Amino Acid Flow Research Articles

Rumen digestion kinetics, microbial yield, and omasal flows of nonmicrobial, bacterial, and protozoal amino acids in lactating dairy cattle fed fermentation by-products or urea as a soluble nitrogen source

The objective of this study was to evaluate the effect of a fermentation by-product on rumen function, microbial yield, and composition and flows of nutrients from the rumen in high-producing lactating dairy cattle. Eight ruminally cannulated multiparous Holstein cows averaging (mean ± standard deviation) 60 ± 10 d in milk and 637 ± 38 kg of body weight were randomly assigned to 1 of 2 treatment sequences in a switchback design. Treatment diets contained (dry matter basis) 44% corn silage, 13% alfalfa silage, 12% ground corn, and 31% protein premix, containing either a control mix of urea and wheat middlings (CON) or a commercial fermentation by-product meal (Fermenten, Arm and Hammer Animal Nutrition, Princeton, NJ) at 3% diet inclusion rate (EXP). The trial consisted of three 28-d experimental periods, where each period consisted of 21 d of diet adaptation and 7 d of data and sample collection. A triple-marker technique and double-labeled 15N15N-urea were used to were used to measure protozoal, bacterial, and nonmicrobial omasal flow of AA. Rumen pool sizes and omasal flows were used to determine digestion parameters, including fractional rates of carbohydrate digestion, microbial growth, and yield of microbial biomass per gram of degraded substrate. Fermentation by-product inclusion in EXP diets increased microbial N and amino acid N content in microbes relative to microbes from CON cows fed the urea control. Microbial AA profile did not differ between diets. Daily omasal flows of AA were increased in EXP cows as a result of decreased degradation of feed protein. The inclusion of the fermentation by-product increased nonmicrobial AA flow in cows fed EXP versus CON. Average protozoal contribution to microbial N flow was 16.8%, yet protozoa accounted for 21% of the microbial AA flow, with a range of 8 to 46% for individual AA. Cows in this study maintained an average rumen pool size of 320 g of microbial N, and bacterial and protozoal pools were estimated at 4 different theoretical levels of selective protozoa retention. Fractional growth rate of all microbes was estimated to be 0.069 h-1, with a yield of 0.44 g of microbial biomass per gram of carbohydrate degraded. Results indicated that fermentation by-product can increase omasal flow of AA while maintaining adequate rumen N available for microbial growth and protein synthesis. Simulations from a developmental version of the Cornell Net Carbohydrate and Protein System indicated strong agreement between predicted and observed values, with some areas key for improvement in AA flow and bacterial versus protozoal N partitioning.

When insecticide spraying ceases prematurely Tetranychus urticae mites are not killed by predators, they wither and die in situ

An outbreak of spider mites on apple trees sprayed with insecticide collapsed when spraying was stopped prematurely. But mites were not taken by predators. They remained at their feeding site but became torpid, withered and died. This observation supports earlier evidence that mites increase because the application of insecticide caused protein in the leaves to break down releasing soluble amino acids into the sap. This improved the nutrition of the mites, allowing them to increase. But when spraying was stopped at the height of an outbreak this flow of amino acids ceased and the mites starved from the consequent decline in their nitrogen nutrition.

Multiple effects of secondary metabolites on amino acid cycling in white clover rhizosphere

Secondary metabolites secreted by microbes and plants act as mediators in plant-microbe interactions including nutrient uptake. However, until now very little is known about their role in nutrient assimilation, particularly amino acids, which are important compounds due to their high N content. Here we show that the addition of flavonoid secondary metabolites, derived from clover, to soil changed the bacterial diversity, enhanced the flux of asparagine, and increased the pools of glutamine/glutamate in the soil. This indicates that flavonoids are functionally important qualitative and quantitative components of clover root exudates. Furthermore, the addition of microbial secondary metabolites negatively affected clover uptake of asparagine and plant performance, which demonstrates that microbial competition for nutrients may have multiple physiological targets in the plant. Finally, the detection of intact asparagine in clover roots confirms that amino acid uptake is significant to the plant in agricultural soil. In conclusion, amino-acid flow in the clover rhizosphere can be modified by the effects of clover-derived flavonoids on the bacterial community structure, which affects the flux and pools of amino acids; microbial secondary metabolites, which reduce clover uptake of asparagine; and direct recapture of amino acids by clover.

