Proper nutrition is crucial for health, productivity and profitability for any livestock enterprise. Nutrients are feed components whose requirements for livestock vary depending on factors such as age, weight, growth rate, reproductive status and environmental conditions. Cattle are ruminant animals that have a four-compartment stomach in which microbial fermentation allows for efficient use of nutrients stored even in the most fibrous feeds such as pasture, hay and baleage (haylage). This section outlines the nutrients and their roles in beef cattle nutrition, aiding in the evaluation of feed analyses and decision-making by Louisiana beef ranchers.
1. Water
Requirements: Water consumption varies by temperature, diet and physiological state. Louisiana’s elevated temperature and humidity significantly increase water intake (refer to LSU AgCenter Pub. 3933 for more details). Cattle consume around 1.5 gallons of water per 100 pounds of body weight daily. Overall water intake by beef cattle can range from 4 gallons to 8 gallons.
Sources and Quality: Water quality can influence consumption. Several contaminants can be a risk to animal health and nutrition. Those contaminants can be determined in analyses that include:
Water deficiency can limit productivity and even lead to fatality quicker than the deficiency of any other nutrient (carbohydrates, protein, fats, minerals or vitamins). Plentiful availability of water of adequate quality is key for any beef operation.
2. Energy
Importance: Energy refers to the capacity of nutrients (like carbohydrates, lipids and proteins) to fuel physiological processes necessary for the body’s basic functions (maintenance), growth, reproduction and lactation. Because the bulk of a diet is used as an energy source by the body, energy tends to be a main driver of feed intake.
Requirements: Energy needs depend on the stage of production. Nursing calves and lactating cattle have higher energy needs. Energy is estimated more often in terms of total digestible nutrients (TDN), given in % of the dry matter, but can also be expressed as net energy (NE), given in megacalories per pound or Mcal/lb.
Sources and Quality: Technically, energy is not a nutrient, but it is derived from nutrients, namely carbohydrates and fats. Proteins can also be used as energy sources but are expensive and less efficiently used for energy by cattle. Energy sources make up the bulk of the diet, given the amount of nutrients needed to fulfill an animal’s energy requirements.
Fiber content (NDF and ADF) tend to increase with maturity (rapidly after seeding) in any forage, and are, on average, higher in Louisiana warm-season forages (for example bermudagrass and bahiagrass) when compared with temperate forages (for example, annual ryegrass) at similar maturity.
3. Proteins
Importance: Proteins make up much of the body’s molecules. The structure of proteins is composed of 20 amino acids (AA) in varying proportions, AA content and position in the structure of the protein. An AA presence in a specific position in the polymer can dictate the protein’s structure and function. Proteins functions in the body include transportation, cell and tissue structures, muscle contraction and gene expression, among many others. Proteins are essential for muscle development, milk production and overall body growth.
Requirements: From a nutritional standpoint, the similarity between the animal’s AA requirements and the composition of AA that are absorbed from the small intestine is referred to as protein quality. In the case of cattle, rumen fermentation plays a key role in protein quality and utilization. A portion of feed protein and nonprotein nitrogen (NPN such as urea, biuret, ammonia) are fermented by rumen microbes into peptides (short polymers of amino acids), amino acids and ammonia. Those components can be converted into microbial proteins if sufficient energy is also made available in the rumen at a timely rate. Microbial protein synthesis can vary based on factors such as the quality of the diet, rumen conditions and the type of feedstuffs used. The microbial protein produced by rumen microbes has great biological value and typically contains a balanced profile of amino acids, including most of the essential amino acids required by ruminants. The fraction of the protein in feeds that undergoes microbial digestion is called rumen degradable protein (RDP). Rumen microbes also have nutrient requirements to support microbial population. Rumen microbes need a minimum dietary protein of 7% crude protein in the dry matter to be able to digest dietary fiber properly. In most dietary conditions, 60% to 80% of the proteins that reaches the small intestine in ruminants are microbial proteins.
