BIOLOGICAL IMPORTANCE OF RUMINATION AND ITS USE ON-FARM

R. J. Grant and H. M. Dann
William H. Miner Agricultural Research Institute
Chazy, NY

INTRODUCTION

Rumination  is  controlled  by  dietary  and  management  factors  such  as  fiber
amount  and  particle  size,  degree  of  overcrowding,  grouping  strategies,  and  other
potential stressors in the management environment. Rumination reflects cow health and
is highly sensitive to the state of well-being. However, direct observation of rumination is
labor  intensive  and  only  a  few  cows  may  be  monitored  intensively  at  once.  In  recent
years,  commercial  systems  for  monitoring  rumination  activity  have  become  available,
and  published  research  indicates  that  there  is  reasonable  correlation  between  visual
and electronic monitoring systems (Schirmann et al., 2009). Current research and on-
farm  experiences  are  beginning  to  demonstrate  the  value  of  monitoring  rumination  to
identify  nutritional  problems,  find  cows  in  estrus,  detect  health  disorders  earlier,
streamline  fresh-cow  examinations,  and  adjust  treatment  protocols  based  on  cow
responsiveness. As research accumulates, we expect routine rumination monitoring to
increase because rumination responds to stressors up to 24 h sooner than traditional
measurements allowing for more effective cow management.

NUTRITIONAL ROLE OF RUMINATION

Rumination is defined as the regurgitation of fibrous digesta from the rumen to
the mouth, remastication and reinsalivation, followed by swallowing and returning of the
material  to  the  rumen  (Welch,  1982).  This  cyclical  process  is  influenced  by  several
primary factors including dietary and forage-fiber characteristics, health status, stress,
and  the  cow’s  management  environment  (Grant  and  Albright,  2006;  Calamari  et  al.,
2014). Rumination is controlled both by the internal environment of the rumen and the
external environment of the cow, i.e. the management environment. We have known for
decades  that  receptors  located  within  the  reticulorumen  are  sensitive  to  friction  or
“scratch  factor”  from  the  fibrous  components  of  the  diet  (Gordon,  1968).  Rumination
facilitates  digestion,  particle  size  reduction,  and  subsequent  passage  from  the  rumen
thereby influencing dry matter intake. Rumination also stimulates salivary secretion and
improves ruminal function via buffering (Beauchemin, 1991).

Rumination is positively related to feeding time and dry matter intake. Following
periods of high feed intake, cows spend more time ruminating, usually after a 4-h lag.
Restricting  feed  intake  reduces  rumination:  a  1-kg  decrease  in  dry  matter  intake  has
been associated with a 44 min/d reduction in rumination (Metz, 1975).

Cows ruminate 25-80 minutes per kilogram of roughage consumed (Sjaastad et
al.,  2003).  Mertens  (1997)  reported  that  mean  chewing  time  was  150  minutes  per kilogram  of  NDF  for  long  grass  hay.  This  relationship  between  NDF  and  chewing
response forms the basis of fiber’s physical effectiveness in the physically effective NDF
(peNDF)  feeding  system.  Physically  effective  NDF  is  based  on  the  two  fundamental
properties  of  feeds  that  influence  eating  and  ruminative  chewing:  fiber  content  and
particle size. However, recent observations of Miner Institute’s dairy herd suggest that
more than simply the amount and quality of forage-fiber influence daily rumination time
(Cotanch,  2015).  It  may  be  that  cow  and  nutritional  factors  set  a  “normal”  maximum
amount of rumination activity, and as nutritionists and farm managers we essentially can
reduce that maximal activity with non-ideal management.

Ruminant nutritionists have mostly focused on the component of rumination that
is  determined  by  fiber  physical  form  and  digestibility.  However,  we  know  that  cows
voluntarily control rumination and stop when disturbed. Under acute and chronic stress
environments, rumination is depressed: rumination is highly sensitive to cow well-being.
Increasingly,  the  management  focus  is  shifting  to  these  non-nutritional  factors  that
greatly influence rumination.

RUMINATION AND MANAGEMENT

Figure 1 illustrates several key components of the management environment that
may reduce the cow’s expected rumination response to dietary peNDF, fiber digestibility,
or fiber fragility. Rumination follows a 24-h rhythm and ordinarily mature cows will spend
480 to 540 min/d ruminating under ideal conditions (Van Soest, 1994). A wide range of
management  factors  may  depress  rumination  activity  including  overcrowding,  mixed
parity  pens,  excessive  time  spent  in  headlocks,  and  heat  stress.  If  rumination  is
chronically depressed by 10 to 20% due to poor management, then we can reasonably
predict compromised ruminal function and greater risk for associated problems such as
sub-acute rumen acidosis, poorer digestive efficiency, lameness, and lower milk fat and
protein output.

