Placentome size in Bos taurus x Bos indicus crosses in the mexican tropics differs from the source breeds

Abstract

The objective of the present study is to verify the size of placentomes, through ultrasonography, at different gestational ages in Bos indicus x Bos taurus crosses located in the tropics.Placentome size in cows can vary in response to many factors, including crossbreeding. Placentome measurents were taken by averaging the length and width of the placentome.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. Descriptive statistics were generated for diameter for each gestational age category. All statistical analyses were run with the SAS program (2013). In all nine categories, placentome size was larger than reported for Bos taurus cows and smaller than reported in Bos indicus cows. In conclusion, placentome size in the sampled Bos taurus x Bos indicus cows was intermediate between that of the two source breeds. This confirms that existing reference tables for Bos taurus and Bos indicus purebreds are not accurate for crossbreeds.