Promoting dry matter intake (DMI) to support milk production is a cornerstone of successful dairying.A majority of research investigates how changes in feed nutrient composition impacts DMI of lactating dairy cows. However, DMI of group-housed lactating dairy cows is also affected by feeding behavior, which is modulated by the environment, management, health, and social interactions.Farmers can use knowledge of dairy cow feeding behavior to improve DMI, cow health, welfare and performance, and farm profitability.
Condensed by Milkproduction.com staff from a paper by Naomi A. Botheras, The Ohio State University, Columbus, Ohio, USA, originally published in the Proceedings of the 2007 Tri-State Dairy Nutrition Conference.
For example, management practices and each cow’s social status influences her access to feed at the times she wants to eat. High producing dairy cows must be able to eat whenever desired to optimize cow health, welfare and productivity, and ultimately farm profitability. Increased time spent eating has resulted in increased milk yield (Shabi et al. 2005), suggesting producers may increase performance by encouraging lactating dairy cows to spend more time eating.
The impact of factors such as feed bunk management practices (e.g., feed bunk space and design and frequency of fresh feed delivery) and social conditions (e.g., competition for feed and group composition) on the feeding behavior of group-housed dairy cows will be discussed below.
Patterns of Feeding Behavior
High-yielding dairy cows housed indoors typically spend about 4 to 6 hours/day feeding, with feeding time divided into 9 to 14 feeding sessions, or meals, over the course of the day (Dado and Allen, 1994; Tolkamp et al., 2000; Fregonesi and Leaver, 2001; Grant and Albright, 2001; Phillips and Rind, 2001a; DeVries et al., 2003b).
On pasture, there is a strong temporal pattern in feeding behavior with large influences due to the times of sunrise and sunset, and removal of cows from pasture for milking. At pasture, major peaks of grazing behavior occur immediately upon entry to the paddock following milking with a smaller peak around midnight (O’Connell et al., 1989; Orr et al., 2001; Gibb et al., 2002). A clear relationship between time of sunset, cessation of grazing, and commencement of lying-down behavior has been described for cows at pasture, with very few cows observed grazing soon after sunset.
Indoor housing differs considerably from pasture conditions. Changes in physical and social factors (e.g., artificial lighting, confinement, and reduced availability of space) for housed cattle substantially alter both the level and distribution of various behavioral activities. In a free-stall barn with TMR fed twice daily, cows were in the feed alley nearly every minute of the day with the highest percentages present during the daytime and early evening and the lowest percentage during late evening and early morning (DeVries et al., 2003a). A dramatic increase in feed alley activity occurred immediately following delivery of fresh feed and return of cows from milking. Increases in number of animals at the feed alley in the hour immediately following feed push-ups were not nearly as large as were responses to milking and feeding.
Delivery of fresh feed appears to be a much stronger feeding stimulus than the return from milking (DeVries and von Keyserlingk, 2005). Contrasting with grazed dairy cows, daily feeding patterns of group-housed dairy cows is largely influenced by timing of fresh feed delivery, rather than the times of sunrise and sunset, or return from the milking parlor. Timing of feed delivery also affected lying behavior. Cows that received fresh feed upon return from milking, laid down about 20 min later than cows returning to stale feed. Cows with access to feed after milking stood longer (48 versus 21 min) than cows unable to feed after returning from milking (Tyler et al., 1997). The practical significance is possibly reduced risk for intramammary infection since the teat sphincter has more time to close prior to exposure to environmental bacteria when cows lie down after milking.
Frequency of Feeding
A total mixed ration (TMR) provides the balance of nutrients needed to maintain a stable and efficient microbial population. However, feed availability and intake distribution also contribute to a stable ruminal microbial population (Nocek and Braund, 1985), reducing the risk of subacute ruminal acidosis. Typically, group-housed dairy cows are provided with fresh feed once or twice daily. Increasing frequency of fresh feed provision may better distribute intake over the course of the day, with potential improvement in rumen microbial stability. Indeed, research has shown that increasing the frequency of feed delivery can reduce diurnal fluctuations in rumen pH (French and Kennelly, 1990; Shabi et al., 1999).
