Managing Replacement Heifers for Service at Springtime01 April 2015
Whether home-bred or bought in, heifers are a big part of the future of your operation and represent a doorway to new genetics and higher productivity.
For this reason, appropriate selection is crucial, according to livestock advisers at England's red meat levy board EBLEX.
Sourcing heifers from other farms brings disease risk and time scales should be granted for vaccines and tests accordingly. Changes to environment, feed and housing can add to stress, reducing fertility.
The main disease risks are Johne’s Disease, Bovine Viral Diarrhoea (BVD), Leptospirosis and Infectious Bovine Rhinotracheitis (IBR), write advisers at EBLEX.
Ensure any testing required is carried out well in advance of serving to prevent problem heifers being kept. Heifers must have completed their vaccinations at least four weeks before service.
It is too much to ask these heifers to mount an immune response to vaccines and conceive at the same time.
Table assumes first service at 15 months of age
Selecting the Right Heifers
Select homebred heifers based on their growth rate to weaning, structural soundness, temperament and liveweight relative to target for the service period. Heifers born early in the calving period usually make the best replacements, because they are well grown, likely to reach the target service weight and are born to fertile cows.
Heifers should be 65 per cent of their mature bodyweight at the start of the breeding season, advises EBLEX. To increase the chance of heifers conceiving during the target service period and at regular yearly intervals after that, they should be managed to reach target weights at key points.
The targets are expressed relative to mature cow weight, so it is important that accurate mature cow weights are used to calculate them (Table 2). Heifers that are too fat at service will be harder to get in calf. It is better to keep them leaner rather than fatter at this time and allow for some increase in the level of feeding towards service.
Leaner heifers have less liver problems and are usually more fertile, although still require adequate levels of feeding. If using AI to serve the heifers, it is important to discuss the different synchronisation program options with the vet well in advance.
Planning and attention to detail are vital for achieving good conception rates. Bull options also need considering early so a suitable sire for the heifers and the herd can be chosen. Ensure the bull has good Estimated Breeding Values (EBVs) for Calving Ease – Direct, as this identifies sires whose progeny will be born without assistance.
When buying a bull to use on heifers, source it at least three months before the mating period to allow for acclimatisation and for health and fertility testing. All breeding cattle should be checked pre-mating and treated if there are any issues with lameness, worms and liver fluke.
This will allow full recovery before service and give the best chance of conception. Feed to ensure continuous lean growth and a target body condition score of approximately 2.5-3 at calving. Offer good quality forage and high quality protein and energy sources.
Increase the level of nutrition gradually towards the service period and minimise stresses and changes in management at this time. Also consider mineral and vitamin requirements, which will maximise fertility, eg manganese, selenium and iodine.