RUMINANT NUTRITION SYMPOSIUM: Effects of postruminal flows of protein and amino acids on small intestinal starch digestion in beef cattle.

Many nutritionists adopt feeding strategies designed to increase ruminal starch fermentation because ruminal capacity for starch degradation often exceeds amounts of starch able to be digested in the small intestine of cattle. However, increases in fermentable energy supply are positively correlated with increased instances of metabolic disorders and reductions in DMI, and energy derived by cattle subsequent to fermentation is less than that derived when glucose is intestinally absorbed. Small intestinal starch digestion (SISD) appears to be limited by α-glycohydrolase secretions and a precise understanding of digestion of carbohydrates in the small intestine remains equivocal. Interestingly, small intestinal α-glycohydrolase secretions are responsive to luminal appearance of milk-specific protein (i.e., casein) in the small intestine of cattle, and SISD is increased by greater postruminal flows of individual AA (i.e., Glu). Greater flows of casein and Glu appear to augment SISD, but by apparently different mechanisms. Greater small intestinal absorption of glucose has been associated with increased omental fat accretion even though SISD can increase NE from starch by more than 42% compared to ruminal starch degradation. Nonetheless, in vitro data suggest that greater glucogenicity of diets can allow for greater intramuscular fat accretion, and if greater small intestinal absorption of glucose does not mitigate hepatic gluconeogenesis then increases in SISD may provide opportunity to increase synthesis of intramuscular fat. If duodenal metabolizable AA flow can be altered to allow for improved SISD in cattle, then diet modification may allow for large improvements in feed efficiency and beef quality. Few data are available on direct effects of increases in SISD in response to greater casein or metabolizable Glu flow. An improved understanding of effects of increased SISD in response to greater postruminal flow of Glu and casein on improvements in NE and fates of luminally assimilated glucose could allow for increased efficiency of energy use from corn and improvements in conversion of corn grain to beef. New knowledge related to effects of greater postruminal flow of Glu and casein on starch utilization by cattle will allow nutritionists to more correctly match dietary nutrients to cattle requirements, thereby allowing large improvements in nutrient utilization and efficiency of gain among cattle fed starch-based diets.

Effects of bismuth subsalicylate and dietary sulfur level on fermentation by ruminal microbes in continuous culture.

In ruminants, excess dietary sulfur can be associated with a reduction in DM intake, poor feedlot performance and sulfur-associated polioencephalomalacia. Bismuth subsalicylate (BSS) has been shown to decrease hydrogen sulfide in vitro. The objective of this experiment was to evaluate effects of BSS inclusion (0 or 0.5% of diet DM) and dietary sulfur (0.21 or 0.42% of diet DM) on microbial fermentation in continuous culture. Treatments were arranged in a 2 × 2 factorial design. Eight dual-flow continuous culture fermenters were used during 2 consecutive 10-d periods consisting of 7 d for stabilization followed by 3 d of sampling. A pelleted feedlot diet containing 39% dry rolled corn, 32% earlage, 21% wet distillers grains, 3.2% corn silage, 1.5% soybean meal, 0.6% urea and 2.7% mineral premix (DM basis) was provided as substrate for microbes at a rate of 75 g of DM × fermenter–1 × d–1. Effluents from sampling days were composited by fermenter within period, resulting in 4 replicates/treatment. Bismuth subsalicylate inclusion decreased (P < 0.01) true OM digestion, while no effects were observed for NDF and ADF digestion. Total VFA concentrations, molar proportions of acetic, propionic, and branched-chained VFA decreased (P < 0.01) with BSS addition. The ratio of acetic to propionic acid and the molar proportion of butyric acid increased (P < 0.01) with BSS addition. In regard to nitrogen metabolism, BSS increased NH3–N concentration, NH3–N and dietary-N flows (P < 0.01), and decreased non-NH3–N flow, microbial-N flow, CP degradation, and efficiency of microbial protein synthesis (P < 0.01). Inclusion of BSS increased mean, minimum, and maximum fermentation pH (P < 0.01). Amount of dietary sulfur and BSS inclusion influenced flows of amino acids and fatty acids from fermenters. Influences on fatty acid biohydrogenation and amino acid flows demonstrated an overall suppression of microbial fermentation. Results from this experiment indicate that BSS inclusion at 0.5% of diet DM has detrimental effects on in vitro rumen fermentation in continuous culture.

