Hormonal Profiles of Late Gestation Ewes Following Intra-uterine Inoculation With and Without Lux-modified Escherichia coli

Abstract

Abstract. The objectives of these investigations were to develop an ovine model for Escherichia coli (E. coli)-induced preterm delivery, and monitor ewe hormonal response. EXP 1: Ewes (105 ± 13 days of gestation) were allotted to the following intra-uterine inoculations: Saline-(CON; n=5); 1 × 10 6 CFU/ml (Low Treatment, LT; n=6); or 1 × 10 7 CFU/ml (High Treatment, HT; n=6) E. coli. Twenty-four h after inoculation, the HT ewes had increased (P<0.05) cortisol compared to LT and CON ewes, and HT and LT ewes had increased (P<0.05) progesterone compared to CON ewes. Preterm delivery was 33% for LT ewes and 0% for HT and CON ewes. EXP 2: Ewes (124 ± 18 days of gestation) were allotted to the following intra-uterine inoculations using lux-modified E. coli: Trial-1: Luria Broth (LB; CT1; n=5); 4.0 × 10 6 CFU (n=5), 20.0 × 10 6 CFU (n=5); and Trial-2: LB (CT2; n=5), 1.2 × 10 6 CFU (n=5), and 5.6 × 10 6 CFU (n=5) E. coli-lux. Preterm delivery occurred between 48 and 120 h post-inoculation in 60, 25, 60 and 75% of ewes infected with 1.2, 4.0, 5.6, and 20 × 10 6 CFU, respectively. Serum cortisol and progesterone did not differ (P>0.05) between CT1 or CT2 and inoculated ewes. In summary, 25 to 75% of ewes inoculated preterm delivered. However, variable results in cortisol and progesterone profiles between Control and inoculated ewes were observed between the two studies. Key words: Cortisol, Escherichia coli, Pregnant, Progesterone, Sheep (J. Reprod. Dev. 55: [55][56][57][58][59][60][61][62] 2009) eproductive efficiency of livestock is reduced in response to non-specific uterine infections and ultimately causes a decline in profit potential of sheep farms. Of the 66,100 sheep operations with a total national flock of 6,965,000 head, 18.3 ± 0.5 percent of ewes in the flocks were culled in 2000. Of the culled ewes 5.5 ± 0.4 percent were due to failure to lamb [1].In dairy cows, uterine infections reduce reproductive efficiency; with infections reported to be associated with changes in progesterone and estrogen concentrations during the estrous cycle [2]. In a retrospective study from 1999 to 2006 on a total of 434 reproductive cases involving dairy farms and beef cow-calf farms in Finland; inflammatory lesions suggesting bacterial infection were detected in 30% (85/286) of fetuses and in 14% (20/148) of stillbirths. Significant bacteriological load was isolated from 26% of fetuses and 10% of stillbirths [3]. In swine, a reduction in ability of the uterus to resist infections occurred with endogenous and exogenous progesterone [4]. Similarly in the ewe, the uterus is rendered resistant to bacterial infection when progesterone levels are low, while the uterus becomes susceptible to post partum infections with progesterone supplementation [5]. In goats, low estrogen levels with low progesterone probably enhanced the uterine immune system post partum [6]. Thus resistance to uterine infections have been reported among livestock when concentrations of progesterone are basal, yet when concentrations of progesterone are increased...