Effect of pre- and postpartum supplementation with lipid-encapsulated conjugated linoleic acid on reproductive performance and the growth hormone-insulin-like growth factor-I axis in multiparous high-producing dairy cows.

The objective of the study was to evaluate the effect of prepartum and postpartum (PP) supplementation with 2 isomers of conjugated linoleic acid (CLA) on reproductive parameters and some related metabolic factors in dairy cows. High-producing, multiparous Holstein Friesian cows (n = 60) were allotted to 3 treatment groups: the CLA1 group (n = 20) was supplemented with 70 g of lipid-encapsulated CLA providing 7 g each of cis-9,trans-11 and trans-10,cis-12 CLA from d 21 (d 21) before expected calving until d 7 after artificial insemination (AI), that is, until 77 to 91 d PP; the CLA2 group (n = 20) was supplemented with the same amount of CLA beginning at calving until d 7 after AI; and the control group (n = 20) received an isocaloric, isonitrogenous, and isolipidic diet. Blood samples were taken weekly to measure glucose, insulin, insulin-like growth factor-I (IGF-I), and leptin. Liver biopsy was performed in 10 cows per group for growth hormone receptor 1A and IGF-I mRNA analyses. At d 49 to 63 PP, ovulation was synchronized with the Pre-Synch protocol followed by fixed-time AI. Milk progesterone was monitored from calving until d 35 post-AI. Cows returning to estrus following AI were inseminated. Supplementation with CLA before calving improved the recovery of plasma leptin levels in the early PP period (from the day of calving until wk 3 PP; treatment effect). Later PP (wk 5), plasma IGF-I, and leptin remained significantly higher in both CLA1 and CLA2 groups compared with control, although hepatocellular IGF-I mRNA was not different among groups. Plasma IGF-I levels remained higher in both CLA-treated groups on the day of AI. Growth hormone receptor 1A mRNA levels in hepatic tissue decreased in all groups, reaching a nadir in the first week PP. Days to first PP ovulation did not differ between groups; however, both supplemented groups conceived earlier compared with control (d 97 ± 19, d 97 ± 23, and d 113 ± 30 for CLA1, CLA2, and control, respectively). Plasma progesterone concentration was higher in both supplemented groups on d 2 to 5 following the synchronized ovulation than in controls. We concluded that CLA supplementation around calving alters PP metabolic signals as reflected by higher plasma leptin and IGF-I levels. Conjugated linoleic acid stimulated early luteal function and reduced the PP interval to conception.

Effect of pre- and post-partum supplementation with lipid-encapsulated conjugated linoleic acid on milk yield and metabolic status in multiparous high-producing dairy cows.

We evaluated the lactation performance, liver lipid content and plasma metabolites indicating the energy balance of dairy cows supplemented with conjugated linoleic acid (CLA) pre- and post-partum (PP) vs. only PP. A total of 60 cows were divided into three groups (n = 20). Daily diet of cows was supplemented with 14 g of CLA (7 g cis-9, trans-11 and 7 g trans-10, cis-12 isomers) from week 3 before the expected date of calving (group CLA1), or from the day of calving (group CLA2) until 77-91 days PP. Control cows were fed an isocaloric, isonitrogenous and isolipidic diet without CLA. Between week 3 and week 6 PP, the milk yield of cows in both CLA-treated groups was approximately 4.5 kg higher (p < 0.05) than in control. Milk fat concentrations decreased from week 3 and were lower in both CLA groups than in control (p < 0.01). Body condition score loss was lower (p < 0.05) in the CLA1 than in the control group on week 5 PP. By week 11 PP, the body condition of both CLA1 and CLA2 groups exceeded that of control. Plasma non-esterified fatty acid was lower in CLA1 compared to CLA2 and control during the early PP period (p < 0.05), while this difference faded away by the late PP period. Beta-hydroxybutyrate (BHBA) increased rapidly in all groups following calving. In CLA1 group, it began to decrease sooner than in CLA2 and control. The prevalence of subclinical ketosis (BHBA > 1.2 mm) was lower in CLA1 group than in CLA2 and control (p < 0.05). Liver biopsy analyses showed that CLA1 treatment decreased (p < 0.05) the total lipid content of liver compared to control at week 5 after calving. Our results show that CLA supplementation is more efficient in alleviating body mass mobilization and decreasing the incidence of subclinical ketosis when applied as early as 3 weeks before calving than started feeding after calving.

