CALF_News_August_September_2020

38 CALF News • August | September 2020 • www.calfnews.net Cattle lead diverse lives Beef cattle can be classified into many different management groups. Each animal in a particular contemporary group shares similar nutritional requirements. Groups can be formed by age, gender, performance or production, but age and gender are the easiest parameters to use. Groupings can transition over time; as calves age, their nutritional needs will fluctuate. Mineral supplementation should be tailored to each group and comple- ment available forages and feedstuffs. For example, a cow will provide nourishment for young calves, but as the calves age, their nutritional requirements are no longer met by milk alone. Forage will gradually provide a larger portion of nutrients. This will influence their require- ments and, if not managed properly, lead to production losses. Weaning calves creates stress; a major shift in nutrient requirements takes place because of diet changes, necessitating supplementation for optimal production. Post-weaning growth requirements can be different based on future production expec- tations, like becoming a feeder calf rather than a replacement animal. To determine the mineral supplementation needs of your cattle, it is imperative to know what age, weight and stage of life they are in, and what they are consuming from their daily diets. Edmondson recommends collecting and sending forage or ration samples to a lab for analysis. Dry mater intake (DMI) should then be calculated to estimate minerals provided by the feedstuffs. Edmondson says, for grazing animals, dry matter intake (DMI) for each animal is commonly estimated at 2 to 2.5 per- cent of the mature animal’s weight. However, there are many variables that can affect the DMI in cattle. Rumen develop- ment stage, age, weight and forage quality are all factors. Forage quality is most likely to deviate from year to year, and from month to month. As plant nutrient values decrease as forages mature, rumen bacteria will require more time to digest feedstuffs. Slowing down digestion means that feeds take up space in the rumen for a longer period. The cattle cannot eat more until space becomes available, which decreases DMI. Cattle weights can be an indication of rumen capacity. Lighter weight calves will eat a higher percentage of their body weight compared to heavier animals. This is a function of adding more body capacity over time as compared to addi- tional rumen capacity. All tied up Edmondson explains that the ability for cattle to break down compounds into usable, absorbable forms is called bioavailability. It can determine the price paid for and value realized from a mineral supplement. Bioavailability is an important factor in determining mineral quality. For example, several sources of copper compounds can be used to formulate a supplement that delivers 1,200 parts per million (ppm) of copper. It will be listed that way on the feed tag. The specific source of copper compound, however, affects how the supplement reacts in the gastrointestinal tract, which in turn affects its bioavailability. Copper oxide tagged at 1,200 ppm, for instance, would deliver a small level of copper to the animal due to cattle’s inability to break it down into a usable form. It is important to identify the mineral sources used; cheap sources may not be worth the trip to town to pick them up. Chelated minerals are generally the highest quality and most available of all options on the market. Trace minerals, or microminerals, have significant effects on rumen bacteria. A case in point: university studies have indi- cated that forage digestibility can increase by 12 to 24 percent when cattle are supplemented with rumen-available cobalt. Rumen bacteria have small requirements for other trace minerals like copper, zinc and manganese. These requirements are so small that they are almost always met by other feed- stuffs, barring stress episodes. Additionally, cattle themselves have trace mineral requirements that compete with the rumen bacteria needs. These trace minerals are more beneficial when the rumen is bypassed, and they are absorbed in the lower gastrointestinal tract.  MINERAL SUPPLEMENTS Continued from page 36 Mature animals no longer need to meet growth targets so nutrient needs should be adjusted to maintenance levels. Levels of essential nutrients change seasonally with available forages and with changes in production classes (pregnant, lactating or dry). This requires producers to change how mature animals are supplemented. Our feedstuffs vary Cattle have specific nutrient and mineral needs that must be met. Each bodily process competes with others over mineral availability. The ability of the body to store and overcome short-term deficiencies varies by mineral and animal. Macrominerals include calcium, phosphorus, magnesium, potassium, sodium and chloride (salt) and sulfur. Their needs fluctuate based on stage of production and age of the animal. Microminerals, however, do not fluctuate much based on age or stage of production, but can be affected by stress events.