Παρασκευή, 14 Μαΐου 2010

The effect of temperature stress on dairy cows






J. Praks

When environmental temperatures move out of the thermoneutral zone (or comfort zone) dairy cattle begin to experience either heat stress or cold stress. Either stress requires the cow to increase the amount of energy used to maintain the body temperature and there is less energy available to produce milk. Thermoneutral zone is the range of environmental temperatures where normal body temperature is maintained and heat production is at the basal level. The ranges of thermoneutral zone are from lower critical temperature (LCT) to upper critical temperature (UCT). LCT is the environmental temperature at which an animal needs to increase metabolic heat production to maintain body temperature. UCT is the environmental temperature at which the animal increases heat production as a consequence of a rise in body temperature resulting for inadequate evaporative heat loss (Yousef, 1985). Thermoneutral zone depends on the age, breed, feed intake, diet composition, previous state of temperature acclimatization, production, housing and stall conditions, tissue (fat, skin) insulation and external (coat) insulation, and the behaviour of the animal. UCT is given as 25-26 ºC , LCT as a range from -16 to -37 ºC for dairy cows (Berman et al., 1985; Hamada, 1971). LCT for newborn calves is 10 ºC in dry and draught-free environment. LCT decreases to 0 ºC by the time the calf is 1 month old


Temperature-humidity index (THI) could be used as an indicator of thermal climatic conditions. THI is determined by equation from the relative humidity and the air temperature and is calculated for a particular day according to the following formula (Kadzere et al., 2002):

THI=0.72 (W+D) +40.6
Where W – wet bulb temperature ºC
D – dry bulb temperature ºC

The principle of THI is that as the relative humidity at any temperature increases, it becomes progressively more difficult for the animal to cool itself. (RCI Technical Information. The influence of temperature humidity index on cow performance).

THI values of 70 or less are considered comfortable, 75 – 78 stressful, values greater than 78 cause extreme stress
(http://www.guaranteedweather.com/page.php?content_id=25)


Heat stress

Heat stress for the dairy cow can be understood to indicate all high temperature-related forces that induce adjustments occurring from the sub-cellular to the whole animal level to help the cow avoid physiological dysfunction and for it to better fit its environment (Kadzere et al., 2002).

Signs of heat stress

• Restlessness
• Crowding under shade or at water tanks
• Panting (open-mouthed breathing)
• Increased salivation
• Increased respiration rate (gasping):
 80 to 120 breaths per minute moderate heat stress
 120 to 160 breaths per minute strong heat stress
 Over 160 breaths per minute severe heat stress
• Rates of gut and ruminal motility are reduced
• Lethargy
• Decreased activity
• Reduced feed intake
Under continuous heat stress lactating cows begin to show a decline in the intake at 25-27 ºC with a marked decline of 40% above 30 ºC. (RCI Heat stress in dairy cattle).

• Increased sweating

In dairy cows two types of sweating can be distinguished: both are involved in heat dissipation. The first type is insensible sweating or perspiration that leaves the body at all times, unless the relative humidity is 100%. The other type, thermal sweating, occurs as the principle evaporative cooling mechanism of the cow when the ambient temperature rises.

• Rise of rectal temperature

Rectal temperature is an indicator of thermal balance and may be used to assess the adversity of the thermal environment. In severe cases of heat stress the rectal temperature rise. The effect is increased when the relative humidity is greater than 50%. A rise of 1 ºC or less is enough to reduce performance in most livestock species (McDowell et al., 1976).

• Reduced heart rate

Initial increase in heart rates slows down when the heat stress persists. Reduced heart rate is more typical in heat-stressed cows as it is associated with the reduced rate of heat production as a response to high environmental temperatures

• Increased water intake
Heat stress increases water consumption by at least five times the normal level in temperate zones. Water and macro-mineral needs, influenced heavily by demands to maintain homeostasis and homeothermy, are altered for lactating dairy cows during heat stress. Milk is about 87% water, and contains large concentrations of the electrolytes Na, K, and CI. Therefore, lactating dairy cows have large turnover of water and these electrolytes (Shalit et al., 1991).

• Drop in daily milk production
It is accepted that heat stress is the major cause of lost production in dairy cattle in hostile regions. Some authors reported declines in the productions of milk and fat as a direct result of high environmental temperatures. This may be explaned by the negative effects the heat stress has on the secretory function of the udder (Silanikove, 1992). Some authors suggested that milk production is reduced 15%, accompanied by a 35% decrease in the efficiency of energy utilization for productive purposes, when a lactating Holstein cow is transferred from an air temperature of 18 to 30 ºC. Milk fat, solids-not-fat, and milk protein percentage decreased 39.7, 18.9 and 16.9% respectively (quoted by Kadzere et al., 2002).

