Dietary Protein Effects on Growth Performance, Carcass Traits and Expression of Selected Jejunal Peptide and Amino Acid Transporters in Broiler Chickens

The effect of dietary protein on growth, carcass traits and some specific intestinal intestinal peptide and amino acid transporters in broiler chickens was studied. Birds received a common pre-test diet, and were subsequently fed either a standard positive control diet (PC) or a reduced CP diet (RCP) from 21 to 42 d of age. Growth was negatively impacted with feeding of RCP as manifested by an increase in feed consumption and feed conversion ratio. Carcass traits also showed evidence of negative effects of feeding the RCP diet, leading to a reduction in carcass and breast meat yield and an increase in abdominal fat percentage. Blood plasma total protein was reduced when the broilers were fed the RCP diet. Expression of mRNA for one peptide (PepT1) and four AA intestinal transporters (bAT; CAT2; yLAT2; EAAT3) was measured from the jejunum. Quantified mRNA for the AA transporters yLAT2 and EAAT3 showed that they were upregulated in chickens fed the RCP-diet. The transport systems PepT1, bAT, and CAT2, were not affected by the dietary treatment imposed. The live and processing data validated the in vivo portion of the study and elucidated the negative impact of feeding the RCP diet, while the responses observed with the expression of the various transporters may help provide some insight on the physiological consequences and adaptations that birds endure when provided diets too low in CP for abnormally extended periods of time.