Functional properties of cream from dairy cows with experimentally altered milk fat composition.

Modification of milk fat composition might be a desirable method to alter manufacturing characteristics or produce dairy products low in saturated fat that more closely meet consumer dietary preferences. The aim of this research was to evaluate functional properties of cream obtained from milks with fat composition modified by altering the profile of long-chain fatty acids (FA) absorbed from the intestine. A control and 5 mixtures of long-chain free FA were infused into the abomasum of lactating dairy cows in a 6 × 6 Latin square design with 21-d periods. Treatments were as follows: (1) control (no FA infused), (2) mostly saturated FA (C16:C18 = 0.74), (3) low linoleic palm FA (C16:C18 = 0.73), (4) palm FA (C16:C18 = 0.73), (5) soy FA (C16:C18 = 0.10), and (6) high palmitic soy FA (C16:C18 = 0.73). All treatments included meat solubles and Tween 80 as emulsifiers. Viscosity, overrun, whipping time, foam firmness, and foam stability were evaluated in creams (33% fat). Cream from cows infused with soy FA (treatment 5) had the longest whipping time and lowest overrun, foam stability, viscosity, melting point, firmness, and solid fat content at 5 and 20°C because the fat had the highest unsaturated FA content. Increasing palmitic acid content of soy FA (treatment 6) improved functional variables in cream relative to soy FA alone. Differences among treatments 1 to 4 were less pronounced because of the effect of C18:1 trans in treatments 3 and 4 on milk fat yield and composition. Milk fat from cows infused with palm FA (treatment 4) exhibited comparable or better functionality than control cream. Increased polyunsaturated FA in milk fat resulted in increased amounts of triglyceride (TG) fractions with 28, 30, 38, and 40 carbon numbers, increased oleic acid resulted in increased 50-carbon TG, and higher palmitic and myristic acids resulted in greater 44, 46, and 48 carbon number TG. These TG groups consistently correlated with functional properties of creams from different treatments. Our results indicated that optimal functionality of cream is dependent more on its content of palmitic acid than on unsaturated FA. However, an optimal composition of milk fat for cream functional characteristics might be obtained through nutritional manipulation of diets for dairy cows to deliver an optimal profile of FA.

Fat profile of jamaican ackees, oleic Acid content and possible health implications.

OBJECTIVE: To re-investigate the composition of ackee oil and unequivocally determine its principal fatty acid components. METHODS: Oil was extracted from the edible portion of ackees harvested in three different studies (I-III) by several analysts; studies I and II utilized composite samples from several trees while study III consisted of ackees from seven separate trees. The oils were either saponified and methylated or trans-methylated and the fatty acid methyl ester content analysed by gas chromatography-mass spectrometry (GC-MS). Relative fatty acid composition was quantified based on chromatographic peak areas while fatty acids were identified by mass spectrometry. The degree of unsaturation of the ackee oils was characterized by determination of the iodine value. RESULTS: Gas chromatography-mass spectrometry data from the three studies were assessed. Relative fatty acid composition for the ackee oils was consistent across the three studies. The major fatty acid components were oleic acid (55.44%), palmitic acid (25.57%) and stearic acid (12.59%); linoleic acid was present in minor to undetectable amounts. An iodine value of 49 was determined which is consistent with the high oleic acid content of the ackee oil. CONCLUSION: The ackee samples analysed were rich in the monounsaturated fatty acid (MUFA) oleic acid. Consideration should be given to potential protective health effects of diets which include ackee.

