Betaine increases net portal absorption of volatile fatty acids in Iberian pigs.

Betaine is an osmolyte with the potential to increase volatile fatty acids (VFAs) production and hence improve intestinal health.The present study investigated how betaine affects portal and arterial concentrations and net portal absorption (NPA) of VFA in growing Iberian pigs. Eight 30 kg BW Iberian growing barrows with indwelling catheters in portal vein, ileal vein and carotid artery were randomly assigned to a control diet or a diet supplemented with 0.5% betaine. Para-aminohippuric acid was infused into the ileal vein as a marker to determine portal blood flow using the dilution method. Blood samples were simultaneously taken from the carotid artery and portal vein at -60, 60, 120, 180, 240, 300 and 360 min after feeding 1 200 g of the diet. The NPA of VFA (acetate, propionate, butyrate, valerate, isobutyrate and caproate) was determined by multiplying the porto-arterial plasma concentration differences by portal plasma flow. Betaine increased NPA of acetate (1.44 fold; P < 0.001) and total VFA (0.55 fold; P < 0.001) while decreased NPA of propionate (-0.38 fold; P < 0.05) and valerate (-1.46 fold; P < 0.05) compared with control pigs. Estimated heat production potentially derived from NPA of VFA accounted for 0.20-0.27 of metabolizable energy for maintenance. Acetate and propionate accounted for most of the total VFA estimated heat production (0.83-0.89). Regarding bacterial communities, betaine apparently did not change the DNA abundance of fecal total bacteria, Lactobacillus, Bifidobacterium, Enterobacteriaceae, Bacteroides and the Clostridium clusters I, IV and XIV. In conclusion, betaine increased portal appearance and NPA of VFA, contributing to cover maintenance energy requirements.

Protein retention, growth performance and carcass traits of individually housed immunocastrated male- and female- and surgically castrated male Iberian pigs fed diets of increasing amino acid concentration.

Immunocastration (IC, vaccination against gonadotropin releasing hormone (GnRH)) is one alternative to surgical castration (SC) for preventing sexual development and boar taint in male pigs. A temporal increase in performance has been described for IC pigs before the second vaccination against GnRH. The objective of this work was to assess the effects of IC on Iberian male and female pigs (fed diets of increasing CP content) on performance, nitrogen retention (NR) and digestibility, and carcass traits. Fifty-four pure Iberian pigs individually housed were allocated to a 3 × 3 factorial arrangement with three sex groups (IC males, IC females and SC males), three diets (153, 137 and 119 g CP/kg DM; 14 MJ metabolisable energy/kg DM) and six pigs per treatment combination. Pigs were vaccinated at 18 weeks of age (40 kg BW) and seven weeks later (70-80 kg BW) and fed at 0.9 × ad libitum on BW basis. Two digestibility and nitrogen balance assays were performed before and after the second vaccination, respectively. Pigs were slaughtered at 105 kg BW. Before the second vaccination, Iberian IC males showed higher growth rate (g/day), feed efficiency, NR (g/day) and efficiency of NR than the other groups (P < 0.001). The NR and efficiency of NR was 40% greater in IC v. SC males (P < 0.001). After the second vaccination, no differences in performance between sex groups were detected (P > 0.05). Growth rate and feed efficiency were higher in IC males than in the other groups for the whole experimental period (from the first vaccination to slaughter; P < 0.001). After the second vaccination, differences among sex groups in NR and the efficiency of NR disappeared (P > 0.05). NR efficiency was 0.177 on average. No significant effects of dietary CP were detected on performance. The NR was greater in pigs fed the 153 CP diet (17 to 37%; P > 0.05). Lean components of carcass (sirloin, loin and butt lean) were greater in IC males than in the other groups (0.001 < P < 0.05). There were no significant sex group×dietary CP interactions. Iberian IC males grew at higher rate, deposited more protein, and more efficiently, than Iberian SC males before the second vaccination against GnRH. Iberian IC females showed similar growth performance to SC males and intermediate protein deposition efficiency between IC and SC males. Despite the higher growth performance, protein deposition rate, and efficiency of protein deposition of IC males v. SC males, no significant differences in amino acid requirements were detected between them.

