Complementary responses between feather meal and poultry by-product meal with or without ruminally protected methionine and lysine in growing calves

We evaluated feather meal (FTH) and poultry by-product meal (PBM) as complementary protein sources for growing calves. In a replicated 84-d growth trial, individually fed steer calves (n = 120; 252 +/- 24 kg) were supplemented with urea or with graded levels of soybean meal (SBM), FTH, PBM, or 2/3 FTH:1/3 PBM (CP basis). Protein efficiency, calculated as gain above the urea control vs natural protein intake using the slope-ratio technique, was greater for FTH than for SBM, PBM, and 2/3 FTH:1/3 PBM (P < .10). Addition of ruminally protected methionine and lysine did not affect protein efficiency (P > .30) for FTH, PBM, or 2/3 FTH:1/3 PBM. Even though true protein digestibility in the gastrointestinal tract in a trial with lambs was similar (P > .15) for FTH (83.1%) and PBM (91.2%), escape protein was greater for FTH (66.8%) than for PBM (43.6%). Analyses were conducted to estimate intestinal flow of amino acids relative to requirements for live animal gain, and no obvious amino acid deficiencies were present. The lack of a response in protein efficiency to ruminally protected methionine and lysine suggests that FTH and PBM are adequate in these amino acids. Although FTH and PBM are excellent sources of metabolizable protein, there was no complementary response in protein efficiency between them.     

Supplemental methionine and time of supplementation effects on ruminal fermentation, digesta kinetics, and in situ dry matter and neutral detergent fiber disappearance in cattle

Two experiments were conducted to study the effects of methionine supplementation on ruminal fermentation and digesta kinetics. In Exp. 1, nine ruminally cannulated beef heifers (average initial BW = 527 kg) in a crossover design were fed low-quality grass hay and cottonseed meal with or without 11.4 g of supplemental methionine (polysaccharide-coated). Particulate and fluid kinetics, rate of DM and NDF disappearance, ruminal VFA and NH3 N concentrations, and pH were not altered (P > .10) by supplemental methionine; however, ruminal purine concentration was greater (P < .05) in methionine-supplemented heifers than in unsupplemented heifers. In Exp. 2, 12 ruminally cannulated Holstein steers (average initial BW = 622 kg) grazing a fescue pasture were allotted to one of three groups: no supplemental methionine (CON) or 11.4 g of supplemental methionine fed at 0700 (AM) or at 1200 (PM). Forage intake, particulate kinetics, ruminal fluid kinetics, pH, VFA, and NH3 N concentrations were not altered (P > .10) by supplemental methionine or supplementation time. In situ rate of DM and NDF disappearance was greater (P < .05) in supplemented steers than in CON steers; AM steers exhibited faster (P < .05) rates than PM steers. Overall, methionine supplementation of low-quality forage increased ruminal purine concentration but did not alter in situ fermentation or digesta passage, whereas supplementation at 0700, but not at 1200, of steers grazing fescue forage increased rate of NDF fermentation.     

Supplementation of milk replacers containing soy protein with threonine, methionine, and lysine in the diets of calves

An attempt was made to improve the protein quality supplied in milk replacers containing soy protein by supplementing Thr, Met, and Lys to the milk replacers fed to calves. Six Holstein x indigenous male calves were fitted with single cannulas at the end of the ileum. Calves were fed milk replacers containing skim milk (86%) and whey (14%) proteins or skim (43%), whey (14%), and soy (43%) proteins either with or without amino acid (AA) supplementation according to a double 3 x 3 Latin square design. Average daily gain, N retention, and ileal digestibilities of dry matter, N, and AA were significantly higher for calves fed the milk replacer containing skim milk protein than for calves fed the milk replacer containing soy protein. Average daily gain, N retention, and ileal digestibilities of dry matter, N, and AA were significantly higher for calves fed the milk replacer containing soy protein plus AA supplementation than for calves fed the milk replacer containing the soy protein without AA supplementation. Therefore, supplementation of a milk replacer containing the soy protein without AA supplementation. Therefore, supplementation of a milk replacer containing soy protein with limiting AA that correspond to the AA found in milk protein can considerably improve the protein quality of that milk replacer for the preruminant calf.     

Threonine and methionine are limiting amino acids for protein synthesis in patients with AIDS

This study was conducted to identify the most rate-limiting amino acids for whole-body protein synthesis in acquired immunodeficiency syndrome (AIDS) patients. We postulated that an essential amino acid that would be rate limiting in AIDS should have a low basal plasma concentration and should remain at a low level during amino acid infusion. Seven male AIDS patients (median age 37 y, CD4 cell count: 76 mm-3) without any clinically active opportunistic infection during the month before the experiment were infused intravenously with a complete amino acid-glucose mixture for 2.5 h. Eight healthy volunteers were used as controls. Before the infusion, the concentrations of most free essential amino acids (methionine, threonine, histidine, isoleucine, leucine and tryptophan) were significantly lower (P < 0.05) in AIDS patients than in controls. Most plasma free essential amino acids increased significantly during infusion. However, the absolute increase above basal levels for threonine, valine, lysine, (P < 0.05) and methionine (P < 0.073) was smaller in AIDS patients than in control subjects. Thus, threonine and possibly methionine may be rate limiting for whole-body protein synthesis in AIDS patients, suggesting that there are selective amino acid requirements in patients with AIDS.     

