IS YOUR HERD MEETING ITS GENETIC POTENTIAL?

by: Stephen B. Blezinger
PhD, PAS

Purebred breeders regularly talk about their genetics. They spend large amounts of time and money in the selection of animals that have the right “genetics” to meet what they have set as their production goals. This may mean in a specific look (phenotype) that the animal has (color, horned or polled, muscling, skeletal structure, body size, etc.). Other parameters are performance measurements and can include calving ease, birth weights, milking ability, average daily gains under different feeding regiments, feed efficiency, reproductive efficiency and so on.

Producers and industry professionals discuss these issues all the time and they include in this discussion the animal's genetic potential and feeding and managing that animal to meet this potential. But what does this mean, exactly? How does a producer know exactly what that genetic potential is? What are things that may affect this potential outside of the basic set of genes a given animal received from its sire an dam? The questions are endless and frankly many do not have good answers.

One thing research over recent years HAS determined though is that establishing and meeting genetic potential starts very early in an animal's life. It is currently theorized that this could begin at or even before conception. A term that has become relatively common is “fetal programming” (FP). Described simply, FP is the concept that how we feed and manage the cow may very well affect the calf she is carrying from the time of conception through its entire life. Essentially what the concept means is how we feed and manage the pregnant cow will “program” the calf from birth on.

Producers, nutritionists, vets and academics have long known that the nutrition and management of a pregnant female (the concept was actually first recognized in humans) has direct effects on the health and growth of the fetus and the baby. Some of the earliest specific work by Barker and his team at Southampton University in England showed that mothers who were malnourished during the first half of their pregnancy had children that had an increased incidence of health problems as adults which included diabetes, obesity and cardiovascular disease.

For the cattle producer this is very tangible. If we mismanage the nutrition program or fail to take steps to keep stress in check during pregnancy there will be affects to the unborn calf. Initially the calf may be born very weak or even dead. The calf born as a result of that pregnancy may not gain weight to its potential while still on the cow or later in the feedyard. A heifer calf, as it matures to a producing cow, may not be as reproductively sound as she should be because some genetic groundwork was not laid properly. In a nutshell the concept means that the producer is managing the cow (and the bull) as best possible from before conception through calving to insure the calf's genetic potential is at its best. It is now believed that this very early nutrition and management may dictate what the calf's genetic potential really is.

This sounds like it is only a long term prospect and as such may be difficult to see the results. However, how we manage the cow carrying the fetus from the time of conception can have dramatic effects on growth and development of the calf while in the uterus and then after birth. In addition to the performance issues such as those listed previously we can also see negative effects on pregnancy rates and initial calving date in females. Fetal programming may also impact carcass quality in the form of muscling and the amount of marbling. So when we look at ribeye area ultrasound scans, what we see in an animal at 12 months of age may have been affected when it was an embryo only a few weeks old.

In general, most producers recognize how important it is to provide adequate nutrition to the cow during the third trimester of pregnancy. Most of the unborn calf's growth occurs during this latter part of gestation, with about 75 percent of growth occurring during the last two months. The cow's nutritional status during the later months of pregnancy also influences how quickly her reproductive system recovers after calving and resumes normal estrous activity. It has been proven time and time again that it is hard to get a cow ready to breed if she is in poor condition at the time of calving. Consequently, much research have concentrated on the cow's dietary needs during late pregnancy.

So in many cases, historically, the first half of gestation has seemed less important — once she's bred we can sit back and relax. This seems especially true when you consider that the fetus has limited nutrient requirements for growth and development at this stage. However, growing evidence suggests there is a lot going on at the very beginning, at and from conception, as well as later in the pregnancy — things that can have significant effects on producer profitability — as a result of fetal or developmental programming. This very early stage of pregnancy is the focus for this discussion. The key concept we will focus on here is that the cow must be managed prior to breeding, at breeding and in the early periods after conception in such a way that the developing embryo and fetus will receive everything it needs to insure its productivity through its life.

Some things to Understand

There are two primary keys for the producer to understanding the initial fetal programming process in the animal. First, there has to be recognition of what is happening at conception and the period following. This includes what is going on with the genetic material. Secondly, once conception takes place, there has to be a connection made between the developing embryo and the cow.

