The ability of the porcine intestinal microflora to resist the establishment of pathogenic bacteria has been demonstrated previously (Hillman et al, 1994). Subsequent work has shown that certain intestinal lactobacilli react to the presence of a culture filtrate derived from a coliform pathogen by increasing their antagonistic activity towards that pathogen (Hillman and Robertson, unpublished), indicating the presence of a quorum-sensing or related mechanism. The current experiment was devised to determine whether a similar effect could be produced within the entire porcine colonic microflora, using an in vitro simulation system.

There is a considerable body of information on the voluntary feed intake of pigs fed on dry diets. However, there is a paucity of information on the factors affecting feed intake of pigs fed liquid diets. Pigs have a limit to their volumetric intake and will normally maximise dry matter intake when fed dry diets, ad libitum. For pigs fed dry feed the requirement for water per unit of dry matter will be dependent upon the composition of the feed and the requirement for renal clearance of nitrogen and minerals. What is not clear, is whether presenting the feed mixed with water results in excessive water intake that produces a point loading of the stomach, which in turn limits voluntary feed intake, i.e. whether physical bulk limitations override the normal homeostatic control. Therefore, it is not possible to extrapolate from data generated with dry fed pigs and anticipate voluntary intake of pigs fed dilute liquid diets. The aim of this study was to determine the effect of dry matter concentration of liquid feed on feed intake and growth performance of grower-finisher pigs.

There is potential for improving the growth performance of pigs through a better understanding of factors that influence the digestibility of nutrients and energy in liquid feeds. These factors include dry matter content and the size and distribution of particles of the dry feed components within the liquid diet. The objective of the current study was to determine if changing the dry matter concentration of liquid feeds affects the digestibility and retention of nutrients and energy in pigs growing from 35kg to 95kg live weight.

Farrowing and lactation are two of the most critical phases of pork production. A relatively high proportion of pig losses occurs during these periods. Rapid bacterial colonisation of piglets’ sterile gut and underdeveloped immune system represents a very dangerous combination of events. The most significant factors affecting the microflora of the piglet’s gut is its mother and the environment into which it is born. Therefore, management interventions and nutritional regimes that influence the microbiology of the sow’s faeces in a beneficial way are likely also to influence the neonate. Work at the University of Plymouth and at Foulum in Denmark has shown that feed may be fermented successfully with lactic acid bacteria (LAB) and that this process reduces the number of salmonellae and coliforms in the feed and consequently in the lower gastrointestinal tract (Brooks et al. 2001). Recent studies strongly support the hypothesis that orally administered LAB stimulate the immune system, both at the local and systemic level. This combination of effective immunity and reduced level of environmental contamination with faecal pathogens can lead to improved management of sows for increased litter size and weight at weaning time.

Purpose of researches in feed restriction area is improvement of feed efficiency, decrease of carcass fat content and abdominal fat pad size (Plavnik and Hurvitz,1991).Birds after early life feed restriction have less maintenance requirements due to decrease of heat increment and decrease of basal metabolic rate and specific dynamic action of food (Forsum et al.,1981).In many investigations, compensatory growth have not observed (Summers et al.,1990).It seems administration of Thyroid hormone after feed restriction can induce compensatory growth. The objective of the present study was to investigate the effect of early feed restriction and L-Thyroxin administration after early feed restriction on compensatory growth in broiler chickens.

Cotton is one of the main agricultural crops of Iran. The potential of cottonseed meal (CSM) for poultry nutrition is limited by the presence of gossypol, a toxic polyphenolic pigment. Gossypol exists in CSM in two forms, free and bound. Free gossypol, as defined by AOCS official methods, are those gossypol and gossypol derivatives that are soluble in aqueous acetone and are physiologically active. Bound gossypol is insoluble in ether, chloroform or aqueous acetone and for the most part is physiologically inactive (Berardi & Goldblatt, 1980). The objectives of the experiments reported herein were to study of gossypol reduction by dehydrated ferro sulfate( DFS) and lecithin and also the feeding value of a commercially processed CSM in broiler diets.

In lambs, the rapid increase in heat production after birth is due to initiation of nonshivering thermogenesis in brown adipose tissue (BAT). This occurs in conjunction with an increase in amount and activity of BAT specific uncoupling protein 1 (UCP1) (Clarke et al. 1997). UCP1 abundance and activity is low in fetal life but, within twelve hours of birth, there is an increase in the thermogenic activity of BAT and mRNA for UCP1. This ontogeny of UCP1 mRNA in BAT is very similar that of leptin, which is first detectable in the sheep fetus at 90 days gestation in fetal adipose tissue, its expression then increases up to term at 147 days (Yuen et al 1999). Leptin is a hormone which is thought to play a physiological role is in energy balance, it is primarily produced by white adipose tissue although there is evidence for its production in both brown adipose tissue and the placenta. Lambs born in the autumn are known to be smaller than those born in the spring (McCoard et al. 1997). It is not known if moderate changes in date of mating can influence birth weight or adipose tissue development. The present study aimed to determine whether date of mating could influence lamb birth weight, the abundance of BAT, UCP1, plasma leptin.

