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Label Gazing-Why a calf’s assessment of a feed might tell you more than the label
A colleague told me earlier this year that he had been asked several times to explain how feed could be assessed from the details on its declaration label.
Labels are a legal requirement and every detail is laid out in the feed regulations.
Labels are seen as a tool for farmers and others to assess feed but it’s a truism that when what is important can’t be measured, then what can be measured becomes important.
Let me explain. Calves, as well as dairy cows, require absorbable amino acids but this would be expensive to measure. We could try to determine the protein content in the diet but again that would be cumbersome and of less value so instead we must record crude protein or what should be called ‘could be’ protein. This is because it is purely a measure of the nitrogen content of the diet multiplied by a coefficient to convert it into crude protein.
It can be useful for feeds using plant-based ingredients only but when it comes to milk replacers the coefficient used overestimates the protein content of the cheaper calf milks and underestimates the protein value of skim milk and whey based diets. (see Table 1).
Table 1
N content of Feeds
N content of protein | Variance to std coefficient | |
Milk | 14% | Under declaration of 1%+ |
Plant protein | 17.5 | Over declaration of 1% + |
Coefficient | 16% taken as standard for label declaration |
If we consider ash content, in plant-based feeds, the ash level is low so the impression is that the lower the better, but a reason children should consume cow’s milk and not plant-based alternatives is because dairy milk is full of the calcium and phosphorus needed for bone development (Table 2). Calcium and phosphorus are ash so again the more milk the higher the ash content. For calf milk, 7.5% is the sweet spot but not if it comes from adding additional calcium or limestone to the feed.
Table 2 Mineral content of milk or plant ingredients
Feed | Calcium content (%) | Phosphorus (%) |
Milk powder | 1 | 0.9 |
Plant protein | 0.15 | 0.1 |
If we consider trace elements and vitamins, what is declared is what it is added but many ingredients are natural sources of these additives.
An example is vitamin E. In certain parts of the world lard is used as the main source of fat in calf milk, but in the UK plant oils are exclusively used.
As can be seen from Table 3, plant oils contain a lot of vitamin E, though the types may vary in effectiveness. Therefore, again, looking at the label and comparing it to trial work involving different fat sources can be misleading.
Vitamin E content of fats used in milk replacers
Feed | Vitamin E (all sources) |
lard | 60mg/kg |
Plant oils | 130-800mg/kg |
The ingredients list is often seen as a clue but those without experience in the feed industry assume a commodity is a commodity. Tell that to a buyer sourcing wheat for biscuit making, or barley for brewing. They will have intimate knowledge of what sources work for them, and what don’t.
Knowing where the commodity comes from, how it is stored and how it is processed are key to producing consistently good feed.
Many years ago, in a different company, a supplier of whey powder suddenly increased crude protein content. We investigated this and found the company had started to use ammonium chloride (NH4 Cl) to neutralise the whey before drying. The N in the NH4 increases the crude protein of the whey powder but this is not what we, or the calf, wanted.
Milk powders change with heat treatment – see QR code. Skim milk powder dried for food tends to be high heat so sourcing product from companies that dry their milk ingredients from raw fresh milk is more important than the percentage of skim milk powder.
We are stuck with the label format for now and the error strewn crude protein system. There are effective ways now of declaring amino acid content but no convention on how to declare it.
Good advisers therefore look at the calves not the label. And, even better, they start with the end point, the cows – scrutinising everything from their longevity and the calving index of heifers to how many heifers reared to eight weeks are entering the milking herd and if all heifers are ovulating at 13-14 months and are at target weights.
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