Question

Given below are two statements: one is labelled as Assertion A and other is labelled as Reason R
Assertion A: Colostrum contains high percentage of Immunoglobulins, growth hormones and lactoferrin
Reason R: Immunoglobulins are important for the immunity of newborns
In the light of the 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 and 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:

Colostrum Immunity: Calves are born agammaglobulinemic (no placental antibody transfer) $\rightarrow$ Colostrum provides PASSIVE IMMUNITY via high Immunoglobulins (IgG1).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Immunological role of bovine colostrum: because the synepitheliochorial placenta prevents in utero transfer of maternal antibodies, colostrum concentrates massive levels of Immunoglobulins (IgG1, 6--10%) to provide critical passive systemic immunity to the agammaglobulinemic newborn calf.
Key Formula or Approach:
\[ \text{Synepitheliochorial Placenta (No in utero Ab transfer)} \implies \text{Calf born Agammaglobulinemic} \xrightarrow{\text{Colostrum IgG}} \mathbf{Passive \text{ } Systemic \text{ } Immunity} \]

Step 2: Detailed Explanation:
1. Assertion A: First-milking bovine Colostrum contains exceptionally high concentrations of Immunoglobulins ($60 - 100\text{ g/L}$, predominantly IgG1, IgG2, IgM, IgA), along with insulin-like growth factors (IGF-1, IGF-2), growth hormone, and antimicrobial Lactoferrin. Hence, Assertion A is true.
2. Reason R: In ruminants, the thick six-layered synepitheliochorial placenta prevents any transplacental transfer of maternal antibodies to the fetus during gestation; calves are born completely agammaglobulinemic (immunologically naive). Ingestion of colostral immunoglobulins during the first 24 hours of life (prior to gut closure) is critically indispensable for establishing passive systemic humoral immunity in the newborn calf to survive neonatal pathogens.
- Therefore, Reason R is true and provides the direct biological explanation for Assertion A.

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