Placentome Size in Bos Taurus X Bos Indicus Crosses in the Mexican Tropics Differs From the Source Breeds

Abstract Placentome size in cows can vary in response to many factors, including crossbreeding. We measured placentome size at different gestational ages in Bos taurus x Bos indicus cows raised in the tropics. Uteruses were collected immediately after slaughter from 102 cows with gestations ≥ 30 days and processed in the abattoir. All cows were Swiss Brown x Zebu phenotypes. Fetus gestational age was estimated by measuring from the crown to the tail base. Five placentomes were randomly chosen from each uterus (n = 510), and diameter (cm) measured for each. Gestational age was classified into nine categories (days): a) ≤ 45, b) > 45 ≤ 60, c) > 60 ≤ 90, d) > 90 ≤ 120, e) > 120 ≤ 150, f) > 150 ≤ 180, g) > 180 ≤ 210, h) > 210 ≤ 240 and i) > 240. Placentome size data was grouped by these categories. In all nine categories, placentome size was larger than reported for Bos taurus cows and smaller than reported in Bos indicus cows. This intermediate size suggests that existing gestational age reference tables based on placentome size for purebred cows are not applicable to Bos taurus x Bos indicus crosses.