Effects of birth weight and dietary fat on intake,body composition,and plasma thyroxine in neonatal lambs

Intrauterine growth restriction (IUGR) is often observed in one of the fetuses carried by well-fed prolific ewes. This condition is the result of an insufficient placental size to cover the nutritional needs of the fetus during the near exponential growth phase of the last trimester. After birth, these IUGR offspring have an elevated appetite and lower maintenance energy requirements, suggesting dysregulation of homeostatic systems governing energy metabolism. It is also unknown whether the consequent increase in fatness occurs similarly in both visceral and carcass fractions. To address these questions, lambs differing in birth size (BS, IUGR vs. Normal, 2.6 ± 0.05 vs. 4.2 ± 0.07 kg, P < 0.001) were offered unlimited amounts of a low fat [LF; 22% of dry matter (DM)] or a high fat (HF; 38% of DM) milk replacer and slaughtered on day 14 of postnatal age (n = 7 to 8 for each BS × Diet); a second group of IUGR lambs (n = 3 for each diet) was slaughtered when they reached 8.5 kg, corresponding to the weight of Normal lambs on day 14. When normalized to body weight (BW), the DM and energy intake of IUGR lambs were higher than those of Normal lambs over the first 14 d of life (BS, P < 0.01), but contrary to expectations, the HF diet did not exacerbate these effects of the IUGR condition. Intrauterine growth restricted lambs had increased viscera fat with both diets (BS and Diet, P < 0.05) but increased carcass fat only with the LF diet (BS × Diet, P = 0.08); the fatness promoting effect of the IUGR condition was increased in both body fractions when lamb groups were compared at the fixed BW of 8.5 kg. A subset of metabolic hormones was analyzed, including the metabolic rate-setting hormone thyroxine (T4) and its possible positive regulator leptin. Plasma T4 was lower in IUGR than in Normal lambs at birth (P < 0.05) but then disappeared by day 7 of postnatal life (BS × Day, P < 0.01). On the other hand, the HF diet had no effect on plasma T4 over the first 3 d but caused an increase, irrespective of BS by day 11 (Diet × Day, P < 0.001). Plasma leptin increased with dietary fat and time (P < 0.06) but bore no relation to the effects of BS or Diet on plasma T4. These data show that IUGR and Normal lambs are similarly unable to adjust caloric intake in early life and that the fatness promoting effects of the IUGR condition are more pronounced in the viscera than in the carcass. These data also reveal dynamic regulation of plasma T4 by BS and Diet in neonatal lambs.     

Influence of dietary protein level on body composition and energy expenditure in calorically restricted overweight cats

High‐protein (HP) diets help prevent loss of lean mass in calorie‐restricted (CR) cats. However, it is not entirely known whether these diets also induce changes of energy expenditure during periods of CR. To investigate this issue, sixteen overweight cats were fed either a high‐protein [(HP), 54.2% of metabolizable energy (ME)] or a moderate‐protein [(MP), 31.5% of ME] diet at 70% of their maintenance energy intakes for 8 weeks, and energy expenditure, energy intake, body weight and composition, and serum metabolites and hormones were measured. While both groups of cats lost weight at a similar rate, only cats eating the HP diet maintained lean mass during weight loss. Indirect respiration calorimetry measurements revealed that both total and resting energy expenditure (kcal/d) significantly decreased during weight loss for both treatment groups. However, only cats eating the MP diet exhibited significant decreases of total and resting energy expenditures after energy expenditure was normalized for body weight or lean mass. Results from this study suggest that in addition to sparing the loss of lean mass, feeding HP diets to overweight cats in restricted amounts may be beneficial for preventing or minimizing decreases of mass‐adjusted energy expenditure during weight loss.     

