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MINERAL INTAKE CRITICAL FOR REPRODUCTIVE PERFORMANCE

By: Dr. Stephen B. Blezinger
Ph.D, PAS

The old saying goes “if you don't get them bred, you're not going to accomplish much.” Over the years we have addressed nutrition's effect on the brood cow and this factor just cannot be minimized. We know the three sides of a beef operation – genetics, management and nutrition are important. We know the nutritional plane the cow is on directly affects breeding, gestation and parturition (calving). Over or underfeeding are equally detrimental to normal reproductive function. Nutrients out of balance are also detrimental. Protein and energy are the nutrient components needed in the largest quantities and directly effect condition scores and normal reproductive performance and we have covered this on several occasions in the past. For this article, however, we are going focus on another set of nutrients: the major and trace minerals and their importance. Not only will we look at the minerals but we'll discuss the need for a quality mineral supplementation program. One of the most common problems I see on cattle operations I visit and work with is the mineral program. Pound for pound, mineral supplements are the most expensive of all the nutrients we supplement. They are also fed in the smallest quantities. Pound for pound, they also may very well have the greatest impact on cow performance.

Mineral Forms and Intake

Free-choice, loose mineral supplementation is generally considered the most common mineral supplementation strategy in grazing beef herds. Unfortunately a lot of mineral blocks are still fed. These are typically the hard, red 50 lb. blocks that cows simply cannot lick enough of to meet their mineral needs. You will also still find a few ranchers that will put out salt (white or yellow) as a mineral block. These will not adequately provide for a herd's needs. In nearly all cases, however, use of a good quality, palatable, loose mineral product is an effective, cost-efficient means of delivering adequate vitamin and mineral supplementation to the cow. Although formulations vary greatly, the common base mix should contain approximately 8 to 10 percent salt, along with 8 to 12 percent phosphorus. The variation in phosphorus content typically creates the greatest influence on overall cost of the product.

Intake is often targeted at two to four ounces per head daily. Achieving this target intake by all animals does not occur. Several animals within a herd will consume very little to no mineral at all. However, on the average, mineral consumption usually meets the desired intake levels. It is this averaging effect, over time, which allows free-choice mineral supplements to be the most practical choice for most cattle producers.

In most areas, seasonal variation in mineral intake is evident. During the summer months, cattle readily consume well designed mineral supplements as they normally do winter months. This can commonly be linked to forage quality. As forage quality decreases, free-choice intake commonly increases. In spring and fall (after rainfall rejuvenates forages), intake may be greatly reduced. In a study by the University of Florida (Arthington, et al) the seasonal changes in mineral consumption were clearly noticeable (Figure 1). Cows were offered a weekly amount of mineral that was equal to their targeted intake of two ounces per head daily (14 ounces per cow weekly). The amount of mineral not consumed was weighed and removed each week. The results show that during the summer months, cows readily consume their two ounce per day allowance; however, during the winter months cows often consumed less than ½ of their two ounce allowance. These differences in mineral intake are likely due to several factors, but the most important contributors are probably the moisture content of the pasture forage and the presence of winter supplement. It is important to recognize that this was a pattern noticed in Florida and that other regions may vary on the intake patterns observed. The issue here is to understand that intake variations occur.


This information is important to consider when evaluating a mineral supplementation program. For instance, during some months cows may consume mineral at a rate that exceeds their targeted intake. In the study referenced above, mineral was offered at the two ounce per day level, but clearly they would have eaten more during the summer. Often this weekly allowance was completely consumed within four to five days. While some authorities will allow that there is nothing wrong with allowing the mineral feeder to remain empty for a couple days I would tend to disagree. Over-consumption of mineral is usually not considered a problem although, there is some evidence of reduced reproductive performance in heifers and young cows that consume too much mineral. The most pronounced impact of mineral overeating is economic, as the producer is receiving no additional benefit from the added costs realized by the additional mineral purchased. One should consider, however, that since mineral intake will vary one cannot assume to manage intake on a week to week basis. Intake should be assessed over a longer period of time (i.e. a month or 6 weeks). Over longer periods of time, assuming the mineral the producer is using is well designed and formulated properly, hitting target intakes are normally not a problem.

