Five experiments were conducted to determine if serum uric acid, serum urea N (SUN), serum ammonia, and the uric acid content of the excreta (UAE) could be used to determine the efficacy of amino acid (AA) utilization in diets for broilers. All experiments were conducted with Ross x Ross 308 or 708 broilers from 0 to 14 or 0 to 18 d posthatching in brooder batteries. Treatments had 6 or 7 replications with at least 6 broilers per replicate pen. All diets were corn and soybean meal-based and formulated to contain 1.0% Ca and 0.45% nonphytate P and to meet or exceed the requirements of all nutrient requirements except total Lys, Met, and Thr (experiment 1) or Met (experiments 2 to 5). Experiment 1 consisted of 2 dietary treatments. Diet 1 was formulated to be deficient in Lys, Thr, and Met and diet 2 was formulated to be adequate in all nutrients. Broilers fed the AA-adequate diet had increased (P<0.01 to 0.03) ADG, ADFI, and G:F compared with broilers fed the AA-deficient diet. Serum uric acid, SUN, serum ammonia, and UAE were not affected (P=0.34 to 0.70) by dietary treatment. In experiments 2 to 5, diets contained 1.35% total Lys, 2 levels of Met (0.50 or 0.76 TSAA:Lys), and without or with Gly supplementation up to 2.32% Gly+Ser. Broilers fed diets containing supplemental Met in experiments 2 to 5 had increased (P=0.01 to 0.03) ADG, ADFI, and G:F. Gain:feed was increased (P=0.01 to 0.07) in broilers fed supplemental Gly. Serum uric acid and SUN were decreased (P<0.01) after a 2-h fast in broilers fed supplemental Met and Gly. Serum uric acid and SUN also were decreased at other times after fasting, but the 2-h fast gave the most consistent response. Uric acid content of the excreta was decreased (P<0.01) in broilers fed supplemental Met. Serum ammonia was decreased (P<0.01 to 0.02) in experiments 2, 3, and 4 at varying times postfeeding but was not affected by diet in experiment 5. The results of this research indicate that serum uric acid, SUN, and UAE concentrations can be used as an indicator of AA utilization in broilers fed AA-adequate and AA-deficient diets.

An experiment was conducted to investigate the effect of dietary Ca level on the efficacy of phytase. A total of 288 male Ross × Ross 708 broilers with initial and final BW of 37 and 705 g, respectively, were used in brooder batteries from 0 to 21 d posthatch. Each treatment had 8 replications with 6 broilers/replicate pen. All diets were corn-soybean meal based and formulated to contain 1.26% total Lys. The treatments were positive control with 0.45% nonphytate P and 1% Ca and a negative control with 0.20% nonphytate P with 0.67, 1.00, or 1.33% Ca fed with or without 500 phytase units of Optiphos (Escherichia coli-derived phytase; JBS United Inc., Sheridan, IN). Increasing Ca from 0.67 to 1.33% linearly decreased (P ≤ 0.003) ADG, ADFI, bone breaking strength, bone weight, tibia ash weight, and percentage tibia ash; however, quadratic effects were found for ADFI, G:F, percentage tibia ash, and mortality (P ≤ 0.09). Phytase supplementation increased (P < 0.001) ADG, ADFI, bone breaking strength, bone weight, ash weight, and percentage tibia ash and decreased (P = 0.054) mortality. The increase in ADG, ADFI, bone weight, ash weight, and percentage tibia ash (P ≤ 0.026) and decrease in mortality (phytase × Ca linear; P = 0.058) from phytase supplementation was greater in broilers fed the higher levels of Ca. Calcium utilization was linearly decreased (P < 0.002) with increasing Ca. Phosphorus digestibility and utilization were increased with increasing levels of Ca (P ≤ 0.002); however, P utilization decreased at 1% Ca and increased at 1.33% (quadratic; P < 0.070). Phytase supplementation increased Ca utilization (P < 0.024), P digestibility (P < 0.001), and P utilization (P < 0.029). However, the increase in P digestibility (phytase × Ca; P < 0.021) was greater at the lower levels of Ca whereas P utilization (phytase × Ca; P < 0.001) was greater at 1.33% Ca with phytase supplementation. The results of this research indicate that dietary Ca level, within the ranges used in this experiment, does not negatively affect the efficacy of phytase.

