Every environment has unique opportunities to succeed and overcome production issues. These include feed costs, environmental stressors (weather, forage production and quality), health challenges unique to geographical areas and local or regional economic climate. Operational resiliency relies on our ability to address challenges.
Beef cattle nutrient requirements for various stages of production can be found in the Nutrient Requirements for Beef Cattle from the National Research Council (NRC) and National Academies of Sciences, Engineering and Medicine (NASEM). Forage sampling provides essential information for supplement formulations. On rangeland or in a nutrient-limited environment, if a producer needed to choose the most important of factors when considering supplementation, the top five would be:
- Crude protein (CP)
- Total digestible nutrients (TDN)
- Phosphorus
- Calcium
- Potassium
These five are typically going to be the first to be in a limited supply during droughts or dormant forage situations.
In most cases, producers are encouraged to work with trained feed salespersons and nutritionists. However, it is important for ranchers to have a strong understanding of heifer or cow needs to ensure all requirements are being met. Cattle raised and selected for production environments that have climatic extremes (frequent droughts, high heat, extremely cold winters) are likely going to have unique nutrient requirements. For example, beef cows raised at the New Mexico State University Corona Range and Livestock Research Center rarely see forage TDN that meets their requirements according to the NRC. Yet these cows are able to maintain a moderate body condition score of 5 and an average pregnancy rate of 90% or greater because strict selection pressure on the herd has resulted in a set of cows that flourish in this environment.
Maternal nutrition impacts female progeny fertility
Nutritional management of the dam during pregnancy can have long-lasting impacts on the fertility of her female offspring. A 2014 study led by Robert Cushman with the USDA’s Agricultural Research Service (ARS) evaluated the impact of three levels of maternal nutrition on subsequent female progeny reproductive development. Interestingly, researchers did not report any deleterious effects of reducing intake by 25% (low treatment) during the second and third trimester. Increasing energy supply to dams during the third trimester did increase their female progeny’s first-service conception rates. This report points out that limiting intake by 25% of maintenance does not necessarily result in appreciable reduction in performance.
Feeding the beef female at levels below requirements must be cautioned against, as limiting nutrient supply can negatively impact fetal development. However, there is a point where challenging a cow’s metabolic system can enhance her and her offspring’s resilience to nutrient-limited environments.
ARS’s Andrew Roberts led a study in Montana that supplemented pregnant beef cows at marginal or adequate levels of supplement during pregnancy and then subjected their female offspring to one of two treatments that were adequate or marginal. Heifers born to dams fed the marginal level of supplement and that were also subjected to ad libitum or 80% of ad libitum during their development period were able to remain in the herd at the same level as heifers born to dams fed at the adequate level. Interestingly, heifers subjected to restricted levels of feed during the development period but had been born to cows fed adequate levels during their pregnancy had a lower herd retention rate. In other words, when dams were subjected to a nutrient-limited feeding program, their female progeny performed similarly no matter the nutritional level they were subjected to as heifers. Heifers born to dams that were adequately fed were less resilient to restricted nutrients during their development period and did not remain in the herd as long.
Taken together, these studies demonstrate that placing modest nutritional stress on the cow herd can improve the resiliency of their offspring. That said, one does not need to spend an exorbitant amount of money on feed to maintain animals in a high body condition.
Protein
Protein is typically considered the first limiting nutrient on rangelands in beef cow production. In general, forage CP concentrations of 7% or greater do not provide additional benefit to the animal as measured by improvements in intake. However, when forages are fed that are below 7% CP, an improvement in forage intake is observed with supplemental protein. When forage protein is below 7%, mixtures of urea and natural protein work well to assist the ruminal bacteria in breaking down dietary fiber. However, when forage CP is low (less than 5%), a greater inclusion of true protein sources rather than urea is generally more useful in improving low-quality forage digestibility.
Supplemental protein in ruminants can be placed into two categories: ruminally degradable protein (RDP) and ruminally undegradable protein (RUP, also known as bypass protein). RDP is primarily utilized by the ruminal bacteria, whereas the RUP escapes ruminal degradation and travels to the small intestine of the animal, where it is absorbed. Ruminants have a requirement for both, and one can influence the supply of the other.
A team of researchers from Iowa State University, South Dakota State University and the University of Missouri in 2017 evaluated the impact of feeding excess CP from two sources formulated to provide low or high amounts of RUP when consuming cornstalks. In this experiment, the researchers showed that beef cows consuming corn gluten meal (high RUP) had greater ovulatory follicle growth. Commercial protein supplements that include dried distillers grains plus solubles, corn gluten meal or animal byproducts (feather meal, fish meal, porcine blood meal) will have a greater proportion of RUP than something like soybean meal or cottonseed meal. That said, if the ability to custom formulate supplements with more bypass protein is limited, producers are encouraged to procure individual commodities to achieve their nutritional goals.
Development of resiliency in individual beef herds is key to maintaining low input costs. This is not to say animals must be improperly managed; rather, optimizing inputs and outputs is important for the long-term sustainability of any beef production operation. Cow herds that are nutritionally challenged will develop a resilient animal with greater stayability for not only her but her offspring when compared to those that are pampered.
References omitted but are available upon request by sending an email to the editor.