Fat profile of Jamaican ackees, oleic acid content and possible health implications / Perfil de grasas del seso vegetal jamaicano, contenido de ácido oleico, y posibles implicaciones para la salud

OBJECTIVE: To re-investigate the composition of ackee oil and unequivocally determine its principal fatty acid components. METHODS: Oil was extracted from the edible portion of ackees harvested in three different studies (I - III) by several analysts; studies I and II utilized composite samples from several trees while study III consisted of ackees from seven separate trees. The oils were either saponified and methylated or trans-methylated and the fatty acid methyl ester content analysed by gas chromatography-mass spectrometry (GC-MS). Relative fatty acid composition was quantified based on chromatographic peak areas while fatty acids were identified by mass spectrometry. The degree of unsaturation of the ackee oils was characterized by determination of the iodine value. RESULTS: Gas chromatography-mass spectrometry data from the three studies were assessed. Relative fatty acid composition for the ackee oils was consistent across the three studies. The major fatty acid components were oleic acid (55.44%), palmitic acid (25.57%) and stearic acid (12.59%); linoleic acid was present in minor to undetectable amounts. An iodine value of 49 was determined which is consistent with the high oleic acid content of the ackee oil. CONCLUSION: The ackee samples analysed were rich in the monounsaturated fatty acid (MUFA) oleic acid.Consideration should be given to potential protective health effects of diets which include ackee.

OBJETIVO: Re-investigar la composición del aceite del seso vegetal (ackee) y determinar de manera inequívoca sus componentes principales de ácidos grasos. MÉTODOS: Se extrajo el aceite de la porción comestible de sesos vegetales de la Blighia sapida (ackee), cosechados como parte de tres estudios diferentes (I - III) por varios analistas. Los estudios I y II utilizaron muestras combinadas de varios árboles de Blighia sapida, en tanto que el estudio III estuvo formado por muestras de siete árboles de Blighia sapida por separado. Los aceites fueron saponificados y metilados o transmetilados, y el contenido de éster metílico de ácidos grasos fue analizado mediante técnicas de cromatografía de gases y espectrometría de masas (GC-MS). La composición relativa de ácidos grasos se cuantificó sobre la base de las áreas cromatográficas pico, mientras que los ácidos grasos se identificaron mediante espectrometría de masas. El grado de insaturación de los aceites de seso vegetal fue caracterizado mediante la determinación del valor de yodo. RESULTADOS: Se evaluaron los datos de la cromatografía de gases acoplada con espectrometría de masas de los tres estudios. La composición relativa de ácido grasos de los aceites de seso vegetal, fue constante a través de los tres estudios. Los componentes principales del ácido graso fueron el ácido oleico (55.44%), el ácido palmítico (25.57%), y el ácido esteárico (12.59%). El ácido linoleico estuvo presente en cantidades que fluctuaron de menores a indetectables. Se determinó un valor de yodo de 49, el cual está en correspondencia con el alto contenido de ácido oleico en el seso vegetal. CONCLUSIÓN: Las muestras analizadas de sesos vegetales de la Blighia sapida (ackee) eran ricas en ácidos grasos monoinsaturados (MUFA por sus siglas en inglés) y ácidos oleicos. Debe prestarse atención a los posibles efectos protectores de la salud de dietas que incluyen sesos vegetales.

Functional properties of butter oil made from bovine milk with experimentally altered fat composition.

Modification of milk fat composition might be desirable to alter manufacturing characteristics or produce low saturated fat dairy products that more closely meet consumer dietary preferences. The aim of this research was to evaluate functional properties of butter oil obtained from milks with fat composition modified by altering the profile of long-chain fatty acids (FA) absorbed from the small intestine of cows. A control and 5 mixtures of long-chain free FA were infused into the abomasum of lactating dairy cows in a 6 x 6 Latin square design with 21-d periods. Treatments were 1) control (no FA infused), 2) mostly saturated FA (C16:C18 = 0.72), 3) low-linoleic palm FA (C16:C18 = 0.85), 4) palm FA (C16:C18 = 0.72), 5) soy FA (C16:C18 = 0.10), and 6) high-palmitic soy FA (C16:C18 = 0.68). All treatments included meat solubles and Tween 80 as emulsifiers. Solid fat content (from 0 to 40 degrees C), melting point, and force at fracture were determined in butter oil. Milk fat from cows infused with palm FA (treatment 4) exhibited functionality equal to or better than control butter oil. Infusion with palm FA increased amounts of triglyceride (TG) fractions with 48, 52, and 54 carbon numbers but decreased TG with 32, 34, 36, and 42 carbon numbers. Infusion with soy FA increased TG with 26, 38, 40, 52, and 54 carbon numbers but decreased TG with 34, 42, and 46 carbons. Infusion of the mostly saturated FA increased TG with 38, 50, 52, and 54 carbon numbers but decreased TG with 32, 34, and 42 carbon numbers. These TG groups were consistently correlated with functional properties of butter oils from different treatments. The content of palmitic acid is important for maintaining functionality in the presence of increased polyunsaturated FA. The composition of milk fat may be able to be optimized through nutritional manipulation of diets for dairy cows if the optimal composition of FA and TG is defined for a particular dairy product.

