Component Feeding Systems


Source: Pennsylvania State University

The goal with component feeding or a PMR is to mimic the approach of a TMR by avoiding wide swings in rumen pH that can cause acidosis, milk fat depression or other performance related issues.


There are two major types of feeding systems: component feeding and a total mixed ration (TMR). Component feeding is when forages, protein supplements, and grains are fed individually to the cow. The amounts delivered can be fed by weight or volume. The other system is a TMR, where all the feeds are weighed and blended together to meet the total nutrient needs of the animals. TMRs can be fed successfully in different housing facilities, i.e., tie-stall or free-stall barns. Component feeding tends to be utilized in tie-stall housing and grazing systems. This feeding approach is quite common in Pennsylvania. Using the 2017 Census of Agricultural data from the USDA National Agricultural Statistics Service, approximately 78 percent of the total dairy operations (6,048) with milk sales have less than 99 milk cows. It is realistic to assume that many herds of those sizes utilize component feeding. Operations that use robotic milking systems would follow many of the guidelines for component feeding systems since they utilize a partial mixed ration (PMR) with much of the concentrate fed through the robot at the milking station. Grazing herds would also incorporate many of the recommendations of component feeding as well. Though, some grazing herds do offer a PMR when animals return from milking, before being released out to pasture or when barns are used as heat abatement during the summer months.

Component-fed cows can have their forage and grain amounts adjusted according to several criteria. This can include body weight, body condition score, stage of lactation, and age. Feeding adjustments can be made if animals have excessive drops in production or experience milk fat depression. Component feeding also lends itself to feeding based on volume versus weight. Feeding sequence or the order in which forages and grains are fed can influence animal performance. All these areas will be covered in this publication.

Forage and Fiber Intake

The following are suggested guidelines for total forage dry matter intake as a percent of body weight.

Minimum: 1.4 percent body weight daily
Example: 1,300 lb. x .014 = 18.2 lb. of forage

Maximum: 2.4 percent body weight daily
Example: 1,300 lb. x .024 = 31.2 lb. of forage

The following are suggested guidelines for total and forage neutral detergent fiber (TNDF/FNDF) intake as a percent of body weight.

Guide for forage intakes

Forage NDF as a percent
of body weight
Intake Level
0.75%* Minimum if ration provides 1.3-1.4% total NDF by use of byproduct feeds.
0.85%* Minimum if ration provides 1.1-1.2% total NDF by use of grains or starchy ingredients.
0.90% Moderately low
0.95% Average
1.00% Moderately high
1.10% Maximum

*Higher minimum may be necessary if forage is chopped exceptionally fine.

Example of FNDF as percent of body weight

0.85 percent body weight
1300 lb. x .0085 = 11.05 lb.

0.75 percent body weight when TNDF is 1.3-1.4 percent of body weight
1300 lb. x .0075 = 9.75 lb. if TNDF is 1300 lb. x .013 = 16.9 lb.

1.1 percent body weight
1300 lb. x .011 = 14.3 lb.

Example of TNDF as percent of body weight

1.1 to 1.2 percent body weight
1300 lb. x .012 = 15.6 lb.

If the ration is formulated for 33 percent TNDF and the dry matter intake is 49 lb., then
0.33 x 49 = 16.2 lb. of TNDF/1300 lb. x 100 = 1.25 percent body weight.

Suggested guidelines for TNDF and FNDF as a percent in the total ration dry matter.

Milk production, lb. TNDF % FNDF %
High >80 lb. 28-32 21-27
Medium 70-80 lb. 33-37 25-32
Low <70 lb. 38-42 29-36

Guidelines for Feeding Forages

The following are general guidelines when feeding cows as individuals. The objective is to minimize digestive upsets by ensuring cows are receiving adequate fiber.

  • First-calf heifers may consume only 85 percent as much forage as the average-sized mature cow.
  • Cows exceeding the average body weight by 100-300 lb. could consume 10 to 20 percent more forage.

Concentrate Intake

The following are general guidelines when feeding grain to cows on an individual basis. The objective is to gradually adjust the amount of concentrate fed to avoid drastic drops in rumen pH and issues associated with acidosis and milk fat depression. Feeding recommendations are based on a complete grain mix on an air-dried basis (approximately 88 percent dry matter). If high moisture grains are fed, the amounts would need to be adjusted accordingly, and the amount of total concentrate to feed (energy and protein supplement) would be combined. All recommendations follow the rule that no animal receives more than 2.5 percent of their body weight in concentrate.

1. Fresh cows
Start animals at a total concentrate level equal to about 1.0 percent of their body weight on freshening day. Increase grain by about 1 lb. as-fed per head daily until reaching a level equal to 2.0 percent of body weight, around 14 days in milk (DIM). If production warrants, keep increasing grain to a maximum level of about 2.5 percent of body weight.

2. Lactating heifers
Feed first-calf heifers 2–3 lb. of concentrate beyond what is needed for milk production to support growth, keeping total concentrate intake within the 2.5 percent maximum (of body weight). Second-calf heifers should be fed 1–2 lb. of extra concentrate for growth requirements.

