Stress, Strain, and Productivity in Relation to Animal Habitat | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Impact of Climate on Livestock

1. Causes of Stress

• Livestock face various stressors such as climate, feed, parasites, and diseases.
• Adverse climate, particularly hot and humid conditions, is a primary stress factor.

2. Climate's Influence on Livestock

• Adverse climate affects grazing behavior, feed and water intake, animal growth, and reproductive processes.
• Production of milk, meat, wool, or eggs is also impacted by climate conditions.

3. Tropical Climate Characteristics

• The term "tropical" refers to the region between the Tropics of Cancer and Capricorn.
• Tropical climates vary based on factors like latitude, altitude, land-water distribution, soil, and topography.
• Despite diversity, common characteristics include small daily and seasonal temperature variations, especially near the equator.

4. Micro-Climates in the Tropics

• Specific micro-climates exist due to the interaction of factors like ocean currents, winds, rainfall, and vegetation.
• Climate is a combination of elements, including temperature, humidity, rainfall, air movement, radiative conditions, barometric pressure, and ionization.

5. Key Climate Elements

• Temperature and rainfall are crucial climate elements affecting livestock.
• Effective rainfall, representing the amount available to vegetation, is more important than total rainfall in practice.

6. Challenges in Tropical Regions

• Livestock in tropical regions face challenges like relatively small daily and seasonal temperature variations.
• Day length remains fairly constant, affecting the total hours of sunshine and solar radiation.

7. Overall Impact on Livestock

• Livestock health, grazing, feed consumption, and reproductive capabilities are significantly influenced by the prevailing climate.
• Understanding and managing these climate-related factors is crucial for maintaining healthy and productive livestock.

Grazing Behavior of Cattle and Climate Stress

1. Daytime Grazing Variation

• Climate significantly affects how long cattle graze during the day.
• Factors like climate stress, cattle breed, and available pasture impact the duration of daytime grazing.

2. Effect on High-Grade Cattle

• High-grade Bos taurus cattle in humid tropical climates graze less during the day.
• They mainly graze in the early morning and late afternoon, adjusting based on climate stress levels.

3. Night Grazing Practices

• In many tropical areas, indigenous cattle are kept indoors at night, supposedly for protection.
• However, experts suggest that indigenous cattle should be allowed to graze at night, especially when feed quality is low.

4. Feed Quantity and Quality Impact

• Limited feed quantity increases total grazing time.
• Poor feed quality makes cattle more selective in grazing.
• During sub-optimal conditions, cattle may graze more at night to cope with climate stress.

5. Nomadic Livestock Challenges

• Observations on grazing behavior are lacking for nomadic cattle in semi-arid tropics.
• Dry seasons lead to decreased water in forage, increasing the demand for water.
• Cattle walk longer distances for feed and water, raising their demand and generating heat, depleting water resources.
• Physiological stress during dry seasons reduces productivity in nomadic or semi-nomadic livestock.

6. Compounding Factors

• Decreasing water content in forage during the dry season increases the demand for water.
• Nutrient content in available feed drops as the dry season progresses.
• Water supplies may become highly mineralized, and ambient temperatures rise, further increasing water requirements.
• These factors collectively stress nomadic livestock in semi-arid tropics, potentially reducing their productivity significantly.

Intake and Utilization of Feed and Water in Livestock

1. Feed Intake

• High temperatures affect how much cattle eat; all cattle eat less in hot weather.
• Bos taurus breeds eat less at lower temperatures compared to Bos indicus breeds.
• Extremely high temperatures, above 40°C (104°F), lead to a significant decrease in feed intake, especially in Bos taurus-type cattle.

2. Humidity and Feed Intake

• Increased humidity, above 23.9°C (75°F), reduces feed intake in all cattle.
• Radiation stress affects feed intake in Bos taurus but not in Bos indicus-type cattle.
• In a tropical climate, hay intake is lower, though overall nutrient intake remains similar.

3. Water Intake

• Climate complexity influences water intake in livestock for essential body functions and heat regulation.
• Water intake generally rises with increasing ambient temperature, but the relationship is not straightforward.
• For Bos taurus milking cows, water intake increases up to 29.4°C (85°F) and declines beyond due to decreased feed intake and productivity.

4. Humidity's Impact on Water Intake

• Humidity plays a role; above 23.9°C (75°F), increased humidity reduces water consumption and increases drinking frequency in cattle.
• Higher radiation intensity increases water consumption, likely due to the animal using more water for cooling under radiation stress.

5. Efficiency of Utilization

• Controlled conditions show that as ambient temperature rises, feed utilization efficiency decreases.
• Field conditions may show insignificant differences in utilization efficiency.

