INTAKE VARIABILITY AFFECTS CATTLE'S PERFORMANCE

by: Stephen B. Blezinger
PhD, PAS

Part 1

A fairly common discussion in my office is why we see variation in performance in a group of cattle. In some cases this is explained by the fact that within any group of animals there are differences in the genetics of the individuals. Some are genetically predisposed to perform well, some not as much.

A more common cause may very well be the common variability we see in the intake of feeds and supplements. For cattle only on pasture, most animals will consume the base forage according to their requirements and this is fairly predictable. When supplements are thrown into the equation, especially if there are multiple sources, the intake dynamic changes, sometimes to a great degree. Often, when a producer is utilizing an extensive supplementation program, he may not recognize that intake variation may be significant until problems arise.

Most producers will provide some type of feed, mineral or other product to deliver a variety of nutrients, hopefully to meet all of the animal's nutritional needs. In the most basic sense this is necessary to help enhance performance (reproductive, health, growth) by providing for the shortcomings of the forage program. For breeding cattle this is the vast majority of their lives. For feeder cattle, this period is much shorter but still affects their overall performance and thus profitability.

This article will discuss the effects intake and intake variability has on the delivery of nutrients and other management components. We will take a look at how this variation affects the animal's performance and what can be done to minimize these issues.

Forage-based vs. Supplement-based Nutrient Delivery

For cattle on pasture or on a typical forage program (hay, silage, etc.), in most cases a large portion of their nutrient needs are “delivered” by the forage material they consume. This would include dry matter in general, then protein and carbohydrates, fibers and fat for energy, minerals and vitamins. Let's assume that there is an adequate amount of forage available to provide for this base. This has been and is an issue for many producers in drought-stricken areas where the availability of forge materials to only meet basic dry matter requirements has been a problem. For the purposes of this discussion, however, we'll assume this is adequate. Depending on the forage base, time or season of the year, etc. certain nutrient components are available in adequate supply for specific classes of cattle. For instance, in the southern United States during the spring and early summer months of the year, in most cases, a Bermuda grass based pasture will provide adequate crude protein for the most mature breeding cows. This will depend on pasture management, production stage and/or age of the cow and a variety of other factors. In many cases, this same system will also provide for her energy needs. Energy is the nutrient component that drives weight gain. Under normal conditions, during this time of year it is not uncommon for cattle to gain weight on grass alone. They will not gain the maximum amount they could if they were on an all-grain diet but nonetheless, their energy intake is adequate to provide for their requirements to gain weight. Less obvious is the delivery of minerals and vitamins. Forages are highly variable in terms of mineral and vitamin content. Mineral content is affected to a large degree by the mineral content of the soil which is in turn affected by fertilization programs, natural soil characteristics, location and previous management. As such, the ability for a given pasture to meet all the cow's mineral requirements at any given point in time is always questionable unless the producer has a fairly involved, ongoing, forage analysis program. Even this only tells him whether or not minerals are available in the plants during a given period or point in time.

Research has long shown the value of different types of supplementation for cattle operations. Depending on the variation of forages, time of the year, production stages and so on it may, at any given point, be necessary to supplement protein or energy in order to meet the cow's requirements above and beyond what the forage base provides. Minerals, on the other hand, generally require more consistent supplementation. Even when pastures or forages may provide all the protein and energy that the cow needs, one or more minerals may still be in short supply. Another scenario could be that the minerals are there to provide for the basic nutrient needs but one, such as sulfur, might be present in excess and thus interferes with the absorption of another such as copper.

Additionally, research has provided us with a number of performance enhancement products that can improve gains, health, reproduction, etc. and thus can help the producer be more profitable. For instance products such as Rumensin™, Bovatec™ or GainPro™ all help the grazing animal to better utilize the energy provided by the plant material and thus increase gains and efficiency (i.e. less feed/forage per lb. of gain). Melengesterol Acetate (MGA™) can be used to suppress estrus in mature, cycling females to either assist in heat synchronization or to keep them less active so gains will improve. Other products such as Chlortetracycline, Rabon, S-Methoprene™ (Altosid™) are commonly used to help improve performance by improving animal health or reducing fly populations.

The whole point behind this section is that regardless of the purpose, at some point producers generally want or need to provide something to their cattle that they cannot get from the forages they consume. As such they have a need to supplement these animals in some way.

Complications

Countless supplements are provided every year to deliver the variety of nutrients or management products that producers choose to use. Some are obviously better than others. Many are, more or less, exactly the same thing. Still others are custom formulated to meet very specific requirements. At this point we have to consider how these supplements are provided to the animal. Options include self-feeding or hand feeding. Supplements can be fed in feeders, troughs or on the ground (not recommended).

