Animation using quiver

I am trying to animate the flow of vectors using quiver. However, I am not able to successfully generate what I am looking for. I use the following code

p = quiver(zeros(N), zeros(N), gradient=(zeros(N),zeros(N)))
anim = Animation()
for t = 1:1:501
    push!(p,x[t,:],y[t,:],vx[t,:],vy[t,:])
    frame(anim)
end

The push! function does not let me insert the gradient keyword and hence, I dont get the desired plot.