Outwintering Replacement Dairy Heifers

Published 13 March 15

At the time of this study AHDB Dairy was operating under the DairyCo brand. In June 2015 DairyCo was rebranded to AHDB Dairy.  

‘Measure to manage’ is the key message from a DairyCo funded trial investigating the effect of forage type on the performance of out-wintered dairy heifers on 9 commercial farms across GB.


Over the last four years, researchers at Harper Adams University (HAU) have been investigating the suitability of outwintering systems for replacement dairy heifers as part of the DairyCo Grasslands, Forage and Soils Research Partnership.

‘With increasing dairy herd size, out-wintering systems may provide a cost effective method of facilitating herd expansion’ outlines HAU researcher Prof Liam Sinclair ‘however little is known about the performance of dairy heifer replacements on these systems’.

Over the course of the trial, the research team visited 9 commercial farms and monitored liveweight gains of in-calf spring calving heifers on three different forages: deferred grazing, kale and fodder beet. The team found no difference in liveweight gains (LWG) over the course of the rearing period (averaging 0.25kg LWG/cow/day) between the three forages. There was a wide range in daily liveweight gains between farms (-0.22 to +0.55 kg/cow/day) however the highest liveweight gains were noted on those farms which regularly weighed animals and adjusted their management accordingly.

In addition, forage source did not significantly affect milk production in the first 100 days of lactation however those animals outwintered on fodder beet did have a higher proportion of first lactation animals in calf at the end of the mating period (95%) compared to the kale (86%) and deferred grazing (88%) forages.

The study also examined the impact of administering a mineral bolus on animal performance. Supplementing with a mineral bolus resulted in a small increase in body condition prior to calving, and increased milk fat content in early lactation (4.26 vs 4.07%), especially in herds grazing kale.

‘From our research we can see that variation in heifer performance during the rearing period is greater between individual farms than between different forage types’ states Liam. ‘As a result, decisions on the most appropriate forage should be made on soil type to minimise damage, and crop yield’ he continues.

DairyCo research and development manager Dr Debbie McConnell says ‘Heifers rearing is the second largest cost to a dairy business after feed and forage costs and therefore it is important to maximise the return on this investment. This study highlights the crucial role regular monitoring plays in ensuring heifers reach their target liveweight gains’.

The full project report can be downloaded from the DairyCo website where more information on monitoring growth and liveweight gains in youngstock can also be found.