Effects of energy intake and body weight on physical and chemical body composition in growing entire male pigs

Two experiments were conducted to determine independent effects of BW and DE intake on body composition and the partitioning of retained body energy between lipid and protein in pigs with high lean tissue growth potentials and when energy intake limited whole-body protein deposition. In a preliminary N-balance experiment involving 20 entire male pigs at either 30 or 100 kg BW, it was established that whole-body protein deposition increased linearly (P < 0.05) with DE intake at both BW. These results indicate that DE intake controlled whole-body protein deposition and that these pigs did not achieve their maximum whole-body protein deposition when fed semi-ad libitum. In the main serial slaughter experiment, 56 pigs, with a BW of 15 kg, were assigned to one of four DE intake schemes and slaughtered at 40, 65, 90, or 115 kg BW. Within DE intake schemes, DE intake was increased linearly (P < 0.05) with BW, allowing for an assessment of effects of DE intake and slaughter BW on chemical and physical body composition (carcass, viscera, blood). Between 15 and 90 kg BW, average DE intake of 16.1, 20.9, 25.2, and 28.8 MJ/d supported average BW gains of 502, 731, 899, and 951 g/d, respectively. The proportion of whole-body protein present in the carcass increased with BW and decreased with DE intake (P < 0.05), whereas the distribution of whole-body lipid between carcass and viscera was not influenced by BW and DE intake. A mathematical relationship was developed to determine the relationship between DE intake at slaughter (MJ/d) and chemical body composition in these pigs: whole-body lipid-to-protein ratio = 1.236 - 0.056 x (DE intake) + 0.0013 x (DE intake)2, r2 = 0.71. The data suggests that absolute DE intake alone was an adequate predictor of chemical body composition in this population of entire male pigs over the BW and DE intake ranges that were evaluated, simplifying the characterization of this aspect of nutrition partitioning for growth in different pig populations.     

Effects of dietary protein concentration and specific amino acids on body weight,body composition and feather growth in young turkeys

1. Two randomised block factorial experiments were conducted to investigate the relationships between the effects of dietary crude protein and specific amino acid concentrations on the relative growth of the body and feathers of young turkeys. 2. Decreasing dietary crude protein concentration from 300 to 180 g/kg in experiment 1 reduced the body and breast muscle weights of a large male line of turkeys proportionally by 0.44 and 0.52 compared with 0.19 and 0.24 in a small traditional line. 3. Decreasing dietary crude protein concentration was associated with a maximum reduction in feather weight of 0.18 and 0.24 respectively in male line and traditional turkeys. The length of the feathers in the cranial region of the breast decreased from 26 to 19mm in the traditional line compared with an increase from 14 to 25 mm in male line turkeys. 4. Decreasing dietary crude protein concentration was associated with an increase in the fat content of the feather-free carcase. Male line turkeys had a higher carcase fat and lower feather dry matter content than the traditional turkeys. 5. It was concluded that dietary crude protein was preferentially partitioned to feather rather than muscle growth in the male line in contrast to a traditional line of turkeys in which the growth of feathers and muscle were affected equally. 6. In experiment 2, the amino acids arginine, valine, methionine and tyrosine were added separately to a common basal ration (180g CP/kg) to raise their concentration to that of the control ration (260 g CP/kg). Each ration was fed ad libitum to male line turkeys from 2 to 6 weeks of age. 7. Amino acid supplementation increased body and breast muscle weights. 8. Compared with the basal ration, tyrosine was associated with a reduction in feather weight whereas valine had no effect. Supplementation with arginine and methionine resulted in increased feather weights that were similar to that of the controls. 9. It was concluded that arginine and methionine were used preferentially and are essential for feather growth. Excess amino acids that are not required for feather growth such as tyrosine and valine were used for increased body growth and resulted in relatively poor feather cover. 10. The results suggest that feather growth was maintained as much as possible at the expense of body growth when the amino acid concentration of the ration was less than that required to maximise body and muscle weight gain in large male line turkeys.     

