Effect of dietary electrolyte balance on growth and acid-base status in swine

The effect of dietary electrolyte balance on pigs fed lysine- or tryptophan-adequate or tryptophan-deficient diets was investigated in four experiments using 8- to 12-wk-old pigs. Electrolyte balance, expressed as Na+K-Cl in meq/kg of diet, was varied by altering dietary levels of Na and Cl while holding all other minerals constant. In two experiments in which the basal diet contained a balance of 135 meq/kg, simple lysine or tryptophan deficiences caused depressed growth, feed intake and efficiency of feed utilization, but none of these responses was altered by dietary supplementation with NaHCO3. In one experiment in which the electrolyte balance of the basal diet was 61 meq/kg and in which both lysine and tryptophan were limiting. NaHCO3 supplementation significantly increased growth and feed intake. This did not occur if the diet was also supplemented with tryptophan. A final experiment was conducted to determine the response of pigs to a range of electrolyte balance (-85 to 341 meq/kg) in a practical corn-soy diet containing adequate levels of all amino acids. Growth and feed intake appeared to be maximal for balances of 0 to 341 meq/kg Na+K-Cl, but were decreased at -85 meq/kg (P less than .05). Acid-base balance was adversely affected at 0 meq/kg. The results suggest that the response of lysine-deficient pigs to sodium bicarbonate is dependent upon the electrolyte balance of the diet, and also is influenced by other dietary amino acids.     

夏季日粮电解质平衡值对笼养初产蛋鸭血液酸碱平衡和生产性能的调控

研究日粮电解质对夏季笼养初产蛋鸭血液酸碱平衡和生产性能的影响。试验选用17周龄体重相近的金定蛋鸭1 152只,随机分成4个处理,每个处理8个重复,每个重复36只鸭,以不同的日粮DEB值[DEB=(Na++K+-Cl-)mmol/kg]为试验处理,即DEB对照组200 mmol/kg、试验Ⅰ组250 mmol/kg、试验Ⅱ组300 mmol/kg、试验Ⅲ组350 mmol/kg,试验期42 d。结果表明:随着日粮DEB值的提高,鸭血液pH值和HCO3-的浓度显著升高(P<0.05);试验Ⅱ组的试鸭开产日龄比对照组提前约8 d;试验Ⅰ、Ⅱ组试鸭的产蛋率和产蛋量显著高于对照组(P<0.05),而料蛋比显著低于对照组(P<0.05);试验Ⅰ、Ⅱ组蛋壳强度和蛋壳厚度比对照组均有不同程度的提高,但差异不显著(P>0.05)。综合以上各项指标,夏季笼养初产蛋鸭日粮电解质平衡值以250~300 mmol/kg为宜。     

Dynamics of the acid-base balance of venous and arterial blood in clinically healthy calves]

Values of the acid base balance were examined in both venous and arterial blood of healthy calves (n = 6) of the Slovak Spotted breed aged, 3, 6, 8, 10, 12, 14, 18, and 24 weeks, respectively. Until week 4 of age the animals were fed milk only, until the age of 9 weeks a milk-roughage transition fodder and from week 10 on they were given classical herbage. Blood samples were taken from the V. jugularis and A. carotis communis or A. axillaris, respectively. The results achieved were corrected to a body temperature of 39 degrees C. During the examination period the following values were stated for both arterial and venous blood: actual acidity (pH) 7.391 +/- 0.014 and 7.362 +/- 0.013 logmolc, pCO2 6.35 +/- 0.15 and 7.35 +/- 0.11 kPa, HCO3-28.38 +/- 1.42 and 30.32 +/- 1.02 mmol. l(-1), ABE 3.57 +/- 1.44 and 4.34 +/- 1.09 mmol. l(-1); pO2 12.63 +/- 1.15 and 5.21 +/- 0.73 kPa, SAT 95.8 +/- 1.03 and 61.2 +/- 9.59%, respectively. A gradual increase in most indices of the acid base balance could be stated both in arterial and venous blood. The trends either revealed a parallel increase (HCO3-, pH) or they were more pronounced either in venous blood (SAT) or in arterial blood (ABE, pO2). Some trends were almost balanced (pCO2 and pO2 in venous blood and SAT and pCO2 in arterial blood). Thus pH, pO2 and SAT indices of the acid base balance were higher in arterial blood as compared to venous blood while pCO2, HCO3- and ABE values were higher in venous blood.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of the wing-of-the-nostrils correction procedure on the change of the acid-base balance parameters and oxygen concentration in the arterial blood in French bulldogs