To begin, the blueprint for life is deoxyribonucleic acid or DNA. This material is essentially the instruction manual for everything happening in the animal physiologically from the start – how cells and tissues divide, multiply and accumulate, how the fetus and later the animal grows and develops, establishment of the immune system, the ability to grow at a certain rate, and so on. The DNA for a given individual is established at the point of conception and is a combination of that DNA delivered from the sire in the sperm and from the dam in the ova. This is the true mechanics of the selections breeders make when mating specific bulls and cows. Many producers carefully consider EPD's which provide an indicator of what an animal's genetic potential is for traits like birth weight, weaning weight, milk production and so on. These EPD values have a physiological base in the genetic material that is the platform for this performance. Providing the proper nutritional and management support for the dam is critical to optimizing the expression of the genetic investment.

The DNA begins its role almost immediately after conception, instructing the fertilized egg cell to begin dividing and transitioning into an embryo and then a fetus. The DNA blueprint then goes on to set the protocol for how the tissues and various physiological systems in the growing body develop. This is a key period of time. During these very early stages (only a few days after conception) the new embryo is undergoing exponential growth, some of the most rapid cellular division in its entire life. If conditions are not optimal, opportunity exists for problems or errors to occur in the genetic codes or instructions. This is where a material known as RNA or Ribonucleic Acid comes into the picture. While DNA is the instruction manual that resides in the nucleus of the cells, RNA leaves the nucleus and the cells and is essentially the individual pages of the instruction manual. It provides specific instructions on how the countless actions and reactions in the cells, tissues and entire body are to occur.

This is where a significant opportunity for problems to develop. While DNA is very stable, has methods of error detection and the means to correct these errors, RNA does not have these same capabilities. Both DNA and RNA are capable of making copies of themselves. DNA copies are generally very good. With RNA this is not always the case as it can make flawed copies of itself and does not really have a way to repair these flaws. Additionally, RNA replicates itself about 10 times faster than DNA so appropriate nutritional building blocks must be in place constantly to support this copying process.

It has been well known for many years that many nutrients are critical to this entire process. For most producers the nutrients given the most attention are protein and energy. Adequate provision of both these nutrients is important for production of the genetic materials. Remember that both DNA and RNA are essentially proteins. In order for proteins to be synthesized, basic building blocks (dietary proteins and amino acids) must be present to create the structure. Energy is required to facilitate the synthesizing reactions. The availability of protein has very practical results. Research studies have shown that calves born to cows that are fed a diet lacking in protein in the early stages of pregnancy, may be more susceptible to respiratory disease later in life. This is thought to be caused by poor lung development during gestation. This could be related to a lack of the basic building materials for tissue synthesis or for proper RNA replication which instructs the body HOW to build these tissues. Further research has examined the incidence of bovine respiratory disease (BRD) in feedlot cattle. Fifteen to 45 percent of cattle have been affected by BRD and one to five percent of cattle placed in feedlots die from this disease. Anything we can do to reduce BRD and respiratory problems will be huge for the industry in the form of additional profits. There is likelihood that FP through proper nutrition can help reduce the incidence of BRD in these cattle. This may also become increasingly important as the industry's access to antibiotics becomes more restricted.

But protein and energy are not the only nutrients requiring attention. We have known for years that minerals have long played a role in embryo and fetal development. For example, Wilberg and Neuman reported in 1957 that there was an association between DNA and the trace mineral Manganese (Mn). Based on their work it was suggested that Mn has a functional relationship in the transmission of genetic information. De Carvalho and co-workers (2010) reported that Mn seems intimately involved in the synthesis of protein as well as DNA and RNA. Their results suggested that epiphiseal growth plate cartilage was affected during the early stages of embryo development due to Mn deficiency in the diet of the dam. This went on to result in malformations of the calf's reproductive systems and birth of calves with congenital defects in the skeletal tissues. So from this we can infer that if Mn is in short supply in the cow, this deficiency will be present in the reproductive tissues and may be in short supply during the initial phases of cellular division when the transmission of this genetic information is critical.