Conjugated linoleic acid and betaine affect lipolysis in pig adipose tissue explants.

Consumers' demand of leaner meat products is a challenge. Although betaine and conjugated linoleic acid (CLA) have the potential to decrease porcine adipose tissue, their mode of action is poorly understood. The aim of the study was to determine the lipolytic effect of betaine and CLA in the adipose tissue of Iberian pigs. Adipose tissue explants from five pigs (38 kg BW) were prepared from dorsal subcutaneous adipose tissue samples and cultivated for 2 h (acute experiments) or 72 h (chronic experiments). Treatments included 100 µM linoleic acid (control), 100 µM trans-10, cis-12 CLA, 100 µM linoleic acid + 1 mM betaine and 100 µM trans-10, cis-12 CLA + 1 mM betaine (CLABET). To examine the ability of betaine or CLA to inhibit insulin's suppression of isoproterenol-stimulated lipolysis, test medium was amended with 1 µM isoproterenol ±10 nM insulin. Media glycerol was measured at the end of the incubations. Acute lipolysis (2 h) was increased by CLA and CLABET (85% to 121%; P < 0.05) under basal conditions. When lipolysis was stimulated with isoproterenol (1090%), acute exposure to betaine tended to increase (13%; P = 0.071), while CLA and CLABET increased (14% to 18%; P < 0.05) isoproterenol-stimulated lipolysis compared with control. When insulin was added to isoproterenol-stimulated explants, lipolytic rate was decreased by 50% (P < 0.001). However, supplementation of betaine to the insulin + isoproterenol-containing medium tended to increase (P = 0.07), while CLABET increased (45%; P < 0.05) lipolysis, partly counteracting insulin inhibition. When culture was extended for 72 h, CLA decreased lipolysis under basal conditions (18%; P < 0.05) with no effect of betaine and CLABET (P > 0.10). When lipolysis was stimulated by isoproterenol (125% increase in rate compared with basal), CLA and CLABET decreased glycerol release (27%; P < 0.001) compared with control (isoproterenol alone). When insulin was added to isoproterenol-stimulated explants, isoproterenol stimulation of lipolysis was completely blunted and neither betaine nor CLA altered the inhibitory effect of insulin on lipolysis. Isoproterenol, and especially isoproterenol + insulin, stimulated leptin secretion compared with basal conditions (68% and 464%, respectively; P < 0.001), with no effect of CLA or betaine (P > 0.10). CLA decreased leptin release (25%; P < 0.001) when insulin was present in the media, partially inhibiting insulin stimulation of leptin release. In conclusion, betaine and CLA produced a biphasic response regarding lipolysis so that glycerol release was increased in acute conditions, while CLA decreased glycerol release and betaine had no effect in chronic conditions. Furthermore, CLA and CLABET indirectly increased lipolysis by reducing insulin-mediated inhibition of lipolysis during acute conditions.

Influence of para-aminohippuric acid analysis on net portal-drained viscera flux of nutrients in pigs.

In nutrition studies, para-aminohippuric acid (PAH) is a marker frequently used to measure blood flow in pigs, which is essential for estimating portal-drained viscera (PDV) flux of nutrients. The aim of this study was to evaluate the PAH analytical method by means of qualimetric statistical procedures to estimate the matrix effect and the accuracy and limits of quantitation of the method. Net PDV flux of nutrients was determined in five multi-catheterized pigs using water, plasma or commercial serum as standard matrix. A proportional systematic error due to matrix effect was found for plasma and serum. Mean recovery was 99.4%, and intra- and inter-day precision of the method was 2.4% and 3.8% relative standard deviation, respectively. The limit of quantification was 0.22 mg PAH/l. Use of water for the PAH standard curves underestimated portal blood flow compared with PAH standards prepared with plasma or commercial serum (706, 954 and 927 ml/min; P<0.05, respectively). Consequently, PDV O2 consumption, glucose and amino acids fluxes were underestimated by 33% (P<0.001). In conclusion, our results stress the importance of using plasma from pigs not infused with PAH or alternatively commercial pig serum to prepare PAH standards to determine blood flow in pigs to avoid underestimation of blood flow.

