Effect of dietary l-carnitine supplementation on growth performance of piglets from control sows or sows treated with l-carnitine during pregnancy and lactation

IGF-1 concentration patterns and their relationship with follicle development after weaning in young sows fed different pre-mating diets

Piglet birth weight and within-litter birth weight variation are important for piglet survival and growth. Pre-mating diets may improve IGF-1 and follicle development during the weaning-to-oestrus interval (WEI) and subsequent piglet birth weight. The objective of this study was to modulate IGF-1 concentration during late lactation and the WEI of young sows by using specific pre-mating diets supplemented with microfibrillated cellulose (MF), l-carnitine (LC) or l-arginine (AR). A further objective was to investigate the relationship between IGF-1 and subsequent follicle development and oestrus and ovulation characteristics. In total, 56 first-parity and 20 second-parity sows in three consecutive batches were used for this experiment. Sows received daily either wheat (CON) or wheat plus MF, LC or AR at one of two supplementation levels (low and high) during last week of lactation and WEI. From weaning onwards, follicle and corpus luteum (CL) diameters were repeatedly measured with ultrasound. Blood samples were collected during the WEI for IGF-1 and on day 21 of pregnancy for progesterone analyses, respectively. Insulin-like growth factor-1 concentration, follicle diameter, oestrus and ovulation characteristics and CL diameter were not affected by pre-mating diets. Low IGF-1 class (≤156 ng/ml, N = 22) sows had smaller follicles at weaning (3.5 v. 3.8 mm, P < 0.05) and a longer weaning-to-ovulation interval (147.2 v. 129.8 h, P < 0.05) than high IGF-1 class sows. In first-parity sows, high loin muscle depth (LM) loss sows (≥8%, N = 28) had lower IGF-1 concentrations at weaning (167 v. 214 ng/ml, P < 0.05) compared to low LM loss sows (<8%, N = 28). However, after weaning, IGF-1 concentrations increased and did not differ between high LM loss and low LM loss sows. In conclusion, the different supplemented compounds in pre-mating diets did not improve IGF-1 concentrations around weaning in young sows. Furthermore, high body condition loss caused lower IGF-1 concentrations at weaning, but these levels rapidly recovered after weaning and were related to follicle development and the interval from weaning to ovulation.

Basic mechanisms of the regulation of L-carnitine status in monogastrics and efficacy of L-carnitine as a feed additive in pigs and poultry

A great number of studies have investigated the potential of L-carnitine as feed additive to improve performance of different monogastric and ruminant livestock species, with, however, discrepant outcomes. In order to understand the reasons for these discrepant outcomes, it is important to consider the determinants of L-carnitine status and how L-carnitine status is regulated in the animal's body. While it is a long-known fact that L-carnitine is endogenously biosynthesized in certain tissues, it was only recently recognized that critical determinants of L-carnitine status, such as intestinal L-carnitine absorption, tissue L-carnitine uptake, endogenous L-carnitine synthesis and renal L-carnitine reabsorption, are regulated by specific nutrient sensing nuclear receptors. This review aims to give a more in-depth understanding of the basic mechanisms of the regulation of L-carnitine status in monogastrics taking into account the most recent evidence on nutrient sensing nuclear receptors and evaluates the efficacy of L-carnitine as feed additive in monogastric livestock by providing an up-to-date overview about studies with L-carnitine supplementation in pigs and poultry.

Maternal L-carnitine supplementation ameliorates renal underdevelopment and epigenetic changes in male mice offspring due to maternal smoking

OBJECTIVES

Epidemiological and animal studies showed that L-carnitine (LC) supplementation can ameliorate oxidative stress-induced tissues damage. We have previously shown that maternal cigarette smoke exposure (SE) can increase renal oxidative stress in newborn offspring with postnatal kidney underdevelopment and renal dysfunction in adulthood, which were normalised by LC administration in the SE dams during pregnancy. Exposure to an adverse intrauterine environment may lead to alteration in the epigenome, a mechanism by which adverse prenatal conditions increase the susceptibility to chronic disease later in life. The current study aimed to determine whether maternal SE induces epigenetic changes in the offspring's kidney are associated with renal underdevelopment, and the protective effect of maternal LC supplementation.

