Age-Dependent Changes in Sperm Production, Semen Quality, and Testicular Volume in the Black-Footed Ferret (Mustela nigripes)1

Abstract

The black-footed ferret (Mustela nigripes), which was extirpated from its native North American prairie habitat during the 1980s, is being reintroduced to the wild because of a successful captive-breeding program. To enhance propagation, the reproductive biology of this endangered species is being studied intensively. The typical life span of the black-footed ferret is approximately 7 yr. Female fecundity declines after 3 yr of age, but the influence of age on male reproduction is unknown. In this study, testis volume, seminal traits, sperm morphology, and serum testosterone were compared in 116 males from 1 to 7 yr of age living in captivity. Results demonstrated that testes volume during the peak breeding season was similar (P > 0.05) among males 1 to 5 yr of age, reduced (P < 0.05) among males 6 yr of age, and further reduced (P < 0.05) among males 7 yr of age. Motile sperm/ejaculate was similar in males 1 to 6 yr of age but diminished (P < 0.05) in those 7 yr of age. Males at 6 and 7 yr of age produced fewer (P < 0.05) structurally normal sperm than younger counterparts; however, serum testosterone concentrations were not reduced (P > 0.05) in older males. Histological comparison of testicular/epididymal tissue from 5- and 7-yr-old black-footed ferrets confirmed that the interval between these two ages may represent a transitional period to reproductive senescence. In summary, functional reproductive capacity of male black-footed ferrets exceeds that of females by at least 2 yr. Testes and seminal quality are indistinguishable among males 1 to 5 yr of age, with progressive reproductive aging occurring thereafter.

Approaches and efficacy of artificial insemination in felids and mustelids

“…Thus, it was realized that (1) many males were not breeding naturally and (2) a valuable founder descendant was under-represented. A more detailed assessment of the first challenge revealed a high incidence of sexual incompatibility between designated mates, largely due to improper copulatory positioning, inter-animal aggression and poor testis development [110,111]. These findings collectively justified the need to begin applying AI within the blackfooted ferret breeding program.…”

Effect of dietary vitamin E and prey supplementation on semen quality in male black-footed ferrets (Mustela nigripes)

“…Previous research revealed that age (1-5 years) did not affect semen quality and testosterone concentrations [8]; however, each diet treatment had four 1-year-old males and seven 2-to 3-year-old males to ensure the age class of the ferret breeding population was represented. The beef diet was selected as a treatment to assess whether this diet could be offered to ferrets as an alternative diet to the horsemeat diet.…”

“…Recent studies reported that the percentage of normal spermatozoa (sperm) morphology in an ejaculate ranged from 50% reported in 2000 to 16% in 2006 and 2007 [6][7][8]. Additionally, the average breeding success rates for females have declined from original breeding success rate of 70% (from 1987 to 1998) to 46% reported in 2013 [3].…”

Aging of the Normal Lung

“…During the saccular stage, the lung parenchyma begins to form by the thinning of the connective tissue and the development of the surfactant producing system (Merkus et al, 1996). This is followed by Yu et al (1982) Rabbit Oryctolagus cuniculus 4e9 months 7.5 years Kilborn et al (2002) Guinea pig Cavia porcellus 6e11 weeks 8 years Wolfer and Lipp (1995) Pamplona et al (1998) Hamster Mesocricetus auratus 4e7 weeks 4 years Schulz et al (2004) Hart and Setlow (1974) Ferret Mustela putorius furo 8e12 months 7 years Ryan (1984) Wolf et al (2000) Dog Canis lupus familiaris 7e10 months 8e14 years Kilborn et al (2002) Speakman et al (2003 Sheep Ovis aries 5.5 months 15 years Suttie et al (1991) Oberbauer et al (1988 Pig Sus scrofa domestica 6 months 20 years Sterning et al (1998) Douglas (1972 the alveolar stage, which involves development of the primary gas exchange units primarily by a process of septation (Massaro and Massaro, 2002). It is these latter stages in particular where the relative development of the lung at birth varies considerably between species.…”