by: Stephen B. Blezinger

Part 1

The New Year always provides a great opportunity to reflect on what we did the previous year and how we will approach the one oncoming. We know there are many thing we cannot control – weather, commodity prices, etc. But there are quite a number that the producer can control.

With the New Year, one area of focus for the cow-calf producer is calf production. In many cases the goal is one to produce a live calf and two, to get the cow re-bred for the next calf crop. So let's talk about these two calf crops – the one soon to be born between now and March and the one to follow when these cows are rebred.

Over the past year we've talked a few times about managing and feeding the cow in such a way that we enhance the performance of the newly born calf as well as its health and performance throughout its life. The principles of fetal, metabolic or developmental programming (all the same thing) have been known for some time but are gaining clarity for the cattle producer only over the last five years or so. Over the last year, I've had the opportunity to write several articles on the subject as well as to give several presentations on this topic to calf growers whose livelihood depends on the production of a healthy calf. I've been surprised by the response and the interest many producers have.


First, a statement of the obvious: the function of the cow is to produce a calf. The producer's primary goal is to get every cow bred and to produce a live, healthy, productive calf once per year. Most producers fall short of this in some manner or another and this may or may not be due to direct management effects. Lots of factors affect this process. But this is the goal – breed the cow, produce a calf.

But there is substantially more to this. This is where the fetal programming (FP) concept comes into play. Many producers will tell you that they are attempting to produce calves that have a set of genetics that will result in good health and growth performance. In the heifer calves this extends out to reproductive performance as well. This can also be seen as having a multigenerational effect as we can see specific traits passing through a dam to her offspring, then to its offspring and so on. This can be as simple as a hair coloring feature or markings or it can be seen in milking ability, fertility, longevity, etc.

But other important performance features can also be recognized as genetic expression of traits such as immune response, weight gains, feed efficiency or residual feed intake. These are factors that have a direct effect on animal profitability and thus a measurable economic effect.

Consider an example of what this really means: During gestation, the cow is fed lower than required levels of one or more nutrients that has been shown to have a direct effect on the calf's immune development (let's say Copper or Zinc). After birth, the calf shows a much higher rate of sickness and thus requires more treatment either while on the cow or later during weaning and transition. This means the calf has to be handled more and that antibiotics have to be utilized to treat the illness. This results in more medicine and or vet costs. Based on earlier Texas A&M ranch to rail data, these cattle who are prone to sickness also exhibit poorer performance in the feedyard (lower average daily gains, lower feed efficiency, lower carcass performance). This means poorer economic performance to either the cow's owner or to whoever owns the calf in later in the production stages. An additional area where revenues can be reduced to the cow owner is related to weaning weights. Because of this nutritional compromise during fetal growth and development the calf may show lower than anticipated rates of gain prior to weaning. This may or may not be related to its health performance. It could be a combination of the two.

So at this point the bottom line may be that failure to provide proper levels of Copper and Zinc (at a cost of pennies) and specific fetal developmental stages while the cow is gestating may end up costing large amounts of money in health costs and reduced gain performance.

So What is Really Happening?

To grasp this we need to understand a few things concerning the developmental process from conception through birth of the calf. First some general observations:

• “The concept that lifetime health is determined in large measure by the environment experienced during development is the single most important story in human and animal health.” - Dr. Peter Nathanielsz, UT Health Science Center – San Antonio, TX.

• The process through which a stimulus or insult establishes a permanent response.

• Fetal (Developmental) programming hypothesis has several components:

   ° Exposure during a critical period in development may influence later metabolic or physiological functions in adult life.

   ° The ability to improve animal production and well-being by altering the maternal environment holds enormous challenges and great opportunities for researchers and animal industries (producers).

   ° Provides the basis for establishing and supporting the maximized expression of genetics. Of particular interest to the cattleman is phenotypic expression.

   ° Involves long term management and nutrition.

   ° May be multigenerational.

These observations have been made by a variety of researchers and provide an understanding of the importance of the concept. But all this can be summarized in one statement:

What we do with the cow, how she is fed, how she is managed, sets the stage for how the calf she is carrying performs throughout the rest of its life.

The Principles

The principles or basics of the FP concept are fairly straight forward. They include:

1.      Fetal programming can be positive or negative. This means that management and nutrition during gestation can either improve the calf's performance up to its genetic limitations or it can significantly limit the calf's ability to reach those genetic limits.

2.      Base genetics of sire and dam must be considered. Is it possible that the background of either the bull or cow could be limiting in some way due to the same effect?

3.      Initial stage is embryonic attachment to the uterine wall and development of blood supply is critical. This is the pathway by which all maternal nutrients are delivered to the embryo/fetus.

4.      What is nutrient availability to the developing fetus/embryo? What is the cow's diet during this period of time?

5.      Stress level. What types of stress is the cow under at this point? Environmental, production, health, etc.?

Items 1 and 2 are fairly straightforward so let's jump forward. To best understand stages 3-5 we need to review a timeline of what is happening from the point of conception:

Hour 0 -- Conception

Hour 1 -- Single Cell – genetic material from both sire and dam are present

Day 3-8 -- Cell mass developing – about 8 cells

Day 3-4 -- Cell mass (developing embryo) enters the cow's uterus

Day 8 -- Blastocyst Stage

Day 15-18 -- Maternal recognition of pregnancy

Day 21-22 -- Fetal Heartbeat is detectable

Day 25 -- Fetal Limb Development

Day 30-35 -- Implantation into Uterus

Day 45 -- Testicular Development in male calves

Day 50-60 -- Ovarian development in female calves

Day 90 -- Preferential vascularity of caruncles begins

Day 90-120 -- Increase in blood flow and vascular density

Day 120 -- Placental vasculature apparent

Day 281 -- Birth

Obviously there are many other things taking place at the same time as those listed. For instance, it is noted that by day 21-22 a heartbeat is detectable. This means that in the days prior the heart is developing. In the days following this it has been long known (Hubbert, 1972) that we see sequential development of Pancreas, Liver, Adrenals, Lungs, Thyroid, Spleen, Brain, Thymus and Kidney. These are all critical organs and susceptible to mal-development should an insult to the blood or nutrient flow occur at a specific stage of development.

Work in humans, where this concept started, has determined that problems in the FP process during these developmental periods have found links to incidence of obesity, cardiovascular disease and Type II diabetes. It would follow that significant metabolic diseases may also be identified in cattle.

As discussed above, a critical stage in the overall process is the embryo's entry to the uterus, subsequent attachment and establishment of functional utero-placental and fetal circulation.

Ruminants have a cotyledonary placenta.


Cotyledon: the fetal side of the placenta

Caruncle: the maternal side of the placenta

Placentome: a cotyledon and caruncle together

Research has shown that nutrient restriction of cows from d 30 to 125 of gestation resulted in reduced caruncular and cotyledonary weights from nutrient-restricted cows compared with control cows, and fetal weights from nutrient-restricted cows tended to be less compared with control cows (Zhu et al., 2007). Even after correction of the diet during day 125 to 250 of gestation, caruncular and cotyledonary weights were still reduced for nutrient-restricted cows; however, fetal weight was not different. What this means is that the cow's nutritional plane at the time of embryo attachment and the related placental development and structures directly affects how these structures develop and can thus affects the flow of blood, oxygen, nutrients, hormones and other blood chemicals from the cow to the fetus.


Obviously the maternal groundwork that is laid from conception through birth is important to the new calf and is a complex process. In the next part of this series we will continue this discussion to hopefully increase understanding of the importance of cow management and nutrition during this point in time.

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

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