WORTH EINEMANN SEMINAL QUALITY AND SPERM PRODUCTION IN BEEF BULLS WITH CHRONIC DIETARY VITAMIN A DEFICIENCY AND SUBSEQUENT RE-ALIMENTATIQN L. M. Rode, G. H. Coulter, J. P. Kastelic’ and D. R. C. Bailey Research Centre, Agriculture and Agri-Food Canada P. 0. Box 3000, Main, Lethbridge, Alberta, Canada TlJ 4Bl Received for publication: zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPO Juty 26, 1994 Accepted: November 17, 1994 ABSTRACT Sixteen Hereford bulls (16 mo of age, 462 kg average body weight) were used in each of 2 yr to evaluate the effects of hypovitaminosis A on seminal quality and sperm production. Bulls were fed a high-concentrate diet with (+VIT) or without (-VIT) supplemental Vitamin A until the apparent onset of hypovitaminosis A (28 and 32 wk in Year 1 and 2, respectively). Half of the bulls on each treatment were then slaughtered and those remaining were re-alimented with Vitamin A. Plasma retinol concentration in -VIT bulls reached a nadir at approximately 25 wk. In Year 1, the proportion of progressively motile spermatozoa was lower in -VIT bulls after 17 wk but returned to that of the +VIT group after re-alimentation. The proportion of spermatozoa with primary morphological defects appeared to be greater in -VIT bulls compared to +VIT bulls by 26 and 24 wk in Year 1 and 2, respectively. The incidence of these defects declined in -VIT bulls upon re-alimentation, and approached the incidence observed in +VIT bulls by 8 to 12 wk of re-alimentation. Hypovitaminosis A decreased paired testes weight, daily sperm production, and epididymal sperm reserves but did not affect daily gain. Prolonged dietary Vitamin A deficiency impaired semen quality and sperm production in the abscence of other clinical symptoms. However, under practical feeding conditions, diets that result in long-term, marginal Vitamin A deficiency or a relatively short-term absence of Vitamin A intake probably would have minimal effects on spermatogenesis. Key words: bull, Vitamin A deficiency, testes, seminal quality, spermatozoa INTRODUCTION The most consistent symptom of hypovitaminosis A is the replacement of normal epithelium with keratinlzed squamous epithelium (4). In rats, hypovitaminosis A caused degeneration of the seminiferous tubules and, therefore, a cessation of spermatogenesis (7). In bulls, symptoms of hypovitaminosis A include disruption of spermatogenesis and reduced libido (8, 11). During the breeding season, beef bulls typically graze pastures that contain adequate levels of Vitamin A in the form of fl-carotene. However, at other times and in some management systems, bulls may be exposed to periods of chronic dietary Vitamin A deficiency. At weaning, many bull calves (potential sires) are placed on high-concentrate diets in test stations to determine growth performance. Acknowledgments LRC Contribution No. 3879210. The authors thank Allyn Mills and Geoff Wallins for excellent technical contributions, Toby Entz for statistical analyses and Shelia Torgunrud for graphics. ‘To whom reprint requests should be addressed Theriogenology 43:1269-i 277, 1995 Q 1995 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDC 0093-691X’95/$10.00 SSDI 0093-691 X(95)00096-S