"My first time ever..." joke

The sky was dark, the moon was high;
All alone, just her and I.
Her hair was so soft; her eyes so blue,
I knew just what she wanted to do.
Her skin so soft; her legs so fine,
I ran my fingers down her spine.
I didn't know how, but I tried my best;
I started by placing my hands on her breast.
I remember my fear, my fast beating heart;
But slowly she spread her legs apart.
And when I did it I felt so shame;
All at once the white stuff came.
At last it's all finished; it's all over now,
My first time ever at milking a cow.