Increasing frequency of feed provision both increased, as well as changed the distribution of, daily feeding time resulting in more equal access to feed throughout the day (DeVries et al., 2005). Although statistically significant, increases in total daily feeding times were small (10 to 14 min). Similar results (Mäntysaari et al., 2006) were found comparing feeding a TMR once or 5 times a day. Eating time was distributed more evenly over the day for cows fed more frequently, while cows fed once daily had a clear peak in feed consumption immediately after feeding. Thus, increasing feed delivery frequency may more evenly distribute feeding time over the course of the day, contributing to decreased diurnal variation in ruminal pH and reduced risk of subacute ruminal acidosis.
Overcrowding the Feed Bunk
While more frequent feeding may even out distribution of feeding time over the course of the day, the amount of bunk space and a cow’s social dominance may influence whether cows are able to feed at the times they want to eat. Accessibility of feed may be more important than actual amounts of nutrients provided (Grant and Albright, 2001). Additionally, feed intake and milk production will generally improve when cows are allowed access to feed when they want to eat. Cost considerations may lead to limits on feeding space availability. Facility design may also influence the number of cows which have to share a particular resource. Furthermore, the tendency for cows to synchronize their behavior, and especially to want to feed when fresh feed is delivered, will also impact the number of cows attempting to eat at the same time. Thus, a number of conditions may limit cows being able to access feed when they want to eat, resulting in feed restriction.
Initial research suggested that overcrowding at the feed bunk did not reduce eating time (Collis et al., 1980; Friend et al., 1977; Wierenga and Hopster, 1990). The limited effect of overcrowding on total eating time was thought to be due to the relatively short amount of time spent eating each day allowing cows to compensate for changes in feed access with overcrowding. More recent research has demonstrated that increasing access to feeding space increases feeding activity (DeVries et al., 2004) while overcrowding of either headlocks (Batchelder, 2000) or post-and-rail feed barriers (Huzzey et al., 2006) reduced feeding times. These changes were most obvious during times of peak feeding activity.
In a comparison between 4 and 6 row barns, which provide very different bunk space per cow at similar stocking rates, extra feed space per cow in a 4-row barn improved access to feed at peak feeding times (Mentink and Cook, 2006). Although 24 inches of bunk space per cow has traditionally been regarded as adequate (Grant and Albright, 2001), total daily feeding time has increased when feed bunk space increased from 25 to 36 inches/cow (DeVries and von Keyserlingk, 2006). This may be a reflection of the fact that the recommended width may be narrower than many mature Holstein dairy cows (Mentink and Cook, 2006). Furthermore, dairy cows distribute themselves at the feed bunk to maintain some distance between neighbors while feeding; this spacing pattern is influenced by social rank (Manson and Appleby, 1990). Therefore, although maximum utilization of the feed bunk (all feeding positions simultaneously occupied) may be rarely observed (e.g., Mentink and Cook, 2006), this may not necessarily indicate that all cows are unrestricted in ability to access feed whenever desired.
All cows are highly motivated to access freshly delivered feed (DeVries and von Keyserlingk, 2005). When feeding space is inadequate, some cows may be unable to eat when fresh feed is delivered, with consequent shifts in their feeding time. Cows frequently sort TMRs, thus reducing feed quality throughout the day (Bal et al., 2000; Kononoff et al., 2003; DeVries et al., 2005; Leonardi et al., 2005). Therefore, cows forced to delay feeding due to overcrowding may consume a poorer quality diet and be unable to meet their nutritional demands for milk production. Furthermore, when cows cannot eat when they desire, they may over-eat at the next meal leading to digestive upsets. Increased feeding competition due to overstocking may reduce intake and increase feeding rate, possibly increasing the risk for metabolic problems such as displaced abomasum and subacute ruminal acidosis (Shaver, 1997, 2002; Cook et al., 2004).
