Concentration Of Urea In Blood Plasma Research Articles

Effects of Low-Protein Diets with Different Levels of Essential Amino Acids and Metabolizable Energy on Productivity and Metabolic Processes in Pigs

An experiment with growing meat pigs has proven the productive efficiency of low-protein diets rich in essential amino acids. In order to achieve a live weight of 20 kg, the use of 10.08 g lysine (accessible 9.0 g), 6.09 g threonine (accessible 5.33 g), and 5.04 g methionine (accessible 4.19 g) are required. In the growth period, 8.08 g (6.39 g), 5.26 g (4.46 g), and 5.04 g (4.23 g), respectively, are required, while 7.49 g (3.97 g), 4.93 g (4.43 g), and 4.72 g (3.97 g), respectively, are required in the fattening period; the metabolizable energy is expressed as 13.30–12.69 MJ/kg fodder. In addition, the ratios of lysine to the metabolizable energy (g/MJ), the threonine, and the sum of methionine and cystine should be in the ranges of 0.79, 0.60, and 0.51, respectively, in order to reach the live weight of 20 kg. In the growth period, these items should be in the ranges of 0.64, 0.65, and 0.62, respectively, while they should comprise 0.61, 0.65, and 0.63, respectively, in the fattening period. The data on the blood plasma urea concentration and the urinary excretion of nitrogeneous waste can prove the more efficient use of the amino acids in the biosynthetic processes under the experimental conditions.

Cattle and sheep develop preference for drinking water containing grape seed tannin

Ingestion of small amounts of some types of condensed tannins (CTs) by ruminant livestock can provide nutritional, environmental and economic benefits. However, practical methods are needed to make these tannins more available to ruminant livestock. Results from previous trials with crude quebracho and black wattle tannin indicated that cattle and/or sheep would not preferentially drink water containing these tannins. Therefore, we conducted preference trials to determine if cattle and sheep would learn to prefer water containing purified grape seed tannin (GST) that provided up to 2% of their daily dry matter (DM) intake. After gradual exposure to increasing amounts of this tannin in water during a pre-trial period, five adult ewes and five yearling heifers fed lucerne (Medicago sativa) pellets (19% CP) were offered water and several concentrations of GST solutions for either 15 (sheep trial) or 20 days (cattle trial). We measured intake of all liquids daily. Concentrations of blood urea were also measured for heifers when they drank only tannin solutions or water. Both sheep and cattle developed preferences for water with GST in it over water alone (P < 0.01) although this preference appeared earlier in the trial for sheep than for cattle. For the sheep, mean daily intake of water alone and all tannin solutions (in total) was 0.6 and 6.1 l, respectively. For the cattle, mean daily intake of water and all tannin solutions in total was 21.8 and 20.6 l, respectively, in the first half of the trial and 10.8 and 26.1 l, respectively, in the second half of the trial. Compared with the other tannin solutions, both sheep and cattle drank more of the solution with the highest tannin concentration (2% of daily DM intake as GST) than of water on more trial days (P < 0.05). Ingestion of water with the highest concentration of GST reduced blood plasma urea concentration in the cattle by 9% to 14% (P ⩽ 0.10) compared with ingestion of water alone. Results from the trials suggest that providing grape seed and perhaps other CTs via drinking water may be a practical way to introduce CTs into sheep and cattle diets.

Short communication: Assessing urea transport from milk to blood in dairy cows

The concentration of urea in milk (MUC) has emerged as a potentially useful tool to predict urinary N excretion. Various factors may affect the relationship between MUC and urinary N excretion, including transport characteristics of urea from blood to milk and vice versa. The main objective of this study was to test whether substantial transport of urea from milk to blood exists in lactating dairy cattle. The subobjectives were (1) to assess the effects of various urea gradient levels between blood and milk on urea transport from milk to blood and (2) to test the occurrence of urea transport between different compartments of the mammary gland such as the cistern and the alveoli. Urea transport was studied in 2 multiparous lactating Holstein-Friesian cows (36.0±6.18kg of milk/d; mean ± SD). In 3 separate trials, boluses of [15N15N]urea were injected in the cisterns via the teat canals at 20, 60, and 120min before the 1700-h milking at various levels of MUC and of blood plasma urea concentration (PUC). In trial 1, a primed continuous infusion of urea (105g at the start, continuing with 20g/h) into the jugular vein started at 0500 h and stopped at 0, 1, 2, and 3h before the 1700-h milking on d 1, 2, 3, and 4, respectively. In trial 2, 5.5g of urea was injected into the cisterns at 20, 60, and 120min before the 1700-h milking on d 5, 6, and 7, respectively. In trial 3, urea fluxes were measured without an experimentally induced gradient between MUC and PUC on d 8, 9, and 10, respectively. During milking, successive milk samples were taken from first to last milk. Blood and milk were analyzed for 15N-urea enrichment. Levels of 15N-urea in blood increased after injection of a [15N15N]urea bolus in milk, indicating urea transport from milk to blood. Between 21.0 and 35.3% of injected [15N15N]urea in milk was recovered after 2h. The fractional [15N15N]urea decline rate in milk varied between 0.0076 and 0.0096/min. The level of MUC, rather than the concentration gradient between MUC and PUC, appeared to affect this fractional rate of decline. Enrichment levels of 15N-urea in milk samples within a single milking showed that urea was transported from cistern milk to alveoli milk. In conclusion, the results indicate that transport of urea from milk to blood in lactating dairy cattle occurs and that urea is transported from cistern milk to alveoli milk.

