CIBTech Journal of Zoology ISSN: 2319–3883 (Online) An Open Access, Online International Journal Available at http://www.cibtech.org/cjz.htm 2016 Vol. 5 (3) September-December, pp.32-39/Moharrery et al. Research Article Centre for Info Bio Technology (CIBTech) 32 IS THERE A RELATIONSHIP BETWEEN NITROGEN INTAKE AND TESTICULAR UREA CONCENTRATION? Ali Moharrery 1 , *Rasoul Rezaei 1 and Mohammad Javad Zamiri 2 1 Department of Animal Science, Agricultural College, Shahrekord University, P.O. Box 115, Shahrekord 2 Department of Animal Science, College of Agriculture, Shiraz University, Shiraz, Iran *Author for Correspondence ABSTRACT An experiment was conducted to determine the relationship between nitrogen intake and testicular urea content. Twenty ram lambs of fat-tailed Iranian native breed were used in this study. The mean (±SD) age and body weight of the lambs were 180±20 days and 36.7±6.3 kg, respectively. The lambs were divided in to five groups of equal size, and received a ration containing a single protein source; including: 1) urea as a control, 2) barley grain, 3) cotton seed meal, 4) gluten meal, and 5) canola meal. Crude protein content of the diet was adjusted at 13.6 percent, but with different ruminal degradability. During the experiment, the lambs were kept in isolation to avoid exposure to the sight and smell of female sheep. Rams were kept under natural day light conditions and ambient temperature (latitude 51◦27_N) for 11 weeks. On day 75, ruminal fluid samples were collected at 2, 4, 6, and 10 hours after morning feeding. On day 76, jugular blood samples were collected in vacuum tubes containing heparin as the anti-coagulant, and slaughtered subsequently. The right testis was removed, weighed, homogenized in phosphate buffer solution, and centrifuged to collect the supernatant for future analysis. The testicular extract and plasma were analyzed for urea nitrogen, and the ruminal fluid sample and testicular extract were analyzed for ammonia concentration. All samples were assayed in duplicate. The level of nitrogen intake significantly affected the testicular urea concentration (P<0.05). Plasma urea concentration was significantly correlated with rumen ammonia concentration at 4 and 6 hours, but not at 2 and 10 hours, after feeding. Testicular urea and ammonia concentrations were highly correlated. In conclusion, plasma urea concentration did not impact on testicular urea and ammonia concentrations but, nitrogen intake had a significant effect on testicular urea concentration. Keywords: Urea, Testis, Blood Urea, Protein Sources, Sheep INTRODUCTION Protein is a key nutrient in ruminant nutrition, not only by providing amino acids to the animal, but also as a source of nitrogen (N) for microbial protein synthesis (NRC, 2007). Proteins differ in their amino acid profile, and the availability of crude protein (CP) in the rumen and at post-ruminal digestive tract (Gleghorn et al., 2004; Bateman et al., 2005). It is accepted that dietary protein requirements and supply are best expressed in terms of ruminal degradable (RDP) and undegradable protein. Because Nutilization efficiency inruminants is lower than in non-ruminants, it is necessary to feed large amounts of protein which increases the production cost and N loss to the environment. This may also exert detrimental effects on reproduction and cause lower production, especially during hot weather (West, 2003). Although, numerous studies have shownthat overfeeding protein negatively influences the male reproduction (Oldham et al., 1978; Cameron et al., 1988; Abi Saab et al., 1997; Al-Haboby et al., 1999), the mechanism by which excess protein intake influences reproduction is partly unknown. The relationship between protein nutrition and reproduction, usually recorded in rams, probably follows a non-linear model and hence, the magnitude of the response can vary when different levels of protein intake are compared (Fernandez et al., 2004). Fernandez et al., (2004) reported that above a certain level of protein intake there will not be any additional benefit on testicular growth. A number of studies have demonstrated that the spermatogenesis in rams is sensitive to increases in protein intake (Oldham et al., 1978; Cameron et al., 1988; Abi Saab et al., 1997). This effect has been related to an increase in testicular size increase as a result of increased volume of seminiferous epithelium and greater diameter of the