Effect of glucose supply on fasting nitrogen excretion and effect of level and type of volatile fatty acid infusion on response to protein infusion in cattle

Abstract

Two experiments were carried out on cattle nourished entirely by intragastric infusion, to determine the extent to which glucose or a glucose precursor determines the response to protein infusion in energy-undernourished animals. In order to determine the requirement for glucose in 1-year-old fasting cattle, glucose was infused at increments to supply 0, 1·5, 2·5, 3·5, 4·5, 5·5 and 6·5 g/kg metabolic body weight (W0·75) and the effects on plasma β-hydroxybutyrate and N excretion were measured. At 5·5 g glucose/kg W0·75 plasma β-hydroxybutyrate was reduced to a basal level of 1·65 mmol/l and fasting N excretion reduced from 529 to 280 mg N/kg W0·75. No further reduction was observed with the higher level of 6·5 g glucose/kg W0·75. In the second trial, three steers were used in a 3 × 3 Latin square design and infused with a volatile fatty acid mixture of 65, 27 and 8 mol acetic, propionic and butyric acids respectively/100 mol, either at an estimated maintenance energy level of 450 kJ/kg W0·75 and supplying a calculated glucose equivalent level of 13·0 g/kg W0·75 (M1A), or at 1·5 × maintenance supplying a glucose equivalent of 20 g/kg W0·75 (M1·5A). Another mixture infused at the maintenance energy level contained 49, 43 and 8 mol acetic, propionic and butyric acids respectively/100 mol but with a glucose equivalent of 20 g/kg W0·75 (M1P). Casein was infused at each of these energy treatments to supply 0, 200, 400, 800, 1600 and 2500 mg N/kg W0·75 daily, and N balance and blood metabolites were measured. N retention increased linearly (r 0·98) with casein infusion. The coefficients for N retention were 0·55, 0·57 and 0·64 for M1A, M1·5A and M1P respectively. The mean efficiency of N utilization was 0·58. The results suggest that provided the glucose need is met there is no relationship between energy supply and efficiency and level of protein retention. However, the results also indicate that glucose requirement in cattle may be higher than that previously observed in sheep.

Interaction between protein and energy supply on protein utilization in growing cattle: A review

“…However, some observations using this experimental approach (Lindberg and Jacobsson, 1990;Ørskov et al, 1999) are suggestive of the existence of protein-and energy-dependent phases of growth, which contrasts most of the experiments involving normally fed animals. These apparent inconsistencies might occur because, under conditions of total intragastric infusion, the metabolism of the animals may differ from that of normally fed animals because intragastrically maintained animals usually present a nonfunctional rumen, as well as a regressed thin-walled intestine (Ørskov et al, 1979), resulting in different overall metabolism and reduced growth rate.…”

Improving the quality of rice straw by urea and calcium hydroxide on rumen ecology, microbial protein synthesis in beef cattle

“…Moreover, Ørskov et al. () discussed that, when high fibre diets were offered, VFAs in ruminal fermentation shifted from 65:25:10 to 70:20:10 (acetate: propionate: butyrate, in molar percentage) ratios.…”

“…Rice straw is an important crop residue practically used by farmers for ruminant feeding especially during the long dry season (Ørskov et al.,). However, rice straw is low in nutritive value with low level of protein (20–50 g/kg DM), high fibre and lignin content (NDF > 650 g/kg), low DM digestibility (<450 g/kg), thus resulting in low voluntary feed intake (Wanapat et al., ).…”

Analysis of Nitrogen Utilization and Excretion in Growing Dairy Cattle

“…When DMI is zero, however, as may be approximated experimentally with intragastric infusion, 0.300 g/kg of BW 0.75 is predicted to be excreted in urine alone. Orskov and MacLeod (1982) found in dairy cattle that total N excretion at zero N infusion with VFA energy infusion was between 0.308 and 0.429 g/kg of BW 0.75 , and more recently, Orskov et al (1999) found a value of 0.261 g/kg of BW 0.75 when glucose energy was infused but no N was given. Furthermore, Hovell et al (1987) indicated that a mean value of basal UN excretion for 23 lambs nourished by intragastric infusion of VFA with no NI was 0.356 g/kg of BW 0.75 .…”