by: Stephen B. Blezinger
Ph.D., PAS

Part 2

In Part 1 of this series we began discussing the effects that the nutrition of the pregnant cow pre-calving can have direct effects on how well the resulting calf performs throughout its life. This is a concept (fetal programming) that has been discussed at length and is in fact well accepted. However, researchers and producers alike have only, in recent years, begun to understand how this dynamic can actually be manipulated to the benefit of not only the calf but as a means of enhancing performance and profitability on the operation.

As discussed previously improving the nutrition of the cow at and post conception and through the entire gestational period has been shown to enhance a number of performance parameters including:

1) Calf survival (lower dystocia rates)

2) Growth (greater weaning weights)

3) Carcass quality

4) Health (lower rates of sickess and deathloss prior to weaning).

5) Quality of colostrum produced by the cow during the hours immediately after birth.

6) Heifer calf reproductive performance

A focus on strategic development of the cow's nutritional status produces more than theoretical results. There are very tangible, profitable opportunities to be recognized.

Results the Producer can Measure.

A very basic result of improved nutrition for the pregnant cow is an overall increase in live calves born. In today's market, the loss of even one calf has significant implications on operation revenues, even larger operations. Research over the years have illustrated the effects maternal nutrition has on calf survivability and sickness at and after birth. Corah and co-workers (1975), found increased morbidity and mortality rates in calves born to first calf heifers receiving 65 percent (limited) of their dietary energy requirement over the last 90 days of gestation compared to calves from the same type of heifers receiving 100 percent of their energy requirement. In other words, the limit or restricted fed heifers gave birth to calves that experienced greater post calving death loss and sickness. Another factor contributing to increased morbidity and mortality is decreased birth weight. Calves born to nutrient restricted cows were 4.5 lbs. lighter at birth compared to calves from dams receiving adequate nutrition. These results have been repeated in numerous studies since.

These can be interpreted very plainly. Pregnant heifers and cows provided nutrient levels to meet their needs have been shown to a) produce a higher percentage of live calves and b) to produce calves that are less prone to sickness. Combined, these results can increase the total pounds of beef produced from a given cow herd. While the exact amounts will vary based on any number of other factors, producing more calves that are less likely to become sick is obviously beneficial in terms of more animal units to start with, less opportunity for later death loss, less growth hesitation due to effects of illness, reduced vet, medicine and labor expenses.

Effects on Heifer Calves - Reproduction

The effects of maternal nutrition can be noted in numerous studies and even goes beyond the initial generation. Martin et al. (2007) conducted a study with cows grazing dormant Sandhills (Nebraska) range pastures during late gestation. 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 weights were not different between the two groups but heifer calves born to supplemented cows had increased adjusted 205 day weaning weights, pre-breeding body weights, body weights at pregnancy diagnosis and improved pregnancy rates compared to heifers from non-supplemented dams.

In a 2010 study, Funston and his co-workers, using the same cow herd as noted above, offered a distillers based supplement (28 percent CP, dry matter basis) 3 times weekly at the equivalent of 1.0 lb/day, or no supplement during late gestation. These herds were maintained on either dormant Sandhills range pastures or corn crop residue. Calf weaning body weight was statistically greater for heifers from protein supplemented dams. A second study with these groups of animals also reported a decreased age at puberty for heifers from protein supplemented cows and a tendency for higher pregnancy rates when compared to heifers from non-supplemented dams. This may have been related to the decreased age at puberty. Similarly, Corah et al. (1975) reported heifers born to first calf heifers fed 100 percent of their dietary energy requirement during the last 90 days of gestation were began cycling 19 days earlier than heifers born to first calf heifers fed an energy restricted diet.

These studies illustrate that maternal nutrition can have a direct effect on the growth and reproductive performance of heifer calves born to cows managed and fed properly.

Effects on Steers Headed for the Feedlot

As discussed in Part 1, the goal of producing meat animals is to harvest skeletal muscle. The fetal stage is crucial for skeletal muscle development because there is no net increase in muscle fiber numbers after birth (Stickland, 1978; Zhu et al., 2004). Therefore, a decrease in the number of muscle fibers because of inadequate dam nutrition permanently reduces muscle mass and the animal's ability to accumulate muscle volume. Hence, reduced calf weights at varying stages and overall muscle expression.

