Effects of supplemental ascorbic acid on the energy conversion of broiler chicks during heat stress and feed withdrawal

Abstract

The objectives of this study were 1) to determine the effects of supplemental ascorbic acid (AA) on the energy conversion of broiler chicks maintained at thermoneutral and potential heat stress temperatures using indirect convective calorimetry; and 2) to determine whether changes in energy conversion are reflected in changes in lipid metabolism. In Experiment 1, 120 2-d-old cockerels, housed in two identical environmental chambers, were maintained under constant light (2.0 +/- 0.2 fc) and recommended thermal conditions (29.6 +/- 0.8 C; 33.4 +/- 8.0% RH) and consumed water and feed ad libitum. Beginning on Day 8 posthatch, one-half of the birds inside each chamber were randomly assigned and received feed supplemented with AA. Beginning on Day 9 posthatch, the temperature inside one chamber was increased to 34 C whereas the other chamber remained thermoneutral. This design resulted in four treatments: 1) thermoneutral (TN: 27.7 +/- 0.8 C; 40.9 +/- 9.4% RH) and 0 mg AA/kg feed (ppm); 2) TN and 150 ppm AA; 3) heat stress (H: 33.8 +/- 0.5 C; 43.3 +/- 7.4% RH) and 0 ppm AA; or 4) H and 150 ppm AA. Also beginning on Day 9 posthatch, birds were randomly assigned to one of three identical, indirect convective calorimeters designed to accommodate TN or H. Oxygen consumption, carbon dioxide production, respiratory quotient, and heat production were evaluated daily for 8 h, through Day 17 posthatch. Following calorimetric measurement, birds were returned to their respective caging unit/chamber for the remainder of the study. Weight gain, feed intake, and gain: feed were also measured over the 9-d study. Heat exposure depressed (P < 0.05) weight gain, feed intake, and gain:feed. Ascorbic acid increased (P < 0.10) weight gain. Oxygen consumption and carbon dioxide and heat production per kilogram0.75 decreased (P < 0.05) with age with no change in the respiratory quotient. Heat exposure lowered (P < 0.001) the respiratory quotient. A temperature by AA interaction was detected in which heat-exposed birds expressed lower (P < 0.10) respiratory quotients when consuming the AA-supplemented diet. In Experiment 2, 18 2-d-old cockerels, housed in an environmental chamber, were maintained under constant light and recommended thermal conditions (29.3 +/- 0.4 C; 41.4 +/- 3.3% RH) and consumed water and feed ad libitum. On Day 9 posthatch, birds were deprived of feed for 24 h with ad libitum access to water supplemented with either 0 or 400 mg AA/L. Blood samples were obtained from each bird before and after feed withdrawal and supplementation. Supplemented birds exhibited elevated (P < 0.01) plasma AA, levels that were not affected by feed deprivation. Feed deprivation increased (P < 0.0001) plasma beta-hydroxybutyrate with no effect of AA, and decreased (P < 0.05) plasma triglycerides in the unsupplemented birds. A feed withdrawal by AA interaction was detected in which plasma triglycerides remained elevated in birds supplemented with AA. These data suggest that supplemental AA influences body energy stores that are used for energy pu...

Cold-Induced Ascites in Broilers: Effects of Vitamin C and Coenzyme Q10

“…Broilers submitted to heat stress and supplemented with Vit. C presented better performance, as well as lower plasma corticosterone and higher thyroid hormone levels compared with non-supplemented birds (McKee et al, 1997).…”

“…Cold stress increases the energy requirement for thermoregulation, diverting the available energy for production to maintenance (Hangalapura et al, 2003). Cold-exposed broilers also increase their FI to increase the thermogenic effect of nutrient absorption, assimilation, and utilization (McKee et al, 1997;Collin et al, 2003). Under low environmental temperatures, the activity of the thyroid increases, resulting in high metabolic rate, oxygen consumption, and FI for thermoregulation, which may lead to reduced BWG.…”

“…C may reduce plasma corticosterone. A likely mechanism is inhibited by C-21 hydroxylase and 11-b hydroxylase and decreased corticosterone synthesis (McKee et al, 1997).…”

Effects of fasting and refeeding on the antioxidant system in cockerels and pullets

“…In stress conditions, increased secretion of ACTH, cortisol and noradrenalin (McKee et al, 1997) leads to the reduction of α-tocopherol, retinol and GSHPx activity in the plasma and in blood cells (Sconberg et al, 1993), and to an increase in the rate of lipid peroxidation in the blood plasma and tissues after vigorous formation of free radicals (Teeter and Belay, 1996). However, the antioxidant defence system has many components, and a deficiency in any of these components can cause a reduction in the overall activity of the antioxidant system.…”

Efeitos do estresse térmico por calor sobre os índices zootécnicos, a integridade do trato intestinal e a imunidade inata em frangos de corte

“…Ainda, nesta linha de pensamento, a redução no consumo alimentar em função do estresse por calor já havia sido descrita por outros autores (MCKEE et al, 1997;KIRUNDA et al, 2001). Podemos ainda citar outros estudos que mostraram ser o aumento de temperatura (42±3ºC) por 12 horas e por 6 dias em galinhas poedeiras com 31 semanas de vida, capaz de diminuir o ganho de peso e o consumo de ração em relação a animais de um grupo controle (24 a 26ºC) (ROZENBOIM et al, 2007).…”