When feed space is limited, some cows may be forced to stand and wait for an available feeding spot. Time spent standing inactive in the feeding area was observed to decrease when more bunk space was provided, with greatest differences in inactive standing occurring during periods of peak feeding activity (DeVries and von Keyserlingk, 2006; Huzzey et al., 2006). Overcrowded cows preferred lying down over eating after milking (Batchelder, 2000). The overcrowded cows spent more time standing in the alley waiting to lie down than they did eating. Increased time spent standing inactive in the feeding area may have long-term negative hoof health effects. Increased standing times, especially on hard surfaces, have been associated with higher risk for developing hoof and leg injuries (Colam-Ainsworth et al., 1989; Greenough and Vermunt, 1991; Singh et al., 1993; Dippel et al., 2005).
Increased aggression in the feeding area with overcrowding has been noted by a number of researchers (Olofsson, 1999; DeVries et al., 2004; DeVries and von Keyserlingk, 2006; Huzzey et al., 2006). Aggression could have consequences for hoof lesion development and lameness; less dominant cows may avoid dominant animals by turning away from them, causing twisting of the rear feet on an abrasive surface (concrete) which leads to shearing effects on the hoof and various hoof injuries. Cows that engaged in a high number of aggressive interactions at the feed bunk had more severe claw-horn lesion scores than cows that did not engage in such encounters (Leonard et al., 1998). Shaver (2002) suggested that the potential for laminitis may be greater when limited feeding space coincides with overcrowding of free stalls (as is often the case), because cows may consume fewer, but larger, meals or have reduced feed intake (due to overcrowding at the feed bunk), and spend more time standing on concrete rather than lying in stalls (due to overcrowding of free stalls).
Reduced access to feed will have differing impacts on individual cows within a group. High ranking cows may be completely unaffected, while low ranking cows may struggle to eat when they wish (Olofsson, 1999; Wierenga and Hopster, 1990). Frequency of aggressive interactions at the feed bunk decreased when more bunk space was provided; cows of lower social status experienced the greatest decreases in number of feed bunk displacements per day (DeVries and von Keyserlingk, 2006). Providing increased feed bunk space may improve access to feed and reduce competition at the feed bunk, particularly for subordinate cows.
Feed Bunk Design
Physical environment at the feed bunk may also influence feeding behavior. While average daily feeding times did not differ between headlock barrier or post-and-rail barrier feed systems for one study (Endres et al., 2005), daily feeding times were greater for a post-and-rail barrier than a headlock feed barrier in another (Huzzey et al., 2006). Other workers found greater group DMI with a post-and-rail barrier design (Batchelder, 2000). Differences may be due to post-and-rail feed barriers being more comfortable for the cows, or a learned aversion to headlocks (Huzzey et al., 2006). However, Endres et al. (2005) observed that during periods of peak feeding activity, cows that had lower feeding times relative to group mates when using the post-and-rail barrier showed more similar feeding times to group mates when using the headlock barrier. There were also 21% fewer displacements at the feed bunk when cows accessed feed by the headlock barrier compared with the post-and-rail barrier. Similarly, Huzzey et al. (2006) found cows ranked lower in the social hierarchy at the feed bunk were displaced more often when feeding at a post-and-rail barrier. A headlock barrier system can reduce aggression at the feed bunk and improve access to feed for socially subordinate cows during peak feeding periods. Headlocks may provide some protection against competitive interactions at the feed bunk by offering physical separation between adjacent cows.
The type of flooring used in front of the feed bunk may also influence cow behavior. While not all work shows an advantage to softer surfaces in front of the feed bunk (Fregonesi et al., 2004), both rubber flooring (Olsson et al., 2005) and sawdust platforms (Tucker et al., 2006) have been found to increase eating time compared with concrete.
