Whole Soybean Supplementation And Cow Age Class: Effects On Intake, Digestion, Performance, And Reproduction Of Beef Cows

Whole soybean supplementation and cow age class: Effects on intake, digestion, performance, and reproduction of beef cows1
J. P. Banta,*2 D. L. Lalman,† C. R. Krehbiel,† and R. P. Wettemann†
*Department of Animal Science, The Texas A&M University System, Overton 75684 †Department of Animal Science, Oklahoma State University, Stillwater 74078

ABSTRACT: Two experiments were conducted todetermine the effects of whole soybean supplementation on intake, digestion, and performance of beef cows of varying age. Treatments were arranged in a 2 × 3 factorial with 2 supplements and 3 age classes of cows (2-yrold, 3-yr-old, and mature cows). Supplements (DM basis) included 1) 1.36 kg/d of whole raw soybeans, and 2) 1.56 kg/d of a soybean meal/hulls supplement. Supplements were formulated toprovide similar amounts of protein and energy, but a greater fat content with the whole soybeans. Supplements were individually fed on Monday, Tuesday, Thursday, and Saturday mornings. During the treatment period, cows had free choice access to bermudagrass hay [Cynodon dactylon (L.) Pers.; 8.4% CP; 72% NDF; DM basis]. In Exp. 1, 166 springcalving Angus and Angus × Hereford crossbred beef cows wereindividually fed supplements for an average of 80 d during mid to late gestation. During the first 50 d of supplementation, cows fed soybean meal/hulls gained more BW (10 kg; P < 0.001) and body condition (0.18 BCS units; P = 0.004) than cows fed whole soybeans. However, BW change (P = 0.87) and BCS change (P = 0.25) during the 296-d experiment were

not different between supplements. Althoughcalves from cows fed soybean meal/hulls were 2 kg heavier at birth, there was no difference in calf BW at weaning between supplements. Additionally, first service conception rate (68%; P = 0.24) and pregnancy rate (73%; P = 0.21) were not different between supplements. In Exp. 2, 24 cows from Exp. 1 were used to determine the effect of supplement composition on forage intake and digestion; cowsremained on the same supplements, hay, and feeding schedule as Exp. 1. Crude fat digestibility was the only intake or digestibility measurement influenced by supplement composition; fat digestibility was higher for cows fed whole soybeans compared with cows fed the soybean meal/hulls supplement (58.1 vs. 48.8%). Hay intake and DMI averaged 1.63 and 1.92% of BW daily, respectively. Dry matter, NDF, andCP digestibility averaged 54.1, 55.1, and 63.2%, respectively. Compared with supplementation with soybean meal/ hulls, whole soybean supplementation during mid to late gestation resulted in reduced BW weight gain during supplementation, inconsistent effects on reproduction, no effect on calf weaning weight, and no effect on forage intake or digestion.

Key words: beef cow, prepartum, wholesoybean ©2008 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2008. 86:1868–1878 doi:10.2527/jas.2007-0383

INTRODUCTION
Reproduction is one of the most crucial factors in determining profitability of a beef cow/calf enterprise. Thus, nutrition and management strategies to optimize or maximize reproductive efficiency are continually being researched. One nutrition strategythat has received considerable attention in recent years is the potential nutraceutical effect of lipid supplementation. Williams and Stanko (2000) defined a nutraceutical
1 Approved for publication by the director of the Oklahoma Agric. Exp. Stn. This research was supported under project H-2464. 2 Corresponding author: jpbanta@ag.tamu.edu Received June 28, 2007. Accepted April 17, 2008.

as afeedstuff or feed additive having physiological effects outside of its generally accepted role as a nutrient source. Increased lipid intake may improve reproductive efficiency through increased functional capacity of the ovary or alterations in PGF2α synthesis by the uterus or both (Williams and Stanko, 2000). Effects of oilseed and commercial fat supplements on reproduction are inconsistent and...