(challenge of city board of adjustment decision that challenger’s neighbors have existing, nonconforming animal rights use to keep cattle on their property due to use since 1970; appellate court found challenger failed to meet his burden of proof and marshal evidence; sufficient evidence existed to support board’s decision; challenger also failed to preserve issues at board hearing, so not addressed at appellate level; court also upheld district court order allowing neighbors to intervene in challenger’s action against city; board decision affirmed).