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PubMed1988

Influence of addition of yeast culture supplement to diets of lactating cows on ruminal fermentation and microbial populations.

Six ruminally fistulated Holstein cows were utilized in a randomized block design to examine effects of yeast culture supplement on ruminal metabolism and apparent digestibility. Cows were fed a diet of 40% corn silage and 60% concentrate (DM basis). Treatments were control (supplement without yeast cells) and yeast culture supplement. Treatment periods were 6 wk. Ruminal pH, ammonia, molar proportions of acetate and isovalerate, and acetate: propionate ratio were lower and molar proportions of propionate and valerate higher in cows receiving yeast. The concentration of anaerobic bacteria tended to be higher and cellulolytic bacteria concentrations were greater in cows fed yeast than in cows receiving control diet. Supplemental yeast did not affect molar proportions of isobutyrate or butyrate, total VFA, or viable yeast concentrations in ruminal fluid. Ruminal liquid dilution rate and total tract apparent digestibilities were not different between treatments. Rate of disappearance of cellulose in vitro was lower in cows receiving yeast. Less variation in ammonia concentrations and microbial numbers suggest that ruminal fermentation was more stable in cows receiving yeast culture supplement.

Animals↗
PubMed1990

Dietary fat and ruminally protected amino acids for high producing dairy cows.

Eight early lactation Holstein cows, used in a replicated 4 x 4 Latin square design, were fed the following diets: control; control plus ruminally protected amino acids (15 g methionine and 20 g lysine); control plus added fat (.32 kg 60:40 animal and vegetable blend and .36 kg of Ca salts of fatty acids); control plus ruminally protected amino acids plus added fat. The objective was to examine the effect of ruminally protected forms of lysine and methionine and dietary fat on milk yield and composition. Cows were fed for ad libitum consumption of total mixed diets consisting of 50% forage and 50% concentrate on a DM basis. Added fat increased milk, fat, and 4% FCM yield but decreased milk protein percentage. Ruminally protected amino acids increased milk protein percentage. The combined effect of fat and ruminally protected acids increased milk fat percentage and yield more than the sole addition of either supplement. Added fat increased the percentage and yield of long-chain fatty acids in milk. Plasma free fatty acids were also increased by fat addition. Adding ruminally protected amino acids to fat-supplemented diets may help alleviate the milk protein depression found with added fat.

Animals↗
PubMed1991

Ruminal metabolism, fiber, and protein digestion by lactating cows fed calcium soap or animal-vegetable fat.

Effects of two levels of Ca soap or animal-vegetable fat on digestion of fiber and N and on microbial protein synthesis were studied in five ruminally and duodenally cannulated lactating cows in a 5 x 5 Latin square. Fat was added at 0, 2.5%, or 5% of dietary DM, which consisted of a 60:40 forage:concentrate mix. Treatment did not influence DMI, duodenal OM flow, or digestibility. Fat linearly increased liquid dilution rate (12.1 vs. 11.1 h-1) and reduced liquid (53.6 vs. 62.4 L) and ruminal (61.6 vs. 70.1 L) volumes. Source and amount of fat did not influence mean ruminal pH, ammonia N, or VFA concentrations; however, animal-vegetable fat reduced acetate:propionate ratios compared with Ca soap (3.47 vs. 3.64). Neither source nor amount of fat influenced fiber flow, digestion, or efficiency of microbial protein synthesis. Source and amount of fat did not change ruminal or total digestibilities of DM, OM, ADF, or NDF; however, dietary fat increased total tract apparent digestion of N (70.3 vs. 66.8). Estimates of ruminal DM digestibility were lower (24.2 vs. 39.0) and total tract DM digestibility was higher (63.3 vs. 60.5) with Cr marker compared with C31 hydrocarbon marker. Animal-vegetable fat or Ca soap can be supplemented up to 5% of the dietary DM in high forage diets without adverse effects on ruminal metabolism and digestion.

Ammonia↗
PubMed1992

Sodium bicarbonate and yeast culture effects on ruminal fermentation, growth, and intake in dairy calves.

