During the past few years, there has been a noticeable increase in publication of applied cow behavior research. Presently, many of the most active research groups in dairy cattle behavior are located in Europe and Canada. We need more dedicated research effort in the United States on applied behavior, and greater collaborative efforts, with a goal of developing decision support tools that assist the producer and consultant in making profitable decisions by accurately modeling behavioral responses to facilities and management and associated changes in cow and herd performance.
We need to differentiate between individual cow behavioral response to a management routine and the economic return for adopting a management routine on a whole-herd basis. Most research has focused on cow response, but a comprehensively useful decision tool needs to consider herd response (as the integration of multiple pen responses) and the impact of stocking density on long- term enterprise profitability.
An appropriate research target should be how to achieve the point of inflection where economic return to the dairy is optimized. We can surmise the optimal stocking density might vary among farms, and consequently “an optimal stocking density” can never be determined. But we can identify the primary factors that most acutely influence optimal stocking density for any particular farm and then develop decision support tools that solve for the optimal solution.
Beginning with an initial focus on cow behavioral response, the primary purpose of this [article] is to review briefly the current knowledge base of selected factors that influence eating, resting and rumination behavior. Specifically, major factors known to influence the cow’s behavioral response within a herd setting will be addressed including stocking density and grouping strategies.
Dairy cow’s daily time budget
Essentially, the 24-hour time budget represents the net response of a cow to her environment. Deviations in any herd from these benchmarks for behavioral routines represent departures from natural behavior and could serve as a basis for estimating the performance and economic loss from poor management strategies. Albright measured the daily behavioral time budget for a cow (Beecher Arlinda Ellen) during the lactation in which she set a world record for milk production while housed primarily in a box stall. The data indicated she spent 6.3 hours per day eating, 13.9 hours per day resting (lying) and 8 hours per day ruminating (7.5 hours per day while lying and 30 minutes per day while standing).
Matzke compared the time budget of the top 10 percent of cows (by milk yield) in a group versus the average time budget for the entire group of cows. It is interesting that the elite cows, as well as Beecher Arlinda Ellen (the first cow to produce greater than 22,600 kilograms of milk in a lactation), both rested for 14 hours per day. One could speculate the actual requirement for resting is close to 14 hours per day for the most productive cows, rather than 10 to 12 hours per day as commonly proposed.
An appropriate analogy might be the approach of formulating rations to meet the requirements of a cow above the average milk production level in a group of cows. Perhaps we need to consider designing facilities and developing management routines that allow the cows access to stalls for up to 14 hours per day; cows requiring less than this amount will use the time for other behaviors, whereas the highest producers will have adequate access to stalls.
It is clear cows need to accomplish certain behavioral activities each day, and we cannot allow our management routines to interfere. If we tally up the required number of hours each day to satisfy the basic behavioral needs, it approaches 20 to 21 hours per day: 5 to 5.5 hours per day for eating + 12 to 14 hours per day for lying and resting (includes 6 hours of rumination) + 4 hours per day for rumination while standing + 30 minutes per day for drinking.
If we add in only 30 minutes per day for other activities such as grooming and other interactions, the total time required in the budget is 20.5 to 21.5 hours per day. Given this time need, it is easy to see how our management practices can very easily perturb the cow’s normal time budget.
Improper grouping strategies that result in overcrowding and excessive time in holding pens are two common ways of upsetting the time budget and reducing herd productivity.
Feeding behavior: Measurement in competitive feeding environments
Feeding is the predominant drive in dairy cattle, and consequently any attempt to predict cow response to a particular environment must accurately describe feeding response. When a competitive situation exists at the feedbunk, dominant cows typically spend more total time eating than cows of lower social rank, resulting in greater feed intake. Some level of competition within a group of cows is inevitable; even under conditions of unlimited access to feed, cows interact in ways that give some an advantage over others.
Swedish researchers evaluated the effect of increasing competition from one to four cows per total mixed ration feeding station. As competition per feeder increased, cows exhibited shorter average eating times and accelerated eating rates. Similarly, visits to the feeding station increased in direct proportion to greater aggression during feeding. However, feed intake was unchanged. In contrast, when cows were fed limited amounts of feed, dominant cows consumed 14 percent more feed than submissive cows. This divergence increased to 23 percent as competition increased from one to four cows per feeding station. Under conditions of limited feed availability, competition escalates and feed intake of submissive cows suffers.
In addition, when competition increased from one to four cows per feeding station, a higher proportion of the feed consumption occurred during the night. The cows also spent a smaller proportion of time standing during the night with greater competition for feed.
As level of competition increased, cows of low social rank tended to adjust behaviors to a greater extent than did the more dominant cows. Instead of eating, the subordinate cows were observed standing and lying more often around milking time, when eating would have been preferred.
Additionally, as manger space is reduced, there may be a greater risk of increased feeding rate and associated risk of metabolic problems, such as abomasal displacement and subacute ruminal acidosis. The industry standard for feeding space has been about 2 feet (approximately 60 centimeters) per cow. With this amount of feeding space, 66 to 70 percent of cows in a group may eat simultaneously.
DeVries et al. evaluated the impact of increasing manger space from 1.6 feet to 3.3 feet (50 to 100 centimeters) per cow. These researchers observed a 60 percent increase in space between cows, 57 percent fewer aggressive interactions while feeding and a 24 percent increase in feeding activity during the 90 minutes following fresh feed delivery. This research clearly raises the question of what constitutes optimal manger space for cows in a competitive environment.
But we also need to keep in mind the concept of cow response versus herd profitability. The bottom line is that we need to be able to accurately model feeding patterns, meal consumption and timing and size of meals throughout the day for models to best predict total feed intake and dynamic ruminal conditions.