Effects of tallow in diets based on corn silage or alfalfa silage on digestion and nutrient use by lactating dairy cows.

Six multiparous Holstein cows (average 31 days in milk; 36.3 kg/d of milk) fitted with ruminal cannulas were used in a 6 x 6 Latin square with 21-d periods to investigate the effects of diets that varied in forage source and amount of supplemental tallow. Isonitrogenous diets in a 2 x 3 factorial arrangement were based on either high corn silage (40:10 corn silage to alfalfa silage, % of dry matter) or high alfalfa silage (10:40 corn silage to alfalfa silage, % of dry matter) and contained 0, 2, or 4% tallow. Intakes of dry matter and total fatty acids were lower when cows were fed the high corn silage diet. Tallow supplementation linearly decreased dry matter intake. Milk yield was unaffected by diet; yields of milk fat and 3.5% fat-corrected milk were higher for the high alfalfa silage diet but were unaffected by tallow. Milk fat percentage was higher for the high alfalfa silage and tended to decrease when tallow was added to the high corn silage diet. Contents of trans-C18:1 isomers in milk fat were increased by high corn silage and tallow, and tended to be increased more when tallow was fed in the high corn silage diet. Ruminal pH and acetate:propionate were lower when high corn silage was fed. Ruminal acetate:propionate decreased linearly as tallow increased; the molar proportion of acetate was decreased more when tallow was added to the high corn silage diet. Ruminal liquid dilution rates were higher for the alfalfa silage diet; ruminal volume and solid passage rates were similar among diets. Total tract apparent digestibilities of dry matter, organic matter, crude protein, starch, energy, and total fatty acids were unaffected by diet. Digestibilities of neutral detergent fiber, acid detergent fiber, hemicellulose, and cellulose were lower when high corn silage was fed. The high alfalfa silage diet increased intakes of metabolizable energy and N, and increased milk energy and productive N. Tallow decreased the amount of N absorbed but had few other effects on utilization of energy or N. Tallow linearly increased concentrations of nonesterified fatty acids and cholesterol in plasma; cholesterol was increased by high alfalfa silage. Overall, forage source had more pronounced effects on production and metabolism than did tallow supplementation. Few interactions between forage source and tallow supplementation were detected except that ruminal fermentation and milk fat content were affected more negatively when tallow was fed in the high corn silage diet.

Effect of chromium supplementation on production and metabolic parameters in periparturient dairy cows.

The effect of supplemental chromium as chromium-methionine (Cr-Met) on production and metabolic parameters was investigated in 48 cows from 28 d before expected calving date through 28 d of lactation. Average body weight (BW) was 730 +/- 61 kg before treatment. Treatments were supplementation of 0, 0.03, 0.06, and 0.12 mg of Cr as Cr-Met/kg of BW(0.75). Dry matter intake increased linearly and quadratically during the prepartum and postpartum periods, respectively, and body condition score loss decreased linearly during the postpartum period with increasing Cr-Met. Increasing Cr-Met supplementation caused quadratic increases in milk, fat, and lactose yields. Treatments did not affect concentrations of blood metabolites and liver triglyceride. Serum insulin concentration and molar ratio of insulin to glucose for cows receiving Cr-Met were lower than for cows not receiving Cr-Met, but they increased quadratically with increasing Cr-Met. Glucose tolerance tests (GTT) were conducted on d 10 prepartum and d 28 postpartum. Chromium-methionine supplementation attenuated insulin sensitivity prepartum and enhanced glucose tolerance postpartum, but not prepartum. Basal insulin concentrations for cows receiving Cr-Met were higher than for cows not receiving Cr-Met during the prepartum GTT. During the postpartum GTT, peak glucose concentration and clearance rate decreased and half-life (t(1/2)) and time to reach basal concentration (T) were prolonged quadratically by increasing Cr-Met. Additionally, peak insulin concentration, area under the curve, and molar ratio of insulin to glucose were higher for cows not receiving Cr-Met than for cows receiving Cr-Met and t(1/2) and T were shortened quadratically by increasing Cr-Met.

