Showing papers by "Tim A. McAllister published in 2000"
TL;DR: Dietary CT may provide a means to beneficially manipulate protein digestion and/or prevent pasture bloat in ruminants, and alter digestive processes as compared with diets free of CT.
Abstract: Condensed tannins (CT) are polyphenolic secondary plant products that are widespread in the plant kingdom. By definition, CT bind to protein and are regarded as "antinutritional" compounds which re...
277 citations
TL;DR: The effects of steroidal saponins isolated from Yucca schidigera extract on ruminal bacteria and fungi were investigated in pure culture studies and revealed that SAP altered the cell walls of the SAP‐inhibited non‐cellulolytic bacteria.
Abstract: The effects of steroidal saponins (SAP) isolated from Yucca schidigera extract on ruminal bacteria and fungi were investigated in pure culture studies. Prevotella bryantii, Ruminobacter amylophilus, Selenomonas ruminantium and Streptococcus bovis were cultured through ten 24-h transfers in ruminal fluid medium containing 0 or 25 µg SAP ml−1 (measured as smilagenin equivalents). The four strains, each non-exposed or pre-exposed to SAP, were then inoculated into medium containing 0 or 250 µg smilagenin equivalents ml−1 and 24-h growth curves were determined. The cellulolytic ruminal bacteria Ruminococcus flavefaciens, Fibrobacter succinogenes and Rc. albus were cultured for 72 h on Whatman no. 1 filter paper in medium containing 0, 9, 90 or 180 µg SAP ml−1 for the determination of filter paper digestion and endoglucanase activity. The ruminal bacteria differed in their responses to SAP. Steroidal saponins in the medium reduced the growth of Strep. bovis (P 0·05) between pre-exposed and non-exposed cultures and the concentrations of total SAP and soluble (deglycosylated) SAP in the liquid fraction were unchanged (P > 0·05) over time. Steroidal saponins inhibited the digestion of filter paper by all three cellulolytic bacteria, but F. succinogenes was less (P < 0·05) sensitive to SAP and more (P < 0·05) effective at deglycosylating SAP than were Rc. flavefaciens or Rc. albus. Transmission electron microscopy revealed that SAP altered the cell walls of the SAP-inhibited non-cellulolytic bacteria. The ruminal fungi, Neocallimastix frontalis and Piromyces rhizinflata, were cultured on filter paper in medium containing 0, 0·45, 2·25 or 4·5 µg SAP ml−1. Filter paper digestion by both fungi was completely inhibited by 2·25 µg SAP ml−1. Steroidal saponins from Y. schidigera inhibit cellulolytic ruminal bacteria and fungi, but their effects on amylolytic bacteria are species dependent and similar to the effects of ionophores. As such, SAP may be useful in nutritional applications targeting starch-digesting ruminal micro-organisms.
186 citations
TL;DR: The synergistic effect between ruminal and exogenous enzymes increases the hydrolytic potential within the rumen environment and is likely a significant mechanism by which enzyme additives improve feed digestion in ruminants.
180 citations
TL;DR: The biological activity of YE was shown to be attributable to its SAP and to be diet-dependent and the effects of SAP on digestive microbes were less pronounced with barley grain digestion than with alfalfa.
Abstract: In a first experiment, ground alfalfa hay and rolled barley grain were incubated in buffered ruminal fluid with and without Yucca schidigera extract (YE, 0 or 10 mg ml−1). Gas and total VFA production from barley grain were increased (P < 0.05) by YE during the first 10 h of incubation; from alfalfa hay, these were reduced (P < 0.001) throughout the 24 h. Yucca extract reduced (P < 0.001) acetate/propionate ratios and ammonia concentrations, irrespective of substrate. In a second experiment, ground barley grain was incubated in a buffered suspension of mixed ruminal microbes obtained by low-speed centrifugation of ruminal fluid. Steroidal saponins (SAP) isolated from YE were included at 0, 15, 75 or 225 µg ml−1. Microbial incorporation of 15N was increased (P < 0.05) by 15 µg SAP ml−1 but decreased (P < 0.05) by 225 µg SAP ml−1. Gas and VFA production peaked with 75 µg SAP ml−1 and were elevated (P < 0.05) relative to control in the presence of 75 µg SAP ml−1. Microbial protein synthesis was increased (P < 0.05) by SAP at 15 µg ml−1 and reduced (P < 0.05) by the higher concentrations. Acetate/propionate ratios were linearly reduced by SAP from 8 to 24 h incubation (P < 0.01). The effects of SAP on digestive microbes were less pronounced (P < 0.05) with barley grain digestion than with alfalfa. A YE × diet interaction was recorded. The biological activity of YE was shown to be attributable to its SAP and to be diet-dependent.
