Dietary macronutrients and performance and plasma hormone and metabolite levels of broiler chickens fat by carbohydrate substitution

The present experiment was aimed to study the effects of an isocaloric substitution of fat by carbohydrate calories while maintaining the same CP content - on some endocrine parameters and key metabolites of the lipid (L), protein (CP) and carbohydrate (CHO) metabolism and muscle cell membrane integrity of broiler chickens. Ninety male broiler chicks (Cobb) were obtained at 1-day old and raised in an environmentally controlled room. Food and water was provided ad libitum. At day 7, the chicks were provided with the experimental diets: Control diet (CON: 20% CP; 9.1% L; 39.6% CHO), Low lipid diet (LowL: 22% CP; 3.36% L; 59.7% CHO), and low carbohydrate diet (LowCHO: 22% CP; 8.09% L; 46.7% CHO). T e chickens fed the CON manifested the best growth rate feed conversion compared to both other groups. The CO chickens showed the highest plasma T-3 Concentrations at 14 days of age as compared to both LowL and LowCHO chickens. At 35 days of age however, LowL chickens were characterized by the highest plasma T-3 levels. Overall, CON birds had the highest plasma T-4 levels (P < 0.0001) compared to LowL and LowCHO chickens. Plasma corticosterone levels were not affected by diet composition. Glucose levels increased towards the end of the experimental period, but there was no overall effect of diet composition on plasma glucose levels. Chickens fed the CON diet were consistently characterized by the highest plasma uric acid levels compared to LowL and LowCHO chickens. Irrespectively of diet, plasma triglyceride levels were high at 14 days of age, then decreased and finally increased again during the last week. This latter increase was most pronounced for the CON chickens and is congruous with their high fat deposition. At 28 days of age, a significant effect of diet was observed, as CON birds had lower plasma free fatty acid (FFA) levels compared to LowL but not to LowCHO chickens. However there was no overall effect of diet composition on plasma FFA levels. Creatine kinase (CK) activities increased significantly with age and were consistently higher in CON chickens. In conclusion, fast growth in broiler chickens is positively correlated with catabolism of protein from dietary or endogenous origin and (muscle) cell membrane disruption as reflected in high plasma uric acid levels and CK activity, respectively. The currently investigated substitution of fat by CHO had no marked effects on endocrine functioning and intermediary metabolism, but this does not exclude that larger substitutions between both nutrients can have an effect

Dietary macronutrients, endocrine functioning and intermediary metabolism in broiler chickens - Pair wise substitutions between protein, fat and carbohydrate

Three pens of male broiler chicks were raised under standard conditions and fed from 7 to 42 days of age three isocaloric diets each with 15.8; 19.6 and 19.5% of CP; and 51, 51, and 44% of CHO; and 6.5; 3.0 and 7.7% of fat, and designated as the low protein (LowCP), low lipid (LowL) and low carbohydrate (LowCHO) diets, respectively. Body weights and feed intake were monitored weekly and blood samples were collected at the same time for posterior analysis of hormone and metabolite content. Chickens fed the LowCP diet were characterized by a reduced body weight gain and feed intake and poorer feed conversion efficiency compared to those fed the LowL and LowCHO diets, which were very similar in this respect. Plasma corticosterone and glucose levels and creatine kinase activity were not significantly changed by diet composition. LowCP chickens were characterised by the lowest plasma T-4 and uric acid levels (indicative for reduced protein breakdown and lower protein ingestion) but highest plasma triglyceride levels (congruent with their higher fat deposition) compared to the LowL and LowCHO chickens. LowL chickens had on average higher plasma T-3 and free fatty acid levels compared to the LowCP and LowCHO chickens.In conclusion, a limited substitution of carbohydrate for fat in iso-nitrogenous, iso-energetic diets has no pronounced effects on plasma hormone and metabolite levels, except for the elevation in T-3 (may enhance glucose uptake) and free fatty acid levels in the plasma of the chickens fed the LowL diet. The protein content of the diet has a greater impact on zootechnical performance, and underlying endocrine regulation of the intermediary metabolism compared to the dietary lipid and CHO fraction. (C) 2003 Elsevier B.V. All rights reserved

Metabolism of stevioside by chickens

In intubation experiments (643-1168 mg per animal), most of the stevioside administered to chickens was recovered unchanged in the excreta, and only about 2% was converted into steviol. Neither stevioside nor steviol could be found in the blood. In chronic studies (667 mg of stevioside/kg of feed) with laying hens and meat-type chickens, no significant differences were found in feed uptake, weight gain, and feed conversion as the result of stevioside administration. The egg production and egg composition of laying hens were not influenced. Most of the stevioside taken up was found untransformed in the excreta, and about 21.5% or 7.3% was converted to steviol by meat-type chickens or laying hens, respectively. No stevioside or steviol could be detected in the blood or in the eggs of the different groups of animals. In anaerobic incubation experiments with chicken excreta, only a 20% conversion of stevioside into steviol was found. No harmful effects were observed in the chronic stevioside supplementation experiments nor in the intubation experiments in which very high stevioside doses were given.status: publishe

