|Akins, Matthew - University Of Wisconsin|
|Esser, Nancy - University Of Wisconsin|
|Gelsinger, Sonia - University Of Wisconsin|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2018
Publication Date: 8/17/2018
Citation: Coblentz, W.K., Akins, M.S., Esser, N.M., Ogden, R.K., Gelsinger, S.L. 2018. Effects of Overstocking at the Feedbunk on the Growth Performance and Sorting Characteristics of a Forage-based Diet Offered for Ad-libitum Intake to Replacement Holstein Dairy Heifers. Journal of Dairy Science. 101:7930-7941.
Interpretive Summary: Various forms of overcrowding are not uncommon in heifer-rearing operations. Our objectives for this study were to evaluate the effects of overstocking at the feedbunk (100, 133, 160, or 200% of capacity) on the voluntary intake, growth performance, feedbunk sorting behaviors, displacements from the feedbunk, and hygiene of Holstein heifers. Overstocking at the feedbunk did not affect nutrient intakes, heifer growth performance, sorting behaviors, or hygiene under the management system established for this trial; however, it did increase displacements from the feedbunk. During the first hour after daily feed distribution, heifer displacements from the feedbunk were greater for overstocked pens, and increased linearly with stocking rate, exceeding 70 displacements/hour in pens stocked at 200% of capacity. Furthermore, our results did not suggest that heifers adapted over time by developing a regular feeding order based on relative aggressiveness; displacements from the feedbunk were relatively consistent across the duration of the trial. This suggests that in the absence of other major stressors, overstocking at the feedbunk may play only a limited role in heifer growth performance. However, other forms of stress, such as extreme crowding for lying space in bedded-pack barns, insufficient free-stall numbers, infrequent cleaning of pens, irregular or inconsistent refreshing of bedding, as well as poor feeding management also may interact with competition at the feedbunk to affect heifer growth performance. Given the management system and standards of animal care authorized for this trial, these types of additional stress were largely nonfactors in our results. While overstocking at the feedbunk did not affect heifer growth performance, it should not be inferred that it can be practiced blindly without attention to other critical components of animal welfare.
Technical Abstract: Various forms of overcrowding are common in heifer-rearing operations. Our objectives for this study were to evaluate the effects of overstocking at the feedbunk (100, 133, 160, or 200% of capacity) on the growth performance, feedbunk-sorting behaviors, and hygiene of 128 gravid Holstein heifers (475 ± 55.3 kg) consuming an alfalfa haylage and corn silage diet diluted with processed wheat straw at an inclusion rate of 25.2% (DM basis). In this study, heifers were overstocked only at the feedbunk, and not with respect to available freestalls or pen area. Heifers were blocked by weight, and subsequently assigned to 1 of 16 identical research pens. A total mixed ration (TMR) was distributed at 1000 h daily for 91 d via a drive-through feed alley with heifers allowed access to the feedbunk through head-locking feeding gates. Mean weights for the 4 blocks (32 heifers/block) were 406 ± 14.9, 453 ± 15.3, 493 ± 17.6, and 548 ± 21.9 kg. Generally, nutrient intakes were not affected by stocking rate at the feedbunk; mean intakes of DM, NDF, and TDN across all feedbunk-stocking rates were 10.63, 5.19, and 6.29 kg/d respectively. Overall, the effects of competition at the feedbunk on heifer growth performance were minor, with a collective average daily gain of 1.02 kg/d across all treatments. Only trends for linear increases in total weight gain and BCS were observed with overstocking at the feedbunk. Collectively, overstocked rates also exhibited a trend for better feed:gain than pens stocked at 100% of feedbunk capacity (10.3 vs. 11.0 kg:kg). There was solid evidence that heifers collectively sorted against large (> 19-mm) particles, and also exhibited preference for short (> 1.18-mm, and < 8-mm) and fine (< 1.18-mm) feed particles; however, these responses were not affected by feedbunk-stocking rate. Additionally, heifers sorted against neutral detergent fiber (NDF) as the concentration of NDF remaining in the feedbunk increased during the 24-h period following feeding; conversely, they preferred crude protein (CP) as indicated by a decreasing concentration of this nutrient over time. Heifer hygiene was not affected by competition at the feedbunk. Under the experimental conditions established for this trial, overstocking at the feedbunk did not affect heifer growth performance, but it should not be practiced blindly without attention to other critical components of animal welfare.