Straw particle size in calf starters: Effects on digestive system development and rumen fermentation

Area of Science:

• Animal Science
• Ruminant Nutrition
• Digestive Physiology

Background:

• Calf starter diets are crucial for rumen development.
• Straw particle size is a key physical characteristic influencing rumen function.
• Understanding the impact of straw particle size on early rumen development is essential for optimizing calf nutrition.

Purpose of the Study:

• To investigate the effects of varying straw particle sizes in calf starter on rumen fermentation and development.
• To determine if altering straw particle length influences key digestive parameters in young calves.

Main Methods:

• Two trials involving Holstein calves fed milk replacer and a starter containing 5% straw.
• Straw particle sizes varied (0.82 mm to 12.7 mm geometric mean particle length).
• Rumen fermentation parameters and digestive organ development were assessed at 6 weeks post-starter introduction.

Main Results:

• Rumen pH decreased and volatile fatty acid concentration increased with age, independent of diet.
• Dietary straw particle size did not significantly alter volatile fatty acid proportions or rumen papillae development.
• Omasum weight as a percentage of body weight decreased linearly with increasing straw particle size.

Conclusions:

• Modifying straw particle length in calf starter has minimal effects on rumen fermentation and development.
• Age-related changes in rumen pH and fermentation are likely driven by increased starter intake.
• Straw particle size may influence omasum development, warranting further investigation.