DIETARY-SUPPLEMENTS OF FOLIC-ACID DURING LACTATION - EFFECTS ON THE PERFORMANCE OF DAIRY-COWS

The present experiment was undertaken to determine the effects of diet ary supplements of folic acid administered from 4 wk prepartum to 305 d of lactation on lactational performance. Sixty-three Holstein cows w ere assigned to 22 blocks of 3 cows according to lactation number, mil k production, and body weight (BW). Within each block, cows received 0 , 2, or 4 mg of folic acid/kg of BW per d. Dietary supplements of foli c acid increased serum and milk folates but affected milk production a nd composition of primiparous and multiparous cows differently. Supple mentary folic acid had little effect on milk production and compositio n of primiparous cows, except that milk production decreased during th e first 100 d of lactation. However, during a complete lactation(3 to 305 d after calving), supplementary folic acid was associated with inc reased milk production by multiparous cows (8284 +/- 560, 8548 +/- 380 , and 8953 +/- 191 kg for cows fed diets supplemented with 0, 2, and 4 mg of folic acid/kg of BW per d, respectively). The percentage of ash in milk was decreased for cows fed the highest amount of dietary foli c acid. During the first 100 d of lactation, supplementary folic acid was associated with a lower concentration of nonprotein nitrogen in th e milk of multiparous cows. The present study confirms results obtaine d previously, suggesting that, although the supply of folates from an unsupplemented diet and the ruminal microflora is sufficient to avoid a deficiency in folic acid, supplementary folic acid may increase the milk production of cows in the second lactation or greater.