Evaluation of alfalfa leaf meal in wintering beef cow diets. C. M. Zehnder1, A. DiCostanzo*1, J. B. Hall2, and D. B. Brown3, 1University of Minnesota, St. Paul, 2Virginia Tech University, Blacksburg, 3North Central Experiment Station, Grand Rapids, MN.
A study was conducted to evaluate effects of substituting alfalfa leaf
meal (ALM) for soybean meal (SBM) as the protein source when supplementing low quality hay diets. One hundred pregnant, nonlactating Angus cows (631 kg) and 24 pregnant, nonlactating Angus heifers (470 kg) were assigned by BW, calving date and body condition to one of four dietary treatments for a late gestation wintering period. Dietary treatments consisted of supplementing hay-based diets at 100 or 115% of NRC recommended CP intake using either SBM or ALM as the supplemental protein source. Hay for heifers and cows contained 82.1 and 78.4% DM, 7.4 and 6.1% CP, and 52 and 46% TDN, respectively Cows were group fed (two replicate pens/treatment) while heifers were individually fed. The study lasted 70 (early calving) or 85 (late calving) d for cows and ended when the first cow in each replicate calved. Heifers were fed dietary treatments until each heifer calved; for an average of 100 d. Heifers fed ALM consumed less (P < 0.05) hay (5.7 vs 6.6 kg/hd/d for ALM and SBM treatments, respectively) and corn (1.78 vs 1.90 kg/hd/d for ALM and SBM treatments, respectively) DM. Diet DMI was unaffected (P > 0.05) by protein source. Feeding 115% of recommended protein (1.08 vs .94 kg/hd/d) to heifers increased (P < 0.05) precalving rate of gain (−.10 vs .11 kg/hd/d for 100 and 115% CP treatments, respectively). Cows fed ALM had greater (P < 0.05) rates of gain (.53 vs .34 kg/hd/d for ALM and SBM treatments, respectively) when gain was measured 22 d before calving. Once cows calved, weight change was similar (P > 0.05) for each protein source (−.74 kg/hd/d). However, cows fed ALM consumed more (P = 0.054) total DM. Calving traits were not affected by protein source or intake. Wintering heifers or cows on ALM-based supplements had no detrimental effect on performance of heifers or cows, or calving traits. Additional protein may be required by heifers to ensure that they continue gaining weight during late gestation.
Key Words: Alfalfa, Cow, Diet