Brachycephalic syndrome develops as a result of a specific build of splanchnocranium. In dogs of brachycephalic breeds, an impairment of correct gas exchange occurs. 5 French bulldogs at the age of 11-14 months, which suffered from continuous mixed-type dispnoea and lowered effort tolerance, were examined. Apart from the above-mentioned symptoms, the occurrence of strong external nostril stenosis was noted in the clinical examination. The symptoms observed together with the nostril stenosis indicated a possibility of an occurrence of the brachycephalic syndrome. 1 ml of full blood was drawn from the femoral artery. Acid-base balance parameters were determined in the arterial blood: pH, pCO2, HCO3-, and pO2. The wing-of-the-nostrils correction procedure were carried out in general anaesthesia. In premedication, the patients received medetomidine and after 15 minutes, fentanyl together with atropine. The induction of propofol was carried out. After four weeks from the procedure, blood was collected and the acid-base balance and pO2 parameters were again determined. The obtained values of the acid-base balance and pO2 parameters showed a noticeable influence of the wing-of-the-nostrils correction procedure on the values of the parameters determined. The results of the blood gasometry obtained prior to the procedure clearly indicate the occurrence of respiratory acidosis. The correction of wings of the nostrils significantly influenced saturation of the arterial blood with oxygen and the symptoms of dispnoea observed by the owners and episodes of apnoea and the loss of consciousness entirely subsided.     

The effect of arterial blood sampling sites on blood gases and acid-base balance parameters in calves.

In 21 healthy calves, 1-6 months old, the interrelationship and comparability of acid-base balance variables (pH, HCO3-, BE) and blood gases (pCO2, pO2, and sat-O2) were evaluated in arterial blood collected from a larger, centrally localised (the a. axillaris) and a smaller peripheral artery (the a. auricularis caudalis). Sampling was done by direct puncture of the vessels without local anaesthesia. Except for blood pH, significant differences were observed in the average values of pCO2, pO2, HCO3-, sat-O2 (P < 0.001), and BE (P < 0.05). Analyses of blood from the a. axillaris showed higher pH, pO2, and sat-O2 values, and lower pCO2, HCO3-, and BE values compared with that from the a. auricularis caudalis. Despite statistically significant differences between some variables, in all indices high and significant correlation relationships were recorded (R = 0.928-0.961; P < 0.001). Therefore, from the biological and clinical point of view, these differences are unimportant and the presented method of peripheral arterial blood sampling can be considered suitable for evaluating blood gases and acid-base status.     

Effects of dietary supplementation with L-carnitine and fat on blood acid-base responses to handling in slaughter weight pigs

Blood acid-base responses to handling were evaluated in slaughter weight pigs fed diets supplemented with l-carnitine and fat. The study was carried out as a randomized block design with a 2 x 2 factorial arrangement of treatments: 1) dietary L-carnitine supplementation (0 vs. 150 ppm, as-fed basis); and 2) dietary fat supplementation (0 vs. 5%, as-fed basis). Sixty pigs (91.1 +/- 5.14 kg BW) were housed in mixed-gender groups of five and had ad libitum access to test diets (0.68% true ileal digestible lysine, 3,340 kcal of ME/kg, as-fed basis) for 3 wk. At the end of the feeding period (110.3 +/- 7.52 kg BW), pigs were subjected to a standard handling procedure, which consisted of moving individual animals through a facility (12.2 m long x 0.91 m wide) for eight laps (up and down the facility), using electric prods (two times per lap). There was no interaction between dietary L-carnitine and fat supplementation for any measurement. Pigs fed 150 ppm of supplemental L-carnitine had lower baseline blood glucose (P < 0.05) and higher baseline blood lactate (P < 0.05) concentrations than the nonsupplemented pigs. After handling, pigs fed L-carnitine-supplemented diets had a higher (P < 0.05) blood pH and showed a smaller (P < 0.05) decrease in blood pH and base excess than those fed the nonsupplemental diets. Baseline plasma FFA concentrations were higher (P < 0.01) in pigs fed the 5% fat diet. After the handling procedure, blood glucose, lactate, and plasma FFA were higher (P < 0.05) in pigs fed the 5 vs. 0% fat diets, but blood pH, bicarbonate, and base excess were not affected by dietary fat. The handling procedure decreased (P < 0.01) blood pH, bicarbonate, base excess, and total carbon dioxide and increased (P < 0.01) blood lactate, partial pressure of oxygen, and glucose, and also increased (P < 0.01) rectal temperature. Free fatty acid concentrations were increased by handling in pigs fed both 0 and 5% fat and 150 ppm L-carnitine. In conclusion, dietary L-carnitine supplementation at the level and for the feeding period evaluated in the current study had a relatively small but positive effect on decreasing blood pH changes in finishing pigs submitted to handling stress; however, dietary fat supplementation had little effect on blood acid-base balance.     

