A probiotic is a culture of live microorganisms that can manipulate and maintain a beneficial microflora in the gut. Prebiotics are nondigestible feed ingredients that can positively affect the animal organism by stimulating the activity and growth of beneficial native bacteria in the gastrointestinal tract and eliminate the pathogenic ones. Some studies have shown their beneficial effects when they have been used separately or simultaneously in the form of synbiotics, to obtain enhanced mutual effect. These supplements were proposed with success as alternatives to antibiotic growth-promoting feed additives but further studies are needed to better understand their mode of action and effects. This review article presents growing interest in using these antibiotic alternatives, the potential mechanism of their action in the live organism, and discusses some recent data on the effects of these supplements in poultry nutrition.

The effect of dietary conjugated linoleic acid isomers (CLA) on growth performance, carcass composition, fatty acid composition of adipose and muscle tissues, and serum lipoproteins was investigated in broiler chickens. A total of 160 (eighty male and eighty female) chickens were allocated to four dietary treatments (0.0, 0.5, 1.0, and 1.5 % CLA) and fed a standard starter diet from 8 to 21 d, and a grower-finisher diet from 22–42 d. When determined for the total period 8–42 d, feed intake and body weight gains of broiler chickens were significantly reduced (from 3.31 to 3.12 kg and from 1615 to 1435 g respectively; P<0.05), particularly at the 1.5 % dietary CLA level. Feed conversion efficiency and carcass yield values showed no significant effects of dietary CLA. Abdominal fat deposition was significantly reduced (from 2.68 to 1.78 %; P<0.05), the relative proportion of breast muscles was unaffected, and that of leg muscles significantly increased (from 19.0 to 20.6 %; P<0.05). The concentration of CLA isomers (% of total methyl esters of fatty acids) increased linearly in tissue samples from broilers fed 0.5, 1.0, and 1.5 % dietary CLA. The relative proportions of saturated fatty acids (16:0, 18:0) were significantly (P<0.01) increased, and those of monounsaturated (16:1, 18:1) and polyunsaturated fatty acids (18:2, 20:4 in muscle tissues) significantly (P<0.05) reduced. Total serum cholesterol concentrations reached a maximum in broilers fed 1.0 % CLA and then decreased slightly (from 141.73 to 136.47 mg/dl; P<0.01). The same was true also for HDL-cholesterol (from 113.58 to 109.97 mg/dl; P<0.01). The HDL cholesterol:total cholesterol ratio and serum triacylglycerol concentration was unaffected. In conclusion, feeding CLA to broiler chickens resulted in substantial incorporation of CLA isomers into their tissue lipids, thus providing a potential CLA-rich source for human consumption.

In this paper, we present a study on the evaluation of the effect of xylanase addition to a diet with an increasing content of modern hybrid rye (Brasetto variety) on the performance indices and viscosity of small intestine content in broiler chickens. A total of 560 1-day-old male Ross 308 chickens were randomly assigned to 1 of 10 treatments, each comprising 7 replicate cages, with 8 male birds per cage. A 5 × 2 factorial arrangement was employed, with five dietary levels of ground rye (0%, 5%, 10%, 15%, and 20%). All the diets were either unsupplemented or supplemented with xylanase (200 mg/kg of feed; with minimum xylanase activity 1000 FXU/g). In the starter rearing period (1–21 days of age), the inclusion of rye (without xylanase supplementation) to the diet, even at the lowest dietary level (5%), negatively affected body weight gain (p < 0.05); there was no effect on feed intake and feed conversion ratio. In older chickens (the grower-finisher rearing period; 22–42 days of age), none of the dietary levels of rye (5–20%) affected growth performance indices. Similarly, no significant effect of increasing dietary level of rye was found for the entire rearing period (1–42 days of age). Diet supplementation with xylanase improved body weight gain and feed conversion ratio in chickens from 1 to 21 days of age. No positive effect of enzyme was found in older birds. No significant effects of the experimental factors used were noticed on the results of slaughter analysis, i.e., the carcass yield, breast meat yield, abdominal fat, and relative weight of the liver and gizzard. A high dietary concentration of rye (20%) increased the viscosity of small intestine content (p < 0.05); however, diet supplementation with xylanase significantly alleviated this effect. The findings of this experiment indicated that modern hybrid rye grain may be used at a 20% dietary level in broiler diets during the second feeding phase, i.e., from 22 to 42 days of age, without any detrimental influence on growth performance indices, while enzyme (xylanase) positively affected body weight gain and feed conversion ratio in younger chicks (1–21 days of age).

The aim of this study was to investigate the effect of two levels of whey protein concentrate (WPC, 80.35% protein, 5.86% lactose) added to diets and duration of these treatments on growth and slaughter value, haematological parameters involved in immune processes, oxidative status of liver and...

The aim of the experiment with 240 ISA Brown hens fed the diets with standard or decreased Ca level was to evaluate the effect of selected feed additives on laying performance and eggshell quality. The hens were allocated to 10 treatments, each containing 12 cages (replicates) of 2 birds. A 2 × 5 experimental arrangement was used. From 26 to 70 wks of age, experimental diets containing 3.20 or 3.70% Ca were used. The diets were either not supplemented, or supplemented with sodium butyrate, probiotic bacteria, herb extracts blend or chitosan. The decreased dietary Ca reduced eggshell quality indices in older hens (43-69 wks) (P<0.05) without effect on performance indices. The addition of the probiotic, herb extracts, or chitosan increased the laying rate (P<0.05). In older hens, i.e. at 69 wk, chitosan increased eggshell thickness and breaking strength, while herb extracts increased eggshell thickness (P<0.05). There was no interaction between the experimental factors in performance and eggshell quality. The used feed additives had no influence on fatty acid profile of egg lipids, however diet supplementation with chitosan decreased cholesterol concentration in egg yolk lipids (P<0.05). It can be concluded that such feed additives as probiotic, herb extracts, or chitosan may positively affect performance and eggshell quality, irrespective of Ca dietary level.