The effect of continuous and cyclical heat stress on broiler growth performance, nutrient digestibility, energy and nitrogen balances was investigated. Four hundred and fifty, 21-day-old, Cobb male broilers were raised in battery cages in five treatments: 22C/AL (continuous 22°C, ad libitum feed consumption); 32C/AL (continuous 32°C, ad libitum feed consumption); 22C/PF32C (continuous 22°C, pair-fed on the daily feed intake of 32C/AL); CY/AL (cyclical-32°C for 8 h and 25°C for 12 h, ad libitum feed consumption); 22C/PFCY (continuous 22°C, pair-fed on the daily feed intake of CY/AL). Between 39 and 42 days of age, dry matter, crude protein, crude fat and AME n were analyzed in the diets and excreta to determine nutrient digestibility. Energy and nitrogen balances were evaluated through comparative slaughter (21 and 42 days of age). Growth performance was significantly lower in broilers exposed to either continuous or cyclical heat stress. However, the cyclical heat stress had a lower effect on feed intake and weight gain and no effect on the feed conversion rate. Nutrient digestibility was only influenced by continuous heat exposure, decreasing dry matter (3.9%) and protein digestibility (9.7%) in comparison to control birds. Broilers exposed to continuous heat stress increased metabolizable energy intake (20.3%) and heat production (35.5%), and decreased energy retention (20.9%) and energy efficiency (32.4%) in relation to control ones. Nitrogen intake and nitrogen retention were reduced by both forms of heat exposure, in comparison to control, but more strongly under continuous heat. Nitrogen retention was reduced by 50.4% and 20.4%, for continuous or cyclical heat stress, respectively. Nitrogen efficiency was reduced only by the continuous heat exposure (33.1%). These results revealed important differences between the effects of a continuous or a cyclical heat exposure in broiler chickens for digestibility, performance and energy and nitrogen balances.

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This study aimed to assess the effects of glutamine as feed additive on performance and intestinal mucosa morphometry of broiler chickens vaccinated against coccidiosis. A total of 400 day-old male chicks were randomly assigned to four treatments (NVNG -no vaccination, no glutamine supplementation; NVG -no vaccination, glutamine supplementation (10 g kg −1 ); VNG -vaccination, no glutamine supplementation; VG -vaccination, glutamine supplementation) replicated four times with 25 birds per replicate. A commercial sprayed-on vaccine against coccidiosis containing Eimeria acervulina, E. maxima, E. mivati, and E. tenella was administered at the hatchery. Broiler performance was evaluated from 1-28 days, and morphometric parameters were analyzed at 14, 21, and 28 days of age. Body weight gain and feed intake were negatively affected by vaccination, but not by glutamine. Vaccination increased crypt depth in the duodenum and jejunum at 21 and 28 days. In conclusion, this study showed that glutamine was not able to increase weight gain of broiler chickens, irrespective of whether the animals were vaccinated or not against coccidiosis. Glutamine supplementation was able to improve feed conversion in vaccinated birds suggesting trophic effect on intestinal epithelium improving.

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The objectives of this study were to describe alterations that age and dietary inclusion of direct-fed microbial (DFM) Bacillus subtilis (BS) and a specific essential oil (EO) blend (carvacrol, cinnamaldehyde, cineol, and pepper extract) causes in the activity of digestive enzymes (maltase: MALT; aminopeptidase-N: APN; intestinal alkaline phosphate: IAP) and expression patterns of genes related to transport (oligopeptide transporter gene: SLC15A1; Na+-dependent glucose and galactose transporter gene: SLC5A1; Na+-independent glucose, galactose, and fructose transporter gene: SLC2A2; ATPase, Na+/K+ transporting gene: ATP1A1) and digestion (aminopeptidase-N gene: ANPEP; maltase-glucoamylase gene: MGAM; Sucrase-isomaltase gene: SI) of carbohydrates and proteins in the small intestine of broilers. Also, the objective was to analyze if growth performance of broilers is affected by supplementation (BS and EO blend). Day-old male broiler chicks (n = 1,320) were assigned to 5 treatments. Diets included a basal diet (BD) as a negative control (CON); experimental diets were BD + BS; BD + BS + EO; BD + EO; BD + antibiotic growth promoter (AGP) avilamycin was the positive control. Performance was evaluated between 1 to 42 d. Transcript abundance of transport-related genes and digestion-related genes were assayed by RT-qPCR and determined at d 7, 21, and 42. MALT-, APN-, and IAP-specific activities were determined at d 7, 21, and 42. Broilers fed BS had greater SLC15A1 mRNA abundance compared to CON, while EO and AGP were related to higher activities of IAP and APN. Analysis over time revealed higher abundance of MGAM, SLC2A2, SLC15A1, SLC5A1 and SI mRNA at d 42 when compared to d 7. Activity of IAP decreased after d 7 and activity of MALT increased with age. The current study suggests that age had effect over carbohydrate and protein transport and carbohydrate digestion. The supplementation of BS DFM hade evident effect over protein transport and that the use of EO in the diet enhanced the activities of carbohydrate and protein digestion, reflecting improvement in digestive and transport physiology of birds. Changes performed by BS DFM and EO did not favor performance.