Apparent and standardized ileal nutrient digestibility of broiler diets containing varying levels of raw full-fat soybean and microbial protease

BackgroundAlthough soybean meal (SBM) is excellent source of protein in diets for poultry, it is sometimes inaccessible, costly and fluctuates in supply. The SBM can partially be replaced by full-fat SBM, but the meals prepared from raw full-fat soybean contain antinutritional factors. To avoid the risk of antinutritional factors, heat treatment is always advisable, but either excessive or under heating the soybean could negatively affect the quality. However, the potential for further improvement of SBM by supplementing with microbial enzymes has been suggested by many researchers. The objective of this study was to evaluate the performance and ileal nutrient digestibility of birds fed on diets containing raw soybeans and supplemented with microbial protease.MethodsA 3 × 2 factorial, involving 3 levels of raw full-fat soybean (RFFS; 0, 45 or 75 g/kg of diet) and 2 levels of protease (0 or 15,000 PROT/kg) was used. The birds were raised in a climate-controlled room. A nitrogen-free diet was also offered to a reference group from day 19 to 24 to determine protein and amino acid flow at the terminal ileum and calculate the standardized ileal digestibility of nutrients. On days 10, 24 and 35, body weight and feed leftover were recorded to calculate the body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR). On day 24, samples of ileal digesta were collected at least from two birds per replicate.ResultsWhen RFFS was increased from 0 to 75 g/kg of diet, the content of trypsin inhibitors was increased from 1747 to 10,193 trypsin inhibitors unit (TIU)/g of diets, and feed consumption of birds was also reduced (P < 0.05). Increasing RFFS level reduced the BWG from hatch 0 to 10 d (P < 0.01) and hatch to 24 d (P < 0.05). The BWG of birds from hatch to 35 was not significantly (P = 0.07) affected.Feed intake was also reduced (P < 0.05) during 0 to 35 d. However, protease supplementation improved (P < 0.05) the BWG and FCR during 0 to 24 d. Rising levels of RFFS increased the weight of pancreas (P < 0.001) and small intestine (P < 0.001) at day 24. Except for methionine, apparent and the corresponding standardized ileal digestibility of CP and AA were reduced (P < 0.01) by increasing levels of RFFS in diets.ConclusionThis study showed that some commercial SBM could be replaced by RFFS in broiler diets, without markedly compromising productivity. The AID and SID of CP and lysine were slightly improved by dietary supplementation of microbial protease.