Metabolic responses
Under heat stress metabolism is reduced, which is associated with reduced thyroid hormone secretion and gut motility, resulting in increased gut fill. Plasma growth hormone concentration and secretion rate declines with hot temperature (35 ºC). Ruminal pH is typically lower in heat stressed cattle (quoted by Kadzere et al., 2002).

There are great changes in dietary electrolyte balance and acid/base balance associated with heat stress. The major electrolytes involved in dietary electrolyte balance are Na+, K+, CL¯ and the buffer HCO3¯. S= is not considered so critical in the equation of dairy cattle. Na+, K+, CL¯ are the main ions involved in sweat

The effects of heat stress on dietary electrolyte balance may be summarised as:

• Appetite is depressed, there is some indigestibility of feed and gut motility is slowed
• Milk yield - at 35 ºC there is up to 33 % depression and at 40 ºC, as much as 50%
• Loss in milk quality - fat and protein content declines

• Loss in body weight

• Incidence of milk fever increases

• Metritis is more widespread

• Uterine prolapse is more common

• Mammary gland infections increase

• Uterine infections increase

• Udder oedema is more severe

• Laminitis is more frequent

• Keto-acidosis is a recurring problem

• Fertility is lowered - insemination success rate falls, embryo mortality
increases

• Calves are often premature and small

• Growing animals have markedly reduced weight gains

• Drinking water intake increases

• Nutrient deficiencies occur in marginally adequate diets
(RCI Heat stress in dairy cattle).

Water metabolism

The total body water is estimated to range between 75 and 81% of the body weight for lactating dairy cows. Temperature is among the most important environmental factors controlling water intake in lactating dairy cows. Heat stress simultaneously influences both energy and water metabolism (Silanikove, 1992). Under thermal stress cows tend to have increased water content in the rumen as a result of an accelerated water turnover rate. Water loss from an animal is a continuous process; taking place all the time and increasing during the heat stress because of additional evaporative water loss. Water intake of a dairy cow under heat stress increases significantly

Steps to reduce heat stress

There are two main management practices that have been proposed to ameliorate the effects of heat stress: physical protection and nutritional dietary manipulation

Physical protection

• Natural shade
Trees are an excellent natural source of shade on the pasture. Trees are not effective blockers of solar radiation but the evaporation of moisture from leaf surface cools the surrounding air.

• Artificial shade
Solar radiation is a major factor in heat stress. Blocking its effects through the use of properly constructed shade structures alone increases milk production remarkably. Two options are available: permanent shade structures and portable shade structures (Shearer et al., 2005).

Permanent shade structures
Major design parameters for permanent shade structures (orientation, floor space, height, ventilation, roof construction, feeding and water facilities, waste management system) depend on climate conditions. In hot and humid climates the alignment of the long-axis in an east-west direction achieves the maximum amount of shade and is the preferred orientation for tied animals, its north-south orientation is better where cows are free to move. Space requirements are essentially doubled in hot climate. Natural air movement under the permanent shade structure is affected by height and width, the slope of the roof, the size of the ridge opening etc. Painting metal roofs white and adding insulation directly beneath the roof will reflect and insulate solar radiation and reduce thermal radiation on cows.

Portable or temporary shades
Portable shades offer some advantages in their ability to be moved to a new area in different pastures. Portable shade cloth, as well as light roofing material, may be used on the temporary shades

• Cooling by reducing ambient air temperature
Air temperature of micro-environment can be lowered by air conditioning or refrigeration but the expense of such types of air cooling make these impractical.

The evaporative cooling pad (corrugated cardboard or similar material) and a fan system which uses the energy of air to evaporate water is a more economically feasible method to cool the micro-environment.

Fine mist injection apparatus – recent design of micro-environment evaporative cooling systems. This apparatus injects water under high pressure into a stream of air blown downward from above. Coolers are positioned in the roof of the shade structures or cowsheds and air is pulled through the cooler at very high rates. This system is effective in arid climates.

High pressure foggers disperse a very fine droplet of water which quickly evaporates, cooling the surrounding air and raising the relative humidity. The typical design incorporates a ring of fogger nozzles attached to the exhaust side of the fan. As fog droplets are emitted they are immediately dispersed into the fan's air stream where they soon evaporate. Animals are cooled as the cooled air is blown over their body and as they inspire the cooled air.