Effects of different dietary threonine levels on growth and slaughter performance in finishing pigs

The objective of this study was to determine the threonine (Thr) requirement of a modern crossbred growing pig from Austria in the finisher stage (67 to 113 kg body weight). For on average 50 days, 30 castrated male and 30 female pigs were fed isonitrogenous diets (135 g/kg crude protein, 8.0 g/kg lysine) supplemented with increasing levels of crystalline Thr. Total dietary Thr contents (g/kg) were 4.9 (basal diet), 5.0, 5.4, 5.8, 6.1, 6.5, corresponding to a Thr:Lys ratio of about 0.60, 0.64, 0.68, 0.73, 0.76, 0.81. Dietary Thr concentration of 5.4 g/kg improved daily gains by about 15 percentage points (&lt;i&gt;P&lt;/I&gt; &lt; 0.05) and the feed conversion ratio by about 7 percentage points, compared to pigs fed the basal diet (4.9 g/kg Thr). Increasing dietary Thr above 5.4 g/kg had no further effects on performance. The blood plasma urea concentration was minimized at a dietary Thr concentration of 6.1 g/kg. For all treatments there was a low effect of dietary Thr supply on carcass quality. Goblet cell density in the small intestine and colon did not differ between different levels of dietary Thr. Based on the results of growth performance, an optimum total dietary Thr:Lys ratio in the finisher stage of pigs ranges from 0.66 to 0.68.

BLOOD PLASMA UREA CONCENTRATION AND ITS RELATIONSHIP WITH MILK PRODUCTION PARAMETERS IN CZECH PIED COWS

Experimental groups of 18 Czech Pied cows were observed in the course of 12 consecutive calendar months in order to describe the relationship between urea concentration in blood plasma and milk production. The cows were in early lactation, the mean number of lactation was 2.6, number of days after calving 55.6 and concentration of urea in blood plasma 5.42 mmol/l. During the fi rst 100 days of lactation milk yield amounted to 2624 kg with 3.90 % fat, 3.47 % protein and 4.86 % lactose. The calculated coefficients of the correlation between blood plasma urea concentration and milk production parameters greatly varied between test days and thus did not reveal any clear relationships. Graphic polynomials expressed the relationships better. They showed that urea concentration in blood plasma tended to have a significant positive relationship with milk fat content, and a significant negative relationship with milk protein content. The relationships between urea concentration and number of lactation, milk yield and lactose content were mainly positive while a mainly negative relationship was found with a number of days after calving.

Effect of condensed tannins on the production of wool and on its processing characteristics in sheep grazing Lotus corniculatus

The effect of condensed tannins (CT) in Lotus corniculatus upon voluntary feed intake (VFI), concentration of rumen and plasma metabolites, production of wool, and wool processing characteristics was measured in grazing ewes restricted to maintenance feeding for 125 days during summer. A rotational grazing system with restricted feed allowance with 40 mixed aged dry ewes (54±1·0 kg) was used. Half of the ewes were selected randomly for twice-daily oral polyethylene glycol (PEG; MW 3500) supplementation (CT-inactivated), with the remainder being CT-acting animals. Measurements of the diet selected, VFI, wool production, and wool processing characteristics were made. The concentration of ammonia in rumen fluid and the concentrations of methionine, cysteine, and urea in blood plasma were also measured. The diet selected contained 32 g total nitrogen (N) and 28 g total CT/kg dry matter (DM) and had an in vitro organic matter digestibility of 0·70. Action of CT reduced rumen ammonia concentration (256 v. 302 mg N/L), reduced blood plasma urea concentration (7·3 v. 8·9 µM), and increased blood plasma cysteine concentration (30 v. 27 µM) compared with sheep receiving PEG supplementation. CT had no effect on VFI but increased clean fleece weight (2·53 v. 2·28 kg/ewe) and staple length (7·7 v. 6·9 cm), but did not affect liveweight gain (54 v 67 g/day). The CT reduced dag weight and tended to reduce wool yellowness relative to sheep receiving PEG. There were no signifiant effects of CT on fibre diameter, staple strength, bulk density, and wool resilience. It was concluded that action of CT in sheep fed L. corniculatus reduced the degradation of forage protein in the rumen and the principal effect of this was to increase the efficiency of wool production, with more wool being produced at the same feed intake and the wool being of reduced yellowness.