BACGROUNDS: Heat stress causes the lower performance in broiler chickens. OBJECTIVE: This research was conducted to investigate the effect of betaine supplementation in broiler chickens under heat stress condition. METHODS: Two hundred one-day-old male broiler chicks (Ross 308) were used in a completely randomized design with 4 treatments and 5 replicates per treatment and 10 birds per each replicate. The experimental treatments were the heat stressed birds fed the different levels of 0.0 (without any dietary supplement), 0.05, 0.1 and 0.2% betaine. The experimental diets were added to the diets during the finisher period (day 25 to 42 of age) and under heat stress condition (32±1º C from 9.00 AM to 5.00 PM). RESULTS: The results showed that feed consumption was not affected by betaine supplementation. Consumption of 0.2% betaine resulted in a higher weight gain during the whole period as compared to 0.05 betaine and control diet (P<0.05). The consumption of all betaine levels caused the decreased feed conversion ratio during the finisher period (P<0.05) and 0.2% betaine resulted in lowest feed conversion ratio between the experimental treatments. Dietary betaine supplementation had no effect on internal organ weights of heart, liver, abdominal fat, spleen and bursa at day 42 of age (P>0.05). Furthermore, consumption of different betaine levels had no effects on blood indices, the amounts of blood enzymes and antioxidant status at day 42 of age (P>0.05). CONCLUSIONS: Totally, the consumption of 0.2% betaine improves the performance without any effects on blood indices and internal organs under heat stress condition.

BACKGROUND: Heat stress reduces the poultry performance through physiologic changes. OBJECTIVES: This experiment was conducted to evaluate the effects of different levels of tryptophane on performance, carcass characteristics and some blood parameters of broiler chickens under heat stress condition. METHODS: Two hundred and fifty one-day-old broiler chicks (Ross 308) were used in a completely randomized design with four treatments and five replicates (pen), 10 birds in each replicate. The chickens of experimental treatments were fed basal diet (control group) and the diets plus the different levels of 100, 120 and 130 and 140% of the Ross strain tryptophane requirements. The experimental diets were used during the finisher period (day 25 to 42 of age) and under heat stress (32±1 ºC as cyclic from 9.00 AM to 5.00 PM). RESULTS: The results showed that the weight gain was  increased linearly by increasing the tryptophane level to 110% of Ross requirements but increasing the tryptophane level to 120, 130 and 140% caused the deteriorated weight gain (p<0.05). The feed conversion ratio was linearly decreased during the finisher and whole the period by supplementation of tryptophane to 110 and 120% but the higher tryptophane levels (130 and 140%) increased the feed conversion ratio during these two periods (p<0.05). Increasing the tryptophane level to 130% of Ross requirements caused a linear increase in the amount of lactate dehydrogenase, alanine amino transferase and alkaline phosphatase (p<0.05). Dietary supplementation of tryptophane had no effect on the blood urea, protein, creatinine, albumin, glucose and cholesterol at day 42 of age but triglyceride (p>0.05). Increasing the tryptophane level to 140% caused the lower blood triglyceride content (p<0.05). CONLUSIONS: Totally, the results of recent experiment show that consumption of 110 and 120% tryptophane of Ross requirements is the best level for performance improvements in broiler chickens under heat stress.

BACKGROUND: The application of medicinal herbs with high anti-oxidant properties could reduce the detrimental effects of oxidative stress and free radicals under heat stress and improve the performance of broilers. OBJECTIVES: The effects of rosemary powder and extract on growth performance, carcass characteristics and blood parameters of broilers were evaluated under heat stress. METHODS: For studying the effect of experimental treatments including control, different levels of rosemary powder (5, 10 and 15 g/kg), rosemary extract (3.5,7 and 10.5 g/kg) and Vit-Asp (1 g/L) on growth performance (feed intake, body weight and feed conversion ratio), carcass characteristics and blood parameters (cholesterol, triglyceride, hematocrit, glucose and heterophil to lymphocyte ratio), 160 one-day old chicks (Ross male-308) were used applying a randomized complete block design with 8 treatments, 4 replicates and 5 chicks per replicate during a 42-day period. Heat stress schedule was 32±2ºC as cyclic from 10.00 AM to 6.00 PM. RESULTS: Rosemary had significant effects on feed intake and final live weight of chicks (p<0.05) but not on feed conversion ratio (p>0.05). Significant effects from rosemary on glucose and heterophil to lymphocyte ratio were found (p<0.05). The effects of rosemary on carcass characteristics, cholesterol, triglyceride and hematocrit were not significant (p>0.05). CONCLUSIONS: In general, inclusion of rosemary in broilers diet under heat stress improved the performance because of anti-oxidant effects.Keyword: Rosemary, performance, blood parameters, heat stress, broilers

The aim of this study was to determine the effects of severe extreme thermal stress on the respiratory rate (panting) of unsheared and sheared rams in standing and lying position, and to analyse two temperature-humidity indices (THIs). Six mature Australian Merino rams from Northern Patagonia, three unshorn and three shorn, were subjected to 40 hours (8 hours each day for five days) of gradual increase in temperature from 25°C to 40°C, guaranteeing 4h daily at 40°C in a heat chamber. Respiratory rate (RR) was registered continuously by counting flank movements, and the ambient air temperature and relative humidity were recorded every five minutes inside the heat chamber. From 1413 RR measurements, descriptive and modelling analyses were performed. Panting as a response variable was distributed into five categories, and fixed effects such as THI, wool (unshorn/shorn), and position (standing/lying) were considered. No significant differences were observed between the panting score in the unshorn (standing or lying) and standing (unshorn or shorn) sheep, but significant differences were observed in shorn and lying rams. The explanations could be that heat production from muscle activity was lower and the transfer and heat lost by conduction to the floor was easier in the rams with shorter fleece (at least 0.7 inches long). However, in the unshorn rams, their wool acted as an insulator, both with air as well as the floor. Australian Merino rams from Northern Patagonia are heat tolerant to an environment between 31.5°C and 42°C, and 32% to 48% humidity for 40 hours over five days. The rams were in the first phase of panting, and the normal rectal temperatures registered daily when leaving the heat chamber confirmed that regulation of body temperature was possible. The LPHSI’s THI was adjusted to improve the analysis of the RR more than the National Research Council’s THI.

OBJECTIVE To determine whether infrared thermographic images obtained the morning after overnight heat abatement could be used as the basis for diagnostic algorithms to predict subsequent heat stress events in feedlot cattle exposed to high ambient temperatures. ANIMALS 60 crossbred beef heifers (mean ± SD body weight, 385.8 ± 20.3 kg). PROCEDURES Calves were housed in groups of 20 in 3 pens without any shade. During the 6 am and 3 pm hours on each of 10 days during a 14-day period when the daily ambient temperature was forecasted to be > 29.4°C, an investigator walked outside each pen and obtained profile digital thermal images of and assigned panting scores to calves near the periphery of the pen. Relationships between infrared thermographic data and panting scores were evaluated with artificial learning models. RESULTS Afternoon panting score was positively associated with morning but not afternoon thermographic data (body surface temperature). Evaluation of multiple artificial learning models indicated that morning body surface temperature was not an accurate predictor of an afternoon heat stress event, and thermographic data were of little predictive benefit, compared with morning and forecasted weather conditions. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated infrared thermography was an objective method to monitor beef calves for heat stress in research settings. However, thermographic data obtained in the morning did not accurately predict which calves would develop heat stress later in the day. The use of infrared thermography as a diagnostic tool for monitoring heat stress in feedlot cattle requires further investigation.