749 Effects of postruminal flows of protein and amino acids on small intestinal starch digestion in cattle

A large amount of cattle in the United States are fed starch-based diets because limitations to efficient production of meat and milk by cattle are frequently associated with limits in NE. Many nutritionists adopt feeding strategies designed to increase ruminal starch fermentation because ruminal capacity for starch degradation often exceeds amounts of starch able to be digested in the small intestine of cattle. However, increases in fermentable energy supply are positively correlated with increased instances of metabolic disorders and reductions in DMI, and energy derived by cattle subsequent to fermentation is less than that derived when glucose is intestinally absorbed. Apparently, small intestinal starch digestion (SISD) is limited by α-glycohydrolase secretions and a precise understanding of digestion of carbohydrates in the small intestine remains equivocal. Interestingly, small intestinal α-glycohydrolase secretions are responsive to luminal appearance of high-quality protein (i.e., casein) in the small intestine of cattle, and SISD is increased by greater postruminal flows of individual AA (i.e., Glu). Indeed, greater flows of casein and Glu appear to augment SISD but by apparently different mechanisms. Greater small intestinal absorption of glucose has been associated with increased omental fat accretion even though SISD can increase NE from starch by more than 42% compared to ruminal starch degradation. Nonetheless, in vitro data suggest that greater glucogenicity of diets can allow for greater intramuscular fat accretion, and if greater small intestinal absorption of glucose does not mitigate hepatic gluconeogenesis then increases in SISD may provide opportunity to increase synthesis of intramuscular fat. If duodenal metabolizable AA flow can be altered to allow for improved SISD in cattle, then diet modification may allow for large improvements in feed efficiency and beef quality. Few data are available on direct effects of increases in SISD in response to greater casein or metabolizable Glu flow. An improved understanding of effects of increased SISD in response to greater postruminal flow of Glu and casein on improvements in NE and fates of luminally assimilated glucose could allow for increased efficiency of energy use from corn and improvements in conversion of corn grain to beef. New knowledge related to effects of greater postruminal flow of Glu and casein on starch utilization by cattle will allow nutritionists to more correctly match dietary nutrients to cattle to allow large improvements in nutrient utilization and efficiency of gain among cattle fed starch-based diets.

Protein Kinetics and Metabolic Effects Related to Disease States in the Intensive Care Unit.

Evaluating protein kinetics in the critically ill population remains a very difficult task. Heterogeneity in the intensive care unit (ICU) population and wide spectrum of disease processes creates complexity in assessing protein kinetics. Traditionally, protein has been delivered in the context of total energy. Focus on energy delivery has recently come into question, as the importance of supplemental protein in patient outcomes has been shown in several recent trials. The ICU patient is prone to catabolism, immobilization, and impaired immunity, which is a perfect storm for massive loss of lean body tissue with a unidirectional flow of amino acids from muscle to immune tissue for immunoglobulin production, as well as liver for gluconeogenesis and acute phase protein synthesis. The understanding of protein metabolism in the ICU has been recently expanded with the discovery of how the mammalian target of rapamycin complex 1 is regulated. The concept of "anabolic resistance" and identifying the quantity of protein required to overcome this resistance is gaining support among critical care nutrition circles. It appears that a minimum of at least 1.2 g/kg/d with levels up to 2.0 g/kg/d of protein or amino acids appears safe for delivery in the ICU setting and may yield a better clinical outcome.

Metabolisable protein supply to lactating dairy cows increased with increasing dry matter concentration in grass-clover silage

The aim of this experiment was to study the effect of increased dry matter (DM) concentration in grass-clover silage, obtained by extending the pre-wilting period before ensiling, on the amount of metabolisable protein (MP) supplied to lactating dairy cows. Spring growth and first regrowth of grass-clover swards grown by two Danish organic farmers were cut and pre-wilted to a planned DM concentration of 350 and 700g/kg, respectively, giving in total eight silages with DM concentrations ranging from 283 to 725g/kg. Four Holstein dairy cows in late lactation with fistulae in rumen, duodenum and ileum were included in a crossover design, with five periods of 21 d. The cows were fed ad libitum with the experimental silages without any concentrate, but with daily supply of minerals and vitamins. Feed intake was registered daily and in the last week of each period 12 subsamples of duodenal and ileal chyme and faeces, respectively, were collected over 94h to cover the diurnal variation, pooled, and subsequently analysed. Rumen fluid was collected in same sampling procedure. To estimate the duodenal flow of microbial protein, microbes were isolated from the rumen and analysed for amino acids (AA) and purines. Methane (CH4) production was measured the last two days in each period in open-circuit respiration chambers. Results were analysed using a linear random regression model with DM concentration as fixed effect, cow and cut number x farmer as random intercepts and with a cut number x farmer random slope. The amount of AA digested in the small intestine increased (P=0.024) by 5.59g/kg DM intake with each increase in silage DM concentration of 100g/kg. The increased digestion of AA in the small intestine was caused by a higher small intestinal digestibility of AA and a tendency towards a higher duodenal flow of AA. The higher duodenal flow of AA derived from a lower rumen degradation of feed protein and a tendency towards a higher microbial synthesis in the rumen. Fibre digestibility and CH4 production were not affected by silage DM concentration. In conclusion, MP concentration in grass-clover silage can be improved by pre-wilting to a higher DM concentration before ensiling.

