Testicle length as an indicator of sperm production in male alpacas in Sweden

• Testicle length as an indicator of sperm production in male alpacas in Sweden J. Puhakka 1, M.C. Abraham 1, A. Ruete 2, J. Morrell 1 and R. Båge 1 1Division of Reproduction, Department of Clinical Sciences, Swedish University of Agricultural Scienc, 2Department of Ecology, Swedish University of Agricultural Sciences  Male alpacas are reported to reach puberty at 1-3 years of age; this long timespan is not helpful for herd management. Previous studies have shown that testicle length can be used as an indicator of sperm production, with 4 cm as a threshold (1). Aim: To find out when male alpacas in Sweden can be expected to start producing sperm, and whether this age is affected by body condition. Testicle length was measured in 72 male, 12-48 months old alpacas. Body condition was scored (BCS) 1-5 according to a standardized scale. Relationships between testicle length, BCS and age were studied by regression analysis. Testicle length was explained by squared age (p=0.024) and by BCS (p=0.007). However, the best model only included age, probably because age and BCS are correlated (r=0.28; p=0.016). Of the 1-2 year old males 27 % could be expected not to produce any sperm, 43 % to produce little or no sperm, and 30 % to produce sperm to a varying degree. Of the 2-3 year old males 25 % could be expected to produce little or no sperm, 69 % to a varying degree and 6 % would definitely be producing sperm. Among the 3-4 year old males 80 % were probably producing to a varying degree and 20 % would definitely be producing sperm. Mean testicle length was 3.4 cm (2.5-4.4), 4.3 cm (3.4-5.2) and 4.7 cm (4.1-5.6) in respective age group. This wide variation cannot be fully explained by BCS differences. Swedish alpacas seem to have larger testicles than alpacas in Peru, probably due to better nutrition, but data are consistent with Australian reports. In practice, testicle length has to be used combined with e.g. sexual behavior for decision making on farm. 1. Galloway DB (2000). The Development of the Testicles in Alpacas in Australia. Proc. of the Australian Alpaca Industry Conference, p21-23.

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LANTBRUKSVETENSKAPER  -- Veterinärmedicin -- Klinisk vetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Veterinary Science -- Clinical Science (hsv//eng)

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