The remaining portion of the dietary protein that is not digested in the rumen is deemed rumen undegradable protein (RUP). In diets based on high-quality forages, microbial protein can supply the needs of most beef cattle categories and rely minimally on RUP. The RUP fraction may be digested in the small intestine and utilized by the ruminant, and its quality (amino acid composition) plays a significant role. Overall, protein needs vary with age and production stage. Young calves in initial stages of growth and high-producing dairy cows need higher protein levels. For those animal categories, special attention to RUP is warranted.
Sources and Quality: Protein analysis is reported as crude protein (% CP). Forages, grains, oilseed meals (such as soybean meal, cottonseed meal, dry distillers’ grains – DDGS) and protein supplements (protein tubs). Most protein in forages are rumen degradable, therefore high-quality forages can supply plentiful protein for growing and mature beef cattle. Rumen available energy also plays a role in the synthesis of microbial proteins. Therefore, it is important to feed protein supplements when using poor-quality forages (high NDF and ADF) with low energy content and low protein content. Lick tubes, range cubes, protein blocks and liquid supplements often contain urea (or other sources of NPN) and molasses (energy source). It is important to ascertain that enough energy is available and NPN toxicity is avoided. Sufficient sulfur (S) is also warranted when supplementing NPN to ensure that rumen microbes can produce some specific sulfur-containing AA’s (methionine and cysteine), optimizing microbial protein production.
4. Minerals
Importance: Minerals are required for many essential roles in beef cattle supporting overall health, optimum growth and reproduction. Some of the most crucial functions include:
Requirements: Minerals are required in minute amounts compared with water, energy and protein. Based on the amounts required by the animals, minerals are often classified as macrominerals or microminerals (or trace minerals). Macrominerals include Ca, P, K, Na, Cl, Mg and S, while microminerals most routinely supplemented include Fe, Zn, Cu, Mn, I and Se. Mineral deficiency can be associated with specific and with unspecific symptoms in cattle. Ca deficiency can lead to bone malformation in calves (rickets) and mature cattle (osteomalacia), while P deficiency may decrease calf weight gain. Louisiana warm summers increase losses of Na and K through sweat and decrease feed intake, thus supplementation may need to be adjusted depending on the season. The macrominerals most deficient in forages in Louisiana are Na and Mg, and the trace minerals are Cu and Zn, and in some regions, Se.
Sources and Quality: Minerals may be required depending on animals, plants, soils and environment and their interactions. Those include animal category and level of production, mineral status in the body, diet content and bioavailability, mineral and vitamin interactions, forage species, and soil fertility, among several others. Bioavailability refers to the fraction of a mineral that may be utilized by the animal. Mineral bioavailability varies widely, particularly in forages. Mineral bioavailability may be enhanced or may require the presence of certain vitamins (for example, iron and vitamin C). Similarly, certain minerals may enhance the absorption of other minerals, but more often, excess supplementation of some minerals may decrease the utilization of others. For instance, P, Zn, Mn and Cu can decrease Fe absorption while higher dietary Zn may enhance Cu absorption. It is also important to note that overfeeding minerals is not only wasteful and a potential environmental risk, but it can also be toxic to the animals. Minerals may be found associated with other feed components such as proteins, carbohydrates and vitamins. Microminerals associated with those organic compounds tend to be slightly better utilized by cattle than when inorganic supplements are offered. Mineral concentration in feeds (forages and grains) vary widely and mineral content should be determined by laboratory analyses whenever feasible. Mineral analyses have to be requested for specific elements, but some laboratories offer packages that include multiple mineral elements for convenience. Contents of macrominerals are usually expressed in percentage (%) and microminerals in parts per million (ppm). Some commercial supplements include organic mineral supplements, but their cost-effectiveness must be carefully evaluated. The commercial minerals are often balanced for regional deficiencies, but depending on the situation may need to be fine-tuned for individual farm conditions.
