Effect of diet on milk allantoin and its relationship with urinary allantoin in dairy cows.

The present study examined the effects of diet on the concentration and excretion of allantoin in milk and the relationship between allantoin in milk and urine of dairy cows. Results are reported from three experiments. In Experiment 1, four diets with two different protein percentages and two different rumen degradabilities were fed to 12 cows in a continuous trial. In Experiment 2, four diets with different protein balance values in the rumen were fed to four cows in a 4 x 4 Latin square design. In Experiment 3, four diets with different contents of concentrate and fat were fed to four cows in two incomplete 2 x 2 Latin squares. The excretion of allantoin N in milk increased as dry matter intake increased (Experiment 1) and as the concentrate in the diet increased (Experiment 3). In Experiments 1 and 3, the excretion of allantoin in milk was correlated with its concentration in milk and with its excretion in urine. In the three experiments, allantoin excretion in milk was closely correlated with milk yield. The amount of allantoin secreted in milk represented a small proportion (0.63 to 1.34%) of the total excretion in urine and milk. The proportion of allantoin secreted in milk was negatively correlated with the urinary excretion of allantoin in Experiments 2 and 3 and positively correlated with the excretion of allantoin in milk in Experiment 1. In Experiments 1 and 2, the proportion of allantoin excreted in milk was not constant but increased as milk yield increased.

Portal net appearance of amino acids in growing pigs fed a barley-based diet with inclusion of three different forage meals.

The net absorption of amino acids (AA) in young pigs fed a barley-based control diet (C) and diets where barley was replaced by 200 g/kg fresh weight of dried lucerne (Medicago sativa; L20), white clover (Trifolium repens; W20) or perennial ryegrass (Lolium perenne; PR20) meal was studied. Castrated male pigs were fitted with permanent catheters in the hepatic portal vein and mesenteric artery, and the hepatic portal net absorption of AA was estimated from the porto-arterial plasma concentration differences and the hepatic portal-vein blood flow. In general, the essential AA (EAA) concentrations in the hepatic portal vein reached peak levels 90 min after feeding and thereafter exhibited a transient decline. Maximum porto-arterial differences were reached between 1 and 3 h postprandially for most of the AA. The cumulative net absorption of non-essential AA (NEAA) and EAA did not differ significantly between the barley-based diet and diets W20 and PR20. Due to a lower intake of AA on diet L20, the cumulative net absorption of NEAA and EAA was significantly (P < 0.05) lower than diet C. With the exceptions of the EAA arginine, cystine and valine, and the NEAA glutamic acid + glutamine and glycine, there were no significant differences in the absorption coefficients for the EAA and NEAA between the diets. In addition, the pattern of the total EAA in the mixture absorbed postprandially did not differ significantly between the diets. The present study gives support to the contention that the replacement of barley AA with forage meal AA in a barley-based diet for growing pigs should be expected to result in minor differences in the net portal flux of AA.