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Effects of rumen-protected choline on plasma, milk yield and composition of middle and late lactation Holstein cows
Rumen-protected choline (RPC) has become common in the dairy industry; questions regarding its benefits remain prevalent. The objective of this study was to assess the effects of RPC on milk yield and milk composition. Fifty (n=50) lactating multiparous Holstein cows over 100 days in milk were randomly assigned to one of two treatments. Dietary treatments were: 1) control diet (CON, n = 25), not supplemented with RPC and 2) supplemented diet (RPCt, n = 25), supplemented with RPC (115g/cow/day). Control and supplemented diets were fed ad libitum once daily. Basal diet was formulated according to NRC, 2001 recommendations to meet or exceed nutrient requirements. Body weight (BW) and BCS were measured weekly. Milk production and DMI were recorded daily. Milk samples were collected twice weekly on weeks 3, 6, and 9. Milk samples were analyzed for fat, protein, lactose, urea nitrogen (MUN), somatic cell count (SCC), fatty acid (FA) composition, and choline concentration. Plasma from blood samples were obtained on weeks 1, 3, 4, 6, 7, and 9 and analyzed for NEFA and choline concentrations. Cows remained in the experiment for 9 weeks. Data were analyzed using the MIXED procedure of SAS (v9.4). Dry matter intake, BW, and BCS were not affected (P > 0.05) by RPC supplementation. Cows supplemented with RPCt did not have greater milk yield, 3.5% FCM, ECM, or milk components than control cows (P > 0.05). While concentration of de novo and mixed (16:0 + cis-9 16:1) FA were greater in CON; preformed FA had greater concentration in RPCt (P < 0.05). Total saturated FA (P < 0.001) concentration was higher in CON cows than RPCt. Total MUFA and cis PUFA concentration were greater in RPCt cows (P < 0.05) than CON. Yield of cis PUFA tended to increase (P = 0.08) in RPCt cows. Omega-3 and omega-6 FA had greater yield in RPCt when compared to CON. Higher choline concentration in plasma (P< 0.05) indicated intake and absorption of RPC by supplemented cows. Cows in RPCt had their milk fat composition enriched by long chain PUFA such as LA, ALA, DHA, and EPA either in middle or late lactation.
Keywords: dairy cow, choline supplementation, milk fatty acids