This is a relevant question to ask. This stuff is hard and it takes a lot of oversight to make it work. But that doesn't mean that we should assume every charity is producing negative consequences which outweigh the good they do. That would be just as naive as assuming charities have no negative consequences.

For what it's worth, Heifer International has released quite a few detailed reports on their projects which you can review here: (http://www.heifer.org/ending-hunger/our-impact/reports.html). If you're satisfied, maybe consider giving. If not, and you're qualified to offer a contrary explanation, please share it.

But assuming a negative impact without reviewing their approach is a perfect example of what has come to be known as "middlebrow dismissal". "Charities can have negative consequences which outweigh their good, this is a charity, therefore it has negative consequences which outweigh its good" is not a valid argument. The propensity of charities to produce negative unintended consequences is a sign to be careful, but not sufficient proof to dismiss charities outright.

Note that Charity Navigator gives Heifer International a nearly perfect score on Transparency and Accountability. (http://www.charitynavigator.org/index.cfm?bay=search.summary...)