Your Future Herd Replacements

Many herd replacements are now grazed off farm, with the subsequent need to rely on the graziers to do the best job possible. Many grazing contracts for a set fee do not include any incentive for the grazier to perform. Many farmers blame the grazier for the return of poor heifers to calve.

Now that the calf-rearing season is almost over again, it is time to reflect and assess your future herd replacements.

Many herd replacements are now grazed off farm, with the subsequent need to rely on the graziers to do the best job possible.

Many grazing contracts for a set fee do not include any incentive for the grazier to perform. Many farmers blame the grazier for the return of poor heifers to calve.

So what do you need to do to ensure your heifers arriving home in calf, are going to perform up to your expectations, and their potential, once they calve.

1. Do your calves measure up at weaning?

Accepted criteria for weaning heifer replacements include

• Weaning weights of Friesian 85kg liveweight Jersey 70kg
• Age of 10 weeks
• Consumption of about 1kg meal per calf per day.

It is usual that weaning is carried out with a combination of the 3 above factors.
With the emphasis in recent years on early rumen development, low cost rearing, and less milk fed, some very poor calves have been weaned. Recent research has shown that if calves are lighter at weaning due to lower feeding level then they are unlikely to make up that deficit.

Three groups of calves were offered 3 levels of milk replacer plus ad-lib calf pellets, hay and pasture. Liveweights of the 3 groups out to 135 days were as tabulated

Milk replacer allowance
High Medium Low
Day 65 69.8 66.2 66.3
Day 86 83.4 79.9 78.7
Day 135 108.2 100.9 101.2

So it is clear that the birth to weaning period is the most important phase in setting the standard for good herd replacements.

2. Do your yearlings measure up at first mating?

A study in Victoria, in commercial herds, has shown that the weight of yearlings at first mating, had a positive association on pregnancy outcome. The higher the weight, the better the pregnancy rate.
A lower weight at first mating, is also associated with lower submission rates in the first lactation.

3. Do your heifers measure up at first calving?

Improved milk production in the first lactation, has also been shown to be linked positively, to heifer liveweight.
Increased heifer liveweight at first calving also has a positive effect on survival rates in the herd, ensuring a higher proportion of cows in more profitable lactations.

Herd A Herd B
Liveweight at 18mths 385kg 315kg
Liveweight at 30 mths 405kg 365kg
% heifers surviving 1st lactation 100 78
% heifers surviving 2nd lactation 90 60
% heifers surviving 3rd lactation 80 59
% heifers surviving 4th lactation 70 55

There are clearly benefits to be gained from growing your heifer replacements well.
The benefits are probably greater than in just improving herd genetics.
Why then is there so little attention paid to the young herd replacement?
The benefits from improved weights are real, so lets give those valuable replacements a fair go, monitor and make changes to improve the growth rates.

So what are the liveweight targets we need to aim for, and compare with, when we monitor our young herd progress.

Our targets for your young herd replacements

A revised group average liveweight target (from NZGC analysis of records)

Age 4mth 9 mth 14 mth 21 mth 24 mth Mature
Start mating Pre
calving % mature weight 23 37 54 80 88
Friesian 130 210 300 460 500 570
Jersey 105 165 240 355 385 440

Lindsay Rowe
Dairy Consultant
Intelact Nutrition
Manawatu Vet Services