TY - JOUR
T1 - Administration of recombinant bovine somatotropin prior to fixed-time artificial insemination and the effects on fertility, embryo, and fetal size in beef heifers
AU - Oosthuizen, Nicola
AU - Fontes, Pedro L.P.
AU - Henry, Darren D.
AU - Ciriaco, Francine M.
AU - Sanford, Carla D.
AU - Canal, Luara B.
AU - de Moraes, Gentil V.
AU - Dilorenzo, Nicolas
AU - Currin, John F.
AU - Clark, Sherrie
AU - Whittier, William D.
AU - Mercadante, Vitor R.G.
AU - Lamb, G. Cliff
N1 - Publisher Copyright:
© The Author(s) 2018.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2018/5/4
Y1 - 2018/5/4
N2 - 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.
AB - 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.
KW - Beef heifers
KW - Fixed-time artificial insemination
KW - Insulin-like growth factor 1
KW - Recombinant bovine somatotropin
UR - http://www.scopus.com/inward/record.url?scp=85048191837&partnerID=8YFLogxK
U2 - 10.1093/jas/sky077
DO - 10.1093/jas/sky077
M3 - Article
C2 - 29733416
AN - SCOPUS:85048191837
VL - 96
SP - 1894
EP - 1902
JO - Journal of Animal Science
JF - Journal of Animal Science
SN - 0021-8812
IS - 5
ER -