Feed intake is a major factor that determines the productivity and efficiency of dairy cattle.
Feed intake is a major factor that determines the productivity and efficiency of dairy cattle. Ad libitum access to feed has been a common practice and recommendation in feeding dairy cattle for a long time. Starting prefresh or fresh cows on high energy diets, avoiding wide swings in daily intake, reducing subclinical and preventing clinical acidosis, and maintaining reasonable feed intake for the length of the lactation are all challenges in feeding lactating dairy cattle. Alternative practices may encourage more uniform feed intake, decrease the incidence of digestive setbacks, and increase the margin of profit on dairy farms.
The severity of the problems mentioned above are dependent on the person “reading the bunk” and how that person adjusts the feed a pen of cattle receive on any given day. The reader usually follows some protocol or intuition. This is still an art. Some readers are very good while others seem to always be a little behind or ahead of the cattle.
After a period of consuming high energy diets, feed intake will often decrease and the cows seem to “stall out”, milking poorly or with poor feed efficiency. The result is mediocre performance and high feed cost. When this happens the cows appear to be healthy and in good condition. “Restarting” the rumens on these cows by increasing effective forage in the diet for a period of time will sometimes reestablish a higher intake.
Several different intake management systems are used for finishing cattle in the feedlot (Preston, Peters, Bartle). These systems are known by several different names and are variations on ways to enhance feed efficiency and profitability in feedlot cattle. The same principles apply to dairy cattle. The challenge with feeding dairy cattle is the variability of production and feed intake within a group. Milk producers manage a flow of animals through a pen. In feedlots, finishing cattle within a pen are started the same on a given day. The pen is managed as “all-in, all-out”. Even with these differences, there is still a lot that can be learned from bunk management of finishing cattle on very high starch diets.
The goal of any alternative intake strategy is efficient milk production and profitability not maximum intake. In other words the ultimate goal is to give cows all the fresh feed they will eat but not one bite more. Many nutritionists have stated that the last bite of feed has the greatest margin for profitability because maintenance costs have already been paid. This may be true, but at what cost should that last bite of feed be chased. The cost of strategies used on most dairies to chase that last bite of feed is astronomical and creates inefficiencies and lost profits. Maximizing profitable feed intake is all about precision bunk management.
When ad libitum intake is not practiced, rate of passage, site of digestion and extent of digestion will change. This changes the whole dynamics of balancing rations and feeding cows. A less than ad libitum intake system may not work on all cattle or in all situations. It requires more management ability and attention to detail. But the potential returns are much higher. More research needs to be done with these strategies in relation to lactating cows.
Program feeding or limited maximum intake are similar systems of controlling intake. By definition, program feeding or limited maximum intake is using intake prediction equations to regulate consistent daily dry matter intakes. The objective is to maximize dry matter intake over an entire lactation. By contrast, ad libitum bunk management maximizes feed intake on a daily basis without regard for the entire lactation period. With program feeding there is less daily overfeeding and feed efficiency is maximized because of consistent daily feed deliveries over the entire lactation. A large degree of bunk management is still involved when program feeding.
By controlling upper intake levels, cattle seldom exhibit the large downward spike of dry matter intake often observed with an ad libitum intake feeding program.
Comparison of performance of beef cattle on ad libitum and program feeding feedlot systems (Peters)
|Initial weight, kg
|Final weight, kg
|Daily gain, kg
|Daily dry matter intake, kg
|Initial weight, kg
|Final weight, kg
|Daily gain, kg
|Daily dry matter intake, kg
On the other hand, feed bunk management and bunk space can be major obstacles to successful implementation of controlled intake feeding systems.
Bunk management costs little more than a few minutes each day, but has a very significant impact on production costs. Diets almost always look right on paper and management is often “by the book” but some herds still experience low intakes, poor milk production and high feed costs. Fingers get pointed and the problem often goes unresolved.
Good bunk management is essential in efficient production of milk. It relies on the “eye of the master” and is the root of many disappointing production levels. Milk producers and nutritionists use forages and dry hay as surrogate bunk managers. The forages help fill cattle, prevent over consumption and stabilize fermentation.
Cattle are self-propelled fermentation vats that like everything constant. Staying constant means providing a consistent diet in consistent amounts at consistent times. Variation is the number one enemy of all fermentation systems; cows are no exception.
Feedlot cattle are fed very high starch levels. Bunk management becomes very critical when very little forage is fed to cover any mistakes in the bunk. There is very little margin for error in feeding feedlot cattle. We can learn much from them.
One researcher split a single lot of cattle into two different feedlots but fed them the same diet (Pritchard). One feedlot (B) was managed by an “experienced midwestern cattle feeder”. The basic premise was that to feed cattle, simply keep the bunks full at all times. The other feedlot (A) managed on the principle that feed deliveries should match cattle appetites. In figure 1 are the resulting feed deliveries for the two pens.
Table 2. Performance of cattle in Lots A and B.
||Dry Matter Intake
||Average Daily Gain
Feed deliveries were the same for both lots, but average daily gain and feed/gain were very different. The only difference was the way the feed bunk was managed. There is no data that I know of to demonstrate this same phenomena in lactating dairy cattle. But it seems to reason that the same principle holds true. Erratic intakes lead to feed wastage, digestive upsets, and increased costs. The solution is simply bunk management and only requires a few minutes every day.
