Gelatin zymography to determine the difference between non-pregnant and pregnant pigs at 60 days post artificial insemination. A) Gelatin zymography gel B) MMP-9 protein concentration C) MMP-2 protein level. Pigs 903, 904, 905, and 906 are not pregnant. Pigs with identification numbers 302, 303, 305, and 306 are pregnant.