Genetic and phenotypic (co)variances for production traits of intact male populations of purebred and composite beef cattle

Least squares means, genetic (sigma g) and phenotypic (sigma p) standard deviations, and phenotypic coefficients of variation (CV) were estimated for growth traits of intact males from 12 breed groups combined, for nine purebreds combined, and for the F1, F2, F3, and F4 generations of three composite populations to which the nine purebreds contributed. Heritabilities (h2) and genetic (rg) and phenotypic (rp) correlations were estimated for growth traits, calving difficulty of calves with dams of different ages, and gestation length. Coefficients of variation and sigma g generally were similar for composites and contributing purebreds. Generally, estimates of h2 were similar for all breed groups combined, contributing purebreds combined, and composites combined. Estimates of h2 for calving difficulty were higher for calves with 2-yr-old dams than for calves with dams > or = 3 yr old and were sufficiently high (.27 and .31) to be a useful selection criterion for reducing calving difficulty. Mean h2 pooled within all breed groups ranged from .35 for 200-d weight and 368-d weight to .48 for 368-d height. Estimates of h2 for subjective scores of anatomical traits were only slightly lower than those for growth and size traits. The h2 of scrotal circumference (.43) was similar to those for growth and size traits. Genetic correlations between birth weight and calving difficulty were similar for 1) calves with dams of all ages, 2) calves with 2-yr-old dams, and 3) calves with dams > or = 3 yr old.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cumulative selection and genetic change for weaning or yearling weight or for yearling weight plus muscle score in Hereford cattle

Selection in three lines of Hereford cattle for 1) weaning weight (WWL), 2) yearling weight (YWL), and 3) an index of yearling weight and muscle score (IXL) was studied. Remnant foundation cows and semen from seven foundation sires were used to establish an unselected control line for the last 11 yr of the experiment. Performance data collected over a 23-yr period on birth weight (BWT), weaning weight (WWT), postweaning gain (PWG), yearling weight (YWT), muscle score (MSC), and an index (IDX) giving equal weight to standard deviations of yearling weight and muscle score were analyzed. Generation interval of midparents was about 4.16 yr in each selected line. Sire and dam selection differentials, in standard deviation units per generation, for primary criteria were, respectively, 1.59 and .33 for WWT in WWL, 1.75 and .25 for YWT in YWL, and 1.42 and .25 for IDX in IXL. Components of direct and maternal genetic variances, direct-maternal covariance, and dam permanent environmental variance were estimated by REML. The average annual response of males and females in actual units for each trait in WWL, YWL, and IXL was, respectively, BWT, .22, .24, and .27 kg; WWT, .98, .63, and 1.26 kg; YWT, 2.43, 2.64, and 3.44 kg; and MSC, .053, .009, and .104 scores. Average selection responses in BWT, WWT, YWT, MSC, and IDX per unit of primary criteria in each selection line (all in standard deviation units) were .22, .20, .31, .10, and .24 for WWT in WWL; .23, .12, .32, .04, and .21 for YWT in YWL; and .27, .22, .40, .20, and .36 for IDX in IXL. Responses in bold type are realized heritability and others are correlated responses. Realized genetic correlations were .78 for WWT and YWT, .87 for WWT and IDX, and .86 for YWT and IDX. Responses for all traits in IXL were greater than in other selected lines.     

Lipopolysaccharide-induced reductions in food intake do not decrease the efficiency of lysine and threonine utilization for protein accretion in chickens

Exposure of animals to infectious agents induces immune responses that result in reductions in food consumption and weight gain. The effect of these changes on amino acid requirements and utilization remains unclear. Three assays were conducted with young chicks with Escherichia coli lipopolysaccharide (LPS) used to stimulate the immune system. An initial study was conducted to evaluate the effects of LPS on animal performance. In a daily or alternate day injection regimen for 9 d, chicks were given intraperitoneal injections of sterile saline containing 0, 100 or 400 microgram LPS. Administration of 100 or 400 microgram LPS daily, or every other day, decreased both weight gain and food consumption. In two subsequent growth assays, chicks were fed graded levels of lysine or threonine and injected with either 0 or 400 microgram LPS every other day to evaluate the effect of LPS administration on the efficiency of amino acid utilization. At the three lowest amino acid doses, whole-body protein accretion was a linear function of supplemental lysine or threonine intake, and slopes of the accretion curves were not altered by LPS administration. The dietary lysine concentration required to maximize protein accretion was unaffected by LPS, but the absolute lysine intake required to maximize chick performance was lower in LPS-injected chicks than in saline-injected chicks. These results show that LPS administration reduces weight gain, food intake, efficiency of food utilization and the absolute quantity of lysine required to maximize these criteria. However, LPS administration does not affect the efficiency of amino acid utilization, nor does it affect the concentration of dietary lysine required to maximize performance.     