METHOD

Female Balb/c mice (7 weeks) were exposed to cigarette smoke (SE) or air (Sham) for 6 weeks prior to mating, during gestation and lactation. A subgroup of the SE dams received LC via drinking water (SE + LC, 1.5 mmol/L) throughout gestation and lactation. Male offspring were studied at postnatal day (P)1, P20, and 13 weeks.

RESULTS

Maternal SE altered the expression of renal development markers glial cell line-derived neurotrophic factor and fibroblast growth factor 2, which were associated with increased renal global DNA methylation and DNA methyltransferase 1 mRNA expression at birth. These disorders were reversed by maternal LC administration.

CONCLUSION

The effect of maternal SE on renal underdevelopment involves global epigenetic alterations from birth, which can be prevented by maternal LC supplementation.

Effects ofl-carnitine and/or maize distillers dried grains with solubles in diets of gestating and lactating sows on the intestinal barrier functions of their offspring

The objective of this study was to investigate the effects ofl-carnitine and/or maize distillers dried grains with solubles (DDGS) in diets of gestating and lactating sows on the intestinal barrier functions of their offspring. The experiment was designed as a 2×2 factorial with two dietary treatments (soyabean mealv.DDGS) and twol-carnitine levels (0v.100 mg/kg in gestating diets and 0v.200 mg/kg in lactating diets). Sows (Landrace×Large White) with an average parity of 4·2 with similar body weight were randomly assigned to four groups of thirty each. Dietary supplementation withl-carnitine increased the total superoxide dismutase activity but decreased the concentration of malondialdehyde of the jejunal mucosa in newborn piglets and weaning piglets on day 21. Dietary supplementation withl-carnitine decreased the concentrations of IL-1β, IL-12 and TNF-αin the jejunal mucosa of newborn piglets and decreased the concentrations of IL-6 and TNF-αin the jejunal mucosa of weaning piglets on day 21. There was an interaction between dietary treatment andl-carnitine on the bacterial numbers of total eubacteria in the digesta of caecum in weaning piglets on day 21. Bacterial numbers of total eubacteria in weaning piglets on day 21 were significantly increased byl-carnitine only in soyabean meal diet, but there was no significant effect ofl-carnitine in DDGS-based diet. Dietary supplementation withl-carnitine increased the bacterial numbers ofLactobacillusspp. and bifidobacteria spp. in the digesta of caecum in weaning piglets on day 21. Dietary supplementation withl-carnitine in sows affected the expression of tight junction proteins (claudin 1, zonula occludens-1 (ZO-1) and occludin) in the jejunal mucosa of their offspring by increasing the expression of ZO-1 mRNA in the jejunal mucosa of newborn piglets, and by increasing the expression of ZO-1 and occludin mRNA in the jejunal mucosa of weaning piglets on day 21. In conclusion, dietary supplementation withl-carnitine in gestating and lactating sows had positive effects on intestinal barrier functions of newborn piglets and weaning piglets on day 21, but it did not have effects on intestinal barrier functions of growing–finishing pigs in the filial generation. There were no effects of dietary treatment of sows on intestinal barrier functions in their offspring.

Supplementation with l-carnitine downregulates genes of the ubiquitin proteasome system in the skeletal muscle and liver of piglets

Supplementation of carnitine has been shown to improve performance characteristics such as protein accretion in growing pigs. The molecular mechanisms underlying this phenomenon are largely unknown. Based on recent results from DNA microchip analysis, we hypothesized that carnitine supplementation leads to a downregulation of genes of the ubiquitin proteasome system (UPS). The UPS is the most important system for protein breakdown in tissues, which in turn could be an explanation for increased protein accretion. To test this hypothesis, we fed sixteen male, four-week-old piglets either a control diet or the same diet supplemented with carnitine and determined the expression of several genes involved in the UPS in the liver and skeletal muscle. To further determine whether the effects of carnitine on the expression of genes of the UPS are mediated directly or indirectly, we also investigated the effect of carnitine on the expression of genes of the UPS in cultured C2C12 myotubes and HepG2 liver cells. In the liver of piglets fed the carnitine-supplemented diet, the relative mRNA levels of atrogin-1, E214k and Psma1 were lower than in those of the control piglets (P < 0.05). In skeletal muscle, the relative mRNA levels of atrogin-1, MuRF1, E214k, Psma1 and ubiquitin were lower in piglets fed the carnitine-supplemented diet than that in control piglets (P < 0.05). Incubating C2C12 myotubes and HepG2 liver cells with increasing concentrations of carnitine had no effect on basal and/or hydrocortisone-stimulated mRNA levels of genes of the UPS. In conclusion, this study shows that dietary carnitine decreases the transcript levels of several genes involved in the UPS in skeletal muscle and liver of piglets, whereas carnitine has no effect on the transcript levels of these genes in cultivated HepG2 liver cells and C2C12 myotubes. These data suggest that the inhibitory effect of carnitine on the expression of genes of the UPS is mediated indirectly, probably via modulating the release of inhibitors of the UPS such as IGF-1. The inhibitory effect of carnitine on the expression of genes of the UPS might explain, at least partially, the increased protein accretion in piglets supplemented with carnitine.