A review of published leptin data for growing lambs, older ewes and mature dairy cows in late lactation showed that only 0.30-0.37 of the variation in blood leptin concentration was explained by differences in body fat variably expressed as % of liveweight (LW), backfat thickness and body condition score (BCS) respectively (Wylie et al., 2002). In dairy cows between 15d and 226d postpartum, Wylie et al (2002) observed no overall correlation between leptin at slaughter and lipid expressed as % of LW, empty body weight or carcase weight and only a weak correlation in cows in mid-lactation. Losses of fat during early lactation may ‘uncouple’ the link between leptin and fat and produce a bias across all of lactation. Another explanation is that leptin may be more closely linked with lipogenesis than with the amount of stored fat. This study revisits some metabolite and hormone data from a previous investigation of IGF-1 changes in fed, fasted and re-fed sheep in the light of more recently obtained leptin concentrations in the same animals.

Scrapie is an ovine sub-acute transmissible spongiform encephalopathy (TSE) caused by unconventional transmissible agents. In several species, TSE are associated to major endocrinopathy, such as hyperinsulinemia and hypercorticism (Carp et al, 1990, Gayrard et al, 2000). Cachexia is commonly observed in the clinical phase of the prion disease. Our objective was to investigate if scrapie is associated to alterations of GH axis, leptin, insulin and metabolic parameters. In addition, central adrenergic system being affected in TSE (Braun et al, 1999), we investigated a possible alteration of α2-adrenergic control of GH axis associated to the prion disease.

The closely related actions of cortisol and leptin (Ahima & Flier, 2000) are involved with appetite, tissue growth and maturation, energy balance and weight deposition so that resistance to either may lead to obesity. In normal weight humans, plasma leptin and cortisol exhibit diurnal variation, peaking during darkness and late afternoon (respectively). In sheep, the literature consensus is that plasma cortisol levels are greatest during daylight. Ovine plasma leptin is also reported to vary in response to photoperiod-driven changes (Bocquier et al., 1998) and such as alterations in voluntary feed intake as daylength changes. Daily circadian patterns, however, are thought to be entrained by the time of daily feed presentation (Marie et al., 2001). The aim of the present study was to investigate the diurnal variation in ovine plasma leptin in unrestrained animals with ad-lib access to hay and water in relation to their plasma cortisol profile over the same period. Remote blood sampling was employed in order to reduce sampling stress that would affect the animals’ plasma physiology.

Leptin is mainly secreted by adipose tissue and plays an important role in body homeostasis and in a great number of physiological functions, particularly in reproduction. Sheep is a seasonal ruminant whose reproductive period is initiated during decreasing day lengths. Leptin expression and secretion have shown to be decreased during short days, independently of adipose cell size, feed intake and ovarian activity (Bocquier et al., 1998). The mechanism by which leptin could be modulated is not well understood (Chilliard and Bocquier, 2000). As nocturnal pineal melatonin secretion is increased during short days, it appears as a potential mediator in the regulation of plasma leptin by photoperiod. The aim of this study was to test this hypothesis by comparing plasma leptin and metabolite concentrations in adult ewes exposed to long days treated (M), or not (LD), with melatonin after 20 and 69 days.

Blood concentrations of leptin, the first of several recently-discovered adipocyte proteins, putatively signal the extent of fat energy reserves to the hypothalamus in mammals and help regulate food intake and reproductive activity (through control of GnRH release). In early post-partum dairy cows, the rapidly increasing milk energy output and slowly increasing feed energy intake produce a negative energy balance (-ve EB) that is met by mobilisation of adipose fat stores and the severity and/or duration of the –ve EB may delay resumption of normal ovarian activity. The objective of the current study was to compare post-partum EB and serum leptin concentration profiles in Holstein-Friesian and Norwegian Red heifers, both of high genetic merit within their breed.

In ruminants plasma leptin is increased with increasing body fatness. Leptin acts on hypothalamus to decrease food intake and increase energy expenditure. It is possible that leptin has a key role in transition from pregnancy to lactation of dairy cows. The objective of the present work was to investigate the pattern of plasma leptin concentration, as well as its relationship with other hormones and metabolites and dairy cow performance.

