Effects of rumen protected choline supplementation on milk production in dairy cows fed hay based diets

Choline has been proposed as limiting nutrient in lactating dairy ruminants especially in early lactation. This situation seems to be exacerbated when silage-based diets are fed, whereas less is known when hay-based diet are used. In light of this the aim of the study was to evaluate milk production in dairy cows receiving a hay-based diet supplemented with rumen-protected choline (RPC). For this purpose ten Italian Holstein multiparous cows, in the second month of lactation (50 days in milk), were divided into two experimental groups: control group (CTR) receiving an empty capsule (no choline), and RPC group receiving 20 g/day of choline in rumen protected form. Cows were fed a hay-based diet designed according to NRC 2001 requirements. The experiment lasted 60 days. The mean postpartum DMI was unaffected by the treatment (26.0 and 25.2 kg/d for CTR and RPC, respectively). Mean milk yield did not change between experimental groups (33.3 kg/d and 34.3 kg/d for CTR and RPC, respectively), even though RPC supplementation increased milk production (P<0.05) in the first weeks of the trial. A slightly increase in milk protein yield (1012 vs 1093 g/d for CTR and RPC, respectively; P<0.05) has been observed in RCP supplemented animals. No change was observed in milk fat content (3.23% vs 3.22% for CTR and RPC, respectively). Dietary treatment did not affect the metabolic profile of experimental cows. Results obtained from the present trial suggested that RPC administration can be effective in optimizing milk production in dairy cow receiving a haybased diet, even though an exhaustive comparison with a silagebased diet deserves further investigations. Acknowledgments Ricerca Corrente 2009 dal titolo "Applicazione della genomica alla risoluzione di problemi di fertilità, resistenza alle malattie e assicurazione della qualità dei prodotti in bovini e suini" (ProZoo).