The effects of different dietary crude protein level on faecal crude protein and amino acid flow and digestibility in growing pigs

ABSTRACTThis study was conducted to evaluate the effects of dietary crude protein (CP) level on faecal CP and amino acid (AA) flow and digestibility, faecal and ileal digesta microbial AA composition. Eighteen Duroc × Landrace × Yorkshire barrows (60 ± 1.43 kg) were randomly divided into 3 groups with 6 barrows in each, and fed a maize–soybean meal diet at the 10% (L-CP), 13% (M-CP) and 16% (H-CP) CP levels. The results indicated the faecal total N, CP, total AA (TAA) flow increased linearly (P < 0.05) whereas dietary CP concentration increased from 10% to 16%. The DM digestibility, CP digestibility, TAA digestibility, essential amino acid and non-essential amino acid digestibility decreased linearly (P < 0.05), whereas dietary CP concentration increased from 10% to 16%. Compared with pigs in M-CP and L-CP groups, pigs in the H-CP group had higher Asp, Cys, His, Arg flow in the faeces (P < 0.05). Compared with pigs in the L-CP group, pigs in M-CP and H-CP groups had less faecal Glu, Ala, Tyr, Pro, Val, Ile, Leu and flow (P < 0.05). Faecal microbial N and AA in the L-CP group was the highest in three groups. Pigs fed a corn–soybean meal-based diet reduced in protein concentration have lower faecal N flow.

Forragens taniníferas na produção de caprinos e ovinos

Tannins are a complex group of polyphenolic compounds, derived from secondary plant metabolism. The aim of this study was to conduct a survey of information on the effects of using tanninipherous forage on ruminal parameters, intake and digestibility of nutrients, weight gain and carcass traits, milk production and composition, wool production activity and anti- helminth in sheep and goats. At moderate concentrations (20-40 g/kg DM), tannins reduce the ruminal degradation of dietary protein and increase the post-rumen flow of essential amino acids. In tannin rich diets (> 50 g/kg DM) there is formation of insoluble complexes, mainly with the protein diet, which damage the digestibility of nutrients, reduce voluntary intake due to diet astringency, and damage microbial activity and ruminal digestive efficiency. In the presence of soluble tannins, ruminal bacterial species responsible for endoglucanase activity and methanogenic bacteria are affected. To mitigate the effects of tannins and other secondary compounds in tropical and temperate fodder, polyethylene glycol (PEG) has been used. Positive effects are characterized by an increase in milk production, an altered fatty acid profile of milk and meat, wool growth, and weight gain. The parasitic infections are reduced with the tannins presence due to the reduction in the availability of nutrients for nematodes, complexing the tannins glycoprotein cuticle of the worms and toxic effect on the abomasal and intestinal mucosa. It is suggested that tannin concentrations do not exceed 6-7% of the diet dry matter. Therefore, more research is required in order to clarify the issues related to this topic.

Basal endogenous losses of amino acids in protein nutrition research for swine and poultry

In this review, the definition and terminology of amino acid (AA) digestibility and ileal endogenous losses of AA (IAAend) in poultry and swine nutrition are discussed. Compared with apparent (AID) and true (TID) ileal digestibility, standardised ileal digestibility (SID) of AA is recommended for the expression of digestible AA contents of feed ingredients and for describing nutritional requirements of poultry and swine. To determine the SID of AA, total ileal flow of AA should be corrected for basal IAAend. Therefore, the measurement of basal IAAend is of great importance for the accuracy of the SID estimation in feed ingredients. The techniques for measuring basal IAAend in poultry and swine include the use of a nitrogen-free diet (NFD), a highly digestible or enzyme hydrolyzed protein diet, and the regression method. The classic method for basal IAAend determination involves the feeding of a NFD to experimental animals and measuring the ileal AA flow. This IAAend output is considered as basal IAAend, and it is assumed that the excretion of basal IAAend depends only on DM intake, regardless of dietary composition. There are criticisms with the NFD method about the abnormal physiological state induced by severe AA deficiency. Although this AA deficiency may affect the estimate of basal IAAend for dispensable AA, especially proline and glycine because of the degradation of body protein, the NFD method is still the most widely used method for basal IAAend measurements. According to the definition of basal IAAend, the NFD should be the preferred methodology in SID determination, because the basal IAAend should be only related to dry matter intake. Additionally, the SID coefficients in feed ingredients generated by NFD method are considered to be additive in a complete diet. However, the results generated from NFD method can vary among studies due to the variance in the experimental animals and diet composition. To improve the accuracy of estimating the SID of AA in feed ingredients, it is suggested that a mandatory NFD be included in individual studies to generate basal IAAend for correcting total ileal amino acid flow in determining SID of AA. In addition, research is needed to investigate the standard diet formulation of NFD.

