Dietary Citrulline Supplementation Enhances Milk Production in Lactating Dairy Goats

抄録

Abstract
Background Nutrition, day of lactation, litter size, parity, and sire impact lactational performance in goats. Arginine (Arg) has important roles in synthesis of nitric oxide (NO), polyamines, and creatine. Ruminal microbes degrade extracellular Arg; however, extracellular Cit is not degraded by ruminal microbes and can be fed unencapsulated as a proxy for Arg. Cit is absorbed in the small intestine, converted to Arg, then metabolized to NO, polyamines and creatine that may enhance lactational performance. This study determined effects of dietary citrulline (Cit) supplementation on milk production and milk composition of Alpine dairy goats. Does were synchronized to estrus and bred to Alpine bucks. Parturition was induced on Day 149 of gestation. After kidding, does were suckled overnight to allow their kid(s) to obtain colostrum before being milked 24h later (Day 1 of lactation). Does were assigned to either control (CON, n = 24) or citrulline (CIT, n = 23) supplemented diets. The isonitrogenous control diet was supplemented with 1.37% alanine and 1.00% soybean hydrogenated oil. The CIT supplemented diet was 97.63% basal diet with a 2.37% supplement (0.5% Cit, 0.5% Glutamine, 1% soybean hydrogenated oil, and 0.37% cornstarch). Diets were group fed ad-libitum by treatment group. Blood samples were collected on Days 0 and 30 of lactation, and daily milk volumes were collected twice daily. On Days 10, 20, and 40 of lactation, milk samples were collected for compositional analyses. Results CIT-treated does had greater mean daily milk production (P = 0.0332) and there was an effect of day of lactation on mean daily milk production (P < 0.0001). Does producing three kids had greater mean daily milk production than does producing one kid (P<0.001). Multiparous does had greater mean daily milk production than primiparous does (P<0.0001), and there was an effect of sire on mean daily milk production (P<0.05). Compositional analyses revealed that Cit supplementation increased soluble-non-fat (SNF) (P= 0.0189) and protein (P=0.0238) in milk. Conclusions Dietary supplementation of Cit fed ad-libitum increased mean daily milk yield and impacted milk composition in Alpine does. Further investigations should seek to understand underlying mechanisms responsible for these effects.