Effect of progestins on serum hormones, semen production, and agonistic behavior in the gerenuk (Litocranius walleri walleri)

Abstract

The use of progestins to suppress endogenous testosterone production to reduce agonistic behavior and prevent semen production was studied in gerenuk. Five male gerenuk (20 months to 3 years of age), housed as a bachelor group, were treated with 3 monthly injections of medroxyprogesterone acetate (MPA; 2.5-20 mg/kg), followed by a melengestrol acetate implant (MGA; 0.3 g/kg) for 2 months. Blood samples collected monthly were assayed for serum testosterone and cortisol using enzyme-linked immunoassays. Quantitative behavioral data were collected for 30 min 3/week starting 1 month before treatment. Body weight, testes volume, and semen traits were measured before treatment, after MPA treatment, and after MGA treatment. Results showed lower (P<0.05) mean serum testosterone concentrations after MPA (4.34 pg/ml) and MGA (5.02 pg/ml) treatment compared to pre-treatment values (65.9 pg/ml) in four of five gerenuk. The remaining sub-adult gerenuk had low testosterone initially (4.9 pg/ml) that did not decrease further with treatment (1.4 and 7.8 pg/ml for MPA and MGA, respectively). Mean serum cortisol concentrations decreased markedly after treatment with MPA (6.0+/-3.7 ng/ml) and MGA (0.8+/-0.3 ng/ml). Cortisol concentrations were regained rapidly post-treatment (42.8+/-4.8 ng/ml) and were not significantly different from the pre-treatment value (60.6+/-12.6 ng/ml; P>0.05). The mean incidence of combined aggressive/dominant behaviors (horning, sparring, supplanting, threat) was not different before and after treatment. Body weight, total numbers of spermatozoa produced per ejaculate, percent motility, and percent normal spermatozoa declined maximally 8 months after treatment. Mean testes volume decreased (P<0.05) after MGA treatment (10.53 cm(3)vs. 11.96 cm(3) pre-treatment). Elevated hepatic enzymes and bile acids were seen in three of five animals after progestin treatment and anorexia was noted in two males after MGA implant removal, however two of three males had elevated liver enzymes before progestin treatment began. Results show that reducing serum testosterone concentration does not seem to modify agonistic behavior in bachelor gerenuk groups. Zoo Biol 26:245-257, 2007. (c) 2007 Wiley-Liss, Inc.

Monitoração não-invasiva da supressão da atividade ovariana cíclica e do comportamento de estro em fêmeas de leão africano (Panthera leo), induzidos pelo uso de implantes de análogo de GnRH, deslorelina.

“…Contracepção é a prevenção deliberada da prenhes (HUTCHINS, 2005). , 1966;SEAL et al, 1975;SEAL et al, 1976;REYNOLDS;SOKOLOWSKI, 1977;TRIGG et al, 2001;WRIGHT et al, 2001;PELICAN et al, 2005;ASA;JUNGE, 2007;CHUEI et al, 2007;PATTON;PENFOLD et al, 2007;WHEATON et al, 2007;SCHOEMAKER et al, 2008 SORENSON; SCHULTZ, 1997) e de zoológico (SEAL et al, 1975;KIRKPATRICK et al, 1991 (SEAL et al, 1975;SEAL et al, 1976;DEMATTEO, 2005 SHORT, 1984;KOLLIAS JR., 1996;MUNSON, 2006), androgenização (SEAL et al, 1976) e ganho de peso BELLENGER, 1987;BALDWIN et al, 1994).…”