Effects of diet mix time and ractopamine hydrochloride on finishing pig growth and carcass performance.

Two experiments were completed to determine the effects of diet mix uniformity and ractopamine HCl on finishing pig performance. In Exp. 1, a total of 200 pigs (BW = 90 kg) were used in a 33-d growth assay arranged in a randomized complete block design with 5 pigs/pen and 8 pens/treatment. Treatments were a corn-soybean meal-based control diet mixed for 360 s or the mixed control diet with 10 mg/kg ractopamine added before additional mixing for 0, 30, 120, or 360 s. Chromium was added to the diet and analyzed to determine mix uniformity of the ractopamine. Therefore, this experiment was designed to determine the effects of nutrient utilization from a thoroughly mixed diet with a potentially nonuniform distribution of ractopamine. Pigs fed diets with ractopamine had greater (P < 0.05) ADG, G:F, final BW, HCW, dressing percentage, loin depth, and percentage carcass lean with lower (P = 0.005) 10th rib backfat thickness. Increasing mix time from 0 to 360 s decreased (quadratic, P = 0.001) CV for Cr from 67 to 12% but had no effect on the response to ractopamine for any growth or carcass measurements. In Exp. 2, a total of 160 pigs (BW = 93 kg) were used in a 27-d growth assay arranged in a completely randomized design with 2 pigs/pen and 16 pens/treatment. Treatments were a corn-soybean meal-based control diet mixed for 360 s or the control diet with 10 mg/kg ractopamine mixed for 0, 30, 120, or 360 s. Diet mix uniformity was determined by measuring Cr and using Quantab Cl titrators (low range 0.005 to 0.1% as NaCl; Environmental Test Systems Inc., Elkhart, IN) to measure the concentration of salt. This experiment was designed to determine the combined effects of potentially nonuniform distribution of both nutrients and ractopamine. The use of ractopamine increased (P < 0.05) ADG, G:F, final BW, HCW, dressing percentage, percentage lean, and loin depth. Increasing mix times from 0 to 360 s decreased (quadratic, P = 0.050) CV for salt and Cr from 51 to 12% and 51 to 15%, respectively, with no effect on ADG, ADFI, final BW CV, HCW, dressing percentage, backfat thickness, loin depth, or percentage carcass lean; however, G:F tended to increase (linear, P = 0.07) as mix time increased from 0 to 360 s. In conclusion, increasing mix time of diets from 0 to 360 s did not affect the response of finishing pigs to ractopamine

Enzyme supplementation and particle size of wheat in diets for nursery and finishing pigs.

Three experiments were conducted to determine the effects of enzyme supplementation and particle size of wheat-based diets on growth performance and nutrient digestibility in nursery and finishing pigs. In Exp. 1, 180 weaned pigs (5.7 kg and 21 d of age) were fed diets in a 35-d growth assay without or with a Trichoderma longibrachiatium enzyme product (4,000 units of xylanase activity per gram of product) and with wheat ground to mean particle sizes of 1,300, 600, or 400 microm. Enzyme supplementation had no effect on ADG or gain/feed (P > 0.32), but there was a trend (P < 0.10) for greater digestibility of DM (d 6) in enzyme-supplemented diets. A particle size of 600 microm supported the greatest overall gain/feed (quadratic effect, P < 0.01). An interaction of enzyme supplementation with particle size occurred; gain/feed was improved (P < 0.01) with enzyme supplementation at the coarse (1,300 microm) particle size but not when the wheat was ground to 600 or 400 microm. In Exp. 2, 160 finishing pigs (67 kg) were fed a diet without or with the same enzyme used in Exp. 1 and wheat ground to 1,300 or 600 microm. No interactions occurred between enzyme supplementation and particle size of the wheat (P > 0.15). However, there were trends for greater gain/feed (P < 0.10) during the 67- to 93-kg phase of the experiment and for greater digestibility of DM (P < 0.10) and N (P < 0.07) with enzyme supplementation. When particle size was reduced from 1,300 to 600 microm, gain/feed was improved (P < 0.03) for the 93- to 114-kg phase of the growth assay, and digestibilities of DM (P < 0.02) and N (P < 0.04) were greater. In Exp. 3, 160 finishing pigs (63 kg) were given diets without or with the enzyme product and wheat ground to 600 or 400 microm. Enzyme supplementation improved ADG (P < 0.04) in the 90- to 115-kg phase but otherwise did not affect growth performance, carcass measurements, or stomach lesions. A particle size of 400 microm increased overall gain/feed (P < 0.04), digestibilities of DM and N (P < 0.01), and development of stomach lesions (P < 0.01). In conclusion, pigs did not benefit consistently from enzyme supplementation. However, wheat particle sizes of 600 and 400 microm supported the best overall performance in nursery and finishing pigs, respectively.