Etiology of fatty liver in dairy cattle: effects of nutritional and hormonal status on hepatic microsomal triglyceride transfer protein.

We conducted three experiments to determine the effects of nutritional and hormonal status on microsomal triglyceride transfer protein (MTP) activity and mass. In experiment 1, 18 nonlactating Holstein cows, 75 d before expected calving date, in their second gestation or greater were monitored from d 75 to 55 prepartum. Cows were fed a control diet from d 75 to 62 prepartum for covariable measurements. From d 61 to 55 prepartum, six cows continued to receive the control diet, six cows were restricted to 2.3 kg of grass hay/d, and six cows were fed the control diet plus 1.8 kg of concentrate/d and 500 ml of propylene glycol given 2 times/d as an oral drench. Plasma glucose and serum insulin concentrations were highest in cows that received propylene glycol and lowest in feed restricted cows. Plasma nonesterified fatty acids (NEFA) and liver triglyceride (TG) concentrations were highest in feed restricted cows and not different between cows that received the control diet and cows that received propylene glycol. Hepatic MTP activity and mass were not affected by treatment in experiment 1. In experiment 2, bovine hepatocytes isolated from the caudate process of five preruminating Holstein bull calves were incubated with either 0, 0.5, 1.0, or 2.0 mM NEFA for 48 h. Intracellular TG increased linearly as NEFA concentration in the media increased. Concentration of NEFA in the incubation media had no effect on MTP activity or mass. There was a quadratic effect of concentration of NEFA in the incubation media on MTP mRNA. In experiment 3, bovine hepatocytes isolated from the caudate process of five preruminating Holstein bull calves were incubated with 2 mM [1-14C]oleate for 24 h to accumulate TG, followed by a 36-h period of TG depletion, during which hepatocytes were incubated with no hormone, 10 nM insulin, or 10 nM glucagon. There was no effect of insulin or glucagon on intracellular TG, MTP activity or mass. Cells incubated with no hormone had higher levels of MTP mRNA compared to cells incubated with insulin or glucagon during the depletion period. Results suggest that hepatic MTP mRNA may be affected by TG accumulation, insulin, and glucagon in vitro. However, hepatic MTP activity and mass are not affected by nutritional status of nonlactating dairy cows, TG accumulation in vitro, or insulin and glucagon in vitro.

Changes in hepatic microsomal triglyceride transfer protein and triglyceride in periparturient dairy cattle.