Amino acid utilization of lactating dairy cows when diets are changed from an alfalfa-based diet to cereal straw-based diets

This experiment assessed the utilization of amino acids (AA) by the mammary gland of cows when diets are changed from an alfalfa hay-based diet (AH) to cereal straw-based diets using corn stover (CS) or rice straw (RS). Thirty multiparous Holstein dairy cows were selected and randomly assigned to 1 of 3 treatments (n=10). After 13 weeks’ feeding, arterial and venous plasma were collected every 6h over 2days and AA concentrations measured. The cows fed the CS or RS diet had lower milk and protein yield despite similar dry matter intake. The digestive AA flow was predicted to be lower in the cows fed CS or RS than in AH-fed cows. The arterial concentration of methionine and valine was lower in the cows fed RS than in cows fed AH. The mammary uptake of most essential AA, especially branched-chain AA, methionine, and arginine, was greater in the AH-fed cows than in cows fed CS or RS. The ratio of mammary uptake to milk output of methionine was lower in the RS-fed cows than that in the cows fed AH, with a value below 1 for both. In summary, the insufficient supply of free AA from arterial plasma presented to the mammary gland and lower mammary plasma flow restrict the mammary AA uptake for milk protein synthesis when energy is limited. On the other hand, the utilization of leucine and methionine may be a limiting factor for milk protein synthesis and lactation performance when corn stover or rice straw is fed to dairy cows.

786 GLP-2 Analogues Increase the Splanchnic Flow of Amino Acids in Patients with Massive Intestinal Loss Dependent on Home Parenteral Nutrition

786 GLP-2 Analogues Increase the Splanchnic Flow of Amino Acids in Patients with Massive Intestinal Loss Dependent on Home Parenteral Nutrition

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Effects of the dietary ratio of ruminal degraded to undegraded protein and feed intake on intestinal flows of endogenous nitrogen and amino acids in goats

This study was conducted to evaluate the effects of the dietary ratio of ruminal degraded protein (RDP) to ruminal undegraded protein (RUP) and the dry matter intake (DMI) on the intestinal flows of endogenous nitrogen (N) and amino acids (AA) in goats. The experiment was designed as a 4 × 4 Latin square using four ruminally, duodenally and ileally cannulated goats. The treatments were arranged in a 2 × 2 factorial design; two ratios of RDP to RUP (65:35 and 45:55, RDP1 and RDP2, respectively) and two levels at 95% and 75% of voluntary feed intake (DMI1 and DMI2, respectively) were fed to the goats. There were no significant differences in the N intake, duodenal flow of total N, undegraded feed N, microbial N, endogenous N or ileal flow of endogenous N, but the duodenal and ileal flow of endogenous N numerically decreased by approximately 22% and 9%, respectively, when the feed intake changed from DMI1 (0.63 kg/d) to DMI2 (0.50 kg/d). The dietary ratio of RDP to RUP had significant effects (p < 0.05) on the ileal flows of endogenous leucine, phenylalanine and cysteine. The present results implied that the duodenal flows of endogenous N and AA decreased when the dietary RDP to RUP ratio and DMI decreased, and the flow of endogenous AA at the ileum also decreased when the DMI decreased but increased with decreasing RDP to RUP ratios.

