Personalized Tractor Farmer Cow 13th Birthday Youth T-Shirt. Celebrate your little one's special day with our Tractor Farmer Cow 13th Birthday apparel and gifts! Our selection of unique and creative birthday products are sure to make your kids, babies, and children smile. Let the good times roll in a durable T-Shirt that takes kids from school to play in an amazing array of colors. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar.