Showing papers by "Tim A. McAllister published in 2001"

Fermentation characteristics and ruminal ciliate protozoal populations in cattle fed medium- or high-concentrate barley-based diets

Abstract: Fermentation characteristics were measured and numbers and distribution by genera of ciliate protozoa were determined in ruminal fluid samples collected from 10 ruminally cannulated steers during the first 30 d of their being fed barley-based diets containing 62% (Medium Barley) or 95% (High Barley) barley grain (DM basis). Ruminal samples were collected at 5-d intervals over the 30-d periods beginning after adaptation (i.e., at the first full feeding of each diet). Ruminal pH and ammonia concentrations were lower (P < 0.001) with the High Barley than with the Medium Barley diet. Concentrations of total VFA and propionate and amylase activity of ruminal fluid were higher (P < 0.001) on High Barley than on Medium Barley. Total protozoal numbers in ruminal fluid were 42% lower (P < 0.05) on High Barley (470 x 10(3)/mL) than on Medium Barley (804 x 10(3)/mL). On Medium and High Barley diets, respectively, Entodinium spp. made up 89 and 91% of the ciliate protozoal populations. With the Medium Barley diet, relative proportions of Dasytricha, Ophryoscolex, Ostracodinium, Diplodinium, and Metadinium spp. in the total ciliate population were 4.5, 0.4, 0.5, 0.7, and 0.3%, respectively. When the High Barley diet was fed, these genera were not detected. In a subsequent survey, ruminal samples were collected from 200 finishing cattle at slaughter. Average protozoal population was 328 x 10(3)/mL, and Entodinium spp. constituted 97% of the total. These data demonstrate that a large population of Entodinium spp. can persist in the rumen of cattle fed high barley grain-based finishing diets.

Effects of an exogenous enzyme preparation on microbial protein synthesis, enzyme activity and attachment to feed in the Rumen Simulation Technique (Rusitec).

Abstract: The effects of an exogenous enzyme preparation, the application method and feed type on ruminal fermentation and microbial protein synthesis were investigated using the rumen simulation technique (Rusitec). Steam-rolled barley grain and chopped alfalfa hay were sprayed with water (control, C), an enzyme preparation with a predominant xylanase activity (EF), or autoclaved enzyme (AEF) 24 h prior to feeding, or the enzyme was supplied in the buffer infused into the Rusitec (EI). Microbial N incorporation was measured using (15NH4)2SO4 in the buffer. Spent feed bags were pummelled mechanically in buffer to segregate the feed particle-associated (FPA) and feed particle-bound (FPB) bacterial fractions. Enzymes applied to feed reduced neutral-detergent fibre content, and increased the concentration of reducing sugars in barley grain, but not alfalfa hay. Ruminal cellulolytic bacteria were more numerous with EF than with C. Disappearance of DM from barley grain was higher with EF than with C, but alfalfa was unaffected by EF. Treatment EF increased incorporation of 15N into FPA and FPB fractions at 24 and 48 h. In contrast, AEF reduced the 24 h values, relative to C; AEF and C were similar at 48 h. Infused enzyme (EI) did not affect 15N incorporation. Xylanase activity in effluent was increased by EF and EI, compared to C, but not by AEF. Xylanase activity in FPA was higher at 48 h than at 24 h with all treatments; it was higher with EF than C at 24 and 48 h, but was not altered by AEF or EI. Applying enzymes onto feeds before feeding was more effective than dosing directly into the artificial rumen for increasing ruminal fibrolytic activity.

Resistance of feed enzymes to proteolytic inactivation by rumen microorganisms and gastrointestinal proteases.

Abstract: Potential feed enzyme additives for ruminants were tested in vitro for their stability to ruminal microbial and gastrointestinal proteolysis. Four commercial preparations from Trichoderma longibrachiatum (A, B, C, and D) and one from an undisclosed source (E) were incubated up to 6 h with ruminal fluid taken from four lactating dairy cows before or 2 h after feeding. The stability of preparation B was also tested in the presence of pepsin at pH 3 and pancreatin at pH 7. Cellulase (EC 3.2.1.4), cellulose 1,4-beta-cellobiosidase (EC 3.2.1.91), beta-glucanase (EC 3.2.1.6), xylanase (EC 3.2.1.8), beta-glucosidase (EC 3.2.1.21), and beta-xylosidase (EC 3.2.1.37) activities were monitored throughout the incubations. Polysaccharidase activities of all enzyme preparations were remarkably stable in ruminal fluid taken after feeding. Ruminal fluid obtained before feeding inactivated the polysaccharidases in preparations B and D to a greater extent than ruminal fluid obtained after feeding. Cellulase and cellulose 1,4-beta-cellobiosidase activities were the least stable, declining (P < 0.05) by 35 and 60% for preparations B and D, respectively. Xylanase activity of preparation D decreased (P < 0.05) by up to 30% after 6 h of incubation, whereas beta-glucanase activity was not affected. The ability to degrade exogenous enzymes also differed among cows (P < 0.05). Pepsin and acid (pH 3.0) did not affect polysaccharidases in preparation B but decreased glycosidase activities by 10 to 15% (P < 0.05) after 1 h of incubation. Pancreatin, at the maximum concentration used, inactivated cellulase, cellulose 1,4-beta-cellobiosidase, and xylanase activities at a rate of 0.55, 1, and 0.45%/min, respectively. beta-Glucosidase and beta-xylosidase activities decreased by 1 and 0.75%/min, respectively. Partial proteolysis of cellulase, cellulose 1,4-beta-cellobiosidase, and xylanase by pancreatin produced a transient increase in activity. This twofold increase for cellulase and fourfold increase for cellulose 1,4-beta-cellobiosidase was directly proportional to pancreatin concentration. These results suggest that the enzyme feed additives tested were stable in the rumen of animals after feeding. Exogenous enzymes are likely to be more susceptible to the host gastrointestinal proteases in the abomasum and intestines than to ruminal proteases. However, exogenous polysaccharidases may survive for a considerable period of time in the small intestine and they probably maintain activity against target substrates in this environment.

