It’s all about consistent feed intake and maintenance of rumen health for dairy cows in the transition period before calving.
There was a time when producers believed a drop in feed intake in the high-straw diet was a natural process for cows in the days or weeks before calving, said Trevor DeVries, a professor and Canada research chair in dairy behaviour at the University of Guelph.
Subsequent research has shown a consistent feed intake and energy balance keeps the cow in condition and the rumen better prepared for the ration given during lactation.
“We know that those issues that dairy cows faced in early lactation are going to have longer negative impacts on those animals, specifically in terms of their milk production but also their chances of being re-bred and coming back into a next lactation and/or being culled,” DeVries said during a presentation at the Western Canadian Dairy Seminar.
Disease in early lactation continues to be a challenge on Canadian dairy farms and these are related to body condition and feed intake during the dry period. A controlled energy diet for dry cows can help address this problem, DeVries said.
“If we can control energy consumption, we can control body condition gain, keep those animals in a steady state of condition throughout the dry period … then do so with a diet that’s also going to promote a lot of bulk intake.”
Dry cow diets are typically bulky and low in moisture. A coarse feed allows the cows to sort through it more easily so nutrient intake is inconsistent and variable among animals.
Lactating cows are typically given a more finely chopped ration that has more moisture and is consumed more quickly.
DeVries and his team examined the impact of straw particle size and found that dry cow diets on many farms had chop lengths of 10 centimetres or more. This makes it easily sortable by the cows.
When comparing that length of chop to one with two to three cm lengths, they found a major difference.
“Simply by reducing chop length … that was having a big impact on the overall consistency in the diet that was being consumed by those cows,” he said.
Cows given a ration with shorter chop length had higher intake throughout the dry period than those given a longer chop.
Cows that consumed the shorter-straw length also had better rumen health, indicated by pH in early post-partum, he added.
Cows given the longer straw reduced their intake before calving, a risk factor for their health post-calving.
The study thus indicated that dry cow rations should be physically similar to those fed during lactation.
Adding water to the dry cow ration can also limit sorting and improve intake, DeVries said. In his studies, adding water resulted in more consistent consumption. The cows ate more throughout the dry period and continued the same level of intake in the post-calving period.
He offered a caution about adding water, particularly in summer when humidity is high. Those conditions promote spoilage so feed should include good quality forage, ideally provided more than once a day and with good bunk management to keep feed pushed up.
Adding molasses to the dry cow diet increased feed intake and kept it consistent leading up to calving and in the post-calving period, the study showed.
DeVries also noted the importance of adequate bunk space — at least 75 cm per cow — so animals don’t have to compete for an adequate amount of feed.