Graduate Thesis Or Dissertation

 

Broiler Chicken Meat Quality and Lipid Composition as Influenced by type of Retail Label and Diet Composition Pubblico Deposited

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  • The objectives of the current study were 1) to evaluate the nutritional composition of chicken breast meat labelled as organic and non-organic, and 2) to determine the effect of microalgae and methionine supplementation on meat quality, the incidence of white striping, and muscle pathology in broilers. Two experiments were conducted to assess the nutritional composition of meat. Experiment 1 characterized the lipid and fatty acid (FA) composition of breast meat from broiler chickens labelled as organic or non-organic. Experiment 2 investigated the effects of docosahexaenoic acid- rich (DHA, 22:6 n-3) microalgae product along with methionine (Met) supplementation on growth performance, carcass yield, serum metabolites, breast muscle quality, nutrient content, FA composition, and pathological aspects in broiler chickens. These studies were based on the central hypothesis that the type of production system alters muscle FA composition and feeding Met and n-3 FA-rich diet enhances muscle n-3 FA content while attenuating breast muscle myopathies in broiler birds. In experiment 1, a total of 24 breast meat samples were obtained from local grocery stores. The meat samples originated from two different non-organic (n=6) (Regular 1, Regular 2) or organic (Organic 1, Organic 2) (n=6) labelled chicken meat. Meat samples were analyzed fresh or after 4 week storage at -20oC for moisture and fat content. FA composition and lipid oxidation products were measured as thiobarbituric acid reactive substances (TBARS). Organic 2 had the highest and Regular 2 had the lowest moisture content (P<0.05). However, essential FA such as linolenic acid (18:2 n-6), and α linolenic acid (18:3 n-3) were higher in meat labelled as organic compared to non-organic (P<0.05). Over 1.7 fold increase in total polyunsaturated fatty acids (PUFA) was observed in meat labelled as organic compared to non-organic (P<0.05). When expressed as mg/100 g, organic meat had over 98-130 mg/100g n-3 FA compared to 16-21 mg/100 g in non-organic meat (P<0.05). The TBARS was higher in Organic 2 than Regular 1 (P<0.05). Storage increased TBARS (P<0.05) and had a trend (P=0.09) in reduction in moisture in all of the sampled meat. In conclusion, results from experiment 1 revealed significant differences in FA composition with organic labelled meat providing higher n-3 FA than non-organic meat. However, the high TBARS observed in Organic 2 meat points to the need of natural antioxidants in diet to enhance the freshness and lipid stability of meat from chickens raised and labelled as organic. In experiment 2, one hundred and forty four (n=144) day old Cornish cross chicks were fed a corn-soybean meal-based diet containing 0% microalgae product, (Control), 2% microalgae product (Diet 1), and Diet 1+100% more NRC requirement of Met (Diet 2) for 42 days. All diets were isocaloric and isonitrogenous. The chicks were kept in six pens with eight chicks per each replicate pen. Feed consumption and feed efficiency (feed intake/weight gain) was calculated on day 10, 21 and 42. On day 43, three chicks per each pen (n=18/treatment) were euthanized. The breast muscle was visually scored for muscle striping (0= no striping, 1= moderate, 3= severe) and were subjected to histopathology. Carcass cut up-yield and relative organ weight (breast muscle, thigh muscle, liver, fat pad, heart, gizzard) was determined. Nutrient characterization (total lipid, FA composition, cholesterol, total protein, minerals) of the breast muscle (pectoralis major) was conducted. Other tissues (thigh muscle, liver, fat pad) were subjected to FA analysis. A one-way ANOVA (analysis of variance) was done on the data with diet as the main factor and significance was set at (P<0.05). The incidence of muscle striping was lower (P<0.02) for Control vs Diet 2 and a trend for reduction in white striping was noticed in birds fed Diet 1 vs Control (P=0.09). Histopathology revealed least severe changes in myofiber damage and least inflammation in birds fed Diet 2 (P<0.05). No effect of diet on body weight gain, feed efficiency, breast and thigh muscle, gizzard, and heart tissue yield or serum cholesterol and triacylglycerol was observed (P>0.05). Total n-3 and total long chain (>20C) n-3 FA were highest in the breast muscle of Diet 2 birds (P<0.05). No effect of diet on breast muscle pH, moisture, TBARS, cooking loss, mineral (Ca, P, Mg, Na), or protein content was observed (P>0.05). Drip loss and shear force was highest in Diet 2 (P<0.05). Breast meat color (A*, redness) was reduced (P<0.05) and a trend for reduction in B* (yellowness) was observed in Diet 2 (P=0.07). Total lipid content in breast muscle was lowest in birds fed Diet 1 (P<0.05). In conclusion, the results from Experiment 2 indicates a significant effect of DHA-rich microalgae along with Met supplementation in attenuating white muscle striping and muscle myopathy, while enriching meat with n-3 FA without affecting production performance in broiler birds. In summary, as the current western diets are lacking in n-3 FA and chickens being the major source of animal protein consumed globally, diet management strategies using microalgae and Met could be used in broiler diets to enhance meat quality and n-3 FA content, reduce muscle myopathy and white striping without affecting productivity.
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