Amazon offers Select Amazon accounts: 25% Off Select Purina Pro Plan Dog & Cat Food when you 'clip' the coupon on the product page and check out via Subscribe & Save. Shipping is free w/ Prime or on $25+ orders.
Note, you may cancel Subscribe & Save any time after your order ships. Coupons are typically one-time use. The coupon may be targeted.
Look for items marked "25% off your first subscription order")