Rumen function and grazing behavior of early-lactation dairy cows supplemented with fodder beet.

Area of Science:

• Animal Science
• Ruminant Nutrition
• Dairy Production

Background:

• Fodder beet (FB) provides fermentable carbohydrates for dairy cows but can cause subacute ruminal acidosis (SARA).
• SARA impairs rumen function and limits milk production responses to supplements in early lactation dairy cows.

Purpose of the Study:

• To investigate the effects of fodder beet supplementation on rumen function, grazing behavior, and milk production in early lactation dairy cows.

Main Methods:

• Eight Holstein Friesian × Jersey cows were assigned to a crossover experiment comparing grazed perennial ryegrass herbage with or without 6 kg DM/d of FB bulb.
• Rumen function was assessed via digesta sampling, volatile fatty acid analysis, and in sacco dry matter disappearance.
• Grazing behavior and rumination time were monitored.

Main Results:

• Fodder beet supplementation did not alter dry matter intake, milk yield, or milk solid production.
• Supplementation reduced ruminal pH, increasing the risk of subacute ruminal acidosis.
• Rumen volatile fatty acid profiles shifted, with increased butyrate and lactate, and decreased acetate and ammonia.
• Rumination and grazing time increased, while grazing intensity declined with FB supplementation.
• In sacco dry matter disappearance of ryegrass herbage decreased with FB supplementation.

Conclusions:

• Fodder beet supplementation increases rumination and mastication in grazing dairy cows.
• Despite increased chewing, FB supplementation reduces ruminal degradation of ryegrass herbage due to low ruminal pH.
• FB supplementation did not enhance milk production and poses a risk of subacute ruminal acidosis in early lactation dairy cows.