No abstract

Three energy balance experiments were conducted to determine AMEn of glycerin using broiler chickens of diverse ages. In experiment 1, two dietary treatments were fed from 4 to 11 d of age. Dietary treatments consisted of a control diet (no added glycerin) and a diet containing 6% glycerin (94% control diet + 6% glycerin). Four dietary treatments were provided in experiment 2 (from 17 to 24 d of age) and 3 (from 38 to 45 d of age). Diets in experiment 2 and 3 were 1) control diet (no added glycerin); 2) 3% added glycerin (97% control diet + 3% glycerin); 3) 6% added glycerin (94% control diet + 6% glycerin); and 4) 9% added glycerin (91% control diet + 9% glycerin). Diets in experiment 1 and 2 were identical, but the diet used in experiment 3 had reduced nutrient levels based on bird age. In experiments 2 and 3, broilers were fed 91, 94, 97, and 100% of ad libitum intake so that differences in AMEn consumption were only due to glycerin. A single source of glycerin was used in all experiments. Feed intake, BW, energy intake, energy excretion, nitrogen intake, nitrogen excretion, AMEn, and AMEn intake were determined in all experiments. In experiment 1, AMEn determination utilized the difference approach by subtracting AMEn of the control diet from AMEn of the test diet. In experiments 2 and 3, AMEn intake was regressed against feed intake with the slope estimating AMEn of glycerin. Regression equations were Y = 3,331x -72.59 (P < or = 0.0001) and Y = 3,348.62x -140.18 (P < or = 0.0001) for experiments 2 and 3, respectively. The AMEn of glycerin was determined as 3,621, 3,331, and 3,349 kcal/kg in experiments 1, 2, and 3, respectively. The average AMEn of glycerin across the 3 experiments was 3,434 kcal/kg, which is similar to its gross energy content. These results indicate that AMEn of glycerin is utilized efficiently by broiler chickens.

In commercial practice, formulating diets to adequate amino acid (AA) minimums is critical to optimize live production and meat yield of broiler chickens. The modern broiler has lower feed intake per unit BW gain and also has the potential to accrete more white meat than the commercial broiler of previous decades. Broilers consuming less feed per unit of gain have led to formulating higher AA density diets in commercial production for improved performance and meat yield. This manuscript reviews current literature in dietary AA density. In addition, it provides estimates of consumption and dietary percentages of critical AA needed to optimize growth and meat yield calculated from published research.

A randomized complete block design within a factorial arrangement of treatments was used to evaluate the effect of strain and sex on carcass characteristics, meat quality, and sensory acceptability. Two broiler strains were reared: a commercially available strain (strain A) and a strain currently in the test phase (strain B) that has been genetically selected to maximize breast yield. Broilers were harvested in a pilot scale processing plant using commercial prototype equipment at 42 d of age. Carcasses were deboned at 4 h postmortem. The left half of each breast was evaluated for pH, color, cooking loss, shear force, and proximate analysis. The right side of each breast was used for consumer acceptability testing. Thigh meat was evaluated for proximate composition. No interactions were observed throughout the study. Male broilers had a higher (P < 0.05) live BW, carcass weight, and breast weight and lower (P < 0.05) dressing percentage and breast meat yield when compared with females. Broilers from strain B presented a higher (P < 0.05) breast yield and dressing percentage than those broilers corresponding to the commercially available broiler strain. At 24 h postmortem, female broilers presented a lower ultimate pH and higher Commission internationale de l'éclairage yellowness values (ventral side of the pectoralis major) when compared with male broilers. On average, no differences existed (P > 0.05) among treatments with respect to pH decline, cooking loss, shear values, and proximate composition. In addition, no differences (P > 0.05) existed among breast meat from the different strains with respect to consumer acceptability of appearance, texture, flavor, and overall acceptability, but breast meat from strain B was slightly preferred (P < 0.05) over that of strain A with respect to aroma. However, breast meat from both strains received scores in the range of "like slightly to like moderately." Overall data suggest that all treatments yielded high quality breast and thigh meat and strain cross did not present variability in terms of consumer acceptability.

A randomized complete block design with 3 replications (n=144) was utilized to evaluate the effects of feeding distillers dried grains with solubles (DDGS; 0% control and 8%) on broiler breast and thigh meat quality. Electrical stunning was performed, and broiler carcasses were scalded, picked, and eviscerated using commercial prototype equipment. At 4 h postmortem, carcasses were removed from the chill tank and breast and thigh removal was performed. Color, pH, cooking loss, and shear force values were measured on breasts that were removed from the right side of the carcass. Breasts removed from the left side of the carcass were utilized for sensory testing. Thigh meat was evaluated for TBA reactive substances and fatty acid composition. On average, no differences (P>0.05) existed among the DDGS and control treatment with regards to color (CIE L*, a*, b*), ultimate pH, cooking loss, and shear values. In addition, no differences (P>0.05) existed among treatments regarding the acceptability of texture, but the control treatment was slightly preferred (P<0.05) over the DDGS treatment with respect to flavor and overall acceptability. However, both treatments received scores of "like moderately" on the hedonic scale, and consumers who liked the chicken breasts "moderately" or "very much" (over 50% of the panelists) did not differentiate between the 2 treatments. In addition, in a sensory difference test, consumers could not differentiate (P>0.05) between the control and DDGS treatment. Fatty acid composition varied slightly (P<0.05) between treatments. The DDGS treatment had a greater (P<0.05) percentage of linoleic and total polyunsaturated fatty acids, indicating that it may be slightly more susceptible to oxidation. Overall, data suggest that both feeding treatments yielded high-quality breast and thigh meat with minimal product differences.