Misters. A mist droplet is larger than a fog droplet but cools air by the same principle. These systems do not work well in windy conditions or in combination with fans in humid environments, where mist droplets are too large to fully evaporate before setting to the ground. The consequence is wet bedding and feed.



Enhancing the cow's natural mechanism of heat loss

Cooling in hot and humid climates emphasizes shade, wetting the skin, and moving air to enhance the cow's major mechanism for the dissipation of heat – evaporative cooling from the skin.

Sprinkler and fan cooling systems (Direct evaporative cooling)
Sprinkling uses large water droplet size to wet the hair coat to the skin. Cooling is accomplished as water evaporates from the hair and skin. Upper body sprinkling followed by forced-air ventilation reduces body temperature, increase feed intake and milk yield.



Sprayers in parlour exit lanes
Exit lane sprayers are designed to automatically spray water onto the cows as they pass through.

Nutritional dietary manipulation

Evaporative heat loss through sweating and panting is the primary mechanism for heat loss at high environmental temperatures. As a result of water loss from sweating at high temperatures thirst is increased, more urine is excreted and the huge waterflux resulting from increased water consumption also causes heavy loss of electrolytes. Potassium (K+ ) loss from the skin increases by 500% in unshaded cattle. In attempts to conserve K+, cows increase urinary excretion rates of Na+.

In high temperature there is panting respiration (an important reaction to cool the body by evaporative cooling). The rapid loss of C02 results in respiratory alkalosis. Cows compensate by increasing urinary output of HC03-. Constant replacement of this ion is critical to management of blood chemistry. Heat stress increases dietary requirements for the key electrolytes, Na+, K+ and HC03-.

Dietary electrolyte balance is especially important in locations where environmental temperatures exceed 24 ºC and is exacerbated if relative humidity exceeds 50%.

Management of the dietary electrolyte balance is based on adding essential body salts and electrolytes to the drinking water and feed. It stabilises the dietary electrolyte balance, promotes homeostasis, assists the osmoregulation of body fluids, stimulates appetite, ensures normal skeletal development etc.(RCI Heat Stress in Dairy Cattle;
http: //www.rci.com.au/)

Cold stress

European cattle tend to be tolerant to cold. It is the reason why the impact of cold stress on nutrient utilization and animal performance in cattle has received less research attention. Dairy cattle are housed in the cowsheds that minimize the impact of environmental temperature fluctuations on the animals.
During the last decade uninsulated loose housing cowsheds for dairy cattle have become common also in northern countries. The temperature in the animal's rooms is only a few degrees higher than the temperature outside the cowshed. This trend in dairy cattle keeping increases the importance of cold stress investigations

The effects of cold stress on metabolic and physiological adaptations

The next systemic reactions take place in animals suffering from cold stress:
• Increased dry matter intake
• Increased rumination
• Increased gastrointestinal tract motility
• Increased rate of passage of feed and liquid in the rumen and digestive tract
• Increased basal metabolic rate and maintenance energy requirements
• Increased body oxygen consumption
• Increased cardiac output
• Increased adrenalin, cortisol and growth hormone levels
• Increased lipolysis, glyconeogenesis, glycogenolysis
• Increased hepatic glycose output

• Decreased rumen volume
• Decreased dry matter digestibility
• Decreased insulin response to a glucose infusion
• Decreased temperature of skin, ears, legs

There are a number of factors that alter the effects of cold temperatures on animals: wind, hair depth, hair coat conditions etc. It is important to emphasize the value of a clean, dry hair coat and clean, dry environment with minimal wind for animals exposed to low temperatures

For the dairy cows cold should be considered as a local problem. Direct chilling of the udder depends as much on the thermal properties of the floor as on the temperature

The potential problems in cold weather

• Make sure the waterers or water tanks are not frozen
• Cold weather increases feed needs of cows. Hay provides more heat during digestion than concentrate feeds.
• Do not close eave inlets. This will restrict the ventilation rate and create wet, damp conditions.
• Prevent draught. Cows need dry, draught-free resting area.
• Use ample amount of good, dry bedding
• Having dry teats when the cow leaves the parlor is important. One way to lessen the risk is to dip the teats, allow the dip of about 30 seconds and then blot dry using a paper towel.
(University of Minnesota Extension Service, 2004.)

