What of the followings could be called as 'True growth' of calf... | Agrigyan

Heifer rearing and breeding benchmarks:

• Target weight at first breeding in crossbred heifers: In India, crossbred heifers (e.g. Karan Swiss, Karan Fries, Frieswal) are recommended to be bred when they attain approximately $250\text{ to }275\text{ kg}$ body weight (about $60\%\text{ to }65\%$ of mature body weight, typically at $15\text{ to }18\text{ months}$ of age). A weight of $300\text{ to }350\text{ kg}$ is too high for first service of Indian crossbred heifers and represents post-calving or pure exotic standards. Therefore, Statement (I) is incorrect.
• Role of nutrition: Growth rate, onset of puberty, and skeletal dimensions are primarily governed by the plane of nutrition rather than chronological age alone. Balanced feeding accelerates puberty. Therefore, Statement (II) is correct.
  
  Option analysis:
  Statement (I) is incorrect but Statement (II) is correct, matching Option 4 (Key 4).

Signs of estrus in bovines:

• Heifer in estrus: Estrus produces elevated systemic estrogen, causing intense behavioral restlessness, increased locomotion, reduced rumination, and early wakefulness, standing alert and restless while herdmates are resting. Thus, Statement (I) is correct.
• Estrus in buffaloes: Buffaloes are notorious for 'silent heat' with weak overt vocalization and mucus discharge; therefore, 'standing heat' (willingness to stand firmly when mounted by a teaser bull or another female) is the most reliable, definitive behavioral sign for insemination timing. Thus, Statement (II) is correct.
  
  Option analysis:
  Both Statement (I) and Statement (II) are correct, making Option 1 the correct answer (Key 1).

Concept and benefits of Steaming-up in dairy cows:

• Definition: Steaming-up refers to the practice of providing an incrementally increasing concentrate ration to pregnant cows/heifers during the last $2\text{ to }3\text{ weeks}$ prior to parturition. Statement (I) is correct.
• Benefits: It replenishes maternal body reserves, acclimates rumen microflora and papillae to high-concentrate diet, builds nutrient pools for colostrum synthesis, supports rapid attainment of peak lactation, extends lactation persistency, and supports high milk fat content. Statement (II) is correct.
  
  Option analysis:
  Both Statement (I) and Statement (II) are correct, matching Option 1 (Key 1).

Principles of hygienic milking management:

• Regularity: Dairy animals are creatures of conditioned reflex and habit; milking should always be done at fixed intervals and times. Option 1 is correct.
• Milk let-down reflex: Teat/udder stimulation releases oxytocin from posterior pituitary, causing alveolar myoepithelial contraction within $45\text{ to }60\text{ seconds}$ ($1\text{ minute}$). Option 2 is correct.
• Duration: Effective circulating half-life of oxytocin is only $1\text{ to }2\text{ minutes}$, and let-down subsides within $5\text{ to }7\text{ minutes}$; hence milking must be completed in $5\text{--}7\text{ minutes}$. Option 3 is correct.
• Feeds during milking: Dusty, husky, or strong-smelling feeds (silage, onion/garlic residues) should never be offered during milking because dust contaminates milk and volatile flavors enter milk. Option 4 is wrong/irrelevant and therefore the correct answer.
  
  Option analysis:
  Option 4 is a bad management practice that contaminates clean milk production.