Heart girth measurements to estimate body weight of growing and mature Holstein-Friesian cattle

Excellent nutritional management of replacement dairy heifers is critical to their development and for farms to meet animal development and business finance targets. Small dairy farms in particular may not have the space or resources for large animal weigh scales, and may have to rely on alternative methods of assessing heifer body weight (BW) to monitor growth and to determine nutrient requirements. Weigh tapes are a cheap, widely available alternative to weigh scales for monitoring growth targets. Our objective was to determine the relationship between heart girth (HG, cm) and BW (kg) in growing Holstein-Friesian heifers and to assess the accuracy of a commercially available weight tape. One hundred heifers started the experiment from about 7 wk old and 8,948 individual animal BW and HG measurements were recorded using a weigh crush and tape measure respectively. Animals were fed a range of diets, and measurements continued to the end of second lactation for animals that reached that. Mean data were calculated for every 2 wk of age resulting in 233 paired comparisons of BW (range 51–942 kg) and HG measurements (range 88–232 cm). A quadratic equation was fitted to investigate the relationship between HG and BW: BW = 0.032 × HG² – 3.89 × HG + 154.4; R² = 0.999. The weigh tape (ANImeter, Göbel, Germany) was used to predict BW from known HG, which were
compared against known BW measurements. Predicted values were within 20% of the true BW >99% of the time, with a Lin’s concordance correlation coefficient (Lc) of 0.999. BW were also estimated using the equations of Heinrichs et al. (1992) (BW = 102.71 – 2.876 × HG + 0.02655 × HG²), and Sastry et al., (1982) (W = (L × G²) / 300, where W = BW in lbs, L = animal back length from withers to tail head in inches, and G = HG in inches). These resulted in lower Lc values (0.987 and 0.811 respectively) with our data. It is concluded that the correlation
between HG and BW is sufficiently accurate to allow the use of BW estimated from HG measurements for monitoring heifer growth targets in the absence of weigh scales, and that commercially available tapes are appropriate for this.