Keys To Milk Quality
As described previously, dry period management is a current research focus for mastitis scientists. Ways to fine-tune feeding, promote cow comfort and well-being, and otherwise manage the dry period to minimize new mastitis infections and maximize cure rate of existing mastitis infections are being re-investigated under current farm conditions. This is the last article to focus specifically on dry-off methods and describes findings from some of the recent research.
Survey of Existing Dry-Off Methods
Until 2010, no published surveys were done to see how producers manage cow Dry-Offs. A survey by Rajala-Schultz and co-workers at Ohio State found that only 18% of dairies (69 of 385 farms) considered milk production of individual cows in their Dry-Off decisions. Eighty-eight percent said that expected calving date was the only criteria used to determine time to Dry-Off cows. When asked about specific Dry-Off decisions, 20% of dairies reported decreasing ration energy level as an aid to Dry-Off and dry period mastitis control. Seventy-two percent of dairies reported using abrupt Dry-Off method instead of intermittent Dry-Off method. Only twenty percent of dairies milked cows 1-time per day before Dry-Off. The survey also found that larger dairies appeared to use abrupt Dry-Off more often and dried cows off at higher milk production than smaller herds. The reasons for decisions associated with Dry-Off were not studied. The findings indicate that few herd managers, especially on larger dairies, Dried-Off cows intermittently or decreased ration energy level before Dry-Off. The survey also indicates that calving date was the main criteria used by most dairies when determining date to Dry-Off cows.
Informal mastitis risk assessments in south central Pennsylvania of 200 dairies from 2008 to 2012 agree with these findings. With the exception of a few dairies with less than 100 cows, few herds indicated milking cows intermittently before Dry-Off or decreasing energy density of the ration for the week before calving. In dairies using intermittent Dry-Off, the method was only used for select cows with high milk production, or a history of leaking milk, and not as a whole herd strategy to reduce new infection risk in the early dry period. Although not a formal study, abrupt Dry-Off appears to be most popular as an across herd strategy in Pennsylvania and agrees with survey findings from Ohio State.
So why is abrupt Dry-Off used on most dairies despite research indicating a positive benefit from reducing production in the last week of lactation? I can guess but don’t know for sure. Because of changes to dry period management practices following the original research, additional studies are needed to evaluate the benefits of intermittent Dry-Off compared with abrupt Dry-Off on new infection rates in the early dry-period.
New & On-Going Studies
A large project with several individual studies is currently on-going at Ohio State. Project findings should provide improved best management practices for Dry-Off. Variations in procedures, facilities, and cows will help to develop best methods on individual dairies to reduce new mastitis infections between dry-off and calving. For intermittent Dry-Off to be economically justified, it must provide economic benefit to compensate for additional labor requirements. Economic merit will likely vary by farm and will take longer to prove.
A herd study was reported in 2005 by Rajala-Schultz and co-workers at Ohio State and re-examined the effect of Dry-Off method – abrupt versus intermittent on new mastitis infections. Researchers studied 112 Dry-Offs at a single dairy to evaluate the impact of dry-off method. Cows were Holstein or Jersey and were seasonally grazed. Housing was the same before and after Dry-off. The 56 cows Dried-Off abruptly were housed in tie-stalls in the first year and Free-stalls in the second-year of the study due to management changes at the dairy. The 56 cows Dried-Off intermittently were housed in Free-stalls. Ration changes were not made before Dry-Off so only milking frequency was evaluated. All other conditions were similar between treatment groups so that only Dry-Off method could be evaluated. Bacterial cultures and somatic cell count (SCC) tests on cow and quarter milk samples, collected 3-days after calving, were used to determine impact of Dry-Off method.
Researchers found that higher milk production was associated with risk for new environmental mastitis infections. For every 11-pound increase in milk production above 27.5 pounds, the odds of a cow having an environmental mastitis infection increased by 77%. There did not appear to be an increased risk of a cow having a Staph species infection at calving when milk production was higher at Dry-Off. When only cows with environmental mastitis infections were included in the analysis, cows with higher milk production at Dry-Off had 2.13-times greater odds of having an environmental mastitis infection compared with cows with lower milk production. Results suggested that increasing milk production at Dry-Off is an important factor affecting environmental mastitis level at calving.
A 2010 study by Rajala-Schultz and co-workers offers some confusion to answering the best Dry-Off method question. Similar to the previous study, Dry-Off method was evaluated in 112 Holstein and Jersey cows in a single herd. The purpose of this study was to evaluate the influence of milk production and infection status between cows Dried-Off intermittently or abruptly.
Researchers found that the intermittent method was effective at reducing milk production level at Dry-Off compared with abrupt Dry-Off. In addition, quarters not infected before Dry-Off and producing more cumulative milk the week before Dry-Off had a greater chance of a new mastitis infection when evaluated at calving. Uninfected quarters from cows producing 36-pounds of milk per day over the last week before dry-off had significantly higher odds (7.05-times) of being infected compared with cows milking less than 23-pounds per day. The confusing portion of the study is that when both infected and non-infected quarters before Dry-Off were included in the analysis, Dry-Off method and milk yield at the end of lactation were not significantly associated with mastitis status at calving.
The latest research by Rajala-Schultz’s team took a novel approach to investigating Dry-Off methods. The team evaluated impact of abrupt Dry-Off on cow lying behavior immediately following Dry-Off. They expected cows Dried-Off abruptly would increase activity and decrease lying time of cows immediately after Dry-Off. They also expected that milk production level at Dry-Off would be partially responsible for change in lying behavior patterns. Eighteen cows were evaluated in three dairies in the summer of 2011. Activity sensors on cows’ hind legs 7-days before Dry-Off through 7-Days following Dry-Off were used to study lying behavior.
Researchers found that cows changed their lying habits following Dry-Off and there was substantial variation between herds. Across herds, standing time increased significantly and lying time decreased significantly following Dry-Off. Milk production level and lactation number were not significantly associated with lying behavior. Because number of study cows was small, this finding may be contested in future studies with more cows and greater variation in milk at Dry-Off. Herd differences in lying behavior after Dry-Off were attributed to likely housing and management differences. Although number of cows and especially number of herds was much too small to be conclusive, there was a statistically higher activity level and less lying time in barn-housed cows compared with cows on pasture all day following dry-off. Despite statistical significance, without more herds and cows within herd no conclusions can be drawn between the interaction of housing type and Dry-Off method on lying behavior. It will be very interesting however, to see future research findings and best methods that may be adopted to reduce new infection risk in the early dry-period while maintaining comfort of cows in this critical time period.
Article Highlights
- Milk production level appears to impact risk for new environmental mastitis infections following Dry-Off. Higher production is associated with increased risk of new mastitis infections in the early dry period and infections likely persist into early lactation.
- Intermittent milking before Dry-Off is effective at reducing milk production level at Dry-Off.
- Abrupt Dry-Off changes lying behavior of cows following Dry-Off and likely increases cow activity, while decreases lying time. Differences in housing and management practices within herd will likely affect importance to individual dairies.
- Intermittent Dry-Off may be a useful best management practice in herds with higher milk production and cows with higher production at Dry-Off to reduce new infection risk for environmental mastitis.
- Complete impact of Intermittent compared with Abrupt Dry-Off, including economic viability is not known at this time.
