How do you know if replacement heifers are on target weight for breeding?
To say the least, weather conditions have been extremely difficult with areas grazed well back on many farms. Martina Gormley discusses the importance of assessing heifer body weight before the breeding season to make informed decisions.
Understandably, much of the discussion and frustration has been in relation to getting cows out. However, with breeding around the corner and many farmers considering synchronisation of heifers with sexed semen the body weight of heifers needs to be assessed. Ideally, this would be done before now but even now, it is not too late and this information will aid breeding decisions.
Table 1 below shows the target weights for three mature herd sizes. A herd with a mature herd size of 590kg should have heifers at 355kg in May, while a herd at 540kg will require heifers to be 325kg.
Table 1 Maintenance subindex (SI) and heifer target weights per month
Talking to a group of farmers that have taken the plunge and got heifers weighed recently, most have got a surprise with high parentage well under the target. One farmer said “I guess unless you’re in the mart every day then you’re not a good judge, plus we are too used of looking at our own stock”
If heifers can go out now until breeding what will they gain? If we take breeding on the 1st May and out from the 17th March, that’s 44 days at 0.8kg/day that’s 35kg of a gain. The big question is should sexed semen be used on underweight heifers, the advice is it should not be used. Synchronisation programmes plus sexed straws do not come cheap plus heifers calving pattern is extremely important. With so much at stake, heifers should be weighed and from these weights, a decision should be made on what to breed and whether sexed or conventional semen should be used.