Effects of feedbunk restrictions and push-up frequency on the growth performance of Holstein dairy heifers offered a forage-based diet with a limit-feeding strategy

Authors: Coblentz, Wayne; AKINS, MATTHEW - University Of Wisconsin; ESSER, NANCY - University Of Wisconsin

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2020
Publication Date: 7/18/2020
Citation: Coblentz, W.K., Akins, M.S., Esser, N.M. 2020. Effects of feedbunk restrictions and push-up frequency on the growth performance of Holstein dairy heifers offered a forage-based diet with a limit-feeding strategy. Journal of Dairy Science. 103:7000-7008. https://doi.org/10.3168/jds.2020-18152.
DOI: https://doi.org/10.3168/jds.2020-18152

Interpretive Summary: Conceptually, there are 2 feeding strategies for achieving acceptable daily weight gains, while avoiding the over-conditioning that can be particularly problematic for gravid heifers that have reduced energy requirements relative to younger animals. These strategies include: i) dilution of the ad-libitum diet with low-energy forages; or ii) offering a diet of greater nutrient density, but intentionally restricting the amount of DM available for consumption (limit-feeding). Our objectives for this study were to evaluate the effects of feedbunk restriction (100 or 133% of capacity) and feed push-up frequency (1.5 or 3.0-hour intervals) on the growth performance of pregnant Holstein dairy heifers. The frequency of feed push-ups within a limit-feeding management system affected growth performance of heifers only minimally throughout this research trial, and did not interact with feedbunk access. Heifers without feedbunk restriction exhibited greater final bodyweights, but total and daily weight gains differed only numerically between full and restricted access. These results suggest heifers can exhibit acceptable growth performance when offered a high-forage diet with limit-feeding management that includes moderate feedbunk restriction, provided other forms of stress are minimized. Heifers were grouped by weight, such that bodyweights were relatively uniform within each pen, and head-locking feed gates were used, both of which provide some additional protection from adjacent disproportionately large or aggressive heifers. Under these conditions, heifers were largely able to adapt to restricted bunk space, and exhibit acceptable daily weight gains, regardless of feed push-up frequency. Although moderate feedbunk restriction did not greatly affect heifer growth performance in this trial, it should not be inferred that this can be applied blindly, and without strong attention to minimizing other forms of stress within limit-feeding management systems.

Technical Abstract: Conceptually, there are 2 feeding strategies for achieving acceptable daily weight gains, while avoiding the over-conditioning that can be particularly problematic for gravid heifers that have reduced energy requirements relative to younger animals. These strategies include: i) dilution of the ad-libitum diet with low-energy forages; or ii) offering a diet of greater nutrient density, but intentionally restricting the amount of DM available for consumption (limit-feeding). Our objectives for this study were to evaluate the effects of feedbunk restriction and feed push-up frequency on the growth performance of gravid Holstein dairy heifers. A total of 128 gravid Holstein heifers (434 ± 46.7 kg) were enrolled in the trial. Heifers were blocked by weight, and assigned to 1 of 16 identical research pens (4 pens/weight block; 8 heifers/pen), where the mean initial BW (± SD) for the 4 blocks were 491 ± 19.0, 450 ± 16.5, 419 ± 10.6, 374 ± 23.0 kg. Within each block, a 2 × 2 factorial arrangement of treatments was assigned; treatments consisted of feedbunk access [full (FUL) or restricted (RES] and feed push-up frequency [1.5 or 3.0-h intervals]. The RES treatment was applied by covering 2 of the 8 head-locking feed gates in assigned pens with plywood partitions (133% of capacity). A TMR diet comprised of alfalfa haylage (60.5%), corn silage (38.0%), and mineral (1.5%) was offered once daily for 91 d; daily feed allotments were generally consumed entirely within 9 h of feeding. Nutrient intakes were not affected by push-up frequency or the interaction of main effects, but all nutrient intakes were affected by feedbunk access, except for DM and NDF expressed as a percentage of BW (overall mean = 1.93 and 0.80%, respectively). In each case, intakes for FUL were greater than those observed for RES; for DMI, this amounted to a difference of 0.20 kg/d between those main-effect treatments. After 91 d, heifers without feedbunk restriction exhibited greater final BW, but total gain and ADG differed only numerically between FUL and RES. Under the conditions of this trial, heifers were blocked by weight, such that BW were relatively uniform within each pen, and head-locking feed gates were used, both of which provided some additional protection from adjacent aggressive heifers. These results suggest heifers can exhibit acceptable growth performance on high-forage diets in a limit-feeding program that includes moderate feedbunk restriction provided other forms of stress are minimized. A total of 128 gravid Holstein heifers (434 ± 46.7 kg) were enrolled in the trial. Heifers were blocked by weight, and assigned to 1 of 16 identical research pens (4 pens/weight block; 8 heifers/pen), where the mean initial BW (± SD) for the 4 blocks were 491 ± 19.0, 450 ± 16.5, 419 ± 10.6, 374 ± 23.0 kg. Within each block, a 2 × 2 factorial arrangement of treatments was assigned; treatments consisted of feedbunk access [full (FUL) or restricted (RES] and feed push-up frequency [1.5 or 3.0-h intervals]. The RES treatment was applied by covering 2 of the 8 head-locking feed gates in assigned pens with plywood partitions (133% of capacity). A TMR diet comprised of alfalfa haylage (60.5%), corn silage (38.0%), and mineral (1.5%) was offered once daily for 91 d; daily feed allotments were generally consumed entirely within 9 h of feeding. Nutrient intakes were not affected by push-up frequency or the interaction of main effects, but all nutrient intakes were affected by feedbunk access, except for DM and NDF expressed as a percentage of BW (overall mean = 1.93 and 0.80%, respectively). In each case, intakes for FUL were greater than those observed for RES; for DMI, this amounted to a difference of 0.20 kg/d between those main-effect treatments. After 91 d, heifers without feedbunk restriction exhibited greater final BW, but total gain and ADG differed only numerically be