Wednesday, July 6, 2022

Measuring a must

In a discussion group this month there was comment about fertiliser choices. We were on a below-average hill-country farm being transformed by a new owner into a well above-average one. This is truly the most effective way to lift farm productivity – that is, for the low-performing farms to be taken over by progressive owners. No amount of extension to the original owner would achieve this outcome.

But back to the discussion about fertiliser choices where there was a sentiment that some alternatives could be used. Certainly lime was put forward, but this is hardly an alternative. What was of interest to me was that what we know as “tried and tested” in getting the major macro-elements up to satisfactory levels to underpin maximisation of pasture production was not contested. The massive increase in productivity on farmland during the past 50 years is in part testament to this soil science being applied.

Yet users of alternatives were being quoted and their productivity being given as evidence. As often discussed before, unless we measure, we do not really know what is happening. What is more, we see what we expect to see. Whether it is vitamin supplements, digestion modifiers or humus, any gains can be substantiated only by measuring.

For such measuring to be valid it has to be of sufficient numbers, it has to have an equal sized control, the treated and control parts have to be of equal status at the start, and any difference needs to be differentiated from a difference created by chance. Most farm-based trials do not meet many, or often any, of these requirements.

A trial I did last spring looking at production responses to drench capsules on one farm gave a 0.7kg weaning weight gain to the lambs weaned from capsule ewes. When analysed properly this was not a significant difference. This difference could have happened by chance. In trying to do this trial it was extremely difficult to get two equal groups at the start. Just randomly allocating ewes to one group or the other gave one mob over half a condition score advantage. To have carried on with these two groups as initially drafted would have given an advantage to one group. Condition score at lambing is an important driver of ewe lactation performance. It took a lot of sorting before I had two groups that I was happy to call of equal status. How often do we do that level of balancing in on-farm trials? Yet we are happy to take most trial results without questioning their validity.

At the same day during which the fertiliser discussion was had there was almost passing discussion or little interest in the fact that the farmer was buying a superior sire bull (via AI) to generate herd bulls for his own use. It certainly was cheaper than buying high-performing bulls, but is the genetic gain being slowed enough to make up for the lower cost in sires?

If somehow the females for AI could be selected based on some production measure then perhaps the delay in genetic gain would be lessened. In a commercial herd that is calved unsupervised the opportunity to identify superior cows is limited. Maybe just identifying the heaviest heifer calves at weaning and letting them mother up again would select for either the early calving cows and/or the cows that grow the biggest calves, both of which enhance production.

What prompted my interest in this was that earlier in the week I was on a Wairarapa sheep stud farm. I was so impressed with what I saw that I thought that many hill-country flocks would do well to get these genetics in as fast as possible. The SIL data was impressive but when I observed the production environment and the uncompromising selection for that loose term “robustness” I was even more impressed. Seeing four-plus thousand ewes in a well-managed rotation on hills is a sight to behold. Diluting those genetics through breeding your own sires would be costly in delaying the benefits.

On the same discussion group day I was able to show that the farm was just well enough set up for the winter and spring. The pasture cover was just enough, the supplements available ahead were substantial, and nitrogen had just gone on, but such a conclusion can be made only after looking at the supply/demand curve for the next few months.

In several forums of late when the discussion has been about getting set up for next season I am asked what that magical May 1 pasture cover should be. I have no idea without doing some calculations specific to each farming system. On most farms that run out of feed late in the winter, such an outcome was predictable at the start of winter. This is a whole area that is poorly acknowledged, promoted or given extension priority by the industry. Yet it is the cornerstone of setting up next season. It is more important than agonising over lambing pasture covers. 

  • Trevor Cook, veterinarian, Manawatu.
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