Feeding pregnant cattle

Every year, I attend a field day hosted by the Government-owned Landcorp called Beef Cows 4 Profit. Its intention is to lift the productivity and profitability of its beef breeding herds by studying its population of around 30,000 Angus cows.

I have found the research tremendously interesting, primarily because the local farm — Takakuri, near Kaeo (the other two are on the East Coast and in South Otago)- is not dissimilar to mine in terms of its climate, terrain, soil types and pasture composition.

Such field days are of value to anyone with any number of animals and I encourage you to look out for them in your area. Be brave: lifestyle block owners do go to them!

One of the recurring issues discussed at the gatherings is levels of animal nutrition and body condition. New Zealand farmers have long been prone to underfeeding their cows. Beef breeding cows have usually been used as an adjunct to sheep production — keeping pastures in good order and cross-grazing for the good of sheep flocks — and have been used as a sacrificial animal in terms of available feed. They get the low-quality left-overs and they’ll still produce a saleable calf. Feed planning has been in terms of how much weight/condition a cow can be allowed to lose over the winter as she grazes poor quality feed to clean up pastures for better sheep production.

When I came to farming, that approach was strongly conveyed at field days as if it was the proper way to manage pregnancy in a cow, but that practice never sat very well with me.

After a few years I began to wonder what effect the underfeeding of pregnant cows might be having on their calves in the long term. Publication of research in the human field made for interesting reading: people whose mothers ate poor diets during pregnancy are being found to be more likely to develop various metabolic problems in adulthood.

My own small observation of my cow herd tells me that heifer calves which receive a good start to their lives, from before conception and onwards, become better animals as adults than those which did not. If an animal is severely challenged during pregnancy it would appear that her daughter will carry that legacy and even pass it on to her own daughters.

At the field days in more recent years, discussion has been aimed specifically at debunking the old belief that restricting feed to pregnant animals will control the size of the calves they are carrying. The actual time to control calf size is right back before mating day, by choosing a bull with a record for easy calving, and/or small calves.

In young, first-time-calving heifers, careful management is crucial. I still suggest that calving two-year-old heifers is not something to be taken on by anyone without some existing cattle-breeding experience, but if you do have young pregnant cattle, don’t believe the old story that if you keep heifers on tight rations they’ll calve more easily than otherwise.

As one of the participants said at the most recent field day, the calf is going to continue gaining around 300g each day, whether or not you feed its mother sufficiently. The mother will always prioritise resources to her baby, so if you starve her she’ll end up weak and thin (and possibly under-grown) and lacking energy when it comes time to give birth. She’ll have less milk and it’ll be of lesser quality than if she were properly nourished. Applying restrictions to a heifer which is still growing herself may seriously impact on her long-term production and her ability to do her job in the current season.

Getting young first-time-calvers back in calf the next season is sometimes tricky and you don’t want to make it even more difficult by having her in a poor state at first calving. However, note that rising three year old heifers calving for the first time and already nearing mature size can require careful management to ensure they don’t get too fat.

Cows are a bit easier to manage but their energy requirements during the latter part of pregnancy indicate how careful you have to be with their younger herd mates to ensure you get it right.

You can develop a good feel for how well to feed your animals, but it pays to back that up with some measurement and calculations. If you under or over-feed an animal, it will take a few weeks for her body condition to change enough for you to detect it.

If your pregnant heifer has been losing weight and you haven’t noticed it until she’s calved and her skeleton is suddenly starkly visible, you’ve got a lot of catching up to do on her condition and growth and you will have lost a lot of ground in terms of the calf’s start to its life.

Beef + Lamb NZ information tells me that for my 550kg cows at 12 weeks prior to calving, I should be providing an extra 12% feed above their ordinary maintenance requirements. At 7kg of dry matter per day, that means I have to provide nearer 8kg per day at that stage.

Four weeks later, their needs increase tc just over 20% above normal maintenance.

At four weeks before calving they need 36% more than maintenance.

At calving their needs escalate to over 60% above normal maintenance feed requirements.

Considering those figures, you can see that holding them tightly back on inadequate feed could have serious consequences. Cattle are robust creatures, but just because you don’t see any consequences of restricting their feed, it does not mean there aren’t any in terms of calf health, milk production, fertility and ongoing well-being.

Reassessing stock numbers

After several years of varyingly tricky farm management (the wettest winter on record followed a year and a half later by the worst drought in decades, then the most recent drought three years later) I’ve gradually downsized my herd.

I’ve also learnt a lot more about managing the animals better, particularly in regard to feed requirements and the wide-ranging effects of keeping them well-nourished. I did not do that well in early years and I am still improving my practices.

Pushing a property to its maximum level of possible production appears to be becoming more and more widely practised. Most people no longer farm with the pasture they’re able to grow on their own properties (eaten green in the growth periods of the year, excess harvested to feed out when growth is insufficient or non-existent), relying instead on the importation from near or far of supplementary feed, in some cases throughout the year.

While that can be economically viable, it can have high costs to the environment, and makes the practice unsustainable in the long term, although for many that long term exists beyond their farm ownership or lifetime and doesn’t concern them.

My inclination is to head in the other direction: reduce numbers to the point that our property is self-sufficient in feed. Luckily for me in the Far North’s climate, I can rely on the grass which grows all year rather than having to involve myself in hay or other supplement making during the summer. In a breeding herd, my stock numbers fluctuate during the year so that they match the feed growth.

Our property is just under 96ha (about 240 acres), but there are some large areas of fenced bush, along with lots of accidentally regenerating scrub areas, streams, tracks etc. With the help of a satellite picture, I initially estimated the effective grass-growing area to be around 46% of the farm, ie 44ha.

I calculated I’d grow 460kg of feed per day over the whole farm over winter (terrain and fertility affecting growth in different areas). But budgeting on that number last year, my cattle ended up coming out of winter in lesser condition than I wanted -1 believe I had their feed demand calculated correctly, but there wasn’t as much grass area as I thought.

I then reassessed the available grass areas and come up with a reduced 37.8ha over which I estimate I can grow a minimum 420kg of feed each day over winter. I make the assumption that my calving date (starting late September) means increasing spring growth will match the increasing needs of the pregnant cows and heifers at the end of their pregnancies.

Last year I had a daily winter feed demand of 435kg, but this year that will be down to 419kg, which fits within my newly calculated theoretical ability to grow grass. I have the same number of animals as last winter, but the age composition of the herd and consequent feed demand is different.

I think that I’m getting closer to working out the comfortable carrying capacity of the farm. This is all about lifestyle, after all, not stress!

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