Incidence of ascites syndrome and related hematological response in short-term feed-restricted broilers raised at low ambient temperature

Abstract

Ascites is a major cause of mortality and morbidity in modern broiler production. Reduction of early growth, followed by compensatory gain, seems a practical and viable method to minimize losses caused by ascites. An experiment was conducted to determine if early feed restriction can reduce the incidence of ascites in broilers exposed to cool temperatures. Ross 308 cockerels (N=180) were assigned to 5 diet treatments and 2 temperature regimes, with 3 replicate pens of 6 birds per treatment and temperature. A standard grower diet was diluted by adding rice hulls at 0, 15, 30, 45, and 60% by weight from 7 to 14 d of age. On d 21 through 42, the temperature was maintained at 20 to 25°C (thermoneutral), or at 11 to 15°C (cool). Broilers exposed to cool temperatures developed higher right ventricle (RV) to total ventricle (TV) and RV to BW ratios, increased plasma triiodothyronine (T3) and thyroxine (T4) concentrations, and elevated blood values for hemoglobin concentration, mean cell volume, and hematocrit (P<0.05) but did not develop clinical ascites. Diluting the feed with rice hulls from d 7 to 14 resulted in proportional reductions in BW by d 14 (P<0.001) that tended to persist through d 28 (P=0.005), after which compensatory growth eliminated all differences in BW between diet treatment groups by d 35 (P=0.099) and d 42 (P>0.1). Exposure to cool temperatures increased key indices of ascites susceptibility, and these preascitic changes were partially prevented by diluting the feed to reduce growth performance.

Impact of Reduced Dietary Crude Protein in the Starter Phase on Immune Development and Response of Broilers Throughout the Growth Period

“…No significant differences were noted across bursa, thymus, spleen, or femur, suggesting no deficiency in those nutritional components that are required for proper development of lymphoid organs. This is consistent with previous research that showed that moderate decrease in CP level (range between 18 and 23%) had no effect on bursa, thymus, and spleen weight ( 19 , 28 , 29 ).…”

“…Broilers fed an RCP diet tended to have lower body weight gain between d 1 and d 28 but compensated between d 28 and d 35 ( Table 3 ). This is consistent with previous research which has shown that reduced protein starter phase diets do not have a negative impact on performance, and also, lower body weight will be compensated after the fourth week ( 19 , 21 , 22 ). This is also consistent with prior reports which point to specific amino acid supplementation rather than CP as most critical to broiler performance.…”

“…Chickens that did not receive an injection were used as a negative control (0 h birds). Blood total leukocytes were counted in a hemocytometer chamber using Natt and Herrick's solution to obtain a 1:200 blood dilution ( 19 ).…”

“…Changes in the endocrine system and metabolic activities, which is directly influenced by diet, have been shown to affect immune status (37). Many components in the endocrine system, including growth hormone, thyroid hormones, and corticosterone levels, can be regulated under protein or energy restriction condition (19,37,38). Additionally, it has been demonstrated that heterophil release from bone marrow to the circulatory blood are enhanced under corticosterone stimulation (39).…”

Betaine and Antioxidants Improve Growth Performance, Breast Muscle Development and Ameliorate Thermoregulatory Responses to Cyclic Heat Exposure in Broiler Chickens

“…For the first seven days of the experiment, the temperature of both rooms was a constant 33 °C for the full 24 h in each day. From day 8, the temperature in each room was either TN where the temperature was decreased gradually from 33 °C to 25 °C on 21 days (one degree every two days starting from day 7) and then maintained at 25 °C from 21–42 days, which is in the range of the optimum temperature for Ross-308 broiler chickens [ 28 ] or HS conditions. The HS conditions were characterized as cyclic 33 °C from 1–42 days where the chickens were kept at 33 °C between 08:00 to 17:00 h and then the prevailing temperature in the TN room for the rest of the day.…”