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Supplementation

The goal of a supplementation or a supplement would be to promote utilization of the forage that the cow is consuming. As with other animals that are consuming forages, the supplementation should be used to complement or enhance forage utilization. We are going to switch from RUP, RDP to DIP, UIP. Remember, I said beef people are behind dairy people? So DIP supplements, this is degradable intake protein. Degradable supplements would be soybean meal, cottonseed meal, urea would be examples. Undegradable supplements, examples would be blood meal, fish meal, feather meal. You could also throw distiller's and brewer's in the undegradable supplements. Look at some energy supplements, corn, barley, beet pulp. Wheat midds would be one that would be a DIP supplement, but also an energy supplement.

If you had your choice what would you supplement with, an energy source or a protein source? I heard some proteins from the back of the room and they are right because protein is usually the first limiting nutrient in grazing production systems. So we would expect to see the greatest benefit from supplementing a protein source. We have chosen, we are going to supplement with a protein. Should you supplement with a degradable protein or an undegradable protein? Think about what the rumen microbes need, they need ammonia right? If they cannot degrade it, can they get any ammonia? No. And so your choice would be a DIP supplement because microbes use degradable protein to produce bacterial protein. Remember that bacterial protein is high quality, so it has a good amino acid profile. It is high in protein, about 80% protein. And it is also highly digestible, about 80% digestible. Secondly, so in addition to needing ammonia in the rumen, DIP supplements are often, almost always less expensive than UIP supplements. Remember, fish meal will cost about $550 per ton. What can you get soybean meal for now? Soybean meal is a DIP supplement. You could get it for $200 about a ton. That is less than protein, but it is cheaper on a percent protein basis or a pound basis.

Research has shown that if you supplement with undegraded sources, so UIP supplementation of low quality forage, it does not illicit the same positive response as DIP, or you may get a response, but you do not get the magnitude of the positive response. Something else you get with DIP sources, that you often do not get UIP sources because UIP sources are so high in protein, is DIP sources are usually also energy dense. They are somewhat similar to grains in TDN, but they also contain degradable protein. You get the added benefit of having additional energy, not just protein.

Next, let us look at an example of the effects the forage quality on the required level of intake. We will compare two forages, one is alfalfa, the other is winter range. And the example animal we are going to use is a lactating 2 year old heifer, it weighs about 1,000 pounds, producing about 12 pounds of milk per day and based upon NRC requirements, she would need to consume or would be able to consume about 22 pounds of dry matter a day. This heifer’s requirements would be 13.8 pounds of TDN or if we divide 13.8 pounds of TDN by 21.6 pounds of dry matter, this animal would need a TDN concentration of about 64%. If this animal was receiving alfalfa, which is about 66% TDN, she would need to consume about 21 pounds of intake per day, which is very close to that as estimated by the National Research Council. On winter range, which contains about 51% TDN, this animal would need to consume about 27 pounds of dry matter per day to meet her TDN requirement. This lactating two year old would also need about 2.25 pounds of crude protein or the concentration of protein in the diet would need to be about 10.4%. If we look back at alfalfa again, it would contain about 18% crude protein. So, 2.25 pounds of protein divided by .18, which is the protein concentration of alfalfa in the decimal form, this heifer would need to consume about 12.5 pounds of dry matter per day to meet her protein requirements. The winter range would contain somewhere around 5% protein. In order for this two year old heifer to meet her protein requirement, she would need to consume about 48 pounds of dry matter per day to meet her protein requirement.

What is first limiting in this example? Well, it would be protein, of course, because this heifer would need to consume about 48 pounds of protein to meet her requirement. It is unrealistic to assume that this heifer could consume 48 pounds of range to meet her protein requirement. It would probably also be a stretch to assume that she could consume 27 pounds of winter range to meet her energy requirement, simply because this is of moderate to poor quality. If this heifer was grazing range during the winter, she would probably be deficient in both TDN or energy and protein, with protein being the most deficient. Certainly with alfalfa we could meet her energy requirement because she probably would consume 21, 22 pounds per day on this quality alfalfa. And we will also meet, actually exceed, her protein requirement if the alfalfa did contain 18% crude protein. Often, we would supplement the winter range or our forage source with some kind of protein source. And we will see that in addition to supplying protein, it may actually increase energy intake or intake leading to an increase into energy intake.

