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FINE-TUNED NUTRITIONAL PROGRAM ENHANCES REPRODUCTION

Steve Blezinger
Ph.D.

From time to time we have touched on various components of nutrition and the subsequent effects these factors have on reproductive performance. Obviously, these factors are important whether you are a commercial or purebred cattle producer. With the emphasis in this issue on purebred herds I am going to focus this on purebred cattle but the principles are just as applicable for the commercial cattle producer. Also, later in this article I want to give you a checklist that can be used to fine-tune your nutritional program to insure that you are "firing on all your pistons."

While reproductive performance is vital to all breeding operations, purebred breeders commonly use not only natural servicing but also artificial insemination and embryo transfer programs to maximize their ability to produce the desired genetics in the most cost effective or productive form. Through my experience in working with purebred breeders that implement programs of this nature the need is even greater here to utilize optional (not excessive) nutrition and feeding management techniques. We have commonly had significant success in areas such as reducing number of services per conception as well as production of viable embryos per collection by fine-tuning the intake and timing of intake of various nutrients by the breeding animal. Programs such as these tend to be pretty intense and potentially stressful to the animal. Therefore it is important that an appropriate diet be utilized that compensates for this intensity of management and overall production stress.

Let's look at a number of these tools as well as their application to improve reproductive performance.

Body Condition Scoring

As we have discussed before in this column, Body Condition Scoring (BCS) is probably one of the most important tools a cattleman can use to manage reproductive efficiency. By insuring that the condition of the animal is appropriate at critical times in the cow's annual production cycle, we improve our chances that she will cycle normally. Research has shown repeatedly that a BCS of 5 will optimize her reproductive performance. At a BCS of 5 at the time of breeding (30 to 60 days post-calving), the cow has the necessary body stores of fat which are required for normal hormonal production for cycling activity. Additionally utilizing BCS year-round to monitor cow condition helps the producer make sure that the cow will be in the correct condition at targeted breeding times. Monitoring of BCS helps the producer determine if a given cow or the herd in general is on track, too fat or too thin at various times of the year and also helps him make the necessary decisions concerning his supplementation program. This subsequently helps the producer better manage feed and supplement cost.

Protein and Energy Intake

Protein and energy are two of the most essential nutrients in the cow's diet. Requirements for both fluctuate throughout the production year depending on what stage she may be in along with a host of other factors. Protein is required to build and maintain muscle as well as provide numerous precursors for numerous bodily processes, one of the most important being reproductive function. As we've mentioned before, intake and utilization of various nutrients, including protein and energy is prioritized in the animal. In other words, the amounts provided by the diet are utilized in a specific order from most important to least important as related to animal survival and maintenance. Unfortunately reproduction is on the bottom of this list and if the nutrients are not available, reproductive function will be one of the first to shut down since it is not vital to the animal's survival. This fact helps us illustrate why appropriate nutrient intake is so important.

Additionally, appropriate protein intake is necessary to feed the microbial population in the rumen to stimulate the digestive activity by the bugs. Research has shown that the digestibility of poor quality roughages is improved when a small amount of supplemental protein is added to the animal's diet. By improving the protein (primarily the nitrogen fraction of protein) into the rumen, the bacteria are more active, reproduce faster and therefore break down forage particles more extensively extracting greater amounts of nutrients.

Energy intake is required in the cow for the same reason we put gas in a car - to make her body run. Energy (we refer to this with terms such as TEN, Net Energy Maintenance, Net Energy Gain) drives many physiological processes and directly effects fat deposition in the animal. Therefore it is closely related to BCS. If a cow approaches calving and she is thinner than we desire (BCS lower than 4 to 5) it will be necessary to increase her energy intake to improve fat covering prior to calving and subsequent rebreeding. The fat in a cows body is used to a large degree as building blocks for reproductive hormones and are essential for normal functioning. If the fat is not there and not in the diet the synthesis (construction) of these hormones is reduced and subsequently we see effects such as delayed cycling, increased services per conception, delayed conception, etc. Improving body condition is not an overnight process either. Once we have determined that BCS is lower than normal (perhaps a 3 instead of 4 or 5) we will need to increase the energy intake by feeding more grain, whole cottonseed, etc for several weeks to get her up to the next level. In the average 1000 lb. cow, one BCS score is equal to about 100 lbs. of body weight. This is why it is important to monitor BCS year round along with monitoring energy intake so that we don't wake up one day (the middle of calving season) and find that half the herd is in a lower than desirable BCS. Keeping close tabs on BCS and energy intake will reduce this problem and greatly improve reproductive efficiency along with saving a lot of money.

Mineral Program

If you have read this column to any degree in the past you know that I am a strong proponent of a sound mineral program. Minerals are probably one of the most incorrectly supplemented nutrient groups in the cattle industry, mainly because there is so much misinformation.

