|Williams, Kalyanna - University Of Wisconsin|
|Weigel, Kent - University Of Wisconsin|
|Esser, Nancy - University Of Wisconsin|
|Schlesser, Heather - University Of Wisconsin|
|Hoffman, Patrick - Vita Plus Corporation|
|Hu, Huawei - University Of Wisconsin|
|Akins, Matthew - University Of Wisconsin|
Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 4/22/2016
Publication Date: 7/19/2016
Citation: Williams, K.T., Weigel, K.A., Coblentz, W.K., Esser, N.M., Schlesser, H., Hoffman, P.C., Hu, H., Akins, M.S. 2016. Effect of diet energy level and genomic residual feed intake on dairy heifer performance. Journal of Dairy Science. ADSA/ASAS Joint Meeting, July 19-23, 2016. Salt Lake City, UT.
Technical Abstract: The objective of this study was to determine the growth, feed intake, and feed efficiency of dairy heifers with different genomically predicted residual feed intakes (RFI), and offered diets differing in energy density. Post-bred Holstein heifers (N=128; ages 14-20 months) were blocked by initial weight (high, medium high, medium-low, and low weight) with 32 heifers per block. Each weight block was sorted by RFI (high, low) to obtain 2 pens of high and 2 pens of low predicted RFI for each block (8 heifers per pen). Dietary treatments were: i) a control diet comprised primarily of corn silage and alfalfa haylage (CON; 62.7% TDN, 11.8% CP, and 45.6% NDF, DM basis); and ii) a similar diet diluted with straw to reduce energy density (STR; 55.9% TDN, 11.7% CP, and 50.1% NDF, DM basis). Each treatment was randomly allocated within each block to obtain a 2 × 2 factorial treatment arrangement of 2 RFI levels and 2 dietary energy levels. Diets were offered in a 120-d feeding trial. Statistical analyses were performed using a MIXED procedure in SAS 9.3 with pen as the experimental unit. Dry matter intake was affected by dietary energy level (11.0 vs 10.0 kg/d for CON and STR, respectively; P<0.01), but not by RFI or the interaction of main effects (P>0.10). Average daily gain was affected by the interaction of RFI and diet, with low RFI heifers having greater gains than high RFI heifers when fed STR (0.94 vs 0.84 kg/d ; P=0.02), but no difference was observed for RFI groups when fed CON (P=0.25). Feed efficiency was better for low RFI than high RFI heifers when fed STR (10.6 vs. 11.8 kg feed/kg gain; P<0.01), but no effect of RFI was found when fed CON (P>0.10). Final body condition score was greater when heifers were offered CON (3.8 vs. 3.5; P=0.02). Diet digestibility was greater for CON (58.4 vs. 50.8% DM; P=0.01), which likely caused the greater intake and gains for heifers fed CON. Based on these results, feed efficiency of heifers having different RFI is dependent on diet energy level with heifers having low RFI using the moderate energy (STR) diet more efficiently. The STR diet reduced intake, and also maintained more desirable heifer weight gains.