The aim of the present study was to evaluate the effects of heat stress (HS) and methionine supplementation on the markers of stress and on the gene expression levels of uncoupling proteins (UCP), betaine -homocysteine methyltransferase (BHMT), cystathionine b-synthase (CBS), glutathione synthetase (GSS) and glutathione peroxidase 7 (GPx7). Broilers from 1 to 21 d and from 22 to 42 d of age were divided into three treatment groups related to methionine supplementation: without methionine supplementation (MD); recommended level of methionine supplementation (DL1); excess methionine supplementation (DL2). The broilers were either kept at a comfortable thermal temperature or exposed to HS (388C for 24 h). During the starter period, we observed the effects of the interaction between diet and environment on the gene expression levels of UCP, BHMT and GSS. Higher gene expression levels of UCP and BHMT were observed in broilers that were maintained at thermal comfort conditions and received the MD diet. HS broilers fed the DL1 and DL2 diets had the highest expression level of GSS. The expression levels of the CBS and GPx7 genes were influenced by both the environment and methionine supplementation. During the grower period, the gene expression levels of BHMT, CBS, GSS and GPx7 were affected by the diet £ environment interaction. A higher expression level of BHMT was observed in broilers maintained at thermal comfort conditions and on the MD diet. HS induced higher expression levels of CBS, GSS and GPx7 in broilers that received the DL1 and DL2 diets. The present results suggest that under HS conditions, methionine supplementation could mitigate the effects of stress, since methionine contributed to the increased expression levels of genes related to antioxidant activity.

RESUMO - O efeito da temperatura ambiente sobre desempenho e características de carcaça de frangos de corte alimentados com dieta controlada e dois níveis de energia metabolizável foi avaliado. Cento e sessenta frangos de corte machos Hubbard, de 21 dias de idade, com 791+4,12 g de peso médio inicial, foram alojados em ambiente com temperatura termoneutra (23,3±0,58ºC) ou quente (32,3±0,31ºC) até 42 dias de idade. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 2 x 2 (nível de energia metabolizável [3075 e 3300 kcal de EM/kg] e temperatura ambiente [termoneutro e calor]), com cinco repetições e oito aves por unidade experimental. As aves receberam iguais quantidades de ração nos dois ambientes. Ganho de peso e conversão alimentar foram influenciados negativamente pelo calor. Embora os pesos absolutos da carcaça e dos cortes (coxa, sobrecoxa, pernas e peito) e o rendimento de peito dos frangos mantidos sob estresse de calor tenham reduzido, o rendimento de carcaça aumentou. Os pesos, absoluto e relativo, das penas foram menores para os animais mantidos no calor. Os pesos, absoluto e relativo, da gordura abdominal foram maiores para os frangos de corte criados no calor. A alta temperatura ambiente reduziu os pesos, absoluto e relativo, de coração, fígado, moela e intestinos, entretanto, o peso relativo dos pulmões e do proventrículo não foi influenciado. O estresse de calor influenciou negativamente o desempenho, reduziu o rendimento de peito e o peso de órgãos vitais, bem como aumentou a gordura abdominal de frangos de corte, independente do nível energético da ração.

