management tool to consistently identify patterns and address herd nutrition, reproduction, and health. However, the efficacy of scoring in different BCS point increments has not been well described. Our objective was to evaluate the variation in BCS based on scoring in half- (HALF) or quarter-point (QRT) increments and to evaluate the accuracy of categorically assessing cows as thin, ideal, or fat (CAT) for current lactation stage compared to assigning traditional BCS. Our hypothesis was that HALF scoring would not increase variation of managerial value. We further hypothesized that CAT score would be interpretively similar to traditional BCS. Jersey cows (n = 20) balanced by lactation stage were scored by undergraduate students (n = 14) of varying experience for 6 weeks. Prior to trial initiation, all participants received BCS training and were provided an on-farm scoring guide. Each week, participants assigned QRT, HALF, and CAT scores. Statistical analysis included a SAS mixed-model approach (fixed effects: scoring method, lactation stage, week, scorer experience; random effects: scorer, cow) with repeated week as appropriate; residuals were regressed against predicted BCS from HALF, centered to the mean. CAT method was on a 2 - 4 scale; QRT and HALF were on a 1 - 5 scale. Regression of the residuals indicated a mean bias (P < 0.01) where HALF underestimates herd BCS by 0.018 and a slope bias (P < 0.01) where HALF increased by 0.110 points compared to QRT for every whole point BCS gain observed. Scoring method influenced mean score (P < 0.01) where CAT was lower than QRT or HALF by 0.055. Also of note, novice scorers estimated cows 0.24 points lower than more experienced scorers (P < 0.01). Variance of QRT and HALF were not different (P > 0.10). These data indicate that HALF could be equally accurate as QRT, while potentially decreasing producer effort and time to score. Further work is needed to support these results on farms with different breeds and management styles and with scorers of different ages and backgrounds.
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Keywords
nutrition, cow grouping, transition, dairy, body condition score