Changes in blood gas and acid-base values of bovine venous blood during storage

The stability of blood gas and acid-base values in bovine venous blood samples (n = 22) stored on ice for 3, 6, 9, or 24 hours was studied. Values studied include pH, PO2 and PCO2 tensions, base excess, standard base excess, bicarbonate concentration, standard bicarbonate concentration, total carbon dioxide content, oxygen saturation, and hemoglobin. The results indicate that, except for PCO2, changes in blood gas and acid-base values during 24 hours of storage and differences between cattle of differing ages, rectal temperatures, and acid-base status were too small to be of clinical significance. Therefore, bovine venous blood samples stored up to 24 hours on ice are of diagnostic utility.     

Construction of acid-base alignment nomograms to estimate buffer base and base-excess concentrations in arterial blood from immature pigs

Acid-base characteristics of a population of immature domestic pigs were used to construct a blood acid-base alignment nomogram with scales to estimate porcine buffer base concentration. The nomogram was based on average plasma bicarbonate concentration of 31.6 mEq/L and plasma albumin and globulin values of 25.4 and 32.2 g/L, respectively. A measurement temperature of 38 C was assumed. Subsequently, this nomogram was used to construct a blood acid-base alignment nomogram with scales to estimate porcine base-excess concentration. The nomogram was based on the assignment of zero-base excess to blood with a pH of 7.50 and a PCO2 of 40 mm of Hg. Construction details, including tabular data reflecting the acid-base characteristics of porcine plasma and erythrocytes, are provided.     

Assessment of acid-base status and plasma lactate concentrations in arterial,mixed venous,and portal blood from dogs during experimental hepatic blood inflow occlusion

OBJECTIVE: To determine the effects of extended experimental hepatic blood flow occlusion (ie, portal triad clamping [PTC]) in dogs by measuring acid-base status and plasma lactate concentrations in arterial, mixed venous, and portal blood and evaluating the relationship between metabolic and concurrent hemodynamic changes. ANIMALS: 6 healthy Beagles. PROCEDURE: During anesthesia with isoflurane, cardiac output and arterial blood pressure were measured. Arterial, mixed venous, and portal blood samples were collected simultaneously for blood gas analyses and plasma lactate measurements before PTC and at 8-minute intervals thereafter. RESULTS: PTC resulted in severe hemodynamic and metabolic alterations. Eight minutes after PTC, significant decreases in cardiac index from a baseline value of 3.40 +/- 0.27 to 1.54 +/- 0.26 L/min/m2 and in mean arterial blood pressure from a baseline value of 74 +/- 6 to 43 +/- 6 mm Hg were recorded. After PTC, results indicative of lactic acidosis were found in portal blood at 16 minutes, in mixed venous at 32 minutes, and in arterial blood at 48 minutes. Significant differences in measured variables were also found between arterial and portal blood samples, between mixed venous and portal blood samples, and between arterial and mixed venous blood samples after PTC, compared with differences at baseline. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of mixed venous blood is preferable to analysis of arterial blood in the assessment of metabolic derangement. In a clinical setting, occluded portal blood is released to the systemic circulation, and the degree of reperfusion injury may depend on the metabolic status of pooled portal blood.     

The effect of propofol on acid-base balance and ionic composition of venous and arterial blood in goats

The aim of the present study was to determine the effect of propofol on acid-base balance and ionic composition of arterial and venous blood in clinically healthy goats. The experiment was performed on ten adult goats. Propofol was administered intravenously at bolus dose of 6 mg/kg bw. The heart and breath rate, acid-base balance (pH, pCO2, pO2, HCO3-, BE, O2SAT, ctCO2) and ionic composition (Na+, K+, Cl-) of arterial and venous blood were measured before injection and 3, 6 and 15 min. after. The propofol infusion induced increase of heart rate, decrease of breath rate and compensated respiratory acidosis in venous and arterial blood. It was found that changes of acid-base balance parameters in arterial blood arose faster than in venous blood. The levels of sodium and chloride ions in both types of blood were similar, whereas the level of potassium ions was higher in venous blood during entire experiment.     