Gender-related amino acid intake of adult wild Red-legged Partridge (Alectoris rufa).

The Red-legged Partridge (Alectoris rufa) is under an enormous hunting pressure. It is bred intensively in game farms. The hunting season is during the non-reproductive resting period when partridges are at maintenance conditions. There is a lack of information about the amino acid (AA) composition of the natural diet of the adult birds in their habitat or differences in dietary AA composition related to gender. The objective of this work was to establish a first approach to the AA composition of the natural diet of adult wild Red-legged Partridge. Food content in crops and gizzards of female and male birds hunted in the same hunting season and area was analysed for AA composition. Females food had higher concentrations of individual essential AA (EAA) and non-essential AA (NEAA) than males. There are important differences in the concentration of AA in the natural diet of wild females and males. It may be advisable to use diets differing in the proportion of individual AA in the game farms during the non-reproductive resting period.

Metabolic differences in hepatocytes of obese and lean pigs.

There are important differences in terms of metabolic activity, energy utilization and capacity of protein and fat deposition when Iberian and modern pigs are compared. Primary culture of hepatocytes was used to evaluate hepatic function and sensitivity to hormones between breeds without the interference of circulating blood factors. Hepatocytes were isolated from pure Iberian (n=10) and Landrace (n=8) pigs of similar BW (24.5±12.1 and 32.9±6.1 kg BW, respectively), by collagenase perfusion. Monolayers were established in medium containing fetal bovine serum for 1 day and switched to serum-free medium for the remainder of the culture period. Hepatocytes were maintained in William's E supplemented with ß-mercaptoethanol (0.1 mM), glutamine (2 mM), antibiotics (gentamicin, penicillin, streptomycin and amphotericin B), dimethyl sulfoxide (1 µg/ml), dexamethasone (10-8 M), insulin (0.173 and 17.3 nM) and glucagon (0.287, 2.87 and 28.7 nM) for 24 to 48 h. Gluconeogenesis (GNG), glycogen degradation, triglycerides (TG) content and esterification, ß-hydroxybutyrate (BHB) synthesis, IGF-1 synthesis, albumin and urea synthesis were determined. Iberian pigs had greater capacity of GNG than Landrace (24%, P<0.05), although no difference in glycogen degradation was found (P>0.10). TG content and esterification tended to be lower in hepatocytes from Iberian compared with Landrace pigs (12% and 31%, respectively; 0.100.10). IGF-1 synthesis was diminished in hepatocytes from Iberian compared with Landrace pigs (16%, P<0.05). On the contrary, rate of albumin synthesis was greater in Iberian compared with Landrace pigs (58%, P<0.05). Finally, the capacity of urea synthesis was lower in hepatocytes of Iberian compared with Landrace pigs (37%, P<0.05). When ammonia was added to the media, urea concentration increased (648%, 1108% and 2791% when 0 mM was compared with 2.5, 5 and 10 mM, respectively). Urea synthesis increased on increasing ammonia content (55% and 325% when 0 mM was compared with 5 and 10 mM, respectively; P<0.0001). In conclusion, the genetic background accounts for important differences in protein and energy metabolism pathways found in primary culture of hepatocytes from lean and obese pigs.

Changes in tissue free amino acid pools in growing chickens fed thermally treated vetch diets.