Composition of diet modifies colonization dynamics of Campylobacter jejuni in broiler chickens.

AIMS: To evaluate the impact of diet composition on colonization dynamics of Camp. jejuni and on related physiological parameters in the chicken intestine. METHODS AND RESULTS: A total of 54 1-day-old Ross 308 broiler chicks were randomly divided into three isocaloric and isonitrogenous dietary groups: maize-based (MB), wheat-based (WB) diet and wheat-based diet with NSP-degrading enzyme supplementation (WBES). Chickens were orally infected with 10(8)  CFU Camp. jejuni on day 14, and samples (n = 6) were collected on 7, 14 and 21 days postinfection (DPI), respectively. Colony forming units of Camp. jejuni of caecum and jejunum, short-chain fatty acid (SCFA) concentrations, pH values of the caecum, jejunal histomorphology and viscosity of jejunal chymus were measured. In case of WBES diet, lower Camp. jejuni colonization 14 DPI, higher jejunal viscosity, higher total SCFA concentrations in the caecum and enhanced jejunal histomorphology were observed compared to those measured in chickens fed MB diet. CONCLUSIONS: The WBES diet altered Camp. jejuni colonization dynamics in the chicken intestine which resulted by higher SCFA concentrations in the caecum and by the change of gut morphology. SIGNIFICANCE AND IMPACT OF THE STUDY: Our study proves that diet composition can modify Camp. jejuni colonization depending on sampling time point postinfection.

Effects of rumen-protected choline supplementation on milk production and choline supply of periparturient dairy cows.

The objective of the present study was to determine the effects of rumen-protected choline (RPC) supplementation on body condition, milk production and milk choline content during the periparturient period. Thirty-two Holstein cows were allocated into two groups (RPC group - with RPC supplementation, and control group - without RPC supplementation) 28 days before the expected calving. Cows were fed the experimental diet from 21 days before expected calving until 60 days of lactation. The daily diet of the RPC group contained 100 g of RPC from 21 days before calving until calving and 200 g RPC after calving for 60 days of lactation, which provided 25 g and 50 g per day choline, respectively. Body condition was scored on days -21, 7, 35 and 60 relative to calving. Milk production was measured at every milking; milk fat, protein and choline content were determined on days 7, 35 and 60 of lactation. Body condition was not affected by RPC supplementation. Milk yield was 4.4 kg higher for the group of cows receiving supplementary choline during the 60 days experimental period and 4% fat-corrected milk production was also increased by 2.5 kg/day. Milk fat content was not altered by treatment, but fat yield was increased by 0.10 kg/day as a consequence of higher milk yield in the RPC-treated group. Milk protein content tended to increase by RPC supplementation and a 0.18 kg/day significant improvement of protein yield was detected. Milk choline content increased in both groups after calving as the lactating period advanced. However, milk choline content and choline yield were significantly higher in the RPC group than in the control group. The improved milk choline and choline yield provide evidence that some of the applied RPC escaped ruminal degradation, was absorbed from the small intestine and improved the choline supply of the cows and contributed to the changes of production variables.

In sacco studies of conjugated linoleic acid production from various oils in the rumen of sheep.

