|Williams, K. - University Of Wisconsin|
|Weigel, K. - University Of Wisconsin|
|Esser, N. - University Of Wisconsin|
|Hoffman, P. - Vita Plus Corporation|
|Su, H. - University Of Wisconsin|
|Akins, M. - University Of Wisconsin|
Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/6/2017
Publication Date: 6/25/2017
Citation: Williams, K., Weigel, K., Coblentz, W.K., Esser, N., Hoffman, P., Su, H., Akins, M. 2017. Effect of diet energy level and genomic residual feed intake on pre-bred dairy heifer feed intake and growth. Journal of Dairy Science. 100 (suppl. 2): 271.
Technical Abstract: The objective of this study was to determine the growth, feed intake, and feed efficiency of pre-bred dairy heifers with different predicted genomic residual feed intakes as lactating cows (RFI), and offered diets with different energy levels. Pre-bred heifers (128, ages 4-9 months) were blocked by initial weight (high, 286 kg; medium-high, 241 kg; medium-low, 205 kg; and low, 168 kg) with 32 heifers per block. Each weight block was sorted by RFI to obtain 2 pens of high (HRFI) and 2 pens of low RFI (LRFI) for each block with 8 heifers per pen. Animals with LRFI might be expected to have greater feed efficiency than HRFI animals. Dietary treatments were a high energy diet (HiE; 66.6% TDN, 14.0% CP, and 36.3% NDF, DM basis) and a low energy diet (LoE; 63.8% TDN, 13.5% CP, and 41.2% NDF, DM basis). Each treatment was randomly allocated to pens to obtain a 2x2 factorial arrangement of treatments (2 RFI levels and 2 diet energy levels). Diets were offered in a 120 day feeding trial. Statistical analyses were performed using a MIXED procedure in SAS 9.3 with pen as experimental unit. Dry matter intake was not affected by diet (7.38 vs. 7.83 kg DM for HiE and LoE, respectively; P=0.14), or by RFI (7.40 vs. 7.81 kg DM for HRFI and LRFI, respectively; P=0.17) or by their interaction (P=0.66). Average daily gain was affected by diet with heifers fed the HiE diet having greater gains than the LoE diet (1.14 vs. 0.97 kg/d; P<0.01). Residual feed intake also affected daily gain with LRFI heifers having greater gains than HRFI (1.09 vs. 1.02 kg/d; P=0.03), but the interaction of RFI and diet was not significant (P>0.10). Feed efficiency was improved for the HiE diet (6.44 vs. 8.02 kg DMI/kg gain; P<0.01), but was not affected by RFI (P=0.48) or the interaction of diet energy and RFI (P=0.62). Overall, feed efficiency of pre-breeding heifers was not dependent on RFI with LRFI heifers having improved weight gain likely due to a numerical increase in intake. Feed efficiency was lower for the LoE diet, but resulted in more optimal weight gains for pre-breeding heifers than feeding a higher energy diet ad-libitum.