Levels Of Protein Supply Research Articles

Changes in mammary metabolism in response to the provision of an ideal amino acid profile at 2 levels of metabolizable protein supply in dairy cows: Consequences on efficiency

The aim of this study was to compare the modifications in mammary gland metabolism by supplying an ideal versus an imbalanced essential AA (EAA) profile at low and high metabolizable protein (or PDIE, its equivalent in the INRA feeding system). Four lactating, multiparous Holstein cows received 4 treatments composed of 2 basal diets containing 2 levels of PDIE (LP or HP) and 2 different infusions of AA mixtures (AA− or AA+) in the duodenum. The AA+ mixture contained Lys, Met, Leu, His, Ile, Val, Phe, Arg, Trp, and Glu, whereas the AA− mixture contained Glu, Pro, and Ser. The infusion mixtures were iso-PDIE. The diet plus infusions provided 13.9 versus 15.8% of crude protein that corresponded to 102 versus 118g/kg of dry matter of PDIE in LP and HP treatments, respectively. The treatments were designed as a 2×2 crossover design of 2 levels of PDIE supply (LP vs. HP) with 28-d periods. Infusions of AA in the duodenum (AA− vs. AA+) were superimposed to diet within each 28-d period according to 2×2 crossover designs with 14-d subperiods. Increasing the PDIE supply tended to increase milk protein yield; however, the efficiency of PDIE utilization decreased and the plasma urea concentration increased, indicating a higher catabolism of AA. The AA+ treatments increased milk protein yield and content similarly at both levels of protein supply. This was explained by an increase in the mammary uptake of all EAA except His and Trp. The mammary uptake of non-EAA (NEAA) was altered to the increase in EAA uptake so that the total AA uptake was almost equal to milk protein output on a nitrogen basis. The ratio between NEAA to total AA uptake decreased from 46% in LPAA− to 40% in LPAA+, HPAA−, and HPAA+ treatments. The PDIE efficiency tended to increase in the AA+ versus the AA− treatments because the NEAA supply and the amount of NEAA not used by the mammary both decreased. Nevertheless, our AA+ treatments seemed not to be the ideal profile: the mammary uptake-to-output ratio for Thr was higher than 1 in LPAA−, but it decreased to 1 in all the other treatments, suggesting that Thr was deficient in these treatments. Conversely, an excess of His was indicated because its uptake was similar in AA+ and AA− treatments. In conclusion, balancing the EAA profile increased milk protein yield and metabolizable protein efficiency at both levels of protein supply by increasing the mammary uptake of EAA and altering the NEAA uptake, leading to less AA available for catabolism.

Metabolic and growth response of mink (Neovison vison) kits until 10 weeks of age when exposed to different dietary protein provision

Growth performance and metabolism were investigated in mink kits (n = 210) exposed to the same dietary treatment as their dams (n = 30), i.e. high (HP; 61% of metabolisable energy, ME), medium (MP; 48% of ME) or low (LP; 30% of ME) protein supply, from birth until 10 weeks of age. The kits were weighed weekly, and were measured by means of balance experiment and indirect calorimetry, in weeks eight and nine post-partum (p.p.). At weaning (seven weeks p.p.) and 10 weeks p.p. one kit per litter was killed and blood, liver and kidneys were collected. Plasma amino acid profiles, and hepatic abundance of mRNA for phosphoenolpyruvate carboxykinase (PEPCK), fructose 1,6-biphosphatase, pyruvate kinase and glucose-6-phosphatase (G-6-Pase) by q-PCR, were determined. There were no differences in live weights among kits the first four weeks of life when kits solely consumed milk, but male LP kits were the heaviest. After transition to solid feed MP kits weighed most at nine weeks of age (p < 0.05). At eight weeks of age, the kits fed the LP diet retained less (p < 0.05) N than HP and MP kits. Heat production did not differ among kits, although protein oxidation was higher (p < 0.001) in HP kits than in LP kits. Kits fed the LP diet had lower (p < 0.05) plasma concentrations of lysine, methionine and leucine than MP kits. Dietary treatment was not reflected in the relative abundance of any of the studied mRNAs, but kits had significantly lower abundance of all studied mRNA than their dams, ranging from 83% less PEPCK abundance to 40% less for G-6-Pase. The kidney mass was smallest (p < 0.01) in kits fed the LP diet, and liver masses were largest (p < 0.001) in HP kits. The results indicate that the LP diet did not meet the protein requirements for mink kits in the transition period from milk to solid feed. The capacity to regulate the rate of gluconeogenesis was even more limited in young mink kits than in adult dams. However, young mink kits can regulate protein oxidation in response to dietary protein supply, probably by adapting the size of the liver and kidneys to the level of protein supply.

