Effects of methionine hydroxy copper supplementation on lactation performance, nutrient digestibility, and blood biochemical parameters in lactating cows.

The objective of this study was to investigate the effects of methionine hydroxy Cu [(HMTBA)(2)-Cu] supplementation on lactation performance, nutrient digestibility, and blood biochemical parameters in lactating cows. Thirty lactating Holstein cows were assigned to 1 of 3 treatments in a randomized block design: (1) Cu sulfate only (S): 12 mg of Cu provided by CuSO(4) per kilogram of concentrate; (2) Cu sulfate and (HMTBA)(2)-Cu (SM): 6 mg of Cu provided by CuSO(4) and 6 mg of Cu provided by (HMTBA)(2)-Cu per kilogram of concentrate; or (3) (HMTBA)(2)-Cu only (M): 12 mg of Cu provided by (HMTBA)(2)-Cu per kilogram of concentrate. The level of dietary Cu was determined according to the NRC (2001) requirement. This experiment lasted for 120 d, with the first 20 d for adaptation and with sample and data collection beginning on d 21. The milk yield and 4% fat-corrected milk yield of cows in the SM treatment tended to increase compared with those in the S and M treatments. Cows fed SM also tended to have higher NDF and ADF apparent digestibility values than did cows fed S or M. Plasma Cu concentration significantly increased for the SM treatment compared with the S and M treatments. Cows fed S had higher plasma K concentration than did cows in the other 2 treatments. In conclusion, replacing one-half of the dietary Cu sulfate with (HMTBA)(2)-Cu increased plasma Cu concentration and tended to improve the neutral and acid detergent fiber apparent digestibility values and the lactation performance of lactating dairy cattle.