The assumption of steady-state conditions in the rumen clearly does not match reality, and we may now be entering a period where researchers can generate the needed feeding behavior data to make existing models more accurately reflect in vivo conditions.
Resting behavior: Implications in competitive environments
As early as 1928, researchers were investigating the importance of resting and the implications of adequate lying time for cow comfort, health and productivity. Recognized benefits of adequate resting activity include:
•reduced stress on feet
•increased blood flow to the mammary gland
•increased feeding activity
•greater overall cow health
The advantages of adequate rumination activity are obvious and involve maintenance of ruminal conditions conducive to efficient microbial fermentation. Although dietary physically effective fiber drives rumination activity, social stress (such as overcrowding and excessive competition for feed and stalls) can reduce rumination activity significantly.
Cows attempt to maintain a rather fixed amount of lying time, and their well-being is impaired when lying time is restricted for several hours. Within 10 hours, approximately 50 percent of lost resting activity has been recouped in most cases. When lying and eating are restricted simultaneously, cows choose to rest rather than eat, with an additional 1.5 hours per day standing time associated with a 45-minute reduction in feeding time.
A similar relationship was observed by Batchelder where cows with a stocking density of 130 percent preferred using freestalls versus eating post-milking and spent more time in the alley waiting to lie down than eating when compared with a stocking density of 100 percent.
On-farm measurement of resting time is difficult because most producers will not have the luxury of observing their cows throughout 24 hours to directly determine resting activity. It is worth noting that recently several producers have inquired about installing video cameras in their barns to monitor resting and other activity. What a tremendous development! For some producers, use of video monitoring equipment will help them solve behavioral and production problems on their dairy.
Also, we need to recognize this approach merely attempts to convert known short- and long-term responses to varying resting times into realistic milk yield changes. A more accurate and mechanistic approach to predicting economic consequences (long- and short-term) of variable resting times for a dairy herd must await further research on the impact of housing and management routines on health status of a herd (notably lameness), reproductive performance and lactational performance.
Grouping strategies and behavioral responses
A fundamental consideration for any decision tool on grouping strategies is the difference between conventional concepts in dominance hierarchies and grouping and what may be closer to reality. Conventionally, it is assumed that:
1. cows fight to establish social hierarchy
2. fighting stops once hierarchy is established
3. dominant cows regulate access to the resources
4. group size should not exceed number of cows an individual can recognize
5. dominance hierarchy is rapidly established – 50 percent within one hour
6. the hierarchy is stable (only 4 percent are reversed)
Contrast this rather static depiction of group interactions with the following more dynamic and likely realistic scenario:
1. continued and fluctuating levels of fighting or aggression
2. formation of subgroups within larger pens
3. inability to recognize all peers when group size exceeds approximately 100 cows
4. some individuals thrive, not by winning fights, but by not participating
5. stable hierarchy formed within two days for cows with previous social experience and within four days for cows with no previous experience
Various social behaviors and locomotor activity will return to a baseline level within five to 15 days following a grouping change such as regrouping or commingling. Essentially, this figure represents the major challenge inherent in grouping cattle. We need to manage a group of cows such that the rate of decline in physical interactions is as rapid as possible and the period of social stability is maximized.
Realistically, animals move into and out of pens continuously on many farms, and so the challenge becomes managing the magnitude of increase in the physical interactions that accompany any regrouping and introduction of new animals into a pen. A reasonable analogy would be steady-state conditions in the rumen – they are never truly achieved, just assumed.
Early tools to help with grouping decisions may assume social stability is reached and then maintained, but this would clearly be simplification of reality. Monitoring and then devising means to control the physical to nonphysical interaction ratio would be a valuable tool for producers and consultants.
A useful tool to assist with proper grouping decisions would need to consider competition for resources, stocking density, group size (Can it become too large?), group composition (especially primi- and multiparous cows commingled) and degree of commingling and movement between groups, particularly during the transition period when feeding behavior is naturally depressed.
A tool that would accurately predict the net effect of these factors on the time budget (assuming deviations from a natural time budget can be related to changes in health and performance) would be a logical research goal.
Stocking density and behavioral responses
Stocking density will affect the time budget of dairy cattle. To date, few experiments have evaluated stocking density, and some were conducted using small numbers of animals per pen. Consequently, the real effect of stocking density on larger group sizes remains unknown. A key difference between small group sizes and larger (more realistic) group sizes is the amount of time an animal will spend outside the pen for milking and other management procedures. When cows spend too much time away from the pen (basically more than 3.5 hours per day), resting time will be reduced.
Additionally, when primi- and multiparous animals are commingled, resting time is reduced much more for the heifers than for older cows (-2.6 hours per day for multiparous cows and -4.2 hours per day for primiparous cows).
Although there is clearly variation among studies, the few data reported thus far are surprisingly consistent. Some tentative conclusions to draw from these studies are:
1. At 120 percent stocking density and beyond, resting time is reduced by 12 to 27 percent. (This may be a function of pen siz,e with greater reduction for larger pens.)
2. Eating time is not affected greatly by stocking density (although meal patterns and feed intake could well be).
3. Rumination may be reduced by as much as 25 percent at 130 percent stocking density.
4. At 120 percent stocking density or greater, standing time will be increased by 15 to 25 percent.
In general, the negative effect of overstocking beyond 120 percent on resting and standing becomes more pronounced as the level increases, but there is insufficient data with larger group sizes to accurately model the effect at this point.
Considerably more research is required to develop accurate tools to evaluate management strategies to minimize negative effects on natural behaviors and time budgets. Key information would include measurement of feed intake and feeding behavior for cows group-housed in competitive situations.
Resting and standing time play a major role in cow health and productivity and effects of management on these two variables must be understood. PD
References are available upon request.
—Excerpts From 2006 Penn State Dairy Cattle Nutrition Workshop Proceedings
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