In this experiment sunflower oil, soybean oil and fish oil were incubated in rumen-fistulated adult ewes (n = 5) to study conjugated linoleic acid (CLA) production in the rumen. The individual oils were incubated in nylon bags in the rumen on perlite carrier (40% oil, 60% carrier) over a period of 2, 4, 6, 8, 10 and 12 h for all treatments. During the incubation of each oil primarily the formation of the cis-9, trans-11 isomer of CLA could be observed. Both sunflower and soybean oils showed similar changes in the rumen. After the incubation of these two vegetable oils the proportion of linoleic acid decreased significantly as the duration of incubation increased in the rumen. These changes were accompanied by a significant increase in the amount of cis-9, trans-11 CLA. However, in the case of sunflower oil the rate of formation of the cis-9, trans-11 CLA isomer was significantly higher after the different incubation times as compared to soybean oil. Much lower amounts of CLA were formed when fish oil was incubated in the rumen. The level of cis-9, trans-11 isomer produced during these treatments was 10% less than the amount obtained with the other two oils of vegetable origin. Besides the cis-9, trans-11 isomer, trans-10, cis-12 CLA could also be detected during the incubation of the different oils in the rumen. However, the level of this isomer was low and did not show consistent differences among the treatments. The results of this experiment indicate that the fatty acid composition of the oils and the duration of incubation collectively determine the amount of CLA produced in the first compartment of the forestomach of ruminants.

Effect of supplementation with methionine and different fat sources on the glutathione redox system of growing chickens.

The effect of supplementary methionine and fats of different saturation levels on the glutathione redox system of growing broiler cockerels was studied. The diet of three groups of chicks was supplemented with corn germ oil, beef tallow and fish oil at the levels of 30 g/kg and 50 g/kg of feed, respectively. The diet of further three groups was supplemented with methionine (5 g/kg of feed) in addition to the different fat sources. Control chicks were fed with a compound feed without methionine and fat supplementation. Reduced glutathione (GSH) and glutathione disulphide (GSSG) content as well as glutathione peroxidase activity in the liver were determined and GSH/GSSG ratio was calculated at day old and then at one and three weeks of age. Our results indicate that supplementary methionine stimulates both the synthesis of the glutathione redox system and glutathione peroxidase activity in growing chickens in the first period of postnatal life, when the risk of lipid peroxidation is high due to feeding unsaturated fats in the diet.

Effects of transcutaneous electrical nerve stimulation on the fatty acid profile of rabbit longissimus dorsi muscle (preliminary report).

This study was designed to investigate whether transcutaneous electrical nerve stimulation (TENS) of the longissimus dorsi muscle (MLD) of rabbits induces specific proportional changes in the muscle fatty acid composition. Ten 4-week-old Pannon White rabbits were exposed to TENS treatment two times a day, with the following settings: 30 Hz, 20 micros impulse length, 10 mA, 2 x 20 min. After a treatment period of 50 days rabbits were slaughtered and the fatty acid composition of the MLD was determined by gas chromatography. The TENS treatment increased the proportions of linoleic (C18:2 n-6), linolenic (C18:3 n-3) and gondoic acids (C20:1 n-9), compared with the control group. The level of palmitic (C16:0), stearic (C18:0), oleic (C18:1 n-9) and eicosapentaenoic (C20:5 n-3) acids significantly decreased. The proportion of total unsaturated fatty acids significantly increased. On the basis of the results obtained, TENS may have similar effects on the muscle fatty acid profile like physical training. Based on the supposal that the composition of membrane structure was also affected, the electrical stimulation of muscles may have further consequences, e.g. on membrane properties.

Fatty acid composition of intramuscular lipids in various muscles of Holstein-Friesian bulls slaughtered at different ages.

Holstein-Friesian bulls were slaughtered at 7, 14 and 19 months of age. Samples were collected from the psoas major, longissimus and semitendinosus muscles. The total lipids (TL) of the samples were extracted and the fatty acid compositions were analysed by gas chromatography. Both the slaughtering age and the type of muscles had significant effects on the intramuscular TL contents and fatty acid compositions. The longissimus muscle had higher intramuscular TL both at 14 and 19 months than at 7 months of age. As the bulls became older the proportion of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) increased in the TL of each muscle tested, whereas that of polyunsaturated fatty acids (PUFA) decreased. Among the muscle types, the semitendinosus had the lowest, intramuscular TL at each slaughtering age and the psoas major the highest. Except for SFA at 7 months of age, the semitendinosus showed lower levels of SFA and MUFA and higher proportions of PUFA than the other two muscles.

Effects of glucagon and insulin on plasma glucose, triglyceride, and triglyceride-rich lipoprotein concentrations in laying hens fed diets containing different types of fats.

