Summer Stress Management in Livestock

Dr Preeti Verma

(M.V.Sc Scholar)

Department of Veterinary Physiology & Biochemistry Jabalpur

College of Veterinary Science and Animal Husbandry Jabalpur,

NDVSU Jabalpur M.P-482001

 

Corresponding author:  preetyverma563@gmail.com

Abstract:

Summer stress negatively affects livestock production and health. Heat stress has negative effects on the health and biological functioning of dairy cows through depressed milk production and reduced reproductive performance. Heat stress is one of the major concerns which affect the production potential of dairy cattle almost in every part of world. Elevated temperature and humidity negatively affects feed intake leading to negatively affecting the reproductive potential which ultimately decrease milk production. High yielding cows more susceptible to summer stress than the low yielders. Heat stress can increase body temperature which may affect the fat synthesis in mammary gland. Apart from reducing the milk production, summer stress can also reduce the quality of milk. Internal metabolic heat production during lactation can further reduce the resistance of cattle to high ambient temperature, resulting in altered milk composition and reduction in milk yield.

 https://www.pashudhanpraharee.com/summer-stress-management-in-livestock-3/

Keywords: Summer stress, shed of animals, cooling, water supply, fans and soakers, nutritional management.

 

Introduction

 Summer stress is affect the reproductive and health status of animals. Yousef (1985) defined stress as the magnitude of forces external to the body which tend to displace its systems from their resting or ground state. In view of this, heat stress for the dairy cow can be understood to indicate all high temperature related forces that induce adjustments occurring from the subcellular to the whole-animal level to help the cow avoid physiological dysfunction and for it to better fi t its environment. Environmental factors such as ambient temperature, solar radiation and humidity have direct and indirect effects on animals (Collier et al. 1982). Heat stress occurs in animals when there is an imbalance between heat production within the body and its dissipation. Thermoregulation is the means by which an animal maintains its body temperature. It involves a balance between heat gain and heat loss. Under heat stress, a number of physiological and behavioural responses vary in intensity and duration in relation to the animal genetic make-up and environmental factors. Climatic, environmental, nutritional, physical, social or physiological stressors are likely to reduce welfare and performance of animals (Freeman 1987). Heat stress is one of the most important stressors especially in hot regions of the world. The endeavour by homeotherms to stabilise body temperature within fairly narrow limits is essential to control biochemical reactions and physiological processes associated with normal metabolism (Shearer and Beede 1990).

Signs of summer Stress:

Some signs of summer stress are reduced milk production and the lethargic behaviour of the cows. Moderate signs of summer stress may occur when the temperature is between 80° and 90°F with the humidity ranging from 50 to 90 percent. These signs include rapid shallow breathing, profuse sweating, and an approximately 10 percent decrease in milk production and feed intake by cows. As temperatures rise to 90° to 100°F and humidity remains in the 50 to 90 percent range, the cow will show severe depression in milk yield, usually greater than 25 percent, and in feed intake as her body temperature elevates. She will begin exhibiting more significant signs of heat stress, such as open mouth breathing with panting and her tongue hanging out.

Usually, the combined temperature and humidity that result in a temperature/humidity index of greater than 90 will result in severe signs of heat stress in the high-producing cow and moderate signs in lower-producing cows. In severe cases, cows may die from extreme heat, especially when complicated with other stresses such as illness or calving. Higher-producing cows exhibit more signs of heat stress than lower-producing cows because higher-producing cows generate more heat as they eat more feed for higher production. They must get rid of the extra heat generated as a result of metabolizing greater nutrients in the feed. In general, the decrease in milk production results from less feed intake by the cow. Two pounds of milk production is lost for every pound of decreased dry matter intake when temperature and humidity levels are high.

Management of summer stress:

The most practical methods to reduce summer stress can be grouped into shade, ventilation, and cooling. Common areas where cows congregate that will benefit from a reduction in heat exposure are holding areas, feed bunks, and loafing areas. But first we must also recognize the importance of cows having access to adequate water. Seek out shade, which they often will not leave to drink or eat,

• Increase water intake,
• Reduce feed intake,
• Stand rather than lie down,
• Increase respiration rate,
• Increase body temperature,
• Increase saliva production.

