SUMMARY. Two experiments were performed, with male and female broilers separately, to evaluate the effect of early feed restriction on performance, carcass, or

A meta-analysis was developed to model performance depression in heat stress (HS), to analyze the influence of HS type (cyclic or constant), and to assess the correlation between dietary electrolyte balance (DEB) and HS in broilers. Two databases (Dat) with performance and temperature were constructed (initial phase – up to 21 d of age – 14 articles, 7,667 animals, average replicate number treatment-ARN/T, 5 and growing phase – over 21 d of age – 74 articles and 25,145 broilers, ARN/T, 7). The criteria for article selection were (1) experiments using at least 2 temperatures (thermoneutral and high temperature); (2) results of ADFI and ADG; (3) feed and water ad libitum during the experiment. Each treatment was classified as cyclic or constant HS and the HS group response was calculated relative to the thermoneutral group. Performance was evaluated as raw data or as relativized information (indicated as “HS effect or ≠”), expressed as a percentage of the difference between results. The models to predict “HS effect” showed that for the initial phase, only ADG was influenced by HS, while for the grower phase, prediction equations were created for ADFI and ADG. Considering the simplest models, there was a reduction of 1.4% in ADFI and 2.1% in ADG for each unit (°C) above the upper critical temperature for broilers older than 21 d. Feed conversion (FC) was not affected by HS in any of the studied phases. Constant HS proved to be more negative than cyclic HS to broiler performance after 21 d of age. The relation between DEB and performance of broilers under HS was analyzed considering broilers over 21 d of age, and very weak correlations were observed. It was concluded that HS affects broilers over 21 d more, although FC is not affected. ADFI is the most important variable affected by HS and the relation between the DEB of the diet and HS is very weak. The empirical models generated in this study accurately predicted ADG and ADFI of broilers exposed to HS and can be used to minimize those effects on poultry production.

The present study aimed at evaluating the effect of the prebiotic Bio Mos™ (2 kg/ton up to 10 days; 1 kg/ton from 10 to 21 days; and 0.5 kg/ton from 21 days to slaughter), of the probiotic Lac XCL 5x™ (by spray-mixing), of a combination of the two supplements (prebiotic + probiotic), and of one growth promoter antimicrobial agent (Avilamycin at 15 ppm). Birds were orally challenged with inoculated Salmonella Enteritidis (SE) 10(6) CFU at 3 days of age. Four hundred and eighty male Ross chicks were used. The experiment lasted 28 days, and the analyses were conducted at 15 and 28 days of age. Cecum and liver bacterial colonization of production of anti-SE antibiodies, intestinal micrometry and bird performance were assessed. Neither the prebiotic, nor the probiotic influenced performance or production of anti-SE antibodies in SE-challenged birds. Intestinal micrometry and bird mortality were not influenced by prebiotic or probiotic supplementation, or by the antimicrobial agent. The use of an antimicrobial agent produced higher SE CFUs in cecum bacterial counts, while prebiotic and probiotic yielded lower counts. The combination prebiotic+probiotic did not produce significantly different results from the individual use of the additives

The present study aimed at assessing the effects of methionine and arginine on the immune response of broiler chickens submitted to immunological stimuli. Three methionine concentrations (0.31, 0.51, and 0.66% from 1 to 21 days of age; 0.29, 0.49, and 0.64% from 22 to 42 days of age) and 2 arginine concentrations (1.33 and 1.83%; 1.14 and 1.64% for the same life periods) were tested. Birds were divided into two groups for immunological stimuli (3x2x2 arrangement). Vaccines against Marek's disease, fowl pox, infectious bronchitis, Freund's Complete Adjuvant, Sheep red blood cells (SRBC), and avian tuberculin were administered to one group as immunological stimuli; the other group did not receive any stimulus. The experiment was carried out with 432 one-day-old male Ross broilers, distributed into 12 treatments with 6 replicates of 6 birds each. Performance data were weekly collected. Anti-SRBC antibodies were collected by hemagglutination test and cell immune response (CIR) was measured by tubercularization reaction in one wattle 24 hours after administration of the second tuberculin injection at 42 days of age. The weight difference between the two wattles of each bird (one injected with tuberculin and the other not) was the measure of CIR. Arginine levels did not influence either bird performance or immune response. Methionine concentrations higher or lower than usually adopted in broiler production (0.51 and 0.49%) equally failed to influence the birds' immune humoral response, but the best CIR was observed at the intermediate methionine level. Vaccines administered on the first day of age impaired bird performance up to the 21st day of age

We evaluated the effects of a protease supplementation on the growth performance and intestinal health of broilers. Cobb chicks (392; 1-42 d) were divided into four treatments (seven replicates of 14 birds each). There were two feed formulations: a standard diet (SD) and a low crude protein and digestible amino acids diet (Low CP&AA). The two diets were either supplemented (+P) or not (−P) with a protease (Jefo Protease; 1.25 g kg⁻¹). Performance was evaluated by feeding phases (1-7, 8-21, 21-35, and 35-42 d). On day 28, ileum samples were analyzed by a morphometric index for histological alterations (I See Inside Scoring System – ISI). Broilers fed the Low CP&AA had a poor feed conversion ratio (FCR); however, the addition of the protease to the Low CP&AA positively affected FCR and body weight gain and promoted a performance similar to the group fed SD−P. Birds fed diets supplemented with the protease presented the best ISI morphological index, mainly as a result of the low number of alterations regarding the lamina propria, epithelial thickness, and enterocyte proliferation. It is possible to conclude that the enzyme improves feed conversion and lamina propria, epithelial thickness, and proliferation of enterocytes index of broiler chickens when added to a standard diet or with a low crude protein and digestible amino acids diet.

The supplementation of vegetal diets with L-methionine (100% molar), methionine hydroxyl analogue (HMB) (88% molar) or DL-methionine (99% molar) was compared as to the performance of broilers allocated in cages and submitted to cyclic heat stress (CHS). The trial was carried out from 21 to 42 days of age. Two levels of synthetic methionine were supplemented for each methionine source (0.1 or 0.3 %), and the control treatment was not supplemented with synthetic methionine (negative control). Statistical analyses included the negative control treatment or were performed in a 3 x 2 factorial design (sources x levels). Addition of synthetic methionine to the basal level containing 0.63 % of total sulphur amino acids significantly improved feed conversion (FC) independent of the source. On the other hand, improvements in weight gain (WG) and body weight (BW) were more consistent comparing the negative control to HMB-supplemented treatments. Factorial analysis showed better FC for L-Met compared to DL-Met, whereas HMB showed intermediate results. The supplementation level of 0.3% methionine showed better FC than 0.1%. Methionine levels or sources had no effects on carcass, yields of cuts or feathering results. Therefore, results of DL-Met and HMB added to vegetal-based diets in comparable molar terms promoted similar performance in broilers under CHS conditions.