WW-00469 Reviewed 2008
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The objective in formulating rations is to provide animals with a consumable quantity of feed stuffs that will supply all required nutrients in adequate or greater amounts and do so in a cost effective way. Today, almost all rations are formulated with the aid of a computer compared with only a few years ago when all rations were hand calculated. Use of computers has resulted in more complete evaluations of nutrient profiles in rations and allowed for economics to be included in ration formulation decisions. The four most common ways of expressing computer ration information are:
Analyze. A ration analysis is a summation of all feeds in the ration and the nutrients they contribute. An analysis does not balance the ration, and therefore does not correct any nutrient deficiencies or excesses. The amount of each feed fed, along with its nutrient composition, must be known to obtain an accurate ration analysis.
Balancer. A ration balancer program combines feeds to meet the nutrient specifications set for a ration. The amount of each feed to be included in the ration will be determined based on its nutrient contributions and how it fits with other feeds in meeting nutrient specifications. A balancer program does not consider feed costs or profit.
Least cost. A typical least cost formulation involves specifying the nutrient requirements or constraints for the ration and then finding the combination of feeds that meet or exceed these constraints at the lowest cost per pound of DM. Least cost formulations change as feed costs change. An opportunity or break-even cost for feeds not used in the ration will often be given. When the price of an unused feed goes below the opportunity price, it is considered a good buy and the ration should be reformulated to see how much of that feed can now be used in the ration.
Maximum profit. A true maximum profit ration program includes a least cost function, incorporates milk price information, and uses a maximum profit (income over feed cost) as one of the constraints or specifications to formulate on. The difference between maximum profit and least cost or balanced rations is that the computer selects feeds and a milk production level to obtain a maximum profit; whereas, in least cost or balanced rations the computer selects only feeds to meet the nutrient requirements specified for a given level of milk production.
|Step 1.||Use tables A-6, A-7, and A-8 to determine nutrient requirements. Forage tests, feed tags, and tables A-9, A-10, and A-11 should be used as sources of nutrient information in feedstuffs.|
|Step 2.||Weigh the amount of each forage fed. Calculate pounds of DM from each forage.|
|Step 3.||Determine nutrient contribution of forages. Multiply pounds of forage DM by nutrient content.
|Step 4.||Subtract nutrients contributed from the forages from the nutrient requirements determined in step 1|
|Step 5.||Total the pounds of forage DM fed and subtract this amount from the projected total DMI given in table 15. The difference is the amount of grain needed.|
|Step 6.||The Pearson Square technique can be used to determine proportions of different grains in a grain mix, based on net energy, or more commonly, to determine the protein content of the grain mix. An example for protein will be given here.|
|Example:||2000 x 18%
|= 360 lb of SBM DM|
|360 x 100
|= 400 lb as feed|
|Percentage shelled corn =
Percentage SBM =
| 33/40 x 100
7/40 x 100
Cow Data: (Weight, lb 1300) (Milk, lb/day 80) (Fat, % 3.5) (Age, months 48) (Days in Milk 120) (Weight gain, lb/day 1)
(Milk lb x .4) + (Fat lb x 15) = 74 lb FCM
|Requirements||Crude protein||Net energy||Calcium||Phosphorus|
|Maintenance (table A-6)||.89||9.6||25||17|
|Gestation (table A-6)||-||-||-||-|
|Growth - heifers (table A-6)||-||-||-||-|
|Production (tables A-7, A-8)||6.72||24.8||109||66|
|Weight gain (table A-6)||.32||2.32||-||-|
|Total (table 15)|
|Body weight (cwt) x||Intake % of body weight||= Pounds of DM|
|13 x||3.70||= 48.1|
|Kind of feed||lb feed||x||% DM||=||lb DM|
|Protein suppl (SBM)||6.5||x||90||=||5.8|
|Nutrients Provided (tables A-9, A-10, and A-11)|
|A x 1 = Crude protein (CP)||A x 3 = Calcium (Ca)|
|A x 2 = Net energy, Mcal (NE)||A x 4 = Phosphorus (P)|
|Difference from requirements (+,-)||+.52||0.0||+44||+6|
|Ration %||9.3/49.3 = 18.9||14.5/49.3 = 29.4|
|NDF from forage, %||12.4/49.3 = 25.2 or 12.4/14.5 = 85.5% of total|
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