Total Mixed Rations for Dairy Cattle

July, 1991 - Issue 91.3
Livestock Nutrition
Murray Snowdon, Livestock Nutritionist

Feeding total mixed rations (TMRs) to dairy cattle is certainly not a new concept. TMRs have been fed for many years but recently there seems to be a greater interest in TMRs than ever before. This recent increase in popularity is somewhat regional but it seems that most areas of North America are seeing an increase in the use of TMRs.

TMRs are widely used in areas of the U.S. where large herd sizes are common. With large herds of production-grouped cows, often fed from bunk silos, TMR feeding becomes an obvious choice based on economics and practicality.

TMRs have been promoted in areas where both corn silage and haylage are fed since TMR feeding prevents individual cows from expressing a preference for one forage over another.

TMRs are used extensively in areas where seasonal calving is still common. With all cows at the same stage of lactation, the TMR for the whole herd can simply be adjusted as lactation progresses and grouping is not necessary.

Private consultants often promote TMRs in part because a TMR eliminates most commercial feeds from the ration making the farmer a better candidate for nutrition consulting services. A TMR also makes "commodity" and byproduct purchases more feasible, allowing the nutrition consultant to look at more ration options and make purchases on behalf of his client. A nutrition consultant who makes good purchasing and feeding decisions for a farmer can form an integral part of a successful TMR feeding system.

TMRs have also gained popularity because Wisconsin's highest production herds are feeding TMRs. This observation might seem conclusive at first glance, but a recent Illinois summary showed a wide variety of feeding systems in their high production herds. Only 2 out of 9 surveyed in Illinois were feeding TMRs compared to 7 out of 8 in the most recent Wisconsin summary. Production levels in the two state surveys were similar when adjusted for 3x milking. It appears that high production can be obtained under many different feeding systems and a move to TMR should not be made solely for milk production potential.

Although TMRs make the most sense in larger free-stall herds TMRs have been successfully adopted in herds of every type and size and the list of potential advantages makes them at least worthy of consideration for most herds.

POTENTIAL ADVANTAGES

(1) Of all feeding systems, a TMR most readily delivers a balanced ration to the cow, minimizing the difference between the ration as it appears "on-paper" and the ration that is actually consumed. In most other feeding systems the unknown of individual cow forage intake makes true ration balancing difficult. The delivery of a uniform TMR ensures that every bite consumed by the cow is the same, and is one of the strongest arguments in favour of TMRs.

(2) A TMR ensures a fixed ratio of forage:grain and also ensures that when two different forages are fed they will be consumed in the desired ratio.

(3) By providing an appropriate and consistent forage:grain ratio for early lactation cows, the management requirements of getting fresh cows onto full feed is simplified.

(4) A TMR results in a more uniform rumen pH than a feeding system that offers concentrates in meals. This helps to maintain milk fat test and also tends to improve feed efficiency and feed intake.

(5) Feeds such as fats or animal byproducts, routinely used in high production herds can present difficulties in traditional feeding systems due to their poor palatability but are easily fed in TMR system.

(6) Byproduct feeds such as wet brewer's grains that may be impractical to use in more traditional systems often fit into a TMR system quite readily.

(7) Offering a TMR to cows in a free-stall barn results in cows standing less and resting more. Cows travel to one location to eat and have access to feed at all times. The extra time travelling to two feed sources - a bunk and a computer feeder - is eliminated and time spent waiting at a computer feeder is also eliminated.

(8) Since a TMR system eliminates the need for a commercially prepared dairy ration, a farmer switching to a TMR will automatically reap any benefits of a grain storage and milling system.

(9) A farmer feeding a TMR is more likely to analyze feeds and balance rations on a regular basis. This improves the chances of increasing milk production and income over feed cost.

POTENTIAL DISADVANTAGES

(1) A factor that kept many farmers from adopting the TMR system was the general recommendation that cows be divided into at least two milking groups. In fact, in years past, many felt that three groups were required. This aspect of a TMR discouraged many producers from giving TMR much further thought. Today, specialists are more open-minded on this aspect of TMRs and would consider all of the following as possibilities, depending upon the individual farm involved:

(a) A three-group TMR is still sometimes recommended but is less popular. In many cases, the third group is for 1st-calf heifers.

(b) A two-group TMR is likely the most common in terms of use and recommendation. Again, the split may be based on mature versus 1st-calf heifers rather than on production level.

(c) One-group TMRs are now common. This approach can be successful in well-managed, high production herds where over-conditioning due to either low milk production or lengthy days open does not become a problem.

(d) Producers who are now using computer feeders may choose to use a one-group TMR, with the computer feeder reserved for high producing cows.

With this wide range of options now accepted and proven successful, the grouping aspect of TMRs is not necessarily the stumbling block that it was in the past.

(2) One of the most often cited disadvantages of a TMR is the milk production drop seen when cows are switched from one group to another. The extent of this problem will depend upon barn design - how different is one group's facilities from the other? upon number of cows switched at a time - switching small numbers is more stressful than larger groups, upon ration difference from group to group - more than a 15 percent drop in energy content may cause problems, and the reason for moving the cow - if the cow is being moved strictly for space reasons but has not met an appropriate milk production or body condition criteria, then a production drop can be expected.

(3) On farms where forage quality is poor and refusals and significant feedbunk cleanout is common, one must bear in mind that on a TMR program this discarded feed will contain many high priced components in addition to the forage.