© 2000 Society of Chemical Industry. Contributions of Y Wang, T A McAllister, L J Yanke and Z Xu © Minister of Public Works and Government Services Canada 2000
147 citations
TL;DR: Fibrolytic enzymes enhance fiber degradation by altering the structure of alfalfa hay by interacting with xylanases and esterases, and are implicated as activities responsible for the initiation of this stimulatory effect.
137 citations
TL;DR: The effects of supplying increasing ruminal doses of exogenous polysaccharide-degrading enzymes (EPDE) on rumen fermentation and nutrient digestion were studied using eight ruminally cannulated heifers and did not affect urinary excretion of allantoin and uric acid, or concentrations of glucose and urea in blood.
Abstract: The effects of supplying increasing ruminal doses of exogenous polysaccharide-degrading enzymes (EPDE) on rumen fermentation and nutrient digestion were studied using eight ruminally cannulated heifers, four of which were also duodenally cannulated, in a replicated Latin square The heifers were fed a diet of 855% rolled barley grain and 14% barley silage (DM basis), and once daily they were given intraruminal doses of 0 (Control), 100, 200, or 400 g of a preparation containing polysaccharide-degrading enzymes Enzyme treatment decreased ruminal pH (linear, P 05) ruminal fluid amylase activity Elevated levels of fibrolytic activities in the rumen resulted in increased (quadratic, P 05) urinary excretion of allantoin and uric acid, or concentrations of glucose and urea in blood
120 citations
TL;DR: Development of grazing-tolerant alfalfa varieties is solving some of the problems associated with lack of persistence of al falfa in mixed stands; however, they are not bloat-safe.
Abstract: Alfalfa has been recognized for its superior yield and quality in seeded pastures. However, when grazing immature alfalfa there is a risk of animal losses due to frothy bloat in some ruminant livestock. Inclusion of at least 50% grass in the pasture mixture is commonly recommended to reduce the risk of bloat. Two decades of plant breeding have resulted in the release of AC Grazeland, an alfalfa cultivar that reduces the incidence of bloat. Other bloat control agents such as pluronic detergents and ionophores can also be of value. Development of grazing-tolerant alfalfa varieties is solving some of the problems associated with lack of persistence of alfalfa in mixed stands; however, they are not bloat-safe. Animal productivity commonly increases when alfalfa is included in pasture mixtures. Improvements in cattle rate of gain are observed when alfalfa contributes as little as 35% to the sward. Grazing management is the principal method for controlling pasture yield and quality as well as animal performance...
85 citations
TL;DR: These nonionic surfactants were effective for enhancing rumen microbial protease and cellulase activities and further study is warranted to determine their potential for improving ruminant feeding.
63 citations
TL;DR: The effects of Tween 80 on the stability and substrate binding capacity of two commercially available enzyme preparations were studied in vitro and increased protein binding both to filter paper and to cotton fibres.
Abstract: The effects of Tween 80 on the stability and substrate binding capacity of two commercially available enzyme preparations were studied in vitro. After 1 wk of incubation, endoglucanase activity was higher (P < 0.05) in the presence of 0.02 or 0.2% (vol vol−1) Tween 80 than without this surfactant. Tween 80 increased (P < 0.05) protein binding both to filter paper and to cotton fibres. Digestibility and feedlot experiments were conducted with Dorset and Romanov × Suffolk lambs, respectively, given forage- and concentrate-based diets. The diets were untreated or sprayed with the enzyme preparations, Tween 80 or a mixture of both. With the concentrate diet, treatment with enzymes + surfactant reduced (P < 0.05) intake of feed dry matter and N, acid detergent fibre digestibility, N digestion and microbial N production, relative to treatment with either additive alone. Treating the concentrate diet with enzymes increased (P < 0.05) N retention (g d−1) by the lambs, as compared to untreated diet. With the forag...