Observations of increased standing and lying on rubber surfaces at the feedbunks highlights the importance of taking into consideration the comfort of the entire facility rather than concentrating on just a single component (Tucker et al., 2006). Results showing that cows clearly prefer to stand on softer flooring surfaces than concrete when eating (indicating that concrete flooring is uncomfortable) and that having softer surfaces near feed bunks may increase the time cows spend in the area, including time spent eating. There is also increasing evidence of a link between concrete flooring and development of lameness (Vokey et al., 2001; Cook, 2003; Somers et al., 2003; Vanegas et al., 2006).
Social rank is closely related to factors such as age and body size. Therefore, heifers are often lower in a group’s dominance hierarchy than older cows. Because of the effects of aggression at the feed bunk on feeding behavior (discussed above), primiparous cows may benefit from being grouped separately. On pasture, a mixed group of multiparous and primiparous cows grazed for less time than either multiparous or primiparous cows grouped alone (Phillips and Rind, 2001b). Free stall heifers housed separately from older cows increased eating time and had a higher DMI (Krohn and Konggaard, 1979). However, in a loose-housing, robotic milking unit, total eating time was about 30 min longer for primiparous cows housed in a mixed parity group than primiparous cows housed alone (Bach et al., 2006). Further research is required to determine any potential benefits on feeding behavior and DMI of separately managed primiparous and multiparous cows.
Ruminating and Lying Behaviors
While feeding behavior dramatically impacts DMI of lactating dairy cows; however, cows also need to ruminate for full and efficient digestion of feed. Cows prefer to ruminate while lying down (Phillips and Leaver, 1986; Cooper et al., 2007), making access to a comfortable and inviting place to lie down a necessity in maximizing rumination time. Overcrowded cows were observed to spend significantly less time ruminating during a 24-hour period than uncrowded cows (Batchelder, 2000).
Sufficient lying time is essential not only for rumination but also because lying behavior and rest are very important for dairy cows, and cows are highly motivated to lie down, even after short periods (2 to 4 hours) of deprivation (Metz, 1984; Bolinger et al., 1997; Cooper et al., 2007). Cows have a rather inelastic demand for lying, and lying has a higher priority over eating for cows simultaneously deprived of the opportunity to do both (Metz, 1984; Fisher et al., 2003). Increased lying behavior is also associated with a reduction in lameness and increased blood flow to the udder, so maximizing lying time may ultimately increase longevity, reduce health costs, increase productivity, and improve cow welfare. Since high-producing cows generally spend more time eating, less time is available for lying and other activities. Under some conditions, cows may not be able to fulfill their needs for eating and lying time with serious implications for dairy cow health, welfare, and productivity.
Feeding behavior of group-housed dairy cows is influenced by management practices at the feed bunk, as well as the physical and social environment. The feeding pattern of group-housed dairy cows is largely influenced by the timing of fresh feed delivery, with fresh feed delivery stimulating eating more than return from milking. Delivering fresh feed more frequently improves feed access for all cows and reduces sorting of the TMR. This will potentially reduce variation in diet quality consumed by cows, with benefits for milk production and reduction in risk of subacute ruminal acidosis.
Reducing overcrowding at the feed bunk increases feeding time, particularly during periods of peak eating activity, reduces the time cows spend standing idle waiting to gain access to the feed bunk, and reduces aggression in the feeding area. The use of headlock feed barriers may reduce aggression at the feed bunk and enable subordinate cows more equal access to feed, particularly if cows are overcrowded at the feed bunk.
Cows clearly prefer to stand on softer flooring surfaces than concrete, and providing softer surfaces such as rubber mats near the feed bunk may increase the time cows spend in the area, including time spent eating, and may be beneficial for hoof health and lameness.
In conclusion, farmers can use knowledge of dairy cow feeding behavior to improve DMI, cow health, welfare and performance, and farm profitability.
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