Shade of animals:

Although shade trees are the best method for relieving heat stress, most trees don’t survive intensive use. When not enough natural shade is available, artificial shades can provide needed shelter from the effects of solar radiation. If cows are to be confined under a shade structure, it should be oriented with a southeastern exposure of an open sidewall. Walls of freestall barns should be opened up to maximize air movement. Eliminate any wind block within 50 ft. of the windward side of the building. Each cow should be provided with 60 sq. ft. of shade. The floor should have 4-inch concrete and should be grooved to provide firm footing. It should be sloped about 1.5 to 2% for proper operation of flush systems. Earthen floors under shades quickly can become mud holes and thus are not generally recommended. The concrete slab needs to be larger than the area of the shade roof. The slab should extend 8 ft. on the north side, and 20 ft. on the east and west sides if the eave height is 12 ft. higher eaves will require that the slab be extended out farther. The recommended eave height is 12 ft. for structures up to 40 ft. wide and 16 ft. for structures wider than 40 ft. Gable roofs should have a 4:12 slope and a continuous open ridge, overshot ridge, or raised ridge cap to promote natural ventilation. All eave blocking should be eliminated. The holding area should have open sidewalls and ridge ventilation. Cows should be in the holding area for no more than one hour per milking. Shade cloth is available in patterns providing 30 to 90% shade and fabricated from a variety of yarn materials. The most common material used for animal shades is woven polypropylene fabric, providing 80% shade.

 

Cooling of Animal house:

Cooling of animal house is very important tool to reduce the higher ambient temperature.    Each area of the dairy farms facility must be considered when looking at cow cooling options. First, cool the holding pen near the milking parlor. Crowding cows into a small area restricts air flow and aggravates heat stress. Fans and sprinklers can reduce ambient temperature by 15° F, and cooled cows produce more milk than non-cooled cows. Also, it is important to minimize the time cows spend in the holding area.

 

Adequate water supply:

Cows need to increase water intake during times of summer stress to dissipate heat through the lungs (respiration) and by sweating. Water consumption will increase by as much as 50%. If water supplies are not adequate or heat stress becomes severe, cows divert water normally used in milk synthesis to the metabolic processes of heat dissipation. Water intake will rise by 5-6 gal on summer days due to temperature effects alone. Beede (1992) showed that cows consumed about 3 lb. water/lb. dry matter intake (DMI) with temperatures between 0-41° F but reached 7 lb./lb. Dry matter intake  at high temperatures with high producing cows capable of consuming 50 gallon Water/day .In order to encourage water consumption:

• Put waterers in the shade,
• Provide access to water right after milking (large intakes of water shortly before milking may elevate freezing point of milk),
• Ensure enough waterer space by:
  • Providing at least two waterer locations per group (at least 1 watering station per 20 cows and this may not be enough),
  • Having a water supply of at least 3-5 gal/minute (cows can consume 6 gallon/hr.),
  • Maintaining a minimum of 3 in. water depth, and
  • Providing a minimum of 0.65 sq. ft. of surface area per cow at single- or double-position waterers,

 

Fans and soakers:

Fans need to be clean and should generate at least 5mph wind over the back of the cow. Use a wind speed meter to detect good air movement and dead areas, especially where cows congregate. Add in soakers on the feed bunk and in the holding pen to apply water to the back of the animal. In humid climates, which include much of the US, water should be applied as a “soak” and not a mist. Maximize equipment performance by regularly monitoring and maintaining fans and soakers.

Nutritional management:

Higher temperatures can negatively affect milk production and milk fat yield, due in large part to heat stress-induced pH decrease in the rumen and leaky gut. Although it is vital to provide proper heat abatement strategies, there are also feeding strategies that may assist in reducing lost performance. Incorporating effective feed additives could help promote gut health, immune strength, and overall wellness. Healthy cows perform better, and a healthy gut can help cows manage the heat. Ultimately, this can result in greater profitability on the farm. Consult with your nutritionist about what ration changes might be appropriate for warmer temperatures, including the addition of products to optimize rumen health.

