Abstract
Few studies have been published on the body growth of replacement dairy heifers from Jersey (JER) and Holstein × Gyr (H × G) breeds, as most of them have focused on Holstein (HOL) heifers. In addition, HOL genetics vary significantly across countries. Our goal was to study the body growth curves of 3 distinct genetic groups of heifers (HOL, H × G, and JER) using data from Brazilian commercial dairy herds. Heart girth [to estimate body weight (BW)], hip height (HH), and withers height (WH) were measured. Weights (heifers and cows) and heights (only heifers) were collected from animals in several herds for each genetic group to model and describe the growth rates, mature body weight (MBW), weights, and heights for the recommended age at first breeding (RAFB) and first calving (RAFC). The RAFB values for HOL, H × G, and JER cattle were 15, 18, and 13 mo, respectively. The RAFC values for HOL, H × G, and JER cattle were 24, 27, and 22 mo, respectively. Data were obtained from 18 dairy farms located in 4 Brazilian states and analyzed using nonlinear modeling. Data were collected from 2,266 animals: 878 HOL, 610 H × G, and 778 JER cattle. We observed different body growth patterns in each genetic group. Jersey cattle matured earlier than HOL and H × G, especially for BW and HH. Mature BW of the HOL, H × G, and JER cattle was 681, 607, and 440 kg, respectively. All genetic groups reached the recommended BW at RAFB. However, the genetic groups did not reach the recommended BW at RAFC. Average daily weight gain from weaning to RAFB was 0.84, 0.53, and 0.54 kg/d for HOL, H × G, and JER cattle, respectively. Average daily gain from RAFB to RAFC was 0.53, 0.42, and 0.48 kg/d for HOL, H × G, and JER cattle, respectively. The HH at RAFB and RAFC were 130 and 139 cm for HOL, 130 and 137 cm for H × G, and 114 and 124 cm for JER. Withers height at RAFB and RAFC were 125 and 134 cm, 125 and 134 cm, and 110 and 121 cm for HOL, H × G, and JER cattle, respectively. In general, the rearing practices were adequate to reach the recommended BW at RAFB but below the recommended BW at RAFC for all genetic groups. In addition, each genetic group demonstrated different body growth patterns, especially for BW.
Highlights
Rearing dairy heifers is necessary for replacing culled cows and increasing herd size
We aimed to describe the growth rates (ADG), mature body weight (MBW), body weight (BW), and heights for the recommended age at first breeding (RAFB) and first calving (RAFC) for each genetic group
The final nonlinear models selected for BW growth were Von Bertalanffy, logistic II, and logistic I for HOL, H × G, and JER genetic groups, respectively
Summary
Rearing dairy heifers is necessary for replacing culled cows and increasing herd size. Some studies have been published on the body growth of dairy cattle, especially in Bos taurus cattle, such as HOL (Heinrichs and Hargrove, 1987; Heinrichs and Losinger, 1998; Berry et al, 2005; Duplessis et al, 2015), Jersey (JER), Guernsey (Heinrichs and Hargrove, 1991; Duplessis et al, 2015), Ayrshire, Brown Swiss, and Milking Shorthorn (Heinrichs and Hargrove, 1994; Duplessis et al, 2015) These studies measured the BW and WH. Growth curve data of dairy cattle raised in tropical regions are scarce
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