Salivary crystallization pattern: a possible unconventional tool for timing of insemination and early pregnancy diagnosis in zebu cows

The present study assessed if salivary crystallization pattern (ferning pattern formed as a result of the higher levels of salt content in the dried sample) could be used for estrus detection and for diagnosis of pregnancy/non-pregnancy in dairy cows. Saliva and blood samples were collected from non-pregnant cycling cows (Sahiwal breed; n = 20) on alternate days from the day of estrus till next estrus. Then, all the cows were inseminated and saliva and blood sampling were continued further for a period of 22 d post-insemination. Pregnancy diagnosis was carried out on day 45 post-insemination and eight cows were found to be pregnant. The salivary crystallization pattern and estradiol:progesterone ratio during estrous cycle and during pregnancy were compared among these cows. Six types of salivary crystallization patterns were discerned; distinct patterns such as branch-like, fern-like, fir-like and combinations of these. Fern-like pattern was observed in all the cows on the day of estrus (first measurement day) and furthermore, all of the cows that subsequently became pregnant had fern-like salivary crystallization pattern at the time of insemination. Saliva of all the pregnant cows showed branch-fir type of crystallization pattern on day 16 post-breeding while only 50% of non-pregnant cows showed this pattern on day 16 of estrous cycle. The appearance of fern-like pattern was positively and significantly related to estradiol:progesterone ratio (r = 0.86; P < 0.001). The findings were validated on a separate group of cycling cows (n = 32). We can conclude that salivary crystallization pattern might serve as a non-invasive and cost effective and easy-to-use cow-side tool for estrus detection and early pregnancy/non-pregnancy diagnosis in cows upon validation on a larger sample size.