A three-day assay was developed to evaluate the effect of autoclaving on protein quality of vetch as an alternative to classical growth methods. Male chickens (n = 10/diet) were given approximately isonitrogenous diets based on raw or autoclaved vetch for 3 days. Samples of plasma, muscle and liver were obtained for free amino acid analysis. Heating vetch depressed growth (11.9 vs. 23.2 g/d; p < 0.05). Plasma methionine and histidine increased (0.05 < p < 0.06), while gluconeogenic amino acids tended to decrease (p < 0.10) after heating. Muscle free amino acids did not change except for a trend to increased methionine (p = 0.06) in birds fed autoclaved vetch. In liver, most essential amino acids, glycine, proline and tyrosine increased markedly with heated vetch diet. Correlations between plasma and muscle free amino acids were poor compared with those between plasma and liver free amino acids. Liver free amino acid pool was more sensitive than muscle or plasma pool to amino acid inflow modifications after vetch heating.

Impact of dietary betaine and conjugated linoleic acid on insulin sensitivity, protein and fat metabolism of obese pigs.

To determine possible mechanisms of action that might explain the nutrient partitioning effect of betaine and conjugated linoleic acid (CLA) in Iberian pigs and to address potential adverse effects, twenty gilts were restrictively fed from 20 to 50 kg BW Control, 0.5% betaine, 1% CLA or 0.5% betaine + 1% CLA diets. Serum hormones and metabolites profile were determined at 30 kg BW and an oral glucose test was performed before slaughter. Pigs were slaughtered at 50 kg BW and livers were obtained for chemical and histological analysis. Decreased serum urea in pigs fed betaine and betaine + CLA diets (11%; P = 0.0001) indicated a more efficient N utilization. The increase in serum triacylglycerol (58% and 28%, respectively; P = 0.0098) indicated that CLA and betaine + CLA could have reduced adipose tissue triacylglycerol synthesis from preformed fatty acids. Serum glucose, low-density lipoprotein (LDL) cholesterol and non-esterified fatty acids were unaffected. CLA and betaine + CLA altered serum lipids profile, although liver of pigs fed CLA diet presented no histopathological changes and triglyceride content was not different from Control pigs. Compared with controls, serum growth hormone decreased (20% to 23%; P = 0.0209) for all treatments. Although serum insulin increased in CLA, and especially in betaine + CLA pigs (28% and 83%; P = 0.0001), indices of insulin resistance were unaffected. In conclusion, CLA, and especially betaine + CLA, induced changes in biochemical parameters and hormones that may partially explain a nutrient partitioning effect in young pigs. Nevertheless, they exhibited weak, although detrimental, effects on blood lipids. Moreover, although livers were chemically and histologically normal, pigs fed CLA diet challenged with a glucose load had higher serum glucose than controls.

In vivo body composition in autochthonous and conventional pig breeding groups by dual-energy X-ray absorptiometry and magnetic resonance imaging under special consideration of Cerdo Ibérico.

The improvement of carcass quality is one of the main breeding goals in pig production. To select appropriate breeding animals, it is of major concern to exactly and reliably analyze the body composition in vivo. Therefore, the objective of the study was to examine whether the combination of dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) offers the opportunity to reliably analyze quantitative and qualitative body composition characteristics of different pig breeding groups in vivo. In this study, a total of 77 pigs were studied by DXA and MRI at an average age of 154 days. The pigs originated from different autochthonous or conventional breeds or crossbreeds and were grouped into six breed types: Cerdo Ibérico (Ib); Duroc × Ib (Du_Ib); White Sow Lines (WSL, including German Landrace and German Large White); Hampshire/Pietrain (Pi_Ha, including Hampshire, Pietrain × Hampshire (PiHa) and Pietrain × PiHa); Pietrain/Duroc (Pi_Du, including Pietrain × Duroc (PiDu) and Pietrain × PiDu); crossbred WSL (PiDu_WSL, including Pietrain × WSL and PiDu × WSL). A whole-body scan was performed by DXA with a GE Lunar DPX-IQ in order to measure the amount and percentage of fat tissue (FM; %FM), lean tissue (LM; %LM) and bone mineral, whereas a Siemens Magnetom Open with a large body coil was used for MRI in the thorax region between 13th and 14th vertebrae in order to measure the area of the loin (LA) and the above back fat area (FA) of both body sides. A GLM procedure using SAS 9.2 was used to analyze the data. As expected, the native breed Ib followed by Du_Ib crossbreeds showed the highest %FM (27.2%, 25.0%) combined with the smallest LA (46.2 cm2, 73.6 cm2), whereas Ib had the lowest BW at an average age of 154 days. Pigs with Pi_Ha origin presented the least %FM (12.4%) and largest LA (99.5 cm2). The WSL and PiDu_WSL showed an intermediate body composition. Therefore, it could be concluded that DXA and MRI and especially their combination are very suitable methods to reliably identify differences in body composition and carcass traits among different pig lines in vivo.