57 citations
TL;DR: The studies that led to the development of a bloat-reduced alfalfa began in 1970 and a 4-h nylon-bag rumen digestion technique was developed, which was used to assess the initial rate of digestion (IRD) of fresh leaf material in large numbers of al falfa genotypes.
Abstract: The studies that led to the development of a bloat-reduced alfalfa began in 1970. Initial work focused on the causes of bloat, the characteristics of bloat-safe and bloat-causing legumes and the development of screening methodologies. The characteristics that were examined as causal factors of bloat in legume species included soluble proteins, saponins, absence of condensed tannins, and rapid breakdown of cells in the rumen. The factor or combination of factors responsible for causing bloat in animals grazing legumes have not been clearly identified; however, of the above, rapid cell breakdown was considered to be the most promising line of research to pursue in selecting a bloat-safe legume. A 4-h nylon-bag rumen digestion technique was developed, which was used to assess the initial rate of digestion (IRD) of fresh leaf material in large numbers of alfalfa genotypes. Using this technique on a population of four alfalfa cultivars, four cycles of recurrent selection for low initial rate of digestion (LIRD...
TL;DR: It is demonstrated that fenbendazole is an effective treatment for giardiosis, resulting in a clinical benefit and reducing the number of infective cysts shed by calves.
TL;DR: A review of the results of grazing and feeding trials using alfalfas with low rates of digestion (LIRD) shows that this new strain reduces the incidence and severity of frothy bloat on pasture.
Abstract: and Cheng, K.-J. 2000. Bloat in cattle grazing alfalfa cultivars selected for a low initial rate of digestion: A review. Can. J. Plant. Sci. 80: 493‐502. The occurrence of frothy bloat limits the practice of alfalfa grazing in spite of the availability of strains bred specifically for pasture. Bloat is a chronic condition, endemic to cattle. Prophylactics and management techniques are ava ilable to reduce its incidence but they are expensive, difficult to administer, conflict with traditional grazing management regi mens and do not eliminate bloat in all circumstances. A program to breed and evaluate a bloat-reduced strain of alfalfa was initiate d in 1980 to overcome some of these limitations. A review of the results of grazing and feeding trials using alfalfas with low initi al rates of digestion (LIRD) shows that this new strain reduces the incidence and severity of frothy bloat on pasture. Their effec tiveness in controlling bloat was related to feeding or grazing management practices, the maturity of the plants and the season of use. Graziers may reduce the risk of occasional livestock losses from bloat by using LIRD cultivars, like AC Grazeland, or managing species/cultivar mixtures in ways that reduce the initial rate of digestion. Other bloat preventive strategies, including coseeding with bloat-free legumes and using bloat-controlling prophylactics in combination with a LIRD alfalfa, are being investigated.
TL;DR: In two pastures, two multiplex radio frequency (RF) mineral feeders equipped with load cells were used to monitor feeder attendance and individual intake of mineral by 33 and 36 cow-calf pairs individually identified by RF transponders.
Abstract: In two pastures, two multiplex radio frequency (RF) mineral feeders (GrowSafe Systems Ltd.) equipped with load cells were used to monitor feeder attendance and individual intake of mineral by 33 and 36 cow-calf pairs individually identified by RF transponders. A visit was defined as a return to the feeder after a 5-min absence. In exp. 1, attendance of cows and calves at the feeder and intake of mineral were monitored over 13 d. Sodium chloride was included in the mineral at 9.8% (low salt, LS) on days 1 to 6, and at 22.5% (high salt, HS) on days 7 to 13. Percentages of cows and calves that visited the feeder were similar between LS (60.9% and 21.7% respectively) and HS (62.3% and 24.6%). Number of visits (P > 0.05) and daily mineral intake (P < 0.1) were reduced in cows fed HS as compared with LS. Cows had more visits (P < 0.001) and consumed more mineral (P < 0.001) than did calves. In exp. 2, HS as is (control, C) or formulated to contain 0.468% fenbendazole (FB) was provided for 6 d to 36 and 32 cow-c...