Effects of dietary fat and triamcinolone additions during late gestation on the body energy reserves of neonatal pigs

Two trials involving 21 primiparous sows were conducted to evaluate the effects of fat and triamcinolone additions to the diet of late-term, gravid sows on carbohydrate, protein and fat reserves in nursed and fasted neonatal pigs. Beginning 7 d prepartum, sows were fed daily 1.8 kg (6 Mcal metabolizable energy, ME) of a fortified, corn-soybean meal diet that was supplemented with 4 Mcal ME/sow in the form of starch, soybean oil or soybean oil plus 70 mg/sow of triamcinolone, a synthetic glucocorticoid. After parturition, the sows were fed daily 5 kg (15 Mcal ME) of a 14% protein, corn-soybean meal diet. The addition of soybean oil to the diet of sows during late gestation did not influence (P greater than .1) liver glycogen content, serum glucose levels or carcass protein and fat reserves in nursed or fasted pigs from birth to 6, 12, 24 or 48 h of age. The addition of triamcinolone to the sows' prepartum diet increased (P less than .1) fat deposition in the nursed pigs from birth to 48 h of age. Liver glycogen reached minimal levels by 24 h postpartum in both nursed and fasted pigs, regardless of the sows' prepartum treatment. Serum glucose levels were maintained at 80 to 130 mg/dl in the nursed pigs from birth to 48 h of age, but approached hypoglycemic levels (50 mg/dl) by 24 h in the fasted pigs. Nursed pigs deposited 28 g of body protein and 15 g of fat from birth to 48 h of age; whereas, fasted pigs mobilized only minimal quantities (3 g) of body protein and fat.     

The relationships among body weight, body composition, and intramuscular fat content in steers

Angus steers of known age (265 +/- 17 d) and parentage were used in a 2-yr study (yr 1, n = 40; yr 2, n = 45) to evaluate the relationship between percentage of i.m. fat content of the longissimus dorsi at the 12th rib and carcass characteristics during growth of nonimplanted steers. Steers were sorted by age and EPD of paternal grandsire for marbling into high- and low-marbling groups so that steers with varying degrees of genetic potential for marbling were evenly distributed across slaughter groups. All steers were fed a 90% concentrate corn-based diet. Steers were allotted to five slaughter groups targeted to achieve hot carcass weights (HCW) of 204, 250, 295, 340, and 386 kg over the course of the feeding period. Data were analyzed as a completely random design with a factorial arrangement of treatments (year, marbling group, and slaughter group). Marbling group did not affect backfat, LM area, yield grade (YG), or marbling score. Regression equations were developed to quantify the change in carcass characteristics and composition over slaughter groups. Hot carcass weight increased in a linear fashion and differed (P < 0.01) among the slaughter groups as anticipated by design. Yield grade followed a quadratic upward pattern (P < 0.01) as HCW increased. Slaughter group affected the degree of marbling linearly (P < 0.01). There were no slaughter group x marbling group interactions, indicating that no differences occurred in the pattern of marbling attributable to paternal grandsire EPD. Carcasses expressed small degrees of marbling at 266 kg of HCW and obtained a YG of 3.0 at 291 kg of HCW. Fractional growth rates decelerated with increasing HCW. Greater advances in marbling relative to total carcass fatness occurred at HCW less than 300 kg. Management practices early in growth may influence final quality grade if compensatory i.m. fat content development does not occur.     

Effects of lighting regimen and grower diet energy concentration on energy expenditure,fat deposition and body weight gain of laying hens

1. Mean metabolisable energy (ME) intakes and heat productions over a laying year were calculated for laying hens which had been submitted to one of various lighting regimens and given either a normal or a high energy ration during the rearing period.

2. Daily ME intake and heat production per hen in the laying period were unaffected by either lighting regimen or grower diet. ME intake per kg W ^0.75 and heat production per kg W ^0.75 during lay increased significantly with laying photoperiod, was non‐significantly higher following an 8‐h rather than an 11‐h rearing photoperiod, but was unaffected by dietary energy concentration. The increase in heat production (/kgW°‘⁷⁵) associated with a 1‐h increment in photoperiod was similar to predictions made from calorimetric measurements of diurnal variation.