Traceability in cattle and small ruminants in Canada.

Abstract: Traceback systems for cattle and small ruminants are of international concern after the outbreaks of bovine spongiform encephalopathy in the European Union and foot and mouth disease in the United Kingdom and South America. Implementation of a national or international identification system depends on meeting a balance between cost, reliability/durability, ease of use, data transfer speed, protection from fraud, avoidance of entry into the food chain and animal welfare issues. As of 1 January 2001, Canada has instituted a national identification programme for cattle, which will have annual operating and administrative costs of Can$0.20 per head, excluding ear tags. The system will provide herd of origin traceback and individual animal identification by ear tags for all beef cattle. A number of identification technologies are available that would have advantages over visual tags, but these are currently too costly without government support (electronic identification, deoxyribonucleic acid [DNA] fingerprinting), too slow (DNA fingerprinting) or have not been tested sufficiently (retinal imaging) to warrant mandatory inclusion in a national traceback/identification system.

Practical measures for reducing risk of alfalfa bloat in cattle.

Abstract: Frothy bloat in cattle is a serious problem and is difficult to manage under field conditions as it progresses rapidly from early signs of distension to acute distress. Scientists at Agriculture and Agri-Food Canada centres in Western Canada are committed to the development of bloat-free alfalfa grazing systems, which may require feed additives or supplements. As well, a new cultivar of alfalfa (AC Grazeland), selected for a low initial rate of digestion, will soon be available. In grazing trials the cultivar reduced the incidence of bloat by an average of 56% compared with the control cultivar (Beaver). Commonly accepted mineral mixes for the prevention of bloat were tested and found ineffective but we have confirmed that poloxalene (Bloatguard) is 100% effective if it is given intraruminally at the prescribed dose. However, under practical conditions, poloxalene can only be offered free choice and protection from bloat cannot be guaranteed. We have also shown that the water soluble polymer, Blocare 4511, when used in the water supply is 100% effective in bloat prevention. This product is not yet registered in North America. Other strategies for bloat prevention will be discussed, including the selection of growth stages and grazing schedules, and the reduction of risk by wilting alfalfa or combining it with tannin-containing forages. DOI:10.2458/azu_jrm_v54i4_majak

Effect of salinomycin or monensin on performance and feeding behavior of cattle fed wheat- or barley-based diets

Abstract: Feeding behavior and growth performance of cattle fed diets containing monensin or salinomycin were assessed in two trials. In trial 1, 36 Hereford × Angus steers (267.7 ± 4.3 kg) were individually fed (n = 12) wheat-based transition and finishing diets containing no ionophore (control, C), 26 mg monensin (M) or 13 mg salinomycin (S) per kg of dietary dry matter (DM). Cattle fed M consumed less than those fed C or S, and their intake was more stable during the transition to the finishing diet. Overall, steers fed M exhibited lower dry matter intake (DMI) (8.0 vs. 9.2 and 9.2 kg d–1) and rates of gain (1.21 vs. 1.62 and 1.56 kg d–1) than those fed C or S. Cattle fed S required fewer days (93.3) to reach the targeted finish (5 mm backfat) than those fed C or M (105.8 d). Monensin reduced slaughter weight and carcass weights, relative to controls (414.3 vs. 480.5 kg, and 231.2 vs. 245.8 kg, respectively). In trial 2, M (25 ppm) or S (13 ppm) were included in barley-based diets for 72 yearling steers placed i...

Enzymes as Direct-Feed Additives for Ruminants

Abstract: Fibrolytic enzymes hold great potential to improve feed utilization and productivity in ruminants. In the past, it was believed that the endogenous activity against plant cell walls could not be augmented by supplementary exogenous enzymes. However, when diets of dairy and beef cattle are supplemented with commercial xylanases and cellulases, animal performance is significantly improved. The most likely site of action is the rumen rather than in the small intestine as is the case for poultry. Because of the complexity of the rumen environment, it has been difficult to identify the exact mode of action for this beneficial response. Since xylanases and cellulases are the main activities that occur in efficacious enzyme mixtures, it may be assumed that the enzymes are having a direct, additive effect on the hydrolysis of plant fiber in the rumen. However, evidence to date suggests that the benefits of exogenous enzymes is synergistic to ruminal endogenous enzymes. This synergy may explain why relatively small amounts of enzyme can have such large effects on animal productivity. Limitations to the exploitation of this technology are the development of an adequate screening system for new enzymes, and the identification of the specific enzyme activities that are critical for efficacy.

Efficacy of Rumensin controlled release capsule for the control of alfalfa bloat in cattle

Abstract: Rumensin controlled release capsule (CRC) was evaluated in grazing trials and in confinement with fistulated steers fed alfalfa at the vegetative to early bud stage of growth. These stages promoted a high incidence of bloat, both in animal days of bloat and in daily frequency of distension. The bolus reduced the incidence of bloat by an average of 50% in five trials, the difference being statistically significant in four of them. The cultivars AC Grazeland and Alfagraze did not differ significantly in daily bloat incidence when evaluated at early stages of growth. Key words: Cattle, bloat, legumes, Medicago sativa L.