Veterinary Physiology-III

HORMONES

Progesterone assay

• Most widely used method of pregnancy diagnosis in farm animals.
• Progesterone can be detected in blood and milk.
• Its level declines in non-pregnant animals. Samples are collected at 22 to 23 days in cows, 17 to 18 days in ewes and 21 days in sows.
• P4 level at this time is low in non-pregnant animals and elevated in pregnant animals.
• Milk can be used for detecting P4.
• These methods are accurate but expensive,
• Require laboratory facilities and results can be known after some days.
• One step qualitative “cow-side” test kits are available which overcome these shortcomings.
• Elevated levels of progesterone do not necessarily signify pregnancy.
• In longer than normal oestrous cycle length, progesterone level would be high on the day of sampling (22 days) indicating “false positive” result.
• In early embryonic mortality, false positive result may be obtained.
• Accuracy of predicting pregnancy with progesterone assay ranges from 70 to 90% and the accuracy of detecting nonpregnancy is 100%, because a cow with low progesterone is not pregnant. Hence, blood/milk progesterone assay is more reliable to diagnose nonpregnancy at a much earlier time.

Oestrone Sulphate

• It is the major estrogen produced by the conceptus
• Can be measured in the maternal blood, milk or urine in all farm animal species
• Estrone sulphate is detectable in the plasma earlier in sow (day 20), and mare (day 40), than in sheep and goat (day 40 to 50) and cow (day 72).
• In pigs, estrone sulphate test has more advantages than other methods.
• It is more accurate in earlier pregnancy than ultrasonagraphy.

Gonadotrophins

• eCG appears in the blood of mares at 40 days of conception, reaches a peak between 50 and 120 d and then gradually declines and pregnancy can be diagnosed using eCG.