Wheat Stubble from Conventional or Conservation Agriculture Grazed by Ewes: Biomass Dynamics and Animal Performances

Abstract

This experiment aimed to determine the effect of stocking rates and cropping systems (conventional agriculture; Conv A vs. conservation agriculture; Cons A) on biomass dynamics and animal performance parameters of ewes grazing on wheat stubble. Forty Barbarine ewes were divided into eight homogeneous groups and allotted equally to the two cropping systems. Two stocking rates of 15 (SR15) and 30 (SR30) ewes/ha were tested for each cropping system, during a period of 60 d. Stubble biomass and BW variations were monitored at periodic intervals. Blood was sampled thrice during the study period at 15 d intervals. Results showed that the stubble biomass exhibited a gradual decrease (P<0.0001) with the progression of the duration by margins of -85.6 and -81.3% on DM basis, respectively, in Conv A and Cons A, as compared to initial biomass. Further, the biomass was also significantly (P=0.03) affected by the cropping system with a higher value in Conv A than Cons A. The variations in biomass chemical composition showed that the CP content decreased (P<0.0001) with advancing of period, while that of ADF increased (P<0.0001). Additionally, there was a significant effect (P=0.0002) of cropping mode evident in the nutritional composition. Overall, the animals maintained their average BW between the beginning (47.16 kg) and the end (47.36 kg) of the experiment. The blood parameters measured were well within the ranges of normal values for sheep. The stocking rates did not show impact on any of the parameters, with the values being generally similar between stocking rates and cropping systems. It is concluded that while the stocking rate had no effect on the measured variables, conservation agricultural system seemed to keep a higher proportion of residual biomass at the end of the experiment as compared to conventional agriculture.