Management of Dairy Animals During Heat Stress: Practical Approaches

Management of Dairy Animals During Heat Stress: Practical Approaches

 

Abstract

India is the largest milk producer of the world with 196.18 million tonnes. This was possible only due to large scale crossbreeding of local breeds and non descript breeds of cattle. Now crossbred cows are emerging as in important dairy animals. Nearly 9 to 11% of all the cows in milk are crossbred. The crossbred animals are more susceptible to heat stress. Heat stress in dairy animals is one of the leading causes of decreased production and fertility during summer months. In India, the summer temperature goes beyond 45⁰ C which is 18⁰ C above the upper critical temperature of dairy cattle. When the temperature exceeds 27⁰ even with low humidity, the temperature is above the comfort zone for the high producing dairy cows. Humidity plays significant role in heat stress. At high ambient temperature the animals waste their feed energy in Panting and Sweating the nature’s way of cooling animals by evaporation. During summer the milk production is reduced to the extent of 50%. The crossbred / exotic animals are more prone to the heat stress losses as compared to indigenous cattle.

https://www.pashudhanpraharee.com/management-of-heat-stress-during-summer-in-dairy-animals/

Introduction:

Heat Stress indicates all high temperature related stress, which induces thermoregulatory changes in cattle. During the extreme hot humid or hot dry weather, this thermoregulatory capability of cattle to dissipate heat by sweating and panting is compromised and heat stress occurs. Severe heat stress can further lead to rise in body temperature, increased pulse rate, increased peripheral blood flow, reduced feed intake, and increased water intake. When the environmental temperature goes beyond Upper critical temperature (24°-26°C for Exotic and crossbred cattle and 33°C for Zebu cattle and 36°C for buffaloes), body is unable to maintain the core body temperature through sweating and panting (evaporative heat loss mechanism). This when coupled with rising body heat production rate lead to hyperthermia in the animals. All the changes associated with heat stress lead to loss of productivity, reduced breeding efficiency and even loss of life in extreme cases. Every year in India severe loss in milk production incurred due to heat stress causing huge financial loss. Heat stress has also detrimental effects on reproduction by decreasing oestrus expression, conception rate and by increasing length of service and dry period. Though indigenous breeds of cattle are more thermo-tolerant, crossbred and exotic breeds of cattle are highly sensitive to heat stress.  Buffaloes are more prone to this owing to their black skin that absorbs more solar radiations and fewer sweat glands (only 1/6th that of cattle), compromising heat dissipation through evaporative heat loss.

When is it most stressful ?

Part of India	Comfortable months	Stressful months
Northern Part	November-February	May-September
Western Part	December-January	May-September
Southern Part	November-February	April-September
Eastern Part	November-February	April-October

 

Detecting Heat stress through symptoms:

In case of heat stress, the following symptoms are seen

• Rapid and weak pulse
• Rapid but shallow breathing
• Abnormal vital parameters:Elevated heart rate, respiration rate, rectal temperature etc.
• Unusual salivation
• Dizziness / unconsciousness
• Skin becomes dull and may be cold too
• In case of heat stroke, body temperature is very high sometimes as high as 106– 108°F.

Managing Heat stress:

The following factors are important in managing thermal stress

• Ensure that the animals are kept under shades. The most effective source of shade is trees. If shade trees are not available, thatched roof of a minimum height of 9 feet should be provided. Agri-nets with 20% perforation are also useful. If facilities are not available with the individual farmers, facilities available at the village shall be used by the community.
• Thatching the roof with materials like paddy straw etc, painting the roof with white paint or, providing a false ceiling insulation will help provide a cooler environment.
• Create barriers against hot wind using thatched wall or wet gunny cloth/ gunny bags.
• Ensure one ventilator of 3 x 1 feet per cow in covered shed. In these sheds heavy duty fan is best option to facilitate ventilation.
• Misting/Fogging of water in the microenvironment of the animal at least thrice in an hour along with provision of fan is useful in hot dry weather. Auto Mister/ Fugger with mini pumps and cyclic timers are preferable.
• Heat stress can also be managed by spraying/ sprinkling water directly on the body of animalsfor a period of 1 to 5 minutes at an interval of 10- 30 minutes. Fans/  blowers should be used to induce evaporation  from the skin of animals. With a provision of fan this method can work both in hot dry and hot humid condition.
• The most effective way of combating heat stress in buffalo is wallowing in the water pond.
• Ensure adequate round the clock drinking water to animals, which should be provided under shade.
• Feeding should be practiced during early morning, evening &night.
• Prefer grazing during early morning & late evening hours to avoid the scorching heat.
• Ration density may be increased so as to provide same nutrients at reduced dry matter intake.  Diets with low-fibre and high fermentable carbohydrate have lower dietary heat increment compared to high fibre diets.
• Ensure increased mineral supplementation during hot weather to meet the increased demand of minerals. Potassium rich mineral mixture should be preferred.