TL;DR: Anaerobic chytrid strains (representing four genera and seven species based on morphological characters), obtained from a variety of hosts, were analysed for variability within the 5' terminal segment of the ribosomal large subunit (LSU) gene, first internal transcribed spacer (ITS1), and the intergenic spacers (IGS) of the ribsomal repeat unit.
Abstract: Anaerobic chytrid strains (representing four genera and seven species based on morphological characters), obtained from a variety of hosts, were analysed for variability within the 5' terminal segment of the ribosomal large subunit (LSU) gene, first internal transcribed spacer (ITS1), and the intergenic spacers (IGS) of the ribosomal repeat unit. In the analyses of the ribosomal LSU gene, strains of Neocallimastix, Orpinomyces, and Anaeromyces clustered into distinct groups, but Piromyces strains did not. Although the size of polymerase chain reaction products for the ITS1 region varied among strains, restriction fragment length polymorphism analysis was not useful in distinguishing between the strains. In the analyses of restriction fragment profiles of the IGS, strains of Orpinomyces and Anaeromyces clustered into distinct groupings that corresponded with morphological characters. In contrast, Neocallimastix strains clustered into two distinct groups. Considerable variability was observed in the IGS for...
TL;DR: A traceback system for individual identification of Canadian beef cattle is proposed in this paper, where simple Kurl-lockTM ear tags with a unique number are used to trace individuals back to their herd of origin.
Abstract: Individual identification of beef cattle is not new to the Canadian beef industry, as traceback systems played a pivotal role in the eradication of bovine tuberculosis in the 1940s and 1950s and brucellosis in the 1970s and 1980s. Recent concerns over animal health (e.g., bovine spongiform encephaolopathy), export markets, product consistency, meat quality (e.g., tenderness, marbling) and safety (e.g., Escherichia. coli 0157:H7, Salmonella spp.) make reestablishment of a traceback system a logical approach to assuring consumer confidence in Canadian beef. Originally, simple Kurl-lockTM ear tags with a unique number were used to trace individuals back to their herd of origin. Although useful for addressing disease concerns, this system did not lend itself to compiling additional information (e.g., growth performance, animal health, breeding programs, carcass quality) for use in management or marketing decisions. More sophisticated electronic identification systems can readily interface with computers and m...
TL;DR: It is indicated that LTB produce an array of cellulolytic and xylanolytic enzymes, and that some of these enzymes possess low-temperature optima which may facilitate degradation of plant fibre under low-Temperature conditions.
Abstract: Three of four isolates, representing phylogenetically distinct groupings of low-temperature basidiomycetes (LTB), were capable of utilizing wheat straw, and to a lesser extent conifer wood at 15°C. A cottony snow mould LTB (LRS 013) and a fruit rot LTB (LRS 241) grown on straw significantly degraded filter paper, carboxymethylcellulose (CMC), p-nitrophenyl β-glucopyranoside (i.e., β-glucosidases), and xylan. Enzymes produced by Coprinus psychromorbidus (LRS 067) were limited to xylanases from straw and wood and β-glucosidases from wood. A sclerotia-forming LTB (LRS 131) exhibited poor growth on both substrates, and did not produce detectable quantities of extracellular enzymes. None of the LTB isolates tested degraded avicel. The temperature optima of CMCases and xylanases in the filtrates from the straw medium ranged from 25°C to 55°C, and with the exception of LRS 067, sig- nificant activity was observed at 5°C. Two cellulases (25 and 31 kDa) and two xylanases (24 and 34 kDa) were ob- served on zymograms for LRS 013 and 241. Reduction of enzymes with 2-mercaptoethanol adversely affected their activity on zymograms, and an additional cellulase band was observed for non-reduced samples. This study indicates that LTB produce an array of cellulolytic and xylanolytic enzymes, and that some of these enzymes possess low-temperature optima which may facilitate degradation of plant fibre under low-temperature conditions.
TL;DR: Trainers did not improve calf health, time spent at the feed bunk, or performance of newly weaned calves, and frequency and duration of bunk visits by the calves did not affect.