The purpose of this research was to investigate the effect of Cr as chromium propionate (CrProp) on growth performance, carcass traits, meat quality, and the fatty acid profile of fat from pigs fed no supplemented dietary fat, choice white grease (CWG), or tallow. An experiment was conducted with 108 crossbred Yorkshire gilts assigned in a randomized complete block design based on BW (average initial and final BW were 29 +/- 3 and 109 +/- 7 kg, respectively) and allotted within block to a 2 x 3 factorial arrangement of treatments. The treatment arrangement consisted of 2 levels of Cr supplementation (0 and 200 microg/kg in the form of CrProp) and 3 dietary fat sources (no added fat, CWG, or tallow). Each treatment was replicated 6 times with 3 pigs per replicate pen. The experiment was conducted over time with 3 replicates in each of 2 trials. A 4-phase grower-finisher feeding program was used. Dietary treatments were 1) a corn-soybean meal (C-SBM) diet with no added fat; 2) a C-SBM diet with 4% added tallow; 3) a C-SBM diet with 4% added CWG; 4) diet 1 + 200 microg/kg of Cr as CrProp; and 5) diet 2 + 200 microg/kg of Cr; 6) diet 3 + 200 microg/kg of Cr. Addition of Cr did not affect (P > 0.10) growth performance, but did decrease (P = 0.05) 10th-rib backfat and increase (P = 0.03) percentage of muscle. Gain:feed was increased (P = 0.003) and ADFI was decreased (P = 0.03) by fat addition. Fat addition increased HCW (P = 0.05) and dressing percent (P = 0.03). Average backfat, 9th-rib LM cook loss, and 10th-rib LM drip loss and total loss were decreased (P = 0.02 to 0.04) by tallow. Belly bending on both the teatline and scribe side were increased (P = 0.01 to 0.03) by CWG. Iodine values on belly fat samples were decreased (P = 0.02) by Cr supplementation. In addition, iodine values on belly and loin fat samples were increased (P = 0.001) by CWG. Overall, Cr supplementation decreased backfat and the iodine value of belly fat and increased the percentage of muscle.

The purpose of this investigation was to compare the growth performance of grower pigs fed low-CP, corn-soybean meal (C-SBM) AA-supplemented diets with that of pigs fed a positive control (PC) C-SBM diet with no supplemental Lys. Five experiments were conducted with Yorkshire crossbred pigs, blocked by BW (average initial and final BW were 21 and 41 kg, respectively) and assigned within block to treatment. Each treatment was replicated 4 to 6 times with 4 or 5 pigs per replicate pen. Each experiment lasted 28 d and plasma urea N was determined at the start and end of each experiment. All diets were formulated to contain 0.83% standardized ileal digestible Lys. All the experiments contained PC and negative control (NC) diets. The PC diet contained 18% CP and was supplemented with only DL-Met. The NC diet contained 13% CP and was supplemented with L-Lys, DL-Met, L-Thr, and L-Trp. The NC + Ile + Val diet was supplemented with 0.10% Val + 0.06% Ile. The NC + Ile + Val diet was supplemented with either His (Exp. 1), Cys (Exp. 2), Gly (Exp. 2, 3, and 4), Glu (Exp. 3), Arg (Exp. 4), or combinations of Gly + Arg (Exp. 4 and 5) or Gly + Glu (Exp. 5). Treatment differences were considered significant at P < 0.10. In 3 of the 4 experiments that had PC and NC diets, pigs fed the NC diet had decreased ADG and G:F compared with pigs fed the PC diet. The supplementation of Ile + Val to the NC diet restored ADG in 4 out of 5 experiments. However, G:F was less than in pigs fed the PC diet in 1 experiment and was intermediate