Figure 1: Animal cooling systems are very important especially in high yielding crossbreds and exotic animals.

Signs of heat Stress:

Common symptoms of heat-stressed animal include:

• Animal moves to shade
• Water intake enhanced while feed intake reduced
• Prefers standing than lying down
• Increased respiration rate, body temperature
• Increased production of saliva
• Open-mouth panting

Some tips to counteract heat stress:

Heat stress challenges the production and reproduction performance dairy animals. The milk production declines. Milk compositions like milk fat%, SNF% are also affected. Heat stress negatively affects follicular development and oestrous cycle. It is therefore necessary to minimize the effects of heat stress through an integrated solution of management, cow comfort and nutrition.

1. 1. Provide shade

Additional environmental control measures typical in modern barns include automated sprinkler systems and fan forced air that help to increase evaporative cooling for the cows.

2. Sufficient water

Availability of water is another important issue when minimizing the effects of heat stress. Attention should be given to ensure that water is clean and easily accessible. Therefore, water troughs should be cleaned regularly and placed at multiple locations in the barns, holding pens, travel alleys and feeding area. Cows should also have water easily available right after milking, so it might be necessary to place extra water source on the way back from the milking parlor.

3. Adjust feeding schedule

Under extreme weather conditions, feeding regimes might have to be adjusted in order to maximize feed intake. Cows might refuse to eat during hot daytime when sun radiation is strong. They are more likely to consume feed when radiation is moderate and the temperature cools down, for example during the night. Therefore, it might be advantageous to reschedule feeding times and to feed 40% of the daily ration early in the morning and 60% late in the afternoon/evening, giving cows access to fresh feed when they are more likely to consume it.

4. Make diet changes

Cows under heat stress have depressed DMI; simultaneously they have similar, if not slightly higher requirements for different nutrients. Therefore, adjustments in diet composition might be needed in order to meet these requirements and prevent high milk yield losses. To choose the proper diet composition under heat stress is a challenge. On the one hand, a reduced forage-to-concentrate ratio supports DMI and increases nutrient density. On the other hand, fiber content should not be compromised too much, as this may easily lead to acidotic conditions in the rumen. If this pH drop prevails for too long, acute ruminal acidosis might be the result. Thus, at times of heat stress the best quality forage, with easily fermentable fiber and high digestibility, should be supplied.

5. Yeast supplementation

Another beneficial tool is to add autolyzed yeast, like Levabon® Rumen, to the diet in order to stabilize rumen pH and thus support gastrointestinal comfort. To meet the energy requirements of heat stressed cows with a reduced feed intake, besides increasing the concentrate-to-forage ratio, other solutions that can help to increase nutrient digestibility are also helpful.

The supplementation with autolyzed yeast, Levabon® Rumen, might be beneficial, as it enhances rumen efficiency by getting more nutrients from the same amount of feed. The aim is to help the dairy cow maintain ruminal and digestive comfort and to minimize feed consumption losses. Levabon® Rumen helps to improve digestibility in cows and efficient feed utilization, even under non-optimal environmental conditions. Unlike yeast cultures, autolyzed yeast consists of pure yeast without carrier, readily available for rumen microflora as cells are already broken-up because of the autolysis (self-digestion) process.

This supplies high quality nutrients to rumen microbiota like B-vitamins, peptides, amino acids and functional components like nucleotides, enzymes and cell-wall carbohydrates (mannan, glucan). They help to maintain ruminal and intestinal comfort and health, especially important under heat stress conditions.

6. Essential oils / phytogenic feed additive supplementation

Additionally, Digestarom® — a phytogenic feed additive — helps to support DMI by stimulating feed intake and rumination, thus preventing sharp drops in DM consumption.

