RESUMEN
A hypothesis was tested that eggshell temperature manipulations during incubation and in ovo injection of thyroxine (T4) would help their progeny chicks to better survive the ascites-inducing condition during the growing period. In experiment 1, a total of 4,800 hatching eggs was randomly arranged in a 2 × 4 factorial design (8 replicates of 75 eggs per treatment), in which the eggs were incubated at a constant eggshell temperature (EST) of 37.8°C throughout the incubation period (CON) or were exposed to 15°C for one h on d 11, 13, 15, and 17 of incubation (EST manipulations; ESTM), and 4 treatment groups of 3 control groups (no injection; INJN, needle pricked; INJP, and sterilized distilled water injection; INJW) and one T4 treatment group (injected with sterilized distilled water containing 65 ng of T4; INJT4). In experiment 2, 240 one-day-old male broiler chicks from 2 temperature conditions and injection (INJN and INJT4) treatment groups were reared for 42 d in a completely randomized design with a 2 × 2 factorial arrangement. To induce ascites, all chicks were exposed to a 15°C room temperature from 14 d onwards. Results from experiment 1 showed that second-grade chicks and yolk sac weight were decreased, and body weight at hatch was increased in the ESTM and INJT4 groups. Also, final body weight was increased in the ESTM group. Ascites mortality rate was decreased in the ESTM and INJT4 groups. In the ESTM and INJT4 groups, the red blood cell (RBC) and the packed cell volume (PCV) count were decreased. In conclusion, the results showed that the ESTM and INJT4 treatments during incubation were associated with improved chick quality, productive performance of broilers, and a decreased incidence of cold-induced ascites in broiler chickens.
Asunto(s)
Ascitis/veterinaria , Pollos , Frío , Cáscara de Huevo/fisiología , Óvulo/fisiología , Enfermedades de las Aves de Corral/prevención & control , Tiroxina/administración & dosificación , Animales , Ascitis/epidemiología , Ascitis/etiología , Ascitis/prevención & control , Incidencia , Inyecciones/veterinaria , Irán/epidemiología , Masculino , Enfermedades de las Aves de Corral/epidemiología , Enfermedades de las Aves de Corral/etiologíaRESUMEN
An experiment was conducted to evaluate the effects of a periodically low eggshell temperature exposure during incubation and dietary supplementation of arginine on performance, ascites incidence, and cold tolerance acquisition in broilers. A total of 2,400 hatching eggs were randomly assigned to 2 treatment groups (16 replicates of 75 eggs per treatment). The eggs were incubated at a constant eggshell temperature (EST) of 37.8ºC throughout the incubation period (CON) or were periodically exposed to 15°C for one hour on days 11, 13, 15, and 17 of incubation and the EST was measured (periodical low EST; PLE). After hatching, 240 one-day-old male broiler chicks from both treatment groups were reared for 42 d with or without dietary arginine supplementation in a completely randomized design with a 2 × 2 factorial arrangement. In order to induce ascites, all chicks were exposed to a 15°C room temperature from 14 d onwards. Results showed that second grade chicks and yolk sac weight were decreased, and final body weight was increased in the PLE group. Ascites mortality rate was decreased only in the PLE group and dietary arginine supplementation had no apparent effect. In the PLE group, the packed cell volume (PCV) percentage and red blood cell (RBC) count were decreased. In conclusion, the results showed that the PLE treatment during incubation was associated with improved hatchability, chick quality, and productive performance of broilers and decreased ascites incidence during post hatch cold exposure. Dietary arginine supplementation had no beneficial effects in cold exposed broilers.
Asunto(s)
Arginina/metabolismo , Ascitis/veterinaria , Pollos , Frío , Suplementos Dietéticos , Termotolerancia , Alimentación Animal/análisis , Animales , Arginina/administración & dosificación , Ascitis/etiología , Dieta/veterinaria , Cáscara de Huevo/fisiología , Incidencia , Masculino , Enfermedades de las Aves de Corral/etiologíaRESUMEN
The extent to which reduced feed intake contributes to decreased growth during heat stress (HS) in the ovine model is not clear. To evaluate the impact of decreased DMI on performance, we conducted an experiment on growing lambs experiencing a cyclical but extensive heat load. Sixteen intact male Afshari lambs (40.1 ± 1.9 kg) were used in a completely randomized design in 2 periods. In period 1, all 16 lambs were housed in thermal neutral (TN) conditions (22.2 ± 3.1°C and a temperature-humidity index [THI] of 67.9 ± 3.2) and fed at libitum for 8 d. In period 2 (P2), which lasted 9 d, 8 lambs were subjected to a cyclical HS condition (33.0 to 45.0°C and a THI of more than 80 at least for 24 h/d and more than 90 for 8 h/d). The other 8 lambs were maintained in TN conditions but pair-fed (pair-fed thermal neutral [PFTN]) to the HS lambs. During each period, DMI and water intake were measured daily. Respiration rate, rectal temperature, and skin temperature at the shoulder, rump, and front and rear leg were recorded at 0700 and 1400 h daily. Dry matte intake declined (17.5%; P < 0.01) in HS lambs and, by design, the temporal pattern and magnitude of reduced feed intake was similar in the PFTN controls. Water intake increased (19%; P < 0.05) during P2 in HS but not in the PFTN controls. Heat stress increased the 0700 and 1400 h skin temperature at the shoulder (5 and 9.2%), rump (6.2 and 10.3%), rear (6 and 9.2%), and front leg (6.5 and 9.8%) and respiratory rates (84 and 163% [P < 0.01]at 0700 and 1400 h, respectfully), but only the 1400 h rectal temperature was increased (P < 0.01; 0.65°C) in HS lambs. Neither environment nor period affected blood urea nitrogen and glucose concentrations. However, circulating NEFA and insulin were increased and declined (P < 0.01) in PFTN lambs, respectively, but neither variable was altered in the HS lambs. Growth was reduced in P2 for lambs in both treatments, but despite being on a similar reduced plane of nutrition, the HS lambs' ADG was more than 2-fold greater than the PFTN controls. These results indicate that HS markedly alters the energetics of weight gain during growth and that the effects of HS are dependent on the severity of the heat load.