(4) Generally speaking, feeding a TMR is more time consuming than many other feeding systems. Someone must be present while ingredients for each group are weighed and mixed. This extra time requirement is partially offset since a TMR is usually fed only 2 times per day, in contrast to other feeding systems where multiple feedings are common.

(5) Much of what is written about dairy cattle nutrition is directed towards the individual cow. This includes reference to cow size, body condition, milk fat and protein test, an individual cow's ability to eat concentrate and of course milk production itself. The TMR system does not cater to any of these factors on an individual cow basis and some would argue against TMR on this basis. The TMR system, by design, must deal with cows on a group basis rather than an individual cow basis.

With group feeding, individual adjustments in a cow's diets for reasons such as sickness, poor body condition or boosting an individual's BCA may no longer be possible.

Producers who have a TMR coupled with locking headgates or a computer feeder can cheat the TMR system and still give individual cow attention.

(6) Targeting of nutrients to individual cows is not as efficient in a TMR system. Depending upon the grouping system used, high priced ingredients such as rumen-protected fats or by-pass protein may be fed to cows who don't require them.

(7) The inability to incorporate hay into a TMR was once seen as a problem but many TMR mixers are now capable of handling hay.

(8) A TMR program cannot be used when cattle are on pasture, thus limiting its usefulness in herds where pasture is still an important ration component.

(9) Feed analysis and ration balancing become even more important in a TMR system. Farmers who don't carry out these tasks on a regular basis will not get best results. The dry matter level of the silage in the TMR is the most variable and most likely to introduce major errors into the ration if not routinely measured and adjusted for.

(10) Because one TMR mix is fed to a large number of cows, an error in calculation, weighing or mixing can have a much larger effect on milk production than in other feeding systems where errors are more likely to apply to individual cows.

MAKING A TMR WORK

The one rule above all others in successfully feeding a TMR is that the moisture content of the silages being fed must be routinely monitored and the ration adjusted accordingly.

For example, a TMR may originally be formulated to contain 10 kg of silage dry matter per cow. If the silage analysis indicates a dry matter level of 50% then each cow would be fed 20 kg of wet silage per day. If the silage further down in the silo contains only 30% dry matter and no adjustment is made, then the 20 kg of wet silage would now contain only 6 kg of dry matter rather than the 10 kg formulated for. This results in a 40% reduction in forage and a dramatic change in the forage:concentrate ratio. This shows how crucial on farm moisture testing is to the success of a TMR system.

Regular lab analysis of TMR components, especially the forage, is necessary if the use of nutritional safety margins are to be minimized and if income-over feed cost is to be maximized.

Although TMRs have been fed without the benefit of scales, one can't expect anything but disappointing results from this approach. Accurate weighing of all dietary components is one of the cornerstones of a TMR feeding system.

To maximize dry matter intake and production, feedbunks should not be left empty for more than 2-3 hours per day.

TMRs that contain less than 50% dry matter may depress intake. Care should be taken to stay above this limit particularly in TMRs formulated for a high production group. A ration that is too wet is most likely to occur when high moisture grains and/or a wet byproduct feed is being fed.

There are no hard and fast rules regarding the production level that should be used as the balancing point for TMR formulation. Table 1 contains adjustment factors suggested by Virginia State University. For example, if half of the cows are in group 1 and half are in group 2 (50:0:50), then the recommended balancing point for the high group would be 1.17 times the group average and the balancing point for the low group 1.23 times that group's average production.

CAPITAL COSTS INVOLVED

Since most farmers would be modifying their present system to incorporate a TMR, setup costs will vary widely, but for most herds the cost of a TMR system will be similar to many of the other popular options that might be considered.

For example, if a farmer in a tie-stall barn selects a rail-mounted, multi-compartment grain feeder and chooses to buy whole grains and process them on the farm he will require most of the same equipment as the TMR system. The following items would be common to both systems - silage cart or belt feeder, supplement tank, 1 or 2 flat bottom grain tanks and a roller mill. The price difference between the systems, if any, will arise between the cost for the TMR mixer with scales ($10-15,000) and the around-the-barn feeder ($15-30,000).

In a free-stall herd with horizontal silos, a portable mixer wagon ($20-25,000) can serve to deliver both grain and silage to the herd and can form the basis for a TMR system. The same herd would have the option of installing a computer feeder ($20-25,000) and using another method (tractor and bucket, for example), to deliver the silage.

In a free-stall herd with upright silos, a belt feeder or silage cart will be required in either system and the price comparison comes between a stationary mixer with scales ($10-15,000) and a computerized grain feeding system ($20-30,000).

It appears that the average cost of a TMR system is in the same realm as other options with considerable cost overlap when one considers the top and the bottom price of each system. The cost ranking of a TMR system will vary considerably from farm to farm.Most TMR systems incorporate home milling of grains. This automatically incurs a significant cost but also brings any financial advantage and dollar payback that might be expected from home milling.

CONCLUSIONS

Despite our search for "the" best way to feed cows, we have yet to define it. The TMR system has many potential advantages and warrants consideration by any farmer anticipating a change in his feeding system. In most herds it will not be labour saving, but does offer potential improvements in feed efficiency and animal health, and based on experience elsewhere it does as well as any other system in achieving the genetic potential of the herd.

Table 1 Adjustment Factors for TMR Formulation*

* Multiply group's average production by the appropriate factor to determine balancing point.