Sodium bicarbonate and yeast culture effects on ruminal fermentation, intake, and growth were evaluated in young calves. In trail 1, nine ruminally cannulated Holstein calves averaging 12 wk of age were fed control starter (17% CP) or starters containing 3% sodium bicarbonate or .2% yeast (Saccharomyces cerevisiae) culture in a 3 x 3 Latin square. Calves were fed for ad libitum consumption for 10 d and then at 85% of ad libitum intake to d 14. Ruminal fluid taken at 0 h postfeeding tended to have higher pH and a greater proportion of acetate when calves were fed sodium bicarbonate, but other ruminal and blood parameters did not differ among treatments. By 4 h after feeding, ruminal VFA had increased to 120.7 mM, molar proportions of individual acids were altered, and blood ketones and VFA increased in treated calves. In trial 2, 42 Jersey calves were fed experimental starters for ad libitum consumption during a 12-wk study. Calves began the study at 3 to 5 d of age. There were no significant effects of yeast culture or sodium bicarbonate on DMI or intake of starter, rates of gain, or feed efficiency. Plasma urea N was reduced when sodium bicarbonate was fed. Both sodium bicarbonate and yeast culture affected blood and ruminal metabolites when calves were limit-fed but did not influence intake or daily gain when calves were fed for ad libitum consumption.

Animal Feed↗
PubMed1996

Effects of Saccharomyces cerevisiae and Aspergillus oryzae cultures on ruminal fermentation in dairy cows.

Four lactating Holstein cows, fitted with ruminal and duodenal cannulas, were used in a 4 x 4 Latin square design to examine the effects of supplemental yeast (Saccharomyces cerevisiae) and fungal (Aspergillus oryzae) cultures on ruminal fermentation, microbial populations, and nutrient supply to the small intestine. Cows were fed a basal diet comprising 32.5% corn silage, 17.5% alfalfa hay, 35.3% corn grain, 12.7% soybean meal, and 2% vitamin and mineral mixture on a DM basis. Treatments were arranged in a 2 x 2 factorial as follows: 1) basal diet, 2) basal diet plus 57 g/d of yeast culture, 3) basal diet plus 3 g/d of fungal culture, and 4) basal diet plus 57 g/d of yeast culture and 3 g/d of fungal culture. Ruminal pH, ammonia N concentration, and total VFA concentration were similar among treatments. Molar percentages of ruminal isoacids were lower for cows fed a mixture of yeast and fungal culture than for cows fed yeast or fungal culture alone. Yeast culture increased ruminal OM and CP digestion and decreased OM and N flow to the duodenum. Fiber digestion in the rumen was similar among treatments. Fungal culture stimulated proteolytic and cellulolytic bacterial counts. Proteolytic bacterial counts were also stimulated by yeast culture. Results from this experiment demonstrated that yeast and fungal cultures could influence ruminal fermentation and microbial populations.

Ammonia↗
PubMed1998

Influence of soybean oil in high fiber diets fed to nonlactating cows on ruminal unsaturated fatty acids and nutrient digestibility.

An experiment with a 5 x 5 Latin square design was conducted to determine the effects of the addition of soybean oil to high fiber diets on ruminal fermentation and ruminal lipid concentrations. Diets were 50% bermudagrass hay and 50% concentrate. Soybean oil was added to diets at 0, 2, 4, 6, or 8% of the dietary dry matter (DM). Ruminal samples were collected every 2 h on the last day of each period and analyzed for volatile fatty acids and lipids. The addition of soybean oil decreased DM and organic matter intake but increased fatty acid intake. Soybean oil had no effect on total tract digestibility of DM, organic matter, N, or neutral detergent fiber but decreased digestibility of fatty acids. The addition of soybean oil decreased total volatile fatty acid concentrations and the acetate to propionate ratio. Ruminal concentrations of unsaturated free fatty acids increased nonlinearly as soybean oil in the diets increased but remained < 0.67 mg/g of DM or 3% of the total fatty acids. Ruminal concentrations of total fatty acids and total saturated fatty acids increased nonlinearly as soybean oil in the diets increased. Total unsaturated fatty acid concentrations increased linearly as soybean oil increased. Neutral lipid concentrations in the rumen did not respond to increased soybean oil. These data indicate that large amounts of soybean oil can be fed in high fiber diets without greatly increasing the concentration of ruminal unsaturated fatty acids or depressing nutrient digestibility.

Animal Nutritional Physiological Phenomena↗
PubMed1998

Effect of soybean hulls, soy lecithin, and soapstock mixtures on ruminal fermentation and milk composition in dairy cows.