Abstract: Experiments were conducted to investigate the effects of the presence of a trainer cow on behavior, performance, health, and feeding patterns of newly weaned beef calves. In Exp. 1,252 weaned calves (270+/-18 kg) were allocated to 22 pens (11 to 15 calves per pen). A trainer cow was randomly assigned to each of 11 pens. Calves were weighed prior to feeding on d 0, 3, 7, 14, 21, and 28. Rectal temperatures were taken on each of these days (except d 28) and blood samples were collected on d 0, 3, and 7 and subsequently analyzed for serum haptoglobin and leukotoxin antibody titers. Instantaneous scan observations of calf behavior were made at 10-min intervals between 0730 and 1730 on d 1, 2, 4, 5, and 6. A similar protocol was used in Exp. 2, in which 297 calves (258+/-17 kg) were allocated to 24 pens. Blood analyses included haptoglobin, white blood cell counts (WBC), and neutrophil:lymphocyte (NL) ratios. In Exp. 3, the above protocol was followed and patterns of feed bunk attendance of individual calves were also monitored using radio frequency identification by passive transponder ear tags. Trainer cows did not influence (P > .10) calf rectal temperatures, requirements for antibiotic therapy, WBC, NL ratios, or leukotoxin antibody titers. Pooled across treatments, NL ratios were lower (P .10) overall (d 0 to 28). Trainer cows did not affect (P > .05) frequency or duration of bunk visits by the calves. Averaged across treatments, frequency and duration of bunk visits increased (P < .001) from 9.6 visits/d and 56.7 min/d between d 0 and 3 to 12.3 visits/d and 108.9 min/d between d 15 and 21. The number of calves observed eating during scan sampling observations also increased from 16.4% on d 1 to 25% on d 4 (P < .10) and 29% on d 5 and 6 (P < .05). More (P < .05) calves were observed lying on d 1 (41.7%) and d 2 (45.3%) than on d 4 (37.5%), d 5 (34.8%), or d 6 (36.2%). With a trainer cow present, fewer (36.7% vs 41.5%; P < .001) calves were observed lying and more (11.7% vs 10.2%; P = .08) were observed walking than when no cow was present. Trainer cows did not improve calf health, time spent at the feed bunk, or performance of newly weaned calves.
Journal Article•
TL;DR: This study is the first to implicate 3MI metabolites as having a role in feedyard AIP, and plasma concentrations of 3-methylindole (3MI) metabolites were higher in heifers afflicted with AIP than in the control animals, and concentrations of3MI mercapturates in the urine were lower in affected heifes.
Abstract: Field data were collected over 2 consecutive years to characterize acute interstitial pneumonia (AIP) in feedyard cattle. Thirty-eight cattle with clinical symptoms of AIP were examined following emergency slaughter; 31 (all heifers) were confirmed to have AIP on the basis of gross and histological lung pathology. The 7 without AIP, plus 17 asymptomatic penmates, were used as contemporary controls. Plasma concentrations of 3-methylindole (3MI) metabolites were higher (P 0.05) between the 2 groups, and 3MI was not detected in ruminal fluid from either group. Total ruminal bacterial numbers and populations of lactobacilli and protozoa were similar (P > 0.05) between the AIP-positive and unafflicted groups, but fewer (P < 0.05) cellulolytic bacteria were present in the positive group. Bovine respiratory syncytial virus antigen was not found in lung tissue from any of the heifers confirmed to have AIP. To our knowledge, this study is the first to implicate 3MI metabolites as having a role in feedyard AIP. Further research is required to determine the factors responsible for the elevation in 3MI adducts in plasma and urine of feedyard cattle afflicted with AIP.
TL;DR: Ruminal carboxymethylcellulase, xylanase and amylase activities, numbers of protozoa, and outflow rates of the liquid and solid phases of ruminal contents did not differ among treatments, and pH, concentrations of ammonia, total free amino acids, reducing sugars and total volatile fatty acids, and fluid phase viscosity were unaffected.
