Masters Theses

Date of Award

8-1991

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

H.G. Kattesh

Committee Members

G.A. Baumbach, F.B. Masincupp

Abstract

In the first experiment 11 gilts were injected with 5 mg of estradiol benzoate on d 11-15 of the estrous cycle to induce pseudopregnancy. Twice daily on d 21-30 gilts were administered either 5 mg per kg bodyweight (avg. wgt 120 kg) hydrocortisone acetate (HA) in sesame oil (5 ml) or sesame oil (control) subcutaneously (SQ). Blood samples (20 ml) were collected via jugular puncture on d 11, 21, and 31. Uterine flushings were obtained surgically the day following the last day of treatment (d 31).

Twice daily injection of HA on d 21-30 significantly (p<.001) elevated cortisol levels above that of control animals in plasma and uterine flushing on d 31. The percent distribution of cortisol in plasma [% unbound (UB-C), % corticosteroid binding globulin (CB6) bound (CBG—C), and % albumin bound (Alb-C)] was not different between treatments. Plasma CBG binding capacity (CBG-BC) was lower (p<.001) following 10 d of treatment with HA compared to control gilts (7.4 versus 38.7 pmol/ml). Plasma progesterone (P4) levels were significantly (p<.01) lower in HA treated gilts (8.9 ng/ml) compared to control gilts (17.8 ng/ml). Uterine Flush P4 levels were also decreased (p<.001) compared to control gilts. Total plasma protein and albumin concentrations were similar (p>.05) to control gilts. Total proteins in the uterine flush were lower (p<.001) in HA treated gilts. Corpora lutea (CL) number and concentrations were not affected by treatment. Total CL weight was significantly (p<.01) lower in HA treated gilts compared to control animals.

In the second experiment 18 crossbred gilts exhibiting 2 normal estrous cycles (18-23 d) were naturally bred to a mature boar and randomly assigned to receive 5 mg/kg bodyweight (BW) HA (Trt 1), 2.5 mg/kg BW HA (Trt 2), or 5 ml sesame oil (control; Trt 3) twice daily on d 9-13 of pregnancy. Blood samples were collected on d 9, 11/ 13, and 20 of pregnancy. On d 46 ± 2 gilts slaughtered and reproductive tracts collected. CL number and CL weights were obtained. Number, weight, crown rump length, placental weight, allantoic and amniotic fluid volume of fetuses were measured and recorded.

Plasma cortisol levels were increased (p<.05) due to treatment on day 13. The distribution of cortisol (% UB-C, % CBG-C, and % Alb-C) was not different (p>.05) between treatments. CBG-BC, plasma P4 levels, total proteins, CL number, CL weight, fetal number, fetal length, and placental weight were not affected by treatment. Fetal weights in Trt 2 (2.5 mg/kg HA) were significantly (p<.05) lower compared to Trt 1 (5 mg/kg HA) and control gilts. Allantoic and amniotic fluid volumes were lower in Trt 2 (p<.001 and p<.05, respectively) compared to Trt 1 and control gilts.

These results suggest that : a) HA affected P4 production in the ovary by retarding CL development, B) the HA treatment lowered total P4 output, as reflected by lowered P4 concentration in the plasma, and affected protein secretion in the uterus, C) uterine protein secretions were preferentially reduced in the component contributed by P4-induced, locally synthesized proteins but not by serum transudate, D) HA did not affect liver function as measured by total plasma protein concentration, E) HA affected CBG as evident by the decrease in CBG-BC concentrations and F) reduction in uterine secretory protein output may result in lowered fetal weight due to poor nutrition in utero.

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