Effects of methionine hydroxy copper supplementation on lactation performance, nutrient digestibility, and blood...

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.