This study was conducted to determine whether early age feed restriction improves heat tolerance in female broiler chickens. Chicks were brooded for 3 wk and then maintained at 24+/-1 C. On Day 0, chicks were assigned to one of four feeding regimens; each regimen was applied to four cages of chicks. The feeding regimens were 1) ad libitum feeding (ALF); 2) 40% feed restriction at 4, 5, and 6 d of age (F40); 3) 60% feed restriction at 4, 5, and 6 d of age (F60); and (4) 80% feed restriction at 4, 5, and 6 d of age (F80). From 35 to 41 d of age, all birds were exposed to 38+/-1 C for 2 h/d. Serum concentrations of glucose were elevated by the heat challenge, but were not affected by the feeding regimen. The heat treatment resulted in hypocholesteremia among ALF and F80 chicks, whereas the concentrations increased and remained constant in the F60 and F40 birds, respectively. Subjecting chicks to F60 improved growth and survivability and reduced heterophil to lymphocyte ratios (H/L) in response to the heat treatment as compared with the ALF and F80 regimens. The survivability rate and H/L of F40 chicks were similar to those attained by chicks on other regimens. Newcastle disease antibody titer of ALF birds declined with duration of heat treatment. It is concluded that the F60 regimen is beneficial for alleviating, at least in part, the detrimental effects of heat stress in female broiler chickens.
Stress and fear responses were evaluated in broiler chicks that were pretreated for 24 h with 0 ppm (control) or 1,200 ppm of L-ascorbic acid (AA) in their drinking water. The birds were subsequently subjected to either upright handling (UH) or inverted (IH) handling for about 45 s. Heterophil (H) counts, lymphocyte (L) counts, and H/L ratios (H/L) ratios were determined immediately (T0) and at 20 h (T20) following the handling treatment. The H/L ratios were similar for both groups at T0, whereas 20 h after the handling treatment, AA-supplemented birds had lower ratios than controls, resulting in a significant water treatment x time of blood sampling interaction. Inverted handling had negligible effect on H/L ratios but augmented tonic immobility (TI) durations as compared with UH. Irrespective of handling procedure, supplemental AA reduced underlying fearfulness, as measured by TI reaction. Neither water treatment nor handling method had significant effect on number of attempts to induce TI.
1. This study was conducted to determine the effect of early-age food restriction on heat shock protein (hsp) 70 synthesis in the brains of female broiler chickens exposed to high ambient temperatures. 2. Chicks were brooded for 3 weeks and then maintained at 24+/-1 degrees C. 3. On d 0, chicks were assigned to one of 4 feeding regimens; each regimen was applied to 4 cages of chicks. The regimens were: (1) ad libitum feeding (AL); (2) 80% food restriction at 4, 5 and 6 d of age (F80); (3) 60% food restriction at 4, 5, and 6 d of age (F60); and (4) 40% food restriction at 4, 5 and 6 d of age (F40). From d 35 to d 41, all chicks were subjected to 38+/-1 degrees C for 2 h/d. 4. One day following food restriction (d 7), hsp 70 expression in the brain samples of F60 and F40 chicks was augmented but not those fed AL and F80. 5. Prior to the heat challenge (d 35), all chicks had similar hsp 70 response. Irrespective of feeding regimen, there was a marked increase in hsp 70 expression after 4 d of heat treatment (d 38). Following 7 d of heat exposure (d 41), except for the F60 chicks, the augmented hsp 70 expression in the brains of AL, F80 and F40 birds was not maintained. 6. Enhancement of hsp 70 expression was noted in birds subjected to F60, but not AL, F80 or F40, throughout the period of heat exposure.
Zulkifli, I., Dass, R. T. and Che Norma, M. T. 1999. Acute heat-stress effects on physiology and fear-related behaviour in red jungle fowl and domestic fowl. Can. J. Anim. Sci. 79: [165][166][167][168][169][170]. Two experiments were conducted to compare heat tolerance of red jungle fowl (RJF) and commercial broilers (CB) at (i) a common age and (ii) a common body weight. In exp. 1, RJF and CB of a common age (8 wk) were exposed to 36 ± 1°C for 6 h. RJF had smaller increases in heterophil to lymphocyte ratios and body temperature and higher serum cholesterol concentrations than CB in response to the heat treatment, while tonic immobility (TI) measurements were not affected by heat stress. In exp. 2, RJF and CB of a common body weight (1000 ± 150 g) were subjected to similar procedures as in exp. 1 (except TI durations). Both breeds responded similarly to the heat treatment. In both experiments, RJF had higher serum glucose level than CB, and the trait was not affected by heat exposure. Deux expériences ont été réalisées pour comparer la tolérance à la chaleur des galliformes rouges d'Asie (GRA) et des poulets de chair de production commerciale (PC) à un même âge et à un même poids corporel. Dans l'expérience 1, les GRA et les PC du même âge (8 semaines) étaient exposés à une température de 36 ± 1°C pendant 6 h. Les GRA manifestaient des accroissements moins importants du rapport hétérophiles-lymphocytes et de la température corporelle ainsi qu'une plus forte concentration sérique de cholestérol que les PC en réponse au traitement thermique. Par ailleurs, les valeurs d'immobilité tonique (IT) n'étaient pas touchées par le stress thermique. Dans l'expérience 2, les GRA et les PC de poids corporel comparable (1 000 ± 150 g) étaient exposés aux mêmes conditions que dans l'expérience 1, excepté pour la durée de IT. Les deux types de volaille réagissaient de la même façon au traitement thermique. Dans les 2 traitements les GRA avaient un niveau sérique de glucose plus élevé que les poulets domestiques et ce caractère se maintenait en présence de stress thermique.
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