|Akins, Matthew - University Of Wisconsin|
Submitted to: Popular Publication
Publication Type: Popular Publication
Publication Acceptance Date: 10/15/2018
Publication Date: 12/18/2018
Citation: Coblentz, W.K., Akins, M.S. 2018. Effects of overstocking at the feedbunk on the growth performance of holstein heifers. Popular Publication. pp. 14-15.
Technical Abstract: Use of corn silage in the diets of pregnant dairy heifers offered for ad-libitum intake can be problematic for several reasons. First, corn silage exceeds the energy requirement for this class of livestock. Secondly, concentrations of structural plant fiber (NDF) are too low, and voluntary intake is not limited adequately through the normal process of gut fill. As a result, heifers often gain excessive weight, which can affect mammary development negatively, as well as first-lactation performance. One remedy for this problem is to dilute total mixed rations (TMR) with low-energy forages, such as straw; however, heifers often exhibit aggressive sorting behaviors that discriminate against these less-desirable forages. Potentially, this can be a problem if smaller or passive animals are prevented from reaching the feedbunk until after substantial sorting has occurred. Sixteen pens of pregnant Holstein dairy heifers (8 heifers/pen) were grouped by weight and offered a diet for 91 days consisting of 54% alfalfa haylage, 21% corn silage, and 25% chopped wheat straw (49.2% NDF, 12.6% CP, 11.1% starch, and 59.0% TDN). All pen groups received the identical diet, but feeding restrictions were put in place so that 0, 2, 3, or 4 head-locking feed gates were covered. This created effective stocking rates at the feedbunk of 100, 133, 160, and 200%, respectively. Displacements from the feedbunk increased with feedbunk stocking rate, but little aggressive activity was observed after the first hour following feed distribution. Heifers sorted aggressively against large feed particles throughout the day, but these behaviors were not affected by overcrowding at the feedbunk. Furthermore, crowding heifers at the feedbunk had no effect on growth performance. It should be noted that other aspects of animal care were maintained at very high standards. These standards included adequate pen area and numbers of freestalls, regular manure removal, frequent push-up of remaining feed, and minimization of the variability for pre-trial bodyweights within each pen. Although heifer growth performance was not affected by feedbunk stocking rate in this trial, it should not be inferred that it can be practiced blindly, without attention to other aspects of animal care.