Foot and Mouth Disease May Skew Secondary Sex Ratio in Cattle

Objective: The study was conducted with single objective, to understand effect of foot and mouth disease (FMD) on secondary sex ratio (SSR) in dairy animals including cattle (Bos indicus, Tharparkar; Bos indicus + Bos taurus, Vrindavani) and Murra buffalo (Bubalus bubalis) maintained at Indian Veterinary Research Institute, Izatnagar. Design: Retrospective data for six years of IVRI, Izatnagar Dairy farm having an average population of about 1000 livestock was analyzed for sex-specific calf birth, abortions, still births and mortality were assessed with reference to the FMD outbreak years and non-FMD outbreak years. In the study period, two FMD outbreaks were recorded one in 2010 June (due to FMD virus type”O”) and other in January 2016 (due to FMD virus type ”A”). Results: In years of FMD outbreak (2010-11 and year 2015-16), there were no biases of the disease towards sex and breed of the affected animals. However, FMD lesions were more apparent in calves and young stocks of Vrindavani strain. In years of FMD outbreaks on the farm male calf births were significantly more than female calf births (in 2010-11, male: female:: 1.34: 1.0, p= 0.067, and in 2015-16, male: female :: 1.624: 1.0, p= 0.004). Male calf births were a little higher in 2015-16 (p= 0.096) than in the year 2010-11. The change in SSR was more apparent in Vrindavani cattle with significantly higher male birth odds (1.34, p= 0.171). Conclusions: The FMD affected all susceptible animals during an outbreak on a dairy irrespective of age, sex, and breed of animals but skewed SSR in favour of males. The study indicated that FMD virus infection altered the SSR in favour of males depending on the type of the virus and breed of the animal affected.