3. Body condition score (BCS)
Thin cows (BCS < 3 on the 5-point scale) should be given 4–6 lb. more concentrate daily than production warrants. Over-conditioned cows (BCS > 3.75) should have grain reduced by 4–6 lb.

4. Cows experiencing excessive drops in milk production
Milk production drops greater than 10 percent from the previous month should receive grain for the normal level of production or add back 1 lb. of concentrate per 2 lb. of excessive production drop.
Example: A cow had been milking 60 lb./day and drops to 48 lb. /day. Feed grain for 54 lb. of milk (60 x 0.10 = 6 lbs.; 60 – 6 = 54 lb. of milk) or feed 6 / 2 = 3 lb. of concentrate beyond that needed for a cow averaging 48 pounds of milk.

5. Reduction in grain amounts
Gradually reduce concentrate for cows at a rate of 10-15 percent per week.
Example: A cow receiving 30 lb. of grain should be dropped to 24 lb.
Lower 3-4 lb. one week and the rest the following week.

6. Milk fat test adjustment
Cows testing above herd average may need 5-10 percent more concentrate while those below herd average may need 5-10 percent less concentrate.

7. Grain feeding
Guidelines based on forage quality are listed in Table 1. Amounts are on an air-dried basis and reflect total intake per day. If high-moisture grain and a supplement are fed, then the total amount would need to be adjusted to an air-dried basis (88 percent dry matter).
Example:  A cow averaging 75 lb. of milk/day receives 25 lb. of high-moisture shelled corn (70 percent dry matter) and 5 lb. of a protein supplement.
25 x 0.70 = 17.50/0.88 = 19.9 lb. + 5 lb. = 24.9 lb. of grain on an air-dried basis

Table 1. Grain-Feeding Schedules for Different Quality of Forages

(Milk (lb./day)
Schedule 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Total Forage NEL* (Grain to feed daily, lb.)
72 3 3 6 6 8 10 13 16 18 21 23 26 28 31 33
70 3 3 6 8 10 12 15 18 20 23 25 28 30 32 **
67 3 3 8 10 12 14 17 20 22 25 27 30 32 ** **
65 4 6 10 12 14 17 19 22 24 27 29 31 33 ** **
63 4 7 11 13 15 18 20 23 25 28 30 32 34 ** **
61 4 8 12 14 16 19 21 24 26 29 31 33 ** ** **
57 6 9 13 15 17 20 22 25 27 30 32 ** ** ** **

**Levels will depend on body weight. Total concentrate level should not exceed 2.5% of cow body weight.
*Net energy of lactation

Volume Feeding Versus Weight Feeding

It is common in component-fed herds to feed by volume versus weight. The ideal standard would be to weigh all forages and grains fed to the individual cows, however, that is not practical in many situations. Table 2 lists the approximate volume weights for forages and grains.

Table 2. Approximate volume weights for selected feedstuffs

Feed Lb./bu Bu/cwta Lb./cu ftb
Brewer’s grain wet 44 2.27 35
Corn, shelled:
     Whole 56 1.79 45
     Ground 48 2.08 38
Corn, ear:
     Whole, Double bushelc 70 1.43 28
     Single bushel 35 2.86 28
     Ground 45 2.22 36
Dairy feed, 16%
     Coarse, textured 44 2.27 35
     Meal 33 3.03 26
     Pellet 50 2.00 40
Green chop forage 20 5.00 16
Mineral ingredients 58 1.72 72
Silages after removal:
     Corn, whole-plantd 20-30 3.3-5.0 16-24
     Hi-moist ear corn 30-35 2.9-3.3 24-28
     Haylage 15-30 3.3-6.7 12-24
Soybean meal 54 1.85 43

aThe bu/cwt values given in this column may be used as factors to convert bushel prices to hundredweight prices, or vice versa. Example: Whole, shelled corn at $3.00/bu. equals $3.00 x 1.79 or $5.37/cwt; shelled corn at $5.37/cwt equals $5.37/1.79 or $3.00/bu.
bOne standard bushel = 1.25 cubic feet; one standard cubic foot = 0.8 bushels.
cThe standard weight of 70 lb. is usually recognized as being about 2 measured bushels of corn, husked, on the ear, because 70 lb. would normally yield 1 bushel or 56 lb. of shelled corn. One bushel of ear corn = 2.5 cu ft; 1cu ft = 0.4 bushels of ear corn.
dOne comfortably rounded silage forkful (six tine) holds about 1/2 bushel.

In general, pellets have a greater weight than the same material in meal form. Grain mixtures containing a lot of oats or byproducts (i.e., wheat midds, brewers, soyhulls) will typically weigh less per unit of volume than mixtures containing a lot of corn. Bushel weights vary for grains and depending on the growing season, the standard bushel weight for a particular grain could be less, especially during drought conditions. It is recommended to do a calibration for new grain mixes and deliveries by checking the weight against the volume. For forages and high moisture grains dry matter changes should be checked. The following is an example comparing feeding by weight and by volume for a component-fed herd.

