Influencing certain carcass traits in her offspring
By Eric Scholljegerdes
Managing the cow/calf operation can be difficult when forage quality changes for the worse. Often times, supplement prices increase and budget constraints influence decisions that may not support optimal animal performance.
In the past, we did not think much about this as long as we had the cows in good condition, or at the very least in decent condition at calving. However, the phenomena of fetal programing or developmental programming has revealed that improper feeding of dams during pregnancy can have long-term consequences on the subsequent calf.
That said, it is not always undernutrition that is problematic, as overfeeding the dam can also have an impact on calf development and subsequent calf performance. Maternal over- and under-nutrition can change the expression of genes in the progeny such that certain traits are better or worse than a properly fed contemporary.
The subject of developmental programming generates negative connotations, but there are instances, where challenging the system can, in some cases, improve calf performance. Unfortunately, the literature is not clear on what happens to carcass characteristics when a cow’s nutrition is not properly managed during pregnancy.
Within the published scientific literature, scientists have identified the time when certain organs and tissues develop and mature during pregnancy.
Du et al. (2010) published a graphic that outlined the development of muscle tissue in the growing fetus during gestation. In this graphic, primary myogenesis begins as early as the first month of gestation up to the third, with secondary myogenesis taking place from 2.5 to 7.5 months of gestation. Likewise, the development of fat cells begins around 4 months of gestation and continue to birth.
Muscle fiber hypertrophy (increase in size of cell) begins around 5 months of gestation and continues to birth. During this time, muscle fiber number and mass, marbling, and ultimately birth weight can be impacted by nutrient restriction.
The question that remains is at being said, there can be variation in the biological responses to maternal nutrition. Such as lambs subjected to nutrient restriction during mid-gestation had greater adipose tissue and increased Type II to Type I myofiber ratio (Zhu et al., 2006). These differences have the potential to negatively impact glucose utilization (Burt et al., 2005).
All of this is to say, that there is a biological response to maternal nutrition in the developing fetus, but what is more important for the producer is whether or not these early changes translate to differences in important carcass traits.
The majority of work in this area has focused on early- to mid-gestation treatments that involve under or over feeding or type of supplement. There is a considerable lack of information regarding maternal nutritional status on subsequent progeny carcass traits and more work is warranted in this area.
Nevertheless, a very brief summary of a set of representative experiments covering a variety of maternal feeding schemes during the pre-partum period is presented in Table 1.
Prepartum undernutrition Beef cow body condition naturally fluctuates throughout the year as physiological state changes and nutrient requirements increase, in a spring calving herd often coincides with changes in grazed forage quality. Each environment places challenges on cows and those that are resilient to those changes are the ones who are able to pass on their genetics to the next generation.
The natural increases and decreases in body condition are a normal part of beef production. Yet, we are just now learning how nutrient restriction can potentially alter offspring outcomes.
Poor nutrition during gestation can alter the growth trajectory of subsequent progeny, particularly the development of muscle and adipose tissue (Du et al., 2010). However, the impact of these changes on final carcass characteristics has not been extensively investigated.
During the prepartum period, positive plane of nutrition generally had equal or greater hot carcass weight (HCW) when compared to steers born to dams that experienced moderate nutrient restriction during mid-gestation (e.g. 75 to 80% of requirements; Underwood et al., 2010; Long et al., 2012; Mohrhauser et al., 2015). Ramirez et al. (2020) reported a quadratic response when cows were fed at 50% maintenance, 75% maintenance or at maintenance during late gestation.
Steers born to cows fed at 75% of maintenance during late-gestation having the lowest HCW than either the 50% of maintenance or maintenance. Cow body condition score (BCS) at calving was 3.4, 4.3 and 5.2 (on a 9-point scale) for 50%, 75% and maintenance treatments, respectively.
The reduction in BCS would naturally lower cow maintenance requirements as the 50% treatment cows lost 75 kg of body weight as compared to 39 kg and 12 kg for 50% and maintenance treatments, respectively. This is reflected in the fact that calf weaning weight did not differ across treatments.
The 50% cows gained 24 kg from lactation to weaning and the 75% treatment cows lost 22 kg. Researchers did not report subsequent pregnancy rates, so it would be ill advised to attempt to reduce cow condition to this level as management strategy.
