Tuesday, February 27, 2024

Supplements: if there’s enough pasture, pasture is enough

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It’s time to consider the cost of supplements – in cash and in time spent feeding them out.
If cows are in good condition and receiving good nutrition during mating, supplementary feed may not be required as it is only one factor affecting reproduction.
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As mating approaches, it’s time to consider the cost of supplements and the time spent feeding them out – time that might be better spent on heat detection.

Can cows get in calf on a pasture-only diet? 
Yes. If there’s adequate feed, such as pasture residuals of 1500kg-1600kg DM/ha and good pasture allocation, there are no reproductive benefits from feeding additional supplements. Also, if intakes are restricted during the mating period (due to a feed deficit, prolonged adverse weather or poor pasture utilisation) then reduced reproduction is likely to be less than expected. 

Can I take out supplements during mating? 
Yes, if energy supplied by pasture is adequate. Past research shows there’s no impact on submission, conception, six-week in-calf or final pregnancy rates when dietary supplements are removed just before mating. 

Isn’t nutrition the main factor affecting reproduction? 
No, it’s only one factor. Others are genetics, bull management, heat detection, cow health, calving pattern, heifer management, non-cyclers, and cow condition at calving and mating.

Does body condition score affect reproduction? 
BCS at mating is a key driver of cow cycling and the six-week in-calf rate. This is largely set by BCS at calving (so aim for targets of 5.5 for two- and three-year-olds and 5.0 for older cows). Cows naturally lose body condition after calving, based on genetics and BCS at calving. Providing additional feed would have little effect on reducing this loss. Instead, focus on achieving target grazing residuals so there’s good quality pasture available during mating. 

So, what’s the best decision? 
It’s up to you to decide whether the cost (including time and labour) involved in feeding out supplements is justified by need and any benefits. If you do decide to use supplements, it doesn’t matter what kind; it’s the megajoules of metabolisable energy per kilogram of dry matter (MJME/kg DM), and the cost, that count.

Key points 
1. Save your time and money: if there is enough pasture, pasture is enough. 
2. In most cases, you’ll only need to feed supplements if there is a deficit in early lactation. 
3. Choose supplements based on cents/MJ ME – focus on feed energy, not type of feed.

More: The information in this article was sourced from DairyNZ’s Feeding Cows in Spring booklet at dairynz.co.nz/publications/feed

This article first appeared in the September issue of Dairy Farmer.

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