Recommended literature

Berman, A., Folman, Y.M., Kaim, M., Mamen, Z., Herz, D., Wolfenson, A., Grabber, Y. Upper critical temperatures and forced ventilation effects for high-yielding dairy cows in a tropical climate. J. Dairy Sci. 1985, 68, 488-495.
Hamada, T. Estimation of lower critical temperatures for dry and lactating dairy cows. J. Dairy Sci., 1971, 54, 1704-1705.
Kadzere C.T., Murphy M.R., Silanikove N., Maltz E. Heat stress in lactating dairy cows: a review. Livestock Production Science 77 (2002) 59-91.
McDowell, R.E., Hooven, N.W., Camoens, J.K.. Effects of climate on performance of Holsteins in first lactation. J. Dairy Sci., 1976, 59, 965-973.
National Research Council,. Nutrient Requirements of Dairy Cattle. National Academy Press, Washington, 1989.
RCI Heat stress in dairy cattle. http://www.rci.com.au
Shalit, O., Maltz, E., Silanikove, N., Berman, A. Water, Na, K, and Cl metabolism of dairy cows at onset of lactation in hot weather. J. Dairy Sci., 1991, 74, 1874-1883.
Shearer J.K., Bray D.R., Bucklin R.A. The management of heat stress in dairy cattle> what we are learned in Florida.
Silanikove, N. Effects of water scarcity and hot environment on appetite and digestion in ruminants: a review. Livest. Prod. Sci., 1992, 30, 175-194.
Turnpenny, J.R., Wathes, C.M., Clark, J.A., McArthur, A.J. Thermal balance of livestock. 2. Applications of a parsimonious model. Agricultural and Forest Meteorology, 2000,m 101, 29-52.
University of Minnesota Extension Service. Managing Dairy Cows in Cold Weather, 2004.
Yousef, M.K. Basic Principles. Stress Physiology in Livestock. Vol. 1. CRC Press, Boca Raton, Fl, 1985).

24 σχόλια:

  1. No matter if some one searches for his vital thing, therefore he/she wishes to be available that in
    detail, therefore that thing is maintained over here.



    my webpage: bmi calculator

    ΑπάντησηΔιαγραφή
  2. In the US, we still express this as cubic inches, feet, or yards.
    Make sure that you don't end up with a look of patches by checking to see that the glitter falls all the way around the edges of a newly-painted area. Flawless Flooring's polished concrete floor product boasts durability and decorative seamless surfaces made mainly from epoxy and polyurethane materials.

    ΑπάντησηΔιαγραφή
  3. When someone writes an piece of writing he/she maintains the
    image of a user in his/her mind that how a user can know it.
    So that's why this article is amazing. Thanks!

    my site Clean Serv carpet cleaning

    ΑπάντησηΔιαγραφή
  4. Hi there, yup this аrticle is in fact nice and I haνe lеarned
    lot оf thіngs from it abοut blogging. thanks.


    Αlso vіѕit mу page: szakibazis.com

    ΑπάντησηΔιαγραφή
  5. This makes the mixing phase a lot easier, just put in your
    concrete and water, and off you go by the wheelbarrow
    load. If a hairline crack in concrete has turned into a
    large crack, it will need to be cleaned
    out before the patching and repairing process.

    Repairing larger cracks or holes in driveways takes a little more
    time and preparation.

    ΑπάντησηΔιαγραφή
  6. Pilots complete flights for their airline, using their simulator, either online (using a network
    such as Sim - Miles) or offline, and then file a pilot report.

    It is also a good practice to make sure that none of the climbers
    are more tired than the other. The End of Military Flight Sim
    Pro With this program you can take advantage of the military aspects of the game,
    landing and takeoff of an airplane taking includes carrier.

    If you are looking for some excitement beyond just flying,
    the Jane's series of combat flight simulators is the best place to look. Unfortunately, the series has been dormant for quite some time and there isn't any indication
    that it will be returning anytime soon.

    ΑπάντησηΔιαγραφή
  7. Do you mind if I quote a couple of your posts as long
    as I provide credit and sources back to your blog? My website is in the very same area of interest as yours and my users would certainly
    benefit from some of the information you present here. Please let me know if this alright with you.
    Regards!

    my blog post ... Sheikh Zayed Mosque

    ΑπάντησηΔιαγραφή
  8. Therefore, if you wanted to specifically look for CNN News, it is
    right there in its own directory on the front webpage. Your local
    newspapers are dynamic ways to boost your business in more far-reaching local coverage in
    your city. Such a benign amalgam is the only
    realistic hope for reconciliation. Generally Tuyetkegel Blognic could
    be consisted of any types such as social, economic, political, art, cultural, terrorism, suicides, religious, health, technology, science, business,
    marketing, and disaster news. A writer in San Francisco can read a
    story in New York at 3:00 AM (EST) and have it ready to go
    in his own paper for the Midnight (PST) deadline.

