Supplementation of guanidinoacetic acid to broiler diets: effects on performance, carcass characteristics, meat quality, and energy metabolism

Creatine, (CREA) a central constituent in energy metabolism, is obtained from dietary animal protein or de novo synthesis from guanidinoacetic acid (GAA). Especially in all-vegetable diets, supplemental CREA or GAA may restore the CREA availability in tissues, and hence, improve performance. In this study, 768 one-d-old male Ross 308 broilers were assigned to 1 of 4 diets: negative control, all-vegetable corn-soybeanbased; negative control supplemented with either 0.6 or 1.2 g of GAA per kilogram of feed; and positive control (60, 30, and 30 g/kg of fish meal in the starter, grower, and finisher diets, respectively). Each treatment was replicated in 6 pens of 32 birds each. At the end of the grower period (d 26), 2 birds per pen were euthanized for metabolic measurements. Four broilers per pen were selected at slaughter age (d 39) to determine carcass characteristics and meat quality. Compared with the negative control, GAA supplementation resulted in an improved gain: feed ratio (P < 0.05) and ADG (P < 0.05; + 2.7 and + 2.2% for GAA at 0.6 and 1.2 g/kg, respectively) throughout the entire period. Breast meat yield was higher for the GAA diets compared with that of the negative control birds (P < 0.05; 30.6 vs. 29.4%) and was comparable with that of the positive control birds (30.2%). With regard to meat quality, lower ultimate pH values, higher cooking and press fluid losses, and higher color L* values were observed for the GAA diets compared with those of the negative control diet (P < 0.05). These effects were small, however. The GAA and CREA levels in breast meat were lower and higher, respectively, in GAA-fed birds compared with those of the control birds (P < 0.01). The diets did not affect plasma metabolic traits, except that plasma insulin-like growth factor I concentrations were almost twice as high in animals fed 1.2 g/kg of GAA compared with those of all other treatments. The GAA included in all-vegetable diets improved animal performance for the whole rearing period and increased breast meat yield

Gut antibacterial effects of C7 and C9 carboxylic acids in the diet of piglets

The antibacterial effects of odd-numbered medium-chain fatty acids (MCFA), such as C7 and C9 carboxylic acids, are poorly described and, hence, their potential as a feed additive for weaned piglets has not been explored. First, the antimicrobial activity was tested in in vitro incubations simulating the digestion in the stomach (pH 3), duodenum (pH 5), and ileum (pH 7) at 0, 17.5, 35.0, and 70.0 mmol/L carboxylate and compared with even-numbered MCFA. All compounds showed a significant reduction of analyzed bacterial counts compared with the control, in many cases >2 log reduction up to complete disappearance, depending on pH and dose. At pH 3 and 5, C6 through C9 carboxylic acids were equally effective against coliforms, whereas C10 was less effective. The activity against lactobacilli and streptococci was higher at the lower pH and increased with chain length. The antimicrobial effects of C7 and C9 carboxylic acids were, in most cases, in between or, in one case, better than that of their respective neighboring even-numbered MCFA. Next, an equal mixture of C7 and C9 carboxylic acid was fed to weaned piglets at 0, 0.1, 0.2, and 0.4% carboxylic acids in the diet for 42 d (8 pen replicates with 6 pigs each). At d 13/14, 1 piglet per pen was sampled to determine major gastric and proximal and distal small intestinal bacterial groups and histomorphological characteristics. Numerical improvements of animal performance for all supplemented diets were observed (P > 0.05) and this corroborated with a trend for longer villi in the proximal small intestine (P = 0.082). The highest dose tended to reduce streptococci in the stomach contents (P = 0.079). In vitro, C7 and C9 carboxylic acids demonstrated clear and significant antibacterial effects against the major bacterial groups in the stomach and small intestine. In the postweaning performance trial, they showed potential to ameliorate performance