Effect of feed withdrawal and dietary energy source on muscle glycolytic potential and blood acid-base responses to handling in slaughter-weight pigs

The effects of dietary energy source and feed withdrawal on muscle glycolytic potential (GP) and blood acid-base responses to handling were investigated in slaughter-weight pigs (initial BW 94.7 ± 1.01 kg). Crossbred pigs (n = 96; 48 barrows, 48 gilts) were used in a randomized complete block design with a 4 × 2 × 2 factorial arrangement of treatments: l) diet [control, high fat (10% supplemental fat), low-digestible carbohydrate (20% total starch), and high-fat/low-digestible carbohydrate (10% supplemental fat and 20% total starch)]; 2) feed withdrawal (0 and 36 h); and 3) sex (barrow and gilt). Diets were fed for 28 d before the feed withdrawal treatment was applied, at the end of which all pigs were individually moved through a 12.20-m-long × 0.91-m-wide passageway for 16 laps (195 m total distance), with the assistance of an electric goad (2 times per lap). Longissimus muscle biopsies were collected at the beginning of the feeding and feed withdrawal periods and immediately after and 4 h after the handling procedure. Venous blood was collected 2 h before and immediately after the handling procedure to measure acid-base responses. At the end of the feeding period, pigs fed the control and high-fat diets were heavier (P < 0.001) than those on the low-digestible carbohydrate and the high-fat/low-digestible carbohydrate diets (129.8, 130.9, 114.0, and 122.1 kg, respectively; SEM 1.91). Diet, feed withdrawal, and sex did not affect (P > 0.05) blood acid-base responses to handling. Muscle GP at the end of the feeding period and 4 h posthandling was least (P < 0.05) for pigs fed the high-fat diet and similar for the other 3 diet treatments. Pigs subjected to 36 h compared with 0 h of feed withdrawal had less GP (P < 0.05) immediately after and 4 h after the handling procedure. There was an interaction between diet and feed withdrawal treatments for changes in GP from the start of feed withdrawal to 4 h posthandling. The reduction in GP was greater (P < 0.05) for fasted than for fed pigs receiving the control and high-fat diets, but was similar (P > 0.05) for fasted and fed pigs receiving the 2 low-digestible carbohydrate diets. In conclusion, neither dietary energy source nor fasting affected blood acid-base responses to handling; however, fasting-induced changes in LM GP were diet dependent.     

Effects of high dietary sodium chloride content on performance and sodium and potassium balance in growing pigs

Thirty castrated male Moo Lath pigs (6–8 weeks of age) were used in a 15-week growth trial to study the effect of high dietary sodium chloride (NaCl) content on feed and water intake, performance, sodium (Na) and potassium (K) balance, and plasma aldosterone concentration. The pigs were randomly allocated (ten per treatment) to diets containing 0.24 % Na (Na0.24), 0.28 % Na (Na0.28), and 0.32 % Na (Na0.32) per kg diet. Feed and water was provided ad libitum, and water consumption, feed offered, and feed residues were recorded daily. Every third week, the pigs were weighed, blood samples were collected, and a 3-day total collection of urine and feces was performed. Water intake was higher (P?=?0.001) in pigs fed with diets Na0.28 (3.7 L/day) and Na0.32 (3.9 L/day) than in pigs fed with diet Na0.24 (3.4 L/day), and dry matter (DM) intake was higher on diet Na0.32 (P?=?0.041) than on the other diets. The average daily body weight (BW) gain was higher on diet Na0.32 than on the other diets (P?=?0.031). The feed conversion ratio (in kilogram feed DM to kilogram BW gain) was 4.6, 4.6, and 4.1 on treatments Na0.24, Na0.28, and Na0.32, respectively (P?=?0.14). The highest Na balance was observed on diet Na0.32 followed by diets Na0.28 and Na0.24 (P?<?0.001), while there was no treatment-related pattern for the K balance. The Na/K ratio in feces and urine increased (P?<?0.001), and the K/Na ratio in feces (P?<?0.001) decreased with increasing Na content in the diet. Plasma aldosterone concentration decreased (P?<?0.001) with increasing dietary content of Na. These results indicate that high NaCl intake and free access to water will increase Na balance but do not negatively influence feed intake and performance of growing local pigs.     

