(debtors' Chapter 13 plan confirmed over creditor's argument that plan not feasible because debtors' projected income from cattle sales speculative due to condition of cattle herd; creditor failed to identify any objective fact clearly establishing that bankruptcy court erred in determining that plan was feasible based on debtors' projections; plan permissibly modified creditor's default remedies and plan does not "bifurcate" the claim into secured and unsecured portions).