Assessing influence of rainfall and temperature variability on productionperformance of sahiwal cattle in semi-arid region of Kenya

Abstract

For over 50 years, Sahiwal cattle breed at the National Stud Herd (NSH) has been bred on rain-fed pastures in a semi-arid ecosystem of Kenya. NSH is located in a hotspot of increasing climate change and variability where Sahiwal cattle herd grazed on rain fed pastures has had long exposure spanning over 50 years. It is hypothesized that Sahiwal has been exposed to large intra and inter annual variations in precipitation and temperatures, with significant influence on their survival rates and milk production. Therefore, the objectives of this study were to characterize the extent of variability in monthly rainfall and temperatures, and to determine their influence on survival rates and on milk production of Sahiwal cattle managed at the Naivasha NSH. Records of monthly herd inventory, deaths and milk yields, monthly minimum (Tmin), maximum (Tmax) and mean (Tmean) temperatures and rainfall for a period of 31 years were obtained from the Naivasha NSH. Variability trends in monthly rainfall and temperature were characterized using the coefficient of variation (CV), standardized anomalies, Precipitation Concentration Index (PCI) and moving averages. The trends were determined using Mann-Kendall (MK) trend test while the slope was computed from Sen’s Slope test. The influence of rainfall and temperatures variations on cattle survival rates was determined using logistic regression while the influence on milk yield was determined using multiple regression analysis. Rainfall variability (CV) was larger in short seasons (CV 59.2%) than in long seasons (CV 48.2%) with a high rainfall concentration (PCI) observed in 34% of the years. The trend for mean annual, long and short season rain, Tmin, Tmax and Tmean were -36.5mm, -25.5 mm + 69 mm, 0.017oC, -0.156oC and -0.09oC per decade, respectively. The range of standardized anomalies for annual rainfall and Tmean were -1.58 to +1.63 and -21.53 to 2.54. The Sen’s slope for mean monthly rainfall, Tmin, Tmax and Tmean ranged from -1.36 to 0.76, -0.06 to 0.05, -0.07 to 0.07 and -0.05 to 0.05, respectively.Effects of temperature variability was insignificant on cattle survival, but rainfall variability had a discernable significant trend on the probability of an animal surviving. For every 1oC increase in Tmin and Tmax, monthly milk yield decreased by 1.58kg and 1.17kg, respectively while for every 1 mm increase in monthly rainfall, monthly milk yield increased by 0.07kg. It is concluded that Naivasha NSH has experienced significant intra and inter annual variations in precipitation and temperatures, with significant influence on survival rates and milk production of Sahiwal cattle. It is advisable to implement adaptation strategies that will respond to effects of variability in precipitation and temperature on cattle survival and milk production. These include adjustments in animal husbandry, grazing management feed conservation to improve pasture quality and quantity all seasons.