Mention the signs of estrus in cattle and buffaloes. What is the time of insemination for better conception in these animals and why is it so?

Signs of Estrus in Cattle and Buffaloes

The manifestation of estrus involves a combination of behavioral and physical signs. While cattle generally exhibit pronounced signs, buffaloes are known for their less overt or "silent" estrus, making detection more challenging.

1. Behavioral Signs:

• Standing to be Mounted: This is the most definitive and reliable sign of estrus in both cattle and buffaloes. The female stands still and allows other animals (cows, buffaloes, or a bull) to mount her.
• Mounting Other Animals: Estrus animals may show homosexual behavior by mounting other cows or buffaloes.
• Increased Activity and Restlessness: Animals in heat often become more active, walk around frequently, and appear nervous or excitable.
• Bellowing or Bawling: Frequent vocalization is common during estrus.
• Frequent Urination: Animals may urinate more often than usual.
• Chin Resting and Back Rubbing: Cows may rest their chin on the rump of another animal, often followed by an attempt to mount.
• Seeking a Bull/Herd Mates: The animal may actively seek out the presence of a bull or other animals.
• Reduced Appetite and Milk Production: A temporary drop in feed intake and milk yield can be observed.

2. Physical Signs:

• Swollen and Reddened Vulva: The external genitalia become swollen, relaxed, and appear reddened (bright cherry pink color).
• Clear, Stringy Mucus Discharge: A characteristic discharge of clear, watery, and often stringy mucus (ropy mucus) from the vulva. This mucus may hang from the vulva or be smeared on the tail and hindquarters.
• Ruffled or Missing Hair at Tail Head/Dirty Flanks: Due to repeated mounting by herd mates, the hair at the tail head may appear ruffled, rubbed, or even missing, and the flanks may be smeared with mud or manure.
• Metestrous Bleeding: Some cows, and especially heifers, may show a bloody mucus discharge 1-3 days after estrus, though this is a post-estrus sign and not an indicator for insemination timing.

Differences in Estrus Expression:

While the general signs are similar, the intensity varies significantly:

Feature	Cattle (Cows)	Buffaloes
Overtness of Signs	Generally pronounced and easily observable.	Less overt, often described as "silent heat," making detection challenging.
Standing to be Mounted	Most reliable and frequently observed primary sign.	Most reliable, but homosexual behavior is rare; standing for a bull is more common.
Peak Activity Time	Can occur throughout the day, often between midnight and 6 am.	Generally commences late evening, with peak sexual activity during hours of darkness.
Mucus Discharge	Clear and abundant.	Present but may be less visible or copious.
Vocalisation (Bellowing)	More common and louder.	Less frequent or intense.
Silent Estrus	Less common, though it can occur.	A significant challenge, especially in certain seasons (e.g., summer).

Time of Insemination for Better Conception and its Rationale

The accurate timing of insemination is critical for maximizing conception rates because the lifespan of viable sperm and the fertile window of the ovum are limited. The goal is to ensure that fertile sperm are present in the oviduct when the freshly ovulated egg arrives.

Optimal Timing:

For both cattle and buffaloes, the optimal time for artificial insemination is generally considered to be 12 to 18 hours after the onset of standing estrus. This recommendation is often encapsulated by the "AM/PM rule."

The AM/PM Rule:

• If an animal is observed in estrus (standing heat) in the morning (AM), it should be inseminated in the evening (PM) of the same day.
• If an animal is observed in estrus (standing heat) in the evening (PM), it should be inseminated in the morning (AM) of the following day.

Why this Timing is Optimal:

This timing strategy is based on the physiological events of the estrous cycle and the reproductive biology of these animals:

1. Ovulation Time:
   • In cattle, ovulation typically occurs 24 to 32 hours after the onset of standing heat, or approximately 10-14 hours after the end of standing heat.
   • In buffaloes, ovulation generally occurs 24-48 hours (mean 34 hours) after the onset of estrus.
   • Inseminating 12-18 hours after the onset of estrus ensures that sperm are already in the reproductive tract and ready for fertilization when ovulation occurs.
2. Sperm Capacitation:
   • Spermatozoa introduced into the female reproductive tract require a period of physiological maturation called capacitation before they can fertilize an egg. This process takes several hours (typically 4-6 hours).
   • By inseminating before ovulation, sufficient time is allowed for sperm to undergo capacitation and reach the site of fertilization in the oviduct.
3. Viability of Sperm and Egg:
   • Sperm Viability: After deposition, viable sperm can survive in the female reproductive tract for approximately 24-30 hours, though their fertilizing capacity might be shorter.
   • Egg Viability: The ovulated egg (oocyte) has a much shorter fertile lifespan, typically 6-12 hours post-ovulation. If insemination is too late, the egg may have degenerated or lost its fertilizing ability.
4. Meeting at the Right Time and Place:
   • The optimal timing ensures that a population of capacitated sperm is present in the oviduct to meet a freshly ovulated, highly viable egg. This synchronicity maximizes the chances of successful fertilization and subsequent embryo development.
   • Inseminating too early might lead to sperm dying before the egg is released, while inseminating too late means the egg may no longer be viable.