Careful heifer rearing to ensure longevity
Heifers calving by two years survive longer in the herd, have a greater lifetime yield and are more profitable, according to a jointly-funded project by DairyCo and DEFRA, at the Royal Veterinary College (RVC).
The project looked at how farmers can best manage heifers to reduce losses from involuntary culling.
Heifers are the future of any dairy business and all producers want them to have a long and fruitful life in their herd, says DairyCo research manager Charlotte Bullock. “A longer herd life yields greater profits and this is directly correlated to the number of lactations achieved in a lifetime,” she says.
The RVC study using 650 dairy calves found an average 8% calf mortality at birth, which was higher for first-calving heifers (12%) and twins (18%). A further 14% of live-born heifer calves failed to reach first calving and 15% of cattle were culled in their first lactation.
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| A growth rate of 0.7-0.8kg a day is optimum for heifers. |
“When it comes to reducing calf mortality at birth and before the age of 15 months, the study showed observation of the calving pen is vital to ensure cows requiring assistance get adequate help,” says Ms Bullock.
“All heifers should aim to achieve an optimum growth rate of 0.7-0.8kg a day, as growing too slowly (less than 0.6kg a day) delays first calving. However, a fast growth rate (more than 0.85kg a day) is expensive and is also associated with poor fertility and calving problems.”
In the study, calves with poor early growth rates in the first six months were more likely to die young due to disease and were less likely to conceive at 15 months. Heifers calving at less than 25 months of age were heavier at one, six and 15 months of age.
According to RVC’s Claire Wathes, measuring body weight and height at various stages throughout the first 15 months is vital.
“Regular measurements give producers time to correct any problems with growth rate before the heifer reaches puberty and first service. Weighing heifers at a time that coincides with another essential management practice like worming will reduce animal stress and the time taken to do the job,” says Prof Wathes.
It is also important producers make decisions about weaning on a combination of calf weight, feed intake and age, but not age alone. If necessary, small calves should be weaned later, adds Ms Bullock.
“It might be necessary to provide heifers with additional supplements when grazing, if grass quality is poor to maintain optimal growth. You don’t want to see all the hard work done inside lost while out at grass.
“One of the benefits of closely monitoring the growth of heifers during the rearing period and ensuring they are of an adequate size to be served at 15 months, is that nutritional management around calving is easier. Nutritional management of pregnant heifers in late gestation helps reduce the risk of fertility problems after calving,” she says.
Ms Bullock recommends heifers calve with a body condition score of three or less. “Fat heifers at calving will suffer from greater calving difficulties, more weight loss in early lactation and more fertility problems. However, small, underweight heifers will give birth to small, underweight calves and you are facing the same problems with the next generation,” she says.
Prof Wathes says a number of factors have an impact on longevity and breeding success. “Heifers calving by two years survive longer, have a greater lifetime yield and are more profitable, so the target should be to reach puberty by nine months and first breeding by 14-15 months.
“Achieving good growth rates and heifer fertility is influenced by a number of factors, including genetics, but good management of calves and heifers will play a major role in reaching these targets,” says Prof Wathes.