Concentrates and Forage:

Common approach to improve dietary energy density during hot weather is to reduce forage in the ration and increase concentrates. The logic is that less fibre (less bulk) will encourage intake, while more concentrates increase the energy density of the diet. Unfortunately, this logic sometimes fails. The figure shows the milk response curve to dietary non structural carbohydrate (NSC) content. On the leading edge of the curve, milk yield is low because of lower energy content (less readily fermentable NSC in the diet). However, with high dietary NSC, the milk yield actually declines despite high energy density. The reason is that excessive grain in the diet causes acidosis, leading to low milk fat percentage, off-feed conditions, digestive upsets, laminitis, and sore feet. The optimum NSC concentration appears to be in the range of 33 to 38%, although 40% NSC is acceptable with good fiber content and fiber particle length. Recommendations for feeding grain and fiber include:

• Do not exceed 55 to 60% concentrate in rations.
• Nonstructural carbohydrates (NSC) should be 35 to 40% of diet DM.
• NDF should be 27 to 33%.
• Maintain adequate particle size Feeding Dietary Fat during Hot Weather

Feeding Dietary Fat during summer:

                                                                       Fat contains 2.25 times more energy as the same quantity of carbohydrate and is particularly valuable as an energy supplement when DMI is limited, as it is during hot weather. Adding fat to the diet during hot weather does not consistently alter DMI but can improve milk yield. Diets with supplemental fat during hot weather improved fat-corrected milk yield (Knapp and Grummer, 1991; Skaar et al., 1989). In both studies, fat was also fed during cool weather. In one study, no environment by diet interaction occurred (Knapp and Grummer, 1991), suggesting no additional benefits from added fat during hot weather over those seen in cool temperatures; however, Skaar et al. (1989) found that dietary fat was beneficial only to cows that calved during the warm season. During hot weather in Arizona, a prilled fat increased milk yield by 2.6 lb/day, and in another study increased milk yield by only 1.5 lb/day in cooled or noncooled cows (Huber et al., 1994). The Arizona results suggested less response from added fat in heat-stressed than in cool cows, even though they expected that added fat would reduce heat production and lower heat stress. The data further suggest that cooling the cow is necessary to achieve full benefits of dietary adjustments such as added fat.

 

 

Protein supplement:  

                                     Inadequate quantities of dietary protein have an immediate negative impact on milk yield, but excess intake protein requires energy to process and excrete. In one study where 19 and 23% crude protein diets were fed, milk yield was reduced by over 3.1 lb simply by feeding the high-protein diet (Danfaer, 1980). Calculations revealed that the energy cost of synthesizing urea and the energy cost to excrete that urea accounted for the reduced milk output (Oldham, 1984). Thus, formulations with either inadequate or excess CP can reduce performance by lactating cows.

Excessive dietary crude protein may impair reproductive performance. Cows fed excess CP had lower first breeding pregnancy rate and lower overall pregnancy rate than cows on the moderate CP diet. Reproductive performance was similar between the moderate CP diet and the high RUP diet. Excessive CP resulted in high blood urea nitrogen (N) and ammonia contents, reducing conception rate. In another field study, cows were defined as having high or moderate milk urea nitrogen (MUN) 30 days prepartum. The odds that a cow would be nonpregnant following breeding were unaffected by MUN during cool weather. However cows calving in warm weather were six times more likely to be nonpregnant compared with cool-weather calving cows when designated moderate MUN, but were almost 18 times more likely to be nonpregnant with high MUN (Melendez et al., 2000). The practice of feeding high CP diets during hot weather to compensate for lower intake should be pursued with caution.