The influence of dietary fat supplementations differing in the ratio of n-6 to n-3 polyunsaturated fatty acids (PUFA) on the effects of glucagon and insulin on plasma glucose, triglyceride (TG), and TG-rich lipoprotein concentrations was investigated in laying hens. Birds were fed either a low-fat control diet (LF) or diets supplemented with 4% pumpkin seed oil (PO; rich in n-6 PUFA) or 4% cod liver oil (CO; rich in n-3 PUFA). After 4 wk feeding of the experimental diets, hens were implanted with wing vein catheters and injected with porcine glucagon (20 microg/kg BW) and porcine insulin (0.5 IU/kg BW), 2 to 5 h after oviposition. Plasma glucose, TG, and TG-rich lipoprotein concentrations were determined from 10 min pre-injection to 60 min post-injection. PO diet resulted in a prolonged plasma glucose response to glucagon administration and altered hypoglycemic response to insulin. However, CO diet did not influence plasma glucose response to either glucagon or insulin administration compared to LF diet. The effects of glucagon and insulin on plasma TG and TG-rich lipoproteins were similar for all diets regardless of the amount or type of fat. The results suggest that feeding dietary fats with high n-6 to n-3 PUFA ratio alters the glucagon and insulin sensitivity of plasma glucose in laying hens. Fats rich in n-3 PUFA seem to have no influence on the plasma glucose response to glucagon and insulin.

Effect of different fat sources on in vitro degradation of nutrients and certain blood parameters in sheep.

This study was designed to determine the effects of calcium salt of palm oil fatty acids (CS), hydroxyethylsoyamide (HESA), butylsoyamide (BSA) and soybean oil (SO) on degradation of crude protein and fibre in vitro, and on the blood plasma lipid parameters in vivo. Five mature wethers (body weight 75 kg) were fed five diets in a 5 x 5 Latin square experiment. The control diet consisted of 50% meadow hay and 50% concentrate with no added fat. The control diet was supplemented with CS, HESA, BSA, or SO. Fat was added at 3.5% of dietary dry matter (DM). The final ether extract content of the ration was near 6%. Each period lasted 20 days. Fat supplements, except HESA, consistently decreased the in vitro DM disappearance of soybean meal as compared to control. In contrast to the effect of other treatments, crude protein degradation was greatest in the test tubes with inocula obtained from sheep fed diet with HESA. Fat supplements equally inhibited the DM and fibre breakdown of alfalfa pellet. CS and HESA seemed to be less detrimental to in vitro fermentation of neutral detergent fibre (NDF) than BSA and SO. All fat supplements increased blood plasma triglyceride, cholesterol and total lipid content. Plasma concentration of cholesterol and total lipid was highest with SO. The inclusion of CS in the diet increased 16:0, while all fat supplements increased plasma 18:0 and decreased 16:1 and 18:1 fatty acid content. Plasma 18:2n-6 was not changed by feeding CS and SO. However, compared to the control diet, 18:2n-6 increased with 12 and 41% in plasma fatty acids when sheep were fed HESA and BSA, respectively. The results showed that plasma concentration of linoleic acid was enhanced more when the amide was synthesised from butylamine than when from ethanolamine.

Rate of lipid peroxidation in brain and liver tissues and the total antioxidant status of blood plasma in developing chicks.

Age-related changes of tissue lipid peroxidation (LPO) of liver and brain, as well as plasma antioxidant capacity of broiler chicken cockerels were investigated. Tissue LPO was characterised by the spectrophotometric assessment of thiobarbituric acid reactive substances (TBARS). Plasma antioxidant power was evaluated by the measurement of total antioxidant status (TAS). Newly hatched broiler chicks had similar TAS value (1.19 mmol/l) as newborns of mammalian species. Significant changes (p < 0.05) were observed in the time course of all parameters. Tissue TBARS concentration was higher in the brain than in the liver at hatching, while the latter organ was found to have more effective antioxidant defence during embryonic life. The concentration of TBARS increased up to the 10th day in the liver but only up to the 21st day in the brain, and the former was accompanied by an approximately 50% decrease of plasma antioxidant capacity. This suggests that the liver plays an important role in forming the antioxidant defence mechanisms of the blood plasma in broiler chicks.

