Administration of recombinant bovine somatotropin prior to fixed-time artificial insemination and the effects on fertility, embryo, and fetal size in beef heifers

Abstract

Our objectives were to determine the effects of the administration of recombinant bovine somatotropin (bST) at the initiation of a fixed-time AI (TAI) protocol on concentrations of plasma IGF-1, follicle diameter, embryo/fetal size, and pregnancy rates in replacement beef heifers. Four hundred and fourteen Angus-based beef heifers were enrolled in a completely randomized design at 4 locations from January to July of 2016. All heifers were exposed to the 7-d CO-Synch + controlled internal drug release (CIDR) protocol where they received a 100-µg injection of GnRH and a CIDR insert on day -9, 25 mg of PGF2α at CIDR removal on day -2, followed by a 100-µg injection of GnRH and TAI 54 ± 2 h later on day 0. Within location, all heifers were randomly assigned to 1 of 2 treatments: 1) heifers that received 650 mg of bST on day -9 (BST; n = 191); or 2) heifers that did not receive bST on day -9 (CONTROL; n = 223). Blood samples were collected on day -9, 0, 28, and 60 to determine the plasma concentrations of IGF-1. Follicle diameter was determined on day -2 and 0 by transrectal ultrasonography. Pregnancy was diagnosed via transrectal ultrasonography on day 28 or 35, and again at least 30 d after the end of the breeding season. Embryo morphometry was assessed by measuring crown-to-rump length (CRL) on day 28, and fetal size was assessed by measuring crown-to-nose-length (CNL) on day 60. Concentrations of plasma IGF-1 did not differ between treatments on day -9 (P = 0.924), 28 (P = 0.075), and 60 (P = 0.792); however, concentrations of plasma IGF-1 were greater (P < 0.001) in BST-treated heifers at TAI (372.4 ± 16.6 vs. 193.7 ± 16.6 ng/ml). No differences (P = 0.191) were detected for follicle diameter between CONTROL and BST treatments on day -2 or 0. Pregnancy rates to TAI (PR/AI) were greater (P = 0.028) for CONTROL compared to BST heifers (42.5 ± 4.0 vs. 29.9 ± 4.1%). No differences (P = 0.536) in CRL were observed on day 28 between CONTROL and BST heifers. In addition, no difference (P = 0.890) was observed for CNL between CONTROL and BST treatments. Final pregnancy rates did not differ (P = 0.699) between treatments. The administration of bST to beef heifers at the initiation of a TAI protocol increased plasma concentrations of IGF-1 at TAI; however, failed to enhance follicle diameter, embryo/fetal size, and reduced PR/AI.

Vitamin and Mineral Supplementation and Rate of Gain in Beef Heifers I: Effects on Dam Hormonal and Metabolic Status, Fetal Tissue and Organ Mass, and Concentration of Glucose and Fructose in Fetal Fluids at d 83 of Gestation

“…Concentrations of P4, insulin [ 26 , 27 ], and IGF-1 [ 28 , 29 , 30 ] were analyzed by competitive chemiluminescent immunoassay using the Immulite 1000 (Siemens, Los Angeles, CA, USA). A 50 µL sample of maternal serum and all controls were analyzed in duplicate.…”

Recombinant bovine somatotropin in the synchronization of ovulation in crossbred dairy cows (Bos taurus indicus × Bos taurus taurus)

“…Treatment with rbST did not increase the size of the ovulatory follicle 48 h after the removal of the PRID (day 10) [14,15]. In a study with Holstein cows in Brazil, the ovulatory diameter was greater for cows treated with rbST (18.2 mm) compared to the control group (15 mm) [5].…”

“…The rbST has been associated with a higher growth rate of the conceptus and consequently with an increase in pregnancy rate [9,28,29]. However, other studies report that the effect of rbST on the total pregnancy rate has not been observed [2,15]; or even a negative effect of rbST on reproduction, whereby cows treated with rbST had a decreased conception rate [31].…”

A Structural Analysis of the FDA Green Book-Approved Veterinary Drugs and Roles in Human Medicine

“…In humans it is used to treat multiple sclerosis. Thyrotropin releasing hormone is used to diagnose hypothyroidism and pituitary pars intermedia dysfunction (PPID) by administering the hormone to animals and observing the response . Oxytocin is a naturally occurring hormone that is used to stimulate uterine contractions in animals, as it is in humans.…”

“…Thyrotropin releasing hormone is used to diagnose hypothyroidism and pituitary pars intermedia dysfunction (PPID) by administering the hormone to animals and observing the response. 134 Oxytocin is a naturally occurring hormone that is used to stimulate uterine contractions in animals, as it is in humans. Both human and porcine insulins are approved for use in veterinary medicine with the two insulin structures differing by a single residue.…”