In particular, recent research shows that overcrowding influences rumination time,
location, and cow posture during rumination (Hill et al., 2009). When cows are fed the
same  diet,  as  stall  and  headlock  stocking  density  is  varied  from  100  to  142%,
rumination time drops by 0.4 h/d, rumination while standing increases by 0.6 h/d, while
recumbent rumination decreases 0.9 h/d.

Dominance  hierarchy  also  affects  rumination  activity.  Ungerfeld  et  al.  (2014)
compared  the  rumination  activity  of  high  and  low  ranked  dairy  cows  and  found  that
lower  ranked  cows  ruminated  35%  less  than  higher  ranked  cows.  The  lower  ranked
cows had shorter rumination bouts that reflected lower feed intake. The effect of social
interactions  within  a  group  of  cows  on  rumination  needs  to  be  considered  when
developing  effective  grouping  strategies  for  a  farm.  This  is  especially  important  for
mixed  parity  pens  where  we  know  that  primiparous  cows  ruminate  and  lie  down  less
when commingled with mature cows. In fact, we have measured up to a 40% reduction
in rumination activity for primiparous cows when they are resting in stalls known to be
preferred by dominant cows within a pen (Grant, 2012).
Figure 1.  Physically effective NDF and fiber fragility drive rumination, but poor
management substantially reduces rumination.

RUMINATION: MORE THAN SALIVATION

Rumination is an innate behavioral need of dairy cattle (Lindstrom and Redbo,
2000) and they exhibit stereotypies when it is inhibited.  When ruminating, whether lying
or standing, cows are quiet and relaxed, with heads down and eyelids lowered. Cows
prefer to ruminate while lying down (Cooper et al., 2007; Schirmann et al., 2012) with
rumination occurring in about 80% of resting bouts. Most rumination occurs at night and
during the afternoon. Consequently, poor management that impairs lying time may also
reduce rumination. The cow’s favored resting posture is sternal recumbency with left-
side laterality (55-60% left-side preference). This combination of left-side laterality and
upright posture is thought to optimize positioning of the rumen within the body for most
efficient rumination (Grant et al., 1990; Albright and Arave, 1997).

Total sleep time in cattle is short, and rumination provides the physiological rest
and  rejuvenation  provided  by  sleep  (Ruckebusch,  1972;  Ewbank,  1978).  Cattle
experience about 3 h/d of non-REM sleep and 45 min/d of REM sleep (Ternman et al.,
2012). The EEG patterns recorded during rumination are similar to sleep or somnolence
(Bell,  1960).  Rumination  is  closely  associated  with  drowsiness  and  can  even  occur
when  the  cow  progresses  into  non-REM  sleep.  There  may  in  fact  be  a  behavioral
continuum  between  rumination  and  sleep  in  ruminants.  Sufficient  sleep  is  critical  for
both metabolic and immune function and the relationships among rumination, resting,
and sleep are critical for the health and well-being of dairy cows.

Rumination activity also increases with advancing age as do number of boli and
time  spent  chewing  each  bolus.  Total  ruminative  chewing  increases  linearly  from  2
years of age forward (Gregorini et al., 2013). This trend toward greater rumination with
advancing age may be compensation for reduced chewing efficiency.

USE OF RUMINATION ON-FARM AS A MANAGEMENT TOOL

Cows  ruminate  for  approximately  450-550  minutes  per  day  and  a  decrease  in
rumination time is typically a good sign that something is affecting ruminal function and
cow well-being. Specifically, research and on-farm experience indicate that monitoring
deviations  in  rumination  from  a  baseline  provides  the  most  useful  management
information. Rumination often responds to a stressor 12 to 24 h sooner than traditionally
observed  measures  such  as  elevated  temperature  or  other  clinical  signs,  depressed
feed intake, or reduced milk yield (Bar and Solomon, 2010). Recently, on-farm systems
have become available to monitor rumination as well as other behaviors such as activity.