Two studies were conducted simultaneously and evaluated the Thr needs of male Ross × Ross 708 broilers. Broilers in the 2 studies were reared under 2 litter conditions: new (NL) vs. used built-up soft wood shavings (BL). Separated by a center aisle, all floor pens from 1 side of the close-sided house contained NL, whereas the opposite side contained BL. Broilers received common diets up to 21 d and then were fed 1 of 6 total dietary Thr levels that ranged from 0.51 to 0.86% total Thr until d 42. At 42 d, birds were processed. A subsample of birds from each experimental unit corresponding to either the 0.51 or 0.72% Thr treatments was taken, immune function was quantified, and lymphoid organs were weighed. Results for live performance and carcass traits are in close agreement with previously reported values in the literature. Quadratic responses were observed for BW gain, feed conversion, and carcass and breast meat absolute and relative weights. Depending on the variable, these responses were maximized from 0.71 to 0.74% Thr when broilers were raised on NL and from 0.73 to 0.78% Thr when broilers were raised on BL. Low Thr (0.51%) was without effect on most immune parameters. However, low Thr decreased relative thymus weight and increased monocyte NO production in built-up and new litter environments, respectively.

The purpose of this study was to understand the needs and relationship of Ile and Val, the most likely candidates to become fourth limiting amino acids in practical broiler formulas. Broiler chicks were fed a diet adequate in all nutrients that served as positive control (PC). A second diet served as negative control (NC), was formulated to resemble the nutrient amounts of the PC, and was supplemented with various crystalline amino acids but not with l-Ile and l-Val, and therefore, no nutrient minimums were given to Ile or Val in the formula. The other treatments fed were as follows: NC plus 0.15% Ile, NC plus 0.15% Val, NC plus 0.075% Ile and 0.075% Val, and NC plus 0.15% Ile and 0.15% Val. Diets were fed in crumble form from placement until 21 d of age. A total of 1,080 Ross x Ross 708 males chicks were randomly allotted into 72 floor pens (15 chicks/pen), and each treatment was replicated 12 times. Individual supplementation with Val, but not Ile, to the NC diet resulted in BW gain of chicks equal to those fed the PC diet (P<0.005). Feed conversion values of chicks supplemented with Val or Ile, or both, resulted in an improvement, but for this variable it would appear that Val and Ile were both equally needed (P<0.001). Responses observed for plasma concentrations of total protein and albumin suggest that Val may be warranted before Ile (P<0.02). Overall responses indicate that Val was the fourth limiting amino acid under these dietary conditions but may reach a point where Ile becomes co-limiting judging by the response observed with feed conversion.

A completely randomized design with 7 replications (n = 7, treatments = 5 with 8 subsamples per treatment) was used to evaluate the effects of feeding various levels of distillers dried grains with solubles (DDGS; 0, 6, 12, 18, and 24%) on broiler breast and thigh meat quality. Broilers were harvested in a pilot scale processing plant with commercial prototype equipment at 42 d of age. The right half of each breast was evaluated for pH, instrumental color, cooking loss, proximate analysis, and tenderness. The left half of each breast was used for consumer acceptability testing. Thigh meat was evaluated for proximate composition, fatty acid composition, and TBA reactive substances. Breast meat from broilers that were fed DDGS had a higher (P < 0.05) pH than those from the control diet. In addition, the 18 and 24% DDGS treatments yielded breast meat with higher (P < 0.05) pH values than the 6% DDGS treatment. No differences existed (P > 0.05) among breast meat from the different treatments with respect to cooking loss, instrumental color, and consumer acceptability, but breast meat from the control (0% DDGS) treatment had slightly lower (P < 0.05) shear force than breast meat from the 18 and 24% DDGS treatments. In addition, no differences (P > 0.05) existed among proximate composition of breast and thigh meat from the control and DDGS treatments. As DDGS concentration increased, there was a linear increase (P < 0.05) in linoleic and polyunsaturated fatty acids, which indicates a greater potential for lipid oxidation. The TBA reactive substances values were greater (P < 0.05) for the 18 and 24% DDGS treatments at d 5 when compared with the control and 6% DDGS treatments, which indicates increased oxidation. Overall, data suggest that all treatments yielded high-quality breast meat and that thigh meat quality was similar among treatments containing 0 to 12% DDGS, but higher inclusion levels led to thigh meat that was more susceptible to oxidation.