Soybean Hull Supplementation to Pasture-Based Beef Cattle Finishing Diets

In the midsouthern United States, forages exist as the major nutrient source for grazing beef cattle. A large forage base allows this region to produce and market many feeder calves to backgrounding and feedlot operations. The utilization of forage resources stands as a high priority to cattle producers. Supplementation of highly digestible fiber feedstuffs can be used to enhance animal performance, to take advantage of forage resources, and to extend forages by increasing stocking rates or increasing hay production. The development of forage based beef cattle finishing systems may be supported by high-fiber energy supplementation strategies. The availability of feeder cattle and an abundance of forage resources in the midsouth increase the feasibility for producers to develop an interest in forage fed beef, niche market opportunities. The objectives of the experiments conducted were: 1) to evaluate two forage based grazing systems designed to produce cattle finished to a traditional endpoint; 2) to determine the effects of soybean hull supplementation on forage intake and site and extent of nutrient digestion. Experiment one was replicated over two yr and consisted of 42 crossbred beef calves (305.3 ± 12.8 kg) of moderate frame size used to compare two forage-based beef cattle finishing systems. The calves were weaned each yr approximately twenty d prior to stratification by gender and weight, and allotment to each system. The cattle received no growth promoting implants or feed additives during the experiment. The two systems were: 1) cattle grazed on cool season perennial grass pastures and wintered on annual grass pastures (CSP+A) and 2) cattle grazed on cool season perennial grass pastures and wintered on stockpiled cool season perennial grass pastures with daily supplementation of pelleted soybean hulls at 1.0% BW on a dry matter basis (CSP+SH). There were three v and four replications for CSP+A and CSP+SH, respectively. Each replication consisted of three steers and three heifers. Supplemented cattle were fed in bunks and all animals had free choice trace mineralized salt, access to fresh water, and sun shelter. The experimental grazing yr consisted of three grazing periods: fall, winter, and spring. Both systems were stocked at a rate of 4.9 calves/ha for each season with the exception of a winter stocking rate of 2.5 calves/ha for CSP+SH. The fall period consisted of both systems grazing cool season perennial grass paddocks. CSP+A cattle were then rotated to annual grass pastures while CSP+SH cattle were moved to stockpiled cool season perennial grass paddocks for the winter period. Hay harvested from CSP+SH experimental paddocks was fed to both systems when adequate winter forage was not available. Rotation back to the original fall paddocks occurred at the beginning of the spring period. The spring period lasted until the cattle were harvested. The mean of two consecutive d weights was recorded for the initiation of the experiment, each grazing period, and the end of the experiment. Corresponding to these weigh periods, ribeye area (REA) and back fat (BF) estimations were determined using real-time ultrasound. Twenty-eight d interval weights were recorded on cattle not withheld from forage or water, yet before daily supplementation to determine average daily gains (ADG) and to adjust soybean hull supplementation. Clipped forage samples were taken corresponding to every weigh period from five random locations (0.25 m x 2.54 cm) in each presently grazed paddock. Samples were used to determine forage quantity and quality. Masticated rumen samples were taken at the beginning of each grazing period from six fistulated steers equipped with rumen cannulas to determine diet quality selection. After 306 and 284 d (yr one and two, respectively) cattle were harvested and carcass data collected. The vi CSP+SH cattle gained 0.58 kg/d more (P 0.35) by supplementation. Crude protein intake was 107 g/d greater (P 0.17) and ruminal ammonia nitrogen concentration was decreased (P 0.60). Supplementation of soybean hulls at a rate of 0.70% BW to cattle consuming fresh tall fescue decreased forage consumption. Supplementation did not change the percentage of ruminal dry matter disappearance, but increased quantities of total tract nutrient disappearance. Also, the rumen conditions were maintained to support cellulolytic microbes and more N was converted to microbial crude protein with supplementation. The supplementation of soybean hulls in grazed forage diets improves overall diet digestibility, extends forage resources, improves animal performance, and provides an opportunity to produce a quality forage fed beef product.