3. Efficiency of conversion of food to egg was unaffected by either lighting regimen or dietary energy concentration.

4. Fat weight gain in lay was not influenced by lighting regimen, but was significantly lower in birds reared on the high, compared to the normal, energy grower ration. Fat‐free weight gain in lay was unaffected by grower diet, but was significantly increased by photoperiods longer than 8 h.

5. ME intake and heat production per kgW^⁰⁷⁵ were negatively correlated with age at first egg, but ME intake and heat production per bird d were not related to age at sexual maturity.     

Resting energy expenditure and body composition of Labrador Retrievers fed high fat and low fat diets

A high dietary fat intake may be an important environmental factor leading to obesity in some animals. The mechanism could be either an increase in caloric intake and/or a decrease in energy expenditure. To test the hypothesis that high fat diets result in decreased resting energy expenditure (REE), we measured REE using indirect calorimetry in 10-adult intact male Labrador Retrievers, eating weight-maintenance high-fat (HF, 41% energy, average daily intake: 8018 +/- 1247 kJ/day, mean +/- SD) and low-fat (LF, 14% energy, average daily intake: 7331 +/- 771 kJ/day) diets for a 30-day period. At the end of each dietary treatment, body composition measurements were performed using dual-energy X-ray absorptiometry. The mean +/- SD REE was not different between diets (4940 +/- 361 vs. 4861 +/- 413 kJ/day on HF and LF diets respectively). Measurements of fat-free mass (FFM) and fat mass (FM) also did not differ between diets (FFM: 26.8 +/- 2.3 kg vs. 26.3 +/- 2.5 kg; FM: 3.0 +/- 2.3 vs. 3.1 +/- 1.5 kg on HF and LF diets respectively). In summary, using a whole body calorimeter, we found no evidence of a decrease in REE or a change in body composition on a HF diet compared with LF diet.     

Effect of dietary fatty acid pattern on growth, body fat composition and antioxidant parameters in broilers

The effects of dietary fat supplementation on performance, fatty acid (FA) composition of tissues and antioxidant defence system of broilers were studied. Male broilers were placed in 20 floor pens (60 broilers per pen). The broilers were fed by diets with added different energy sources: lard (L); sunflower oil (SFO); soybean oil (SBO); and linseed oil (LSO). The treatments did not modify significantly growth performance and feed intake of the broilers. There was no effect of dietary FA pattern on reduced glutathione level and glutathione peroxidase activity of plasma, erythrocyte and liver samples. However, higher PUFA content of the diet resulted in a significant increase in malondialdehyde level of erythrocytes and liver. The broilers fed LSO diet more effectively maintained their antioxidant status with enhanced plasma radical scavenger capacity. FA composition in tissues reflected the FA pattern of the diets, although proportion of FAs with four or more double bonds was metabolic specific. LSO diet increased the level of C18:3, C20:5 and C22:6 in tissue lipids in relation to L, SFO and SBO diets. Significantly increased plasma radical scavenging capacity in concert with the enhanced C20:5 and C22:6 proportion in liver and muscle during LSO feeding indicate metabolic changes to counteract the oxidative injury. This may be related to the compounds produced after different biochemical pathways of n-6 and n-3 FAs.     

Effects of dietary energy concentration on utilisation of energy by broiler chickens and on body composition determined by carcass analysis and predicted using tritium

Groups of 10 male, 10 female and 10 unsexed broiler chickens were given eight diets with energy concentrations ranging from 2.3 to 3.6 Mcal ME/kg in two experiments. Diets with a metabolisable energy concentration of about 3.1 Mcal/kg were found to be optimal for growth to a specified live‐weight. Carcass analysis gave much smaller values for nitrogen retention than did estimates from food intake and excreta. Retention measured by the latter method was influenced by the energy concentration of the diets.

Body composition was influenced by both dietary energy concentration and sex. In general, the energy and fat content of the carcass increased with increasing dietary energy concentration although there were overall differences in fat content between male and female chickens, and also between birds in experiment 1 and experiment 2.

