Insensibilização de frangos de corte em atmosfera controlada na promoção do bem estar animal: Diego Augusto Bitencourt. -

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Incubation and rearing temperature effects on Hsp70 levels and heat stress response in broilers

Incubation temperature (IT) was changed to evaluate if 6-wk-old birds become more tolerant to heat stress. After 13 d of incubation, 470 eggs were submitted to low (36.8degreesC), normal (37.8degreesC) and high (38.8degreesC) temperatures. At day 7 post-hatching, 144 birds were allocated to three rearing temperatures (48 birds/treatment): control/thermoneutral (35-24degreesC), high (33-30degreesC) or low (27-18degreesC) according to the age of the birds. Hsp70 levels in tissues of birds (1 d and 42 d), stress response (42 d) and performance were evaluated. High IT decreased brain (P < 0.01) and liver (P < 0.01) Hsp70 levels, whereas low IT decreased brain (P < 0.01) but increased heart (P < 0.01) Hsp70 levels in 1-d-old chicks. Birds incubated at a low temperature had higher (P < 0.05) feed intake (1-42d). High rearing temperature decreased feed intake (P<0.01) and liveweight (P<0.01). Colonic temperature was lower in birds incubated at a low temperature (P < 0.05) and higher in birds reared in a high temperature (P < 0.05) before heat stress. Birds reared in low temperature had higher increase in colonic temperature after heat stress (P < 0.05). Tissue Hsp70 levels were differently affected by rearing temperature, which affected broiler performance more than IT. Lower IT seemed to increase the sensitivity of birds to heat stress at market age.

Intestinal and pancreas enzyme activity of broilers exposed to thermal stress

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of acute heat stress on heat shock protein 70 messenger RNA and on heat shock protein expression in the liver of broilers

1. The synthesis of heat shock protein 70 (Hsp70) mRNA and the expression of Hsp70 in the liver of broiler chickens submitted to acute heat stress (35 degrees C for 5 h) was investigated.2. Hsp70 expression was detected by SDS-PAGE and Western blot analysis using a polyclonal antiserum against Hsp70 of Blastocladiella emersonii. The specific signal of Hsp70 mRNA was analysed by Northern blot using as probe a Hsp70 cDNA of B. emersonii.3. An increase in the amount of Hsp70 was detected from the first up to the fifth hour of acute heat exposure. This increase in the amount of Hsp70 was accompanied by an increase in Hsp70 mRNA which peaked at 3 h.4. This study shows that the heat induced increase in Hsp70 mRNA and protein in broiler liver, in vivo, are time dependent, similar to that in mammals.

Effect of thermal conditioning during embryonic development on aspects of physiological responses of broilers to heat stress

The purpose of the present study was to investigate the effect of thermal conditioning, (through exposure to heat stress), during pre-hatch development on some physiological responses of post-hatch broilers to a post-natal heat stress challenge. Exposure to heat stress at this stage, we hope, may possibly induce epigenetic heat adaptation. Incubating eggs were exposed to temperature of 39.0degreesC for 2 h from Day 13 to 17 of incubation. At 33, 35, 37, 39, 41 and 43 d of age, the broilers hatched from these eggs were housed individually in open-circuit respiration cells. The climatic chambers were set to 22degreesC and increased to 30degreesC for 4 h. O-2 consumption and CO2 production of each chicken was monitored continuously in order to calculate the heat production. Blood samples were obtained before and during the 4 h heat stress. Thermal conditioning during incubation did not affect the plasma T-4, corticosterone, glucose, uric acid and CK concentrations. Temperature challenge, decreased plasma T-3 of broilers of both groups but the decrease was greater in pre-conditioned broilers compared with controls. A similar trend was observed for triglycerides. These changes did not affect total heat production. Since decreased T3 and triglyceride levels are part of the mechanisms for thermoregulation, these suggest that thermal conditioning during incubation can improve the broiler chicken capability for thermotolerance at later post-hatch age. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Influence of Dietary Lysine Levels and Arginine:Lysine Ratios on Performance of Broilers Exposed to Heat or Cold Stress during the Period of Three to Six Weeks of Age