Liver total lipids and fatty acid composition of shot red and fallow deer males in various reproduction periods.

In this study total lipid (TL) content and the fatty acid composition changes in the liver of red deer stags (n=35) and fallow deer bucks (n=19) were examined at various reproductive stages. Samples were taken from mature red deer stags in the rut (September), in the post-rut (October), at the end of the rut (November) and after sexual activity had ceased (January). Sampling from mature fallow bucks was performed in the pre-rut (early October), in the rut (November) and after the reproduction period (January). The results obtained indicated significant (P<0.001) fatty degeneration of the liver in the males at the rutting season. At that time the TL concentration (x+/-S.D. in wet weight) was 156+/-40 g/kg in the red deer stags and 405+/-46 g/kg in the fallow bucks. Subsequent to the rutting season this value decreased to 47+/-15 g/kg by November in the red deer stags and to 51+/-3 g/kg by January in the fallow bucks. Significant changes were also observed in the fatty acid composition of the liver lipids, determined by gas chromatography. Liver samples collected during the rutting season from both red deer stags and fallow bucks showed higher (P<0.001) total proportions of monounsaturated fatty acids and lower (P<0.001) weight percentages of polyunsaturated fatty acids than those taken in January. In comparison with January the liver samples taken in September from red deer stags showed significantly higher (P<0.001) proportions of fatty acids C14:0, C15:0 and C:16:1, and significantly lower (P<0. 001) proportions of C18:0, C20:4 (n-6) and C22:5 (n-3). The proportions of C14:0, C15:1, C17:1 and C18:3 (n-3) in the liver samples taken in November from fallow bucks were higher (P<0.001), while the proportions of C18:0 and C20:4 (n-6) were lower (P<0.001) than those measured prior to rutting (in October) or after the rut (in January).

Effects of saturated and unsaturated fats with vitamin E supplementation on the antioxidant status of broiler chicken tissues.

The influence of fish oil (highly unsaturated) and beef tallow (highly saturated) with vitamin E (100 IU/kg) supplementation on the antioxidant status of broiler chicken cockerels was investigated. Chicks were fed a control diet with no added fat, 40 g/kg each of fish oil and beef tallow diets, respectively, from 11 to 42 days of age. Tocopherol concentration and the rate of lipid peroxidation, thiobarbituric acid reactive substance (TBARS) in liver, fatty acid composition of the liver lipids, blood serum total antioxidant status (TAS), and reduced glutathione (GSH) content were determined. Vitamin E supplementation of the diet increased liver alpha-tocopherol content in chicks regardless of the type of dietary fat. Fish oil diet resulted in higher liver TBARS value while beef tallow diet showed lower values compared to the control diet. Vitamin E supplementation reduced liver TBARS as well as serum GSH, and raised serum TAS for all diets. Serum GSH was the same for vitamin E supplemented diets regardless of the fat supplement. Fish oil diets resulted in a significant increase in hepatic lipid n-3 PUFA content. A significant positive correlation was found between liver TBARS and n-3 PUFA content. No relationships were established, however, between liver TBARS and n-6 PUFA or saturated fatty acids. The results suggest that feeding oils rich in n-3 PUFA increases tissue concentration of these fatty acids, consequently increasing tissue lipid peroxidation and reducing the antioxidative status of broiler chickens. Supplementing high levels of vitamin E with such oils may increase tissue oxidative stability. Serum TAS or GSH may be used as a measure of antioxidative status in chickens.

Effects of different hybrids, strains and age of laying hens on the cholesterol content of the table egg.

