Feeding the dairy herd
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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.
Ration Formulation Thumb Rules–Lactating Cows
- DMI needs to be known. Use table 15 as a guideline.
- Forage DM minimum is 40 percent of the total DM intake or approximately 1.5 percent of body weight.
- Maximum grain DM is 60 percent of total DMI, or not more than 2 percent of body weight. Between 10 and 70 pounds of milk per day, feed grain at 1 pound per 3 pounds of milk, and above 70 pounds of milk, feed grain at 1 pound per 3.5 pounds of milk.
- Minimum recommended acid detergent fiber (ADF) in ration DM is 18 percent, with 19 to 20 percent preferable, especially when fat is fed
- Neutral detergent fiber (NDF) should be at least 28 percent of the ration DM. Forages should account for 75 percent or more of the total ration NDF (1.2 percent of body weight or 21 percent of ration DM).
- Protein needs to meet requirements (17 to 19% in early lactation rations). A low rumen degradable protein source may be beneficial in early lactation rations for high producing cows. Limit urea to .4 pounds per cow per day and preferably to not over .2 pounds per day in phase 1 and 2.
- Maximum total fat in rations is 7 percent of the DM. A guideline is no more than 2 percent added fat from any one of three sources, animal, vegetable or rumen inert. Increase calcium to .9 to 1 percent, magnesium to .3 percent, and ADF to 20 percent or more in the ration DM when feeding fat.
- Salt should be included in the grain mix at 1 percent or fed at the daily individual cow rate of 1 ounce for maintenance plus 1 ounce for every 30 pounds of milk.
- A calcium-phosphorus mineral source should be included in the grain mix at 1 to 2 percent or fed at an approximate rate of 1 ounce per 10 pounds of milk.
- Supplement vitamins (A, D, and E) and trace minerals in the ration to meet requirements.
|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.|
- Write the desired protein percentage in the grain mix in the middle of the box. Determine the percentage by dividing the amount of protein needed by the estimated amount of grain DM.
- Example: 17%
- Write the protein percentage (DM basis) of the grain and protein supplement in the left corners of the square.
- Example: 10 and 50%
- Subtract diagonally and write differences in right corners. These numbers are parts or proportions.
- Example: 17 – 10 = 7 and 50 – 17 = 33
- Example: 33 + 7 = 40
- Percent SBM is 7 divided by 40 x 100 = 18%
- Multiply the size of the batch mix times the percentage of each ingredient to get the pounds of DM necessary. The pounds of DM must be divided by the percent DM of the ingredient to convert to an as-fed basis.
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
In this example 1 ton of DM would contain 1640 pounds of shelled corn and 360 pounds of soybean meal.
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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