Tritiated water was used to predict body water space enabling body composition to be estimated. Comparisons between determined body water content and tritiated water space showed that the former was overestimated, on average, by 18%. Residual standard deviation of prediction equations based on 240 chickens was 52.6 g for water space, 21.4 g for protein and 34.6 g for fat.     

Male and female cats have different regional body compositions and energy requirements for weight loss and weight maintenance

Body composition and energy requirements are different between males and females in several species, and both interfere with weight loss. The aim of this study was to compare the total and regional body composition and energy requirements in obese male (n = 8) and female (n = 8) cats, during weight loss and weight maintenance over 17 subsequent weeks after regimen. The total and regional (thoracic and pelvic limbs, and trunk) body composition was assessed by dual‐energy X‐ray absorptiometry (DXA). Females exhibited a higher fat mass (FM) than males (p < 0.05), and the trunk was the site with greater fat accumulation regardless of gender. A 23.0 ± 2.8% reduction in body weight was followed by a 50.3 ± 9.4% and a 37.0 ± 8.9% reduction in fat in the trunk region in males and females respectively. Lean mass (LM) mobilization was also increased in the trunk (p < 0.05), and the loss of LM was associated with a reduction in bone mass. The energy intake to achieve the same rate of weight loss was 12.9 ± 3.4% higher in males (p < 0.05). The cats exhibited a gradual increase in energy requirements to maintain their body weight after weight loss (p < 0.05). It was concluded that obese cats mainly accumulate fat in the trunk. The reduction in lean mass after the regimen also occurred in the trunk, with no modifications in the skeletal muscle mass of the limbs. Neutered male cats have higher energy requirements than neutered females, and gender should be considered during obesity management in cats.     

Age and body weight effects on glucose and insulin tolerance in colony cats maintained since weaning on high dietary carbohydrate

High dietary carbohydrate is suggested to promote development of diabetes mellitus in cats. Glucose tolerance, insulin sensitivity, and insulin secretion were assessed in young [0.8–2.3 (median = 1.1) years, n = 13] and mature [4.0–7.0 (median 5.8) years, n = 12] sexually intact females of a large (n ? 700) feline colony in which only dry‐type diets (35% metabolizable energy as carbohydrate) were fed from weaning. Insulin sensitivity was assessed from the ‘late‐phase’ (60–120 min) plasma insulin response of intravenous glucose tolerance tests (IVGTTs) and from fractional change in glycaemia from baseline 15 min after an insulin bolus (0.1 U/kg, i.v.). Insulin secretion was assessed from the ‘early‐phase’ (0–15 min) plasma insulin response of IVGTTs. Compared to the young cats, the mature cats had greater body weights [2.3–3.8 (median = 2.9) vs. 3.0–6.3 (median = 4.0) kg, p < 0.01], greater late‐phase insulin responses (p < 0.05), lower insulin‐induced glycaemic changes (p = 0.06), lower early‐phase insulin responses (p < 0.05), and non‐significantly different rates of glucose disposal. The late‐phase insulin response was correlated with body weight and age (p < 0.05). When group assignments were balanced for body weight, the age‐group differences and correlations became non‐significant. The findings indicate that body weight gain is more likely than dry‐type diets to induce the pre‐diabetic conditions of insulin resistance and secretion dysfunction.     

Effect of dietary protein quality and essential fatty acids on fatty acid composition in the liver and adipose tissue after rapid weight loss in overweight cats

