Changes in Ruminal Fermentation and Growth Performance in Calves After Increasing Ruminal Undegradable Protein at Two...

Area of Science:

• Animal Science
• Dairy Nutrition
• Ruminant Physiology

Background:

• Heifer rearing efficiency relies on timely nutrient provision for optimal growth.
• Rumen-undegradable protein (RUP) is crucial for meeting protein requirements in young ruminants.
• Soybean meal (SBM) is a common protein source, but its RUP content can be modified.

Purpose of the Study:

• To evaluate the impact of the timing of switching to a rumen-undegradable protein (RUP) source on Holstein dairy calf growth and ruminal fermentation.
• To compare the effects of early (day 28) versus later (day 42) introduction of xylose-treated soybean meal (XSBM) in calf starter diets.

Main Methods:

• Thirty-six Holstein female calves were assigned to three dietary groups: SBM from day 28, XSBM from day 28, or XSBM from day 42.
• Diets varied in RUP content (37% vs. 48%) achieved by replacing SBM with XSBM.
• Calves were fed milk, weaned at day 60, and growth performance and ruminal parameters were monitored until day 70.

Main Results:

• Post-weaning (days 61-70), calves fed XSBM diets (XSBM28 and XSBM42) showed significantly greater daily gain and gain-to-feed ratio compared to the SBM28 group.
• XSBM inclusion increased calf height pre- and post-weaning.
• Ruminal pH and butyrate concentrations were higher at weaning in XSBM-fed calves, with lower ammonia-N and total short-chain fatty acids post-weaning.

Conclusions:

• Increasing RUP content by replacing SBM with XSBM in starter diets during the pre-weaning period can enhance growth performance around weaning.
• Introducing XSBM at 42 days of life is as effective as introducing it at 28 days for improving growth outcomes.
• Dietary adjustments in RUP supply can optimize dairy calf development and performance.