Two experiments were conducted to determine effects of soybean hulls, soy lecithin, and soapstock mixtures on ruminal fermentation, milk composition, and ruminal microbial populations. In Experiment 1, 20 Holstein dairy cows were assigned to one of five total mixed rations (TMR) in replicated 5 x 5 Latin squares to measure the effect of TMR on intake and milk composition. Four ruminally fistulated cows were used in a 4 x 5 Youden square to measure the effect of TMR on ruminal fermentation. The TMR consisted of 40 or 50% alfalfa and corn silages, 13% soybean hulls, and 47 or 37% of a concentrate containing either 2.25% soybean oil; 2.25% lipid from a mixture of soybean hulls, soy lecithin, and soapstock; or no added lipid. The ratios of soy lecithin to soapstock evaluated were 1:1, 2.5:1, and 4:1 (dry basis). The TMR containing soy lecithin and soapstock at ratios of 1:1 and 2.5:1 resulted in higher milk C18:2 than did the soybean oil TMR. Rate of ruminal NDF digestion of soybean hulls was reduced for the soybean oil TMR. In Experiment 2, a semi-continuous culture system was used to determine effects of soybean oil or an optimal mixture of soy lecithin and soapstock (1:1, wt/wt) on fermentation of soybean hulls and microbial populations. The TMR containing the lipid mixture increased the ratio of acetate to propionate compared with the TMR containing soybean oil and resulted in higher total protozoal counts than did the control TMR. The TMR containing mixtures of soy lecithin and soapstock at ratios of 1:1 and 2.5:1 elevated milk C18:2, and no negative effect on NDF digestion was detected, indicating some degree of ruminal protection.

Animal Feed↗
PubMed1998

Ruminally protected lysine or lysine and methionine for lactating dairy cows fed a ration designed to meet requirements for microbial and postruminal protein.

The purpose of this study was to separate the effects of ruminally protected Lys from effects of ruminally protected Met on the performance of lactating dairy cows fed a ration calculated to be first-limiting in intestinally delivered Lys and second-limiting in intestinally delivered Met. Thirty multiparous Holstein cows were examined in a 20-wk study that started on wk 5 postpartum. Rations contained timothy silage, corn silage, barley, corn, corn gluten meal, and soybean meal. Treatments were 1) no supplemental amino acids, 2) 21 g/d of intestinally available Lys, and 3) 22 g/d of intestinally available Lys and 6 g/d of intestinally available Met. Post-experimental calculations suggested that, in contrast to the objective, the unsupplemented ration was colimiting in intestinally available His (0.96 of requirement), followed by Lys (1.00), digestible ruminally undegraded protein (1.01), Ile (1.03), Arg (1.04), Val (1.10), and Met (1.14). In this context, the virtually identical performance of cows fed the unsupplemented ration and cows fed the ration supplemented with ruminally protected Lys demonstrated that dairy cows did not respond to enhanced intestinal supplies of Lys when Lys was not calculated to be the first-limiting nutrient. In contrast, for cows fed rations supplemented with both ruminally protected Lys and ruminally protected Met, the production of both milk protein (40 g/d) and fat (40 g/d) was numerically increased to an extent that was consistent with earlier reported studies, although calculations did not indicate that performance was limited by intestinal supplies of Lys or Met. This result, which may be disputed because of a lack of statistical significance, suggests that Met, apparently unlike Lys, may enhance the production of milk components beyond an enhancement expected because of its role as a limiting amino acid.

Animals↗
PubMed1998

Ruminal escape and apparent degradation of amino acids administered intraruminally in mixtures to cows.

The apparent ruminal degradation and escape of amino acids (AA) administered in 9 different mixtures of essential AA and 8 different mixtures of nonessential AA were studied using two cows fitted with ruminal cannulas. The 600-mmol AA mixtures, which were administered intraruminally using polyethylene glycol as a liquid marker, contained equal amounts of two, four, or eight AA. The amounts of each of the AA in the mixtures were 300, 150, and 75 mmol, respectively. Ruminal degradation and escape were compared with values previously reported for AA administered individually. Across doses, the mean rate of initial degradation (degradation during the 1st h after administration) of essential AA was 26% when the AA were administered in mixtures and 45% when the AA were administered individually. For nonessential AA, the corresponding values were 34 and 54%. Across doses, mean ruminal escape during the first 8 h after essential AA administration was 22% when the AA were administered in mixtures and 16% when the AA were administered individually. For nonessential AA, the corresponding values were 13 and 11%. After intraruminal administration of AA, both individually and in mixtures, significant negative correlations were found between rates of degradation during the 1st h and ruminal escape during an 8-h period. Some AA mixtures caused a net increase in the concentration of other AA in ruminal fluid 1 h after administration. Twelve of the mixtures that did not contain Ala caused a considerable net increase in the concentration of this AA, and 3 AA mixtures containing Arg and Ala caused a marked net increase in the concentration of Trp.

