Author:

Keywords:

broiler chicken, macronutrient ratio, intermediary metabolism, endocrine functioning, dietary-protein, growth-hormone, deiodinase activities, hepatic lipogenesis, energy-metabolism, gene-expression, nitrogen intake, plasma-hormone, organ weights, growing fowl, Science & Technology, Life Sciences & Biomedicine, Agriculture, Dairy & Animal Science, Agriculture, DIETARY-PROTEIN, GROWTH-HORMONE, DEIODINASE ACTIVITIES, HEPATIC LIPOGENESIS, ENERGY-METABOLISM, GENE-EXPRESSION, NITROGEN INTAKE, PLASMA-HORMONE, ORGAN WEIGHTS, GROWING FOWL, Animals, Blood Glucose, Chickens, Dietary Fats, Dietary Proteins, Eating, Energy Metabolism, Fatty Acids, Nonesterified, Hormones, Liver, Male, Organ Size, Thyroxine, Triglycerides, Triiodothyronine, Uric Acid, 0605 Microbiology, 0702 Animal Production, 0908 Food Sciences, Dairy & Animal Science, 3003 Animal production, 3006 Food sciences, 3009 Veterinary sciences

Abstract:

The aim of this study was to investigate the influence of dietary macronutrient ratio on postprandial (5 or 48 h after refeeding) endocrine functioning and metabolites of the intermediary metabolism and to relate these parameters with dietary-induced alterations in energy, protein, and lipid metabolism. Male broilers were reared from 1 to 7 wk of age on isoenergetic diets with substitutions between fat and protein but similar carbohydrate contents [low protein (LP): 126 vs. 242 g protein/ kg; low fat (LF): 43 vs. 106 g fat/kg]. The LP chickens had significantly increased postprandial plasma triglyceride levels. This was likely the result of stimulated hepatic lipogenesis, as corroborated by their significantly higher respiratory quotients. Plasma free fatty acid concentrations were higher in LP broilers, whereas glucose levels were unaffected by dietary composition, suggesting that these chickens preferred carbohydrates as an energy source over free fatty acids. Plasma uric acid levels were lower in LP compared with LF chickens, indicating a more efficient protein retention in the former group. LP birds that were fasted and refed at 48 h had higher plasma 3,5,3'-triiodothyronine (T-3) levels, corroborating their increased heat production. The postprandial T-3 increase was more pronounced in the LF chickens, possibly induced by their higher protein consumption.