Effects of partial ruminal defaunation on urea-nitrogen recycling, nitrogen metabolism, and microbial nitrogen supply in growing lambs fed low or high dietary crude protein concentrations1

Abstract

Urea-nitrogen recycling to the gastrointestinal tract (GIT), N metabolism, and urea transporter-B (UT-B) mRNA abundance in ruminal epithelium were evaluated in partially defaunated (PDFAUN) and faunated (FAUN) growing lambs fed 2 levels (10%, low, or 15%, high) of dietary CP (DM basis). Four Suffolk ram lambs (43.9 +/- 1.4 kg initial BW) were used in a 4 x 4 Latin square design with 27-d periods. Sunflower oil was fed (6%; DM basis) as an anti-protozoal agent. Nitrogen balance was measured from d 22 to 26, with concurrent measurement of urea-N kinetics using continuous intrajugular infusions of [(15)N(15)N]-urea. Feeding sunflower oil decreased (P < 0.01) total ruminal protozoa by 88%, and this was associated with a decrease (P < 0.01) in ruminal ammonia-N concentrations. Endogenous production of urea-N (UER; 26.1 vs. 34.6 g/d) and urea-N loss in urine (UUE; 10.1 vs. 15.7 g/d) were less (P < 0.01), and urea-N entering the GIT (GER; 16.0 vs. 18.9 g/d) tended to be less (P = 0.06) in PDFAUN as compared with FAUN lambs. However, as a proportion of UER, GER was greater (P < 0.01) and the proportion of recycled urea-N that was utilized for anabolism (i.e., UUA) tended to be greater (P = 0.09) in PDFAUN lambs. Partial defaunation increased (P < 0.01) microbial N supply. The UER, GER, and UUE were greater (P < 0.01) in lambs fed the high diet. However, as a proportion of UER, GER and its anabolic use were greater (P < 0.01) in lambs fed the low diet. The expression of UT-B mRNA in PDFAUN lambs was numerically greater (by 20%; P = 0.15) compared with FAUN lambs. In summary, results indicate that part of the mechanism for improved N utilization in defaunated ruminants is an increase in the proportion of endogenous urea-N output that is recycled to the GIT, thus potentially providing additional N for microbial growth.

Effect of Defaunation on In Vitro Fermentation Characteristics and Methane Emission When Incubated with Forages

“…It is well established that defaunation consistently decreased NH3-N concentration (Kiran and Mutsvangwa, 2010). However, the result of NH3-N concentration obtained from this study was completely in contrast to those of the previous reports.…”

COMBINATION OF SOYBEAN MEAL AND Hibiscus tiliaceus LEAF IN THE GOAT DIET: EFFECT ON SOME PARAMETERS OF CARBOHYDRATE METABOLISM

“…The dietary starch degradation in rumen was increased in defaunated sheep (Mendoza et al, 1993). There is a contrary between this experimental result and others (Kiran and Mutsvangwa, 2010;Grummer et al, 1983;Han et al, 1999;Mendoza et al, 1993), because before and after feeding ruminal acetate concentration was also increased by the protein supplementation ( Table 2). As the part of this study, the rumen digestible organic matter was unaffected by protein supplementation (Akhsan et al, 2015).…”

“…Kiran and Mutsvangwa (2010) (Grummer et al, 1983). Ruminal acetate and butyrate concentrations were decreased but propionate concentration was increased in defaunated sheep fed on high fiber diet (Han et al, 1999).…”

“…The defaunation may affect on the growth of rumen bacteria negatively, because ruminal ammonia concentration was decreased (Kiran and Mutsvangwa, 2010) and ruminal volatile fatty acids concentration was increased (Han et al, 1999) in defaunated ruminants. These facts in turn may decrease capability in the ruminal fermentability for dietary fiber.…”

UT-B Urea Transporter Localization in the Bovine Gastrointestinal Tract

“…Importantly, ruminal UT-B expression increases with age, correlating to increases in blood urea nitrogen (Naeem et al 2012) and it has recently been shown to be upregulated by solid feed intake (Berends et al 2014). In addition, UT-B mRNA expression increases in defaunated rumen, potentially explaining the increase in urea recycling that enables new microbial growth (Kiran and Mutsvangwa 2010). In adult cattle, bovine ruminal UT-B protein abundance and precise localization within the papillae cellular layers are regulated by dietary intake (Simmons et al 2009).…”