How much is your free forage analysis really costing you?

NIRS has an important role to play in forage analysis, but its limitations are widely known. Michael Carpenter, Kelvin Cave’s technical director, discusses how industry research is highlighting its shortcomings, and what alternatives should be considered for mixed and novel crops.

The best things in life are free, or so they say. This may be true for health and happiness but, in business, it’s rarely the case and you almost always get what you pay for. At this time of year, many of you are investing in preservatives, sheeting and other management products. And earlier in the season, you would have bought seed, fertilisers and sprays to ensure your homegrown forages and cereals are the best they can be in order to maximise milk yield or daily liveweight gain from home-grown feeds. Getting this right not only optimises animal performance and profit but also reduces the amount of purchased supplementary feed required and reduces carbon footprint.

So, as more herbal leys, multi-species swards, bi-cropping and other diverse species are grown, it becomes more important to make a relatively small investment in a full wet chemistry analysis. The same is true with crimped cereals.

Wet chemistry provides an accurate analysis of a forage’s nutrient composition, by treating the forage in a laboratory using various proven scientific processes using heat or chemical reagents. (These processes are described by AOAC International – Official Methods of Analysis.) Although wet chemistry is considered to be the gold standard in forage analysis, with a far greater accuracy than NIRS, it has a much higher cost and slower reporting of results.

Professor Stephen Hawking once said: ‘The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge.’ In the case or rationing, this is very true.

If a nutritionist inputs inaccurate data into a rationing programme which they believe to be true, despite their best efforts, the likely outcome is that the diet will not effectively meet the animal’s needs, resulting in a loss of performance or a reduction in cost-effectiveness of the ration. If the results are very inaccurate then it could also lead to metabolic problems such as acidosis, or reduced fertility.

The graphs below show the wide discrepancy between NIRS and wet chemistry of the same samples, with NIRS generally overestimating protein and seriously under-estimating starch. These discrepancies can have significant effects on diet formulation, particularly when larger quantities of the inaccurately analysed ingredient are included in the animal’s ration. This would be the case in beef diets where wholecrop beans are often the only forage.

This work was presented to a well-respected FAA (Forage Analysis Assurance) accredited laboratory by Dr Davies and highlighted the need for significant work on their part in order to build a more robust calibration for mixed species and novel forages. To their credit, they are no longer accepting samples of wholecrop beans for analysis by NIRS.

The differences between NIRS and wet chemistry are highly likely to be similar in other less common forages.

Even with wet chemistry analysis the metabolisable energy (ME) figure is still often not accurate as ME is normally calculated using the formula D value x 0.16. But there are no true digestibility figures for wholecrop beans and the only way this could be obtained would be to feed bean silages to cattle, measure dry matter intake and faecal DM output to calculate a true digestibility.

The calculation currently used relies on NCGD (neutral cellulase gammanase digestibility) which is an enzyme-based technique to estimate digestibility, using the formula 0.14 x NCGD + 0.25 x oil b.

For all but the most common forages which will have robust data behind them, a growing number of our customers are seeing significant returns by investing in wet chemistry to optimise diets.