Validation of salivary ferning based estrus identification method in a large population of water buffaloes (Bubalus bubalis) using Foldscope.

Missing an estrus event is an economic problem in buffaloes because of lack of a simple and accurate estrus identification method. Saliva, a non-invasive fluid available every time, showed typical fern-like crystallization patterns at early estrus in buffaloes. However, to implement this salivary ferning based estrus identification method in the field conditions, the present study, for the first time, validated this method in four buffalo population samples (PS) representing four different field scenarios, an organized herd (PS1, 10 buffaloes monitored daily for a year (149 estrus events)), artificial insemination (AI) centers (PS2, 114 buffaloes brought for AI), induced estrus condition (PS3, 44 buffaloes) and farmers' doorsteps (PS4, 275 random buffaloes with unknown reproductive history and no estrous signs). Totally, 582 saliva samples were collected from 443 buffaloes. Salivary smears were observed under a simple microscope and/or a less expensive (< 1USD) paper microscope, Foldscope. On the basis of salivary fern-like patterns, the proportions of estrus identification were significantly different among PS. Specifically, the proportions in the PS1 (0.74, P < 0.0001) and PS4 (0.08, P < 0.05) were significantly higher than their population proportion estimates, 0.5 and zero, respectively. Therefore, this estrus identification method is much useful in the PS1 and PS4, the practical field scenarios requiring an accurate estrus prediction method, compared to the PS2 and PS3. Especially, this method is 91 % confirmatory to detect early estrus in PS4. Therefore, salivary ferning is a useful technique to identify early estrus in buffaloes in the field conditions at farmers' doorsteps.