We determined the relationship between microsomal triglyceride transfer protein (MTP) (activity, mass, and mRNA) and liver triglyceride concentration in 16 dairy cows (13 multiparous and three primiparous) from 27 d before expected calving (d -27) to 35 d postpartum (d 35), the time period when fatty liver is most likely to develop. In addition, dry matter intake, plasma nonesterified fatty acids (NEFA), and plasma glucose were monitored. There were no significant parity x time interactions. Dry matter intake, plasma NEFA, plasma glucose, and liver triglyceride were significantly affected by day of sampling. Dry matter intake was 10.7, 8.0, and 19.5 kg/d on d -27, 2, and 35, respectively. Plasma NEFA concentration was higher on d 2 (1113 microEq/L) compared with d -27 (201 microEq/L) and 35 (358 microEq/L). Plasma glucose concentration was 63.3, 54.3, and 57.8 mg/dl on d -27, 2, and 35, respectively. Hepatic triglyceride (TG) concentration increased from 1.8 to 11.8% liver TG (DM basis) on d -27 and 2, respectively. There was no difference between hepatic triglyceride concentration on d 2 and 35. There was a significant effect of day of sampling on hepatic MTP activity and mRNA. Hepatic MTP activity decreased from 2.08 to 1.79 nmole triolein transferred/ h per mg of microsomal protein on d -27 and 2, respectively, and increased from 1.79 to 2.17 nmole triolein transferred/h per mg of microsomal protein on d 2 and 35, respectively. Hepatic MTP mRNA increased from d -27 to 2 and remained elevated from d 2 to 35. There was no effect of day of sampling on MTP mass. There were no significant correlations between hepatic MTP activity, mass, or mRNA with either liver TG or plasma NEFA on any of the sampling days. The cause of a decrease in hepatic MTP activity and increase in mRNA on d 2 is unknown. However, the lack of correlation between MTP activity, mass, or mRNA with either liver TG or plasma NEFA on d 2 postpartum suggests that MTP probably does not play a role in the etiology of fatty liver that occurs in dairy cows at calving.

Plasma concentration of urea, ammonia, glutamine around calving, and the relation of hepatic triglyceride, to plasma ammonia removal and blood acid-base balance.

Two experiments were conducted to test the following two hypotheses: 1) fatty liver could hamper hepatic conversion of ammonia to urea and increase circulating ammonia or Gln% [Gln% = Gln x 100/(Gln + Glu)] in cows around parturition; 2) decreased ureagenesis might cause alkalosis and in turn reduce blood Ca. In the first experiment, 14 Holstein cows were monitored from 27 d prepartum to 35 d postpartum. There was a rise in circulating ammonia and Gln% at calving, suggesting an increase in ammonia passing to and through the liver. Stepwise regression analysis revealed the following relationship for plasma samples at 22 h and liver triglyceride at 2 d postpartum: ammonia (microM) = 32.1+/-0.89 triglyceride (% DM), Gln% = 71.2 + 0.23 triglyceride (% DM) + 1.31 urea (mM). The positive correlation between liver triglyceride and plasma ammonia and Gln% suggests that hepatic triglyceride accumulation might inhibit ureagenesis, thereby increasing ammonia concentration at the perivenous hepatocytes where Gln synthesis occurs and increasing ammonia concentration in blood leaving the liver. In the second experiment, 28 rats were used to determine whether hepatic triglyceride accumulation, induced by choline deficiency, affects urinary ammonia N and blood pH homeostasis. There was a trend for a positive correlation between urinary ammonia N and liver triglyceride. No correlation between liver triglyceride and blood pH, bicarbonate, pCO2 or plasma Ca was found. In conclusion, hepatic triglyceride accumulation may inhibit ureagenesis and result in increased circulating ammonia, Gln% and urinary ammonia N in vivo. Hepatic triglyceride accumulation did not affect blood pH homeostasis.

Effects of induced parturition and estradiol on feed intake, liver triglyceride concentration, and plasma metabolites of transition dairy cows.