Secondly, marbling (i.e., intramuscular fat) is crucial for meat palatability, and plays a role in tenderness. The fetal stage is a major period for generation of intramuscular fat cells which provide the sites for intramuscular fat accumulation or marbling formation during finishing. Thus, fetal programming also affects marbling in offspring cattle.

Studies have reported improved muscle development in steers from adequately fed cows when compared to steer calves from nutrient restricted dams. Underwood and co-workers (2010) reported increased body weight gains, final body weight, and hot carcass weight in steers from cows grazing improved pasture from day 120 to 180 of gestation when compared to herd mates 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. Note that these studies did not evaluate the nutritional differences that utilized a supplement. These compare pasture systems and the ability to deliver critical nutrients.

In a turn to maternal nutrition research, another study was conducted to determine the effect dietary energy source had on calf performance. Radunz (2009) fed cows one of three diets during gestation beginning on approximately day 209 which included hay (fiber), corn (starch), or distillers grains with solubles (DDGS, fiber plus fat). Corn and distillers grains diets were limit fed to ensure the same energy intake across treatments. Results indicated reduced birth weights for calves from cows fed only grass hay when compared to calves from the other two groups with a statistical increase in calf body weight reported through weaning when comparing calves from corn-fed cows to hay fed dams. After weaning, feedlot performance of calves among treatments was not different; however, calves from hay fed dams 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, thus an extended time to reach the same finished point.

Protein supplementation during late gestation increased weaning body weight, average daily gain to weaning, and proportion of calves weaned when comparing calves from supplemented to non-supplemented dams grazing dormant winter range pastures in multiple studies. Larson et al. (2009) reported increased average daily gain, hot carcass weight, and marbling scores in steers from supplemented dams. A greater proportion of steers from supplemented dams graded USDA Choice and USDA Choice or greater when compared to steers from non-supplemented dams. Non-supplemented cows in the study may have been under greater nutritional stress than those reported in other studies, as average weaning date was approximately one month later and possibly had greater impact on fetal development.

Influence of Maternal Nutrition on Long Term Health

Another facet of this discussion notes that studies have linked maternal nutrition during gestation to calf health. As mentioned previously, Corah et al. in the 1975 study showed increased morbidity and mortality rates in calves born to first calf heifers receiving restricted dietary energy requirement over the last 90 days of gestation. In later studies on calves in the feedlot Mulliniks et al. (2008) and Larson et al. (2009) indicated reduced proportions of steers treated for health issues in the feedlot from cows supplemented with protein compared to calves from non-supplemented cows. Stalker et al. (2006) reported increased proportions of live calves weaned from cows offered supplement during late gestation. These results have been a bit variable. Snowder et al. (2006) reported incidence of disease is more likely after 5 days on feed and remains high through the first 80 days in the feedlot. Furthermore, steers were more likely to become sick compared to heifers in the feedlot. Post-weaning stress is a factor influencing calf health. As mentioned earlier, Funston et al. (2010b) did not report any difference in heifer calf health between groups of cows fed either restricted or unrestricted diets. These heifers, unlike their steer cohorts, remained at the ranch post-weaning and were maintained on a forage based diet, likely reducing the amount of stress placed on the animal when compared to their steer cohorts who were transported to the feedlot two weeks post-weaning and adapted to a concentrate based diet. So obviously, other factors do come into play. However, evidence is substantial that maternal nutrition plays a significant role in the health of calves later in life. As noted in previous articles the basis of the immune system is established during early stages of fetal development.

At the end of the day, the producer wants to sell more pounds of beef when the calf leaves his ownership. For the cow/calf producer that is selling calves at weaning. If the producer is retaining ownership and selling these calves out of the feedyard, the quality of this beef (carcass, marbling, etc.) is also a concern as this directly affects the value per pound of product. Regardless of the circumstances, proper nutritional management of the cow herd during gestation has significant and long term effects on the number of calves produced and well as the health and performance over their lifetime.

Copyright 2015 Dr. Stephen B. Blezinger. Dr. Steve Blezinger is a nutritional and management consultant with an office in Sulphur Springs, Texas. He can be reached by e-mail at [email protected] For more information please visit Facebook at Revielle Livestock Concepts.

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