During periods when consumption is often reduced, such as spring and fall as mentioned above, try blending your mineral with your winter supplement. If you do not utilize winter supplements, or blending is unfeasible, try mixing your salt-based loose mineral mix with cottonseed meal or soy hulls at a one to one ratio. Remember to double your offer and monitor intake. An increase or decrease in this ratio may be used to control intake to your desired level. If you are purchasing a commercial feed supplement, ask your sales professional about the mineral content of the feed. In many situations, commercial winter supplements are fortified with a sufficient amount of mineral to meet a cow's requirements. When feeding these products the producer may be able to discontinue offering free-choice mineral or only offer stock salt. This may result in a substantial savings in a herd's annual mineral supplementation program.

Use of a Quality Product

I have had any number of situations where I consulted with a breeding operation (either commercial or purebred) where one of the most rapidly observable problems was mineral deficiency or inbalance. The root of this problem was based on one or more of several factors. These include:

1. Use of no mineral supplement at all.

2. Use of mineral blocks or trace mineralized salt blocks that do not allow for adequate intake.

3. Use of “economical” mineral supplements that, while inexpensive, do not provide the appropriate mineral levels or were low in palatability and subsequently did not allow for adequate intake.

4. Use of a poorly balanced product inappropriate for the given operation.

As we have discussed before, knowledge of your forages and use of forage testing is very important for the selection and design of a mineral. In the next issue we will revisit the process for determining what your mineral should look like.

Here are some things to consider/look for/stay away from in selecting a mineral supplement:

1. Color is not an issue. Many producers feel it is necessary to use a red mineral. Normally, red colored minerals include iron oxide to achieve this red color. This provides no nutritional value since the iron in iron oxide is very poorly available to the animal. Other commercial products use coloring agents as well. This may be effective as a sales and marketing tool but the benefit typically ends there.

2. Stay away from high salt levels. If high salt is required to get an animal to consume a mineral supplement there are probably other problems present. High salt levels, in many cases are used to reduce product cost.

3. Stay away from high Calcium levels (18 percent or more) especially when this is combined with low phosphorus levels Ca to P should be 1:1 to 1.3:1. It's not all that common for a given ranch to be deficient in calcium (it is possible however). Once again this is a cost control issue.

4. Look carefully at the supplement tag. Ask about ingredients that you do not recognize. In many cases any number of “bells and whistles” may be added to provide as tag dressing to make the product appear more valuable than it really is. Generally, free-choice minerals for beef cows do not require B-Vitamins (thiamine, riboflavin, etc.) unless some unique situation is present in the area or on your farm or ranch. Beef cows grazing forages normally produce all the B-vitamins they need by the bacterial action in the rumen.

5. Use of organic trace mineral sources can be valuable in the right application. Organics are more available to the animal than inorganic sources and can thus improve absorption of those nutrients. However, they are not required year-round. Use of organics is valuable from about 30 days prior to calving through rebreeding. After that they can come out subsequently reducing product cost.

6. Trace mineral sources should be from sulfates. Oxides, with the exception of Magnesium oxide are generally poorly absorbed.

Other issues to watch out are processes such as “weatherizing” which adds significant cost to a mineral supplement. Normally, if a product is well designed and palatable, setting up is not a problem since adequate consumption will reduce the incidence of the product getting hard in the feeder. Use of good quality feeders that protect the product from the elements are also helpful.

Conclusions

As we've discussed in the past, use of a quality mineral supplement is an important part of a good breeding program. Producers need to be attentive to how a product is designed and the overall product quality when making a choice on a free-choice mineral product.

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) 885-7992 or my e-mail at sblez@peoplescom.net.

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