Standardized and true ileal amino acid digestibilities in field pea and pea protein isolate fed to growing pigs

Four ileal-cannulated Cotswold barrows (50.41 ± 5.05 kg body weight) were used to determine apparent (AID), standardized (SID) and true (TID) ileal digestibility of amino acids (AA) in field pea and pea protein isolate (PPI) processed from the same batch of the whole field pea. Pigs were allotted to 2 experimental diets in a simple cross-over design. Diets contained either field pea or PPI as the sole source of protein and were formulated to contain 155 g/kg CP. The AID of nutrients was determined by the indicator method. The SID of AA was calculated using published values for basal endogenous AA losses obtained from our laboratory. The total endogenous flow of lysine and the TID of lysine were determined by the homoarginine method. The TID of AA other than lysine were estimated using their published ratios in endogenous protein relative to lysine. The AID coefficient of CP (0.88 vs. 0.80), Ile (0.91 vs. 0.79), leucine (0.92 vs. 0.81), lysine (0.93 vs. 0.84), phenylalanine (0.92 vs. 0.84) and valine (0.89 vs. 0.76) were greater (P < 0.05) in PPI than in field pea. The total (363 vs. 2167 mg/kg [dry matter intake (DMI)] and endogenous (312 vs. 1777 mg/kg DMI) lysine flow were lower (P < 0.05) in PPI compared with field pea. Likewise, field pea had greater (P < 0.05) total and endogenous nitrogen (N) and AA (other than lysine) flow compared with PPI. The SID of indispensable AA for PPI was greater (P < 0.05) than that for field pea. However, PPI and field pea were similar in the TID of all indispensable amino acid except lysine whose TID coefficient in PPI (0.99) was greater (P < 0.05) than for field pea (0.94). In conclusion, the results indicate that processing of field pea to produce pea protein isolate improved apparent AID of AA and reduced ileal endogenous AA losses. However, the processing of field pea to produce pea protein isolate had limited effect on TID of AA.

Standardized ileal amino acid digestibility of expeller-extracted canola meal subjected to different processing conditions for starter and grower broiler chickens

Six expeller-extracted canola meal (ECM) samples produced under different seed conditioning temperatures (90, 95, or 100°C) and screw torques in the second press (low or high) were evaluated in a 3 × 2 factorial arrangement of treatments to determine the effect of processing on standardized ileal amino acid digestibility (SID) in 10 and 24-day-old broilers. A nitrogen-free diet was fed to determine ileal endogenous amino acid flow. Each diet was fed for 5 d to 6 replicate cages of 10 or 7 chicks, and ileal samples were collected at 10 and 24 d, respectively. The endogenous flow (mg/kg DM intake) of CP and all amino acids except Cys decreased (P < 0.01) with age. Conditioning temperature by screw torque interactions were detected (P < 0.05) for apparent ileal digestibility (AID) of CP, Arg, Ile, Lys, Phe, Thr, Ala, Asp, Glu, Pro ,and Ser at d 10, and the same trend was observed at d 24 except for Ile, Phe, Ala, and Pro (P > 0.05). Meals processed under medium conditioning temperature (95°C) at either low or high screw torque had the greatest (P < 0.05) AID of CP and total amino acids. The SID values followed a similar pattern as AID at both ages. When corrected for endogenous losses, the average AID of total amino acids improved approximately 3.5 and 2.0 units, at 10 and 24 d, respectively. The AID and SID values increased (P < 0.05) with age for most AA, but the effect of age was not consistent between ECMs. A negative correlation was detected between NDF and neutral detergent-insoluble nitrogen (NDIN) content of the meals and SID values of Lys at d 24 (r = −0.79, r = −0.76; P = 0.001, respectively). Processing conditions affected CP and amino acid digestibility, likely because of alterations to the chemical composition of ECM and formation of indigestible complexes of amino acids with fiber. The AID and SID values increased with age independent of meal processing conditions.

