Resumen de Effects of protected sodium butyrate in chickens performance and intestinal health
The relation between nutrition and intestinal health is a subject with an increasing interest in research, as nutritionists need knowledge about what effects formulation may have on different parameters in the gastrointestinal tract (GIT). That is why a series of four trials were conducted to assess the effect of nutrient concentration and of protected sodium butyrate (PSB, Gustor N’RGY® produced by Norel S.A.) addition in poultry diets of varied ingredient composition, on chicken performance, digestive parameters, intestinal morphology and microbiota composition. Experimental diets followed a factorial design with two (trials 1, 2) or three (trials 3, 4) levels of nutrient concentration and addition or not of PSB. Control diets (C) were formulated following nutrient recommendations of NRC or FEDNA and ideal amino acid (AA) profile. The different levels of nutrient concentration were achieved by decreasing 60 kcal ME and 2.3% AA respect to C diets (Reduction 1, R1) or 120 kcal ME and 4.6% AA less than C (Reduction 2, R2). Half of the experimental diets were supplemented with PSB dosed at 1kg/t in the mixer. Diets based on Corn Soy (trials 1, 3) or Wheat Barley Soy (trials 2, 4) were manufactured as mash and supplied ad libitum to chickens for 42 d. The number of replicates per treatment varied from 5 to 8, and the number of chickens per replicate from 7 to 46. Feed consumption and weight of animals were taken at 21 (28 d in trial 4) and 42 d. Subsamples of each replicate were taken at both ages for analyzing the intestinal parameters. The reduction of nutrient concentration produced a decrease in chickens performance in trials 2 and 4. Feed conversion ratio (FCR) impaired 2.5 and 1.9% (P<0.05) with reduction 1 in trial 2 and 4, respectively and 5.6%, (P<0.001) with R2; and final body weight (BW) decreased 2.5 and 5.8% (P<0.001) with R1 and R2 diets respect to control in trial 4. The addition of PSB to diets showed an improvement in animal performance, increasing growth, from 2 to 7%, (P<0.05) in all four trials and mainly in the first weeks of growth. Likewise, FCR of chickens at 21 d. of age improved 2.6 and 3.2% (P=0.09, P<0.01) in trials 1 and 3, respectively, with PSB addition. An interaction PSB addition by nutrient concentration has been observed in trials 1 and 4 (P<0.05), the effect of PSB addition on BW increased with the reduction of nutrient concentration. In fact, animals receiving R1 diets and PSB showed similar performance to those receiving C diets without PSB. Gross energy metabolizability was not affected by nutrient concentration reduction, but increased with PSB addition (69.94 vs 72.55; P= 0.02).
There were scarce effects of treatments on the intestinal microbiology evaluated. The reduction of nutrient concentration tended to decrease E. coli population in the caecum (6.3%, P=0.0572) at day 21 in trial 1. The addition of PSB decreased E. coli concentration by 7.6% in the caecum at day 21 in trial 2 (P=0.007).
No clear effect of nutrient concentration and PSB addition in the volatile fatty acids (VFA) concentration of the intestinal sections has been observed in the two assays tested. However, an interaction of both factors was shown in duodenum for lactic, propionic and total VFA (P<0.05), in jejunum for lactic acid (P<0.001) in ileum for acetic and total VFA (P=0.017), where PSB produced an increase in VFA concentration when added to C diet, but a decrease in VFA when added to R1 diet.
Histology of the different sections of intestine of chickens have not been strongly influenced by the experimental diets. Higher ileal villus height and ratio villus height:crypt depth (V:C) were observed in chickens fed R1 vs C diets (518 vs 470 µm, 3.57 vs 3.05, respectively, P<0.05) at 21 d in trial 2. Addition of PSB produced an increase of ileal mucosa thickness at 21 d. in trial 2 (619 vs 670 µm, P=0.048) and an increase in duodenal villus height of 3% (P=0.042) and in ileal mucosa thickness and ratio V:C of 9.6 and 10%, respectively (P<0.05), for 21 d. old chickens in trial 3.
A fifth trial was designed to evaluate the effects of PSB addition, alone or in combination with essential oils (carvacrol and ginger; PSBEO) or medium chain fatty acid (PSBMCFA) compared with a control diet or with an antibiotic supplementation supplied to broiler chickens challenged with necrotic enteritis and with a negative control (NC) on chicken performance, intestinal lesions and oocyst excretion. Birds were assigned to 6 treatments (8 replicates of 58 birds each). On d 13, challenged birds were inoculated with ~5,000 oocysts of Eimeria maxima by oral gavage and on d 18-19 with C. perfringens via drinking water. Jejunal samples were collected at d 12, 18, 21, and 28 to analyze the gastrointestinal tract epithelium. On d 12, before challenge, PSB diet presented the longest villi (982 vs 831 µm, as average P = 0.002) in the jejunum. It also improved FCR of the animals at the same level as NC or diet supplemented with antibiotic (P=0.004). At day 42, however, the only treatment that improved FCR when compared to the challenged, not supplemented group (1.62) was that supplemented with PSBEO (1.50), showing as well less NE related lesions.
It can be concluded that the addition of PSB may help the animal to counteract the negative effect of receiving diluted diets and it does it independently of the ingredients used in the diet. Besides, in combination with other active ingredients may reduce the detrimental effects of bacterial infections.