Modest nutrient restriction during mid- to early-gestation tended to reduce (Mohrhauser et al., 2015) or did not change (Underwood et al., 2010; Long et al., 2012) 12 rib-backfat. No changes have been observed with moderate under nutrition in loin muscle area.
Yield grade (YG) was greater for cows on a positive plane of nutrition. Cows that were restricted to 70% of maintenance and fed supplemental protein had greater YG than controls and those that were restricted to 70% of maintenance and not supplemented protein (Long et al., 2012).
This same response was observed for marbling scores. However, marbling scores were not impacted by moderate nutrient restriction in other reports (Underwood et al., 2010; Mohrhauser et al., 2015).
Underwood et al. (2010) did report improved tenderness in steers born to cows raised on improved pasture during mid-gestation compared to native pasture. This improvement in tenderness reflects that impact of proper nutrition during a time when fat cells (adipocytes) are beginning to be developed in the growing fetus).
Prepartum overnutrition Livestock producers have a natural tendency to feed greater amounts of nutrients than needed to ensure that cows have adequate BCS during gestation, when finances allow.
In many cases, when cows will become over-conditioned and reproductive success can be reduced. In the area of developmental programming, limited literature exists where livestock are overfed and carcass data are reported.
Nonetheless, little differences exist between animals that are adequately fed (maintain a BCS of 5 to 6) compared to over-fed animals (6 to 7). Excessive amounts of protein (129% of protein requirements) did increase 12 rib-backfat and YG (Wilson et al., 2016).
Whereas feeding cows that were grazing endophyte infected tall fescue/red clover pastures and supplemented with 8.61 kg of a dried distiller’s grains plus solubles plus soyhulls mixture from 103 days prepartum to calving did not change carcass characteristics of steer progeny when compared to cows offered no supplement or 2.16 kg of the supplement (Shoup et al., 2015).
Cows fed the high level of supplement did have a larger percentage of steers that graded average choice or greater compared to no supplement but did not differ when compared to the moderate amount of supplement (Shoup et al., 2015) and did not change overall marbling score. In the study reported by Shoup et al. (2015) cows achieved BCS of 6.0, 6.6 and 6.8 for no supplement, moderate supplement and high supplement, respectively.
Excessive supplementation during gestation does not appear to consistently bring about consistent improvements in steer carcass traits. This would suggest that ensuring that cows are adequately fed would be a more financially advantageous when once considers the cost of supplements.
Type of prepartum supplement Supplementation of protein is a common practice in most beef production systems. This supplemental protein improves forage utilization by rumen microbes.
Work out of Nebraska over multiple years showed either an increase in progeny carcass quality grade (Larson et al., 2009) or no differences (Stalker et al., 2006). Larson et al. (2009) speculated that the differences between the two experiments was protein source, with Larson et al. (2009) providing a supplement with greater by-pass protein.
A follow up study was conducted to investigate the impact of varying levels of by-pass protein fed during late-gestation on subsequent progeny carcass composition (Summers et al., 2015). Pregnant heifers were fed either meadow hay alone or with a protein source that contained high or low levels of by-pass protein (protein that escapes ruminal degradation).
Supplement did not impact steer HCW or loin muscle area. Twelfth rib backfat and YG were greater for low-bypass and non-supplemented controls when compared to those fed a high by-pass supplement.
Marbling scores and tenderness were greatest for non-supplemented controls and intermediate for high by-pass with low by-pass being lowest.
Placing cows in the drylot during gestation has become a common practice for many producers during drought situations. Radunz et al. (2012) placed cows during mid- to late-gestation into a drylot and fed grass hay, or a 60% corn ration or a 66.5% DDGS ration. No differences were observed for many carcass characteristics. However, the 60% corn ration had the lowest marbling score and DDGS ration was the same as hay only treatment.
Glucose clearance rate for calves born to cows consuming the 60% corn ration was lower than the other treatments, which can indicate insulin insensitivity, which may alter glucose metabolism such that intramuscular fat deposition is altered later in life. However, what is not clear, is what level of glucose coming from starch can be deleterious to fetal development or the duration and time of exposure.