Effect of protein, carbohydrate, lipid, and selenium levels on the performance, carcass yield, and blood changes in broilers

The objective of this study was to evaluate the performance, carcass and parts yield, and blood changes in broilers fed different protein, carbohydrate, and lipid levels. Birds were fed a commercial diet until seven days of age. On day 8, birds were distributed according to a completely randomized experimental design in a 4 x 2 factorial arrangement (control diet, low protein diet, low carbohydrate diet or low lipid diet vs. supplementation of 0 or 0.3ppm organic selenium) with four replicates of 15 birds each. Broilers fed low protein presented lower body weight, feed intake, and worse feed conversion ratio on day 42, as well as lower carcass and breast yields, higher leg and abdominal fat yields, higher triglyceride and lower uric acid blood levels. Broilers fed the low carbohydrate diets presented low glucose levels on days 14 and 42.Creatine-kinase (CK) levels increased as birds aged. The livability of broilers fed the low protein diets improved and of those fed low carbohydrate diets worsened with dietary selenium addition on days 35 and 42. Selenium supplementation increased glucose levels in 42-d-old broilers. Changes in dietary protein caused more impact on broiler performance compared with carbohydrates and lipids. Changes in macronutrients caused metabolic changes in broilers. Selenium affected broiler livability as measured on days 35 and 42, and glucose blood levels.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Effects of dietary macronutrient content on energy metabolism and uncoupling protein mRNA expression in broiler chickens

The objective of the present study was to investigate the effects of dietary macronutrient ratio on energy metabolism and on skeletal muscle mRNA expression of avian uncoupling protein (UCP), thought to be implicated in thermogenesis in birds. Broiler chickens from 2 to 6 weeks of age received one of three isoenergetic diets containing different macronutrient ratios (low-lipid (LL) 30 v. 77 g lipid/kg-, low-protein (LP) 125 v. 197 g crude protein (N X 6.25)/kg; low-carbohydrate (LC) 440 v. 520 g carbohydrate/kg). LP chickens were characterised by significantly lower body weights and food intakes compared with LL and LC chickens (-47 and -38% respectively) but similar heat production/kg metabolic body weight, as measured by indirect calorimetry, in the three groups. However, heat production/g food ingested was higher in animals receiving the LP diet (+41%, P<0.05). These chickens also deposited 57% less energy as protein (P<0.05) and 33% more as fat. No significant differences in energy and N balances were detected between LL and LC chickens. The diets with the higher fat contents (i.e. the LP and LC diets) induced slightly but significantly higher relative expressions of avian UCP mRNA in gastrocnemius muscle, measured by reverse transcription-polymerase chain reaction, than the LL diet (88 and 90 v. 78% glyceraldehyde-3-phosphate dehydrogenase respectively, P<0.05). Our present results are consistent with the recent view that UCP homologues could be involved in the regulation of lipid utilisation as fuel substrate and provide evidence that the macronutrient content of the diet regulates energy metabolism and especially protein and fat deposition.status: publishe

Cold-induced enhancement of avian uncoupling protein expression, heat production, and triiodothyronine concentrations in broiler chicks

The relationships among avian uncoupling protein (avUCP) mRNA expression, heat production, and thyroid hormone metabolism were investigated in 7-14-day-old broiler chicks (Gallus gallus) exposed to a low temperature (cold-exposed chicks, CE) or a thermoneutral temperature (TN). After 7 days of exposure, CE chicks exhibited higher heat production (+83%, P < 0.01), avUCP mRNA expression (+20%, P < 0.01), and circulating triiodothyronine (T-3) levels (+104%, P = 0.07) for non-statistically different body weights and feed intake between 3 and 7 days of exposure as compared to TN chicks. Plasma thyroxine (T-4) concentration was clearly decreased in CE chicks (-33%, P = 0.06). The lower hepatic inner-ring deiodination activity (-47%) and the higher renal outer-ring deiodination activity (+75%) measured in CE compared to TN chicks could partly account for their higher plasma T3 concentrations. This study describes for the first time the induction of avUCP mRNA expression by low temperature in chickens, as it has been previously shown in ducklings, and supports the possible involvement of avUCP in avian thermogenesis. (C) 2003 Elsevier Science (USA). All rights reserved.status: publishe