Heat Stress and Management for Dairy Cattle

As the capital reported temperatures as high as 47˚ C in the past few weeks, Heat wave has struck the country ruthlessly, and this is the time even animals start to show signs of high temperature related stress.
Think Grain Think Feed brings to you some insights as to how some little attention and inclusions can help you manage the heat stress in your dairy animals this season.
Ambient High Temperatures and The Effects
High temperatures lead to reduced milk yield which in turn is an expensive affair. As per research paper published by Joe W. West (Department of Animal and Dairy Science University of Georgia) Each 1˚F increase in body temperature above 101.5 EF resulted in 4 and 3 lb decrease in milk yield respectively. An inter-related change is the changes in eating patterns and routines from day to night.
Counter Actions: What Can You Do?

A pragmatic approach to maintain intake is increasing the frequency of feeding of cattle, which provides fresh feeds and stimulates the cattle’s natural curiosity. Cooling systems can also be installed to encourage intake. Enhancing your approach how you deal with your cattle can help minimize heat stress. For instance, as per research, Cattle walked for 0.62 miles prior to milking to simulate being brought from pasture during hot weather had body temperature increases of about 3.5°F and 2.9°F and temperatures remained elevated for about 10 and 6 hours, respectively (Coppock et al., 1981). Therefore, it is recommended to avoid moving cattle long distances from pastures, and adopt the routine of grazing cattle during cooler evening hours and providing cooling during hot daytime hours.
2.1 Water
Undoubtedly water is the most important nutrient for lactating cattle subjected to heat stress. Milk contains about 87 percent water, and water is critical for discharge of excess body heat. Water intake directly affects the milk yield. The consumption of water increases sharply as the environmental temperature rises because of greater water losses from sweating and from water vaporization with more rapid respiratory rates , In this scenario one must consider to supply unlimited clean water under shade within easy walking distance for the cow. Water in tanks long distances from the feeding area, especially if tanks are not shaded or the area between the feeding area and the tank is not shaded may force the cow to choose shade over water, limiting performance. Offering cool water in a shaded environment will minimize the increase in water temperature due to direct sunlight and will encourage cattle to go to water.
2.2 Fibre
Following a meal heat production increases which is termed as heat increment (consists of heat of fermentation and heat of nutrient metabolism) (Maynard et al., 1979). Different feedstuffs have varying heat increments, largely because of the efficiency of utilization of the nutrient or the end products of its digestion, or because of the heat of fermentation. Fibre digestion may add significantly to the cow’s heat load. Between hay and concentrate the cattle usually consumes less hay when subjected to heat stress (Johnson et al., 1963). As per available data, high fibber diets do have a greater heat increment than diets low in fibber. The same data suggests Cattle fed high and low forage diets in hot weather, with the difference made up by concentrates, produced more fat-corrected milk, had lower body temperatures (.51˚  F lower), and had fewer respiration (14.1 fewer breaths/min) for the low fibber diets (Stott and Moody, 1960). Intake of DM and milk yield were greater for cattle fed diets containing 14 versus 17 or 21% ADF, and milk yield was less sensitive to changes in daily minimum temperature for cattle fed the 14% ADF diet (Cummins, 1992). At any given temperature DMI was greater for cattle fed the lower ADF diets. However as daily minimum temperature increased, DMI declined more rapidly for the lower ADF diets. Important to remember is that total DMI was greater for the low fibber diets. A plausible explanation for this response is that greater total DMI for cattle fed the low fibber diets contributed to increased metabolic heat production, causing a more rapid decline in intake with rising environmental temperatures. The data indicate that feeding lower fibber diets during hot weather will improve DMI and milk yield, and possibly reduce heat stress. However, this must be balanced with the need for adequate fibber in ruminant diets. Attention to fibber quality for hot weather diets is critical, since lower heat production occurs with the fermentation of high-quality forages compared with lower quality forage. Feeding high quality fibber should be preferred over minimal fibber diets during hot weather.
2.3 Fat
Fat addition to Hot Weather Diets of early lactation cattle are less subject to heat stress than mid-lactation cattle, despite greater milk yield (Maust et al., 1972). Tissue reserves are primarily fat, and implied is an improved efficiency for utilization of fats in general. Because the primary difficulty in feeding heat-stressed cattle is inadequate energy intake, the obvious advantage to including fat in the diet is improved efficiency of energy use and the greater energy density (2.25 times greater) when compared with carbohydrates. Addition of fat to the diet during hot weather can improve milk yield. Feasible applications are to add fat, not exceeding 5 to 7% total fat in the diet. Fat levels beyond these should be supplied using a rumen inert fat. As a general guideline, no more than 30 to 40% of total dietary fat should come from whole oil seeds (a source of unsaturated oils), 40 to 45% from other basal ingredients, and 15 to 30% ruminally inert fats. Another commonly used guideline is that 1/3 of dietary fat come from fats contained in the feedstuffs, from oilseeds, and from ruminally inert fats.
It can be concluded that Fat supplementation increases net energy intake in heat-stressed dairy cattle thanks to its higher energy density and its lower metabolic heat, in comparison with fibre or starch (Baldwin et al. 1980 Morrison 1983;Beede and collier 1986;Knapp and grummer 1991)
2.4 Crude Protein
During Hot Weather it is noted that digestible protein intake is reduced. Hence It is necessary to increase dietary crude protein (CP) content to supply the quantity of protein necessary to sustain milk yield. As per studies Cattle fed high CP diets had lower respiratory rates and slightly lower rectal temperatures, possibly related to improved digestion of the diet or altered metabolism. The improved intake of feed which can occur with greater dietary CP and must be balanced with the increased energy required to metabolize excess ammonia to urea. As per research during heat stress the rumen degradable protein should not exceed 61% of total CP, or that intake of rumen degradable protein should not exceed by 100 g N/day.
2.5 Minerals
Current ranges for mineral supplementation during heat stress include 1.3 to 1.6% K, .35 to .4% Na, and about .35% Mg. Among trace minerals, Se is probably the most interesting to support antioxidative defense of the cow under HS (Calamari et al. 2011) The most effective form of dietary Se in cow seems to be Se-yeast
A ratio or balance of dietary ions may affect performance by influencing the body’s buffering systems. Escobosa et al. (1984) were the first to evaluate diets fed to lactating cattle during heat stress using the electrolyte or cation balance equation. Using dietary buffers is a conventional practice. A number of “non-nutritive” additives are available which have potential to improve performance during hot weather. (An additive is only good if it works in your herd, in your situation)
Just as we take special care of ourselves in rising temperatures it is imperative that similar attention be given to the livestock. The above-mentioned inputs may not be all inclusive but may go a long run as a stepping stone. The heat stress management strategies may differ based on breed, geographic location, History and other specific factors. There can not be a uniform nutrition management plan but it is crucial that the factors mentioned above are given due considerations.
References are available upon request
by Deepika Bharti, Freelancer