An experiment was conducted to determine whether ascorbic acid (AA) increases resistance of female Hubbard x Hubbard broiler chicks to multiple concurrent stressors. Stressors imposed from 10 to 17 d posthatch included 2 x 2 x 2 factorial combinations of beak trimming [(B), sham-operated or beak-trimmed and cauterized], coccidiosis [(C), gavage with 0 or 3 x 10(5) sporulated Eimeria tenella oocysts], and heat stress [(H), 28 vs 33 C]. A starter diet was supplemented with AA to provide 0, 150, or 300 ppm (milligrams per kilogram). This resulted in a 2 x 2 x 2 x 3 factorial design with two six-chick replicates of each of the 24 treatment combinations. Data were analyzed using ANOVA and a level of 95% significance. Ascorbic acid increased feed intake and lowered plasma corticosterone and heterophil:lymphocyte ratios. Heat depressed weight gain and feed intake and elevated heterophil:lymphocyte ratios. Heat and AA interacted to improve weight gain and feed intake and lower heterophil:lymphocyte ratios. Coccidiosis depressed weight gain, feed efficiency, and heterophil:lymphocyte ratios. Coccidiosis and AA interacted to increase feed intake and lower plasma corticosterone and heterophil: lymphocyte ratios. Beak trimming increase heterophil:lymphocyte ratios. Beak trimming and AA interacted to increase feed intake and lower heterophil: lymphocyte ratios. Weight gain and feed efficiency decreased whereas heterophil:lymphocyte ratios increased linearly in unsupplemented birds as a function of stressor "order" (the number of stressors imposed simultaneously) indicating an additive effect of systematically increasing the number of stressors. No changes in feed efficiency or heterophil:lymphocyte ratios were detected as a function of stressor order when AA was provided. Ascorbic acid reduced the slope of the regression equation describing the relationship between weight gain and stressor order. It was concluded that AA, particularly at 150 ppm, enhanced performance of broiler chicks exposed to multiple concurrent environmental stressors.
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...
A study was conducted to determine whether water-cooled floor perches would be utilized by commercial broilers exposed to a constant hot ambient environment; and subsequently, whether utilization of these perches would improve performance beyond those provided uncooled floor perches. A total of 330 day-old commercial broiler chicks were randomly allocated to six pens (2.44 m2) in an environmentally controlled facility and maintained in a thermoneutral brooding environment for 16 days. Following this period, 240 birds were selected on a body weight basis and randomly assigned to the six pens. A perch constructed from steel pipe (2.44 m length, 5.0 cm diameter) was then placed diagonally on the litter covered floor of each pen. The birds were first exposed to a thermoneutral period (27.7 C), during which time cooling of the perches in three replicate pens was initiated by circulating tap water. The other three experimental pens received ambient perches. Ambient temperature was then raised to 32.6 C for the following 4 wk. The results of the present study showed that utilization of water-cooled perches by broilers was greater (P less than or equal to .01) than ambient perch utilization throughout the 32.6 C period. Average daily gain was greatest (P less than or equal to .01) for broilers exposed to cool perches. Additionally, they consume more feed (P less than or equal to .05), on a daily basis, than those given ambient perches during the heat-stress period. Broilers exposed to water-cooled perches also had a more efficient gain to feed ratio (P less than or equal to .01). At the completion of the study, final body weight and total body weight gain were greater (P less than or equal to .05) for broilers given water-cooled perches compared with those exposed to ambient perches. Total amount of feed consumed and total feed efficiency were only moderately affected (P less than or equal to .10) by perch treatments. These results indicated that water-cooled perches were beneficial in improving broiler performance during periods of high environmental temperatures.
Pinealectomized (PX), sham-operated (PN), and control (C) cockerels were randomly assigned to three ambient temperatures (7, 23, or 37 C) at eight weeks of age. Rectal temperature (Tr) and blood were taken from birds either at mid-photophase or mid-scotophase (12L:12D) on five different days of the exposure period (0, 4, 8, 12, and 16 days). After 16 days of exposure to different ambient temperatures (Ta), birds were killed and their adrenal and thyroid glands removed. Serum T3 and T4 were measured by RIA in sera taken from PX and PN birds during both phases at each Ta. Pinealectomy depressed (P less than .05) somatic growth at each time measured independent of T3. A consistently lower Tr in PX birds held at 37 C produced an interaction (P less than .01) between pinealectomy and Ta. Across Ta, relative adrenal weights of PX cockerels (13.8 mg/100 g body weight were greater (P less than .05) than the PN and C average (12.7 mg/100 g body weight). There was an interaction (P less than .05) between pinealectomy and ambient temperature on thyroid weight; PX cockerels had smaller thyroids at 23 C and larger thyroids at 37 C than comparable controls. The PX cockerels had an average T3 concentration of 370.6 ng/100 ml compared to 350.5 ng/100 ml for PN birds. The hot environment (37 C) markedly depressed (P less than .01) serum T3 concentrations independent of surgical treatment. In PX cockerels, decreased body weights, lower Tr, and general adrenal enlargement indicate that the avian pineal gland is involved in endocrine function and maintenance of body temperature as well as normal somatic growth.
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