Making Sense of Feed Labels Part 2: Balancing major minerals in your goat’s diet
In Making Sense of Feed Labels, Part 1: Balancing trace mineral deficiencies in your goat’s diet, we learned how to determine if your mineral supplement balances deficiencies in trace minerals, such as copper, zinc and selenium. Daily mineral requirements for goats were based on diets for large breed diary cattle adjusted for differences in body weight. We will use the same approach in balancing the major minerals listed in Table 1. As mentioned in Part 1, mineral balancing requires feed concentrations expressed in weight rather than percent (%), or parts per million (ppm). Conversion from percent major mineral to weight involves some very simple math. For example, the minimum calcium (Ca) concentration in Table 1 is 15.5%, which is equivalent to 15.5 g/100 g, or 155 g/1000 g = 155 g/1 kg = 155 g/2.2 lb. If you are still uncomfortable using metric units, conversions from English to metric units are shown below.
Conversions between metric and English units
1 gram (g) = 1/28 ounce (oz) = 0.0357 oz, or 28 g = 1 oz
1/1000 g = 0.001 g = 1 milligram (mg) = 0.0000357 oz
1/1,000,00 g = 0.000001 g = 1 microgram (mcg)
1000 g = 1 kilogram (kg) = 2.2 pound (lb)
1 part per million (ppm) = 1 mg/kg = 1 mg/2.2 lb
Table 2 shows the mineral content of two hays fed to our dairy goats. One pasture analysis (Pasture) from our farm is also included for comparison. Hay 1 is high-Ca alfalfa with relatively high iron (Fe) content. Crude protein (CP), which is calculated from protein and non-protein nitrogen in feed, is 16%. Hay 2 is typical low-Fe mixed grass hay from this area, consisting predominantly of fescue with CP = 10%. Pasture sample is mixed grass collected in October with CP = 22%. You can go to the Dairy One website for more information on interpretation of hay and pasture analyses.
Table 3 shows the calculated requirements for diary goats based on the nutritional requirements of large breed dairy cattle. These are compared to the total daily mineral intake from Hay 2 and our local supplement. The mineral balance expressed in terms of excesses and deficits is listed in Table 4. Also included in the table is the trace mineral balance from Part 1.With the exception of slight deficiencies in sodium (Na) and magnesium (Mg), all minerals are in excess of requirements.
For this combination of hay and supplement, the Ca/P ratio is 1.7:1 (19/11), which is within the acceptable range for ruminants (1:1 to 7:1). Most ready-mixed commercial mineral supplements are formulated with a 2:1 Ca/P ratio. Look for the ratio on the feed label, e.g., 2:1 Goat Mineral.
Sodium (Na) is almost always deficient in forage and must be supplemented. One exception is forage grown along the coasts where unusually high Na concentrations are due to atmospheric deposition of sea salt. In this example, most of the deficiency is balanced by our supplement and only 0.2 g (200 mg) Na is required to meet the daily requirement. This amount of Na is contained in 500 mg salt because salt consists of 40% Na and 60% Cl (divide Na amount required by 0.4). To ensure that your goats meet this requirement, sprinkle a small amount of salt on their feed, or purchase an inexpensive gram scale to weigh out milligram amounts. If you are also feeding a dairy concentrate which lists salt in the guaranteed analysis Na will be in excess of requirement.
Magnesium (Mg) is slightly deficient and may require supplementation with magnesium oxide (MgO) in the spring months if grass is a large proportion of your goat’s diet. The lower Mg concentration in spring grass coupled with high concentrations of potassium (K) and organic acids limits absorption of dietary Mg, which can result in a serious metabolic disorder called grass tetany. Cattle are usually fed a high-Mg mineral supplement (14% Mg) in the spring to balance this deficiency.
In Part 1, we discussed how copper (Cu) bioavailability is affected by Fe, molybdenum (Mo) and sulfur (S) interactions. Sulfur can also affect selenium (Se) bioavailability if present in high concentrations (Spears 2004). This is another reason to analyze both your forage and drinking water.
If you are concerned about whether your goat’s diet meets nutritional requirements, test your forage and calculate mineral balance using the methods outlined above and in Part 1. Goat models based on cattle requirements are only approximate but can still provide useful information on feeding guidelines for your nutritional program.
In Part 3 of this series, we will take a look at vitamins, another essential component of your goat’s diet.
George Lager is Professor Emeritus of Geosciences, University of Louisville, Louisville, Kentucky. He has raised dairy goats for about 10 years to satisfy his craving for unpasteurized milk and raw goat cheese! He and his wife Marjorie live on a small farm near Corydon, Indiana where, in addition to goats, they raise wild mustang horses, donkeys, one pet hog, chickens and some crazy geese (not to mention two German Shepherds and 10 cats)! Visit www.mitchellplainfarm.com for more articles about their animals and farm projects.
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