Intravaginal Devices for Feedlot Heifers

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Abstract
Fifty-four 316-kg crossbred beef heifers approximately 15 months old were randomly assigned to two treatments with two pens per treatment. Plastic intravaginal devices were inserted into the heifers of two pens. The heifers were fed a finishing diet for 77 days and slaughtered. Blood samples for progesterone analysis were collected 1, 7, 14, 21, 63, 70 and 77 days after device insertion. Morning and evening observations of estrus activity were made daily, and 24-hr observations were recorded on five occasions. At slaughter 11 of the 27 heifers had lost their devices. Daily gains of control heifers and heifers that retained the devices were not different, 1.36 vs 1.29 kg, respectively. Carcass characteristics were not affected by the devices. There were no acute morphological aberrations due to the devices, although there was a thickening of the vaginal epithelium and a mild inflammation in the vaginal walls of the heifers with devices. Fresh ovary weights and serum progesterone levels were similar for control heifers, heifers that expelled their devices and heifers that retained their devices. Number of estrus cycles per heifer for control, expelled-device and retained-device heifers were not different, 1.8, 1.9 and 2.3, respectively. However, the total number of times heifers were mounted was highest (P<.10) for heifers that retained the devices followed by heifers that expelled the devices and then control heifers, 9.2, 7.6 and 5.3, respectively. Intravaginal devices did not improve feedlot performance or suppress estrus activity of feedlot heifers. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.