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The effect of replacing corn with low-tannin sorghum on broiler performance, carcass yield, integrity of mucosa of small intestine segments, and activity of membrane enzymes of the jejunum is investigated. A total of 594 male Cobb-500 broiler chicks were randomly assigned to 3 dietary treatments: 100% corn (control), 50% corn replacement with low-tannin sorghum (low sorghum), and 100% corn replacement with low-tannin sorghum (high sorghum). Body weight gain, feed consumption, feed conversion, and carcass yield were determined at 7, 21, and 42 d, and segments of the small intestine were collected. Feed conversion and weight gain were impaired at d 42 in broilers fed the high-sorghum diet, but no differences were observed for carcass yield among the treatments (P > 0.05). Crypt cell mitotic index of the jejunum and ileum at d 21 and 42 was lower in broilers fed the control diet than in those fed low- and high-sorghum diets (P < 0.05). Aminopeptidase activity was higher in broilers fed the control diet than in those fed low- and high-sorghum diets irrespective of age (P < 0.05). Conversely, intestinal alkaline phosphatase activity in the small intestine did not differ among the dietary treatments (P > 0.05). Our results indicate that 50% corn replacement with low-tannin sorghum is suitable for broiler diets, whereas 100% corn replacement with low-tannin sorghum had negative effects on the intestinal mucosa and performance of broilers at 42 d.

Steers (379 +/- 10 kg) with ruminal, duodenal, and ileal cannulas were used in a 5 x 5 Latin square digestion trial to quantify and evaluate the relationship between intestinal protein supply and intestinal starch disappearance. Treatments were infusions of 0, 50, 100, 150, or 200 g/d of casein along with 1,042 g/d of raw cornstarch. Abomasal infusions were accomplished by passing tubing and a pliable retaining washer through the reticular-omasal orifice into the abomasum. Steers were fed a 93% corn silage, 7% supplement diet that contained 12% crude protein at 1.65% body weight in 12 equal portions/d. Periods lasted 17 d (12 d for adaptation, 2 d of collections, and 3 d of rest). The quantity and percentage of organic matter and protein disappearance from the small intestine increased linearly (P < 0.03) with infused casein. Greater quantities of starch disappeared with increased casein infusion (P < 0.01). The infusion of 200 g/d of casein increased small intestinal starch disappearance by 226 g/d over the control. Casein infusion did not affect the quantity or percent of organic matter, starch, or protein disappearance in the large intestine. Treatments did not change ruminal ammonia N, ruminal pH, or plasma glucose concentrations. Starch disappearance from the small intestine was increased with greater protein flow to the duodenum of steers.

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.

The promoter region and the beginning of the coding region of the hsp70 stress gene were analysed in broiler chickens of a commercial breed (Hubbard-Pettersen), a breed selected for weight gain (PP1) and a non-selected breed (naked-neck Label Rouge). The naked neck gene (Naked neck, Na), which reduces feathering in birds and is thus related to heat resistance, was present in both PP1 and Label Rouge breeds. Genomic DNA was restricted with PstI and Southern blotting analysis of the samples revealed the absence of polymorphic sites for that enzyme in the promoter region and beginning of the coding region of the hsp70 gene of studied birds. PCR-SSCP analysis of these regions, however, indicated the presence of polymorphisms in the beginning of the coding region and the sequencing of the PCR products confirmed and identified two polymorphic sites in this region: a transition A → G in position +258 and a transversion C → G in position +276. Both mutations were considered to be silent, since they did not modify the aminoacid sequence of the protein Hsp70. The promoter region of the hsp70 gene was identical in all studied birds, indicating that the regulation pattern of this gene must be the same in all birds at the promoter region. Three different alleles (hsp70-1, hsp70-2 and hsp70-3) were identified for the hsp70 gene from the observed mutations. The allele hsp70-3 was detected in only two breeds, Hubbard-Pettersen and PP1, but at a low frequency (0,016 and 0,006, respectively).

RESUMO -O presente estudo foi realizado com o objetivo de pesquisar o desempenho e quantificar a atividade das enzimas digestivas: amilase, lipase e tripsina, dos frangos de corte submetidos a diferentes níveis de energia, na dieta, e a diferentes doses de probiótico na ração. Foram utilizados 360 pintos da linhagem Hubbard, alimentados com dietas contendo 2.900 e 3.200 kcal EM/kg, associadas com a adição de 0, 200 e 400 ppm de probiótico (Bacillus subtilis -10 10 células viáveis esporuladas/grama de produto). Aos 14, 28 e 42 dias de idade, duas aves de cada unidade experimental foram abatidas, o pâncreas e o intestino delgado retirados, pesados e rapidamente congelados em nitrogênio líquido para posterior determinação das atividades enzimáticas. O delineamento experimental utilizado foi em parcelas subdivididas em seis tratamentos principais (dois níveis de energia vs três níveis de probiótico) e três tratamentos secundários (idades), com as parcelas distribuídas em três blocos ao acaso. Não foram encontrados efeitos significativos para a adição de probiótico na dieta em relação ao desempenho e às atividades enzimáticas. O nível de energia na dieta mostrou efeito significativo para o desempenho e as atividades da lipase e amilase (expressas por kg de peso vivo). Foi observado também que, em função da idade, houve diminuição da atividade da lipase, com exceção da amilase e tripsina pancreática, quando expressa em unidades por gramas de pâncreas. Os resultados obtidos neste experimento mostraram que a adição de probiótico (Bacillus subtilis) na dieta de frangos de corte não compromete o desempenho e nem a atividade das enzimas digestivas.Palavras-chave: enzimas digestivas, frangos de corte, probiótico Effect of Probiotic Supplementation on Performance and Digestive Enzymes Activity of Broiler ChickensABSTRACT -The present study was carried out aiming to investigate the performance, as well to quantify the digestive enzymes activities for the following enzymes: amylase, lipase and trypsin from broiler chickens fed with diets containing different in energy levels and mixed with different probiotic doses. Three hundred and sixty one-day old broilers from the Hubbard-Peterson chick strain were used in this experiment. The birds were fed diets containing 2,900 and 3,200 kcal ME/kg to which were added 0, 200 and 400 ppm of probiotic (Bacillus subtilis -10 10 sporulated viable cells/gram of product). At 14, 28 and 42 days of age, two birds of each treatment were sacrificed, the pancreas and small intestine withdrawn, weighed and frozen in liquid nitrogen for further enzymatic activity determinations. The experimental design was made up of subdivided parcels with 6 main treatments (two energy levels and three probiotic doses) and 3 secondary treatments (ages) with parcels distributed in 3 randomized blocks. It was not found statistically significant effects when probiotic was added to the diets with respect to performance and enzymatic activities. Energy levels had a significant effect on the performance and lipase and a...