Multiparameter growth-performance monitoring of Holstein dairy heifers fed on moderate- or high-energy feeding plans from birth to puberty

Abstract

Today, dairy cattle farmers are seeking to optimize expenditure and productivity throughout the lives of their animals by focusing on efficiency at all levels. One strategy for bringing forward the start of a dairy cow's profitability phase is to advance the onset of puberty and reduce the animal's age at their first calving. Thus, one objective of this study was to feed two groups of Holstein dairy heifers the same diet but in different quantities, with the aim of generating a growth differential of at least 200 g/day between the two groups. Thirty-eight heifer calves were followed from birth through puberty using body morphometric measurements and quantitative data collected by automatic feeders, which enabled the monitoring of both feed intake and growth for individual heifers. Routine ultrasonography was used to examine changes in the muscle and adipose tissue compartments, and x-ray tomography was used to monitor bone mineralization and rumen development. At 12 weeks of age, heifers in the optimized feeding (OPT) group had greater cortical bone thickness in the tibia compared with the control (CON) group. At 18 weeks of age, OPT heifers also had more trabecular cancellous bone. In contrast, the ruminal volumes of the heifers in the CON group were greater than those of the OPT heifers at 12 weeks. The OPT heifers had greater indices of general, skeletal, and muscular development at 9 weeks, 6 months, and 12 months. Among the circulating plasma indicators measured in this study, non-esterified fatty acids were highest in the CON calves at 6 and 12 months of age and at the onset of puberty, whereas IGF1 was highest in the OPT calves at all ages. The age at puberty of the OPT calves was 8.4 ± 0.6 months compared with 11.2 ± 1.1 months for the CON calves. The OPT heifers had an average daily weight gain of 1018 g/day from birth to the onset of puberty, which enabled them to achieve increased body fattening and to reach puberty 3 months earlier compared with the CON heifers; the average daily weight gain of the CON heifers was 780 g/day over the same period. Taken together, this study defines new reference values for a multitude of morphometric indicators, thereby enabling precise monitoring of the growth of Holstein heifers from birth to puberty.

Fig 1. CT scan images of a tibia and a rumen.

Photographs showing the different parts of a tibia discriminated by a CT scan with automatic thresholding (A, total bone; B, cortical bone; C, spongy cancellous bone; D, medullary cavity) and of a rumen (E, bolus; F, air) obtained by x-ray CT scanning. The bar represents 10 cm. r, rumen; o, omasum.

Fig 2. Distribution of the ages in months of heifers at puberty onset.

Control (CON) group: white bars, average age at puberty 11.2 ± 1.1 months. Optimized-diet (OPT) group: gray bars, average age at puberty 8.4 ± 0.6 months.

Fig 3. Photographs showing the three locations of ultrasound measurements.

Measurements were made at the buttock at the point of convergence of the facia of the superficial, intermediate, and deep gluteus muscles (A); at the spine of the 4th lumbar vertebra (B); and between the 12th and 13th ribs, at the tip of the ribs with the probe placed vertically (C). The bar represents 1 cm in all photographs. Double white arrows and double white open arrows represent the locations where measurements were performed for fat and muscles, respectively. sk: skin, fb: fat thickness at the buttock, gs: gluteus superior thickness, gi: gluteus intermediate, gd: gluteus deep, fl: fat thickness at the lumbar region, ld: longissimus dorsus thickness, fr: fat thickness at the flat rib region, frm: flat rib muscle thickness.