Rearing heifers as herd replacements is an important component of farm management.
These animals will be the future of the enterprise.
Correct heifer rearing provides a sound basis for a profitable business, while failing to rear them appropriately may lead to economic losses. These losses occur either during the rearing period or after the animals join the herd, through mortality, increased disease, forced culls and reduced productivity.
Successful heifer rearing requires attention to detail, and a programme which sets defined targets and ensures that these are achieved, through regular monitoring of the animals throughout the rearing period.
One interesting task which is an option for participants in the new beef discussion groups is weighing suckler calves between day 150 and 250 — the aim of which is to measure calf growth rate, and ultimately the volume and quality of milk produced by the cow.
The ultimate objective is to raise, at least cost, an animal that, once calved, is capable of maximising her genetic potential for production.
Central to the cost of production is the chosen age for calving. For sucklers, the accepted optimal target is 22 to 24 months. Below this age, there will be an increased incidence of calving difficulty, and reduced productivity after calving.
Heifers that calve late may become overfat before calving, and rearing costs are increased. However, if a farm is unable to achieve the target weight gains required to calve at 24 months, it is better to calve later and accept increased rearing costs.
At this time of year there are two types of heifers on most suckler farms — the ones suckling their mothers, and the ones that are in calf for next season.
Heifer rearing is expensive, with up to 60% of the costs being incurred in the first nine months. The temptation is often to try and find feeding and management systems that reduce rearing costs. However, it is no good saving feed costs for a calf if it later results in increased mortality, more time to service, and smaller heifers at calving.
Ensuring that target growth rate is met during this period is essential to maximise the future fertility and productivity of the animal.
The target growth rate for heifers varies according to age, and is influenced by the planned age and weight at calving, and by breed. The aim should be to achieve a well grown heifer at calving; in general, the heavier the heifer at calving the less growing she needs to do in her first and second lactation, so the more milk she will produce for rearing her calf.
There is a fine line between achieving target weights at calving and falling short. For example, if your target is to have a heifer at 600kg for calving at 24 months, then with a birth weight of 40kg, she must gain an average of 0.77kg/day over the 730 days (two years). Achieving an average of 0.7kg/day will only give a 551kg heifer at first calving.
Growth in heifers should be directed towards lean tissue, and not fat deposition. This can be most influenced by providing suitable levels of protein, and avoiding diets with a high starch and low protein content.
Digestible fibre and protein are the essential nutrients required for efficient frame growth. High starch diets in heifers will result in excessive fat deposition in the udder, reducing mammary tissue development and subsequent reducing milk production.
Given the above requirements for growth, it is critical that there are no prolonged periods of very low growth in replacement heifers.
In the current bad weather, it is critical that heifer performance in both beef and dairy herds is monitored closely. Heifers that have been inseminated to calve next spring need to be provided with sufficient good quality grass to maintain growth. If these heifers are on poor quality grass, are tight on grass, or have returned indoors, then they will need to be supplemented with concentrates. If suckler cows with calves at foot are on restricted pasture quantity or quality, creep feeding should be introduced, to keep calves growing.
Mineral supplementation is also an essential part of successful heifer rearing. Calcium, phosphorous, sodium and magnesium are essential for digestion of feed, and for frame growth. Micro-minerals are needed too, such as copper, while zinc hardens hoofs and horns. Vitamin E aids the immune system.
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