I couldn't find the original article, but the Arabic press is reporting on it as well. They say that Israeli authorities are concerned about the possibility of booby-trapped cattle. Also there is the concern of cattle diseases spreading to Israel.Yedioth reports that the slopes of the northern mountain have become inundated with sheep, disturbing soldiers trying to operate there and turning Israel’s toughest Rambos into veritable shepherds. The army believes the sheep are sent across the border by Lebanese and Syrians looking to cause trouble. “It’s reasonable to assume they were sent to this point. We are talking here about a disruption of Israeli sovereignty in an outstanding way. True, we are talking about sheep, but their presence is dangerous.”
Israel complained to the UN about the violation of its border, and (according to the report) warned that they would be forced to quarantine the sheep if nothing is done.
The Arabic press, apparently seriously, says that Israel will imprison the sheep and that this is another example of "Israeli repression that knows no bounds."