Calculating rations for winter feeding

Calculating rations for winter feeding of gestating and lactating meat goats

Posted by Guest Author on Jun 2, 2017 3:58:48 PM

For most owners, hays are the basic feedstuff used during the winter months when pastures are not adequate to support the nutrient needs of their goats. In non-grazing situations, the daily feed intake (DFI) of gestating or lactating does can be composed of one or more hays or some combination of hay and concentrate to provide the required dietary levels of protein (CP) and energy (TDN). If the available hay(s) contain sufficient percentage of CP (%CP) and percentage of TDN (%TDN) and are fed ad lib, there will be no need to offer supplements (other than perhaps a mineral mix) to these classes of does. Contrarily, if the available forages are inadequate in CP and/or TDN, it usually is cost-beneficial to provide supplements to achieve desired DFI .

Goat producers commonly count the cost of concentrates for their herd as one of the most influential factors affecting net goat-farming income. Table 3 (page 13) shows %CP and %TDN composition of feedstuffs. The composition of grains, protein meals, and processed products are much less variable than hay composition. I caution readers that ‘simple’ supplementation is usually the cheapest supplementation; commercial concentrates may have serious markups in the colorful 50 lb bag along with sweet smelling, beautifully textured or pelleted feedstuffs.

Screen Shot 2017-05-18 at 5.22.43 PM.pngHow to use Tables 1, 2, and 3

It is important to note that the composition figures shown in Table 2 below for hays are generally averages derived from ruminant feeding experiments; a few are derived from laboratory analyses only. The nutritive value (quality) of any forage is influenced by its age at harvesting (either as pasture or hay) and by the leaf-stem ratio saved (influenced by haymaking procedures and storage conditions). Variations from the average composition figures may range widely (10-20% or more in CP and 7-15% in TDN). Consequently, a lab analysis for percentage of CP and percentage of TDN is essential for accurate feeding and, if needed, for proper supplementation; the analytical costs are trifling relative to returns.

To get started, using Table 1, identify the class of doe to be fed. For example, does that are in early lactation, suckling twins, and weighing about 132 lb will, on average, consume about 4.3 lb of diet/day; it should contain .46 lb CP and 2.05 lb TDN, or about 10.7% CP and about 48% TDN, as fed-basis.

Then, using Table 2, note the average composition of your hay, or hays. If you have a lab analysis of your hay, use those figures rather than the textbook figures for better accuracy. If your hay is adequate, or higher, in the percentage of CP and the percentage of TDN, offer no supplement. If the hay is inadequate, some higher protein hay or concentrate will be required. Note that most all the hays in Table 2 have TDN percentages adequate for most classes of does; contrarily, the CP percentage in many grass hays can be inadequate for certain classes.

Examples of ration balancing

Given the 132 lb doe in early lactation, suckling twins:

Example 1

You have 8% CP Timothy hay and 16% CP Alfalfa hay. The Timothy is inadequate in CP and the Alfalfa has more CP than the doe can utilize (the excess is wasted); thus a mixture of the hays is required. To get a mixture with 10.7% CP, use a Pearson’s Square to calculate as follows*:

Parts Alfalfa = 8% CP (The %CP of the Timothy hay) minus 10.7% CP (the target %CP) = -2.7 parts. Remove the negative sign to find the parts Alfalfa needed (2.7 parts).

Parts Timothy hay = 16% CP (The %CP of the Alfalfa) minus 10.7% CP (the target %CP) = 5.3 parts

Taking a total of 8 parts, calculate the percentage of each ingredient and then the weight of each feedstuff needed:

2.7/8 x 100 = 33.75% x 4.3 lb DFI = 1.45 lb Alfalfa

5.3/8 x 100 = 66.25% x 4.3 lb DFI = 2.87 lb Timothy

Total DFI = 4.32 lb

Pearson Square.png

*See http://community.easykeeper.com/easykeeper-extension/pearsons-square for a Pearson’s Square rations balancer.

In the real world, for this example, you could offer Alfalfa (1.45 lbs per doe) in the morning and Timothy (2.87 lb per doe) in the evening. Or, perhaps more conveniently, you could offer Alfalfa and Timothy ad lib on alternate days; in this case, the does would eat more Alfalfa than they needed. Such a 50:50 mixture would test 12% CP (16+8 /2), not 10.7%; which is not a serious issue given the labor savings.

Example 2

You have 8% CP Timothy and wish to feed a grain supplement rather than buy Alfalfa hay. You could offer 1.45 lb of a 16% CP concentrate and 2.85 lb Timothy. The relative prices of concentrate and Alfalfa hay would be the decisive consideration; the does would do well in either case. Alternatively, you could feed 1 lb of 24% CP concentrate plus 3.3 lb of Timothy hay and get the same result. Either concentrate would supply more TDN/lb than Alfalfa hay.

