Effects of arginine and proline combinations on performance, egg quality, plasma measurements, and liver characteristics in aged laying hens

The effects of different combinations of supplemental arginine (Arg) and proline (Pro) on productive performance, egg quality, relative organ weight, plasma measurements, and liver characteristics were investigated in aged laying hens. Four hundred and eighty 100-wk-old Hy-Line Brown laying hens were allotted to five dietary treatments with eight replicates of 12 individually caged hens for six weeks. The treatments consisted of a basal diet and four supplemented diets that formed a 2 × 2 factorial arrangement of 0.2 or 0.4% supplemented Arg and 0.2 or 0.4% supplemented Pro. A significant interaction between dietary Arg and Pro levels was observed for feed intake. Hens fed diets containing 0.2% supplemental Arg with 0.4% supplemental Pro or 0.4% supplemental Arg with 0.2% supplemental Pro had a larger (p < 0.05) feed intake than those fed diets containing 0.2% supplemental Arg with 0.2% supplemental Pro. For both supplemental Arg levels, hens fed diets containing 0.2% supplemental Pro had higher (p < 0.05) eggshell strength and enhanced yolk color than those fed diets containing 0.4% supplemental Pro. Increasing supplemental Pro from 0.2 to 0.4% was associated with lower (p < 0.05) relative spleen weight and liver lightness value, but higher (p < 0.05) relative abdominal fat weight. Among the five dietary treatments, plasma alanine aminotransferase activity was lower (p < 0.05) in hens fed the two mixed-level combinations or the high-level combination than in those fed the basal diet or the low-level combination. Plasma aspartate aminotransferase activity also was lower (p < 0.05) in hens fed the two mixed-level combinations than in those fed the basal diet. Overall, dietary Arg and Pro supplementation did not improve the productive performance of aged laying hens, although specific combinations affected feed intake and plasma measurements. Thus, the supplemental levels of Arg or Pro examined in this study provided no clear productivity advantage in aged laying hens.