Three experiments were conducted to determine the effect of reducing NE, by adding dietary fiber in Exp. 1 and 2 and decreasing dietary fat in Exp. 3, of low-CP, crystalline amino acid (CAA)-supplemented diets for finishing pigs on growth performance and carcass characteristics. In Exp. 1 and 2, 64 barrows (Exp. 1) or gilts (Exp. 2) were allotted to four treatments with four replicates of four pigs each. Average initial and final BW were 74 and 117 kg in Exp. 1 and 74 and 102 kg in Exp. 2. The following diets were fed in Exp. 1: 1) corn-soybean meal (C-SBM); 2) low-CP (-3.5%), supplemented with CAA; 3) CAA + rice hulls (CAA+RH; NE equal to Diet 1); and 4) CAA+RH+OIL (NE equal to Diet 2). Experiment 2 was similar to Exp. 1, except RH were replaced with wheat middlings (WM), oil was replaced with dry fat, and the CP was decreased by 3.1% in the low-CP diets. In both experiments, serum urea-N (SUN, corrected for initial SUN by covariance analysis) was higher (P<.10) for pigs fed C-SBM than for pigs fed any other diet. In Exp. 1, barrows fed CAA+RH had lower hot carcass weight, percentage muscle, fat-free lean (FFLEAN), lean gain per day, retained energy (RE) in FFLEAN, and lean:fat ratio than barrows fed C-SBM, along with less FFLEAN than barrows fed CAA+RH+OIL. Barrows fed CAA+RH had smaller longissimus muscle areas than barrows fed any other diet, and barrows fed C-SBM had higher dressing percentage and lower percentage total fat than barrows fed any other diet. Barrows fed C-SBM had higher lean:fat ratio and lower total fat than barrows fed CAA. In Exp. 2, gilts fed CAA+WM+FAT had heavier heart weights than gilts fed C-SBM or CAA (P<.10). In Exp. 3, 702 gilts were allotted to six treatments with nine replicates of 13 gilts each. Average initial and final BW were 70 and 110 kg. Gilts were fed two levels of CP (15.5 or 11.7% plus CAA added to meet an ideal amino acid ratio) and three levels of NE (2,650, 2,617, or 2,584 kcal/kg), resulting in a 2x3 factorial arrangement of treatments. Gilts fed 15.5% CP had higher gain:feed ratio than gilts fed 11.7% CP (P<.01). Longissimus depth was greater for gilts fed 15.5% CP than for gilts fed 11.7% CP and was decreased as NE decreased only in gilts fed 11.7% CP (CP effect, P<.09; NE linear effect, P<.04; CP x NE effect, P<.01). Gilts fed the diet with 2,617 kcal NE had lighter carcasses and less total fat, fat gain per day, RE, and RE as fat regardless of protein level than gilts fed 2,650 or 2,584 kcal NE/kg (NE quadratic, P<.09). Loin color score increased as NE decreased (linear, P<.06), but longissimus fat depth was increased by the lowest level of NE (NE quadratic effect, P<.09). Overall, the reduction of NE in low-CP, CAA-supplemented diets did not affect growth performance and was not an effective means of reducing fat in finishing pigs.

We conducted two experiments to determine the optimum ratio of total sulfur amino acids (TSAA) to Lys for late finishing pigs. In Exp. 1, 50 barrows and 50 gilts were allotted to treatments with three replicates of three or four pigs per replicate in a randomized complete block (RCB) design within a split-plot arrangement of treatments. Sex was the whole plot and TSAA:Lys ratio was the subplot. Average initial and final BW were 77 and 111 kg. Barrows and gilts were fed diets formulated to contain .55 and .65% Lys, respectively. The ratios of TSAA:Lys were .50, .55, .60, .65, and .70. Diets met or exceeded an ideal amino acid pattern for all indispensable amino acids (except TSAA), and all diets were isonitrogenous and equal in electrolyte balance. In Exp. 2, 60 gilts were allotted to five treatments with four replicates of three gilts each in a RCB design. Average initial and final BW were 74 and 110 kg. Gilts were fed diets formulated to contain .65% Lys. The ratios of TSAA:Lys were .35, .425, .50, .575, and .65. In Exp. 1, there were no TSAA:Lys ratio effects (P > .10) for ADG, final BW, percentage muscle, longissimus muscle area, carcass length, percentage fat-free lean (PFFLEAN), lean gain per day (LGD), total fat (TOFAT), percentage TOFAT (PTOFAT), fat gain per day (FGD), lean:fat, retained energy in TOFAT as ether extractable lipid (RE-F), retained energy (RE), or serum urea N (SUN). Feed intake (ADFI) was greater (quadratic, P < .05) for pigs fed .70 TSAA:Lys than for pigs fed any other treatment. Hot carcass weight, psoas muscle weight, 10th rib fat thickness, dressing percentage, fat-free lean (FFLEAN), and retained energy in FFLEAN as protein (RE-P) responded inconsistently to TSAA:Lys ratio, resulting in cubic (P < .09) effects. In Exp. 2, ADFI (linear, P < .08), TOFAT (linear, P < .05), PTOFAT (linear, P < .07), FGD (linear, P < .05), RE-F (linear, P < .05), RE (linear, P < .05), and SUN (linear, P < .02; quadratic, P < .01) decreased as TSAA:Lys ratio increased. Also, gain:feed (GF) (linear, P < .01; quadratic, P < .04), PFFLEAN (linear, P < .04), and lean:fat (linear, P < .04) increased as TSAA:Lys ratio increased. One-slope, broken-line regression models estimated required ratios of TSAA:Lys of .44 (SUN), .40 (ADG), .47 (ADFI), .45 (GF), .45 (FFLEAN), .44 (LGD), .65 (TOFAT), .65 (FGD), .44 (RE-P), .65 (RE-F), .65 (RE), and .57 (lean:fat). Thus, for growth and muscling traits of late finishing pigs, the optimum ratio of TSAA:Lys is less than the current proposed ratio (.65), but to minimize fat accretion, the ratio is .65.

