Heifer Management.... or future-proofing your herd!
"A few lighter heifers won't make a difference to herd fertility and besides, mine are all in pretty good nick!"...
The above comment based on the ‘eye-o-meter' assessment of young stock is a common one, and as a general rule, most folks aren't far off in their assessments of stock condition.
So the following question must be asked: do you guarantee that what you see with your eye is true? Would you gamble your mating performance on your eye, or the future potential lifetime milk production of those heifers on a look over the fence?
The reproductive performance and milk production potential of replacement heifers is directly related to growth rate and liveweight at first mating and calving. Calves and heifers must be reared to achieve liveweight targets, otherwise their first calving will be delayed, liveweight at calving will be too low and fertility during the next mating period reduced. Well-grown heifers will produce more milk in the first lactation, compete better with mature cows and will survive longer in the herd.
Measuring liveweight should be done at least every three months but more regularly will allow you to make changes more quickly if required. Scales are by far the best option and also the quickest. You should aim to measure them at the same time during the day or let them stand off for a couple of hours before weighing to remove the variation in weights due to gut-fill changes.
How much should they weigh? In order to work this out for your heifers, weigh at least 10 of the 6-8 year old cows in the herd around April/May when they are in body condition score 4.0 - 5.0. These animals should be at their mature liveweight and should give you a good guide of what you are aiming for.
Alternatively, you could use the formula in the InCalf book to calculate mature liveweight from the heifer's liveweight breeding value (Lwt BV). With your mature liveweight target established, the targets for the heifers are:
- 30% of mature liveweight by 6 months
- 60% of mature liveweight by 15 months
- 90% of mature liveweight by 22 months
Therefore, if the mature liveweight of your cows is 500kg then by six months your heifers should weigh 150kg, by nine months they should weigh 300kg and by 22 months they should be at 450kg.
The calving pattern of your first calvers will provide you with an indicator of how successful your heifer management has been. Top farmers achieve levels of 75% calved by week three of the calving period and 92% by week six. It is important to note that if your planned start of calving for the heifers is before the main herd, then your figures should be even higher. For example, if you calve two weeks earlier than the herd then your targets should be 87% by week three and 98% by week six of the herd's calving period. Totally Vets' technician, Guy Haynes, can help by coming out to weigh your heifers to assist with monitoring their progress.
Another area for assessment is the three-week submission rate of your first calvers. The target should be 90%!
Some other things to remember for the young stock are:
- Put in place a parasite control programme
- Don't forget clostridial/leptospirosis booster vaccinations to get them in sync with the main herd
- Protect them from facial eczema during the late summer/autumn period
- Make sure all trace elements are taken care of
If you have any questions or would like to discuss your heifer rearing, please contact one of the large animal vets at Totally Vets.
