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.