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The continuous presence of ewes in estrus in spring influences testicular volume, testicular echogenicity and testosterone concentration, but not LH pulsatility in rams

Published online by Cambridge University Press:  16 June 2020

J. A. Abecia Open the ORCID record for J. A. Abecia [Opens in a new window] ,
M. Carvajal-Serna ,
A. Casao ,
C. Palacios ,
L. Pulinas ,
M. Keller ,
P. Chemineau  and
J. A. Delgadillo
J. A. Abecia*
Affiliation:
IUCA, Departamento de Producción Animal y Ciencia de los Alimentos, Universidad de Zaragoza, Miguel Servet, 177, 50013Zaragoza, Spain
M. Carvajal-Serna
Affiliation:
IUCA, Departamento de Producción Animal y Ciencia de los Alimentos, Universidad de Zaragoza, Miguel Servet, 177, 50013Zaragoza, Spain
A. Casao
Affiliation:
IUCA, Departamento de Producción Animal y Ciencia de los Alimentos, Universidad de Zaragoza, Miguel Servet, 177, 50013Zaragoza, Spain
C. Palacios
Affiliation:
Departamento de Construcción y Agronomía, Facultad de Ciencias Agrarias y Ambientales, Avenida Filiberto Villalobos, 119, 37007Salamanca, Spain
L. Pulinas
Affiliation:
Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100Sassari, Italy
M. Keller
Affiliation:
Physiologie de la Reproduction et des Comportements, UMR INRA, CNRS, Université de Tours, IFCE, Agreenium, 37380Nouzilly, France
P. Chemineau
Affiliation:
Physiologie de la Reproduction et des Comportements, UMR INRA, CNRS, Université de Tours, IFCE, Agreenium, 37380Nouzilly, France
J. A. Delgadillo
Affiliation:
Centro de Investigación en Reproducción Caprina, Universidad Autónoma Agraria Antonio Narro, Periférico Raúl López Sánchez y Carretera a Santa Fe, C.P. 27054, Torreón, Coahuila, Mexico
*
†E-mail: alf@unizar.es
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Abstract

The continuous presence of active male small ruminants prevents seasonal anestrus in females, but evidence of the same mechanism operating from the females to the males is scarce. This study assessed the effects of the continuous presence of ewes in estrus in spring on ram sexual activity, testicular size and echogenicity, and LH and testosterone concentrations. On 1 March, 20 rams were assigned to two groups (n = 10 each): isolated (ISO) from other sheep, or stimulated (STI) by 12 ewes, which were separated from the rams by an openwork metal barrier, allowing contact between sexes. Each week, four ewes were induced into estrus by intravaginal sponges. Live weight, scrotal circumference, testicular width (TW) and length (TL) were recorded at the beginning and at the end of the experiment, and testicular volume (TV) was calculated; at the same time, testicular ultrasonography and color Doppler scanning were performed. Blood samples (March to May) were collected once per week for testosterone determinations, and at the end of the experiment, blood samples were collected for 6 h at 20-min intervals for LH analysis. Rams were exposed to four estrous ewes in a serving-capacity test. Scrotal circumference, TW and TL were higher in the STI than in the ISO rams (P < 0.05) in May, and TV was higher (P < 0.05) in the STI (391 ± 17 cm3) than in the ISO rams (354 ± 24 cm3). In ISO rams, the number of white pixels was higher (P < 0.01) in May (348 ± 74) than in March (94 ± 21) and differed significantly (P < 0.01) from that of the STI rams in May (160 ± 33). In ISO rams, the number of grey pixels was higher (P < 0.05) in May (107 ± 3) than it was in March (99 ± 1). Stimulated and ISO rams did not differ significantly in mean LH plasma concentrations (0.8 ± 0.5 v. 0.9 ± 0.4 ng/ml), LH pulses (2.1 ± 0.5 v. 2.2 ± 0.2) and amplitude (2.0 ± 0.4 v. 3.2 ± 0.7 ng/ml, respectively). Stimulated rams had significantly higher testosterone concentrations than ISO rams from April to the end of the experiment. Stimulated rams performed more (P < 0.05) mountings with intromission (3.0 ± 0.4) than did ISO rams (1.5 ± 0.5). In conclusion, after 3 months in the continuous presence of ewes in estrus in spring, rams had higher TV and some testicular echogenic parameters were modified than isolated rams. Although exposed rams also had higher levels of testosterone after 2 months in the presence of estrous ewes, their LH pulsatility at the end of the study was not modified.

Keywords

sheepsocio-sexual signalsanestrushormonestesticle
Type
Research Article
Information
animal , Volume 14 , Issue 12 , December 2020 , pp. 2554 - 2561
Copyright
© The Author(s), 2020. Published by Cambridge University Press on behalf of The Animal Consortium

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