Modelling the optimal lysine to threonine ratio in growing chickens depending on age and efficiency of dietary amino acid utilisation

1. Experiments were conducted to establish the requirements and optimal dietary ratio of lysine to threonine for fast growing male chickens (genotype Ross 308) depending on age, daily protein deposition and of dietary amino acid efficiency. 2. A total of 216 growing chickens were utilised in nitrogen-balance studies in three age periods (10 to 25 d; 30 to 45 d; 50 to 65 d) using graded levels of protein supply (60 to 360 g/kg crude protein) in lysine or threonine limiting diets. 3. Supplementation of crystalline amino acids (L-Lys, L-Thr, DL-Met and L-Arg) provided the following amino acid ratios: lysine limiting diets (Lys:Met + Cys:Thr:Arg = 1 : 1·01 : 0·91 : 1·14), threonine limiting diets (Lys : Met + Cys : Thr : Arg = 1 : 0·85 : 0·54 : 1·16). 4. The principles of the diet dilution technique using an exponential function were applied for the modelling of lysine and threonine requirements. For equal daily protein deposition, optimal lysine to threonine ratios 1 : 0·69 (10 to 25 d), 1 : 0·70 (30 to 45 d) and 1 : 0·74 (50 to 65 d) were established. 5. For the commercial growth period of fast growing chickens, the derived optimal lysine to threonine ratio was constant (1 : 0·69). The applied modelling procedure gave conclusions for quantitative requirements and optimal dietary lysine:threonine ratios in line with actual recommendations.

Control of nitrogen homeostasis: intestinal arginine metabolism regulation according to protein supply.

Portal arginine (Arg) flow plays a key role in liver ureagenesis. In the intestine, Arg can be converted into citrulline (Cit) via arginase and ornithine carbamyl-transferase (OCT). Cit can also be synthesized from glutamine via glutaminase and ornithine aminotransferase (OAT). The aim of this work was to study the regulation of these enzymes in the intestine in relation to time and level of protein supply. 48 rats were divided in 6 groups to receive a 10% (10P), 17% (17P) or 25% protein (25P) diet for either 16 hours short-term (ST) or 15 days long-term (LT). LT group urines were collected to determine N balance. At sacrifice, blood was collected for plasma amino acid measurement, and the intestinal mucosa was removed for enzyme expression and activity analysis (results are given as means ± SEM, ANOVA + Newman-Keuls test [∗ vs. 17P: p < 0.05]). N balance remained similar in all groups. Cit plasma levels at LT varied with diet (10P: 87 ± 2 ∗; 17P: 69 ± 4; 25P: 88 ± 5 ∗ in mM). There was an increase in ileum at ST in arginase activity under 25P and 10P diets (respectively 46 ± 2 and 46 ± 2 vs. 36 ± 3 (17P) in μmol/g/min) and at LT, in OAT expression in the 10P group (+ 277 %∗). With an hypoproteic diet, Cit synthesis appears to be ensured by either OAT activation at LT or arginase at ST. Surprisingly, both low and high protein diets increased Cit production. Research is needed to gain further insight into the regulation of this complex metabolic network.

High versus low protein diets to mink‐postprandial plasma urea and creatinine response, osmotic load and pattern of nitrogen and electrolyte excretion

Nitrogen balance, pattern of excretion of nitrogenous end‐products, endogenous urinary N excretion, postprandial plasma urea and creatinine, osmotic load, urinary electrolyte excretion and water intake/output relationships were studied in 12 adult female mink fed a high protein diet (HP; n=6) providing about 155g protein/kg or a low protein diet (LP; n=6) providing about 95 g protein/kg. Two balance periods of each 3 d were used and diets were fed raw or cooked. After the last balance period followed a 48 h fasting period. Postprandial plasma urea and creatinine were studied for 48 h following a test meal given after an overnight fast. Osmotic load was determined based on collection of non‐acidified urine carried out during 48h. Level of protein supply did not affect N balance, being close to zero, whereas slightly negative balances were achieved for fasting animals. Protein supply was clearly reflected in excretion of urinary urea and allantoin but not in creatinine and uric acid. Endogenous urinary N excretion was estimated by a second order regression equation giving an intercept of 280mg/kg0.75. Post‐prandial plasma urea concentrations were strongly influenced by protein supply, HP animals having substantially higher peaks than LP animals, but values returned to fasting values within 24 h after the test meal. Plasma creatinine followed a biphasic pattern with a peak about 2 h after feeding and a nadir approximately 6 h after feeding. Physical form of diet influenced postprandial urea, animals fed raw diets having a higher peak, but not creatinine. The HP diet provided almost the double osmotic load of the LP diet and a corresponding increase in urine volume. The resulting water balances were identical irrespective of diet, showing that water intake/output relationships are very accurately regulated.

