DIRECT-FED MICROBIALS (DFMS) IN HORSES AND POULTRY: EFFECTS ON DIGESTIBILITY, NUTRITIONAL VALUE OF ANIMAL PRODUCTS AND ANIMAL HEALTH.

The objective of the research described in this thesis is to evaluate the effect of Direct-Fed Microbial (DFM) in horses and poultry, on digestibility and nutritional value of animal products and animal health. To achieve this objective, three different trials were designed; in the first trial was investigated the effects of live yeast on apparent digestibility in horses, in the second trial was studied the effects of the inclusion of some probiotics in broiler chickens infected with Eimeria spp. and in the last trial the effects of inclusion of selenium-enriched yeast in the diet of laying hens on production performances, health parameters, eggshell quality, and selenium tissue deposition were investigated. In the first study proposed were investigated the effects of the administration of live yeast (LY) in a high-fibre diet on nutrients digestibility in mature horses. Six Italian Standardbred mares (weight: 544 ± 14 kg; age: 15.30 ± 3.9 years) in two-period crossover design were fed a basal diet (2.5% body weight [BW]) in a 70:30 forage:concentrate ratio with (LY) or without (CTR) the administration of 4.6 × 1010 colony forming unit (CFU)/d of Saccharomyces cerevisiae (MUCL 39885). An adaptation to the diet of 14 days, and an 18-day administration phase, with fecal collection in the last 3 days were performed for each period. Yeast was top-dressed twice a day during the concentrate meal (12:30 AM and 09:00 PM). Change in BW was measured at the beginning of each experimental phase and the diet adjusted accordingly, and individual feed intake was recorded daily. Concentrate samples were collected at the beginning of each confinement period and individual hay samples were obtained for each confinement day 38 hours before fecal collection. No influence of LY was observed on BW change (P = .64), feed intake (P = .48), hay intake (P = .48), or concentrate intake (P = .47). S cerevisiae supplementation improved apparent digestibility of dry matter (64.5% vs. 60.1%, P = .03), organic matter (66.1% vs. 61.6%, P = .04), neutral detergent fiber (42.5% vs. 35.9%, P = .04), and acid detergent fiber (36.5% vs. 28.0%, P = .03) with a positive trend on crude protein (P = .08). In the present study, the administration of LY to horses significantly improved the digestion of the fiber fractions of the diet. The aim of the study was to investigate the effects of the inclusion of a probiotics mix (108 cfu/g of Bacillus coagulans, B. subtilis and Cl. butyricum) on growth performance, health status, and intestinal morphology of broiler chickens infected with Eimeria spp. for a complete production cycle from hatching to slaughter. A total number of 900 Hubbard male chickens, 1d old and coming from the same hatchery, were divided in 18 pens located in 3 identical rooms (6 pens per room). At the beginning of the trial, the animals were homogeneously distributed by body weight to 3 experimental dietary treatments consisting of a basal diet plus: PC= probiotics 0.05% (108 cfu/g of Bacillus coagulans, B. subtilis and Cl. butyricum) + a coccidiostat; C= a coccidiostat; P= probiotics 0.1%. On the second week of life each box of the experimental groups was challenged with 400g of litter containing 2.5x105 oocysts of Eimeria spp. homogeneously distributed. Considering the trial divided in two periods: no challenge (first two weeks) and challenge (3 to 8 weeks), in the first two weeks of the trial, birds fed the diets containing probiotics (PC and P) had significantly higher body weight (BW), average daily gain (ADG) and feed intake (FI) compared to animals fed the diet containing only a coccidiostat (C) and the feed conversion ratio (FCR) was significantly lower in the groups fed the diets containing probiotics (P and PC). During the challenge period BW was significantly higher in birds fed the diets containing coccidiostat (C and PC), while no differences were observed for FCR, ADG and FI. The administration of probiotics plus coccidiostat (PC) positively affected the number of intestinal fold goblet cells (F) in the duodenum and ileum. In the ileum of PC group the lowest values for gland depth (G) were assessed, while F:G ratio was lower compared with C group. Fecal count of Eimeria spp did not show any statistical difference between the three experimental groups at the end of the trial. The results of this work show that the administration of probiotics (108 cfu/g of Bacillus coagulans, B. subtilis and Cl. butyricum) in normal farming condition had positively influenced the growth performance of broiler chickens. Subsequently in challenge period no differences were detected between broilers fed either probiotics and/or coccidiostat considering; growth performance and fecal count of Eimeria spp, these results suggest probiotics may have positive effects administered alone or in combination with coccidiostats in broilers chickens infected with Eimeria spp. The aim of the third study is to evaluate the effect of inclusion of selenium-enriched yeast in the diet of laying hens on production performance, health parameters, eggshell quality, and selenium tissue deposition. (Chapter 5) Forty-eight ISA Brown laying hens, each 22 weeks of age, were utilized for an 8-week trial to evaluate the bioavailability of ingested selenium yeast and its effects on egg-laying performance, eggshell quality, health parameters and tissue Se distribution. Animals were divided into 3 treatment groups: the control group (C) received a basal diet containing 0.11 mg of Se /kg DM; the inorganic Se group (SS) received the control diet plus sodium selenite at 0.4 mg/kg DM; and the Se-yeast group (SY) received the control diet plus selenium yeast at 0.4 mg/kg DM. Feed intake, egg mass ratio, and production performances were not affected by supplementation with Se, regardless of the Se source. Only egg weight was higher (P< 0.05) for hens with diets supplemented with Se. Eggshell weight was improved in both Se-supplemented groups, whereas breaking strength was increased by the administration of SY. Breast muscle, liver and skin Se level was higher in the SY group than in the C group, whereas the Se level did not differ between the SS and C groups. Kidney selenium content was statistically significant only for SS animals. Eggs from SY hens had higher Se levels than those from SS hens Results of our study indicate that supplementation with 0.4 ppm of selenium from SS or SY does not affect hens’ zootechnical performance and blood metabolites. The only exception is the increased weight of eggs obtained from hens supplemented with Se. On the other hand, selenium—particularly in its organic form—improves eggshell quality. Specific selenium sources influence selenium distribution in hen tissues. Indeed, egg and breast muscle selenium concentrations were higher when hens were fed selenium yeast because of the greater bioavailability of organic selenium sources when compared with inorganic sources. The supply of organic selenium in the form of selenomethionine in laying hen feedstuffs benefits the human population via the food chain by helping to meet human selenium requirements that are not always satisfied by typical human diets.