The effect of feed intake and body weight on purine derivative excretion and microbial protein supply in sheep1

Abstract

Urinary excretion of purine derivatives (PD) was used to estimate the microbial N (MN) supply to sheep in three experiments designed to examine the effects of DMI and BW on the efficiency of microbial N supply (EMNS) to the host animal. In Exp. 1, four sheep of about 45 kg BW were given 328, 656, 984, and 1313 g of DM/d of a hay/concentrate diet in a Latin square design. Excretion of PD per kilogram of digestible organic matter intake (DOMI) increased with intake, and EMNS increased from 12.0 to 28.3 g of MN/kg of OM digested in the rumen (DOMR). In Exp. 2, 19 sheep ranging from 22 to 73 kg BW were all offered 820 g of DM/d of the same diet as that fed in Exp. 1. Although DM digestibility was relatively constant, PD excretion varied from 4.5 to 13.5 mmol/d and EMNS from 8 to 36 g of MN/kg of DOMR, both inversely related to animal BW. In Exp. 3, five sheep of 48 to 57 kg BW were given a different diet at 702, 966, or 1,237 g of DM/d. Purine derivative excretion per kilogram of DOMI increased with the DMI:BW ratio. Calculated EMNS ranged from 23 to 35 g of MN/kg of DOMR. Pooled data from all experiments showed EMNS to be related to the DMI:BW ratio. It is suggested that the DMI:BW ratio defines the ruminal digesta passage rate and hence outflow of microbial protein. The results imply that the EMNS for a given diet is not constant, but changes with intake.

Microbial protein production determined by urinary allantoin and renal urea sparing in normal and low protein fed Corriedale sheep

“…However, results of the same order as ours and obtained by the allantoin method have been reported: 5.7 g microbial N/day for an intake of 444 g DOMI/day and 45 kg BW [6] and 10.9 g microbial N/kg DOMR/day, corresponding to 4.2 g microbial N/day and an intake of 590 g DOMI/day, in sheep weighing 42 kg [20]. There is no clear explanation for these low values, but factors related to the quality of the ingredients of the diet could be evoked.…”

Estimation of microbial protein supply in ruminant animals based on renal and mammary purine metabolite excretion. A review

“…Further studies, reporting a close correlation between urinary allantoin excretion and rumen NA concentrations (Topps and Elliot, 1965;Mudgal and Taneja, 1977;Turchinski, 1980) and nutrient intake (e.g. Vercoe, 1976;Antoniewicz, 1983;Coto et al, 1984;Lindberg, 1985;Chen et al, 1992a;Giesecke et al, 1994) have provided further indirect evidence to support initial suggestions that urinary allantoin excretion could be used as an indicator of rumen MP production (Topps and Elliot, 1965;Rys etal., 1975).…”

“…Ratios of purine :N in rumen bacteria are subject to considerable variation (Table 1), but the extent of which is due to real sources and that introduced as a result of sampling and analytical errors remains unclear. Chen et al (1992a) proposed the use of a rumen microbe purine-N:N ratio of 0.116, while Kanjanapruthipong, cited by Kanjanapruthipong and Leng (1998) reported an equivalent ratio of 0.0824, indicating that 1 calculated assuming a mean molar adenine:guanine ratio of 1:1.70 for mixed rumen bacteria (Volden etal., 1999) 2 calculated assuming a molar adenine:guanine ratio of 1:1.63 and 1:1.76, for LAB and SAB, respectively (Volden et al, 1999) prediction of MP supply can be biased by the use of a purine :N ratio isolated from a single microbial fraction. In common with other microbial markers, obtaining representative samples of rumen microbes is fundamental to the accuracy of the PD technique.…”

“…Assuming that energy supply is the largest constraint on rumen MP synthesis, this variability can largely be attributed to differences in rumen outflow rates and the microbial maintenance coefficient (Dewhurst and Webster, 1992), and that introduced due to errors associated with the quantification of MP supply. In addition to feeding level (Robinson et al, 1985;Chen et al, 1992a), differences in carbohydrate and N sources, defaunation, and dietary supplements of various agents such as ionophores and branch chain fatty acids may influence EMPS (refer to Sniffen and Robinson, 1987;Hoover and Stokes, 1991;Clark et al, 1992;Chamberlain and Choung, 1995). Consequently, due to the influence of these factors and the inadequacies of techniques used to determine the rate and extent of OM fermentation in the rumen (Dewhurst et al, 1995) none of the modern protein evaluation systems can provide an accurate prediction of MP supply for all animals and feeding situations.…”

Effects of long-term supplementation of chestnut and valonea extracts on methane release, digestibility and nitrogen excretion in sheep

“…The methane energy was calculated using the equation of Brouwer (1965) and converted to MJ. Microbial protein synthesis was calculated using the urinary excretion of purine derivatives according to equations (1) and (2) of Chen et al (1992).…”