The effect of induced parturition and estradiol on feed intake, liver triglyceride, plasma metabolites, and milk yield was evaluated in fifty-six Holstein cows and heifers. Cows were assigned to treatments on d 260 of gestation and were on trial until d 10 postpartum for measurement of dry matter intake (DMI), plasma metabolites, and liver triglyceride and until d 31 postpartum to measure milk yield. Fourteen animals per group (9 cows and 5 heifers) received either a placebo, 1 mg of fenprostalene, 50 mg of estradiol-17 beta benzoate, or both on d 276 of gestation. Cows that received fenprostalene consumed more dry matter (DM) for the last 8 d prepartum than did cows that did not receive fenprostalene (9.6 kg/d vs. 8.5 kg/d, respectively) but consumed less DM for the first 10 d postpartum (10.9 kg/d vs. 13.1 kg/d, respectively). Cows injected with estradiol-17 beta benzoate tended to consume less DM postpartum than did cows not injected with estradiol-17 beta benzoate (11.3 kg/d vs. 12.7 kg/d, respectively). There was no effect of treatment on milk yield; however, a fenprostalene by day interaction resulted from lower milk yield on d 3, 4, 5, 7, and 10 relative to calving in cows that received fenprostalene. Administration of fenprostalene resulted in a delay in the peak plasma nonesterified fatty acid (NEFA) concentration until 2 d after calving. Plasma glucose concentrations were greatest 1 d prior to calving for cows that received fenprostalene, whereas plasma glucose concentrations peaked on the day of calving for cows that did not receive fenprostalene. Liver triglyceride increased over time; however, there was no effect of treatment on liver triglyceride. Calving induction improved DMI for the last 8 d prepartum, but a concomitant decrease in liver triglyceride after calving did not result. Estradiol-17 beta benzoate had no effect on plasma metabolites or liver triglyceride, indicating that the physiological rise in estradiol prior to calving does not have a primary role in lipolysis or hepatic fatty acid metabolism in the dairy cow.

Differences in activity of hepatic microsomal triglyceride transfer protein among species.

Five sows, five cows, five hens, six guinea pigs, six rabbits, and six rats were used in a study to determine if hepatic microsomal triglyceride transfer protein activity differed among species that varied in site of fatty acid synthesis and rate of hepatic triglyceride export. No differences in plasma nonesterified fatty acids were seen among species. Plasma concentrations of glucose were highest in the hen, intermediate in the rat, guinea pig, and rabbit and lowest in the sow and cow. Liver triglyceride was low in all species with the only significant difference being between the hen and the guinea pig (4.7 and 1.1%, DM basis, respectively). No microsomal triglyceride transfer protein activity was found in muscle. The cow, rat, and guinea pig had the lowest levels and the hen and rabbit the highest levels of duodenal microsomal triglyceride transfer protein activity. Hepatic microsomal triglyceride transfer protein activity was significantly higher in the sow than the other species. Hepatic microsomal triglyceride transfer protein activity was 1.51, 1.63, 2.36, 2.72, 2.95, and 6.70 nmole triolein transferred/h/mg microsomal protein for the guinea pig, rabbit, cow, rat, hen, and sow, respectively. Microsomal triglyceride transfer protein activity in duodenal tissue was 18.0, 18.6, 19.2, 33.4, 113, and 161% of hepatic microsomal triglyceride transfer protein activity for the sow, cow, rat, guinea pig, hen, and rabbit, respectively. Hepatic microsomal triglyceride transfer protein activity scaled to liver weight and metabolic body size was 2.69, 3.36, 4.58, 5.83, 7.49, and 22.3 nmole triolein transferred in the liver/min/kg body weight0.75 for the rabbit, guinea pig, rat, hen, cow, and sow, respectively. There was little relationship between previously published rates for triglyceride export and hepatic microsomal triglyceride transfer protein activity measured in this experiment.

Effects of chain length and unsaturation of fatty acid mixtures infused into the abomasum of lactating dairy cows.

Six cows were utilized in a 6 x 6 Latin square design with 21-d periods to determine effects of the postruminal profile of fatty acids on dry matter (DM) intake, milk yield and composition, nutrient digestibilities, and plasma metabolites. Treatments were abomasal infusions of 1) control [168 g/d of meat solubles (carrier for fatty acids) plus 10.6 g/d of Tween 80 (emulsifier)], 2) control plus 450 g/d of mostly saturated fatty acids, 3) control plus 450 g/d of palm oil fatty acids low in linoleic acid, 4) control plus 450 g/d of palm oil fatty acids, 5) control plus 450 g/d of soybean oil fatty acids, and 6) control plus 450 g/d of soybean oil fatty acids high in palmitic acid. Treatments 2, 3, 4, and 6 contained similar ratios of C16 to C18 fatty acids. Infusion of soybean oil fatty acids or soybean oil fatty acids high in palmitic acid decreased intakes of DM, organic matter, crude protein, acid detergent fiber, neutral detergent fiber, gross energy, and total fatty acids and tended to decrease yields of milk and fat-corrected milk compared with the infusion of mostly saturated fatty acids. Infusion of palm oil fatty acids low in linoleic acid or palm oil fatty acids decreased milk fat percentage compared with other treatments. Ruminal characteristics and apparent digestibilities of DM, organic matter, crude protein, acid detergent fiber, neutral detergent fiber, energy, total fatty acids, and total C18 fatty acids were not different. Infusion of fatty acids increased concentrations of cholesterol in plasma. The amount of unsaturated fatty acids passing into the small intestine may influence responses of dairy cows to supplemental fat.