Influence of dietary supplementation with (L)-carnitine on metabolic rate, fatty acid oxidation, body condition, and weight loss in overweight cats

OBJECTIVE

To investigate the influence of dietary supplementation with l-carnitine on metabolic rate, fatty acid oxidation, weight loss, and lean body mass (LBM) in overweight cats undergoing rapid weight reduction.

ANIMALS

32 healthy adult neutered colony-housed cats.

PROCEDURES

Cats fattened through unrestricted ingestion of an energy-dense diet for 6 months were randomly assigned to 4 groups and fed a weight reduction diet supplemented with 0 (control), 50, 100, or 150 μg of carnitine/g of diet (unrestricted for 1 month, then restricted). Measurements included resting energy expenditure, respiratory quotient, daily energy expenditure, LBM, and fatty acid oxidation. Following weight loss, cats were allowed unrestricted feeding of the energy-dense diet to investigate weight gain after test diet cessation.

RESULTS

Median weekly weight loss in all groups was ≥ 1.3%, with no difference among groups in overall or cumulative percentage weight loss. During restricted feeding, the resting energy expenditure-to-LBM ratio was significantly higher in cats that received l-carnitine than in those that received the control diet. Respiratory quotient was significantly lower in each cat that received l-carnitine on day 42, compared with the value before the diet began, and in all cats that received l-carnitine, compared with the control group throughout restricted feeding. A significant increase in palmitate flux rate in cats fed the diet with 150 μg of carnitine/g relative to the flux rate in the control group on day 42 corresponded to significantly increased stoichiometric fat oxidation in the l-carnitine diet group (> 62% vs 14% for the control group). Weight gain (as high as 28%) was evident within 35 days after unrestricted feeding was reintroduced.

CONCLUSIONS AND CLINICAL RELEVANCE

Dietary l-carnitine supplementation appeared to have a metabolic effect in overweight cats undergoing rapid weight loss that facilitated fatty acid oxidation.

Influence of l-carnitine on metabolism and performance of sows

In recent years, l-carnitine has been used increasingly as a supplement in livestock animals. The present review gives an overview of the effects of dietary l-carnitine supplementation on the reproductive performance of sows. Results concerning the effect of l-carnitine supplementation during pregnancy on litter sizes are controversial. There are some studies reporting an increased number of piglets born alive per litter, while others could not find such an effect. In contrast, most studies performed show consistently that l-carnitine supplementation to a sow diet low in native carnitine during gestation increases piglet and litter weights at birth and enhances growth of litters during the suckling period. Biochemical mechanisms underlying the favourable effect of carnitine on intra-uterine growth have not been fully elucidated. There is, however, some evidence that carnitine influences the insulin-like growth factor-axis in sows and leads to greater placentae, which in turn improves intra-uterine nutrition, and stimulates oxidation of glucose in the fetuses. These effects may, at least in part, be responsible for higher birth weights of piglets. The stimulating effect of carnitine on growth of the litters might be due to an improved suckling behaviour of piglets born to l-carnitine-supplemented sows, causing the sows' milk production to rise. In conclusion, recent studies have clearly shown that dietary l-carnitine supplementation increases the reproductive performance of sows. These findings suggest that endogenous de novo synthesis of carnitine is insufficient to meet the metabolic requirement of sows during gestation.

