Dr. Francis Fluharty, Research Professor, Department of Animal Sciences, The Ohio State University
Regardless of the animals stage of production or time of year, Dr. Fluharty reminds us that mineral supplementation is important! Although mineral
can be quite costly initially, Dr. Fluharty outlines the risks and production losses associated with the lack of mineral supplementation.
The major nutritional requirements are: water, energy, protein, minerals, and vitamins. In many cases, sheep producers do a good job of providing adequate water, energy, and protein. However, many sheep producers buy ‘cheap’ minerals, ignoring the fact that the availability of the minerals in the oxide form is low. In many of these mixes, only 10-20% are absorbable by the animal when compared to the sulfate, chloride, organic, or chelated forms (when minerals are metals bound to an organic compound such as an amino acid such as in zinc methionine or organic selenium in selenomethionine; Spears, 2003) in more expensive mineral mixes. The advantage of more available forms of minerals are seen when stress increases. Consider the fact that weather can be a stress, whether it’s extreme heat or cold, and that working sheep at deworming, vaccination, and weaning can be stressors. So, why do so many producers buy minerals that don’t provide the best nutrition to the animal when they need it most, and buy the cheapest mineral instead?
In many cases, it’s because we think in terms of tons rather than days. A ton of mineral seems expensive relative to a ton of hay or grain, but not when you consider that a ton of mineral contains 32,000 oz. (2000 lbs. x 16 oz./lb.) with an anticipated intake of 1.5 oz./hd./day will provide feed for 21,333 animal days. I can’t imagine a sheep producer going to their truck dealership and asking for the truck with the least power when it’s under a load, or asking for the truck with the weakest transmission, but we do this same thing when we buy minerals with the poorest absorption during times of stress. As a result, we then buy additional hay, or grain, or treat sick newborn lambs, or blame the ewe for having weak lambs that die shortly after birth. With the price of lambs, how much is having a greater survival rate, or more twins that are raised?
Macro minerals are described as those required at concentrations greater than 100 parts per million (ppm) of the diet and are often expressed as a percentage of the diet. Trace minerals are considered to be those required at concentrations less than 100 ppm (McDowell, 1992). Macro minerals include calcium, phosphorus, potassium, magnesium, sulfur, sodium, and chloride (salt); whereas the trace minerals include cobalt, copper, iodine, manganese, selenium, iron, and zinc (NRC, 2007). Even though copper is toxic at high levels, it is a required trace element, with the maximum tolerable copper concentration for sheep being 15 mg./kg. dry matter (DM) when their diets contain normal molybdenum (1-2 mg./kg. DM) and sulfur (0.15-0.25%) concentrations (NRC, 2007; page 129). One of the concepts that must be understood about mineral nutrition of sheep regarding copper is that the balance of minerals is critical. Copper toxicity in sheep usually results from the accumulation of copper in the liver over a period of time with no clinical signs followed by a sudden release of liver copper stores during a period of stress, which may result from excessive copper intakes or from low intakes of molybdenum, sulfur, zinc, calcium or following liver damage (Kimberling, 1988).
In terms of vitamins, the most commonly deficient vitamin is vitamin A; whereas vitamin D is synthesized by sheep exposed to sunlight or fed sun-cured forages, and vitamin E concentrations are high in fresh forages. Rumen micro-flora synthesize B-vitamins in sufficient quantities, and B-vitamin supplementation is not normally needed. It is important to remember, however, that the most important nutrient is the one that is missing or deficient, and in the case of nutrient imbalances, there can be more than one! Magnesium, and the trace mineral manganese are cofactors in the energy producing metabolic pathways, and deficiencies can limit energy production and utilization at the tissue level.
As an example, let us say that a sheep mineral is $1200 per ton. This seems like a lot of money, so producers tend to purchase the cheapest mineral possible. However, at a 1.5 oz./day intake, the mineral only costs $0.056/day ($1200/ton ÷ 2000 lbs. = $0.60/lb.). At $0.60/lb. ÷ 16 oz./lb. = $0.0375/oz. If the intake is 1.5 oz./day, that is $0.056/day for mineral ($0.0375/oz. x 1.5 oz./day). The cost of really great mineral nutrition is only $20.50/animal/year (365 days × $0.056/day)! Well, does that pay?
Let’s assume that the price of lambs is $2.00/lb. If the ewe’s nutritional status is insufficient, and she does not breed on her first estrus, it will be 15-17 days before she can re-breed. Normally, lambs should gain approximately 0.5-0.75 lbs./day. That’s a loss of $15.00-$25.50, even for a ewe that later becomes pregnant. On average, that’s as much at the entire mineral nutrition cost for the ewe for the entire year! In addition, many producers supplement their flocks with distillers grains or corn. If dry distillers grains (DDG) are $175/ton, that’s $0.0875 per pound ($175/ton ÷ 2000 lb./ton), and if corn is $5.60 per bushel, it costs $0.10/lb. ($5.60/bu. ÷ 56 lb./bu.). If a producer supplements their ewes with 1.5 lbs. of DDG or corn for 60 days in late gestation and early lactation in order to keep good body condition and provide enough energy for multiple fetuses during gestation, it would cost $0.13/day for DDG, and $0.15 per day for corn. That’s $7.80 for DDG, and $9.00 for corn and that doesn’t include the cost and time involved with transportation and feeding. This doesn’t even take into account the number of lambs that are born weak, or the fact that the quality of colostrum is impacted by nutrition. Why not feed a mineral mix that improves the entire management of the ewe flock, allows the ewe to take advantage of improvements in body condition throughout the summer and fall, and improves her ability to deliver a live lamb and then rebreed in a timely manner. Producers could reduce energy and protein supplementation costs, reduce the average number of days from lambing to re-breeding, reduce the number of lambs treated for illness due to poor immunity early in life, and increase the total pounds of lambs weaned and whole-farm profitability potential, and focus more time on management.
- National Research Council (NRC), 2007. Nutrient Requirements of Small Ruminants. National Academy Press. Washington, DC.
- Kimberling, C.V. 1988., Jensen and Swift’s Disease of Sheep, 3rd Edition. Published by Lea and Febiger, Philadelphia, PA. pp. 372-374.
- McDowell, L. R. 1992. Minerals in Animal and Human Nutrition. Academic Press Inc. Harcourt Brace Jovanovich Publishers, San Diego, CA.
- Spears, Jerry W. 2003. Trace mineral bioavailability in ruminants. Journal of Nutrition. 133:1506S-1509S.