The effect of β-carotene on the fertility of dairy heifers receiving maize silage

One hundred and sixty Friesian heifers were divided into four groups on the basis of live weight and age. All four groups received a production ration of 15 kg maize silage, 0·5 kg straw and either 1·5 or 0·5 kg concentrates according to their mean live weight. This ration supplied only 38 mg (3-carotene per animal per day. Two groups of heifers received a daily supplement of 300 mg β-carotene per head. The other two groups acted as controls and received a daily supplement of 60 000 i.u. vitamin A (18 mg retinol). All heifers received an adequate supply of vitamin A. Supplementation with 300 mg β-carotene per day significantly increased mean plasma concentrations from 3·52 mg/1 at housing to 5·58 mg/1 at first insemination ( P Supplementation with β-carotene did not affect reproductive performance or growth rate in heifers receiving a ration based upon maize silage.