A moderate excess of dietary lysine lowers plasma and tissue carnitine concentrations in pigs

This study was performed to investigate whether dietary lysine concentration influences the carnitine status of pigs. Therefore, an experiment with twenty young pigs with an average body weight of 21 kg was performed which were fed either a control diet (9.7 g lysine/kg) or a diet with a moderate excess of lysine (16.8 g lysine/kg). Concentrations of all the other amino acids did not differ between the diets. Pigs fed the high-lysine diet had lower concentrations of free and total carnitine in plasma, liver, kidney and skeletal muscle than control pigs (P<0.05). Pigs fed the high-lysine diet moreover had an increased concentration of trimethyllysine (TML), a reduced mRNA abundance of TML dioxygenase and reduced concentrations of gamma-butyrobetaine (BB) in muscle, indicating that the conversion of TML into BB in muscle was impaired. Concentrations of BB, the metabolic precursor of carnitine, in plasma, liver and kidney were also reduced in pigs fed the high-lysine diet while the activity of BB dioxygenase in kidney was not different and that in liver was even increased compared to control pigs (P<0.05). In conclusion, this study shows that a moderate dietary excess of lysine lowers plasma and tissue carnitine concentrations in pigs. Reduced concentrations of BB in liver and kidney suggest that the depressed carnitine status was likely caused by a decreased rate of carnitine synthesis due to a diminished availability of carnitine precursor, probably mainly as a result of an impaired BB formation in muscle.

Growth characteristics, blood metabolites, and insulin-like growth factor system components in maternal tissues of gilts fed L-carnitine through day seventy of gestation1,2

A total of 59 gilts (BW = 137.7 kg) from 3 breeding groups were used to assess the effects of feeding l-carnitine during gestation on gilt growth characteristics, blood metabolites, and uterine and chorioallantoic expression of IGF axis components at d 40, 55, and 70 of gestation. Experimental treatments were arranged in a 2 x 3 factorial, with main effects of added l-carnitine (0 or 50 ppm) and day after initial breeding (d 40, 55, or 70 of gestation). All gilts received a constant feed allowance of 1.75 kg/d and a top-dress containing 0 or 50 ppm of l-carnitine beginning on the first day of breeding through the assigned day of gestation. No dietary treatment differences were observed for gilt BW, backfat, or estimated protein or fat mass at any day of gestation. No differences were observed in circulating total and free carnitine at breeding, but concentrations increased (P < 0.01) as day of gestation increased for gilts fed diets containing l-carnitine compared with those fed the control diet. Maternal IGF-I concentration decreased (P < 0.01) from d 0 to 70 for all gilts, with no differences between treatments. Insulin-like growth factor binding protein-3 mRNA (P = 0.05) and IGFBP-5 mRNA (P = 0.01) increased in the endometrium of gilts supplemented with l-carnitine. These data demonstrate that l-carnitine supplementation and day of gestation alter the expression of the IGF axis by changing the expression of IGFBP at the fetal-maternal interface in swine. These changes in the IGF axis at the fetal maternal interface may aid in determining the reasons for the effects of l-carnitine on reproductive traits.

Body composition, muscle fibre characteristics and postnatal growth capacity of pigs born from sows supplemented with L-carnitine

Recently, it has been shown that supplementation of sows with L-carnitine increases their plasma concentrations of insulin-like growth factor (IGF)-I, and it has been hypothesized that this may stimulate fetal myogenesis. This study was performed to investigate whether piglets of sows supplemented with L-carnitine differ in muscle fibre characteristics, chemical body composition and postnatal growth capability from pigs of control sows. Muscle fibre characteristics and chemical body composition were determined at weaning in 21 piglets of control sows and 21 piglets of sows treated with L-carnitine with similar body weights; postnatal growth capability was determined from weaning until slaughter at a body weight of 118 kg in 80 pigs of control sows and 80 pigs of sows treated with L-camitine which had also similar body weights at weaning. Piglets of sows supplemented with L-carnitine did not differ in number, area, diameter and type (percentages of slow twitch oxidative + fast twitch oxidative fibres, and fast twitch glycolytic fibres) of muscle fibres in m. longissimus dorsi and m. semitendinosus and in chermical body composition (concentrations of dry matter, crude protein, crude fat) from piglets of control sows. Postnatal growth capability (body weight gains, feed conversion ratio) from weaning to slaughter as well as carcass composition (carcass yield, meat thickness, fat thickness) was also not different between pigs of sows treated with L-carnitine and pigs of control sows. In conclusion, data of this study do not support the hypothesis that L-carnitine supplementation of sows during pregnancy enhances fetal muscle fibre development and increases postnatal growth capability of the offspring.