Aspects of Lipid Utilization in the Neonatal Chicken

Mutayoba, Salome Kokushubila (1993) Aspects of Lipid Utilization in the Neonatal Chicken. PhD thesis, University of Glasgow.

Abstract

Lipids play an important role throughout the life of the birds but particularly during embryonic and neonatal periods. Following hatching the lipids are derived from two sources, the residual yolk sac material and the diet. In modern broiler production much emphasis is placed upon the diet, thus providing the chick with a high lipid oriented environment very early in the post-hatch period. This is normally aimed at enhancing rapid growth in birds. However, a combination of exogenous and endogenous lipid sources to the chick during this period is likely to exert enormous pressure on the physiological processes most of which are still in the developmental stage. Thus, the main objectives of the present studies were to investigate the relative roles of the yolk lipids versus dietary lipids during the neonatal period on lipid and fatty acid compositional changes of the residual yolk sac material, liver, gall bladder bile and gastrointestinal tract. In addition the effects of exogenous and endogenous dietary lipids on the establishment of the gastrointestinal tract microflora, lipid and fatty acid digestibilities were studied. During the study the effect of post-hatching age on all the mentioned parameters was also assessed. Three dietary treatments were used. Diet 1 was a complete diet from a commercial company or a diet compounded using a commercially available fat source. This diet contained high levels of unsaturated fatty acids and free fatty acid. Diet 2 was based on tallow oil as the major fat source and thus contained high levels of saturated fatty acids. Diet 3 was based on soyabean oil as the major fat source and contained high levels of unsaturated fatty acids. The diets were formulated in such a way as to provide adequate levels of other nutrients. Standard procedures for chick rearing and feeding were followed. Established analytical methods for lipid and fatty acids were used throughout. Experiment 1 involved a study on the effects of post-hatching age and dietary fat sources on the lipid and fatty acid compositional changes of the residual yolk sac material, liver and gall bladder bile during the first 12 post-hatch days. The results obtained showed that both the weight and lipid compositions of the residual yolk sac material and the liver were significantly affected by post-hatching age. The changes included significant decline in the weight of residual yolk sac material from about 11% of the total weight of the chick immediately post-hatch to less than 0.1 percent of the chick's body weight by day 12 post-hatch. Between day 1 to 9 post-hatch the rate of decline was higher in chicks receiving the commercial diet and the tallow oil based diet, but no further differences were observed after day 9. Significant increases in the proportion of cholesterol esters and decreases in triglyceride and phospholipid fractions with post-hatching age were observed for all dietary treatments. Dietary effects were also noted, for cholesterol ester and triglyceride, proportions being significantly higher and lower, respectively, in chicks receiving the tallow oil based diet. In common with the residual yolk sac material, the proportion of liver tissue to the chick's body weight was significantly affected by age, particularly between days 1 and 3 post-hatch during which a 50 percent increase was observed in all dietary treatments. After day 3 post-hatch increases were observed only in chicks receiving the commercial diet and the soyabean oil based diet, whilst, decreases occurred in chicks receiving the tallow oil based diet. Liver lipid compositional changes with post-hatching age were characterised by significant decreases of cholesterol esters from 77 to less than 2 percent of total lipid present on day 1 and day 12 post-hatch, respectively. Concomitantly there were significant increases in the triglyceride and phospholipid proportions, whilst, minor changes occurred in the other lipid fractions. Dietary effects on cholesterol esters and triglyceride levels were also observed, levels being higher and lower in chicks receiving the soyabean oil based diet. The lipid composition of the gall bladder bile was significantly affected by post-hatching age in particular the increase in triglyceride levels. In all the tissues studied the effect of age and dietary fat source on fatty acid composition was relatively small. In experiment 2, the influences of the post-hatching age and dietary fat source on the lipid and fatty acid compositional changes in relation to lipid digestion and absorption within the different sections of the gastrointestinal tract were studied. The major feature observed throughout the 12 day post-hatch period was the high phospholipid levels (more than 60 percent of total lipid present) within the duodenal contents irrespective of the dietary treatment. At day 3 post-hatch and in all subsequent days high proportions of triglyceride and free fatty acid were observed in GIT sections beyond the duodenum. It was clear from this study that most of the processes of lipid digestion occurred beyond the duodenum. The proportion of free fatty acid remained high along the remaining sections of the gastrointestinal tract in all the dietary treatments, particularly in chicks receiving the tallow oil based diet.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: R C Noble
• Keywords: Animal sciences
• Date of Award: 1993
• Depositing User: Enlighten Team
• Unique ID: glathesis:1993-75280
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 21:21
• Last Modified: 19 Nov 2019 21:21
• URI: https://theses.gla.ac.uk/id/eprint/75280