Why Do We Feed Fats in Animal Rations
Fats and Oils
The next section is fats and oils. We add fats or oils to rations to actually increase energy density. If we look at most common grains and forages, they will contain about 2% to 3% fat. A couple of the reasons that we add fat is, one, intake is often a limiting factor in high producing cows. And fats are at least two and a quarter times greater in energy concentration than carbohydrates. We can replace highly fermentable carbs, such as one pound of ground corn, which has .88 megacals of NEL, with one pound of animal vegetable fat, which has 2.65 megacals of NEL per pound. So we can replace fermentable carbs with fat and actually increase energy density and maybe increase rumen environment because we are providing less non-fiber carbohydrates. However, we cannot add too much fat because it will impair fiber digestion and therefore reduce feed intake.
There are a couple of problems with fats. And the two forms of fats that we can feed cows.
Unsaturated fats are fats that have more than one double bond, one or more double bonds, depress fiber digestion more severely than saturated fats. A good example of unsaturated fat is vegetable oil. We could feed saturated fats. However, the disadvantage of these is that they are less digestible in the small intestine than unsaturated fats. Usually, we feed a combination of both to prevent negative effects in the rumen, but get the highest level of digestibility in the small intestine as possible. We can break down feeding fat into three phases.
So we have some arbitrary amount of fat along the X-axis, this would be percent, maybe increasing from 1% to 10%. Then we have some milk response, either no response, a negative response or a positive response. During phase one, as we continue to add more fat to the diet, we actually increase energy density, and so cows produce more milk. During phase two; we are starting to have some negative effects on rumen fermentation by adding more fat. We continue to increase energy density with each pound of fat we add, but intake declines in so the level of energy intake remains the same. During phase three, we are adding so much fat that it becomes counter-productive or for each increment of fat we add we drive intake down more than that. Animals are actually consuming less calories per day. The most profitable point or economical point on this graph would be where phase one and phase two meet. We have continued to increase energy intake, but we have not interfered with rumen fermentation. Unsaturated fats are more detrimental in the rumen than saturated fats.
The first two are actually protected fats.
| % UFA | |
|---|---|
| Energy Booster | 15 |
| Megalac | 50 |
| Beef Tallow | 45 |
| Animal-Vegetable | 52 |
| Palm Oil | 53 |
| Restaurant Grease | 71 |
| Cottonseed Oil | 72 |
| Soybean Oil | 85 |
| Canola Oil | 90 |
These are protected in such a way that they are rumen inert and they simply pass to the small intestine. Beyond that we have some unprotected sources. The first would be beef tallow, which is relatively low in unsaturated fatty acids, which means it would have less of an effect in the rumen. But again, since it is relatively low in unsaturated fats, digestibility would be lower in the small intestine. A few other ingredients on this table are vegetable-animal blends of fats, palm oil, restaurant grease, cottonseed oil, soybean oil and canola. You will notice that canola is the highest in unsaturated fats, about 90%. Canola oil would be the most detrimental in the rumen.
How much fat can we add to dairy diets? Generally, there is 2% to 3% naturally occurring in grains or forages. We could add another 3% to this from unprotected sources. Sources such as animal-vegetable blends, restaurant grease, palm oil, etc. Now, we are looking at a total of about 5% to 6% fat in the ration. If we want to go beyond this, we would have to add sources that are protected in the rumen and these would be commercial sources such as Megalac and Energy Booster.
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Source: https://courses.ecampus.oregonstate.edu/ans312/seven/cows_3_trans.htm