Strategies to reduce the negative effects of heat stress:

Breeding Management:

As cows exhibit lesser heat symptoms during heat stress zones as compared to thermal comfort periods, it is necessary to adopt a good heat detection program to detect cows with marginal heat symptoms. It is always advisable to continue AI breeding instead of using bulls because in natural breeding both bull and cows suffers infertility due to summer stress. Genetic selection of heat tolerant animals and inclusion of heat tolerance as a trait in selection programme will be a boon to the farms.

Cooling systems in the farm

Fans in combination with water sprinkling facility provide the best cooling option. Excessive sprinkling should never be practised as it can result into wet bedding making animal prone to mastitis and other diseases. The farm should be well ventilated.

Feeding Management

Heat stressed animals are more likely to have lower reproductive and productive performance. Feeding high quality forages and balanced rations will decrease some of the effects of heat stress and will boost performance of the animals. Some nutritional management tips to manage heat stress are:

• Provide high quality feeds like total mixed rations
• Increase the frequency of feedings
• Feed during cooler times of the day
• Keep feed fresh as much as possible
• Provide high-quality forage
• Provide adequate fibre
• Use of bypass proteins can enhance the milk yield and protein content.
• Intake of sufficient cool water is probably the most important strategy for animals to undertake during heat stress.

Providing natural or artificial shade area

Plantation around the farm will help in alleviating heat load from the animals. But, in today’s commercial dairy industry, it is not always practicable. Therefore, provision of artificial shade area by shade cloth or a naturally well ventilated structure with open sidewalls can keep the animals away from direct solar radiation.

Selection of heat tolerant animals

Genetic Selection of animals based on specific molecular genetic markers for heat tolerance will definitely be a boon to alleviate heat stress in cattle and buffaloes by identifying the heat tolerant animals.

Some important tips of summer management desirable for improving production and reproduction performance in buffaloes are listed below:

Provision of thermal comfort

• Trees and landscaping around the shed
• Housing of buffaloes in proper ventilated sheds
• Washing/wallowing/sprinkling/splashing/showering
• Provision of cool drinking water in extreme hot season
• Cooling device such as fans, wet curtains or air coolers
• Avoid movement of buffaloes to and from the wallowing pond in the hot sun

Nutritional Management

• Feeding of green fodders/silage/hay
• Feeding green fodder mixed with dry fodder
• Provision for night feeding to increase the intake
• Grazing early in the morning and late in the afternoon to avoid sun exposure
• Area specific mineral mixture supplementation
• Proper pre-partum feeding of advance pregnant heifers

Reproductive Management

• Provision of thermal comfort to heifers, buffaloes and bulls
• Improve heat detection efficiency
• Observe for estrus thrice in a day and at least once during night hours
• Close observation of all non-pregnant buffaloes for cervical mucus discharge and its characteristics
• AI during cooler parts of the day and night
• Insemination between mid and late estrus with good quality semen
• Repeat insemination in case of prolonged estrus
• Provide cooler environment for first 15 days after AI
• Avoid breeding of underweight heifers

 

Conclusion

The key to maintaining animal health and performance in periods of heat stress is to support the rumen and gut barrier function and ensure proper liver function. Producers should consider feed additives that support intestinal barrier function, neutralise endotoxins in the intestine, improve digestibility and promote feed intake. Finding the right solution may require a combination of additives tailored to a farm’s specific requirement. An integrated solution should be applied to minimize production and profitability losses associated with the effects of heat stress in dairy animals. This should include animal comfort, by providing animals with a comfortable environment and access to water, adjusted feeding management and necessary diet modifications. Feed additives like Levabon® and Digestarom® can be valuable tools that help to support DMI, increase digestibility and gastrointestinal comfort, thus minimizing the negative effects associated with hot and humid environmental conditions. Heat stress in dairy animals can challenge the reproductive and production potential of the animals. Implementing proper breeding programs, cooling strategies at farm with better feeding programs can help to minimize some of the negative effects of heat stress.

 

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                                                                         Dr. Alok Kumar Yadav

Veterinary Officer, CCBF, Andeshnagar, Lakhimpur-Kheri (U.P.)

Corresponding author: – alokvet1000@gmail.com

References:

1. Managing Reproduction during Times of Heat Stress, ABS Global Technical Services Newsletter
2. Rensis, Fabio D. and Rex.J. Scaramuzzi. 2003. Heat stress and seasonal effects on reproduction in the dairy cow—a review. Theriogenology 60:1139-1151.
3. Buffalo under Heat Stress, AK Balhara, Jerome A and Inderjeet Singh.Central Institute for Research on Buffaloes, Indian Council of Agricultural Research.