Metabolic regulation of fatty acid esterification and effects of conjugated linoleic acid on glucose homeostasis in pig hepatocytes.

Conjugated linoleic acids (CLAs) are geometric and positional isomers of linoleic acid (LA) that promote growth, alter glucose metabolism and decrease body fat in growing animals, although the mechanisms are poorly understood. A study was conducted to elucidate the effects of CLA on glucose metabolism, triglyceride (TG) synthesis and IGF-1 synthesis in primary culture of porcine hepatocytes. In addition, hormonal regulation of TG and IGF-1 synthesis was addressed. Hepatocytes were isolated from piglets (n = 5, 16.0 ± 1.98 kg average body weight) by collagenase perfusion and seeded into collagen-coated T-25 flasks. Hepatocytes were cultured in William's E containing dexamethasone (10-8 and 10-7 M), insulin (10 and 100 ng/ml), glucagon (0 and 100 ng/ml) and CLA (1 : 1 mixture of cis-9, trans-11 and trans-10, cis-12 CLA, 0.05 and 0.10 mM) or LA (0.05 and 0.10 mM). Addition of CLA decreased gluconeogenesis (P < 0.05), whereas glycogen synthesis and degradation, TG synthesis and IGF-1 synthesis were not affected compared with LA. Increased concentration of fatty acids in the media decreased IGF-1 production (P < 0.001) and glycogen synthesis (P < 0.01), and increased gluconeogenesis (P < 0.001) and TG synthesis (P < 0.001). IGF-1 synthesis increased (P < 0.001) and TG synthesis decreased (P < 0.001) as dexamethasone concentration in the media rose. High insulin/glucagon increased TG synthesis. These results indicate that TG synthesis in porcine hepatocytes is hormonally regulated so that dexamethasone decreases and insulin/glucagon increases it. In addition, CLA decreases hepatic glucose production through decreased gluconeogenesis.

Differences in portal appearance of lysine and methionine in Iberian and Landrace pigs.

Compared to modern breeds, Iberian pigs have lower rates of muscle protein deposition and greater viscera weight. Factors that limit growth performance of Iberian pigs are unknown. We hypothesized that differences in net portal appearance of the essential AA Lys and Met might partially explain the lower growth rate reported in Iberian pigs compared to modern breeds. Net portal appearance of AA was measured in 6 Iberian and 6 Landrace gilts (28 kg BW) fitted with chronic catheters in the portal vein, carotid artery, and mesenteric vein. Blood samples were taken for 6 h after feeding 2 isoenergetic diets (14.0 to 14.5 MJ ME/kg DM) with low CP (LCP) and high CP (HCP) (13 vs. 16%, respectively) in a crossover design after a 1-wk adaptation. Net portal appearance of Lys was greater (P < 0.05) when pigs consumed the HCP than LCP diet (23 vs. 15 µmol/min); breeds did not differ. Net portal appearance of Met tended to be higher (P = 0.076) for pigs fed HCP than LCP diet (4.4 vs. 3.6 µmol/min); breeds did not differ. In conclusion, differences in portal appearance of Lys and Met did not exist between Iberian and Landrace pigs fed barley (Hordeum vulgare)-soybean (Glycine max) diets with low and high protein concentration.

