Mixing it with sheep and cattle

BY: TREVOR COOK

When working with farmers in all of the northern hemisphere countries I have been to, it was almost a common surprise that sheep and cattle could run together.

Monoculture systems are more common than here, but running them together was for most unheard of. In our sheep and beef sector, monoculture systems are common but mostly associated with finishing enterprises. Mind you, some almost 100% sheep hill country systems do exist in the South Island.

For these northern farmers it was the fact that the sheep and cattle grazed together that was the surprise. But a lot of that surprise was because using pastures as the primary feed resource was still either a novelty or being mastered. So why is it standard practice here?

Theoretically it should only happen when the two stock classes have the same feed demand. So cows with ewes over the winter is common and clearly both have similar feed demands.

Calving cows with lambing ewes is common but very often does not meet the feed demand of each. Cows more often than not seem to be underfed.

It is one of the aspects of our hill country systems that defies our knowledge because I am frequently surprised how well those cows perform. Obviously not at their peak, but amazingly well for how little they appear to have consumed. Maybe there is more feed available than appears to be.

Having cattle with sheep is very often justified on them keeping pasture quality. The cattle will eat that rough pasture. Really? Given the choice they will target the best stuff as much as the sheep do.

It really will be only when pasture covers get below 1200kg drymatter/ha that the cattle cannot compete for the better quality pasture. The competition from co-grazing cattle with growing sheep will always detract from the sheep performance unless pasture covers are very low.

Are there other benefits from grazing sheep and cattle together? The one that is most often cited is in reducing the worm challenge to the sheep. I think this effect is massively over-stated as an outcome. Just how much of this occurs will depend on the sheep-to-cattle ratio, the length of the rotation and the feed levels.

At best having the cattle with the sheep dilutes the worm contamination level. Instead of 15 lambs per hectare there are 12 because there are cattle, so there will be less contamination. But in reality that level of contamination needs to drop by over 50% to make any difference.

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I do not see farmers drenching lambs any less frequently when they are sharing their grazing with cattle. But is that just because the 28-day need to drench is so ingrained that it happens regardless of the challenge?

On any day in the summer and autumn whether a lamb consumes 5000 L3 per day or 8000 makes little difference. It is not until it only consumes 1500 per day that we see significant lifts in liveweight gain. Having some cattle with lambs is unlikely to give that benefit.

If we are to use cattle to make a real difference instead of improving pasture quality they need to be grazed in a much more planned way.

First they need to be grazed on their own. This is not to clean up the sheep worms but to stop further contamination from sheep. They need to graze on their own for long enough for the pasture contamination from sheep to subside.

This is an area that we still need to know more about because I have been caught out by how long sheep-contaminated pasture has remained high enough to parasitise lambs despite several months of cattle grazing. But generally using cattle to “clean” up sheep-contaminated pastures does work.

It takes time and the time of the year is important as to how effective that is. For example, grazing sheep pasture with cattle for the winter and expecting it to be much lower in contamination by the end of the spring is unlikely.

What I find though is that it all takes more than a year. By that I mean applying strict inter-grazing to lower the level of worm challenge is an accumulating benefit. The second year gives much better outcomes than the first year, for example.

Very long rotations with cattle as part of it, but not with the lambs, is the concept I am most excited about. Perfecting that requires some quite lateral thinking on a hill country farm. That can go hand-in-hand with some of that thinking into other parts of our farming.

RESISTANCE AND PRODUCTION NOT MUTUALLY EXCLUSIVE

BY: LYNDA GRAY

GENETIC SELECTION FOR PARASITE

resistant sheep need not be at the expense of production traits.

That’s one of the key messages from Kathryn McRae, an AgResearch scientist.

The best way farmers could incorporate the benefit of this trait while pursuing chosen production goals was to select rams using the NZ maternal worth index and the additional trait of WormFEC (NZMW+F).

However, McRae, who has a special interest in the genetics underpinning disease resistance, says genetic selection is not a quick fix for the increasing problem of anthelmintic resistance in sheep parasites.

“The breeding of sheep with an increased ability to resist infection is one tool. It’s a permanent tool, but it takes generations of breeding for the benefits to accrue.”

Presenting at the New Zealand Veterinary Association conference in June she summarised the key findings of research over the last 25 years about breeding for internal parasite resistance in sheep.

One of the projects had dispelled the popular view that parasite-resistant sheep had more dags than non-resistant sheep.

The 2012 project by a PhD student involving a comparative analysis of 45,000 dag records and 130,000 FEC records showed a very low correlation between parasite resistance and dagginess. That meant selection according to a low dag score was not at the expense of parasite resistance, McRae said.

“Dags, or lack of them is a heritable trait and something that ram breeders could be recording to make genetic progress. They’re easy and free to measure.”

Research had also proved that resistance to internal parasites was geographically transferable.

“While some may believe it's better to select and use rams within a specific environment or geographical region, that's not the case with parasite resistance.”

The next 25 years of research would likely include DNA identification of larvae species from faecal samples.

“If we can look at the breakdown of species within faecal egg counts, it may provide additional information that could help in the breeding of more resistant sheep.”

Another likely project was to identify the typical behaviours of sheep whose health is compromised through parasite infection. The measurement of the time a sheep spent moving, resting, or ruminating with devices such as GPS collars and accelerometers would help with gathering this information.

“That type of research is already happening in the dairy industry and we’re hoping that as the technology advances and gets cheaper we’ll be able to adapt it for the sheep industry.”

The microbiome – DNA markers of microorganisms - within a faecal or rumen sample was another new and future arm of research that could provide more insight about the interaction between sheep and the parasites responsible for infection.