Shaeffer’s formula as an estimator of body weight in slick and wild type-haired Puerto Rican Holstein calves and heifers

Abstract

Recording body weight (BW) regularly is a useful tool for cattle management. However, weighing scales (WS) are not always available on farms, hence the need for BW estimating formulas, which are frequently breed- and/or age-specific. Thus, the current study evaluated the reliability of Shaeffer’s formula (SF), BW=[body length x (thoracic perimeter)²]/300), in nine slick (SLICK) and nine wild type-haired (WT) Holstein calves/heifers. The SF results were compared with those obtained using a WS by the REG and GLIMMIX Procedures (SAS). During weeks 1 to 8, there was a strong association between both weighing methods used on SLICK (R²=0.88; P<0.0001) and WT (R²=0.85; P<0.0001) calves. On average, during this period the SF overestimated BW by 6.39 kg, when compared with the WS (P<0.0001). From 3 to 33 months of age, a strong association was also observed between both weighing methods in the SLICK (R²=0.97; P<0.0001) and WT (R²=0.97; P<0.0001) heifers. Sampling and weighing method interacted (P<0.0001) due to the divergence of the SF and WS curves between 8 and 33 months of age, ranging from 23.20 (P=0.0435) to 80.41 kg (P<0.0001) greater BW by the SF. Shaeffer’s formula turned out to be a feasible and reliable method for BW estimation in the SLICK and WT calves/heifers evaluated in this study, that can be further improved by subtracting the average of overestimated values.