Influence of betaine and conjugated linoleic acid on development of carcass cuts of Iberian pigs growing from 20 to 50 kg body weight.

Twenty Iberian gilts (20 kg body weight, BW) were fed diets containing no betaine or conjugated linoleic acid (CLA) (Control), 0.5% betaine, 1% CLA, or 0.5% betaine+1% CLA. Additionally, 5 pigs were killed at 20 kg BW for the initial points of the allometric equations. At 50 kg BW, left semicarcasses were cut into primal cuts, hams and shoulders trimmed and dissected. CLA alone did not affect any analyzed parameter. Betaine increased (23 and 21%, respectively) the yield of shoulder butt and spine and decreased allometric growth coefficient of belly and backfat, compared to Control diet. Tenderloins and trimmed hams of pigs fed CLA+betaine diet developed later and were heavier (22 and 5%, respectively) than Control pigs. Also, leaf fat developed earlier and had lighter weight (32%). Furthermore, pigs fed CLA+betaine diet had heavier lean (5%) and fat free lean (6%) of shoulders compared to Control pigs.

Synergistic effects of betaine and conjugated linoleic acid on the growth and carcass composition of growing Iberian pigs.

An experiment was conducted to determine the efficacy of dietary betaine, CLA, or both as growth promotants and carcass modifiers in growing Iberian pigs. Twenty gilts (20 kg of BW) were individually penned and fed barley- and soybean meal-based diets (12% CP, 0.81% Lys, and 14.8 MJ of ME/kg of DM) containing either no added betaine or CLA (control), 0.5% betaine, 1% CLA, or 0.5% betaine + 1% CLA, at 95% of ad libitum energy intake. An additional group of 5 pigs was slaughtered at the beginning of the experiment to obtain the initial body composition. At 30 kg of BW, a balance experiment was conducted. At 50 kg of BW, pigs were slaughtered and viscera was removed and weighed. Betaine or CLA alone did not affect growth performance. However, betaine + CLA increased ADG (601 vs. 558 g, P = 0.03) and gain relative to ME intake (25.4 vs. 22.2 g/MJ, P = 0.03) compared with control pigs. Digestibility of nutrients and metabolizability of energy did not differ among diets (P = 0.46 to 0.75). Carcass protein, water, and lean deposition (g/d) increased (19.8, 24.2, and 23.4%, respectively, P < 0.01) in pigs fed betaine + CLA compared with control pigs. Similarly, protein deposition relative to ME intake increased by 28% in betaine + CLA-supplemented pigs (P < 0.05). Fat and mineral deposition did not differ among treatments. Carcass protein, water, and lean content (g/kg of carcass) of pigs fed betaine + CLA-supplemented diets tended to increase (P = 0.07 to 0.09) and carcass fat content tended to decrease (P = 0.09). Similarly, estimated composition of carcass gain was affected, such that water and lean content tended to increase (P = 0.06 to 0.08), whereas fat tended to decrease (P = 0.08) in pigs fed betaine + CLA-supplemented diets. Longissimus muscle area was not altered by treatments (P = 0.49). The liver of pigs fed betaine + CLA diets had increased weight (19%, P < 0.05) compared with control pigs. Overall, dietary supplementation of betaine + CLA increased ADG, protein, water, and lean deposition in growing Iberian gilts. There appears to be a synergistic action when betaine and CLA are used together.

The role of insulin, glucagon, dexamethasone, and leptin in the regulation of ketogenesis and glycogen storage in primary cultures of porcine hepatocytes prepared from 60 kg pigs.