6. Nutrient Loss through Sweating and Drooling

• Sweating and drooling are relevant in cattle, but their significance varies between breeds.
• As temperatures rise, different breeds of cattle exhibit varying sweating behaviors.
• Generally, loss of nutrients, especially minerals, through sweating and drooling is not practically significant in livestock.

Impact of Climate on Livestock Growth

1. Appetite and Productivity

• Climatic stress can reduce appetite, leading to decreased feed intake and grazing time.
• This is likely to affect livestock productivity, especially in terms of growth and milk production.

2. Limited Experimental Evidence

• There's limited field experimental evidence on how a tropical climate affects the growth of livestock.
• The impact of climatic factors on the growth rate of Bos indicus-type cattle is not well-documented.

3. Bos Indicus-Type Cattle Growth

• Bos indicus calves often have low birth weights and slow growth.
• It's unclear how much of this slow growth is directly influenced by the climate.

4. Sheep and Goats Growth

• Information on climate's impact on sheep and goats growth is sparse.
• High temperatures in the Australian tropics can result in low lambing percentages and small, weak lambs with high mortality.

5. Effect on Piglets

• Newborn piglets lack efficient temperature regulation and are vulnerable to extreme temperatures.
• Infra-red lamps are used in temperate countries to prevent chilling in piglets, especially in the first days of life.

6. Pig Growth in Tropical Climate

• In tropical climates, piglet mortality due to overheating can be reduced by providing additional heat in the early days.
• Optimal air temperature for maximum pig growth and food conversion efficiency decreases as pigs age.

7. Chick Tolerance to Temperature

• Chicks are more tolerant to high temperatures than adult birds.
• Transporting day-old chicks in hot conditions may pose a risk of overheating in thick boxes.

8. Impact on Poultry Growth

• High ambient temperatures likely reduce the growth rate of poultry.
• Different breeds react differently, with light breeds better withstanding heat compared to heavy breeds.

Impact of Climate on Milk Production

1. General Effects on Milk Production:

• High ambient temperatures tend to depress milk, butterfat, and solids-not-fat production in cattle.
• Experimental evidence often struggles to separate direct and indirect climate effects on production.

2. Fiji-New Zealand Twin Experiment:

• In a twin experiment comparing temperate and tropical climates, milk production was 44% higher in temperate conditions.
• Butterfat production showed a 56% increase in the temperate climate.

3. Individual Twin Reactions:

• Individual twins at the same location reacted differently to the climatic environment.

4. Psychrometric Chamber Studies:

• Studies in psychrometric chambers provided detailed insights into the impact of climate on milk production.
• Optimal temperature for milk production in temperate cattle breeds is around 10°C (50°F).
• Critical temperatures leading to a decline: 21°C to 27°C (70°F to 80°F) for Jersey and Holstein, 29°C to 32°C (85°F to 90°F) for Brown Swiss, higher for tropical-type cattle.
• Butterfat content declines after 29°C (85°F) due to a steeper decline in milk production than in butterfat percentage.

5. Effects on Milk Constituents:

• High temperatures affect other milk constituents, causing a rise in chloride content and a fall in lactose and total nitrogen content.

Impact of Climate on Reproduction

1. Major Factors Affecting Reproduction:

• Key climatic factors affecting reproduction include ambient temperature, humidity, and daylight length.

2. Effect on Cattle Reproduction:

• High environmental temperatures and sudden temperature fluctuations can directly impact cattle reproduction.
• High humidity intensifies the impact of high temperatures on reproductive performance.

3. Effects on Sheep Reproduction:

• Ewes in hot environments may experience embryonic death and foetal dwarfing.
• Continuous exposure to high air temperatures can eventually kill all embryos.

4. Male Sheep and Goats in Tropics:

• Males imported from temperate zones to the tropics may be less fertile or even sterile for up to a year, likely due to photoperiodic effects.

Impact of Climate on Poultry and Livestock Feed

Egg Production in Poultry

Optimal Temperature for Egg Production:

• Poultry's egg production is highest within the thermoneutral temperature range.
• Constant high temperatures negatively affect laying rate, total eggs laid, egg weight, and shell thickness.
• Water deprivation worsens these effects, reducing fertility and hatchability of eggs.
• Light intensity variations do not significantly impact egg production.

Indirect Effects on Livestock

Feed Quantity and Quality:

• Climatic Factors Limiting Plant Growth:
  • Ambient temperature, effective rainfall, daylight length, and solar radiation influence plant growth.
  • Quality depends on effective rainfall and solar radiation intensity.

Climate Differences in Tropical Regions:

• Equatorial and Amid Tropics:
  • Forage growth is continuous and rapid, with heavy annual yields possible.
  • High water content in humid tropical forage may affect total feed consumption.
• Effect on Feed and Water Intake:
  • Forage with high water content in humid climates may impact dry matter intake for ruminant animals.
  • Evidence suggests that water content affects the total quantity of feed consumed.