Example Calculations – 60 cow herd (used in both weight and volume-feeding calculations) Weight Feeding

Feed type Cow numbers Times fed As-fed lb. Total weight fed, lb.
Haylage, 40% DM 60 1 /day 24 1,440
Com silage, 36% DM 60 2 feeding /day 47 1,410
Hay, 89% DM 60 2 feeding /day   7 210

Volume Feeding
Assume an 18-bushel cart is used

Haylage – lb./bu. = 20 20 x 18 = 360 lb./cart
1,440/360 = 4 carts fed once/day
Corn silage – lb./bu. = 25 25 x 18 = 450 lb./cart
1,410/450 = 3 carts fed per feeding (6 carts fed/day)
Hay bale weight, lb. = 45 210 lb./feeding/45 = 4.7 bales/feeding (9.3 bales/day)

There is limited research on component feeding and the research available is dated. TMR feeding strategies are the current standard when evaluating feeding management practices. However, there are some basic concepts on feeding sequence and frequency of forages and grains that help mimic a TMR feeding system. The goal is to avoid the excessive peaks and valleys in rumen pH and the associated problems, i.e., acidosis. Some general rules of thumb include:

  1. Feed forage before grain, ideally, dry hay first. If hay is not available, then hay-crop silage.
  2. Energy feeds, like high moisture or dry grains should be fed before a protein supplement or commodity (i.e., soybean meal). Energy feeds can take longer to digest in the rumen.
  3. Protein- and mineral-containing items should be fed close to a feeding of items low in these nutrients such as corn silage.
  4. Avoid slug-feeding concentrates by offering grain several times throughout the day, which should minimize rumen pH dropping much below 5.8 or decrease the amount of time it stays below 5.8.

Robotic Milking Systems

The implementation of robotic milking systems is similar to herds that used computer feeders in the parlor 40–50 years ago. The feeding approach is a PMR formulated for a certain level of milk production and the remaining concentrate fed through a computer in the robotic milking unit while the cow is being milked. The guidelines for component feeding can be applied to robotic milking systems with some minor adjustments.

There are two main types of robotic systems: the guided-flow cow movement approach and the free flow. In the guided-flow arrangement, cows can go to either the robotic milker or the feed bunk area. One-way gates operated by transponders worn by the cows provide access to the areas. Guided-flow barns can be set up allowing cows to be milked before they get their PMR, or they can be milked afterward. In this system, a higher percentage of the nutrients and dry matter is delivered by way of the PMR. Typically, a minimum of 2 lb. of grain per cow per day would come from the computer feeder. The maximum total amount of grain fed per cow per day should follow the guidelines for component-fed herds, which includes the grain in the PMR at the feed bunk, and concentrate fed through the computer. The PMR can be balanced for 10–20 lb. less than the average milk production for the herd.

In a free-flow system, cows can go to all areas of the barn without restrictions. The PMR can be balanced for 10–30 lb. lower than the herd’s average milk production. The amount of concentrate offered through the computer is like the recommendations for the guided-flow system. In both approaches, the concentrate will be in pellet form. It is recommended that the pellets are designed to minimize “fines” since this can deter cows from consuming the programmed amount of grain.

In robotic fed herds, bunk management is critically important to maintaining a proper balance between feed consumed at the robot and feed consumed at the bunk. Animal requirements for physical effective NDF and NDF remain unchanged in robotic systems. Consumption of fibrous materials remains important. Delivery of fresh feed twice daily, frequent push-ups, daily removal of refusals, and appropriate ingredient delivery all factor into the successful feeding of a PMR.

Grazing Herds

Incorporating pasture during the spring, summer, and fall is not unusual for any size of dairy operation. The same principles apply for feeding grain and forage as in component feeding or robotic systems. The main challenge is knowing how much pasture dry matter is available to calculate forage and fiber intakes. Reductions in milk volume, milk fat, and/or body condition are common problems that can occur in the spring. Pasture quality is extremely high, which limits intake of other forages and grains. The rate of passage through the rumen can be fast, which impacts the cow’s energy requirements. This can negatively affect cow performance. During the summer, pasture quantity maybe lacking. Inadequate forage and fiber intake coupled with slug-feeding grain can cause milk fat depression and overall lower animal performance. If ample rainfall occurs in late summer into fall, both quantity and quality of pasture maybe adequate. In drought situations, pasture quality and quantity can be hindered if grasses are outcompeted by weeds, some of which can be toxic. Many options are available for weed control, and recommendations change based on whether lactating or non-lactating animals are present. Reformulating the PMR throughout the grazing season to meet the cow’s energy requirements is recommended.


Pennsylvania’s dairy industry is diverse in size, facilities, and feeding approaches compared to other dairy states across the country. With an average herd size of less than 100 milk cows, feeding a TMR is not always practical. Feeding cows as individuals can result in good herd performance, but it can be labor-intensive. The guidelines used to feed forage and grains can also be applied to a high technical approach such as a robotic milking system, or a low-input system such as grazing. The goal with component feeding or a PMR is to mimic the approach of a TMR by avoiding wide swings in rumen pH that can cause acidosis, milk fat depression, or other performance-related issues.

Author: Virginia Ishler