Influence of coated whole cottonseed on nutritional value and its potential for supplementation to ruminants

Whole cottonseed {Gossyplum hirsutum) is a valuable source of crude protein (CP) and energy in livestock feeds, but lint fibers on the seed coat make mechanical handling difficult. A commercially available starch coating process has improved mechanical handling of cottonseed. This coating might offer opportunities for incorporating other nutrients or feed additives to supplement grazing ruminants. Thus, four experiments were conducted to determine effects of the coating process on nutritional value and digestibility of whole cottonseed and its potential to act as a carrier. \n \nIn the first experiment, potential minerals and feed additives that could be included in the coating were investigated for cattle fed sorghum (sorghum bicolor) stover supplemented with coated whole cottonseed (CWC). Our results indicated that most of the animal's nutritional needs were either met or exceeded when cottonseed was added to meet CP requirements. However, for a cow in late gestation, P was deficient. Growing cattle and cows in early lactation were borderline for dietary P and needs for additional sulfur (S), iron (Fe), copper (Cu), zinc (Zn), and manganese (Mn) were indicated. These minerals seem feasible for inclusion in the coating. \n \nExperiment two investigated effects of physical additions to the coating on coating integrity. Feed additives investigated included Rumensin® and Ascophyllum nodosum ground to United States Sieve Size (USSS) 100, 40, and 14 (Tasco-14), and a water-soluble extract (Tasco-EX). Particle size played a major role in physically adding material to CWC. The larger the individual particle of A. nodosum Kelp Meal and Tasco-14, the less chance each particle could property incorporate in the coating and adhere to the seed. Rumensin® with a small particle size and Tasco-EX, mixed readily with the cornstarch, and seed coating was successful. \n \nEffects of coating whole cottonseed on dry matter (DM) digestibility, nitrogen (N) balance, and mineral metabolism were investigated in a metabolism trial with wether lambs (BW = 30 kg; SD = 2.3 kg) fed four forage silages. Twenty-four Rambouillet crossbred lambs were fed either corn {Zea mays) silage or 'Brown midrib-100', 'Fame', or 'Cow Vittles M' sorghum silages. Silages were supplemented with CWC, uncoated whole cottonseed (UCWC), or cottonseed meal (CSM) to meet CP requirements. The experiment was a randomized complete block design with a 3 x 4 factorial arrangement of treatments. \n \nDry matter digestibility was greater (P < 0.01) for lambs supplemented with CSM than for the mean of CWC and UCWC. Coating whole cottonseed did not alter DM digestibility compared with UCWC and had no influence on blood serum mineral values. There seemed to be no negative effects of the coating process on DM digestibility or mineral status of the lambs. Apparent N absorption by lambs fed CWC was greater (P < 0.05) than UCWC expressed either as grams per day (P < 0.05) or as a percentage of intake (P < 0.001). Furthermore, at the beginning of the collection period, blood urea N (BUN) did not differ among lambs fed the different CP supplements; however, by the end of the collection period, BUN was greater (P < 0.05) in lambs fed the whole cottonseed than CSM. \n \nFinally, a laboratory in vitro experiment was conducted to evaluate effects of CWC as a carrier to deliver feed additives and whether inclusion altered in vitro DM digestibility (IVDMD) and in vitro volatile fatty acid (VFA) ratios. The IVDMD was greater (P < 0.01) for CWC than for UCWC. Including Tasco-EX either in the coating or in the substrate resulted in greater (P < 0.05) DM digestibility than when monensin was included or compared with CWC alone. \n \nVolatile fatty acid ratios showed that for acetic acid, UCWC was greater (P < 0.02) than for CWC while for butyric acid, concentration was greater (P < 0.02) for CWC than for UCWC. However, these differences were only observed in one of two runs (treatment x run interaction P < 0.001). Acetic acid (mol/I00mol) increased linearly (P < 0.001) over time. Propionic acid concentration (mol/100mol) decreased linearly (P < 0.01) over time but did not differ among treatments. Butync acid concentration (mol/IOOmol) increased initially then decreased (quadratic response; P < 0.001). Total VFA concentration (mmol/L) increased linearly (P < 0.001) over time. Coating of whole cottonseed did not alter in vivo DM digestibility and could enhance protein metabolism. The coating process seems to be a valuable tool as a delivery system for supplementation of feed additives and may be appropriate for supplementation of minerals as well.