Quantifying production losses associated with foot and mouth disease outbreaks on large scale dairy farms in Nakuru County, Kenya

Abstract

Foot and Mouth Disease (FMD) is a contagious viral disease to which dairy cattle are highly susceptible. An outbreak of FMD in a dairy herd can cause drop in milk yield, increase mastitis infections, force culling, and impair fertility. These production losses can be substantial, but farmers undervalue the magnitude of the loss that they incur. To fill this knowledge gap, the study quantified the association of FMD outbreak with milk yield, mastitis incidences, culling rates and fertility impairments. Data was collected retrospectively from three large-scale dairy farms with a recent history (2008 to 2018) of FMD outbreaks in a region endemic for prevalence of serotype C of the FMD virus since mid-1980s in Nakuru County, Kenya. Records for a total of 507 cows were obtained from three farms for three consecutive periods of six weeks before, during and after FMD outbreaks. Data analysis used general linear model fitting the period of disease outbreak (six weeks before, during and after), farm and breed to explain change in milk production at the herd level. Logistic regression was used for cases of mastitis, culling and fertility impairments, in the three periods of FMD outbreak. The odds ratio was also used to compare between the three phases of FMD outbreaks (before, during, after). Relative to the period before and after FMD, production losses were marked during the outbreak. Disease outbreak was associated with up to 4.7% of the cows drying off (n=24) and milk production (111,466.52 ± 2201.21 Kg) dropped by 16.1% (93,476.32 ± 2181.65). The incidences of mastitis increased from 5.4% to 21.5% (Odd ratio=3.31, Confidence interval =2.27, 4.83) and culling rates increased from 0.59% to 3.8% (OR = 6.71, CI =1.99, 22.58). Incidences of abortion during FMD increased by 1.99% (OR=6.33, CI =2.34, 17.13) compared to the period prior FMD outbreak, retained placenta during FMD increased by 3.03 (OR=7.29, CI=0.88, 59.9) but conception failures marginally declined from 0.39% to 0.21% during FMD. The results suggest that FMD outbreak leads to substantial production losses: Milk production drops substantially and the recovery after the outbreak is slow. Mastitis incidences during FMD increased by 16.1% compared to the period before FMD. While both voluntary and involuntary cow exits increased 3.17% during the outbreak with comparison to the period prior FMD. Fertility is impaired while conception failure was increased the post outbreak period.