No abstract

Seven separate experiments were conducted with Hy-Line W-36 hens to determine the ideal ratio of Arg, Ile, Met, Met+Cys, Thr, Trp, and Val relative to Lys for maximal egg mass. The experiments were conducted simultaneously and were each designed as a randomized complete block design with 60 experimental units (each consisting of 1 cage with 2 hens) and 5 dietary treatments. The 35 assay diets were made from a common basal diet (2,987 kcal/kg of ME; 12.3% CP; 4.06% Ca, 0.47% nonphytate P), formulated using corn, soybean meal, and meat and bone meal. The true digestible amino acid contents in the basal diet were determined using the precision-fed assay with adult cecectomized roosters. Crystalline L-Arg (free base), L-Ile, L-Lys.HCl, DL-Met, L-Thr, L-Trp, and L-Val (considered 100% true digestible) were added to the basal diet at the expense of cornstarch to make the respective assayed amino acid first limiting and to yield 5 graded inclusions of the assayed amino acid. Hens were fed the assay diets from 26 to 34 wk of age, with the first 2 wk considered a depletion period. Egg production was recorded daily and egg weight was determined weekly on eggs collected over 48 h; egg mass was calculated as egg production x egg weight. The requirement for each amino acid was determined using the broken-line regression method. Consumption of Arg did not affect egg mass, thus a requirement could not be determined. The true digestible amino acid requirements used to calculate the ideal amino acid ratio for maximum egg mass were 426 mg/d of Ile, 538 mg/d of Lys, 253 mg/d of Met, 506 mg/d of Met+Cys, 414 mg/d of Thr, 120 mg/d of Trp, and 501 mg/d of Val. The ideal amino acid ratio for maximum egg mass was Ile 79%, Met 47%, Met+Cys 94%, Thr 77%, Trp 22%, and Val 93% on a true digestible basis relative to Lys. The ideal Met and Met+Cys ratios were verified in an ensuing identical experiment with 52- to 58-wk-old hens.

Previous studies have reported that intestinal populations of Clostridium perfringens, the causative agent of necrotic enteritis (NE), are correlated with diets high in glycine. To establish a direct causative link, 3 trials were conducted to examine the effect of dietary glycine levels on gut populations of C. perfringens, alpha-toxin production, and NE lesion scores in broiler chickens. In trials 1 and 2, 12 groups of 4 birds were fed 4 different ideal protein-balanced diets formulated to contain 0.75, 1.58, 3.04, or 4.21% glycine from d 14 to 28 of age. In trial 3, 24 groups of 4 birds were given 6 different ideal protein-balanced diets formulated to contain 0.50, 0.75, 1.00, 1.50, 2.00, or 4.00% glycine. All birds were orally challenged with a broth culture of C. perfringens type A on d 1 and between d 14 and 21 of age and killed on d 28. The majority of birds showed clinical signs of NE with 4.16 to 8.33% mortality in the 3 trials. The highest mortality and intestinal lesion scores were observed in chickens receiving 3.04% glycine in trials 1 and 2, and 4.00% glycine in trial 3. Clostridium perfringens populations in the cecum varied quadratically with increasing dietary glycine, with the maximal response seen at 3.30,3.89, and 3.51% dietary glycine in trials 1, 2, and 3, respectively. Numbers of lactobacilli in cecum declined significantly (P < 0.05) with increasing levels of glycine. The results suggest that dietary glycine level has a significant effect on C. perfringens and lactobacilli populations and may be a predisposing factor for NE in broiler chickens.

Two broiler experiments were conducted to assess the relative bioefficacy of liquid DL-Met hydroxy analog-free acid (MHA-FA) and DL-Met (DLM). Exponential regression analysis was used to determine biological efficacy based on body weight, feed conversion, and carcass responses to dietary Met source. In Trial 1, four graded inclusion levels of DLM and liquid MHA-FA (0.06, 0.12, 0.18, and 0.24%) were each added to a basal diet that met the nutrient and energy requirements of broiler chickens, with the exception of Met + Cys. In four additional treatments, diluted DLM (65%) was added at the same supplementation levels as pure DLM and liquid MHA-FA. In the 42-d trial, broilers responded significantly (P < 0.05) to the supplements. Regression analysis revealed that liquid MHA-FA was 68% (weight gain), 67% (feed conversion), 62% (carcass yield), and 64% (breast meat yield) as efficacious as pure DLM on an as-fed basis. Responses to liquid MHA-FA and diluted DLM were very similar at corresponding supplementation levels. Diluted DLM as an internal standard confirmed that exponential regression analysis was a statistically valid technique for determination of the relative efficacy of nutrient sources. In Trial 2, five graded inclusion levels of each DLM (0.040, 0.091, 0.152, 0.222, and 0.303%) and liquid MHA-FA (0.045, 0.102, 0.170, 0.250, and 0.350%) were added to a basal diet limiting in Met + Cys but adequate in all other nutrients and energy. Liquid MHA-FA was 72% (weight gain), 51% (feed conversion), 48% (carcass yield), and 60% (breast yield) as efficacious as DLM on a weight-for-weight basis.

The objective of this experiment was to measure the concentration and digestibility of CP and AA in distillers dried grains with solubles (DDGS) produced from sorghum (S-DDGS) or a blend of sorghum and corn grains (SC-DDGS), and to compare these values with the digestibility of CP and AA in corn-based DDGS (C-DDGS). Eleven growing barrows (initial BW = 44.6 +/- 6.5 kg) were surgically fitted with a T-cannula in the distal ileum and allotted to a Youden square design with 11 diets and 8 periods. One diet contained 66.7% S-DDGS, 1 diet contained 66.7% SC-DDGS, 8 diets contained 66.7% C-DDGS, and 1 diet was N-free. Chromic oxide (0.3%) was used in all diets as an indigestible marker. The direct procedure was used to measure apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of CP and AA in the 10 sources of DDGS. Results of the experiment showed that the AID of Lys was not different among S-DDGS, SC-DDGS, and C-DDGS. The mean SID of CP, Arg, and Lys in C-DDGS were not different from values obtained in S-DDGS and SC-DDGS. The SID of Trp in S-DDGS (72.0%) was greater (P < 0.01) than in C-DDGS (64.9%), but there was no difference between C-DDGS and SC-DDGS (62.4%). The SID of CP and all AA were different among the 8 sources of C-DDGS (P < 0.01). Among the indispensable AA, Lys had the greatest variation and the SID ranged from 55.7 to 68.7%. The concentration of total and digestible AA was highly correlated (r(2)) for Arg (0.88), Ile (0.85), Leu (0.82), Phe (0.84), and Trp (0.84), but reduced r(2) values were observed for Lys (0.66) and Thr (0.39). A low correlation between the concentration and digestibility of AA indicates that it is desirable to develop in vitro procedures to predict digestible AA concentration in DDGS. In conclusion, SID values for CP and Lys in S-DDGS and SC-DDGS are within the range of values obtained in C-DDGS, but for many other AA, SID values in S-DDGS and in SC-DDGS are less than in C-DDGS.