Effect of Milking Frequency and Diet on Milk Production, Energy Balance, and Reproduction in Dairy Cows

The objective of this study was to determine the effects of reduced milking frequency and increased dietary energy density in early lactation on milk production, energy balance, and subsequent fertility. Sixty-six spring-calving, multiparous Holstein-Friesian cows were assigned to 1 of 3 treatment groups: once-daily milking on a standard diet (1×ST); 3-times daily milking on a standard diet (3×ST); and 3-times daily milking on a high-energy diet. Treatments were imposed for the first 28 d of lactation, after which all groups were milked twice daily and fed the standard diet. During the treatment period, the 1×ST cows had 19.6% lower milk yield and higher milk fat and milk protein concentrations (15.7 and 10.2%, respectively) compared with 3×ST. Dry matter (DM) intake was similar between 1×ST and 3×ST during the treatment period (12.64 vs. 13.25 kg/ d; SED = 0.82). Daily energy balance was less negative for 1×ST compared with 3×ST during wk 1 to 3 of lactation [−3.92 vs. −5.30 unité fourragère lait (UFL)/d; SED = 0.65; 1 UFL is equal to the net energy for lactation of 1 kg of standard air-dry barley]. During the treatment period, the cows on the high-energy diet had 17% higher milk yield, higher DM intake (15.5 vs. 13.9 kg/d; SED = 0.71), and similar energy balance (−4.45 vs. −4.35 UFL/d; SED = 0.65) compared to 3×ST. Diet had no significant effect on any of the fertility variables measured. The interval to first ovulation was shorter for 1×ST than 3×ST (18.3d vs. 28.6d; SED = 1.76). In conclusion, once-daily milking in early lactation may promote earlier resumption of ovarian cyclicity, mediated through improved nutritional status.