Effects of amount of intake and stage of forage maturity on urinary allantoin excretion and estimated microbial crude protein synthesis in the rumen of steers

Abstract

Using ruminally cannulated steers, we investigated how urinary allantoin excretion was related to variations in feed intake and stage of forage maturity. Further, different approaches were compared for predicting ruminal microbial crude protein (MCP) synthesis and its efficiency. Experimental diets were arranged in a replicated 3 x 3 Latin square design (experiment 1) and a 4 x 4 Latin square design (experiment 2). In experiment 1, a mixed diet [forage to concentrate, 68:32 on a dry matter (DM) basis] was fed at three intake levels corresponding to 1, 1.5 and 2 times maintenance energy requirements. In experiment 2, four silage-based diets were fed based on perennial ryegrass (Lolium perenneL.), which was harvested at four maturity stages. Both experiments demonstrated the influence of diet on microbial growth rate and by this on efficiency of MCP synthesis, although the magnitude of the effects differed between approaches used for estimating MCP. Linear functions satisfactorily characterised the relationship between urinary allantoin excretion (y) and digestible organic matter (OM) intake (x, kg/day; experiment 1: y = 7.94 + 17.34 x; R(2) = 0.785) or intake of OM effectively degraded in the rumen (x, kg/day; experiment 2; y = 22.32 + 5.93 x; R(2) = 0.695). Urinary excretion of allantoin permitted a semi-quantitative prediction of MCP synthesis: ranking of diets and magnitude of changes in MCP synthesis were reflected.

Microbial protein synthesis in young steers fed with grass silage and extruded corn

“…Several authors have reported that DOM intake can be a good estimator of the EMPS when there is adequate N intake (AFRC, 1992;. The EMPS values obtained in the EC-10 and EC-25 treatments (Table 4) were lower than the range of 12.0 and 28.3 g N kg -1 OMTDR reported for ewes by and the range of 25 to 27 g N OMADR found for steers by Südekum et al (2006). Furthermore, the results from Orellana et al (1998) obtained with dairy cows match those obtained in our study for the highest intake of EC (between 13 and 17 g N kg -1 DOMR), with the highest EMPS corresponding to the highest concentrate levels.…”

“…Digestible OM intake (DOMI) was calculated from OM digestibility and daily OM intake. Organic matter truly digested in the rumen (OMTDR; kg d -1 ) was calculated from the relationship OMTDR = 0.55 × OMI (Stern et al, 1994;Südekum et al, 2006). The OM apparently digested in the rumen (OMADR, kg d -1 ) was determined by the relationship: OMADR = 0.60 × DOMI (Schröder et al, 1997;Südekum et al, 2006).…”

“…The PD excretion values in the EC-10 and EC-25 treatments are also lower than those presented by Verbic et al (1990) (51.5 and 45.7 mmol d -1 , in two experiments). Südekum et al (2006) suggest that at low intake levels, the energy and the nutrients are ingested almost exclusively for the purpose of maintaining ruminal microorganisms; once intake exceeds these maintenance requirements, an increasing proportion of the nutrients can be used for the growth of ruminal microorganisms. According to Fujihara and Shem (2011) the movement of nucleic acids from tissue is influenced by the animal's metabolic activity, and when the MP contribution is calculated using the urinary PD excretion in ruminants fed at sub-maintenance levels, this must be considered a loss of endogenous PD.…”

Effects of replacing soybean meal with dried rumen digesta on feed intake, digestibility of nutrients, rumen fermentation and nitrogen use efficiency in Thai cattle fed on rice straw

“…N consumed by cattle ultimately appears in either the urine, feces or is interchanged with the body's N reserves (Südekum et al, 2005). Total N excretion tended to be increased (0.6-1.0 g/d) when increasing urea at 1.3-1.9% DM in concentrate diets.…”

Urinary purine derivates excretion as an indicator of in vivo microbial N flow in cattle: A review

“…1). In many Table 3 The endogenous contribution (μmol/kg BW 0.75 per day (±SD)) to urinary excretion of total purine derivates (PD) or allantoin, estimated in steers, dry and lactating cows with different methods studies with cattle, the excretion of allantoin or total PD in urine was not only well related with duodenal flows of N, NAN, or microbial N, but also with dietary RDP content (Reynal et al, 2005), dry matter intake (R 2 = 0.50, Stefanon et al, 1995;Moorby et al, 2006), organic matter intake (R 2 = 0.62, Susmel et al, 1994), digestible organic matter intake (R 2 = 0785, Südekum et al, 2006), and N intake (R 2 = 0.91, Stefanon et al, 1995). Firkins et al (2006) showed with a large dataset (339 observations) that urinary allantoin excretion was best explained in lactating cattle by milk yield, intake of RDP and of non-fibre carbohydrates (NFC), and in nonlactating cattle solely by intake of RDP.…”