Efficacy of monensin for beef cows

Area of Science:

• Animal Science
• Ruminant Nutrition
• Beef Cattle Production

Background:

• Optimizing feed efficiency is crucial for beef cow-calf operations.
• Monensin, an ionophore, is known to alter rumen fermentation.
• Understanding monensin's effects on late gestation and early lactation is vital for producers.

Purpose of the Study:

• To evaluate the impact of monensin supplementation on feed intake and efficiency in beef cows.
• To assess monensin's effects on cow body condition, calf performance, and reproductive outcomes.
• To investigate monensin's influence on rumen volatile fatty acid profiles and blood metabolites.

Main Methods:

• Beef cows were supplemented with monensin at 50, 200, or 300 mg/day during late gestation and early lactation.
• Feed intakes were adjusted to maintain similar changes in cow weight, condition scores, and weight-to-height ratios over 168 days.
• Rumen and blood samples were collected prepartum and postpartum to analyze fermentation and metabolic parameters.

Main Results:

• Monensin supplementation resulted in significant feed savings, ranging from 3.2% to 13.5% with increasing dosage.
• No adverse effects were observed on calf birth weights, 205-day weaning weights, or first-service conception rates.
• Monensin increased propionate proportion and the acetate-to-propionate ratio in prepartum rumen samples, with no significant postpartum changes.

Conclusions:

• Monensin effectively improves feed efficiency in beef cows during late gestation and early lactation.
• Monensin supplementation does not compromise calf performance or reproductive efficiency in beef cows.
• Monensin alters rumen fermentation patterns, particularly prepartum, without negatively affecting key blood metabolites.