Effects of level of concentrate feeding during the second gestation of Holstein-Friesian dairy cows. 1. Feed intake and milk production.

The objective of this experiment was to examine the residual effects of the level of concentrate feeding during the second gestation on performance in the second lactation. Forty-three Holstein-Friesian heifers that calved for the first time at 2 or 3 yrs of age were offered diets based on ad libitum consumption of ryegrass silage and either 2 or 7 kg/d of concentrates over the second half of the first lactation. All cows received a low quality diet, based on grass silage and barley straw (60:40 DM basis) for a short (6-wk) dry period. Feeding in the second lactation was based on ad libitum access to grass silage and a flat rate of concentrates (8 kg/d for 120 d; 5 kg/d thereafter). Three-year-old heifers produced more milk than 2-yr old heifers in the first lactation, equivalent to 93 kg of fat-corrected milk for each additional month of rearing. Cows given the low level of concentrates produced less milk and gained less weight and body condition, though there was a partial compensation when silage quality improved in late lactation. Forage intake declined as cows approached calving, and cows gained little weight or body condition over the dry period. There was no effect on calf weights. Cows that had received the low level of concentrates in the previous lactation consumed more forage dry matter during the second lactation. Parallel curve analysis showed that 2-yr-old heifers that had received a low level of concentrates produced significantly less milk in the second lactation. The numerically much greater gains of weight and body condition for this group were not statistically significant, owing to large between-cow variation.