Four trials of identical experimental design were conducted to determine the effects of temperature, dietary Lys level, and dietary Arg:Lys ratios on performance and carcass yield of male broilers. Birds of a commercial strain were grown from 21 to 42 d of age in wire-floored finishing batteries placed in environmental chambers. The chambers were programmed to provide either a constant thermoneutral temperature (21.1 C), a constant cold temperature (15.5 C), or a cycling hot diurnal temperature (25.5 to 33.3 C). Within each environment there was a factorial arrangement of three Lys levels (1.0, 1.1, and 1.2%) with four Arg:Lys ratios (1.1:1, 1.2:1, 1.3:1, and 1.4:1). Environmental temperature significantly influenced virtually every characteristic examined. Hot cyclic temperatures reduced weight gain, feed intake, and breast meat yield, and increased feed conversion, dressing percentage, leg quarter yield, and abdominal fat content. The cold environment promoted increased feed intake and mortality. Ascites and cardiomyopathy were the leading causes of death under cold exposure and thermoneutral conditions, whereas complications arising from heat exposure were the main cause of death under hot cyclic conditions. Levels of Lys affected leg quarter yield and abdominal fat content over all environments but increased breast meat yield only under cold conditions. Increasing Arg: Lys ratios improved feed conversion and dressing percentage and reduced abdominal fat content; it could not be determined whether these responses were consistent with Arg per se or were due to a nonspecific N response. As increasing Lys levels or Arg:Lys ratios did not improve weight gain, increase breast meat yield, or attenuate adverse effects due to heat or cold exposure, it is concluded that the levels of Lys and Arg suggested for 21 to 42 d by the NRC are adequate for birds of this age under the environmental conditions encountered.

Effect of dietary betaine supplementation on the performance, carcass yield, and intestinal morphometrics of broilers submitted to heat stress

The objective of this study was to evaluate the effect of betaine in methionine- and choline-reduced diets fed to broilers submitted to heat stress. In total, 1,408 male broilers were randomly distributed into eight treatments, according to 2 × 4 (environment x diet) factorial arrangement, with eight replicates of 2 birds each. Birds were reared environmental chambers under controlled temperature (25-26 °C) or cyclic heat-stressing temperature (25-31 °C). The following diets were tested: positive control (PC), formulated to meet broiler nutritional requirements; negative control (NC), with reduced DL-methionine and choline chloride levels; and with two supplementation levels of natural betaine to the negative control diet (NC+NB1 and NC+NB2). Live performance, carcass traits, and intestinal morphometrics were evaluated when broilers were 45 days of age. The results showed that all evaluated parameters were influenced by the interaction between environment and diet, except for breast meat drip loss. The breakdown of the interactions showed that birds fed the PC diet and reared in the controlled environment had greater breast drip loss than those submitted to the cyclic heat-stress environment. Birds submitted to cyclic heat stress and fed the PC diet presented the lowest feed intake. Feed conversion ratio was influenced only by diet. The FCR of broilers fed the NC+NB2 diet was intermediate relative to those fed the PC and NC diets. The addition of betaine in the diet, with 11.18% digestible methionine and 24.73% total choline reductions, did not affect broiler live performance, carcass yield, or intestinal morphometrics.

The strategic application of elecytolyte balance to minimize heat stress in broilers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Strategic feed formulation for relation of electrolytes to promote performance and prevent heat stress in broilers

