Introduction

Heat stress is a critical challenge for the dairy industry in Pakistan. This is especially true during the intense summer season. With ambient temperatures regularly exceeding 40°C, lactating animals experience a significant drop in feed intake. The high relative humidity often above 60% further impacts their milk yield and overall health. In recent years, nutritional strategies—particularly the supplementation of glucose precursors—have shown promise in alleviating the effects of heat stress. This article examines how glucose precursors maintain energy balance. They help improve milk production. These precursors also enhance animal welfare in heat-stressed dairy animals in Pakistan.

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Understanding Heat Stress and Its Impacts

Heat stress occurs when the heat load on the animal exceeds its ability to dissipate it. This leads to:

• Reduced dry matter intake (DMI)
• Negative energy balance (NEB)
• Decline in milk yield and quality
• Impaired immune function and reproductive performance

The University of Veterinary and Animal Sciences (UVAS), Lahore, conducted a study. It found that dairy cattle exposed to heat stress during peak summer months showed a 15-25% decline in milk yield. They also experienced a reduction in feed intake of up to 30%.

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The Role of Glucose Precursors

Glucose precursors like propylene glycol, glycerol, and calcium propionate are used to support energy metabolism in dairy cows. These compounds are fermented in the rumen to produce propionate. It is a volatile fatty acid (VFA). Propionate is the primary gluconeogenic substrate in ruminants.

Benefits in Heat Stress Management:

1. Improved Energy Balance
   During heat stress, cows enter a state of NEB due to reduced DMI. Glucose precursors help generate glucose without increasing heat increment, thus supplying critical energy needed for lactation.
2. Stabilized Milk Yield
   A 2022 field trial was conducted in Punjab. Researchers reported that supplementation with propylene glycol (300 mL/day) in early-lactation cows during summer improved average milk yield by 2.5 liters/day compared to non-supplemented controls.
3. Enhanced Rumen Role
   Glucose precursors support rumen microbial activity, which is often compromised during heat stress. Improved rumen operation helps preserve digestion and nutrient absorption.
4. Reduced Incidence of Metabolic Disorders
   Glucose precursors have been shown to reduce subclinical ketosis. They also help mitigate fatty liver. These conditions are exacerbated during periods of heat-induced NEB.

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Research Data from Pakistan and Similar Climates

• UVAS (2021): In a controlled study, cows receiving propylene glycol during summer had 17% higher blood glucose levels. They also had 22% lower non-esterified fatty acid (NEFA) concentrations. This indicates a better energy profile.
• NIAB Faisalabad (2023): A trial on 50 crossbred cows supplemented with calcium propionate during June-August showed higher average milk fat % (3.9 vs 3.2) and lower respiration rates, suggesting improved thermal tolerance.

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Application in the Pakistani Dairy Sector

Pakistan has a large population of small- to medium-scale dairy farms. Glucose precursors offer an economical and scalable solution for managing heat stress. Recommendations include:

• Supplementation Rates:
  • Propylene glycol: 200–300 mL/day
  • Glycerol: 250–500 mL/day
  • Calcium propionate: 200–300 g/day
• Feeding Method:
  • Top-dressed on feed
  • Mixed into Total Mixed Ration (TMR)
  • Drenched in high-risk animals (fresh calvers, high producers)
• Timing: Best results occur when supplementation begins early in the summer. Supplementation during peak lactation also shows efficacy in preventing the onset of NEB.

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Conclusion

Heat stress significantly hampers dairy productivity in Pakistan’s hot climate. Incorporating glucose precursors into summer feeding programs offers a science-backed, practical solution to this challenge. Glucose precursors support energy metabolism. They improve milk yield and enhance animal comfort. Glucose precursors can be a key part of sustainable dairy production in Pakistan.

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References

1. UVAS Lahore, Dept. of Animal Nutrition (2021). Effects of Glucose Precursors on Heat-Stressed Dairy Cattle.
2. National Institute for Agricultural Biology (NIAB), Faisalabad (2023). Calcium Propionate as a Heat Stress Mitigating Agent.
3. West, J.W. (2003). Effects of Heat-Stress on Production in Dairy Cattle. Journal of Dairy Science, 86, 2131–2144.
4. Khan, N. et al. (2022). Nutritional Strategies for Enhancing Dairy Cattle Performance during Heat Stress in South Asia. Pak Vet J, 42(1), 19–25.