Milk yield did not decrease in large herds of high-producing Holstein cows in semi-arid climate of Mexico.

Area of Science:

• Animal Science
• Dairy Production
• Environmental Physiology

Background:

• Dairy farming in northern Mexico faces environmental challenges.
• Understanding trends in milk production, fertility, and environmental factors is crucial for sustainable dairy operations.

Purpose of the Study:

• To analyze trends in milk production, fertility, temperature-humidity index (THI), and herd size in Mexican dairy herds.
• To investigate the impact of THI on milk production and fertility in Holstein cows.

Main Methods:

• Utilized 16 years of data (2002-2016) from 16 Holstein dairy herds in northern Mexico.
• Employed generalized equation estimation and generalized linear models to analyze milk production, fertility, and THI trends.
• Categorized milk production into low and high levels for comparative analysis.

Main Results:

• Milk production increased from 27.4 L/cow/day in 2002 to 32.3 L/cow/day in 2016.
• Higher milk production levels correlated with increased fertility (P < 0.001).
• Cows experienced heat stress (THI > 73) for 20 hours daily from May to September, leading to decreased milk production and fertility.

Conclusions:

• Large dairy herds in the region demonstrated increased milk production over time.
• Fertility exhibited cyclical fluctuations but was negatively affected by heat stress.
• Managing heat stress is critical for maintaining milk production and fertility in dairy cows.