The key question here is “are all the animals in a given pasture or group consuming exactly the same amount of a given supplement – the amount needed to deliver the desired nutrients or additives to the animal?” The answer here is no, they are not all consuming the same level.

In only a relatively small number of isolated instances will a group of cattle be fed and receive the exact amount of feed or supplement they are supposed to. A for instance would be in a group of show calves that are fed individually in separate pens at each feeding. They can be given the specific amount they are to consume and, if they clean their plate, will consume the exact amount desired. This changes when these same cattle are fed in groups. If fed in groups at a community trough, intake variation between animals begins to come into play. For example, if the feeder has a group of six head and desires for each animal to consume 20 lbs. per head per day he may feed them twice per day with 10 lbs. per head at each feeding for a total of 60 lbs. per feeding. Out of that group he might have one “pig” that eats 15 lbs. at that feeding, another that eats 12 lbs., two head that eat 11 lbs. another that eats seven and the final calf that only gets four lbs. Let's put this number on a table:

As you can see, the amount of feed delivered verses the amount of feed consumed is the same. So, on the average, every calf is getting the same amount. But when specific intakes are considered, we see a huge variation. One that results in a dramatic over-consumption by some animals and significant under-consumption by others. In this situation one of the most obvious signs will be the one and two animals gaining significantly faster than the others in the group and that five and six will gain slower and appear to be “poor doers,” which, in fact they are, due to inadequate feed consumption. Of the group, only two head were eating close to what they were supposed to and even here, consuming 10 percent more may result in gains above projected performance. In a feedyard that's not a bad thing. In the show ring it can be.

Now take this same scenario and apply it to 100 head of cows on 200 acres of pasture. We can assume that, if the grass is plentiful each animal will eat each what she “needs.” This is not entirely true since you will also see some variation in forage intake between animals as well. Aside from the forage consumed, an excellent mineral supplement is provided to meet all the mineral and vitamin requirements for the cow herd on that pasture.

One thing that many producers do not understand about any type of supplementation is that you essentially have three groups of animals. One group eats about the right amount with only small deviations. While there is a small amount of variation among this group, for the most part they are getting about the right amount of whatever nutrient or additive from day to day (another area of discussion). Another group will be eating considerably more of the supplement than they should and as such they consume more than they need. Since too much of anything is not necessarily a good thing, problems can develop. In the case of a high energy supplement this is the group of individuals where you can see bloating, some sub acute acidosis, loose manure, etc. These are the fat, slick, aggressive cows that are the first to the trough, that push the more timid cows away and that are the last to leave. You can see cases of depressed reproductive performance with these cows as well since they may bee too fat or their protein intake can be too high thus decreasing fertility. In terms of mineral supplements, in extreme cases you could see incidences of toxicities but this is rare. The third group are those cows that for some reason eat significantly less than the targeted amount. Some may consume nothing at all. This may be related to individual preference or “taste.” It may be related to the fact that some cows are very timid and are easily bullied away by the more aggressive or “Boss” cows. This dynamic exists in EVERY group of animals, i.e. the development of a pecking order, of which certain cows sift to the bottom of the pile and are thus prone to lower consumption of feed and supplement. Secondly, this dynamic changes whenever cows are added or removed from the group. This is actually a greater problem in well or more intensively managed herds where producers work harder to group cattle by age, production phase, etc.

As such, if you back away and take a look at supplement intake as a whole across the entire herd of 100 head, you have the development of a common bell-curve graph. One end includes those cattle consuming little or nothing and as you work your way across the graph the numbers consuming close to the right amount or the right amount increases. As you go farther along the numbers that consume higher than desired to excessive amounts decreases as well. In most cases the numbers of animals that consume little or nothing is fairly low as are the animals that are simply off the chart of consumption levels (way too much). The point here is that this profile exists in ALL populations of animals. Even if you pull the extremes out, the group realigns itself to once again produce this result although the intake levels may change somewhat thus altering the shape of your graph. Nonetheless, the bell curve will reestablish itself because this is a biological system.

While the excessive consumption individuals can be a problem as discussed, the no to low consumption animals are the true point of our discussion here. In the next part of this discussion we will look at the implications of in adequate or erratic consumption of nutrients and how this affects performance. We'll then examine steps that can be taken to help reduce this problem and hopefully offset these issues.

Dr. Steve Blezinger is a management and nutritional consultant with an office in Sulphur Springs, TX. He can be reached at 667 CR 4711, Sulphur Springs, TX 75482, by phone at (903) 352-3475 or by e-mail at sblez@verizon.net. For more information you can visit follow us on Facebook at www.facebook/reveillelivestockconcepts.







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