Comparative digestibility by cattle versus sheep: effect of forage quality

Area of Science:

• Animal Science
• Nutritional Biochemistry

Background:

• Ruminant species differ in digestive physiology, impacting forage utilization.
• Understanding species-specific responses to forage quality is crucial for animal nutrition and feed evaluation.

Purpose of the Study:

• To compare the apparent total tract digestibility and ruminal fermentation of cattle and sheep fed varying forage qualities.
• To determine if sheep are an adequate model for cattle when assessing forage digestibility across different quality levels.

Main Methods:

• Five steers and five wethers were fed three forage types: alfalfa hay, warm-season grass hay, and lovegrass hay.
• Apparent total tract digestibility, ruminal fermentation parameters (VFA, NDF disappearance), and ruminal fill were measured.
• A 2x3 factorial arrangement with species and forage source as factors was used.

Main Results:

• Intake was more influenced by forage quality than species. Cattle consumed more nutrients per metabolic body weight than sheep.
• Digestibility was similar for moderate-quality forages but lower in sheep for low-quality lovegrass hay.
• Ruminal NDF disappearance and fill were influenced more by forage type than by ruminant species.

Conclusions:

• Sheep are not an adequate model for cattle when evaluating the digestibility of low-quality forages.
• Species-specific differences in digestibility become more pronounced with lower-quality forages.
• Digestibility expressed as digestible intake per unit of body weight may allow for broader comparisons between species.