A study was conducted to elucidate hormonal control of ketogenesis and glycogen deposition in primary cultures of porcine hepatocytes. Hepatocytes were isolated from pigs (54-68 kg) by collagenase perfusion and seeded into collagen-coated T-25 flasks. Monolayers were established in medium containing fetal bovine serum for 1 day and switched to a serum-free medium for the remainder of the culture period. Hepatocytes were maintained in DMEM/M199 containing 1% DMSO, dexamethasone (10(-6) or 10(-7) M), linoleic acid (3.4 x 10(-5) M), and carnitine (10(-3) M) for 3 days. On the first day of serum-free culture, insulin was added at 1 or 100 ng/ml and glucagon was added at 0, 1, or 100 ng/ml. Recombinant human leptin (200 ng/ml) was added during the final 24 h; medium and all cells were harvested on the third day. Concentrations of acetoacetate and beta-hydroxybutyrate (ketone bodies) in media and glycogen deposition in the cellular compartment were determined. Ketogenesis was highly stimulated by glucagon (1 and 100 ng/ml) and inhibited by insulin. In contrast, glycogen deposition was stimulated by insulin and attenuated by glucagon; high insulin was also associated with a reduction in the ketone body ratio (acetoacetate:beta-hydroxybutyrate). High levels of dexamethasone stimulated ketogenesis, but inhibited glycogen deposition at low insulin. Culture of cells with leptin for 24 h, over the range of insulin, glucagon, and dexamethasone concentrations had no effect on either glycogen deposition or ketogenesis. These data suggest that while adult porcine hepatocytes are indeed sensitive to hormonal manipulation, leptin has no direct influence on hepatic energy metabolism in swine.

Effect of dietary betaine on nutrient utilization and partitioning in the young growing feed-restricted pig.

The purpose of this study was to examine the effects of dietary betaine over a range of concentrations (between 0 and 0.5%) on growth and body composition in young feed-restricted pigs. Betaine is associated with decreased lipid deposition and altered protein utilization in finishing pigs, and it has been suggested that the positive effects of betaine on growth and carcass composition may be greater in energy-restricted pigs. Thirty-two barrows (36 kg, n = 8 pigs per group) were restrictively fed one of four corn-soybean meal-skim milk based diets (18.6% crude protein, 3.23 Mcal ME/kg) and supplemented with 0, 0.125, 0.25, or 0.5% betaine. Feed allotment was adjusted weekly according to BW, such that average feed intake was approximately 1.7 kg for all groups. At 64 kg, pigs were slaughtered and visceral tissue was removed and weighed. Carcasses were chilled for 24 h to obtain carcass measurements. Subsequently, one-half of each carcass and whole visceral tissue were ground for chemical analysis. Linear regression analysis indicated that, as betaine content of the diet was elevated from 0 to 0.5%, carcass fat concentration (P = 0.06), P3 fat depth (P = 0.14) and viscera weight (P = 0.129) were decreased, whereas total carcass protein (P = 0.124), protein deposition rate (P = 0.98), and lean gain efficiency (P = 0.115) were increased. The greatest differences over control pigs were observed in pigs consuming 0.5% betaine, where carcass fat concentration and P3 fat depth were decreased by 10 and 26%, respectively. Other fat depth measurements were not different (P > 0.15) from those of control pigs. In addition, pigs consuming the highest betaine level had a 19% increase in the carcass protein:fat ratio, 23% higher carcass protein deposition rate, and a 24% increase in lean gain efficiency compared with controls. Dietary betaine had no effects (P > 0.15) on growth performance, visceral tissue chemical composition, carcass fat deposition rate, visceral fat and protein deposition rates, or serum urea and ammonia concentrations. These data suggest that betaine alters nutrient partitioning such that carcass protein deposition is enhanced at the expense of carcass fat and in part, visceral tissue.

Effect of a low protein diet on the energy metabolism of growing chickens.