Alanine↗
PubMed2002

Effects of ruminal and postruminal infusion of starch hydrolysate or glucose on the microbial ecology of the gastrointestinal tract in growing steers.

Forty crossbred steers were used to determine the effects of carbohydrate supply site on the indigenous bacteria of the gastrointestinal tract. Steers were fitted with ruminal and abomasal infusion catheters and assigned randomly to one of eight groups in a complete randomized block design. The experimental period was 36 d. Treatments included: 1) a pelleted basal diet fed at 0.163 Mcal ME x (kg BW(0.75)) x 1 x d(-1) (LE); 2) the basal diet fed at 0.215 Mcal ME x (kg BW(0.75)) (-1) x d(-1) (HE); 3) the basal diet fed at 0.163 Mcal ME x (kg BW(0.75))(-1) x d(-1) with ruminal infusion of starch hydrolysate (SH) (RSH); 4) the basal diet fed at 0.163 Mcal ME x (kg BW(0.75))(-1) x d(-1) with abomasal infusion of SH (ASH); and 5) the basal diet fed at 0.163 Mcal ME x (kg BW(0.75))(-1) x d(-1) with abomasal infusion of glucose (AG). The total volume ofinfusate (5 kg x site(-1) x d(-1)) was equalized across treatments and infusion sites by infusion of water. Glucose and SH were infused at rates of 14.35 and 12.64 g x (kg BW(0.75)) x d(-1), respectively. Ruminal, cecal, and fecal samples were obtained on d 36. Ruminal pH was low (5.79) in LE steers and unaffected (P > 0.10) by increased energy intake or carbohydrate infusion. Cecal and fecal pH were 6.93 and 7.00, respectively, for LE steers. Increasing energy intake (P < 0.10) and the rate of carbohydrate infusion (P < 0.01) significantly decreased cecal and fecal pH compared with LE. Ruminal counts of anaerobic bacteria in LE steers were 8.99 log10 cells/g and abomasal carbohydrate infusion had no affect (P > 0.10) on these numbers. However, ASH and AG steers had approximately 1.5 log10 cells/g more (P < 0.01) cecal and fecal anaerobic populations. Ruminal, cecal, and fecal aerobic bacterial counts were 40, 22, and 23%, respectively, lower than anaerobic counts. Generally, aerobic counts responded similarly to the anaerobic counts. Less than 1% of the anaerobic bacteria enumerated in the rumen, cecum, and feces were coliforms, and 97% of the coliforms were Escherichia coli. Carbohydrate infusions resulted in only numerical increases in fecal coliform and E. coli concentrations (P > 0.10). Fecal E. coli were highly acid sensitive in all steers, with less than 1% surviving a 1-h exposure to low pH (2.0). This suggests that cecal or fecal pH is not a good indicator of acid resistance, and it supports the concept that there are other factors that may induce acid resistance.

Abomasum↗
PubMed1992

Improved animal production by genetic engineering of ruminal bacteria.

Ruminant production is a major focus of Australian agriculture. The ability of ruminant animals such as sheep and cattle to make productive use of low quality plant materials depends on the activity and efficiency of the anaerobic microbial population that resides in the rumen. Factors that affect ruminant production include the ability of cellulolytic microorganisms to digest plant structural polysaccharides (primarily cellulose and hemicellulose), the capacity of microorganisms to metabolise and detoxify otherwise inhibitory plant products and the efficiency of nitrogen utilisation by ruminal organisms. This review will consider some current Australian research programs aimed at improving ruminant production efficiency by genetic engineering of ruminal bacteria.

Agriculture↗
PubMed1991

Alterations in ruminal utilization of magnesium and zinc in lambs fed different ratios of concentrate: forage.

Twelve wether lambs were used to study the effects of concentrate level on ruminal utilization of Mg and Zn. Treatments consisted of concentrate: forage ratios (C:F) of 10:90, 40:60, and 70:30. Ruminal pH.hours (pH x hours area below 6.7 in 24-hour period) increased (P less than .01; linear) with increasing C:F. Bacterial intestinal Mg flow increased (P less than .01; linear) with increasing C:F and was strongly correlated with pH.hours (r = .75, P = .008). Ruminal Mg absorption was not affected (P greater than .05) by C:F, but correlated well with bacterial intestinal Mg flow (r = .66; P = .026). As with Mg, intestinal flow of bacterial Zn increased (P less than .01; linear) with increasing C:F and was highly correlated with pH.hours (r = .76, P = .006). Ruminal Zn absorption declined (P less than .05; linear) with increasing C:F and correlated well with bacterial Zn flow (r = -.82, P = .002). Data suggest that ruminal pH and (or) bacterial accumulation of Mg and Zn may compromise ruminal absorption of these minerals.

