Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Compared to urea, lactosyl urea can be safely fed to cattle
Reason R: Urease cannot breakdown lactosyl urea
In the light of above statements choose the correct answer from the options given below:

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true but R is NOT the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Hint:

Slow-Release NPN in Ruminants: LACTOSYL UREA is safe because RUMINAL UREASE CANNOT BREAK IT DOWN directly, preventing ammonia toxicity and providing sustained NPN for microbial protein synthesis.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Non-protein nitrogen (NPN) technology in ruminant nutrition: lactosyl urea (lactose-urea condensation product) releases ammonia slowly in the rumen because bacterial urease cannot hydrolyze the covalent glycosyl-urea bond, preventing acute rumen ammonia toxicity.
Key Formula or Approach:
\[ \text{Free Urea} \xrightarrow{\text{Rapid Urease Hydrolysis}} \text{Ammonia Spike } (\text{Risk of Toxicity}) \quad \longleftrightarrow \quad \mathbf{Lactosyl \text{ } Urea} \xrightarrow{\text{Resistant to Urease}} \mathbf{Slow, Safe \text{ } NH}_3 \text{ Release} \]

Step 2: Detailed Explanation:
1. Assertion A: Feeding pure crystalline urea to ruminants carries a severe hazard of acute ammonia toxicity (hyperammonemia) due to explosive rapid hydrolysis by ruminal bacterial urease. Lactosyl Urea (a slow-release NPN compound synthesized by condensing whey lactose with urea) can be safely fed to cattle without any risk of ammonia poisoning. Hence, Assertion A is true.
2. Reason R: The ruminal enzyme Urease cannot directly breakdown or hydrolyze the glycosidic bond of Lactosyl Urea. Instead, lactosyl urea requires slow preliminary enzymatic cleavage of the lactose sugar moiety by microbial $\beta$-galactosidases before urea is gradually released at a controlled rate synchronized with carbohydrate fermentation. Hence, Reason R is true and correctly explains Assertion A.

Step 3: Final Answer:
Therefore, Both A and R are true and R is the correct explanation of A, matching option (A).