A number of producers are seeing reasonable success with leaving self-fed tubs out year-round so that cows can continually consume supplement as needed with the idea that this will maintain condition and ultimately reduce the need for exorbitant supplementation during late gestation.
Palmer et al. (2022) offered cows a molasses plus urea supplement during the winter months or the same supplement offered year-long or a wheat midd cube offered year-long. Twelfth 12 rib backfat was the only carcass characteristic that differed with the winter only treatment group having greater backfat than the year-long treatments.
Winter only supplement treatment did have a greater percentage of steers grading low choice than the other treatments with no differences being observed for percent average choice. Otherwise, feeding year-round did not improve any carcass trait measured.
Conclusions Beef cows are very flexible to their environment due to the dynamic nature of the rumen. Selection pressure on cattle also naturally selects cows that are able to adapt. This modest stress on the cow system, has been shown to improve resiliency in the cow, which is demonstrated by an overall lack of influence of moderate nutrient restriction on many of the desirable carcass traits. Conversely, overfeeding is not only expensive but also does not appear to be advantageous to progeny performance.
Nutrient sources and feeding schemes did show some impact on carcass traits with high-starch diets reducing marbling scores in steer progeny, however, the experiment discussed above only investigated a diet containing 60% corn and more research needs to be conducted to look at how various feeding rates could impact carcass traits.
Feeding supplements with high levels of by-pass protein did improve some carcass traits when compared to lower by-pass protein supplements but not above that of a good-quality hay.
Feeding beef cattle year-round was not advantageous over that of feeding only during the winter (i.e. period of low forage quality). Overall, proper feeding of the cow herd during pregnancy will ensure that progeny will reach their genetic potential. However, in most cases, moderate changes in nutrition (over or under nourished) will not likely have a significant negative impact on final carcass characteristics.
References available upon request.
Author
Treatments
HCW1
12-rib backfat
Loin muscle area
YG2
Marbling score
Tenderness3
Feedlot ADG
Feedlot Feed efficiency4
Prepartum Undernutrition
Mohrhauser et al., 2015
Positive energy status: Grazing pasture, Mid-gestation
Negative energy status: Drylot limited to 80% of requirements, Mid-gestation
ND5
Tended to be greater
ND
Ramirez et al., 2020
Restricted 50% requirements, Late-gestation
Restricted 75% requirements, Late-gestation
Maintenance, Late-gestation
Equal to maintenance
Lowest
Equal to restricted 50%
Greatest
Equal to restricted 50% and 75%
Underwood et. al., 2010
Native pasture, Mid-gestation
Improved pasture, Mid-gestation
Greater
Long et al., 2012
Control, Early to mid-gestation
Restricted to 70% maintenance plus protein supplement, Early to mid-gestation
Restricted to 70% without protein supplement, Early to mid-gestation
Equal to control
Prepartum Overnutrition
Shoup et al., 2015
No supplement, Mid to late-gestation
2.16 kg DDGS6 and soyhulls, Mid to late-gestation
8.61 DDGS and soyhulls, Mid to late-gestation
Wilson et al., 2016
100% protein requirements, Late-gestation
129% protein requirements, Late-gestation
Types of prepartum supplement
Summers et al., 2015
Meadow hay, no supplement, Late-gestation
Hay plus DDGS (High Bypass protein), Late-gestation
Hay plus CGF (Low Bypass protein), Late-gestation
Greater than Low Bypass, Same as High Bypass
Same as no supplement and Low Bypass
Lower than Hay, same as High Bypass
Intermediate
Radunz et al., 2012
Drylot grass hay, Mid to late-gestation
Drylot 60% corn ration, mid to late-gestation
Drylot 66.5 DDGS ration, Mid to late-gestation
Same as DDGS
Same as Hay
Palmer et al., 2022
Winter molasses + urea
Molasses + urea year-long
Wheat midd cube year-long
Same as cube
Same as molasses year-long
1HCW: Hot carcass weight. 2YG: Yield Grade. 3Tenderness: Warner Bratzler Shear force. 4Feedlot feed efficiency: Gain:feed. 5ND: No difference statistically amongst all treatments in the experiment (P>0.05). 6DDGS: Dried distillers' grains plus solubles.
Scholljegerdes is an associate professor in the Department of Animal and Range Sciences at New Mexico State University.