Breast weight has great economic importance in poultry industry, and may be associated with other variables. This work aimed to estimate phenotypic correlations between performance (live body weight at 7 and 28 days, and at slaughter, and depth of the breast muscle measured by ultrasonography), carcass (eviscerated body weight and leg weight) and body composition (heart, liver and abdominal fat weight) traits in a broiler line, and quantify the direct and indirect influence of these traits on breast weight. Path analysis was used by expanding the matrix of partial correlation in coefficients which give the direct influence of one trait on another, regardless the effect of the other traits. The simultaneous maintenance of live body weight at slaughter and eviscerated body weight in the matrix of correlations might be harmful for statistical analysis involving systems of normal equations, like path analysis, due to the observed multicollinearity. The live body weight at slaughter and the depth of the breast muscle as measured by ultrasonography directly affected breast weight and were identified as the most responsible factors for the magnitude of the correlation coefficients obtained between the studied traits and breast weight. Individual pre-selection for these traits could favor an increased breast weight in the future reproducer candidates of this line if the broilers' environmental conditions and housing are maintained, since the live body weight at slaughter and the depth of breast muscle measured by ultrasonography were directly related to breast weight. Key words: animal breeding, multivariate analysis, phenotypic correlation, poultry, pre-selection Características de produção e de composição corporal de frangos em relação ao peso de peito avaliada por análise de trilha RESUMO: O peso do peito possui grande importância econômica na indústria de frangos, podendo estar associado a outras variáveis passíveis de seleção. Estimaram-se correlações fenotípicas entre características de desempenho (peso vivo aos 7, 28 dias e ao abate e profundidade de músculo peitoral por ultra-sonografia), carcaça (peso eviscerado e de pernas) e composição corporal (peso do coração, do fígado e da gordura abdominal), em uma linhagem de frangos, e quantificou-se a influência direta e indireta destas variáveis sobre o peso do peito. Para tanto, utilizou-se a análise de trilha, desdobrando-se a matriz de correlações parciais em coeficientes que forneceram a influência direta de uma variável sobre a outra, independentemente das demais. A manutenção das variáveis peso vivo ao abate e peso eviscerado na matriz de correlações pode ser prejudicial à análise estatística que envolve os sistemas de equações normais, como a análise de trilha, devido à multicolinearidade observada. O peso vivo ao abate e a profundidade do músculo peitoral por ultra-sonografia apresentaram efeitos diretos importantes sobre o peso de peito e foram identificadas como as principais responsáveis pela magnitude dos coeficientes de correlação obtidos. Assi...

SUMMARYHeat stress (HS) is among the major limiting factors to growth of broilers. Heat stress also results in changes in the characteristics of the carcass, such as an increase in fat deposition. The molecular mechanisms responsible for fat deposition in broilers as a response to HS remain unknown. The current study aimed to describe the molecular mechanisms associated with the effects of high temperature and feed restriction due to chronic heat exposure at 32 °C, and to describe the resulting changes in the growth performance and carcass characteristics of the broilers at 21 and 42 days of age. In the current study, 441 male Cobb-500® broilers were subjected to three treatments that differed in rearing temperature and feeding regime: chronic HS fed ad libitum (HS/AL), thermoneutral environment fed ad libitum (TN/AL) and TN and pair-feeding on the feed intake (FI) of the heat-exposed group (TN/PF). HS increased fat content in the breast and wings and decreased fat content in the legs, but did not influence abdominal fat. These effects occurred regardless of reducing consumption induced by HS. Furthermore, HS, independently of reduced FI, increased liver sterol-regulatory element-binding protein-1 (SREBP-1) mRNA in both ages and growth hormone receptor (GHR) mRNA at 42days, whereas feed restriction reduced GHR mRNA only at 21days. In conclusion, increased fat content in the breast and wings was accompanied by a higher gene expression of GHR and SREBP-1, suggesting the involvement of both genes in the control of fat deposition in broilers exposed to HS.

1. An experiment was conducted to study the effect of two different diets on zootechnical performance and the major bacterial groups in association with the host mucosa and dispersed in the lumen contents of the small intestine of broiler chickens. 2. The two experimental diets were maize or sorghum-based. In addition to the total bacteria, bacterial groups belonging to the Enterobacteriaceae (Enterococcus and Lactobacillus) were quantified by real-time PCR. 3. There were no differences in body weight gain and feed intake, but feed conversion ratio increased for sorghum-fed broilers at 21 and 42 d of age. 4. The Enterococcus group decreased in all gut segments from 7 to 42 d, while the Lactobacillus group increased in both ecosystems. In the ileal mucosa, the enterobacterial counts decreased from 7 to 42 d in the maize-based diet, but remained stable in the sorghum-based diet. 5. The results shed light on the spatial and temporal distribution of bacterial groups that play important physiological roles in the small intestine of chickens. Specifically, the increased Enterobacteria population in the ileum is consistent with the relatively poor feed conversion in sorghum-fed broilers.