Relationships between circulating plasma concentrations and duodenal flows of essential amino acids in lactating dairy cows

The objective of this study was to better define essential AA (EAA) requirements in lactating dairy cows through examination of the relationship between plasma essential AA concentration (p[EAA]) and predicted duodenal flow of essential AA (EAAduo). Our hypothesis was that at a given level of milk protein output, p[EAA] would remain steady in response to increasing EAAduo until the EAA requirement was met, at which point p[EAA] would increase rapidly in response to greater duodenal flow of EAA until p[EAA] reached a plateau as other body processes degraded excess EAA to avoid toxicity. Thus, the requirement of each EAA would be fulfilled when p[EAA] increased rapidly. To investigate this hypothesis, we compiled a literature database that included 102 studies with 420 treatment means that reported p[EAA], dietary nutrient content, body weight, and milk production. A second database was produced to validate relationships developed in the first database and included 32 studies with 98 treatment means. All relationships were evaluated as regression equations with study as a random factor. Breed, days in milk, body weight, and milk protein production had no effect on the plasma concentration of any EAA. Other than metabolizable protein supply, nutritional content of the rations did not affect p[EAA]. Only p[Arg] was affected by parity, with primiparous cows having higher concentrations of Arg than older cows. No break points in the relationship between p[EAA] versus EAAduo were detected as either steep increases or plateaus. Plasma Arg, Ile, Lys, Thr, and Val concentrations were best associated with their respective EAAduo as quadratic equations, whereas His, Leu, Met, and Phe were associated only linearly. Adding a quadratic term improved the adjusted R2 or decreased the root mean square error marginally (<2.0%). Thus, we conclude that the main effect of EAAduo on p[EAA] is linear. Abomasal or duodenal infusions of Met, Lys, His, Lys+Met, and casein revealed that Met or Lys infused alone increased the plasma concentration of the infused EAA and lowered the concentration of other EAA, particularly His. Infusion of Lys+Met or His alone was associated with increases in concentrations of these EAA without affecting others. We conclude that over a wide range of protein intakes in lactating cows, plasma levels of EAA increase linearly with duodenal flow. No evidence was found that EAA requirements are reflected in blood plasma concentrations.

Impact of a tannin extract on digestibility, ruminal fermentation and duodenal flow of amino acids in steers fed maize silage and concentrate containing soybean meal or canola meal as protein source

SUMMARYFour Holstein steers (297 ± 56 kg of body weight (BW)) fitted with duodenal cannula and rumen catheter, were housed in metabolism cages and used in a 4 × 4 Latin Square trial to evaluate the effect of both protein source andAcacia mearnsiitannin extract on digestibility, ruminal fermentation, rumen microbial protein synthesis, N utilization and on duodenal flow of individual amino acids. The diet was offered at restricted amount of 25 g of dry matter (DM)/kg BW and consisted of maize silage plus concentrate, in a proportion of 0·7:0·3 (DM basis) respectively. Concentrate was formulated with either soybean meal or canola meal as protein source, with or without 50 g/kg ofA. mearnsiitannin extract (i.e. 15 g/kg of total dietary DM). There was no effect of protein source on most variables. The apparent and true organic matter (OM) digestibilities, as well as neutral detergent fibre (NDF) digestibility were negatively affected by tannin extract inclusion without, however, affecting digestible OM intake. The amount of nitrogen (N) excreted in faeces increased whereas the urinary N excretion decreased in tannin extract treatments. No interaction time × treatment was detected for any rumen variable and no treatment effect was observed for rumen fluid pH and reducing sugars concentration. Rumen fluid concentration of ammonia N was lower for the canola meal plus tannin extract treatment. Rumen concentration ofα-amino compounds was not affected by tannin extract but was higher when canola meal was the protein source. The duodenal flow of OM, total N,α-amino N and non-ammonia non-microbial N increased with tannin extract inclusion, whereas the duodenal flow of microbial N was not affected by treatment. For both protein sources, the amount of most individual amino acids flowing to the duodenum increased due to tannin extract addition. In conclusion, the dietary inclusion of 15 g/kg DM of tannin extract fromA. mearnsiiimproved the amino acid supply independently of whether the protein source was canola meal or soybean meal, without affecting the amino acid profile, to steers fed maize silage plus concentrate, with a minor but significant impact on OM digestibility.