An experiment was conducted to evaluate the impact in relation of dietary electrolytes, based on changes in the balance Na+K-Cl (DEB) and the ratio (K+Cl)/Na (DER) on the performance and survival of broilers subjected to acute heat stress. A total of 1575 male broiler chicks from 1 to 46 d of age were allocated in a 5x3 factorial arrangement in a completely randomized design, totaling of 15 treatments with 3 replicates of 35 birds each. The treatments consisted of 5 diets with electrolyte balances, arising from combinations DEB/DER (150/3, 250/2, 250/3, 250/4 and 350/3), associated with different times of application or not of the acute heat stress on birds at 25 and 36 d old. All diets were cornsoybean meal based and formulated to meet or exceed NRC requirements. Chicks had ad libitum access to feed and water in floor pens with wood shavings as litter. It was possible to verify that a DEB of 250 mEq/kg and a DER very close to the 3:1 providing a more nutritionally adequate diet. There was, however, the impossibility of obtaining a more suitable electrolyte ratio for a very low DEB (150 mEq/kg) or very high (350 mEq/kg) and also, to a very narrow DER (2:1) or very wide (4:1), due to an unfavorable performance and survival rate of birds in these conditions electrolytes adjustments of K, Na and Cl. There was clear indication, with significant difference (P < 0.05), that the DER has the potential to improve the performance of broilers, since simultaneous adjustment made in DEB, even in conditions of acute stress. The results of performance and survival rate of this study also indicate clearly that DER could not replace the DEB, and vice versa, in practical diets for broilers. Therefore, it can be affirmed that the strategic formulation of the correct electrolyte balance for DEB and DER enhances the performance and is able to prevent the effect of heat stress in broiler chickens, leading to better performance and survival.

Dietary electrolytes and thermal conditioning: minimizing heat stress in broilers

In tropical climates the heat is one of the major constraints to production of broilers and is responsible for inducing a high mortality, especially in the finishing phase. Thus, the objective of this study was to compare the thermal conditioning early (TC) and feed formulation using dietary electrolytes (DE). Therefore, the electrolyte balance of K+Na-Cl was set at 350 mEq/kg and electrolyte ratio (K+Cl)/Na) in the 3:1 program PPFR (http://www.fmva.unesp.br/ppfr). A total of 300 Cobb 500 1-dold male broiler chicks was randomly allocated to 24 floor pens with six replicates per treatment in a 2x2 factorial arrangement (with and without TC and with and without DE). Dietary treatments consisted: (T1) a traditional diet without TC; (T2) traditional diet with TC; (T3) with the application of dietary electrolyte and without TC and (T4) application of dietary electrolyte with TC. The thermal conditioning was conducted at 5 d of age (36°C for 24 h), only half of the batch (150 birds). After this period, all birds were transferred to boxes of 1.5 x3m (12 birds / box), with wood shavings reused as litter. Chicks were exposed to acute stress (36°C) for 8 h at the age 36, in all treatments, being electronically monitored the temperature and humidity of the microclimate of the birds. Feed and water were provided ad libitum, even during periods of stress. Were measured performance data (weight gain, feed intake and feed conversion) and mortality rate. The early thermal conditioning (T2) and effect of dietary electrolytes (T3) were effective to minimize the mortality of broilers subjected to acute heat stress with a significant difference (P<0.05), without prejudice on broiler performance. The results also showed that there was a more favorable effect when applied dietary electrolytes and thermal conditioning simultaneously (treatment T4). However, for the treatment none of these strategies has been applied (T1), the mortality rate was 83% over that in which they were applied (T4). It was concluded from this study that both techniques: the thermal conditioning early as the dietary electrolytes are efficacious in minimize the damaging effects caused by heat broiler.

Strategies to minimize heat stress in broilers chickens

The objective of this study was to evaluate the application of early age thermal conditioning (TC) and dietary electrolyte balances (DEB) to minimize the effect of heat stress. A total of 240 Cobb 500 1-d-old male broiler chicks was randomly allocated to 24 floor pens with six replicates per treatment in a 2x2 factorial arrangement (with and without TC and with and without DEB). Dietary treatments consisted: (T1) a traditional diet without TC; (T2) traditional diet with TC; (T3) with the application of dietary electrolyte and without TC and (T4) application of dietary electrolyte with TC. The thermal conditioning was conducted at 5 d of age (36°C for 24 h), only half of the batch (120 birds). After this period, all birds were transferred to boxes of 1.5 x 3m (10 birds / box), with wood shavings reused as litter. Chicks were exposed to chronic heat stress (32°C) for 6 h from 35 to 39 d of age, in all treatments, being electronically monitored the temperature and humidity of the microclimate of the birds. Feed and water were provided ad libitum, even during periods of stress. Were measured performance data (weight gain, feed intake and feed conversion) and mortality rate. Data were subjected to ANOVA using the GLM procedures of SAS. The results of this study demonstrated no interaction effects of all evaluated parameters (performance and mortality). Therefore, no synergism occurred when both strategies (TC and DEB) were applied. Only the first week there was prejudice on broiler performance with the application of the TC and apparently the technique of early age thermal conditioning no improve the resistance of broilers to chronic heat stress. On the other hand, DEB had significantly favorable effects (P<0.05) on performance and minimized mortality immediately after application of the TC.