If we look at protein supplementation, and this would be degradable intake protein or DIP, several functions is it will provide nitrogen for microbial growth in the rumen and this will promote improved fiber digestibility of our forage. At this point, the animal is willing to accommodate increased fill or simply eat more because digestion rates and passage rates increase. Actually, when you offer a degradable protein source to animals consuming poor quality forage, intake will increase and this is known as positive associative effects. This is increase in forage intake due to DIP supplementation. Often we see 25% increase in intake of a poor quality forage through simply providing an undegradable protein source. What about offering an energy source or a grain for energy supplementation of a poor quality forage? Often we will actually reduce microbial population in the rumen or we actually shift the population from cellulolytic bacteria, or bacteria that digest fiber, to more microbes that prefer to digest starch or the grain that we are feeding. It often leads to a depression in fiber digestion which will further depress forage intake and we often refer to this as a negative associative effect. The following table depicts the effects of a nonstructural carbohydrate or a grain on utilization of low quality forages.

We can see when the supplementation is at a low level or 0% to 10% of the diet, we usually do not affect digestibility or intake. When rate of incorporation would be 10% to 20% of the diet, we find that digestibility is depressed and intake is also depressed. As the grain mix makes up more of the diet, so for example greater than 30% of the diet, digestibility is depressed by 15% and intake can decline by as much as 40%.

Some rules of thumb for supplementation. Most often, we will first offer a degradable protein source. And the optimal percent crude protein in the supplement is somewhere in the range of 25% to 35%. If we were offering cottonseed meal or soybean meal, often we can add some grain to this to get a protein concentration of 25% to 35%. But if we want to go strictly with a grain or nonstructural carbohydrate to supplement low quality forages, we would keep the level of use of somewhere under 10%. What about offering additional forages or supplementing the poor quality range in the previous example with an alfalfa? Forages are structural carbohydrates and they are usually neutral in the terms of associative effects. They would not increase or decrease intake, the alfalfa would just offset the intake of poor quality forage.

If we go back and look at our example heifer which is consuming about 21 pounds of dry matter a day, we could offer her or feed her just over two pounds of grain per day or 10% of her diet as nonstructural carbs or grain to keep from encountering negative associative affects. Often a cheap protein source, actually a cheap nitrogen source, is urea. It is a good degradable or it is a degradable protein source. It is actually 100% degradable. There are some things that we should keep in mind when supplementing with urea. Generally, we see toxic affects when urea is at greater than 3% of dry matter. If we go back to our heifer example, this would be about a half a pound of urea per day. When animals consume more than this they experience nitrogen toxicity. Often we would not supplement urea simply by itself, we may combine it with another protein source and the optimal ratio would be about 30% urea with 70% natural protein.

There are several ways to deliver supplements to beef animals. One would be daily supplementation but often, based upon the location of our animals, this is neither economically or physically feasible. Actually, research at Oregon State has shown that we can achieve similar positive effects through either infrequent supplementation compared to daily supplementation. By infrequently, they have measured growth rates, body condition score, etc., some variable, based upon supplementation every second, third, or fourth day and found that there is no differences when we compare that to daily supplementation. Liquid tubs is another way to offer protein and energy to beef cattle. These are mainly, usually, in the form of molasses tubs and intake is generally controlled by palatability. The more palatable it is the more animals will consume. Lick blocks are another alternative. And intake is usually controlled by block hardness, the harder the block the lower level of intake they get from the block each day. Animals should always have free-choice mineral or salt blocks available when on range.

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