The answer is provided by Trevor DeVries, associate professor in the Department of Animal and Poultry Science at the University of Guelph. It is excerpted from his presentation at the 4-State Dairy Nutrition and Management Conference in Dubuque, Iowa, last month.

Q: How can you reduce between-cow intake variations during the transition period?

A: The short answer is: Better bunk management. The long answer is a little more complicated.

Dairy cattle nutrition research has been focused almost exclusively on the nutritional aspects of the diet, and has led to many discoveries and improvements in dairy cattle health and production. Despite many advances in the field of ruminant nutrition, however, we are still faced with the challenge of ensuring adequate dry matter intake (DMI) to maximize production and prevent disease, particularly in the transition period.

Many of the cows that experience reduced DMI in the pre-partum period fail to make a successful transition to the post-partum diet. Research shows that about half of cows have one or more adverse health events during transition, so any practices that can help reduce disease at this time are of significance to the dairy industry.

One of the interesting aspects of transition disease is the individual variability of cow susceptibility. Despite the fact that all animals received similar management and diets, we still face a certain percentage of animals that succumb to disease while others remain healthy.

For example, sub-acute ruminal acidosis is highly variable among cows, despite similar feeding management. There is some data to suggest that this may be in part due to high between-cow DMI variation that can be as high as 30 to 40 percent during the transition period. (This variation drops back to 6 to 10 percent following peak lactation.)

Research also suggests that a 1 percent increase in the variation of DMI during the first 21 days of milk was associated with a 4 percent increase in post-caving incidents (dystocia-related, metabolic or digestive disorders).

Furthermore, research shows that cows diagnosed with acute metritis seven to nine days post-calving consumed less feed and spent less time at the feed bunk during the two-week period before calving. This change occurred nearly three weeks before clinical signs of infection were observed.

Part of the issue is that nutritional models traditionally ignore how diets are actually consumed by cows.

There is an increasingly growing body of literature in which the knowledge of cow behavior can be used to identify bunk-management strategies to reduce the variation in nutrient intake and maximize ration potential. Two main factors are key to success.

First, make sure cows have access to their formulated ration throughout the day. This may mean feeding more frequently than once a day. Research results indicate that cows had more equal access to feed throughout the day when provided feed more frequently. Also, the neutral detergent fiber (NDF) content of the TMR present in the feed bunk increased throughout the day, indicating that feed sorting had occurred — especially when feed was delivered once a day.

Additional studies conducted last year showed that a greater change in ration NDF content over the course of the day was associated with lower feed delivery frequency.

The other key management measure is to reduce feed bunk competition.

Recent observations have shown that at the suggested industry standard of 24-inches of feed bunk space per cow, not all animals can access feed at the same time, because as social animals, cows tend to synchronize their behavior. When feed bunk space is limited, it’s not uncommon to see an increase in aggressive behavior, which is thought to limit the ability of some cows to access feed at times when feeding motivation is high, like when fresh feed is delivered.

Research shows that feed bunk competition dramatically increased the feeding rate at which cows fed at during the day. It was also noted that competitively fed cows have fewer meals per day, which tend to be longer and larger (slug feeding). Studies have also found that competition changed the distribution of DMI over the course of the day, resulting in higher intakes during the later hours after feed deliver. This is when much of the feed sorting had already occurred.

Therefore, increased competition promotes feeding behavior that forces subordinate cows to consumer more of their feed after the dominant cows have sorted the TMR. This likely increases the between-cow variation in composition of TMR consumed and the risk of sub-acute ruminal acidosis.

You’ll get better results if you allow cows to eat when they want and what they need. Keep fresh feed in front of cows and reduce competition.