5. Vitamins
Importance: Vitamins are nutrients required in small quantities that have essential roles in beef cattle. Those nutrients can be divided into fat-soluble vitamins (A, D, E and K), and water-soluble vitamins (B-complex vitamins including thiamin, B1; riboflavin, B2; niacin, B3; pantothenic acid, B5; pyridoxine, B6; biotin, B7; folic acid, B9; and vitamin B12; as well as vitamin C). Vitamin deficiencies are associated with specific syndromes, such as pellagra in pigs (niacin deficiency), rickets in calves and osteomalacia in mature cattle (vitamin D deficiency), and nutritional muscular dystrophy in lambs (vitamin E deficiency). The main functions of the vitamins most commonly supplemented include:
Requirements: Water-soluble vitamins and vitamin K are synthesized in the rumen and intestine of cattle and rarely need to be supplemented for beef cattle. Vitamin D is also synthesized in the skin exposed to UV-light from the sun, thus grazing cattle in Louisiana are rarely deficient in vitamin D. Vitamin A deficiency can result in vision loss (particularly in the dark/night), poor conception rates and abortion, and poor fetal and calf development. The deficiency of vitamin E can result in muscular dystrophy that can be partially reversed with the supplementation of Se. Other signs of vitamin E deficiency in cattle include retained placenta, metritis, cystic ovaries and infertility.
Sources and Quality: Grazing cattle are rarely subject to vitamin deficiencies; however, most vitamins have little to no storage in the body. Supplementation of vitamins A and E is warranted when cattle are feeding on crop residues such as corn stalks, and stemmy or weathered hay (subject to UV light, heat and rain/humidity) and have little access to fresh pastures. Vitamin premixes may be added to mineral supplements or vitamin injection should be indicated in case of cattle already showing clinical signs of deficiency. For more information on minerals and vitamins, visit the section Mineral and Vitamin Supplementation in the Nutrition and Feeding Management chapter.
Pasture: The primary source of nutrients for cow-calf operations in Louisiana are pastures. Quality and quantity depend on forage type, maturity and management practices. Louisiana is blessed with two forage growing seasons: warm-season forages (typically bermudagrass and bahiagrass) and cool-season forages (usually annual ryegrass and clover). Supplementation is necessary to meet energy and protein needs, especially during periods of low forage quantity and/or quality. Pasture availability varies throughout the year, but it is critical during the transition from cool-season to warm-season pastures in the late spring/early summer when cool-season forages reach maturity, and vice-versa, in the late summer/fall, when warm-season forage stands decline. Supplementation is necessary to fill those nutritional gaps. Nutrient shortages typically occur during those periods of seasonal transition and could be minimized by offering preserved forages (hay and baleage/haylage) or grain/concentrate supplements. Table 1 (check PDF) describes a typical nutrient profile of Louisiana forages. Commercial supplements, mineral blocks and specific feed additives can be used, but regular monitoring of body condition, weight gain and overall health is essential.
Preconditioning Programs: Cattle raised in Louisiana are often sold at weaning as stocker calves or later for finishing at feedlots elsewhere. Preconditioning programs often involve feed bunk training, feed transitioning and health programs. They are designed to prepare growing cattle for the next stage in beef production systems, thus improving the adaptation process and usually increasing the sale value to producers. Close attention should be paid to balancing rations with adequate fiber to prevent digestive disorders.
Meeting the nutrient requirements of beef cattle through a balanced diet is essential for their health, productivity and the economic success of beef production operations. Providing adequate water, energy, protein, minerals and vitamins tailored to the specific needs of the cattle ensures optimal growth and reproductive performance and is more economical. Nutritional plans should be designed based on performance, forage availability and changing requirements throughout the production cycle. Consulting with a livestock nutritionist can optimize feeding programs and improve cattle performance.
National Academies of Sciences, Engineering, and Medicine. 2016. Nutrient Requirements of Beef Cattle, Eighth Revised Edition. Washington, DC: The National Academies Press. doi: 10.17226/19014.
Edwards, A. K., and M. Ferreira. 2024. Preparing Beef Cattle Operations for Drought. LSU AgCenter Fact Sheet. https://www.lsuagcenter.com/articles/page1719950002833.