between the NC and PC diets in 3 experiments. Pigs fed supplemental Ile + Val + His had decreased G:F compared with pigs fed the PC. Pigs fed supplemental Cys to achieve 50:50 Met:Cys had decreased G:F compared with pigs fed the PC. Pigs fed Ile + Val + 0.224% supplemental Gly had similar ADG, greater ADFI, and decreased G:F compared with pigs fed the PC. Pigs fed Ile + Val + 0.52% supplemental Gly had ADG and G:F similar to that of pigs fed the PC. Pigs fed supplemental Glu had decreased G:F compared with pigs fed the PC. Pigs fed Ile + Val + 0.48% supplemental Arg had decreased G:F compared with pigs fed the PC. Pigs fed the diet supplemented with Gly + Arg had ADG and G:F similar to pigs fed the PC. Pigs fed the low-CP diets had reduced plasma urea N compared with pigs fed PC. The results of these experiments indicate that supplementing Gly or Gly + Arg to a low-CP C-SBM diet with 0.34% Lys, Met, Thr, Trp, Ile, and Val restores growth performance to be similar to that of pigs fed a PC diet with no Lys supplementation.

Research was conducted to determine the level of l-Lys that can be included in corn-soybean meal (C-SBM) diets for broilers before an amino acid (AA) beyond Met, Lys, Thr, or Gly becoming limiting and to determine the order of limiting AA in low CP C-SBM diets. All experiments were conducted with Ross 708 broilers (0 to 18 d of age) in brooder batteries. Treatments contained 7 or 8 replicates with 6 birds per replicate. In all experiments, a control C-SBM diet containing no l-Lys.HCl and a similar diet [positive control (PC) + Gly] with supplemental Gly to provide 2.32% total dietary Gly + Ser were fed. All diets were formulated to contain 1.26% total Lys. All diets with added l-Lys.HCl contained supplemental Gly to provide 2.32% total dietary Gly + Ser. In experiment 1, l-Lys.HCl was added to the diets at 0.02% increments from 0.15 to 0.27%. Compared with the PC + Gly diet, there were no negative effects (P > 0.10) of supplemental Lys on ADG, ADFI, or G:F. In experiment 2, l-Lys.HCl was added to the diets at 0.05% increments from 0.25 to 0.60%. Compared with the PC + Gly diet, ADG and G:F were decreased (P < 0.03) in broilers fed diets containing greater than 0.30% l-Lys.HCl but not (P > 0.10) in the 0.25% l-Lys.HCl diet. In experiment 3, l-Lys.HCl was added to the diets at 0.05% increments from 0.20 to 0.30%. Daily gain was decreased (P < 0.03) in broilers fed 0.30% l-Lys.HCl but not in those fed 0.20 or 0.25% l-Lys.HCl. In experiment 4, the order of limiting AA was determined in a C-SBM diet containing 0.45% L-Lys.HCl. In addition to the PC and PC + Gly diets, diets consisted of a negative control (NC) diet with 0.45% l-Lys.HCl, NC + 0.247% Ile, NC + 0.484% l-Arg.HCl, NC + 0.249% Val, and all possible 2- and l-way combinations of all 3 AA. Compared with the NC diet, addition of Arg and the combination of Arg and the other AA increased ADG and ADFI, indicating that Arg was the limiting AA in this diet. Experiment 5 was conducted in an identical manner to experiment 4 except the diets with the added AA contained the same ratio of corn to soybean meal that is present in a diet with 0.25% l-Lys.HCl. The results of experiment 5 suggest that Arg and Val are equaling limiting in a diet with 0.25% l-Lys.HCl. In summary, 0.25% l-Lys.HCl can be added to C-SBM diets supplemented with Met, Thr, and Gly with no negative effects on growth performance, and Arg and Val are equaling limiting (after Met, Thr, Lys, and Gly) in diets containing 0.25% l-Lys.HCl.