Poor bunk management is very hard to recognize and objectively evaluate without a very good data set of consistent bunk scores, dry matter intakes and a record of other events that influence dry matter intake. Good bunk management takes practice. A good understanding of what is going on is very useful. There are 3 things that are important to remember
- cows are mobile fermentation vats
- cows do not know how much to eat
- it often takes 2-3 days for a mistake to show up
Delivery of feed needs to be very consistent. In one report, one group of steers were fed ad libitum and another group received feed deliveries that either increased or decreased 10% each day (Pritchard). By design, both groups were fed the same total amount of feed during the feeding period. Only the consistency in delivery was different. The results are in Table 3.
Table 3. Effect of cycling feed deliveries on feedlot performance.
||+ 10 %
|Average daily gain
|Dry matter intake
|a,b Means differ (p<0.10)
The effects of erratic feed delivery are dramatic in feedlot steers. I suggest that the same effect occurs in lactating dairy cattle. The effect would be more dramatic in early lactation and fresh cows. These cows experience many changes at the same time.
The accuracy of feed ingredients is also very important. This is important in controlling feed costs and providing consistent amounts and consistent mixes to maintain the mobile fermentation vat. A group of heifers were sorted into two groups (Pritchard). The feed was weighed and mixed before feeding to the “high management group”. In the “low management” group, feed amounts were estimated using an end loader and buckets. The results are in Table 4.
Performance was significantly reduced by 10% when feed ingredients going into a mix were estimated and not weighed. Inaccuracies in weighing ingredients is a costly mistake.
Table 4. Effect of high and low management of feed on heifer performance.
|Initial weight, lb.
|Average daily gain, lb. b
|Dry matter intake, lb. per day
|b Treatment effect (P,0.05)
To make feed calls, a manager or feeder needs to know how much the cows have been consuming and how much is left in the bunk (bunk score)
Let’s assume a healthy set of high producing cows and well balanced diet. The first feed bunk is empty, a “slick” bunk. How much feed should be unloaded? Since the bunk is empty, obviously a little more than yesterday should be fed. The feeder tries to remember what was fed yesterday and delivers 5% more feed. The feed bunk in the next pen is in the same condition so 5% more feed is fed. The third pen feed bunk is half full. Feed delivery is reduced by 50%. The next day the first two pen feed bunks are half full and the third pen feed bunk is “slick”. The same process of adjusting deliveries is made. Feed deliveries in this scenario are erratic and the producer can expect high feed costs and mediocre production.
Why did the first two pens back off feed? They could have been bumped 5% the day before and the second bump of 5% made a total adjustment of 10%. This resulted in overfeeding the cows and then over compensating in reducing feed deliveries creating a cyclic or erratic feed intake. The same thing is happening in the third pen only the cycle is one or two days off from the first two pens.
To prevent this from happening amount of feed delivered to each pen and bunk scores should be recorded daily. One person should be responsible for making daily feed calls. This person should score the bunks and call feed at the same time every day. It is very important that it be done at the same time every day. The best time is before the first feeding of the day. At least 4 days of bunk scores and feed deliveries should be carried on person when making feed calls. This will indicate to the feed caller that intakes are going up or down or holding steady.
In the above scenario, if 12,600 lb. of feed were delivered yesterday and the bunk scores a 2 (about 1200 lb. of feed left in the feed bunk), the cows probably only ate 11,400 lb. of feed. Obviously today’s delivery needs to be cut back. It could be cut back to 11,400 lb. dd this to what is already in the feed bunk and the total is still at 12,600 lb. If the cows only ate 11,400 lb. yesterday they are not going to eat 12,600 lb. today. Today’s delivery will probably need to be reduced to 10,200 lb. (10,200 + 1,200 = 11,400) and then gradually worked back up to where it should be.
It is very important to look at the cows when making feed calls. If the bunk is “slick”, do the cows look hungry or are they content? If they look content then wait a second or third day before increasing feed delivery. There is a fine line between overfeeding and maximum dry matter intake. A cool night may cause a temporary increase in intake that is not sustainable. Bumping feed delivery may cause overfeeding. Occasionally letting cows clean up or “slick” a bunk does not hurt overall dry matter intake or production as much as the valleys and peaks from erratic feed deliveries. Remember the focus is not to maximize daily intake of feed but to maximize feed intake for the entire lactation period.
Feed in the feed bunk should be examined at every feed call. Not all bad bunk scores are the result of bad feed calls. Hot weather may cause the cows to back off feed or cause the high moisture ingredients to spoil creating an unpalatable feed. A broken or malfunctioning water fountain may be the cause of reduced intakes. Weekend, relief or new feeders may have incorrectly mixed feed or have been in a hurry and not paid attention to detail. Mechanical problems with the mixer may create problems. The person making the feed calls must examine the feed to detect these problems and allow for them in making the feed call.
Precision bunk management can make such a large difference in profitability and requires such a small investment, that it is amazing why so many professionals and producers ignore it. It is much more than common sense. The key is to use records to be consistent, watch cows and feed the diet as formulated.
Bartle S.J. and R.L. Preston. 1992. Roughage level and limited maximum intake regimens for feedlot steers. J. Anim. Sci. 70:3293.
Pritchard, R.H. 1993. Bunk Management is crucial component of beef production. Feedstuffs, April 19. Page 14.
Peters, T.M. 1995. Arguing for controlled intake. Feed Management, Vol. 46, No. 8, Page 14.