|
Cow Comfort is a Critical Component in the Development of Oxidative Stress
|
|
|
|
|
 |
James E. Nocek, Ph.D.
Spruce Haven Farm and Research Center, Auburn NY |
In a normal day, a cow has three basic jobs: eat, rest and be milked. The real issue is that she must do these jobs well, and we are the ones that control how well she does them. To characterize the most appropriate environment (facility design) to accommodate the needs of high producing cows, we must first understand normal cow behaviors. Cows spend about 3 hours/day being milked, 5 hours/day eating, 4 hours/day standing, drinking and receiving treatment, with 12 hours left for resting.
By providing cows with behavioral comfort we offer them a state of freedom from physical and mental pain and anxiety. Alteration from this state can result in a predisposition to oxidative stress. The challenge of course is to accurately measure and objectively achieve this state. The focus of this article is on cow comfort issues, oxidative stress and ways to detect a problem. |
|
|
|
|
|
|
Feeding Area/Barrier Design
|
|
|
|
|
Cattle are gregarious and tend to coordinate their behavior such that they feed, ruminate and rest at the same time. When one cow moves toward the feed bunk, this stimulates others to feed. Social synchronization of feeding behaviors of group-housed cattle has the potential of being influenced by management factors. Cows consume an average of 7-10 meals/day and consume feed for approximately 5-6 hrs/day. The largest peaks in bunk attendance occur around the time of feed delivery to the bunk and upon return from the milking parlor. Canadian researchers separated the practices of milking and feeding and showed that delivery of fresh feed was more influential on stimulating cows to eat than returning from milking.
If offered ad libitum, fresh feed delivery 1, 2 or 4 times/day has no influence on daily lying time or incidence of aggressive behavior at the bunk. However, subordinate cows have better access to fresh feed. Offering fresh feed 1 vs. 2 times increases NDF in the orts, therefore, it increases the potential to reduce variation in diet quality during the day. However, there is no increase in NDF in orts for 2 vs. 4 times per day.
Pushing feed up is thought to be one of the most common practices to stimulate feeding activity. However, research has shown push-up was important to increase feed accessibility and help decrease sorting, but did little to stimulate feeding activity. Fresh feed delivery stimulates feeding activity more than push-up.
Feed barriers are designed to provide cows with comfortable access to feed while reducing wastage. Daily feeding times are higher and the duration of inactive standing time lower using a post and rail vs. headlock system. Headlocks reduce aggression at the feed bunk and improve access to feed for subordinate cows during peak feeding times. Optimal feeding behavior of dairy cattle housed in a freestall environment can be achieved with an 18-22 inches/cow bunk space allowance.
|
|
|
|
|
|
|
Key considerations in the design of a freestall are to study and understand the behavior of the cow in relation to her rising and lying behaviors. Partitions should allow very little interference with the animal and her activities. The animal must: 1) Enter and leave the stall easily, 2) Lie down and rise without interference from the partitions and other animals, and 3) Stand or lie in the stall comfortably. So the fewer metal barriers you have, generally the better off you are.
For most mature lactating cows, a stall approximately 48 inches wide facilitates lying and rising movements and provides sufficient comfort during normal behavior. The same cow may require a width of 52 inches during the dry period. However, this depends on stall surface, bedding type and available traction for the cow. Length from the rear of the curb step to the neck rail should be approximately 66 inches.
Lying times increase when brisket boards are not used. Without brisket boards, cow movement in the stall can be controlled by adjusting the neck rail. Cows like lying surfaces that are dry and soft. There are a variety of bedding types that can be used. Factors such as toxicity, abrasiveness, availability, adaptability to the manure system and cost must be considered. Deep beds (6-12”) with either sand or composted manure are popular beds that provide good cow comfort. The key is to maintain the bed’s depth by filling and leveling regularly as needed.
|
|
|
|
|
|
|
During normal metabolism, the body has a natural balance between free radicals and endogenous antioxidants that prevents free radicals from accumulating and harming the cell. Free radicals are naturally formed (i.e. production of ATP), as well as being generated by phagocytic cells to kill bacteria during infections. Endogenous antioxidant capacity consists of enzymatic (SOD, GSH-Px), thioproteins (cysteine, homocysteine) and low molecular weight chain-breaking molecules (vitamin C, E).
Oxidative stress occurs when there is an imbalance between free radicals and antioxidants. The accumulation of free radicals directly causes oxidative damage to lipids and certain other macromolecules. Since membranes are composed of lipids, lypo-destruction of the cell membrane can modify metabolic pathways, which alter cell function.
|
|
|
|
|
|
Causes of Oxidative Stress
|
|
|
|
|
There are several causes of oxidative stress. During disease challenges, the first immune response of the animal involves generation of free radicals by macrophages and neutrophils to kill bacteria. During this process, SOD and GSH-Px remove free radicals so as not to damage the host cell. If antioxidant capacity of the cell is compromised (deficiency of vitamins, trace elements, etc.) then high levels of free radicals can accumulate, thus damaging the host cell. High metabolic demands during lactation can cause imbalances in oxidative status. Transition cows (rapid fat mobilization, initiation of lactation, metabolic disease potential) are also very susceptible to oxidative stress. Environmental changes, particularly those associated with heat stress can predispose cows to oxidative stress. Dietary fats can also be a source of free radicals.
|
|
|
|
|
|
Relationship Between Cow Comfort and Oxidative Stress
|
|
|
|
|
When a cow’s routine and environment are interrupted or modified, she is predisposed to stress. Items that negatively affect cow comfort – improperly designed feeding areas, and freestalls, etc. – can impact oxidative stress either obviously (injury) or subtly (disrupted feeding behaviors). Poorly designed freestalls cause disrupted resting, which results in changes to the cow’s routine (less time lying, eating sorted feed, forced to lie on a hard bed, excessive standing time in a hot holding area, less time eating, etc). Disrupted routines alter behaviors. For example, behaviors like “engorging” (eating 3 vs. 8 times per day) become more common. This type of feeding behavior results in increased ruminal acid production. Resultant death of bacteria causes endotoxin release. This causes a cascade of events culminating in excessive free radical formation, which may very easily overwhelm endogenous antioxidant potential. Research has shown that supplementing antioxidants in the feed aids in mitigating free radical load, resulting in increased production performance.
Finding ways to detect possible sources of stress associated with making a cow more comfortable are critical. Observe cows and environments as part of the daily management program on each farm. Stressed cows generally have prolonged periods of lying and make fewer trips to the feed bunk. The Cow Comfort Index (CCI – ratio of cow standing to lying in the stall), lameness scoring and hock lesion scoring are good quantitative tools.
- When designing feeding areas, lower stocking densities will increase bunk usage and reduce competition.
- When overstocking is an inevitable problem, headlocks will aid in reducing aggression.
- When designing free stalls, less hardware is more attractive from a cow’s perspective.
- Cows like soft, dry beds. Deep-bedded stalls work well, but require maintenance.
- Observe areas and stalls where cows “are” and “are not” lying down, make changes as needed.
- Watch for cow injury patterns. Consistent back, hook, hock and pin lesions can provide significant information regarding stall design.
- Supplementing antioxidants in the feed can help mitigate stress.
|
|
|
|
|
|