Conquering the great outdoors

Published 25 September 15

Outwintering dairy animals can reduce total feed costs by 20 to 30% on dairy farms. However, the success of the system requires farmers to pay close attention to animal performance, according to Dr Stephen Whelan, Research and Development manager for nutrition at AHDB Dairy.

Successful dairy operations usually aim to calve their replacement heifers down at 90% of their mature weight by 24 months of age. To do this, the animal needs to grow by an average of 0.70kg/day, every day for two years. But what is performance like in outwintered animals?

Recently, an AHDB Dairy-funded study reported that animal performance was only 0.25kg/day over a 12-week period, highlighting severe underperformance on the nine farms studied. Because this was a research study, it was not possible to make adjustments during that time frame. However, on commercial dairy units farmers should weigh their replacement heifers on a monthly basis and adjust the management as required.

To help in the management of outwintering systems it is useful to know what the requirements of the heifers are and what the feed is capable of providing. For example, a 500kg heifer growing at 0.7kg/day requires approximately 70MJ of ME per day. The energy contents of the fodder beet, grass and kale used in the study mentioned above were 9.3, 9.8 and 10.0 MJ ME. This means that our example heifer needs to consume 7 to 8kg DM to meet her requirements. This can be a difficult task for a pregnant dairy heifer. To help bridge the gap between energy available and that supplied, grass silage or concentrates should be used as a supplement.

Another AHDB Dairy-funded outwintering study conducted at Harper Adams University, chose to supplement their animals with grass silage at a rate of 0.35 of DMI. The remainder of the diet consisted of either grass or fodder beet with a housed control group receiving a TMR. Weight gain in this study averaged 1.1kg/day, comfortably meeting the requirement of these high genetic merit heifers with feed costs that were 20 to 30% below the cost of the TMR fed animals. More importantly, these results demonstrate that, with careful management, outwintering replacement heifers can meet their growth targets.

Table 1. Factors to consider for a successful outwintering operation

Factors to success

Action required


Site selection

Aim for a free draining, gently sloping site


High-yielding crop with high utilisation

Seek agronomic advice on which crops perform best in your area


Liveweight gain of 0.7kg/day+

Measure on a monthly basis


Assess feed quality

Get samples of forage analysed


Balance animal requirements

See Chapter 10 in Feeding+