Three experiments were carried out to investigate the effects of age, moulting and strain of hens on the weight, total cholesterol content (TCh) and cholesterol concentration (CCh) of egg yolk. Only slight differences were found in the TCh and CCh of eggs between white and brown egg layer hybrids (Shaver SC 288 vs. Shaver SC 579) of the same age. On the other hand, significant differences (p < 0.05) were found in yolk CCh and TCh of both hybrids during the production period. The change in yolk CCh was periodical: it decreased in both hybrids until 45 weeks of age, then it increased, reaching a plateau between weeks 51 and 54, and declined again at the end of production. TCh, however, increased until 51 (Shaver SC 579) or 54 (Shaver SC 288) weeks of age, which could be attributed to the steady increase in yolk weight throughout the production period. In the eggs of Tetra-SL hens yolk weight, yolk CCh and TCh were slightly higher after moulting (at 108 weeks of age) than in the first production period (at 48 weeks of age), but the differences were not significant (p > 0.05). Significant inter-strain differences (p < 0.05) were found, however, in the yolk parameters measured. The highest values were found in the eggs of New Hampshire hens, as compared to the traditional Hungarian breeds. The eggs of traditional pure-bred hens contained a substantially higher amount of cholesterol than those produced by the hybrids.

Weight-length relationships and reproduction of bream (Abramis brama L.) in Keszthely Bay of Lake Balaton.

The weight-length relationships of bream (Abramis brama L. 1758, family Cyprinidae) were studied in Lake Balaton, Hungary, Fish were randomly collected with a gill net from Keszthely bay between March and November 1995. The condition of bream was investigated monthly, using morphometric parameters of the body, fecundity estimations, and gonadosomatic indices (GSI). The weight-length relationships show that the body weight of bream increased at an approximately 3.4 times higher rate than its length (b = 3.41). The GSI of females were always higher than those of the males. The GSI values of females reached their maximum (14.76-22.22) from March to May. Egg diameter is positively correlated with the spawning months, as demonstrated by the relationship found between egg diameter and GSI (r = 0.94; P < 0.001) Fecundity estimates exhibited a linear relationship to length and weight.

Infusion of various short chain fatty acids causes different changes in the blood glucose and insulin concentrations in growing lambs deprived of food overnight.

Glucose and insulin concentrations of jugular blood plasma were monitored in growing lambs over 8 h, following a 2 h infusion of acetate, propionate, n-butyrate, n-valerate and physiological saline into the ruminal vein. Propionate and especially n-valerate infusion significantly increased blood glucose concentration. n-Butyrate induced only a small increase of shorter duration, while acetate failed to exert a pronounced effect on the blood glucose level. SCFA infusion, except for acetate, raised the insulin level in the blood. Relative rise was closely correlated with the length of carbon chain of the SCFA, that is, n-valerate caused the largest elevation of the insulin level, followed by n-butyrate and propionate. At the same time, acetate failed to cause a marked influence on the insulin level. These results of insulin showed agreement with glucose concentration changes, with the exception of n-butyrate treatment, where the increase of plasma insulin concentrations after the infusion proved to be much larger than that of glucose, relative to the preinfusion value.

Influence of a deficient intake of high and low degradable protein on body composition, metabolic adaptation, production and reproductive performance in early lactation dairy cows.

High-yielding dairy cows (n = 34) were divided into high (HD) and low (LD) protein degradability groups after delivery, and used for a feeding trial which lasted up to day 80 +/- 10 of lactation. The cows were regularly weighed, their body condition was scored (BCS), and their reproductive status assessed. Blood samples were taken simultaneously, and ruminal fluid was collected on the last day of the trial. On postpartum day 45 +/- 6 and 11 days thereafter two prostaglandin F2 alpha (PGF2 alpha) injections were administered. The ammonia and urea concentrations of the ruminal fluid were higher in cows of group HD. The C2:C3 ratio was 2.7:1 vs. 2.3:1 in HD and LD cows, respectively. The amino acid and lipid composition of blood reflected the dietary treatments. The BCS and blood urea concentration were slightly higher in HD animals. The average daily milk production of LD cows was 1.5 kg higher than that of HD cows. The pregnancy rates of the two groups at day 200 after calving did not differ, but LD cows showed their first visible oestrus and reconceived significantly (p < 0.05) later. It can be concluded that--at a marginal energy supply-a moderate (13%) deficiency of rumen-degradable protein during the first 10 weeks after calving can be more detrimental to reproductive performance than a severe (27%) deficiency of undegradable protein.

