Histomorfometria e função da tireóide de frangos de corte após ingestão por curto período de toxina T-2 de Fusarium sporotrichioides

Effect of cyclic heat stress on thyroidal hormones, thyroid histology, and performance of two broiler strains

This study determined thyroid hormone (T₃ and T₄) serum levels and investigated thyroid gland histology, as well as two broiler strains performance kept at different periods of heat stress. Broilers (560 Cobb Slow™ and 560 Hubbard Flex™) were distributed in control environment (0) reared following the thermal recommendations, and environments 1, 2, and 3 exposed to high temperatures for 1 h, 2 h, and 3 h a day, respectively, from 14 to 42 days old. At 21, 28, 35, and 42 days old, blood samples were collected to determine T₃ and T₄ serum levels. At 42 days old, thyroid glands were removed for histological analyses. The performance was calculated weekly. T₃ levels decreased with age advance, while T₄ serum concentration was higher at 42 days old (23.27 nmol L^-1) and lower at 28 days old (15.69 nmol L^-1). The histological sections revealed that thyroid morphology was well preserved. Live weight was higher in Cobb Slow™ (2.97 kg) than Hubbard Flex™ (2.93 kg) broilers at 42 days old. It is possible to conclude that cyclic heat stress exposure for a 3-h period from 14 to 42 days old did not affect performance, thyroid histology, or T₃ and T₄ serum levels. Cobb Slow™ broilers had the best live weight values at slaughtering. With increasing age, T₃ levels decreased and T₄ levels increased for both strains.

Growth performance, morphometric analysis of the intestinal mucosa and thyroid of broiler fed canola meal

ABSTRACT The aim of this study was to evaluate the effect of replacing soybean meal with canola meal in broiler diets on performance, liver histopathology, morphometry of the intestinal mucosa and thyroid. One-day-old Cobb chicks (n=300) were distributed in a completely randomized design, with increasing levels of replacement of soybean meal with canola meal (0, 25, 50, 75 and 100%) and 6 repetitions of 10 birds each. Weight gain decreased linearly (P< 0.05) with increasing levels of inclusion of canola meal, in all stages. Villus height in the duodenum and jejunum linearly decreased (P< 0.05). Follicle diameter and thyroid follicular epithelium height increased linearly with increasing levels of canola meal (P< 0.05). Similarly, there was an increase in relative weight of liver and heart, and liver steatosis in the highest levels of replacement. In conclusion, the replacement of soybean meal with canola meal can reduce performance, adversely affecting the thyroid, liver and the morphometric characteristics in the duodenum and jejunum.