    Feel free to visit my web site: click here

    ΑπάντησηΔιαγραφή
  9. Hi, I think your site might be having browser compatibility issues.
    When I look at your blog in Safari, it looks fine but when
    opening in Internet Explorer, it has some overlapping. I just wanted to give you a quick
    heads up! Other then that, awesome blog!

    Here is my webpage: rmr calculator

    ΑπάντησηΔιαγραφή
  10. Excellent blog! Do you have any hints for aspiring writers?
    I'm hoping to start my own blog soon but I'm a little lost on everything.
    Would you suggest starting with a free platform like Wordpress or go for a paid option?
    There are so many choices out there that I'm totally confused .. Any ideas? Cheers!

    Here is my blog post Handjob Videos Free XXX Videos

    ΑπάντησηΔιαγραφή
  11. Thanks for a marvelous posting! I certainly enjoyed reading it, you are a great author.
    I will remember to bookmark your blog and definitely will come
    back at some point. I want to encourage yourself to continue your great
    work, have a nice holiday weekend!

    Also visit my weblog :: visit

    ΑπάντησηΔιαγραφή
  12. Thank you for the auspicious wгіteup. It in fаct was a amusement account it.
    Loοk advanced to faг аdded agreeable from
    you! Howeveг, how can we communicate?


    Hеre is my web site :: herbal incense blends

    ΑπάντησηΔιαγραφή
  13. It's actually a great and helpful piece of information. I'm satisfied that you simply shared this helpful info with us.
    Please keep us up to date like this. Thanks for sharing.



    My blog post: Slc-Wireless.Com

    ΑπάντησηΔιαγραφή
  14. I love what you guys tend to be up too. Such clever work
    and reporting! Keep up the terrific works guys I've included you guys to my personal blogroll.

    My website :: http://saladtv.kr/?document_srl=11767

    ΑπάντησηΔιαγραφή
  15. I usually do not create a leave a response, but I looked at through some
    responses on this page "The effect of temperature stress on dairy cows".
    I do have a couple of questions for you if
    it's allright. Is it only me or do a few of the remarks come across as if they are coming from brain dead people? :-P And, if you are posting on other online sites, I would like to follow you. Would you list of the complete urls of your social sites like your Facebook page, twitter feed, or linkedin profile?

    Feel free to visit my website ... had me going

    ΑπάντησηΔιαγραφή
  16. With havin so much content and articles do you ever run into any
    issues of plagorism or copyright violation? My website has
    a lot of unique content I've either written myself or outsourced but it seems a lot of it is popping it up all over the internet without my agreement. Do you know any solutions to help reduce content from being ripped off? I'd
    certainly appreciate it.

    Also visit my web page - check this out

    ΑπάντησηΔιαγραφή
  17. wonderful publish, very informative. I ponder why
    the opposite specialists of this sector don't notice this. You should continue your writing. I am sure, you have a huge readers' base
    already!

    my web page: Get More Information

    ΑπάντησηΔιαγραφή
  18. Just want to say your article is as surprising.
    The clearness for your submit is simply excellent and i can suppose you are knowledgeable on this subject.
    Fine along with your permission allow me to seize your RSS feed
    to keep updated with forthcoming post. Thank
    you a million and please carry on the enjoyable work.


    Visit my web-site - Abercrombie France

    ΑπάντησηΔιαγραφή
  19. Hi, I log on to your new stuff regularly. Your writing style is witty, keep doing what you're doing!

    Also visit my web blog; natural cellulite treatment

    ΑπάντησηΔιαγραφή
  20. Awesome things here. I am very glad to look
    your post. Thank you so much and I'm having a look ahead to contact you. Will you kindly drop me a mail?

    Also visit my web blog ... Boutique Guess

    ΑπάντησηΔιαγραφή
  21. Somebody essentially assist to make significantly
    posts I'd state. That is the first time I frequented your web page and thus far? I amazed with the analysis you made to make this particular put up extraordinary. Great process!

    Look at my webpage; samsung-galaxys4

    ΑπάντησηΔιαγραφή
  22. I appreciate, cause I found just what I used to be having a look for.
    You have ended my four day lengthy hunt! God Bless you man.
    Have a great day. Bye

    my website continue reading :: ::

    ΑπάντησηΔιαγραφή
  23. My partner and I stumbled over here coming from a different
    page and thought I might as well check things out.

    I like what I see so now i'm following you. Look forward to going over your web page for a second time.

    Look at my web-site; Michael Kors

    ΑπάντησηΔιαγραφή
  24. Appreciate this post. Let me try it out.

    my web site - http://www.nudeasianwomen.org (www.hihorny.com)

    ΑπάντησηΔιαγραφή