Feeding animal fats to sheep.

In an experiment lasting 7 weeks, 18% of the calculated energy requirement of 5 nonpregnant ewes was met by giving natural fats of animal origin mixed in the ration (at a level of 6.6%). Changes in certain blood and blood plasma parameters of lipid and energy metabolism were monitored at 5 time-points during the experiment. Samples of rumen fluid were taken three times for determining the concentrations of volatile fatty acids (VFA). Rumen fermentation was studied by in sacco method. Total lipid (TL) content of the liver and fatty acid composition of the liver tissue and subcutaneous adipose tissue (from the tailhead) were analyzed at the beginning and at the end of the experiment. At the concentration used in this experiment, fat supplementation caused neither digestive disturbances nor any other adverse changes in the animals' health status. It did, however, exert a significant influence on blood plasma lipid composition. TL and total cholesterol (TCh) concentration increased and blood glucose level decreased. A rise in triglyceride (TG) content was accompanied by a drop in free fatty acid (FFA) concentration. The in sacco experiments and volatile fatty acid (VFA) levels in the rumen fluid suggested an impaired crude fibre digestion in the rumen. At the same time, fat supplementation enhanced rumen proteolysis. The TL content of liver samples did not exceed the physiological limit. The liver biopsy samples had decreased myristic acid and increased stearic and oleic acid concentrations. No change occurred in the fatty acid composition of the fat depots.

Effect of volatile fatty acid infusion on blood plasma free amino acid profiles in growing lambs.

Five ram lambs (average body mass: 25 kg) were given, through a catheter inserted into the left ruminal vein, a total of 28.8 mM sodium acetate, 14.4 mM sodium propionate and 4.8 mM sodium butyrate per kg body mass as a 2-hour infusion. During and at 0, 1, 2, 4, 6, 10 and 24 h after the infusion blood samples were taken from the jugular vein and the blood plasma was assayed for free amino acid (FAA) and immunoreactive insulin (IRI) concentrations. Volatile fatty acid (VFA) infusion significantly decreased the blood plasma concentrations of all FAA but cystine. The lowest FAA concentrations were measured in plasma samples taken at the end of the 2-h infusion. Subsequently the level of all amino acids rose and by 24 h after the infusion the blood plasma concentration of all FAA came close to the preinfusion value. The largest differences were observed in the concentration of glutamate, glycine, leucine and isoleucine. In contrast to FAA, IRI concentration was increased significantly (almost fivefold) by VFA infusion. By 10 h after the infusion IRI concentration returned to the initial level. The results reported here indicate that energy supply given in the form of VFA infusion significantly affects blood plasma FAA profiles, supposedly as a result of changes induced in protein synthesis in tissues. Insulin presumably plays a role in the regulation of these changes.

The effect of feed intake and portal volatile fatty acid infusion on insulin and free amino acid concentrations in plasma of lambs.

Experiments were conducted with chronically catheterized growing lambs to study the effect of variations in rumen volatile fatty acid (VFA) supply on blood plasma free amino acids (FAA) and insulin. Five male lambs were fed, then fasted for 72 h and refed. In the second experiment 48 mmol of a VFA mixture per kg body weight was infused into the rumen vein of another 5 lambs. Rumen VFA, plasma FAA and immunoreactive insulin (IRI) concentrations were determined over the 72 h postfeeding period and during 24 h after refeeding as well as over 24 h after the VFA infusion. Both postprandial increase of rumen VFA and VFA infusion caused a significant increase of plasma FAA concentrations and an increase in IRI. Feed intake decreased the prefeeding total FAA (TFAA) concentration (2.7 mmol/l) to 1.8 mmol/l at 4 h after feeding. It rose again to 2.5 mmol/l at 24 to 72 h postfeeding. IRI seemed to have the highest concentrations when the TFAA were the lowest. VFA infusion also decreased the plasma TFAA, to about half of the preinfusional value. IRI, however, showed a five-fold increase after infusion. The results of these experiments show that variations in VFA absorption from the rumen due to different nutritional stages result in changes of the plasma FAA concentrations. Insulin seems to have an important role in the control of these changes.