Effect of dietary electrolyte balance on production, immune response and mineral concentrations of the femur in broilers

The aim of this study was to assess the age-related effects of dietary electrolyte balance (DEB) on the performance, immune response (from day 0 to 42) and macromineral content of femur ash of broilers. The DEB values of the purchased commercial broiler diets were modified with the addition of NH4Cl or NaHCO3 to formulate the diets (DEB 325, 250, 175, 100, 25 and -50 mmol/kg) for this investigation. A total of 396 chickens were divided into 6 treatment groups and fed with the experimental diets for 6 weeks. During the first two weeks of life, DEB did not influence feed intake and body weight gain; however, by the 21st day of age DEB 175 and between 22 and 42 days of age DEB 250 mmol/kg gave significantly better results than the control. DEB did not affect the macromineral concentrations of bone ash. The immune response of broilers on low DEB (< 175 mmol/kg) was faster and more intensive than that of chickens on diets with medium or high DEB (> 175 mmol/kg). It can be concluded that the optimal DEB value required for the best body weight gain is significantly influenced by the age of broilers. Our results call attention to the discrepancy between the decreasing DEB level of commercial broiler diets and the age-related increase of 'electrolyte requirements' of broilers. It is also interesting that DEB may influence not only the performance but also the immune response of broilers.     

Effects of dietary electrolyte balance on the chemistry of blood and urine in lactating sows and sow litter performance

One hundred fifty-three sows (average parity of 2.2) were used to determine the effects of dietary electrolyte balance (calculated as mEq/kg of diet for Na + K - Cl) on sows and their litters during lactation. The sows were fed corn-soybean meal-based diets (1.0% lysine, 1.0% valine, 0.95% Ca, and 0.80% P; as-fed basis) starting on d 109 of gestation and throughout the 21-d lactation experiment. Dietary electrolyte balance (dEB) was 0, 100, 200, 350, and 500 mEq/kg (as-fed basis), well above and below the dEB of 185 mEq/kg found in a simple corn-soybean meal-based lactation diet. To achieve the desired dEB, diets had the following: 1) 1.8% HCl (6 N) and 1.06% CaCl2, 2) 1.0% CaCl2, 3) 0.04% NaHCO3, 4) 1.29% NaHCO3, and 5) 2.54% NaHCO3 (as-fed basis). Increasing dEB increased blood pH (linear and quadratic effects, P < 0.001), partial pressure of carbon dioxide (linear effect, P < 0.001), HCO3- concentration (linear and quadratic effects, P < 0.001), and blood base excess (linear and quadratic effects, P < 0.001). However, increased dEB resulted in lower blood concentrations of K (linear and quadratic effects, P < 0.04), Cl (linear and quadratic effects, P < 0.001), and ionized Ca (linear and quadratic effects, P < 0.001). Changing dEB did not affect ADFI; water usage, litter weight gain; sow weight change; sow backfat change; percentages of CP, lactose, and fat in the milk; percentage of sows returning to estrus; days to estrus; and number of pigs born alive in the subsequent litter (P = 0.06). However, piglet survivability to d 10 and overall was greatest with the lower dEB treatments (linear effect, P < 0.05). The pH (linear and quadratic effects, P < 0.001) and colony forming units of total bacteria (linear effect, P < 0.03) in the urine increased as dEB of the diet was increased. In conclusion, dEB had pronounced effects on the physiological status of sows and decreasing dEB below that in a simple corn-soybean meal-based diet decreased bacterial counts in the urine and increased piglet survivability. However, milk composition, sow and litter weights at weaning, and subsequent rebreeding performance of the sows were not affected by dEB.     

Changes in lymphocyte blastogenic response of mares during the perinatal period

A fluorometric assay was applied to evaluate blastogenesis of equine lymphocytes. Optimal culture conditions were as follows; concentrations of phytohaemagglutinin-P (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) were 1 microgram/ml, 40 micrograms/ml and 10 micrograms/ml, respectively, when 5 X 10(5) lymphocytes were incubated with culture medium containing 20% pooled horse serum (PHS) for 120 hours. The relative mean stimulation index of healthy non-pregnant mares were 5.107 +/- 0.323 (M +/- SE) with PHA, 4.019 +/- 0.183 with Con A and 3.610 +/- 0.131 with PWM. Sequentially the blastogenic responses of lymphocytes from twenty mares were observed during various stages of the perinatal period. Response decreased gradually before parturition was lowest at the time of parturition (PHA: 1.923 +/- 0.174, Con A: 1.698 +/- 0.206 and PWM: 1.706 +/- 0.177), and then increased gradually after parturition towards non-pregnant levels.     