Animal Feed↗
PubMed1989

[Bacteriological examination of saliva of institutionalized severely mentally retarded persons with chronic rumination].

The purpose of this study was to investigate dental caries prevalence, the pH and the presence of bacteria in the saliva of institutionalized severely mentally retarded persons with chronic rumination. The results obtained were as follows: The prevalence of dental caries among the group with chronic rumination was higher than among the group not suffering from rumination. The viable cell number of mutans streptococci, lactobacilli and yeasts in the group with chronic rumination was significantly higher than that of group without rumination. These results suggested that the saliva of the group with chronic rumination creates a favourable environment for aciduric bacterial growth.

Dental Caries↗
PubMed1986

[Hormonal control of hepatic metabolism in ruminants].

Insulin/glucagon control of hepatic metabolism, i.e. a endocrine-nervous system, is one of the general systems of integration in vertebrates. In this system, substrates coming from the digestive tract or from extrahepatic metabolism are important messenger molecules. Liver uptake of insulin and glucagon mainly accounts for high metabolic clearance rates of these hormones in both ruminants and non-ruminants. Glucagon infusion into ruminants results in an increase in the net hepatic uptake of glucose precursors and gluconeogenesis. Glucagon effects have also been demonstrated in isolated hepatocytes. Glucagon, through its effect on pyruvate carboxylase (EC 6.4.1.1.) may regulate gluconeogenesis. Insulin infusion induces hypoglycaemia. As a result, glucagon secretion increases and counterregulates insulin action. However, it has been shown that hepatic gluconeogenesis decreases during euglycaemic hyperinsulin clamp, mainly due to a decrease in the hepatic supply of glucose precursors following insulin action in extrahepatic tissues. Insulin fails to elicit any significant effect in vitro. Hepatocytes exhibit insulin and glucagon receptors. The apparent characteristics of hormone binding in vitro are similar in ruminants and non-ruminants, but the characteristics of postreceptor events are unknown in the former. Glucagon, which influences hepatic glucose synthesis, may be a major hormone in ruminants.

Amino Acids↗
PubMed1987

[Food ingestion in ruminants: modalities and associated phenomena].

This paper synthesizes the literature on modalities of food intake in ruminants and their main associated phenomena. Firstly, circadian distribution of feeding and ruminating activities has been examined. Ruminants spend a large part of their time chewing. Their meals have been described in detail; changes in rates of intake, time spent eating, the effect of restricting the amount fed or the period of feed accessibility have been discussed. When food is distributed, the animals have a "long" meal. These meals have been analysed in relation to the type of animal and the feed offered. The other meals ("small" meals) have been briefly described. The paper next examines the phenomena associated with meals, or induced by them, and implied in the control of food intake. Forestomach motricity varies according to ruminant feeding behavior and plays a basic role in digesta transit. Rumen content varies with the meal and its chemical composition due to the arrival in the rumen of food, water and saliva. Rumination may require 600 to 650 min/day and is important in the comminution and sorting of rumen particles. The digestive phenomena associated with meals are related to control of intake. The influence of rumen fill has been thoroughly discussed. Finally, main humoral changes due to intake have been reviewed. The influence of volatile fatty acids (VFA) and metabolites has been discussed as well as the role of glucose, amino acids and fatty acids. Among the hormones, insulin and glucagon seem to play an important role in controlling food intake. The amounts of gastrointestinal hormones increase during intake and may also play an important part. Despite a net improvement in the knowledge of phenomena related to intake, much still remains to be done in setting up models to describe these phenomena in relation to feeding activities and to aid in understanding the mechanisms controlling feed intake in ruminants.

Animals↗
PubMed1985

Ruminal lactic acidosis: relationship of forestomach motility to nondissociated volatile fatty acids levels.