OBJECTIVE: To examine effects of dietary protein quality (casein [CA] vs corn gluten [CG]) and dietary lipids (corn oil [CO] vs oil blend [OB] rich in long-chain polyunsaturated fatty acids [LCPUFAs]) on fatty acid composition in liver and adipose tissue after weight loss in overweight cats. ANIMALS: 24 ovariohysterectomized adult cats. PROCEDURE: Cats were allowed ad libitum access to a high-quality diet until they weighed 30% more than their ideal body weight. Cats were then randomly assigned to 1 of 4 weight-reduction diets (6 cats/diet) and were fed 25% of maintenance energy requirements per day. Diets consisted of CG-CO, CA-CO, CG-OB, and CA-OB, respectively, and were fed until cats lost weight and returned to their original lean body mass. Liver biopsy specimens and samples of perirenal, subcutaneous, and abdominal fat were obtained and analyzed for fatty acid content. RESULTS: Following weight loss, fatty acid composition of the liver and adipose tissue was primarily affected by protein quality in that cats fed CA had significantly higher percentages of 20:4(n-6) and 22:6(n-3) fatty acids than those fed CG. Cats fed the CG-CO diet had the lowest concentrations of LCPUFAs, suggesting that dietary lipids and protein quality each influence fatty acid composition in tissues. CONCLUSIONS AND CLINICAL RELEVANCE: These data provide direct evidence that dietary protein quality alters fatty acid composition of tissues during weight loss in cats. The fatty acid patterns observed suggest that protein quality may alter fatty acid composition through modulation of desaturase activity.     

Effects of dietary antioxidant supplementation before and after oral acetaminophen challenge in cats

OBJECTIVE: To determine effects of lipoic acid, vitamin E, and cysteine before and after oxidant challenge in cats. ANIMALS: 24 sexually intact adult cats. PROCEDURE: Cats were allocated into 4 equal groups. For 25 weeks, group A was fed a control dry diet and groups B, C, and D received this diet supplemented with vitamin E (2200 U/kg [dry matter basis {DMB}]) plus cysteine (9.5 g/kg [DMB]), lipoate (150 mg/kg [DMB]), or all 3 antioxidants together, respectively. Weights were measured every 3 days and venous blood obtained every 5 weeks for CBC; serum biochemical analyses; lymphocyte blastogenesis; thiobarbituric acid reactive substances concentration; and concentrations of plasma protein carbonyl, 8-OH d-guanosine, blood glutathione, plasma amino acid, lipoate, and dihydrolipoate. At 15 weeks, all cats received acetaminophen (9 mg/kg, PO, once), clinical effects were observed, and methemoglobin concentrations were measured. RESULTS: Lymphocyte blastogenesis increased transiently in group C and D cats. After acetaminophen administration, all groups had transient increases in methemoglobin within 4 hours and mild, brief facial edema; group C had decreased glutathione concentration and increased 8-OH d-guanosine concentration versus controls; and protein carbonyl concentration increased least for group B. Plasma lipoate and dihydrolipoate concentrations peaked by week 10 for groups C and D. Conclusions and Clinical Relevance-Lipoate, vitamin E, and cysteine did not have synergistic effects. Lipoate supplementation (150 mg/kg [DMB]) did not act as an antioxidant but appeared to enhance oxidant effects of acetaminophen. Vitamin E plus cysteine had protective effects.     

Body composition of breeding gilts in response to dietary protein and energy balance from thirty kilograms of body weight to completion of first parity

