|WILLIAMS, KALYANNA - University Of Wisconsin|
|WEIGEL, KENT - University Of Wisconsin|
|ESSER, NANCY - University Of Wisconsin|
|SCHLESSER, H. - University Of Wisconsin|
|HOFFMAN, PATRICK - Vita Plus Corporation|
|SU, H. - China Agricultural University|
|AKINS, MATTHEW - University Of Wisconsin|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2021
Publication Date: 2/15/2022
Publication URL: https://handle.nal.usda.gov/10113/7622041
Citation: Williams, K.T., Weigel, K.A., Coblentz, W.K., Esser, N.M., Schlesser, H., Hoffman, P.C., Ogden, R.K., Su, H., Akins, M.S. 2022. Effect of diet energy level and genomic residual feed intake on bred Holstein dairy heifer growth and feed efficiency. Journal of Dairy Science. 105(3):2201-2214. https://doi.org/10.3168/jds.2020-19982.
Interpretive Summary: Heifer rearing is a large expenditure for dairy producers. Selection for more efficient heifers can potentially decrease feed costs. Residual feed intake (RFI) is the difference between an animal’s actual and expected energy intake and is a tool for selecting animals with greater feed efficiency. This study investigated the interaction between genomic RFI and diet energy density for post-bred Holstein dairy heifers. Post-bred heifers with lower genomic RFI had improved feed efficiency compared to heifers with higher genomic RFI when fed a moderate energy diet diluted with straw; however, no difference between RFI groups was found when heifers were offered a higher energy diet. Feeding the moderate energy diet reduced efficiency, but weight gains were in the ideal range of 0.85 to 0.94 kg/d, while heifers fed the higher energy diet exhibited excessive weight gains (1.15 to1.20 kg/day). This suggests that selection for improved RFI in lactating cows may improve feed efficiency in growing heifers when offered diets with modest energy densities.
Technical Abstract: The objectives of this study were to determine growth performance, feed intake, and feed efficiency of post-bred dairy heifers with different genomic residual feed intakes (RFI) predicted on the basis of projected lactating cow performance when offered diets differing in energy density. Post-bred Holstein heifers (n=128, ages 14-20 months) were blocked by initial bodyweight (high, medium-high, medium-low, and low) with 32 heifers per block. Each weight block was sorted by RFI (high or low) to obtain 2 pens of heifers with high and low genomically predicted RFI within each block (8 heifers/pen). Low RFI heifers were expected to have greater feed efficiency than high RFI heifers. Dietary treatments consisted of a higher-energy control diet based on corn silage and alfalfa haylage [HE; 62.7% total digestible nutrients, 11.8% crude protein, and 45.6% neutral detergent fiber, dry matter (DM) basis], and a lower-energy diet diluted with straw (LE; 57.0% total digestible nutrients, 11.7% crude protein, and 50.1% neutral detergent fiber, DM basis). Each pen within a block was randomly allocated to a dietary treatment to obtain a 2 x 2 factorial arrangement (2 RFI levels and 2 dietary energy levels). Diets were offered in a 120-d trial. Dry matter intake was affected by diet (11.0 vs 10.0 kg/d for HE and LE diets, respectively), but not by RFI or the interaction of RFI and diet. Daily gain was affected by the interaction of RFI and diet, with low RFI heifers gaining more than high RFI heifers when fed LE (0.94 vs 0.85 kg/d), but no difference was observed for RFI groups for the HE diet (1.16 vs 1.19 kg/d). Respective feed efficiencies were improved for low RFI compared to high RFI heifers when fed LE (10.6 vs. 11.8 kg feed DM/kg gain), but no effect of RFI was found for heifers offered the HE diet (9.4 vs. 9.5 kg/kg). No impact of RFI or diet on first lactation performance through 150 DIM was observed. Based on these results, the feed efficiency of heifers having different genomic RFI may be dependent on diet energy level, whereby low RFI heifers utilize a LE diet more efficiently. The higher-fiber LE diet with straw controlled intake and maintained more desirable heifer weight gains. This suggests that selection for improved RFI in lactating cows may improve feed efficiency in growing heifers when offered to meet growth goals of 0.9 to1.0 kg/d.