Mineral supplement:

Mineral needs for cattle change during hot weather. Cows sweat just like other mammals, but their sweat contains a large amount of potassium (K), unlike humans, whose sweat contains more sodium (Na). Consequently, K requirements increase during summer. In addition, cows need more Na during summer, and magnesium needs to be boosted when high dietary K is fed. Dry matter intake was improved when dietary K was greater than NRC recommendations during hot weather (Schneider et al., 1986; West et al., 1987). Feed intake was improved when diets contained 0.55 vs. 0.18% Na during hot weather Schneider et al. (1986). Current ranges for mineral supplementation during heat stress are:

• Potassium: 1.4 to 1.6% of DM
• Sodium: .35 to .45% of DM
• Magnesium: .35% of DM

A ratio or balance of ions may affect performance by influencing buffering systems in the body. Escobosa et al. (1984) were the first to evaluate diets fed to lactating cows during heat stress using the electrolyte or cation balance equation, later termed as dietary cation-anion difference (DCAD). They reported greater DMI for diets containing 320 meq Na + K – Cl/kg of feed DM vs. diets containing 195 and -144 meq, suggesting that an alkaline diet based on DCAD may be beneficial to heat-stressed dairy cows.

Feed additives:

Various other formulating diets are used for adequate nutrient given to the cow, a number of “non-nutritive” additives are available, which have the potential to improve performance during hot weather. However, an additive is only practical if it works in your herd, in your situation. Additives purchased to solve problems due to poor ration formulation are purchased for the wrong reasons. Buffers such as sodium bicarbonate are especially useful in low fiber diets, diets based on corn silage, when cows can select against forage consumption, and particularly during hot weather. Fed at about 0.75% to 1.0% of diet DM, or 5 to 8 oz per cow per day, bicarbonate can help keep cows on feed and maintain milk fat percentage.

Conclusion:

                    Reduced milk yield with heat stress occurs primarily because of declining feed intake. Greater maintenance costs during hot weather magnify the energy deficit of the heat-stressed cow. Protection from the heat using shade and cooling is the first step toward maintaining intake and milk yield during hot weather. Other steps to enhance performance include: During hot weather some form of cooling is necessary to minimize the reduction in intake and to achieve the desired response to dietary modifications. Abundant drinking water is needed due to greater consumption during hot weather. Ration formulation can be used to minimize heat production potential of the diet through the use of grains, fats, and high-quality forage.Adequate high-quality fiber must be used to maintain rumen function and cow health.

Reference:

Beede, D.K. 1992. Water for dairy cattle, Large Herd Management, H.H. Van Horn and C.J. Wilcox, eds. Management Services, American Dairy Science Assoc., Champaign, IL

Collier, R. J., S. G. Doelger, H. H. Head, W. W. Thatcher, and C. J. Wilcox. 1982. J. Anim. Sci. 54:309-319.

Danfaer, A., I. Thysen, and V. Ostergaard. 1980. Res. Report No. 492. Copenhagen: Beretning fra Statens Husdyrbrugs forsog.

Escobosa, A., C. E. Coppock, L. D. Rowe, Jr., W. L. Jenkins, and C. E. Gates. 1984. J. Dairy Sci. 67:574.

Huber, J. T., G. Higginbotham, R. A. Gomez-Alarcon, R. B. Taylor, K. H. Chen, S. C. Chan, and Z. Wu. 1994. J. Dairy Sci. 77:2080.

Knapp, D. M., and R. R. Grummer. 1991. J. Dairy Sci. 74:2573.

Oldham, J. D. 1984. J. Dairy Sci. 67:1090. Melendez, P., A. Donovan, and J. Hernandez. 2000. J. Dairy Sci. 83:459-463.

Schneider, P. L., D. K. Beede, and C. J. Wilcox. 1986. J. Dairy Sci. 69:99. West, J. W., C. E. Coppock, K. Z. Milam, D. H. Nave, J. M. LaBore, and L. D. Rowe, Jr. 1987. J. Dairy Sci. 70:309.

Shearer JK, Beede DK (1990) Thermoregulation and physiological responses of dairy cattle in hot weather. Agri-Pract 11:5–17

Yousef MK (1985) Basic principles. Stress physiology in livestock, vol 1. CRC Press, Boca Raton

 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4823286/