Periparturient and early lactation performance and metabolism of replacement Holstein‐Friesian heifers out‐wintered on fodder beet or perennial ryegrass compared with winter housing

The effect of winter feeding system on the periparturient performance and early milk production and metabolism of pregnant Holstein‐Friesian dairy heifers destined for a high‐output, total mixed ration (TMR)‐based system was examined. Forty‐eight, 23 ± 0.4‐month‐old, in‐calf Holstein‐Friesian heifers were assigned to one of three treatments: out‐wintered on perennial ryegrass and grass silage (G), out‐wintered on fodder beet and grass silage (F) or housed and fed grass silage and concentrate (H). The study commenced in November 2013, with heifers on treatment for 91 days, housed from 6 weeks prior to parturition and fed a dry cow TMR. Postpartum performance and metabolism were monitored for 12 weeks. Prepartum, average daily gain was lower in heifers receiving G at 0.95 kg d −1  cow −1 than F or H (1.24 and 1.11 kg d −1  cow −1 respectively). Body condition score of heifers that received G was also lower compared with treatments F or H both pre‐ and postpartum. Prepartum, plasma β‐hydroxybutyrate concentrations were lowest in animals receiving treatment H, highest in F and intermediate in G, but did not differ between treatment postpartum. Milk yield averaged 30.7 kg d −1  cow −1 and was not affected by treatment, but milk fat content was lowest in animals that received F (35.4, 37.1 and 37.9 g/kg for F, G and H respectively). The results indicate that out‐wintering in‐calf dairy heifers on fodder beet or perennial ryegrass is a viable alternative to winter housing in high‐output TMR‐based milk production systems in a temperate region.