Mineral supplementation typically provides sources of macro minerals (calcium, phosphorus, magnesium, potassium, sodium, sulfur and chlorine), micro or trace minerals (cobalt, copper, iron, manganese, selenium, zinc) and fat soluble vitamins (Vit A, D and E) as well as other additives. The minerals and vitamins are necessary in the body as components of various physiologic processes, in many cases as part of enzyme systems required to drive specific reactions. An example of this is phosphorus. A lot of research has been performed on the role phosphorus plays in reproductive activity. One of the main effects phosphorus has is on energy metabolism that relates directly to the activities we discussed above. Phosphorus is a component of several compounds in the reactions that transfer energy through out the tissues. If this phosphorus is not available, this energy transfer becomes less efficient therefore slowing down or inhibiting normal functioning. This therefore reduces reproductive activity in the animal. This basic understanding has led to a lot of over supplementation on phosphorus, especially in the dairy industry, but also in the beef industry as well. It goes back to the old adage that if a little is good, a lot has to be better. If phosphorus levels in the diet are adequate to maintain normal bodily functions, feeding more will not promote greater performance, it will simply be excreted in urine or feces. Therefore a lot of wasted phosphorus ends up on the ground (now considered pollution) which is another potential discussion altogether.

Other minerals such as the trace elements are also involved in the energy metabolism process as well as in the reactions required to produce the necessary reproductive hormones. As with phosphorus, if these nutrients are inadequate, it slows down the production of these various compounds and therefore slows reproductive activity. Mineral supplementation is important year round but is accentuated prior to calving and on through rebreeding. I normally recommend that cattlemen use "breeder" mineral about 30 to 45 days prior to calving and up to 90 days post calving to increase the intake of certain minerals and improve absorption. This normally incorporates an organic trace mineral source which has improved bioavailability and improved absorption. This simply helps insure that the necessary minerals and vitamins are available when the demand is the greatest.

Forage Program

The nutrient intake of any cow herd, whether purebred or commercial, is based on a sound forage program. By developing a program where grazing and haying or silage feeding provides ample amounts of high quality forage, the need for supplemental sources of protein and energy is reduced. Subsequently by utilizing soil tests and fertilization that includes the various micro nutrients, forage mineral contents can be enhanced in addition to improving overall forage production. This goes back to maintaining a good body condition score in the breeding herd and supports the factors we described earlier.

Obviously, with the effects that environmental conditions have on forage production, we cannot completely eliminate the supplementation of the various nutrients altogether and the overall quality of the soil plays a large role in forage nutrient density, we can go a long way toward providing the lion's share of nutrients through the forage program for much of the year.

Forage Testing

Along with a sound forage program comes the need to forage test. This is another management technique you've heard me emphasize over and over again, simply because it is so important. Forage testing simply tells us what nutrients are available in various standing or stored forages so we have a better idea of what nutrients are available and what we need to supplement. This keeps the nutrient availability more consistent and keeps the producers costs down. This consistency of nutrient availability strongly supports the BCS program and thereof the reproductive efficiency of the animal.

Stress Reduction

Reduction of stress in the animal, whether it be from environmental conditions, handling, transportation, etc. is vital to insuring that breeding activity operates normally. Stress is a consumer of nutrients the body otherwise would use for normal functioning. If stress levels are ever present or are higher than necessary significant amounts of required nutrients (protein, energy, minerals, vitamins) are used to alleviate these stress effects and are channeled away from processes such as production of reproductive hormones, etc. Taking steps to reduce stress (improving working facilities, adopting low stress handling techniques, provision of shade in the summer, etc.) reduces the demand stress places on the animal's body and the partitioning away of nutrients needed for normal performance.

Reproductive Performance Checklist

To put this all in a format that can be followed easily, the following checklist can be used to help cover the necessary bases to enhance breeding performance in purebred and commercial herds.

*Implement year round Body Condition Scoring (BCS) Program.

*Evaluate BCS at calving, 30 to 60 days post-calving, mid summer, late fall.

*Build a sound forage program that accents forage quality in both standing and stored forages.

*Forage test in the spring and fall.

*Supplement protein and energy based on BCS and forage tests.

*Provide a high quality, free-choice mineral (loose) year round.

*Evaluate environment and handling facilities for stressful components.

By following this list a producer can significantly enhance the performance of his breeding herd. Obviously most of these items cannot be implemented overnight but this gives the producer the building blocks on which to create a management plan that can greatly increase breeding performance and overall profitability.

(Dr. Steve Blezinger is a nutritional and management consultant with an office in Sulphur Springs, Texas. He can be reached at P. 0. Box 653 Sulphur Springs, TX, by phone at (903) 885-7992 or by e-mail at sblez@peoplescom.net  )

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