The feeding value of dry-rolled and steam-flaked corn in finishing diets for feedlot cattle: influence of protein supplementation

We used 80 medium-framed yearling crossbred heifers (357 kg) in a 110-d trial to evaluate the influence of dietary protein level (11 vs 14%) on the feeding value of dry-rolled (DRC) and steam-flaked corn (SFC). All diets contained 1% urea; cottonseed meal (CSM) was the source of supplemental undegradable intake protein (UIP). Steam flaking corn reduced DMI (9%, P < .10) and increased (P < .01) feed efficiency (14%), dietary NEm (13%), and NEg (15%). Steam flaking increased the NEm by 17% and NEg by 19%. Supplemental CSM decreased (P < .10) feed efficiency (7%) and dietary NEm (4%) and NEg (6%). There were no treatment effects (P > .10) on carcass characteristics. Steam flaking corn increased (P < .05) fecal pH and reduced (P < .01) fecal starch. Supplemental CSM increased (P < .01) fecal pH and reduced (P < .01) fecal starch. Four Holstein steers (413 kg) were used in a 4 x 4 Latin square experiment to evaluate treatment effects on digestive function. Steam flaking corn increased (P < .05) flow of nonammonia N (11%, P < .05) and microbial N (15%, P < .01) to the duodenum. Supplemental CSM increased the flow of microbial N (6%, P < .01), feed N (21%, P < .10), and nonammonia N (12%, P < .05) to the duodenum. The UIP value of CSM was 28% for the DRC diet and 52% for the SFC diet. Steam flaking corn increased (P < .01) ruminal starch digestion (26%) and total tract digestibility of OM (17%), N (15%), starch (19%), and GE (17%). Steam flaking increased the DE value of corn by 21%. Supplemental CSM did not influence (P > .10) postruminal or total tract starch digestion. Supplemental CSM decreased (7%, P < .10) the DE value of the diet. We conclude that increasing the postruminal protein supply of a corn-based finishing diet beyond that provided by urea supplementation, alone, will not enhance starch digestion or the energy value of the diet.     

Cdc53 is a scaffold protein for multiple Cdc34/Skp1/F-box proteincomplexes that regulate cell division and methionine biosynthesis in yeast

In budding yeast, ubiquitination of the cyclin-dependent kinase (Cdk) inhibitor Sic1 is catalyzed by the E2 ubiquitin conjugating enzyme Cdc34 in conjunction with an E3 ubiquitin ligase complex composed of Skp1, Cdc53 and the F-box protein, Cdc4 (the SCFCdc4 complex). Skp1 binds a motif called the F-box and in turn F-box proteins appear to recruit specific substrates for ubiquitination. We find that Skp1 interacts with Cdc53 in vivo, and that Skp1 bridges Cdc53 to three different F-box proteins, Cdc4, Met30, and Grr1. Cdc53 contains independent binding sites for Cdc34 and Skp1 suggesting it functions as a scaffold protein within an E2/E3 core complex. F-box proteins show remarkable functional specificity in vivo: Cdc4 is specific for degradation of Sic1, Grr1 is specific for degradation of the G1 cyclin Cln2, and Met30 is specific for repression of methionine biosynthesis genes. In contrast, the Cdc34-Cdc53-Skp1 E2/E3 core complex is required for all three functions. Combinatorial control of SCF complexes may provide a basis for the regulation of diverse cellular processes.     

Docking of nitrogenase iron- and molybdenum-iron proteins for electron transfer and MgATP hydrolysis: the role of arginine 140 and lysine 143 of the Azotobacter vinelandii iron protein

Docking of the nitrogenase component proteins, the iron protein (FeP) and the molybdenum-iron protein (MoFeP), is required for MgATP hydrolysis, electron transfer between the component proteins, and substrate reductions catalyzed by nitrogenase. The present work examines the function of 3 charged amino acids, Arg 140, Glu 141, and Lys 143, of the Azotobacter vinelandii FeP in nitrogenase component protein docking. The function of these amino acids was probed by changing each to the neutral amino acid glutamine using site-directed mutagenesis. The altered FePs were expressed in A. vinelandii in place of the wild-type FeP. Changing Glu 141 to Gln (E141Q) had no adverse effects on the function of nitrogenase in whole cells, indicating that this charged residue is not essential to nitrogenase function. In contrast, changing Arg 140 or Lys 143 to Gln (R140Q and K143Q) resulted in a significant decrease in nitrogenase activity, suggesting that these charged amino acid residues play an important role in some function of the FeP. The function of each amino acid was deduced by analysis of the properties of the purified R140Q and K143Q FePs. Both altered proteins were found to support reduced substrate reduction rates when coupled to wild-type MoFeP. Detailed analysis revealed that changing these residues to Gln resulted in a dramatic reduction in the affinity of the altered FeP for binding to the MoFeP. This was deduced in FeP titration, NaCl inhibition, and MoFeP protection from Fe2+ chelation experiments.(ABSTRACT TRUNCATED AT 250 WORDS)