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Reducing variability of dry matter intake for dairy cows

Dairy Corner: Several factors, including particle size, can affect how dairy cows eat

Optimizing dry matter intake (DMI) of a well-balanced dairy cow diet should be one of the mission statements of every dairy producer. It is the key to providing enough essential nutrients that support good milk production (and its components) in feed that cows can reasonably consume every day. Unfortunately, daily DMI among a lactating cow herd is not always consistent as we would like it to be. Therefore, it is important to set up a strategy to improve dry matter intake.

Whenever I visit a dairy farm with DMI variation, I usually have a checklist of questions concerning lactating cow DMI in my head. Most fall into two categories — either animal- or feed-related (though sometimes, environment plays a role in affecting DMI, such in cases of hot weather and heat stress).

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Otherwise, I stick to a loose script and I look at the animal- or cow-related DMI factors first. These include the number of cows that go up to the feed bunk to eat, the number of mature and first-calf heifers, a general sense of body condition scores in the milking cow herd, the number of cows chewing their cud, manure consistency, any lame cows and cow comfort. I also include a look for abnormal eating behaviours such as individuals trying to sort their bunk ration or any sign of subclinical acidosis amongst the same cows.

When looking at feed-related DMI factors on any given barn tour, I always grab a handful of TMR to see if it is well-mixed, its squeezable moisture content, if it contains lots of effective forage fibre and if it smells good. I also watch for any visible mould in my handful of dairy feed. Then I look along the feed bunk and see if this feed is consistent and how it is pushed up for easy access. I also look at the placement and cleanliness of the water troughs in the same lactation barn.

Intake up or down?

I had a recent chance to put my checklist into practice at a 200-milking cow dairy. The owner told me that DMI of his herd varied periodically (+/- two kg per average cow, dm daily) during the last few months. It took me about 30 minutes to conduct a walk of the lactation free-stall barn a couple of hours after milking that afternoon. The producer walked with me and we discussed my initial observations of the dairy cows. I took my TMR sample that was unloaded on a concrete floor along a row of headgates. According to the producer, milk yield bounced along with the variations in DMI, but milkfat did not change at all.

During my barn walk, I found that nothing stood out of place, especially given the overall body condition and eating behaviour of the cows. About one-third of this dairy herd was eating at the bunk and enjoying a TMR meal that consisted of moist reconstituted chopped alfalfa hay, a grain mill mix and added palm fat. Some cows were trying to sort their dairy diet, but most were eating it in a steam-shovel manner. Otherwise, the remainder of the herd were lying in their stalls and chewing their cud in a relaxed manner. There were no apparent lame cows and only one or two were found to be under-conditioned. We did not visit the dry cow pens.

In this case study, the only thing I found that might contribute to the dry matter variations was that my hand-held TMR sample consisted of either very short leaves/grain concentrate or hard alfalfa stems of one to two inches long. If we were to do a Penn State Particle Separator test on it I suspect the top screen would contain 20-25 per cent, with 50-60 per cent in the bottom screen and a deficiency of particles in the middle. These cows might be lacking important middle-screen fibre (recommended at 30-50 per cent) needed to optimize efficient forage digestion by the rumen bugs and thus might explain this herd’s DMI variations.

I advised this producer that he should check the condition of his mixer (knives) and mixing time (three to four minutes) when making up his next daily TMR lactation diet. It was the best practical solution that offered quick corrective action to hopefully reduce the variability of dry matter intake.

About the author

Columnist

Peter Vitti is an independent livestock nutritionist and consultant based in Winnipeg. To reach him call 204-254-7497 or by email at [email protected]

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