Characterization of heat waves affecting mortality rates of broilers between 29 days and market age

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Hepatic concentration of heat shock protein 70 kD (Hsp70) in broilers subjected to different thermal treatments

1. The relationship between repeated thermal treatments and hepatic synthesis of Hsp 70 was studied in broiler chickens.2. Sixty broilers were submitted to 5 different treatments (12 birds each) from day 1 to day 42. Four groups were kept in a thermoneutral environment and subjected to 0, 1, 2 and 3 heat stress episodes at 35 degrees C for 4 h per week (TN-0, TN-1, TN-2 and TN-3, respectively). The last group (HT-35) was reared at a room temperature of 35 degrees C.3. From 39 to 42 old, the birds experienced acute heat stress at 41 degrees C. Resistance to heat stress was evaluated by the time taken for rectal temperature to increase by 3 degrees C above the pre-treatment value. Livers were collected (before and after heat stress) and Hsp70 was determined using Western Blot analysis with monoclonal anti-Hsp70 antibody.4. Resistance to heat stress and concentration of Hsp70 were higher in those birds subjected to more heat stress episodes during the experimental period (TN-3) and HT-35. A positive correlation was observed between Hsp70 concentration and the time taken for a 3 degrees C increase in rectal temperature (r=0.42; P<0.01).5. Exposing birds to episodes of heat stress (35 degrees C) during rearing may improve their resistance to acute heat stress, but the previous thermal history did not seem to influence the hepatocyte Hsp70 content after exposure to more severe heat stress (41 degrees C).

Performance and carcass characteristics of broiler chickens with different growth potential and submitted to heat stress

In order to evaluate the effects of broiler genotype and of heat exposure on performance, carcass characteristics, and protein and fat accretion, six hundred one-day-old male broilers were randomly assigned in a 2 x 3 factorial arrangement, according to the following factors: genetic group (selected and non-selected broilers) and pair-feeding scheme (Ad(32) - reared under heat stress and fed ad libitum; Ad(23) - reared at thermoneutrality and fed ad libitum; Pf(23) - reared at thermoneutrality and pair fed with Ad(32)), with a total of six treatments with four replicates of 25 birds each. Independent of pair-feeding scheme, selected broilers showed better feed conversion, higher carcass yield, and lower abdominal fat deposition rate. However, as compared to non-selected broilers, they reduced more intensively feed intake when heat exposed, which promoted significant breast-yield decrease, and more pronounced changes on carcass chemical composition. These findings allows concluding that, in both genetic groups, both environmental temperature and feed-intake restriction influence abdominal fat deposition rate and other carcass characteristics; however, the impact of heat exposure on broiler performance is more noticeable on the selected line.

Water intake behavior of broiler chickens exposed to heat stress and drinking from bell or and nipple drinkers

The aspects involved in broiler water intake are not well known, despite the importance of water in animal nutrition and physiology. Water intake behavior should be taken into account when deciding on different types of drinkers. Bell and nipple drinkers are the most commonly used in commercial broiler production. Broilers were housed in cages equipped with two different drinker types and raised at two different environmental temperatures (25 and 34 ºC) to evaluate water intake behavior and volume. Broiler water intake behavior was influenced by drinker type. Birds visited bell drinkers less often, but presented higher total water intake per visit to the drinker as compared to those drinking from nipple drinkers. The results of this study suggest that both broilers drinking behavior and water intake volume should be taken into account when deciding on drinker type to equip broiler houses.