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In Part 1 of this series we began an in-depth look at the specifics for the origination and development of a productive, healthy calf. We touched the surface of the fetal programming concept and began to work on the understanding of the many particulars that can affect the calf from the point of conception on through birth and into its life outside of the uterus.

From a logistical perspective there are two primary issues that have to be recognized and addressed. One is that of embryonic/fetal attachment to the cow. As we discussed in Part 1, this attachement via the placenta is the �pipeline� by which all nutrients are delivered to the developing calf. This attachment and tissue development is complex and requires a variety of nutrients and reactions to be readily available in the appropriate quantities and timing.

The second part of this picture is access to the actual nutrients themselves. It should be emphasized that this is not just a matter of having ENOUGH of all necessary and critical nutrients but also not having TOO MUCH of these as well. The following discussion will delve into the nutrition part of this issue. A side note � you will find a variety of references in this article that will not be listed at the end in order to save space. If you have an interest, please send a note to the email at the end of this article and a complete reference list will be sent to you.

Nutrition is a Critical Key

In livestock production settings, lack of proper nutrition can often occur during gestation, particularly during the first two trimesters, even though we know that the bulk of fetal growth occurs in the third trimester. This results from either low feed reserves and/or management practices that result in cows losing weight during late fall and early winter (Sletmoen-Olsen et al., 2000a,b). However, data indicate that health and growth of offspring born from undernourished mothers are diminished (Godfrey and Barker, 2000; Vonnahme et al., 2003). While variations in the duration and severity of maternal under-nutrition do not always result in a reduced birth weight, physiologic alterations such as glucose intolerance, skewed growth patterns and alterations in carcass characteristics have been reported. It becomes obvious that birth weight alone may not be the best predictor for calf survival and productivity.

For the cattle producer this is very tangible. For example, if the nutrition program is mismanaged or there is failure to take the appropriate steps to minimize stress during pregnancy there will be affects on the unborn calf. Negative nutrient environment can result in possible fetal programming responses due to several factors (Wu et al., 2006; Reynolds et al., 2010). These may include:

1) Breeding of young dams who compete for nutrients with the rapidly growing fetal systems.

2) Increased incidences of multiple fetuses or large litters.

3) Selection for increased milk production, which competes for nutrients with increased energy demand from fetal and placental growth.

4) Breeding of livestock during high environmental temperatures and pregnancy occurring during periods of poor pasture conditions.

These and other studies have reported instances of compromised maternal nutrition during gestation which resulted in increased neonatal mortality, intestinal and respiratory dysfunction, metabolic disorders, decreased postnatal growth rates, and reduced meat quality (Wu et al., 2006). Proper management of cow nutrition during gestation can improve progeny performance and health, perhaps through its entire life.

One of the most significant signs of maternal undernutrition is obvious. 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 genetic potential while still on the cow or later as it begins producing in the milking string or placed in the feedyard. This effect has been documented as reflected in Tables 1 and 2. In 2012, Underwood and co-workers reported increased body weight (BW) gains, final BW, and hot carcass weight (HCW) in steers from cows grazing improved pasture from day 120 to 180 of gestation when compared to progeny from cows grazing native range during that same time. Steers from cows grazing improved pasture had increased back fat and tended to have improved marbling scores compared to steers from cows grazing native range. Similarly, a study was pursued to determine the effect a dietary energy source had on progeny calf performance. Radunz (2009) offered cows three different diets during gestation beginning on approximately day 209: hay (fiber), corn (starch), or distillers grains with solubles (fiber plus fat). Corn and distillers grains diets were limit fed to ensure consistent energy intake among treatments. Results indicated reduced birth weights for calves from dams fed grass hay when compared to calves from the other two groups, with an increase (P≤0.05) in calf body weight reported through weaning when comparing calves from corn fed dams to hay fed dams. Feedlot performance among treatments was not different; however, calves from hay fed cows required 8 and 10 more days on feed to reach a similar fat thickness when compared to calves from distillers and corn fed dams, respectively.

Similar effects can be seen in the effects of maternal prenatal nutritional support on resulting heifer calves as reported in Table 2. Martin et al. (2007) conducted a study with cows grazing dormant Sandhills forages during the late gestation period. One group received a 42 percent CP (DM basis) cube offered three times weekly at the equivalent of 1.0 lb/day while another group received no supplement. Calf birth weight between heifer progeny from supplemented and nonsupplemented dams was not different; however, heifer progeny from supplemented cows had increased adjusted 205 day weaning weights, prebreeding body weight (BW), BW at pregnancy diagnosis, and improved pregnancy rates compared to heifers from nonsupplemented dams. Furthermore, Funston et al. (2010b), using the same cow herd, offered a distillers based supplement (28 percent CP, DM basis) three times weekly at the equivalent of 1.0 lb/day, or no supplement during late gestation as cows grazed either dormant Sandhills range or corn crop residue. Calf weaning BW was greater (P = 0.04) for heifers from protein supplemented dams. The study went on to show a decreased age at puberty for heifers from protein supplemented cows and a trend (P = 0.13) for higher pregnancy rates when compared to heifers from nonsupplemented dams, possibly related to decreased age at puberty.

Other implications in female cattle may also be noted. As the heifer matures to a producing cow, she 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 needs to be managing the cow as best possible from before conception through calving. This helps insure the calf's genetic potential. Indeed this very early nutrition and management may dictate what the calf's genetic potential actually is. This concept is truly managing for the long term.

However, it's not just for the long term. 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 immediately 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 only an embryo only a few weeks old as suggested by the previous data. Additional evidence exists that this early fetal development directly affects the establishment and development of the immune system and can dictate the long term function of the immune responses as well as autoimmune conditions.

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 (Robinson, et al, 1977, Vonnahme, 2007). 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 and producers' efforts have concentrated on the cow's dietary needs during late pregnancy.

In many cases, historically, the first half of gestation has seemed less important. This seems especially true considering 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. The key concepts to 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 the necessary nutrients in these early developmental stages to insure its productivity through its life. A correlation would be the construction of a house on a sound foundation.

Conclusions

As has been stated, it is obvious that the maternal groundwork that is laid from conception through birth is important to the new calf and is a complex process. Nutrition is critical to this process but other issues come into play as well including basic management and stress effects. These issues should cause the serious cattle producer to take a hard look at his preconception through calving program from the standpoint of accuracy of nutrient provision, adequate management and efforts to reduce any stress effect feasible.

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

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