Autumn heifer management

September and into October, is a crucial time in the rearing cycle for replacement heifers. Grass growth starts to slow and grazing conditions tend to become more difficult. Records show heifer growth rates can also slow substantially so Martina Gormley, Dairy specialist has heifer management advice

Managing light weanling and yearling heifers

Records show that heifer growth rates can slow substantially at this time of year and this is particularly important in underweight weanlings and yearlings. The threshold figures for weanling and yearling heifers are 190kg and 440kg in mid-September (approximately 33% and 75% of an assumed mature weight of 570kg) for heifers calving at 24 months of age. Heifers that are lighter than this should be separated and given priority access to grass. If grass is in short supply or grazing conditions difficult, they should be fed a supplement until housing time to maintain or increase growth rates. One or two kilogrammes of concentrate per head per day for underweight heifers is usually sufficient.

Weight data shows that heifer calves at grass in summer can achieve weight gain of 0.85kg/day on grass only. While in the autumn where 1kg of concentrate plus good quality grass is offered, 1kg/day can be achieved. For heifers behind weight the autumn period can significantly add or take from the mating start date weight.

Table 1 below shows the importance of the weight at mating from a longevity in the herd point of view. This data has come from over 80,000 weight and milking records.

Heifers found underweight at ≤316kg and overweight ≥343kg had a lower percentage survival to the beginning of third lactation. With heifer rearing costs near €1500 it is vital that longevity is maximised from a profitability point of view. For many calves an average daily again from birth to mating of 0.7kg/day will result in the appropriate mating start date weight. However calves that are younger and that may have had a set back at some stage will need to achieve higher than 0.7kg/day to reach the target weight at breeding.

This is where autumn supplementation plus good quality grass can help these heifers reach the target mating weight. 

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The Teagasc Dairy Specialists issue an article on a topic of interest to dairy farmers every Monday here on Teagasc Daily. Find more on Teagasc Dairy here