Background This study evaluated the effects of Eimeria spp. challenge and dietary supplementation with free methionine or methionine dipeptide on animal performance; expression of genes associated with the immune system, antioxidant system, and amino acid transport in the jejunum; and redox status of the jejunum of broiler chickens. Methods A randomized, 2 × 3 factorial design was used, in which Eimeria spp . challenge was the first factor ( Eimeria -challenged, EC, or unchallenged, UC, broilers) and methionine supplementation was the second factor (non-supplemented, NS; free dl -methionine, dl -Met; and methionine dipeptide, dl -methionyl- dl -methionine, dl -MMet). At 14 days of age, chickens were inoculated orally with sporulated oocysts of Eimeria acervulina , Eimeria praecox , Eimeria maxima , and Eimeria mitis . Birds were killed by cervical dislocation 144 h post-inoculation (PI), and the jejunum was collected for biochemical and molecular analyses. Results EC broilers had a 13% lower feed intake (FI), 37% lower body weight gain (BWG), and 39% higher feed conversion ratio (FCR) than UC broilers. Chickens fed the dl -Met diet had higher BWG (about 12% higher) and better FCR (about 12% lower) than chickens fed the NS diet. EC chickens had lower relative weight of the bursa of Fabricius (51.8%) and higher relative weights of the spleen and whole intestine (53.6% and 26.3%, respectively) than UC chickens. Eimeria spp. challenge led to an increase in the levels of oxidative substances, such as nitrite and thiobarbituric acid reactive substances (TBARS), in the jejunum of chickens 144 h PI. Among UC chickens, those fed the dl -Met diet had higher total antioxidant capacity (TAC) and lower catalase (CAT) and superoxide dismutase (SOD) activities. EC chickens that received the NS diet had higher carbonylated protein content (CP). This result was associated with their lower TAC and catalase activity. The lower TAC in EC chickens might have been due to reduced expression of catalase ( CAT ) and superoxide dismutase 1 ( SOD1 ) genes. Chickens fed the dl -Met and dl -MMet diets had lower nitrite content. Eimeria spp. challenge suppressed neutral amino acid transporter 1 ( B 0 AT1) , peptide transporter 1 ( PEPT1) , toll-like receptor 5 ( TLR5) ...

This study was conducted to verify the effects of dietary crude protein reduction on growth and carcass performance of 22-42-day-old broilers reared under different temperatures. Treatments were set up in a five by two factorial arrangement, with five crude protein levels (220, 210, 200, 190 and 184 g/kg) and two temperatures (21.6 and 32.2 o C). Diets were isocaloric and essential amino acid-to-lysine ratio was maintained constant in all treatments. There was no interaction between crude protein reduction and environmental temperature for any of the parameters evaluated. Crude protein had no influence on feed intake. Nevertheless, weight gain and feed conversion ratio were linearly influenced by crude protein reduction. Worse performance was also observed in birds exposed to heat stress as compared with birds kept under thermoneutral temperature. There was no effect of crude protein reduction on breast and legs. Birds kept under heat stress had lower breast yield and higher leg yield as compared with broilers reared at 21.6 o C. Any crude protein reduction in the range of 220 to 184 g/kg for 22 to 42-day-old broilers has a negative effect on their performance. Heat stress worsens broiler performance and breast yield.

Utilizaram-se 240 frangos de corte machos Hubbard com peso médio inicial de 689+5,27 g, mantidos de 22 a 42 dias de idade, em condições de estresse de calor (31,9+0,29ºC). Foi usado delineamento inteiramente casualizado, com cinco tratamentos (3000, 3075, 3150, 3225 e 3300 kcal de energia metabolizável/kg de ração), seis repetições e oito animais por unidade experimental. Avaliaram-se os efeitos de níveis de energia metabolizável (EM) sobre o desempenho, a qualidade de carcaça e as variáveis fisiológicas de frangos de corte alimentados de forma controlada (93% do consumo voluntário) com rações isoprotéicas. O ganho de peso e a conversão alimentar elevaram-se e o consumo de energia metabolizável aumentou linearmente, em razão do nível de EM das rações. Observou-se que as deposições de proteína e gordura na carcaça foram influenciadas de forma linear crescente, enquanto o peso absoluto da sobrecoxa apresentou variação quadrática. Os pesos absoluto dos pulmões e do coração e o relativo dos pulmões dos frangos de corte foram influenciados pelo nível de EM das rações. O nível de 3300 kcal de EM proporcionou os melhores resultados de desempenho, enquanto o de 3108 kcal resultou em maior deposição de proteína, com menor proporção de gordura na carcaça de frangos de corte mantidos em condições de estresse de calor.