Additionally, to illustrate the importance of certain nutrients at very early developmental stages, Lequarre and co-workers (2001) reported the presence of Zinc (Zn), Copper (Cu) and Mn dependent enzymes in bovine embryos prior to placental implantation. These enzymes include superoxide dismutase (SOD) which is a critical anti-oxidant and is found in virtually every cell in the body. This study showed that this enzyme was present from the very early stages of life. The synthesis and effect of this enzyme requires the presence of Cu, Zn and Mn.

A second key to FP is the development of the placenta and the vascular system the supplies the blood flow in the fetus. From conception to Day 90 the fetus is developing vital organs along with the development of the placenta so cow nutrition is important at this time. The critical time period for attachment of the placenta to the uterine wall and the subsequent vascular system for the fetus begins at 90 days after conception. By day 120, blood (and nutrient) flow to the fetus has increased greatly. During this critical span of days, (90 to 120 days) if the cow is malnourished, the development of the vascular system between the uterus and the fetus affects the ability of the fetus to get nutrients and oxygen from the mother. If this nutrient delivery system is inadequately developed it will negatively impacting the growth and development of the fetus. Vonnahme (2007).

Conclusions - So what does this mean to the Purebred or Commercial Cow/Calf Producer?

Most producers will tell you that they focus strongly on management and nutrition during the period prior to calving and leading up to breeding. But, in many cases, this focus is driven by a desire to get the cow rebred after calving. What this concept emphasizes is that not only do we need to be attentive to facilitating the next pregnancy but also that what we are feeding and how we are managing the cow at this point in time has significant and long term implications on the overall life and productivity of the new calf. In a time when production efficiency is so critical, the producer cannot leave anything on the table.

So while it is important to pay attention to year-round nutrition and total management special attention should be given to that period starting 45 to 60 days prior to calving on through the first 90 days after conception. First, because we are equipping the cow to deliver the optimum genetic material (DNA). Also remember, it takes approximately 60 days for sperm cells to develop so there needs to be a focus on the bulls prior to the breeding period as well to insure their genetic integrity as well. Second, at conception we want that initial cellular multiplication, growth and development to be as sound as possible and for that embryo to become implanted and the vascular attachment to develop optimally. Finally, the nutrient supply from the cow to the developing fetus must be complete with nothing compromised. Again, all of this attention being given to insure maximum genetic expression and performance throughout the unborn calf's life.

This is not just a matter of taking the shotgun approach to your nutrition program. All facets need to be carefully planned and designed for your operation and your herd. Many producers already have a good nutrition and management program. This is where the fine tuning can really pay benefits. This is also an opportunity to inject added value into your marketing program. There is a distinct advantage to not only promoting your genetics but also the fact that your program addresses the genetic integrity of every animal from the point of conception.

Dr. Steve Blezinger is a management and nutritional consultant with an office in Sulphur Springs, TX. He can be reached at sblez@verizon.net or at (903) 352-3475. For more information please visit us on at www.facebook/reveillelivestockconcepts.

References:

De Carvalho, P. R., M. C. G Pita, J. E. Loureiro, H. R. Tanaka, J. C. S. Ribeiro, and A. A. Philips. 2010. Manganese deficiency in bovines: Connection between manganese metalloenzyme dependent in gestation and congenital defects in newborn calves. Pakistan J. Nutr., 9 (5) 488-503.

Lequarre, A. S., J. M Feugang, O. Malhomme, I. Donnay, A. Massip, F. Dessy and A. Van Langendonckt. 2001. Expression of Cu/Zn and Mn superoxide dismutases during bovine embryo development – influence of in vitro culture. Mol Rep Dev. 58 45-53.

Radunz, A.E., Developmental Programming in Beef Cattle and Potential Utilization of This New Science in the Beef Herd., 2011 Minnesota Beef Cow/Calf Days, Publication BP-1103.

Vonnahme, K.A., Nutrition During Gestation and Fetal Programming., Range Beef Cow Symposium XX, December 11-13, 2007, Fort Collins, Colorado.

Wilberg, J. S and W. F. Neuman. 1957. The binding of bivalent metals by deoxyribonucleic and ribonucleic acids. Arch. Biochem. Biophys. 72:66-83.







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