Two slaughter experiments were carried out to determine whether the protein content of the diet has an influence upon the efficiency of utilization of ME in fast growing chickens. A normal-protein diet (NPD, 204 g CP/kg DM: 14.7 MJ ME/kg DM) based on soybean meal as the sole source of protein was given at four different levels of intake (ad libitum or restricted at about 90, 65 and 40% ad lib) to 10-d-old animals for 2 weeks. In a parallel experiment the chickens were fed ad libitum a low protein diet (LPD, 66 g CP/kg DM: 15.0 MJ ME/kg DM) based on soybean meal. The intake of metabolizable energy ranged from 1675 to 777 and 1770 to 832 kJ/kgW0.75 per day for NPD and LPD treatments, respectively. Mean values of energy retention, gross efficiency of energy utilization and energy retained as protein were significantly (P < .05) lower and heat production (expressed as both kJ/kgW0.75 per day and kJ/kg body protein content0.75 per day) was significantly higher (P < .05) for the chickens fed on LPD. These findings support the concept of dietary-induced thermogenesis in response to reductions in dietary protein concentration. It is concluded that the increased heat production found in the birds fed on the low-protein diet can be explained by both an increase in energy requirements for maintenance (MEm) and a sharp decrease in the efficiency of utilization of ME of growth (k(g)).

Effect of dietary protein quality on energy metabolism in growing chickens.

A slaughter experiment was carried out to study the effect of dietary protein quality on maintenance energy requirements and energy costs for protein accretion and fat deposition in fast-growing broiler-type male chickens. Three isonitrogenous (200 g crude protein/kg DM) and isoenergetic (14 kJ metabolizable energy (ME)/g DM) semipurified diets based on soyabean meal unsupplemented (diet S) or supplemented with 20 g L-lysine/kg (diet SL) or 2 g DL-methionine/kg (diet SM), in order to promote a decrease or an increase in growth rate respectively, were selected and given at four feeding levels (ad lib. or restricted to 40, 28 and 18 g DM/d, on average) to 10-d-old fast-growing male broiler-type chicks for 2 weeks. Both the efficiency with which ME was used to support growth (kg) and the maintenance requirements (MEm) significantly decreased inversely to the biological value of the dietary protein (kg = 0.660, 0.600 and 0.572; MEm = 597, 522 and 464 kJ/kg W0.75 per d, for diets SL, S and SM respectively). The partial efficiencies of use of ME for protein accretion (kp) or fat deposition (kf) were also inversely related, the former increasing with the quality of the protein offered. An alternative procedure was used to try to overcome the statistical problems inherent in the partition of ME between fat and protein.

Effect of dietary protein quality, feed restriction and short-term fasting on protein synthesis and turnover in tissues of the growing chicken.

The effect of dietary protein quality and quantity on fractional rates of protein synthesis (ks) and degradation (kd) in the skeletal muscle, liver, jejunum and skin of young growing chickens was studied. Chickens were either fasted overnight or were fed at frequent intervals, using continuous feeders, with equal amounts of a diet containing soya-bean meal as the sole protein source, unsupplemented, or supplemented with either lysine or methionine. Each of the three diets was provided at 2 or 0.9 x maintenance. On the higher intake, birds on the unsupplemented diet gained weight, lysine supplementation decreased and methionine supplementation increased body-weight gain (by -23% and +22% respectively). Birds fed at 0.9 x maintenance lost weight; supplementation with methionine or lysine did not influence this weight loss. None of the dietary regimens had significant effects on protein synthesis rates in any of the tissues, thus the mechanism whereby muscle mass increased in response to methionine supplementation appeared to be a decrease in the calculated rate of protein degradation. Similarly, on the 0.9 x maintenance diet the failure of the animals to grow appeared to be due to an increase in the rate of protein degradation rather than an effect on synthesis. Conversely, muscle ks was decreased in fasted chickens previously fed on the unsupplemented diet at 2 x maintenance, and in birds which had received the 0.9 x maintenance diet fasting resulted in a similar reduction in protein synthesis in muscle; ks in the liver and jejunum was also significantly decreased.(ABSTRACT TRUNCATED AT 250 WORDS)