Expected changes in rumination time for a variety of management routines and
biological processes have been reported based on accumulated on-farm observations
with a monitoring system that functions on sound created while chewing (SCR, 2013).
Reported deviations in rumination include: calving, -255 min/d; estrus, -75 min/d; hoof
trimming, -39 min/d; heat stress, -20 to -70 min/d; and mastitis, -63 min/d (SCR, 2013;
Miner Institute data, 2014). A recommended target for making management decisions
would be a deviation in rumination of greater than 30 to 50 min/d for either an individual
cow or a group. Patterns in the variation in rumination should reflect the feed, feeding
management, or the cow’s physical and social environment. Key areas to assess would
include standard operating procedure compliance, facility limitations, and management
routines.  Often,  changes  in  rumination  measured  on-farm  reflect  changes  in  feed  or
feeding management, cow grouping or cow movement, and overall cow comfort.

Common  challenges  faced  by  dairy  producers  that  would  benefit  from  routine
rumination monitoring include:

  Identifying nutritional problems,
  Finding cows in estrus,
  Detect  health  problems  earlier  such  as  metabolic  disorders,  mastitis,  and
lameness,
  Management  issues  such  as  grouping,  stocking  density,  or  heat  stress
abatement,
  Modifying traditional fresh-cow checks with less disturbance of cows and time in
headlocks, less labor, and greater focus on high-risk cows, and
  Changing treatment and culling decisions because cows can be monitored after
treatment to evaluate treatment efficacy.

Importantly,  research  to-date  indicates  that  it  is  not  necessarily  the  time  spent
ruminating  each  day  that  must  be  monitored,  but  the  change  in  rumination  time  from
day-to-day that is most important.

Rumination Monitoring and Transition Period

Several  recent  studies  have  demonstrated  the  usefulness  of  monitoring
rumination  activity  during  the  periparturient  period  and  in  particular  the  first  week  of
lactation  as  a  means  to  identify  in  a  timely  manner  those  cows  at  elevated  risk  of
developing a disease during early lactation (ex. Calamari et al., 2014).

Rumination  normally  decreases  by  about  70%  at  parturition  and  increases  by
approximately  50  min/d  following  calving  (Soriani  et  al.,  2012).  However,  severe
inflammation around parturition is associated with a slower increase in rumination time
following calving (Soriani et al., 2012). Additionally, more than 90% of cows that had low
rumination  during  the  first  3  to  6  days  in  milk  experienced  clinical  disease  in  early
lactation compared with only 42% for those cows that had greater rumination time. The
average rumination time prior to calving was 479 min/d (from -20 to -2 d prepartum),
and  the  value  ranged  from  264  to  599  min/d  (Soriani  et  al.,  2012).  For  the  high-
rumination cows during the first week postpartum, the increase in rumination time after
calving was very rapid: by 3 days in milk rumination time had reached the average value
observed for the entire first month of lactation. In contrast, the lower rumination cows
did not reach a stable level of rumination similar to high-ruminators until 15 days in milk.

Earlier  research  has  found  that  primi-  and  multiparous  cows  that  have  greater
lying and ruminating activity for d -2 and -6 prepartum have greater dry matter intake
and milk yield on d 1 to 14 postpartum (Daniels et al., 2003). Furthermore, cows with
less rumination time prepartum tend to have less rumination time postpartum. Shorter
rumination time is also associated with an  elevated risk of several  metabolic disorders
(<420  min/d;  Soriani  et  al.,  2012).  Figure  2  shows  a  screen  shot  from  the  SCR
rumination monitoring system to illustrate how a fresh cow with low rumination activity
may be tracked.

Most  recently,  Stangaferro  et  al.  (2015a)  compared  prepartum  rumination
patterns of lactating dairy cows from -7 d to calving that developed health disorders to
those  cows  that  did  not  up  to  30  days  in  milk.  For  all  health  disorders  combined,
rumination time was less for cows with health disorders (439 min/d) than for cows with
no health disorders (456 min/d). Rumination time was lowest on the day of calving (391
min)  than  the  6  d  preceding  calving  (range  of  458  to  463  min)  for  all  cows.  These
researchers concluded that, starting 7 d prepartum, rumination patterns are altered in
cows that suffer health disorders within 30 days in milk. Specifically, rumination time is
reduced in cows that suffer metabolic disease (such as abomasal displacement, ketosis,
or indigestion) and metritis, but not in cows with retained placenta or mastitis.

Figure 2.  Example fresh cow with low rumination time and           associated health
problems.