Screen Shot 2017-05-18 at 5.22.57 PM.pngIf you have hay testing 11% CP or more (and thus require no supplementation) would each goat eat 4.3 lb of hay/day? Of course not, but if you were feeding 100 such does, they would together eat about 430 lb/day, at least in theory. As a practical matter, one could initially offer 10% more than Table 1 DFI figures indicate (by weighing the bales for 2-3 days), and then quickly reduce the waste as needed. When one feeds round bales, it is more difficult to gauge actual consumption; one merely surmises that if the group’s body condition remains within the desired range for the does’ life-stage/class, all goats are getting enough and, further, that the wastage is tolerable.

Returning to Table 1, if your group of lactating goats had a wide range of body weights or if some were suckling singles, twins, or triplets, your real choices would be:

  • To separate them into individual management groups and feed more nearly according to their needs or,
  • To strike an average DFI (and thus underfeed or overfeed some) or,
  • To offer all of the goats all they can eat all the time (in which case, some will surely fatten).

Special considerations for late gestation does carrying multiples

Returning to Table 1 and looking at the protein and TDN figures needed for early and late gestation periods for does carrying twins and triplets, you’ll see that late gestation does require at least 12% CP and about 60% TDN in the diet if they eat the ‘average’ DFI. In late gestation, there is a contest for space in the abdominal cavity; increasing placental mass reduces rumen space right when the doe needs to eat more. The solution is to increase the dietary density (energy/bite) by raising the %TDN in the ration.

Legume hays and mixtures of legume and grass hays can furnish the 12% CP, or more, as shown in Table 2. The crucial concern, then, is supplying enough TDN in diets during late gestation. Table 2 shows no hays testing near the 60% TDN. The solution is to offer extra dietary TDN in the form of corn or concentrate (in most cases 1-1.5 lb/head day). Note that corn is only 8% CP so the CP in the hay would have to be raised to 15-16% rather than 12% to compensate. Using a 12% CP concentrate would solve this issue.

Screen Shot 2017-05-18 at 5.22.28 PM.pngBalancing the %CP in a daily diet

As indicated in Table 1, diets that contain 12-13% CP, as-fed basis, are sufficient to provide even the highest daily protein needs; with the possible exception of young doelings, other classes of goats require lower percentages of CP. This being the case, if you are purchasing hay, choose hays that test at least 12% CP (as-fed basis) if the prices aren’t exorbitant. If such hays are over-priced or simply unavailable, your option is to buy hay with less protein and supplement it with a higher protein feedstuff (a concentrate or sometimes a single feedstuff).

The basic calculation to decide the proportions of hay and concentrate in a given diet (DFI) can be done using a Pearson’s Square as illustrated earlier. Suppose you needed a diet containing 10% CP and you had hay testing 6% CP; how much distiller’s dried grain (29% CP; See Table 3) and hay (6% CP) would you need to make 5.08 lb of a ‘blended diet’ testing 10% CP for a mid-lactation doe suckling twins.

Parts Distiller’s dried grain (DDG) = 6% CP (The %CP of hay) minus 10% ( the target %CP) = -4 (remove the negative sign to find the parts Distiller’s dried grain needed (4 parts).

Parts hay: 29% CP (The %CP of DDG) minus 10% (the target %CP) = 19 parts

4 parts DDG + 19 parts Hay = 23 parts

Calculate the percentage of each ingredient and then the weight of each feedstuff needed:

4/23 x 100 = 17.39% x 5.08 lb DFI = 0.88 lb DDG

19/23 x 100 = 82.61% x 5.08 lb DFI = 4.20 lb hay

Total DFI = 5.08 lb

In this scenario, you could offer a lb of DDG per head/day in a communal trough and offer the hay ad lib. Barn reality mostly always trumps math when feeding goats.

It is important to note that this magic Square only works if the middle figure (10, in the this example) falls between the two figures to the left (29 and 6). In a correctly configured Square, the difference between these two figures on the left corners will always be equal to the sum of the two figures on the right corners (in this case, 23 = 23). If that computation is not equal, the Square must be reconfigured.

For example, you cannot use 8% CP corn to supplement 6% CP hay; even a 50:50 mixture would still test only 7% CP and still be 30% short of the needed 10% CP in the diet.

In closing, I concede that the nutrient requirements of meat goats are more accurately described than many of their owners can apply in practical circumstances… but don’t worry, make your calculations for guidance only, and then do some trial-and-error feeding of feedstuff and measure your results to find the right mix for your herd.

 

Table 1

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Table 2 

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Table 2.3.png

Table 3

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Table 3.2.png

Table 3.3.png

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frank_sepia.pngAbout the Author

Dr. Frank Pinkerton is one of the industry’s most highly regarded writers and speakers on meat goat nutrition, marketing and management. His book, A Compilation of the Wit and Wisdom of the “The Goat Man” is available at the Goat Rancher Store. He can be reached by phone at 512.392.4123 or email, [email protected].

  


 

 Photos courtesy of Montero/Clinger Goat Farms and the North American Savannah Goat Association.

Topics: Meat goat, Nutrition