Effect of timing and level of protein supply on silage intake, feeding behaviour and milk yield of lactating dairy cattle

Previous studies have shown that the timing of supplement distribution and supplement type can have implications on forage intake and/or production. For example, Robinson et al. (1997) showed that feeding a protein supplement at 00.30 h compared with 08.30 h increased fat yield through stimulation of rumen fermentation. The objective of the present trial was to test the hypothesis “that supplying a protein supplement either before or after silage was offered would affect feeding pattern and silage intake”.Twelve multiparous cows, with average starting milk yield of 25.4 (s.d. 5.95) kg/day were allocated to one of six treatments in an incomplete Latin square with four periods of 21 days. Grass silage (219 g/kg DM, 151 g CP/kg DM) was fed ad libitum mixed with barley in the ratio 3:1 on a DM basis.

Bestimmung von kinetischen Parametern des Proteinmetabolismus bei wachsenden Ratten in Verbindung mit Energieumsatzmessungen. 2. Mitteilung. Bestimmung des Energiebedarfs für den Proteinansatz in Verbindung mit Messungen der Proteinsyntheserate auf unterschiedlichen Niveaus der Proteinversorgung

Energy metabolism-by means of indirect calorimetry-and kinetic parameters of the protein metabolism on the basis of the 3-compartment model were measured with 4 groups of 4 or 5 male Wistar rats in the growth range of between 70 and 230 g live weight in a total of 5 alternately successive periods at the feeding levels growth and energy maintenance as well as 4 different levels of protein supply (6, 10, 17 and 26% crude protein in the feed). The partial energy requirement values for protein retention (bp) for every animal and every period are calculated from the data of energy metabolism. On an average of the 3 growth periods they amounted to 1.75 +/- 0.37 kJ/kJ. A statistically significant linear relation with a slope of approximately 1 could be derived regressively between the protein synthesis rate and the protein retention rate, including all 5 test periods. There was no proven relation between the bp values and the corresponding individual values of the ratio of protein synthesis rate-diminished by the regressively derived protein synthesis rate in the N balance-to the protein retention rate. The results do not permit proven statements on the quantitative relations between protein turnover and energy requirement for protein retention, which is first of all due to methodical shortcomings in measuring both protein metabolism and energy metabolism. They indicate, however, that the heat production from protein synthesis has only a relatively low share in the additional energy expenditure for protein retention and does not considerably surpass the necessary minimal cost for the synthesis of the deposited protein in growing rats.

The energy maintenance requirement of growing pigs of different sexes given normal and high protein diets. 3. Experiments in boars

Six fattening boars each, hybrids of line 150(150 X (L X E] received rations with 17 and 45% crude protein. In the live weight range of 36 to 167 kg, 5 periods of growth feeding alternated with 4 periods of maintenance feeding. Compared with maintenance level the nutrition level of 2.7 did not have an influence on digestibility. Nitrogen retention was only insignificantly influenced by the level of protein supply. The maintenance requirement of the animals used was by 50% higher than in previous experiments made by our work team. On average it amounted to 1,017 KJ metabolizable energy per kg LW0.62, i.e. to 1,063 for those animals fed with rations containing 17% crude protein and to 986 for those animals receiving 45% crude protein in their rations. The utilization of metabolizable energy for energy retention amounted to 75% for rations with 17% crude protein and to 70% for rations with 45% crude protein. The partial utilization of metabolizable energy for fat retention was ascertained as 90% and for protein retention as 53% by means of multiply regressive assessment.

Effect of graduated protein supply (0-50%) on hematologic values as well as protein and urea concentrations in the plasma of rats

The influence of graduated protein supply (0-50% casein) on hematological values was studied in growing rats and compared with other criteria of the supply status. The following results were obtained: Weight development was found to reflect to 30%, the plasma protein content to 40% the level of protein supply. The highest protein levels revealed a trend towards lower values. At a dietary protein content of 15 to 20%, the urea concentrations of plasma went through a minimum. Both with better and with poorer protein supply they proved higher thus suggesting an increasingly energetic conversion of the feed protein. The hematological values hemoglobin, hematocrit and erythrocyt number responded uniformaly to the level of protein supply. This is also attributable to the close statsitical relationship between these three magnitudes. Whilst at the end of the experiment the erythrocyt number with protein-free diet proved lowest, the smallest values for hemoglobin and hematocrit were observed with 5% protein. From 10% on the differences were not so marked. Especially high values were measured, however, for all criteria at 40 and 50%, partly at 25% protein. As the calculation of the mean cell volume (MCV) revealed, insufficient protein supply is likely to affect rather the erythrocyt ripening than iron conversion. In agreement with this idea, the mean corpuscular hemoglobin concentration (MCHC) was not found to be influenced by protein supply.