The relationships among BW, backfat depth, and body physical and chemical composition were evaluated in response to dietary protein and DE balance in breeding gilts from 30 kg of BW to weaning of the first litter. Large White (sire) x Landrace (dam) F1 hybrid (White; n = 75) and Landrace (sire) x (Meishan x Large White; dam) (Meishan; n = 19) hybrid gilts were received at 30 kg of BW. Five gilts were taken as the initial slaughter group at 30 kg of BW, and the remaining gilts were fed diets differing in total lysine to DE ratio, high (H) vs. low (L), from 30 kg of BW to mating (rearing), and during gestation and lactation, allowing factorial investigation of dietary treatment effects and interactions during rearing, gestation, and lactation. Gilts were slaughtered at approximately 50 and 90 kg of BW, and at mating, farrowing, and weaning. Gilts fed L diets during rearing were lighter at mating (117.9 vs. 133.6 kg of BW, P = 0.035) due to a reduction in gain (592 vs. 720 g/d, P = 0.002) and a restriction in protein accretion (83 vs. 117 g/d, P = 0.001). During rearing, lipid accretion did not differ between L- and H-fed gilts (208 vs. 198 g/d, P = 0.60), but the ratio of lipid to protein accretion was about 1.5-fold greater in L-fed gilts, where lipid mass expressed as a percentage of BW was increased at mating (26.0 vs. 21.9%, P = 0.005). Effects of L diets on lipid accretion during rearing were transient; no residual effects on body lipid mass (P > 0.17) were found at farrowing or weaning. Overall, Meishan hybrids carried greater lipid mass (P < 0.001) than White hybrid gilts. Whereas the rate of body lipid and protein accretion and body lipid and protein mass can be nutritionally influenced and can vary according to growth stage, reproductive status, and genotype, this study established that body protein mass expressed as a proportion of the lipid free empty BW remains inflexible. A value for this measure of 0.188 +/- 0.0052 was found in White and Meishan hybrid gilts ranging from 28 to 203 kg of BW and 3 to 36 mm backfat depth, covering growth, pregnancy, and lactation, and offered diets differing in protein and energy balance. Body protein mass can be predicted as approximately 0.2 of the lipid free empty BW once body lipid mass is estimated accurately from physical measurements, such as backfat depth (P2, mm) and BW (kg), by regression using lipid (kg) = - 8.14 (SE, 1.302) + 0.167 (SE, 0.010) BW + 0.883 (SE, 0.065) P2 (residual SD = 3.51; R2 = 0.912).     

Influence of dietary protein and lipid on weight loss in obese ovariohysterectomized cats

OBJECTIVE: To determine effects of dietary lipid and protein on development of hepatic lipidosis (HL) and on physical and biochemical indices following rapid weight loss in cats. ANIMALS: 24 ovariohysterectomized cats. PROCEDURE: Cats were fed a high energy diet until they gained 30% of their ideal body weight and then randomly assigned to receive 1 of 4 weight-reduction diets (6 cats/diet) at 25% of maintenance energy requirements per day. Diets contained a low or high quality protein source and a lipid source deficient or sufficient in long chain essential fatty acids (LCEFA). Serum and plasma samples and liver biopsy specimens were obtained for biochemical analyses and determination of hepatic lipid content before and after weight gain and during and after weight loss. RESULTS: Irrespective of weight-reduction diet fed, all cats lost weight at a comparable rate (4.51 to 5.00 g/d/kg of obese body weight). Three cats developed hepatic lipidosis. Significant changes in plasma insulin, cholesterol, triglyceride, and serum glucose concentrations were detected after weight gain and weight loss in all diet groups, but values for these variables did not differ among groups. CONCLUSIONS AND CLINICAL RELEVANCE: Cats can lose 25 to 30% of their obese body weight over 7 to 9 weeks without developing overt clinical signs of HL, provided that weight-reduction diets are highly palatable, contain a high quality protein, have a source of LCEFA, and are fortified with vitamins and microminerals. However, rapid weight loss may increase risk factors associated with development of diabetes mellitus.     

Leptin, body fat content and energy expenditure in intact and gonadectomized adult cats: a preliminary study

The present study was conducted to assess the body composition, leptin, and energy expenditure changes following gonadectomy in cats. Twenty-one females (12 intact and nine spayed) and 21 males (11 intact and 10 castrated) were used. Body weight was recorded. Serum plasma leptin was measured by radioimmunoassay and body composition and energy expenditure were assessed after injection of doubly labelled water. These results confirmed the gain in body weight and body fat following neutering and demonstrated a strong linear relationship between body fat and serum level of leptin. Energy expenditure decreased in castrated cats in comparison with intact ones. This study underlined the effect of gonadectomy as a major factor of obesity in cats and showed that the increase in circulating leptin reflected the amount of body fat. The present results provide further evidence that the regimen of gonadectomized cats should be carefully controlled to avoid excessive weight gain.