Effects of rumen-protected choline with calcium salts of long chain fatty acids on milk yield and milk composition of middle and late lactation Holstein cows

• Cows supplemented with RPC had greater concentration of free choline in plasma.
• Supplementation with RPC significantly affected milk fat composition.
• Cows supplemented with RPC had greater milk fat concentration of total MUFA and total cis PUFA.
• Omega-3 fatty acids alpha linoleic, EPA, DPA and DHA occurred in greater concentration and yield when RPC was supplemented.

The objective of this study was to evaluate the effect of rumen-protected choline (RPC) supplementation on milk production and milk composition of dairy cows. Fifty lactating multiparous Holstein cows >80 days in milk were randomly assigned to one of two treatments groups. Cows were fed with: (1) control diet (CON; n=25), not supplemented with RPC and (2) supplemented diet (RPC; n=25), supplemented with RPC (115 g/cow/d). Control and supplemented cows were fed at ad libitum intake twice daily. Body weight and body condition score were measured weekly. Milk production and dry matter intake were recorded daily. Milk samples were collected twice weekly on week 3, 6, and 9 and analyzed for fat, protein, lactose, urea nitrogen, somatic cell count, fatty acid (FA) composition, and free choline concentration. Plasma was obtained on week 1, 3, 4, 6, 7, and 9 and analyzed for concentrations of free choline and non-esterified fatty acids. Cows remained in the experiment for 9 weeks. Data were analyzed using the MIXED procedure of SAS (v9.4). Higher free choline concentration in plasma (P<0.001) confirmed intake and absorption of RPC by supplemented cows. Dry matter intake (23.6 vs. 23.4 kg/d), body weight (704 vs. 703 kg), and body condition score (2.86 vs. 2.90; 1–5 scale) were not affected (P>0.05) by RPC supplementation (CON vs. RPC, respectively). There was no difference (P>0.05) on milk yield (36.72 and 36.81 kg/d, respectively), 3.5% fat corrected milk, or energy corrected milk between supplemented and non-supplemented cows, respectively. Although production parameters were not affected by RPC supplementation, they were significantly affected (P<0.01) by period and lactation stage. While concentration of de novo and mixed (16:0+cis-9 16:1) FA in milk fat were greater in CON cows, preformed FA were greater in RPC (P<0.05) supplemented cows. Concentration of total saturated FA (P<0.001) was higher in CON cows, whereas total monounsaturated FA (cis and trans) and cis polyunsaturated FA concentrations were greater in RPC cows (P<0.05). Yield of polyunsaturated omega-3 FA was greater when RPC was added to the diet. Although milk production was not affected, supplemental RPC either in middle or late lactation resulted in milk fat composition enriched by long chain polyunsaturated FA.