Eperythrozoon infection in swine: effect on the acid-base balance and the glucose, lactate and pyruvate content of venous blood

The influence of latent and of splenectomy-induced clinically manifest Eperythrozoon suis infection on the following parameters of the carbohydrate metabolism and the acid-base status was tested in venous blood of German Landrace pigs: Levels of glucose, lactic and pyruvic acid, blood-pH, base excess, actual bicarbonate concentration, standard bicarbonate concentration, pCO2, pO2. The latent E. suis infection resulted in a consistent decrease of blood glucose level. 23 days after infection, blood glucose was reduced by 25% of the initial value. The other parameters were not changed by latent E. suis infection. Acute Eperythrozoonosis induced severe hypoglycaemia (means Gluc, = 39.7 mg/dl and blood acidosis (means pH = 7.13). In vitro experiments showed that break-down of glucose in E. suis infected blood occurs very rapidly. There was no significant reduction of the glucose concentration in control blood that had been treated accordingly. There was an increase of lactic acid (means = 62.7 mg/dl), pyruvic acid (means = 1.86 mg/dl), and pCO2 (means = 82.1 mm Hg). The concentrations of actual bicarbonate (means = 24.8 mmol/l) and standard bicarbonate (means = 20.9 mmol/l) were lowered, and there was a negative base excess (means = -3.56 mmol/l). The ratio of lactic and pyruvic acid changed from 11:1 to 30:1. It seems likely that E. suis itself is able to metabolize glucose. Acidosis is considered to result from both the increase of lactic acid (metabolic component) and an impairment of pulmonary gas exchange (respiratory component).     

Nitrogen balance during compensatory growth when changing the levels of dietary lysine from deficiency to sufficiency in growing pigs

Two experiments were conducted to elucidate the nitrogen (N) balance of pigs exhibiting compensatory growth when changing the dietary lysine levels from deficiency to sufficiency. Experiment 1 elucidated whether pigs exhibited compensatory growth with dietary lysine sufficiency. Twenty 6‐week‐old males were assigned to one of two treatments: control and LC (lysine and control). Control pigs were fed a control diet throughout the 24‐day experimental period, whereas LC pigs were fed a low lysine diet until day 21 of the experiment, followed by the control diet until the end of experiment. The dietary lysine sufficiency treatment induced an 80% increase in the growth rate of LC pigs (P < 0.05). Experiment 2 focused on the N balance of pigs that exhibited compensatory growth with dietary lysine sufficiency. Eighteen 6‐week‐old males were assigned to one of three treatments: control, LC, and LL (low lysine). LL pigs were fed a low lysine diet throughout the 24‐day experimental period. Pigs that exhibited compensatory growth with dietary lysine sufficiency tended to retain a higher amount of N than control pigs (P = 0.10). These finding suggest that the compensatory growth induced in pigs by dietary lysine sufficiency was partly attributable to a higher level of N retention.     

Interactions between dietary fatty acids and hepatic gene expression in livers of pigs during the weaning period

The aim of the present study was to evaluate the impact of dietary fatty acids (FA) during the weaning period on expression of genes involved in the oxidation and metabolism of FA (peroxisome proliferator-activated receptor (PPAR-), stearoyl-CoA-desaturase (SCD), Δ6-desaturase (D6D), acetyl CoA carboxylase (ACC) and fatty acid synthase (FAS)). Liver samples were obtained from littermates, either on day 28 of age just before weaning, or at day 56 after the 4 weeks ad lib. provision of 5% of either animal fat, fish oil or sunflower oil. In conclusion, genes involved in the regulation of FA conversion (SCD, D6D) were influenced by the n-6 to n-3 ratio, whereas the FA oxidation, as indicated by the expression of PPAR-, was highly likely regulated by the hepatic ratio between mono- and poly-unsaturated FA. Furthermore, weaning and/or age affected the hepatic expression of genes involved in FA synthesis and conversion, but not the expression of PPAR-.