Dr Andrew Dale concentrate strategies for grazing cows webinar Q&A session part 1

Published 19 June 15

A recent webinar by grassland research, Dr Andrew Dale from AFBI, on concentrate strategies for grazing cows covered a wide range of topics, from substitution rates to the cost-effectiveness of supplementation, and generated a wide range of questions from the audience. Part 1 of the questions is summarised below.

During the spring flush of grass, when protein levels can be as high as 30%, how can supplements be used to balance the diet?

The conditions can, without a doubt be challenging. In very intensive grazing situations where 90% of the diet is grass, it will not be possible to balance a 30% crude protein content with only a small amount of concentrate, to bring it down to the target dietary content of 16%.  However, we have done work in the past successfully feeding 2–3kg of a 13% or even 9% crude protein concentrate with minimal impact on performance of the herd.

But in a moderate input system, feeding 6–8kg concentrate/cow/day, there is more scope to adjust components of the ration. Some care is required in this scenario, however, as reducing concentrate protein levels can impact on performance, particularly if very low protein levels are fed. Energy levels must also be considered.

However, even before the balance of nutrients in the diet is addressed, nutritionally it’s a huge challenge to maintain dry matter intakes (DMI) from grass in early spring. Strategies such as on-off grazing to encourage cows to activity graze for short periods of time are important. Often digestive upsets can be due to cows being put off eating low DM grass reducing intakes, rather than the nutritional content of grass.

How does supplementing with forages compare to supplementing with concentrate?

This depends on a farm-by-farm approach. There are two factors to bear in mind. Firstly, converting grass into a conserved forage puts on a cost and you could ultimately produce a lower quality feed. Secondly, substitution can be 1:1, ie one kg of silage will displace one kg of grass intake in the worst case scenario. In some situations, this could put the animal under more nutritional stress by giving them 11 ME silage, displacing 12 ME grass.

However, there are situations with limited grazing platforms, where it is vital to fill the gap between availability of fresh grass and the feed demand. And although conserved forage is more expensive then grass it is a lot cheaper than concentrate.

But conserved forage needs to be carefully managed and the emphasis must be on maximising the quality of that forage. The best grass management farms will make silage from covers just over what you would normally graze, so that when they do feed it, the silage is nutritionally close to what the cows were getting at grass. This is very different from a one or two cut silage system, where quality is much lower than fresh grass.

Would feeding the daily allowance of concentrate in one feed have any effects on grass intakes?

It really depends on the level of concentrate. If we are talking about feeding 2–3kg of concentrate/cow/day, it is possible to feed at only one milking. But for some of these studies we were feeding up to 10kg/day, which is not possible in one visit to the parlour. From a practical point of view it would be almost impossible for the cow to eat that during one milking and, from a rumen health point of view, it would not be ideal.

If you are feeding at only one milking (around the 2–3kg range), think about not feeding at the afternoon milking, as it will help focus the cow on maximising her main grazing point in the evening, before dark. However, feeding twice daily is often adopted for management reasons, adding some incentive for the cows to come into the parlour!

What sort of grass management system increases intakes?

Offering fresh grass to cows once a day seems to be comparable, in intakes, to offering fresh grass twice a day, and many good grass management farms are now giving cows a three grazing break. This means cows are only trying to hit residuals once in every three grazings. Overall, they spend less time chasing this residual, which can restrict the animal’s intakes.

The flip side of this is that you do need to back fence or keep the cows moving. Having them in a large field taking 5–6 days to graze, means they will come back and nip off all the fresh growth without back fencing.

You need to keep in mind that you are maximising the performance of the cow and the paddock, so try and grow as much grass as you can. The higher the yield from a paddock, the cheaper your overall grass costs will be.

How did the cows within the study manage weight loss and gain in the flat rate and feed to yield feeding systems?

This is one aspect we have been investigating a little further. Typically, we would expect in a flat rate system that the lower yielding (LY) cows would potentially be overfed and the high yielding (HY) would potentially be underfed. This is as opposed to the feed to yield system where nutritional demands would be better balanced.

Whenever we plotted the results, we ended up with a graph that was comparable to a flat X. As you would expect, the yields of the LY cows on the feed to yield system were lower than the flat rate LY cows and conversely for the other end of the spectrum. 

Q&A flat line

Not unexpectedly, the yield across, from high to lows, were flatter on the flat rate system, so essentially the cows adjusted to the flat rate system; the HY cows coming back in yield and the LY moving up a bit, if anything.

This means that the extremes of over and underfeeding that we were expecting weren’t there. Even looking at the means, we found very little difference, in fact we found no difference in terms of any of the blood parameters we were taking or the liveweight condition score of the cows at the two extremes of the scale.

Averages can sometimes hide a lot but even when we subdivided into extremes of high and low yielding cows we still found very little difference. The one thing to bear in mind is that the range of yields was potentially not as big as in an all-year-round calving system. The cows were certainly well past peak and into mid to late lactation, and levels of concentrate going in were relatively modest (3–4kg). At higher levels, we would have seen a level of underfeeding.

The other aspect of this study is that the flat rate was based on the average cow and, sometimes, you will find farmers will tend to set up their rates to look after the potentially higher yielding cows. Therefore, there will be potentially more overfeeding of low yielders, having a bigger impact on substitution. The type of animals we had and the way we set up the flat rate feeding meant we weren’t getting the extremes of overfeeding.