Ability to relate rumination time to mastitis may be related to severity of systemic
illness and type of mastitis-causing pathogen (Stangaferro et al., 2015a). Nonetheless,
the rumination monitoring system identified cows with abomasal displacement, ketosis,
metritis, and mastitis earlier than farm personnel (Stangaferro et al., 2015b). The mean
days  between  clinical  sign  of  disease  to  the  day  the  disease  was  flagged  by  the
rumination  system  was  -3  d  for  abomasal  displacement,  -1.6  d  for  ketosis,  -0.5  d  for
indigestion, -0.8 d for metritis, and -0.8 d for mastitis.

This  research  demonstrates  that  rumination  technology  may  improve  cow  care
and cow well-being by helping to identify health disorders more quickly. Research and
on-farm observations have effectively related rumination activity and mastitis detection
(Lacker  and  Bar,  2013),  rumination  and  estrus  (Pahl  et  al.,  2015),  rumination  and
grouping  strategy  (Grant  and  Albright,  2001),  and  rumination  and  calving  pen
management (Morrison et al., 2013). The relationship between rumination activity and
lameness detection is less certain. Although Van Hertem et al. (2013) found that cows
ruminated  less  at  night  (8:00  pm  to  4:00  am)  before  being  diagnosed  as  lame,  Van
Hertem et al. (2014) concluded that hoof trimming per se had relatively small effects on
rumination and was dependent on several factors such as parity, stage of lactation, and
effect of hoof trimming on subsequent distribution of locomotion scores.

Rumination and Reproduction

Pahl et al. (2015) found that rumination was reduced for about 30 hours around
estrus  but  the  primary  drop  occurred  at  6:00  am  on  d  -1  and  noon  on  d  0.  Their
research indicates the potential to use changes in rumination as well as feeding times
around estrus as a useful aid for early estrus detection. Rumination also shows great
potential for monitoring of calving events (Pahl et al., 2014). In this study, cows stopped
ruminating 123±58 min before calving and resumed ruminating 355±194 min following
calving. Schirmann et al. (2013) found that daily rumination time decreased by about 63 and  133  min  during  the  24  h  before  and  after  calving,  respectively.  Similarly,  feeding
time was decreased by about 66 and 82 min per day before and after calving.

Rumination and Heat Stress

Heat  stress  negatively  affects  cow  behavior,  including  rumination.  Tapki  and
Sahin  (2006)  found  that,  as  air  temperature  rose  from  25  to  40 o C,  eating  decreased
46%, standing increased 34%, locomotion decreased 19%, and rumination decreased
by 22%. Higher producing cows (>32 kg/d) were more sensitive than lower producing
cows, especially for lying and ruminating activities. More recently, Soriani et al. (2013)
observed  a  negative  relationship  between  daily  maximum  temperature-humidity  index
(THI) and rumination time with a reduction of 2.2 min of rumination time for every daily
maximum  THI  unit  over  76.  Rumination  time  was  negatively  related  to  breathing  rate
and  positively  to  milk  yield.  At  Miner  Institute,  we  have  observed  approximately  1  h
difference  in  rumination  time  for  cows  that  were  exposed  to  minimal  heat  stress
abatement (fans only over the stalls) versus fans and sprinklers over the feed bunk and
the  free  stalls.  This  strong  negative  relationship  between  heat  stress  and  rumination
allows  us  to  use  rumination  monitoring  to  gage  the  effectiveness  of  heat  abatement
strategies implemented by the producer.

Current Outlook for Using Rumination Monitoring

Despite the potential effectiveness of rumination monitoring, not all studies have
found useful relationships. For example, Liboreiro et al. (2015) concluded that, although
differences  in  daily  rumination  time  and  activity  between  cows  that  developed
periparturient diseases and healthy cows were observed, further research is required to
determine how rumination time and activity data can be used to diagnose cows that will
develop  disease  earlier  than  using  standard  visual  observations.  They  concluded,  as
have other research groups, that diagnosis of infectious and metabolic diseases works
best when the focus is on change in rumination time from day-to-day.

The  bottom  line  across  nearly  all  of  the  published  research  and  on-farm
observations is that the results verify that rumination monitoring systems may provide
predictive and actionable information that farmers can use to improve management of
the individual cow, a group of cows, and the whole herd.

RUMINATION: THE BOTTOM LINE

Rumination is highly sensitive to changes in dietary peNDF and fiber digestibility,
cow health and well-being. Its use as a routine on-farm monitoring tool is expected to
grow since it will allow earlier identification of problems and more timely intervention