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Environmental variation effects fertility in tropical beef cattle
James P Copley1, Bailey N Engle1, Elizabeth M Ross1
1Centre for Animal Science, Queensland Alliance for Agriculture and Food Innovation, St Lucia, QLD 4072, Australia.
Translational Animal Science
|May 9, 2022
Summary
Environmental heat load, not acute heat stress, significantly impacts beef cattle fertility in northern Australia. Optimizing weight gain and managing chronic heat exposure are key for reproductive success in extensive farming systems.
Area of Science:
- Animal Science
- Reproductive Biology
- Environmental Science
Background:
- Northern Australian beef cattle face harsh environmental conditions suppressing female fertility.
- Understanding environmental impacts on extensive cattle farming is crucial for industry sustainability.
Purpose of the Study:
- To define environmental descriptors for cattle herds in northern Australia.
- To investigate the effects of environmental factors on key fertility traits in beef cattle.
Main Methods:
- Defined environmental descriptors for 54 commercial herds.
- Recorded three fertility traits: puberty (CL Presence), heifer pregnancy, and first lactation pregnancy.
- Utilized publicly available temperature, humidity, and rainfall data.
Main Results:
- Early puberty (CL Presence at 600 days) increased heifer and first lactation pregnancy rates.
- Temperature Humidity Index (THI) of 65-70 negatively affected all fertility traits.
- Chronic heat load (Area Under Curve of daily THI) reduced puberty and first lactation pregnancy.
- Average daily weight gain positively correlated with heifer and first lactation pregnancy.
Conclusions:
- Chronic heat load is more detrimental to beef cattle reproductive performance than acute heat stress.
- Average daily weight gain and chronic heat load are suitable descriptors for environmental gradients affecting fertility.
- Managing cumulative heat exposure and promoting adequate weight gain are vital for improving cattle fertility in northern Australia.
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