Dairy Cow Behavior and Nutritional Management; Dr. Trevor DeVries, Guelph

Podcast Topic

This Real Science Exchange podcast episode was recorded during a webinar from Balchem’s Real Science Lecture Series.

Guests:

Dr. Trevor DeVries, University of Guelph

Episode 127: Dairy Cow Behavior and Nutritional Management; Dr. Trevor DeVries, Guelph

Timestamps:

Feeding behavior of dairy cows is inherently tied to their dry matter intake (DMI) which is tied to milk production. If we want to change a cow’s DMI, it must be mediated by changing her feeding behavior. (00:23)

In a multi-variable analysis, Dr. DeVries found that DMI was most associated with feeding time and meal frequency. It’s important to allow the cow to maximize the amount of time she can spend at the bunk eating, as well as the number of times she can get to the bunk each day. In one study, about 30% of the variability in milk fat content in cows on the same diet was explained by their meal frequency, where cows who had more meals per day had higher milk fat. Dr. DeVries also talks about the impacts of feeding behavior on cow efficiency and rumen dynamics. (2:13)

As soon as a cow sorts the TMR put in front of her, she consumes a diet that’s variable in composition to what we expect. Cows who sorted against long feed particles had lower milk fat and milk protein concentrations. In another study, Dr. DeVries retrospectively analyzed cows with a low vs high risk of ruminal acidosis. Cows in both groups had similar DMI but a tendency for high-risk cows to have lower milk yield and numerically lower milk fat. Combining these resulted in significantly lower fat-corrected milk for the high-risk cows. Given that the diets and DMI were similar, the difference was attributed to sorting, which can have quite negative impacts on individual and herd-level production. (10:00)

Cows spend nearly twice as much time ruminating as they do eating. Rumination reduces feed particle size and increases surface area, leading to increased rates of digestion and feed passage. In a recent study, Dr. DeVries’ group calculated the probability that cows were ruminating while lying down using automated monitoring data from previous experiments. Cows with a higher probability of ruminating while lying down had higher DMI, milk fat, and milk protein than cows who ruminated while standing. This highlights that cows need not only time to ruminate but also space for sufficient rest. (16:44)

Diets and diet composition should be formulated to encourage frequent meals, discourage sorting, and stimulate rumination. Forage management factors including forage quality, forage quantity, forage type (dry vs ensiled), and particle size all play important roles. In a study with fresh cows, Dr. DeVries’ lab fed two different particle sizes of straw: 5-8 cm vs 2-3 cm in length. While DMI was the same over the first 28 days of lactation, cows fed the long straw spent more time with rumen pH below 5.8 because they were sorting against the straw. This also resulted in a yield difference, as the short straw-fed cows produced about 165 pounds more milk over the first 28 days compared to the long straw group. Dr. DeVries also comments on the use of feed additives on rumen stability and feeding behavior (22:54)

More frequent feed delivery should generate more consistent consumption and better feeding behavior and improve rumen health and milk component concentration. Shifting feed delivery away from return from milking, while still ensuring cows have abundant feed available, results in more consistent eating patterns. Dr. DeVries emphasizes that we push up feed to make sure it’s present at the bunk, not to stimulate cows to eat. We want to make sure that eating behavior is driven by the cow: when she’s hungry and goes to the bunk, we need to make sure feed is there. (30:02)

Dr. DeVries indicates we want to minimize the time cows are without feed completely. An empty bunk overnight plus a little overcrowding resulted in negative impacts on rumen health, including more acidosis and reduced fiber digestibility. Increased competition in overcrowding scenarios results in cows having larger meals, eating faster, and likely having a larger negative ruminal impact. In another study, every four inches of increased bunk space was associated with about 0.06% greater milk fat. Herds with high de novo fat synthesis were 10 times more likely to have at least 18 inches of bunk space per cow. (40:04)

In closing, Dr. DeVries’ biggest takeaway is that how cows eat is just as important as the nutritional composition of the feed in ensuring cow health, efficiency, and production. Collectively, with good quality feed and good feeding management, we can gain optimal performance from those diets. Dr. DeVries ends by taking questions from the webinar audience. (43:40)

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