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The potential of dietary lipases to improve fat utilization in young birds



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In comparison to the adult birds, young chickens and turkeys have a reduced ability to use dietary fat. It was of interest to investigate the role of lipase in fat malabsorption in young birds. It was hypothesized that fat malabsorption in young chickens and turkeys is due to an insufficiency of pancreatic lipase. It was further hypothesized that fat utilization in young birds can be improved by the use of dietary lipase sources. The first in vitro experiment characterized the activity and stability of mammalian, fungal and bacterial lipase sources when exposed to conditions associated with the proventriculus of young birds. The results of this study demonstrated that bacterial Pseudomonas sp. and Chromobacterium viscosum lipase sources are more stable under conditions that mimic the glandular stomach of young birds. Aspergillus niger lipase also showed a relatively high activity in acidic conditions. Mammalian crude porcine lipase was irreversibly inhibited in these conditions. The second in vitro study tested crude porcine, bacterial Pseudomonas sp. and Chromobacterium viscosum, and fungal Aspergillus niger lipase sources under conditions which approximate the small intestine. It was concluded that Pseudomonas sp. lipase had potential as a supplement in poultry diets. Two in vivo experiments were completed to test the use of Pseudomonas sp. lipase in diets of young broiler chickens and turkeys. The first experiment studied the impact of five levels of enzyme addition (0, 50, 100, 200 and 400 units per gram of diet) in a corn-soybean meal based diet containing 8% tallow and fed to broiler chickens from 0 to 35 days of age. The results indicated that lipase addition has a negative impact on body weight gain, feed efficiency and fat digestibility. Analysis of feeds containing 0 and 400 units per gram of diet revealed that triglycerides had been nearly totally hydrolyzed to free fatty acids and glycerol during feed mixing and/or storage in the enzyme supplemented treatment. The second experiment utilized the same enzyme source at four lower levels (0, 20, 40 and 60 units per gram of diet) in diets for turkey poults under study from 0 to 21 days of age. The production results of this trial were similar but less severe than those seen for chickens. The results of this research do not permit the acceptance or rejection of thesis hypotheses. The unexpected finding that the lipase used in in vivo experiments can hydrolyze triglycerides prior to consumption by birds is undesirable and raises a number of questions. (Abstract shortened by UMI.)





Doctor of Philosophy (Ph.D.)


Animal and Poultry Science


Animal and Poultry Science



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