Ruminal lactic acidosis was produced in 9 overnight fasted rumen-fistulated sheep by placing ground wheat (40 g/kg of body weight) into the rumen. Ruminal stasis occurred within 8 hours of grain engorgement in 6 sheep (early stasis group) and between 10 and 12 hours in the remaining 3 sheep (late stasis group). The initial impairment to forestomach motility was a decrease in the mean frequency of reticulo-ruminal contractions which occurred within 4 hours of the intraruminal placement of wheat in the early stasis group and within 6 hours in the late stasis group. Since blood pH, carbon dioxide pressure, and serum bicarbonate were all normal, systemic acidosis was not a contributing factor to this decrease in contraction frequency. The concentrations of total nondissociated volatile fatty acids (VFA; acetic, propionic, and butyric acid) in ruminal fluid, however, were significantly increased, being 13.60 mM/L (mean, pH 4.92) in the early stasis group and 15.77 mM/L (pH 4.80) in the late stasis group. Free DL-lactic acid in ruminal fluids was 6.37 +/- 6.1 mM/L (mean +/- SD) in the early stasis group and 9.72 +/- 4.2 mM/L in the late stasis group. A reduction in contraction amplitude was observed within 6 hours of grain engorgement in the early stasis group and within 8 hours in the late stasis group. At these times, the concentrations of nondissociated VFA were 10.19 mM/L (pH 4.46) in the early stasis group and 10.52 mM/L (pH 4.62) in the late stasis group. The ruminal values of free DL-lactic acid were 13.93 mM/L in the early stasis group and 16.14 mM/L in the late stasis group.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1979

Influence of ruminal turnover on site and extent of digestion.

Ruminal turnover rate plays a major role in ruminant nutrition. Theoretical considerations have been developed and several excellent models are available. Newer methods in marker technology offer opportunity for collection of accurate data. Few good studies have been published. This paper covers the above considerations and gives a critical evaluation of some published data. Increased ruminal turnover of liquid alters ruminal fermentation toward more acetate, butyrate and methane and less propionate. It also results in a greater rate of passage of small feed particles of any type. The effect on total digestion depends on feed composition and physical form. Total fiber digestion is usually reduced. Ruminal liquid turnover is increased by increased level of intake, addition of coarse fiber to rations, and osmotically active agents. It is reduced by some mineral complexes and monensin, and by reducing average particle size. Solid turnover rate is increased by reduced particle size and by several factors that influence liquid turnover. The rate of particle size reduction to a critical size is important in any description of solid turnover rate. Literature data that relate to ruminal turnover and in vivo digestion are discussed.

Anaerobiosis↗
PubMed1984

Stomach lysozymes of ruminants. I. Distribution and catalytic properties.

A major regulatory shift affecting the expression of lysozyme c may have been involved in the origin of two groups of mammals whose nutrition depends on foregut bacteria. A survey of 23 mammalian species reveals that the lysozyme c activity per g of stomach mucosa is many times higher for ruminants and a leaf-eating monkey than for animals lacking a foregut. The implication is that stomach lysozyme c functions as a major digestive enzyme in ruminant-like mammals, helping to make those bacterial which enter the stomach from the foregut available for hydrolysis by conventional digestive enzymes. The high level of stomach lysozyme is due to more enzyme molecules rather than to an increase in the activity of each molecule. This was shown for the cow by purifying the three, non-allelic lysozymes c that account for the lysozyme activity in gastric mucosa and measuring their specific activities and for other foregut fermenters by immunological titration. Lysozyme appears in the stomach mucosa before birth and reaches adult levels before weaning. Other tissues tested from cattle lack lysozyme c and may instead have low levels of another lysozyme that could belong to the g class, the first indication that lysozyme g may be present in mammals. The lysozymes of eight ruminants, four Old World monkeys, and 12 other animals were compared as regards the ability to lyse bacterial cells under various conditions and to resist inactivation by pepsin. There are differences among these species in the dependence of the rate of bacterial lysis on time, pH, and ionic strength. Although not every lysozyme was tested in all of these catalytic respects, there were no exceptions to the following generalizations. First, at ionic strengths above 0.1 and pH values above 5, the rate of lysis by ruminant and monkey lysozymes c rose with the time of reaction, whereas the rate was more nearly constant for the other animal lysozymes. Second, the lytic activity at neutral pH is lower than at pH 5 for the ruminant and monkey lysozymes c when the ionic strength is over 0.1; by contrast, for other lysozymes c under these conditions the activity at neutral pH is about as high as at pH 5. This latter property, which may be viewed as an adaptation for functioning as a digestive enzyme in the stomach, can be explained in part by differences in electrostatic interactions between lysozyme and the substrate due to the relatively non-basic nature of ruminant and monkey lysozymes compared to other lysozymes c.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