Abstract: Ten Jersey steers (484 ± 55 kg) were fed a basal diet of 70% rolled barley grain and 30% alfalfa silage [dry matter (DM) basis] with or without additives, in a replicated 5 × 5 Latin square experiment. Treatments (additives per kilogram dietary DM) were: C, no additives (control); T, Tween 80 (2 g kg−1); SH, salinomycin (13 mg kg−1); TSM, Tween 80 (2 g kg−1) plus salinomycin (6.5 mg kg−1); and TSL, Tween 80 (2 g kg−1) plus salinomycin (3.25 mg kg−1). Ruminal pH, concentrations of ammonia, total free amino acids, reducing sugars and total volatile fatty acids (VFA), and fluid phase viscosity were unaffected (P > 0.05) by treatment. Ruminal carboxymethylcellulase, xylanase and amylase activities, numbers of protozoa, and outflow rates of the liquid and solid phases of ruminal contents did not differ (P > 0.05) among treatments. Ruminal lactic acid bacteria populations tended (P 0.05) by T, TSL and TSM. Partitioning of ruminal dige...
TL;DR: Commercial coarse canola screenings were substituted for barley grain, and the resulting experimental diets were evaluated in feedlot lambs, while the 0, 45 and 95% CS diets were evaluation in a digestibility study using Romanov × Suffolk lambs.
Abstract: Commercial coarse canola screenings (CS) were substituted for barley grain, and the resulting experimental diets (0, 20, 45, 70 and 95% CS, as-fed) were evaluated in feedlot lambs, while the 0, 45 and 95% CS diets were evaluated in a digestibility study using Romanov × Suffolk lambs. The CS comprised 60% canola (as whole, broken and immature seeds), 25% weed seeds and 15% chaff/dust. The control diet (0% CS) contained 75% barley and 20% alfalfa (as a protein/fibre source). Dietary crude protein (CP) increased with inclusion of CS and was lowest for control and 20% CS diets (13%) and highest for the 95% CS diet (14.4%). Digestibilities of dry matter (DM), organic matter (OM), neutral detergent fibre (NDF) and acid detergent fibre (ADF) were reduced (P < 0.05) in the 95% diet as compared with the control diet. Nitrogen retention by lambs was three times higher in the control group than in the 95% CS group (P < 0.001). Growth and feed conversion efficiency in feedlot lambs were linearly reduced (P < 0.001) w...
TL;DR: The data indicate that long-term cold acclimation in skeletal muscle is associated with the establishment of a new homeostasis in protein turnover with decreased protein mass and normal fractional rates of protein turnover.
Abstract: The effect of long-term cold exposure on skeletal and cardiac muscle protein turnover was investigated in young growing animals. Two groups of 36 male 28-day-old rats were maintained at either 5°C ...
TL;DR: Two experiments were conducted to determine the feeding value of canola screenings in combination with barley grain for beef steers and the effects of dietary treatment on ruminal fermentation parameters were determined.
Abstract: Two experiments were conducted to determine the feeding value of canola screenings in combination with barley grain for beef steers. Four dietary treatments were used. These included canola screeni...
TL;DR: Chronic exposure to hot environments was associated with lower skeletal and cardiac muscle mass and protein turnover; lower protein mass in this tissue was due to decreased k(syn); this is consistent with lower plasma T3 concentrations.
Abstract: A study was undertaken to determine the long-term effects of a hot environment on protein turnover in skeletal and cardiac muscles of young homeothermic animals. Three groups of 36 male 28 day old rats were housed at 35°C (hot group), 25°C (control group), or 25°C but pair-fed to the intake of the hot group (pair-fed group). Rates of protein synthesis and degradation were measured in vivo on days 5, 10, 15, and 20. By day 20, soleus and gastrocnemius (skeletal muscle) protein masses were 7 and 14% lower in the hot group and 31 and 21% lower in the pair-fed group compared with the control group (P < 0.05). The fractional rate of protein synthesis (ksyn) was on average 11% lower (P < 0.05) in the hot group compared with control rats and was not different from pair-fed rats. The fractional rate of skeletal muscle protein degradation (kdeg) in hot rats was slightly lower than in control rats; kdeg was on average 18% higher (P < 0.05) in the pair-fed group compared with the hot group and this difference appear...