Production and composition of milk from Jersey cows administered bovine somatotropin and fed ruminally protected amino acids.

Eight multiparous and 4 primiparous Jersey cows averaging 92 d of lactation were utilized in a replicated 4 x 4 Latin square design with 28-d periods to determine responses to bovine somatotropin (bST) and ruminally protected Met and Lys when diets were fed that contained supplemental fat. Treatments were 1) control [no bST or ruminally protected amino acids (AA)], 2) control plus bST, 3) control plus ruminally protected AA, and 4) control plus bST plus ruminally protected AA. Dry matter intake was increased by bST but was unaffected by ruminally protected AA. Milk yield was increased by bST but was not altered by ruminally protected AA compared with the control diet. The bST tended to increase percentages of fat and total solids in milk and increased yields of fat, protein, 3.5% fat-corrected milk, and total solids. Ruminally protected AA increased percentages of fat, protein, and total solids in milk; however, yields of milk components were unaffected by ruminally protected AA. Body weight and body condition scores were unaffected by treatment. Concentrations of essential AA in plasma were unaffected by bST administration. Ruminally protected Met and Lys increased the concentration of Met and tended to increase the concentration of Lys in plasma. The lack of an increase in yields of milk and milk protein when ruminally protected AA were fed suggests that adequate amounts of Met and Lys were supplied by the control diet and protein reserves of the cows to meet the AA requirements for synthesis of milk and milk components.

Susceptibility patterns of bacterial isolates from intensive care and haematology/oncology patients in New Zealand.

AIMS: To determine the current susceptibility pattern of bacterial isolates from intensive care and haematology/oncology patients in New Zealand. METHOD: Over a 6 month period 417 consecutive clinically relevant bacterial isolates from intensive care and haematology/oncology patients from seven New Zealand hospitals had their susceptibility to multiple antimicrobial agents determined by the agar plate dilution method. Methicillin resistant staphylococci were not included. RESULTS: Of the 417 isolates, 224 (54%) were gram negative and 193 were gram positive. Predominant species/groups were: Escherichia coli 63 (15%), Enterobacter spp 26 (6%), other Enterobacteriacae 41 (10%), Pseudomonas aeruginosa 42 (10%), Staphylococcus aureus 111 (27%), coagulase negative staphylococci 30 (7%), Streptococcus spp 31 (7%), and Enterococcus spp 19 (5%). Isolate sources were: respiratory tract, 170 (41%); cutaneous sites, 81 (19%); blood, 64 (15%); and urine 63 (15%). Resistance was uncommon amongst staphylococci, streptococci, enterococci, and H influenzae. No vancomycin resistant or beta-lactamase-positive enterococci were encountered. For different groups of enteric gram negative bacilli: amoxycillin and amoxycillin-clavulanic acid resistance was common, 46-93% and 24-85% respectively; cefpirome was the most active cephalosporin; aminoglycoside resistance was uncommon; and no isolate possessed extended spectrum beta-lactamase. For P aeruginosa: most isolates were susceptible to cefpirome and ceftazidime, and aminoglycoside resistance was uncommon. CONCLUSION: Gram positive bacteria make up a higher proportion of isolates than in a similar European study. At present New Zealand does not have widespread resistance amongst common isolates. Several agents currently available in New Zealand provide adequate cover for commonly encountered pathogens. The choice of which agent to choose therefore rests more with their purchase and administration costs, as well as safety and efficacy data than simply susceptibility data alone.