A stable group close-up dry cow management strategy—Did it affect cow behavior?
The annual Dairy Science Association meetings were held in Phoenix, Arizona in July. These meetings are an opportunity to learn what many dairy researchers around the world are investigating. My graduate student Karen Lobeck and I worked with Ricardo Chebel and his student Paula Basso Silva to investigate the effect of a close-up dry cow management strategy on behavior, health and performance of dairy cows. We also determined social rank in close-up cows and investigated if social rank was associated with health, reproduction, and milk yield and milk components during the first 100 days in milk (DIM). Results of the studies were presented by Karen and Paula at the Dairy Science Association annual meetings.
It has been suggested that cow movement and regrouping during the close-up dry period may affect performance and health in the upcoming lactation. Addition of new cows to a group can cause social turmoil and the resulting stress could affect cows in a negative manner. A study in Canada showed that when lactating cows were regrouped, there was a loss of about 8 pounds of milk the day of regrouping and an increase on the number of displacements from the feed bunk within the pen for 2 days after regrouping. Displacements were defined as physical contact initiated by one cow causing the receiving cow to stop feeding, back out, and entirely remove her head from the headlock. This was an indication of an increase in aggressive interactions between cows as they established a new hierarchy within the group.
Another study showed that cows moved into a new pen were displaced 2 times more than cows that stayed in their regular pen and had a 9% reduction in feed intake. These two studies used lactating cows, not dry cows. A study in Wisconsin investigated the effect of having a dynamic (twice a week entrance of new cows) or stable group of close-up dry cows. They found no differences between the two treatments in number of displacements, dry matter intake, non-esterified fatty acid concentrations and milk production.
These previous studies used pens with a small number of cows (12 or less) and we wanted to investigate the effect of a more stable dry cow group in pens with 44 cows, where social interactions could be more prevalent. We limited the stocking density to 90% of available headlocks, so cows were not overcrowded. Our study included 226 Jersey cows that were in their 2nd or greater lactation. They were housed in sand-bedded, 2-row pens. Using video cameras, we monitored feeding behavior (time spent eating per day) and displacements from the feed bunk for 5 weeks per replicate. Displacements from the feed bunk are an example of aggressive social interaction between cows so we also used displacements to categorize cows into low ranking, middle ranking and high ranking depending on how many displacements they were the actor or the reactor. More dominant cows would be placed in the high ranking category, indicating that they displaced more cows than being displaced by other cows. One study suggested that displacements may predict disease because 2 weeks before calving, healthy cows displaced other cows 16.8 times per day whereas severely metritic cows displaced other cows 12.2 times per day.
Our treatment strategies were conventional (weekly entrance of new cows to keep constant stocking density) or all-in all-out (stable group formed about 4 weeks prior to expected calving date, with no entrance of new cows to the group for up to 5 weeks). As cows calved, the number of cows in the pen changed in the all-in all-out group, especially after 3 weeks. Displacements from the feed bunk were 2 times greater in the conventional treatment since new cows were added once a week creating social disruption (see graph; AIAO=All-in All-out and CON=Conventional, weekly entrance of cows). Feeding time was similar between the two treatments and averaged ~4.3 hours per cow per day.
In collaboration with Ricardo Chebel and Paula Basso Silva, we also investigated if social rank was associated with health, reproduction, and milk yield and milk components during the first 100 DIM. For this study, we used 190 2nd and greater lactation Jersey cows. There were no differences in mastitis, metritis, retained placenta, lameness or death risk among social rank. Middle ranking cows were 3 times more likely to become pregnant after 1st service compared to both low and high ranking cows. Are those cows more 'neutral' to social disruptions in the pen? 'Cool and collected'? There were no differences in body condition scores, non-esterified fatty acid concentrations, or milk yield, milk protein percentage or somatic cell count until 100 DIM. In conclusion, social rank during the close-up dry period was not useful to identify cows at risk for disease events or to predict milk yield in subsequent lactation.
Published in Dairy Star August 11, 2012