Effect on Nutrient Content:

• Nutritious Forage in Wet Season:
  • Experimental evidence shows conflicting results, but in general, forage is more nutritious in the wet season.
  • Positive correlation between rainfall and crude protein, silica-free ash, and nitrogen-free-extract content.
  • Inverse relationship between rainfall and crude fiber content.
• Challenges in Humid Tropical Forage:
  • Continuous cloudy weather may slow down growth after the initial rainy season flush.
  • Crude fiber content in humid tropical forage is consistently higher than in temperate forage, posing challenges for animals under heat stress.

Overall Impact on Livestock

• Quantity and Quality of Feed:
  • Climate significantly influences the quantity and quality of available feed for livestock.
  • Other indirect effects include impacts on disease and parasite incidence, as well as storage and handling of animal products.

Challenges in Semi-Arid and Arid Tropics for Livestock Nutrition

1. Characteristics of Semi-Arid and Arid Regions:

• Low and highly variable total rainfall in semi-arid and arid regions.
• Rainy season followed by a long dry period, sometimes interrupted by scattered showers.
• Droughts can extend dry periods, impacting forage growth.

2. Seasonal Nature of Forage Resources:

• Ruminant livestock often rely on standing dry forage for a major part of the year.
• During droughts, they may depend on this type of feed for extended periods.

3. Effect on Feed Intake:

• Forage in arid and semi-arid tropics has high dry matter content throughout the year.
• Adequate supplies of forage allow grazing animals to maintain sufficient dry matter intake.
• Crucial factor is keeping the stocking rate within the carrying capacity of dry season grazings.

4. Effect on Water Intake:

• Cattle need access to free water at all times, with varying water demands among different breeds.
• Bos indicus breeds require less free water than B. taurus breeds in the same environment.
• Water demands of sheep, goats, and camels are lower than those of cattle.
• Water intake of cattle increases during the dry season, but they can acclimatize to some degree of water deprivation.

5. Water Deprivation and Its Effects:

• Water deprivation affects water and feed intake, metabolism, and productivity.
• Cattle restrict dry matter intake when water-deprived, with differences between Bos indicus and B. taurus breeds.
• Higher ambient temperatures intensify the impact of water deprivation on dry matter intake.
• Managing cattle to restrict grazing time during water deprivation may further decrease feed intake.
• Nutritive content of available feed decreases during the advancing dry season, leading to a further decrease in voluntary dry matter intake.
• Some cattle exhibit better-than-expected performance towards the end of the dry season, likely due to their ability to select high-nutrient parts of the forage plant.

6. Behavior of Water-Deprived Sheep and Camels:

• Water-deprived sheep and camels also show selective foraging behavior, choosing parts of the forage plant with higher nutritive value.
• Nitrogen recycling mechanisms may be activated when nitrogen intake is low, helping to maintain body nitrogen levels.
• Severe water deprivation further reduces nitrogen output, enhancing the value of recycling mechanisms.

7. Short-Term and Long-Term Effects:

• Short-term effects of water deprivation on cattle's liveweight can be dramatic, primarily due to loss of body water.
• Long-term effects are less documented, but water deprivation is expected to decrease liveweight gain by reducing feed intake.

Impact on Nutrient Content of Forage

Forage Quality in Arid and Semi-Arid Regions

• Cattle in arid and semi-arid areas often rely on low-nutrient hay for extended periods.
• Indigenous forage plants are not inherently nutritious, and forage is typically consumed when mature.
• Drying out of forage plants increases the stem-to-leaf ratio, further reducing nutrient value.
• Protein content averages between 2 and 4 percent, with low protein digestibility.

Challenges with Parasites and Diseases

Favorable Breeding Environment

• High ambient temperatures and humidities create favorable conditions for internal and external parasites, fungi, and disease vectors.

Impact on Parasites and Disease Vectors

• Internal Parasites:
  • Less significant in semi-arid tropics.
• External Parasites:
  • Remain important, particularly in semi-arid areas.
  • Importance diminishes in very arid regions.

Indirect Effects on Animal Production

Influence of Vegetation on Disease Vectors:

• Type of vegetation in a region affects the incidence of disease-carrying insects.
• Climate has a significant indirect effect on animal production.
• In regions with high rainfall supporting dense bush growth, teetee-fly incidence can make livestock production challenging or impossible.

Impact on Livestock Management

• Example of Mauritius:
  • Climatic conditions favoring Stomoxys spp. in Mauritius make outdoor grazing difficult during certain times.
  • Livestock owners must build expensive housing to protect animals from fly swarms.
• Example of Sudan:
  • Seasonal incidence of biting flies in Sudan greatly influences managerial methods.
  • Livestock management is adapted based on the prevalence of disease-carrying flies.