BACKGROUND: Leucine is one of the subgroups of amino acids, which play an important role in the anabolism of muscles, adipose tissue, and the liver by stimulating insulin secretion.OBJECTIVES: Effects of different levels of leucine were investigated on carcass yield, characteristics, and quality, and expression of insulin-like growth factor (IGF-1) and insulin genes in male broilers.METHODS: Five levels of L-leucine (100, 110, 120, 130, and 140 % of Ross strain requirements) were tested with 250 male one-day-old chicks in a completely randomized design with five treatments and five replicates (containing 10 chicks each). On day 42 of their age, the blood samples of two birds from each replicate (10 birds per treatment) were taken to determine serum IGF-1 gene expression. Subsequently, these birds were slaughtered for analysis of carcass characteristics and quality, and collecting the samples of liver and breast for expression of IGF-1 and insulin genes.RESULTS: Body weight increased by consumption of 140 % of leucine as compared to 100 %. Reduction in feed conversion ratio was observed by feeding 140 % of leucine level. The IGF-1 gene expression of breast and liver increased by 110 % of leucine level. Moreover, feeding 110 % of leucine level caused a higher expression of insulin gene in breast and liver. Consumption of 130 % of leucine improved the meat protein, fat, and ash contents. Furthermore, consumption of 110 % of leucine increased the serum IGF-1 concentration.CONCLUSIONS: Consumption of leucine in broiler diets was found to increase the expression of IGF-1 and insulin genes and consequently, improve the performance and carcass quality. It also decreased the abdominal fat in broiler chickens.

The present study was carried out to examine the sustained release effect of the implantable bovine somatotropin (SRI-BST) formula. In the blood profile test in steers, the bovine somatotropin concentration in serum by radioimmunoassay showed the peak concentration on the first day after the implantation of the SRI-BST formula, and concentration proceeded for 5 days (p less than 0.05). The insulin-like growth factor-1 concentration showed the peak concentration on the seventh day after implantation of the SRIF-BST formula, and concentration proceeded for 10 days (p less than 0.05). The glucose showed the peak concentration on the first day after implantation of the SRI-BST formula, and concentration continued for 3 days (p less than 0.05). The blood urea nitrogen showed the lowest concentration on the third day after implantation of the SRI-BST formula, and concentration continued for 7 days (p less than 0.05). these results proved that the SRIF-BST formula was the sustained release effects in steers.

Para avaliar a influência de dietas deficientes em energia sobre o perfil hormonal, metabólico e clínico em bovinos, foram usados 12 garrotes aleatoriamente distribuídos em três grupos com quatro animais para receber por 140 dias, as rações: (G1) adequada, para ganho de peso de 900g/dia (17,7 Mcal/d de ED e 13% de PB); (G2) 80% dos requerimentos de mantença (5,8 Mcal/d de ED e 7% de PB); e (G3) 60% dessas exigências (4,7 Mcal/d de ED e 5% de PB). Nos grupos G2 e G3 houve acentuada diminuição do peso vivo e do consumo de alimentos. O déficit energético provocou redução destacada nos teores sanguíneos de IGF-1 e T3. A perda de peso foi uma direta consequência do menor consumo de alimentos, da qualidade inferior de ração ingerida e da menor atuação de IGF-1 e T3. A mensuração da altura dos animais ao término do experimento apresentou uma diferença no G1 de 59% e 73% maior que G2 e G3, respectivamente. O IGF-1 foi considerado o principal indicador do status energético, pois diminuiu de maneira sensível e rápida sua concentração no decorrer do tempo experimental; este hormônio foi diretamente influenciado pelos teores de T3. | To evaluate the influence of diets with different degrees of energy deficiency on the hormonal profile, and on metabolic and clinical states of steers, 12 steers were randomly distributed in three groups of four animals each. The groups received the following diets for 140 days: (G1) 100% of the maintenance to stimulate to weight gain of 900 gr/day (DE: 17.7 Mcal/d and 13% de CP); (G2) 80% of the maintenance (DE: 5.8 Mcal/d and 7% de CP); (G3) 60% of the same requirements (DE: 4.7 Mcal/d and 5% de CP). In both energy deficiency groups (G2 and G3) there was a decrease in body weight and in feed intake during experimental period. In relation to hormonal profile, the energy deficit caused an acute reduction in plasma levels of IGF-1 and T3. Weight loss was due to lower feed intake, poor quality of diet ingested and also due to low concentrations of IGF-1 and T3. Measuring height of animals at the end of the experiment showed a difference of 59% in G1 and 73% higher than G2 and G3, respectively. IGF-1 was considered the best indicator of the energetic status, because its blood levels reduction was sensible and rapid during the dietary energy deficit; and it was influenced directly by level of T3.