Mature bucks can obtain most of their nutrients from pasture. However, yearling and 2-year-old bucks have greater nutrient requirements since they are still growing. Bucks need to be in good body condition, with a body condition score (BCS) greater than 3, before the breeding season because feed intake may be relatively low during that time, resulting in weight loss. Thus, body condition should be evaluated three months before the breeding season. Decisions can then be made on the supplemental nutrition needed for the buck to achieve the desired BCS.
Whenever bucks cannot meet nutritional needs from pasture, supplementation is necessary. Under most conditions, whole, shelled corn or sweet feed at 0.25 percent to 0.5 percent of body weight will be adequate (0.5 to 1 pound of feed for a 200-pound buck). Feeding bucks high levels of grain at more than 1.5 percent of body weight for a long period of time makes them prone to urinary calculi. The levels of grain recommended above are safe for bucks. When pasture is scarce, bucks can be fed medium quality hay free-choice.
Using the Langston Interactive Nutrient Calculator (LINC), calculate the nutrient requirements for a 3-year-old, 200-pound Boer cross-buck, gaining no weight, and on pasture (intensive management). The calculated requirements are 2.39 percent of total digestible nutrients (TDN), 0.26 pounds of crude protein (CP), 5.05 grams calcium, and 4.09 grams phosphorus, with predicted dry matter intake of 3.55 pounds. However, it is important to note that the estimated dry matter intake is influenced by the dietary TDN and CP concentration inputs. In a pasture-based system, the forage (pasture) makes up all or most of the total diet other than perhaps a mineral supplement. If the LINC default TDN and CP values are used and the actual forage base (pasture) has different TDN and CP levels than the default values then the predicted dry matter intake may not be close to the actual amount. In the example above, default values were assumed. To determine if these nutrient requirements can be met by native range with a mineral supplement, click “Select Feed Ingredients” at the bottom of the page. A page listing different feeds will appear. In the “Forages” section below “Concentrates,” click “range, early summer,” and under “Minerals” choose a 12-12 mineral supplement. Go to the bottom and click “Input These Feed Ingredients into the Ration.”
The ration window that lists each ingredient chosen will appear. Intake figures should be entered in the column labeled “Amount, lbs as fed.” The estimated intake for this buck is 3.55 pounds dry matter (pounds of diet not including the water content of the feedstuffs), whereas in this window the consumption amount is entered as the “as fed” form. Because feedstuffs vary in water content (compare the water content of fresh, green pasture to the same forage dried and harvested as hay), nutrient requirements and intake estimations are calculated on a “dry matter basis.” Dry matter basis means that all water has been removed. However, animals eat feed in an “as-fed” form. This calculator will determine the amount of dry matter intake for each ingredient from the as-fed figures entered. This relieves the producer from having to estimate dry matter, allowing the amount fed to the animal to be entered, with the program performing the needed dry matter calculations.
The mineral supplement bag label predicts intake of 0.5 to 1 pound/per month/per 100 pounds of body weight. At that rate, the 200-pound buck will consume 2 pounds a month or 0.067 pounds a day, roughly 1 ounce. Some supplements estimate an intake such as 1 to 1.5 ounces per day, but this can vary with the size of the goat. Enter 0.07 pounds for the mineral. Therefore, in this example it can be assumed that forage dry matter intake is 3.55 pounds. The value of 3.55 is entered into the “Amount, as-fed” column for range forage. Clicking in the “Amount, lbs DM” column will calculate the amount of DM and nutrients provided (Running total) compared with the Requirements. The amount of as-fed native range grass provided should be increased until the forage dry matter provided equals the 3.55 pounds previously calculated. This is done by trial and error method until a correct answer is found. In this case, the correct amount is 3.95 pounds of as-fed native range, which will provide 3.55 pounds of dry matter. Therefore, the estimated daily ration for this buck is 3.95 pounds of native range grass hay, or an equivalent amount of pasture, on a dry matter basis plus 0.07 pounds of mineral per day.
Comparing the Running total with the Requirements shows that this diet did not meet the requirement for TDN (2.12 pounds provided versus a requirement of 2.39, 89 percent). Crude protein, calcium and phosphorus are supplied in excess of requirements. Because the equations used in these predictions include a small safety margin — that is, requirements are most likely slightly greater than actual — if the deficiency is not marked, the diet could be used as is with careful monitoring of performance measures, most notably BCS. In addition, one should consider that the diet actually consumed could be higher in quality than the book composition values used. In this regard, people taking plant samples often cut at the ground level, such as for hay. Conversely, goats select certain plant parts, especially leaves, that have higher nutrient contents. Therefore, the composition analysis used in the calculations might not have matched what was actually eaten. For example, if a TDN concentration in consumed forage of 65 percent and a crude protein level of 12 percent are assumed, the predicted TDN intake is 95 percent of that necessary to satisfy the TDN requirement.
Accurate and abundant data on the nutrient content of plant parts consumed by goats are lacking. When hay is fed and animals are forced to consume most of it, the hay analysis will closely match what is consumed. The same applies to supplemental feeds that are totally consumed. One way to more accurately determine the true composition of diets of grazing goats is to follow the animals for a couple of hours and hand pluck the portions of plants consumed and send the sample in for analysis. However, plant composition and plant parts selected vary over time, making it desirable to sample plants monthly or more frequently. In the absence of feed nutrient analysis, it is important to try to match the description of feeds or pasture as closely as possible to that in the LINC feed tables. If actual analysis has been determined, it can be entered into LINC at the bottom of the feed library. Information required includes concentrations of TDN, crude protein, calcium, and phosphorus. Hopefully in the future, more applicable data will be available for herbage grazed by goats.
Reference: Hart, S. 2008. Meat Goat Nutrition. Pages 58-83 in Proc. 23rd Ann. Goat Field Day, Langston University, Langston, OK.