No abstract

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.

Two experiments were conducted to first determine Met then Cys needs of broilers from 3 to 6 wk of age and whether differences existed between slow-feathering (Ross x 308) and fast-feathering (Ross x 3F8) males. A corn-soybean meal diet (20.0% CP; 3,150 kcal ME/kg) with graded levels of Met or Cys was offered. The first experiment had dietary Met levels of 0.32, 0.38, 0.44, and 0.50% with surfeit Cys (0.40%). Broilers from both feathering strains responded similarly to supplemental Met. Although body weight was not responsive, F/G improved through to the highest level of dietary Met (linear, P < 0.05). Chilled carcass weight increased with Met (linear, P < 0.05) paralleling F/G; however, no differences were detected in the amount of associated abdominal fat. Breast fillet yield increased with Met to maximize at 0.48% (quadratic, P < or = 0.009). In a satellite study using the same birds in cages and feeds, N retention at d 29 maximized at 0.46% Met (quadratic, P < 0.05). The second experiment had Cys at 0.32, 0.34, 0.38, and 0.46% with Met fixed at a submarginal level of 0.38%. Increasing dietary Cys had no effect on live performance of slow-feathering birds, whereas weight gain of fast-feathering birds achieved maximum at 0.36% Cys (cubic; P < 0.05) with F/G responding similarly. Chilled carcass (cubic, P < 0.002) and breast fillet weights (cubic, P < 0.001) of fast-feathering birds also increased with Cys to maximize at 0.36%, and the amount of abdominal fat was not influenced by feathering or Cys supplementation. Separate measurement of N retention at d 31 failed to detect a difference in protein utilization attributable to feathering, but an optimum was achieved at 0.40% Cys with both broiler sources. Overall results suggest that the Met requirement for broiler males between 3 and 6 wk of age was independent of feathering and approximated 0.46% (95% of the level of maximal response). Cystine requirements once corrected for submarginal Met status indicated a greater demand by fast- than slow-feathering male broilers corresponding to 0.42 and 0.37%, respectively.

Two experiments were conducted with fast- (Ross x 3F8) and slow- (Ross x 308) feathering broiler males from 0 to 3 wk of age to determine Met and Cys requirements. A corn-soybean meal basal diet was formulated to be deficient in Met and Cys but was adequate in all other nutrients (22.0% CP; 3,050 kcal ME/kg). In experiment 1, diets contained 0.50% dietary Cys with 0.35, 0.40, 0.45, and 0.50% total Met. Feed conversion (FC) of slow- and fast-feathering males improved in a similar manner to 0.50% Met (linear, P < 0.05). Nitrogen retention measured from 20 to 21 d of age optimized at 0.46% Met (quadratic, P < 0.01), regardless of feathering rate. Experiment 2 examined the response to feeding 0.35, 0.40, 0.45, and 0.50% total Cys in diets having total Met at 0.45%. Increasing Cys improved FC that optimized at 0.40% with fast-feathering birds (quadratic, P < 0.01), whereas slow-feathering broilers were not responsive. Nitrogen retention measured from d 20 to 21 did not indicate a difference attributable to feathering but a Cys optimization at 0.43% with both broiler sources. Present experimentation indicates a Met requirement approximating 0.50% is appropriate for broilers 0 to 3 wk of age, regardless of feather rate; however, the estimated Cys requirement for slow-feathering males (0.39%) was less than for fast-feathering (0.44%) males.