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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.

Two experiments were performed with post-valve T-cannulated growing pigs, using five animals in each experiment in a change-over design to evaluate the effect of inclusion of four different dried forage meals on ileal crude protein (CP) and amino acid (AA) digestibilities. The control diets (C1 and C2) were barley-based and the experimental diets were formulated by replacing the barley with 100 or 200 g/kg of either lucerne (Medicago sativa) or white clover (Trifolium repens) meal in Expt 1 and red clover (Trifolium pratense) or perennial ryegrass (Lolium perenne) meal in Expt 2. A decrease (P < 0.05) in the apparent ileal digestibility of CP and most of the essential and nonessential AA was found with the inclusion of luceme, white clover and perennial ryegrass meal in the barley-based diets. When red clover meal was included, only the apparent ileal digestibilities of CP, leucine, phenylalanine, tyrosine and glutamic acid were found to decrease (P < 0.05). The estimated apparent ileal digestibilities of most essential AA in the forage meals were lower than in the barley-based diets. The ileal flow of glucosamine and ornithine was found to increase (P < 0.05) with increasing proportion of fibre in the diet, suggesting an increase in endogenous N secretions and small-intestinal microbial activity. With the minor changes found for ileal essential AA digestibilities with forage meal inclusion in the diet the present data confirm the potential of forage meals as a source of protein in pig diets.

Wether sheep were fitted with rumen fistulas and polyethylene tubes to the abomasum and were given all nutrients by intragastric infusion. In Expt 1 volatile fatty acids (VFA) were given at 340, 450 and 630 kJ gross energy (GE)/kg metabolic weight (W0-75) and protein at 0, 150, 300, 600, 900 and 1500 mg nitrogen/kg W0-75. In Expt 2 VFA were infused at 450 kJ GE/kg W0-75 and protein at 0 and 300 mg N/kg W0-75. At all levels of energy intake in Expt 1 the N retention was significantly (P less than 0.01) related to N intake. The basal N requirement was estimated to be 281 mg (SE 21.8) N/kg W0-75 at 340 kJ VFA/kg W0-75, 226 (SE 21.8) mg N/kg W0-75 at 450 kJ VFA/kg W0-75 and 207 (SE 19.4) mg N/kg W0-75 at 630 kJ VFA/kg W0-75. Plasma urea concentrations varied markedly in relation to protein intake and to energy supply. On the other hand plasma ammonia, glucose, insulin and creatinine concentrations, and also urinary excretion of purine derivatives and creatinine were not significantly affected by the treatments imposed. It was concluded that the urinary excretion of purine derivatives in ruminants was largely unaffected by moderate changes in energy intake and by large changes in protein intake.

1. In Expt 1 three male goat kids of the Swedish Landrace breed were bottle-fed on isoenergetic liquid diets composed of goat's milk alone or substituted with 200, 400, 600 and 800 ml of a nitrogen-free liquid diet/l. The goat kids were 3 weeks old at the start of the experiment and weighed on average 5.3 (SD 0.22) kg. The experiment lasted for 45 d divided into nine 5 d periods. The goat kids were kept individually in metabolism cages, and faeces and urine were collected daily. 2. In Expt 1 there was a significant (P less than 0.001) relation between N intake and N retention, with an estimated (extrapolation) basal N excretion of 211 mg N/kg metabolic live weight (W0.75). While the creatinine excretion remained fairly constant (19.9 mg/W0.75), there was a tendency for both the allantoin and uric acid excretions to change with N intakes. Hypoxanthine showed no consistent excretion pattern, and xanthine could not be detected. 3. In Expt 2 three male goat kids of the Swedish Landrace breed were used to study the effect of level of intake on N and purine metabolism. The first experimental period (period 1) started at 2 weeks of age (5.5 kg live weight) and the second experimental period (period 2) at 9 weeks of age (9.8 kg live weight). The goat kids were bottle-fed on goat milk at intended intakes of 400, 600, 800 and 1000 kJ gross energy/kg W0.75. Each treatment was given for 7 d with adaptation for 3 d and collections for 4 d. 4. In Expt 2 there were significant (P less than 0.001) increases in both live weight and N retention when level of intake was increased. With increasing N intakes both total N and urea-N excretions increased significantly (P less than 0.05). The proportions of urea-N and ammonia-N were fairly constant within periods, and were on average respectively 0.81 and 0.059 in period 1 and 0.84 and 0.068 in period 2. There was no significant effect of treatment on the urinary excretion of allantoin, hypoxanthine, xanthine and creatinine. In period 2 uric acid excretion was significantly (P less than 0.01) affected by the treatments. 5. From the presented findings it is concluded that the endogenous urinary excretion of purine derivatives in a young growing ruminant was only marginally affected by large variations in protein supply, and also by the level of intake of milk.

Sheep were given a diet of 400 g chopped grass hay/d and 500 g crushed barley/d in three equal meals. The mean retention time in the whole gut (MRT) and the rumen retention time (RRT) of chromium-labelled feed particles and of water were estimated from marker concentrations in faecal samples. MRT of Cr-labelled hay (Cr-H), barley hulls (Cr-Bh), crushed peas (Pisum sativum) (Cr-CP) and rapeseed meal (Cr-RSM) were 53.5, 52.3, 44.3 and 37.0 h respectively when estimated from total faecal collections. The estimates obtained from spot samples of faeces were almost identical. RRT of Cr-H, Cr-Bh, Cr-CP, Cr-RSM (Expts 1, 2 and 3) and Cr-labelled cottonseed meal (Cr-CSM) was 35.9, 36.7, 25.3, 18.8, 19.8, 22.8 and 25.3 h respectively. The Cr-labelled feed particles showed marked variations in density in water (Dw). However, both MRT and RRT were closely related to Dw (r -0.88 and -0.95 respectively). Rumen outflow rates of Cr-RSM in individual animals were related to the rumen outflow rates of water (r 0.76).

Rapeseed (Brassica napus), barley grain, ryegrass (Lolium perenne) and barley straw were labelled with 15N as an internal marker. The dilution of 15N was used to estimate microbial N (RMN15N) in the feed residues in nylon bags incubated in the rumen for 5, 12 and 24 h. For comparative purposes, diaminopimelic acid (DAP) content of the residues was also determined and rumen microbial N (RMNDAP-N) in the feed residues calculated using DAP as a bacterial marker. The influence of two bag pore sizes (20 microns and 40 microns) with different sample sizes (1 g and 5 g respectively) was also studied. For all feeds, the average disappearance of 15N was faster than that of total N, the difference between N and 15N disappearance being marked with barley, ryegrass and barley straw. The disappearance of microbially corrected dry matter (DM; correction calculated from the 15N values) was, accordingly, always faster than the uncorrected DM disappearance. Except for the bag pore/sample size effect for N disappearance, significant (P less than 0.01-0.001) feed, pore/sample size and incubation-time effects were always found for the disappearance values. Errors (%) resulting from the microbial contamination (calculated from the 15N values) in N-loss measurement with rapeseed, barley, ryegrass and barley straw, at 5, 12 and 24 h in 20 microns bags were respectively: -1.8, -3.9, -0.9; -3.8, -22.4, -3.8; -7.2, -4.1, -2.9; -164.5, -146.3, -204.6. In 40 microns bags the corresponding errors were respectively: -4.4, -1.2, -0.7; -26.1, -10.5, -3.9; -13.2, -6.4, -5.5; -221.2, -310.1, -1284.6.(ABSTRACT TRUNCATED AT 250 WORDS)