Experiments (Exp.) were conducted with Cornish Rock males (4 to 14 or 15 d of age) to determine the Lys requirement (Exp. 1) and the optimum ratio of TSAA:Lys for chicks fed adequate or inadequate Lys (Exp. 2). In Exp. 1, 180 chicks were allotted on the basis of BW to six treatments with six replications of five chicks each in a completely randomized design (CRD). Average initial and final BW were 73.5 and 415.5 g. The Lys levels fed were: 0.8, 0.9, 1.0, 1.1, 1.2, and 1.3% digestible Lys. In Exp. 2, 240 chicks were allotted on the basis of BW to 12 treatments with four replications of five chicks each in a CRD. Average initial and final BW were 68.5 and 336.3 g. Chicks were fed either 0.82 or 1.0% digestible Lys and within each Lys level, a ratio of TSAA:Lys of: 0.55, 0.63, 0.72, 0.80, 0.88, and 0.96, resulting in a 2 x 6 factorial arrangement of treatments. At the end of each trial, all chicks were weighed and pen feed consumption was measured. In Exp. 1, average daily gain (ADG) and gain:feed (GF) increased (linear, P < 0.01; quadratic, P < 0.02) as dietary Lys increased. A cubic (P < 0.04) effect of Lys for average daily feed intake (ADFI) was observed. One-slope, broken-line regression models estimated Lys requirements of 1.0, 0.9, and 1.1% for ADG, ADFI, and GF, respectively. In Exp. 2, chicks fed 1.0% Lys had higher (P < 0.01) ADG, ADFI, and GF than chicks fed 0.82% Lys. Daily gain, ADFI, and GF increased (linear, P < 0.01; quadratic, P < 0.01) as TSAA:Lys increased. For ADG, ADFI, and GF, one-slope, broken-line regression models estimated required ratios of TSAA:Lys of 0.66, 0.71, and 0.63 for chicks fed 1.0% Lys and 0.66, 0.67, and 0.63 for chicks fed 0.82% Lys. There were no differences (P > 0.05) in the estimated ratios of TSAA:Lys required to maximize ADG, ADFI, and GF for chicks fed 0.82 and 1.0% Lys. Thus, similar ratios of an indispensable amino acid to Lys can be obtained when chicks are fed at or slightly below their Lys requirement.

An experiment was conducted to evaluate feather meal as a source of Val in lactating sow diets. Sows (five farrowing groups; mean parity = 2.34) were allotted to one of two dietary treatments on the basis of ancestry, parity, and weight and date of d 110 of gestation. The treatment diets included 1) corn-soybean meal lactation diet (n = 40) or 2) corn-soybean meal lactation diet with 2.5% feather meal (n = 39). The diets were formulated on an equal Lys basis. All litters were adjusted to 10 pigs within 24 h after farrowing, and all sows weaned at least nine pigs. Sows were bled at 110 d of gestation and at weaning, and serum urea N was determined. Backfat thickness was determined ultrasonically at 110 d of gestation and at weaning. Serum urea N and backfat thickness at d 110 of gestation were used as covariates for serum urea N and backfat thickness at weaning, respectively. The litter response criteria (weaning weight, litter weight gain, and percentage survival) were not affected (P > .10) by feather meal. The sow response criteria (weaning weight, weight loss per day, weaning backfat thickness, change in backfat thickness, ADFI, and days to estrus) were not affected (P > .10) by feather meal. Sows fed feather meal had increased (P < .01) serum urea N and tended (P = .15) to have decreased sow weaning weight. Following the initial analysis of the data, the data set was split into two groups: 1) sows with litters gaining less than 2.17 kg/d (n = 19 and 20 for control and feather meal diets, respectively) and 2) sows with litters gaining more than 2.17 kg/d (n = 21 and 19 for control and feather meal diets, respectively). These two groups were analyzed separately. In sows with litters gaining less than 2.17 kg/d, the litter and sow criteria were not affected (P > .10) by treatment. In sows with litters gaining more than 2.17 kg/d, sow weaning weight was decreased (P < .04) and sow weight loss (P < .02) and serum urea N (P < .01) were increased in sows fed feather meal. Feather meal (as a source of Val) did not improve litter weight gain, but it increased serum urea N.

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