Blood concentrations of leptin have been associated, to varying degrees, with assorted measures of fat in mammalian species. In ruminants, 0.30, 0.35 and 0.37 of the variation in leptin levels in lambs (Blache et al., 2000), older (2-7 yr) multiparous ewes (Delavaud et al., 2000) and mature, late-lactation, dairy cows (Ehrhardt et al., 2000) was attributed to variation in fat as % of liveweight (LW), backfat thickness and body condition score (BCS) respectively while a strong correlation (R_a2=0.83) between leptin and fat as % of empty body weight (EBW) was found for growing Holstein bull calves by Ehrhardt et al. (2000). The objective of the current study was to determine if leptin could be usefully related to fat in multiparous dairy cows differing widely across stages of lactation.

Leptin is an important hormone for the control of food intake and body weight homeostasis in human and rodents. In ruminants, plasma leptin is positively related to body fatness and energy balance or feeding level (Chilliard et al., 2001) and linked to meat quality determinants such as marbling score (Minton et al., 1998). To our knowledge, no information is available on the effects of the nature of dietary forage on this parameter. The objective of the current work was to examine the effects of replacing maize silage with grass on plasma leptin as well as on the activities of five lipogenic enzymes in perirenal and inter-muscular adipose tissues (AT).

Conjugated linoleic acid (CLA) is a mixture of geometrical and positional isomers of linoleic acid. Health-promoting properties of CLA, which include antioxidant, anti-obesity and anticarcinogenic activities, have been demonstrated in a wide range of animal models (Pariza et al., 2001). Recent studies indicated the CLA has a favorable effect on immune competence in nursery (Bassaganya-Riera et al., 2001) and weaned pigs (Corino et al., 2001). For this reason CLA may be useful in sow nutrition to increase CLA content in colostrum and milk (Bee, 2000). However CLA-fed animals displayed also significantly reduced body fat (Pariza et al., 2001) and this effect may be detrimental to reproductive efficiency in sows per se and for the effects on metabolic hormones as well. Moreover some CLA isomers has been reported to influence leptin gene expression (Houseknacht et al., 1998). The present study examined the effects of dietary supplement of CLA on serum leptin in lactating sows.

Pregnancy and lactation are phases during which major adaptations in maternal metabolism are necessary to meet the requirements of foetal growth and of lactation. Leptin, an adipocyte derived hormone, involved in regulation of energy metabolism, has been implicated in the coordination of these adaptive processes. Similar to monogastric species, increased leptin blood concentrations are reported for sheep at mid-pregnancy when compared to prebreeding, late pregnancy or early lactation (Ehrhardt et al., 2001). In sheep, the changes of leptin concentrations showed no obvious relation with the ability of insulin to promote glucose utilisation (Ehrhardt et al., 2001). With the study presented herein, we aimed to elucidate whether exogenous leptin modulates insulin responsiveness and whether the responsiveness is dependent of the physiological status of the animal. Using specific clamp techniques i.e. glucose infusion studies to quantify insulin secretion and resistance, we compared the effect of leptin application on glucose metabolism in pregnant versus lactating goats.

Leptin is a 16kDa peptide hormone mainly secreted by fat cells to regulate of food intake and energy homeostasis, and to signal the status of body energy stores to the brain (Houseknecht et al., 1998). In ruminant, reducing feedstuffs particle size increases DM intake, particularly if feedstuffs quality is poor, due to a shorter retention time of the particles in the rumen. By-products are included in the ration to supply energy and protein, but they have often a high content of fibre. The by-product fibre has different properties than forage NDF, being characterised by particles of small dimensions and a high density. The aim of this study was to compare the plasma level of leptin in lactating goats fed a traditional silage-based diet or a totally free forage diet, throughout lactation and during the pre and post-feeding state.

The chicken leptin cDNA has been cloned and sequenced (AF012727, AF082500) (Taouis et al., 2001) and in this species, the leptin messenger has been found to be expressed not only in adipose tissue but also in the liver. In mammals, circulating leptin acts through specific receptors (Ob-Rb) located in the region of hypothalamus that regulates feeding behavior and energy expenditure; Ob-Rb have also been identified in the pancreatic ß-cells that produce insulin supporting evidence that leptin directly regulates insulin release (Kieffer et al. 2000). A direct effect of leptin on peripheral target tissues has not yet been demonstrated in chicken. The work was designed to study the effect of recombinant chicken leptin on acetylcholine-induced insulin secretion by isolated perfused chicken pancreas.

Leptin is a signalling factor involved in the regulation of body weight and is synthesised predominantly by adipocytes. In humans, there is a positive correlation between plasma concentration of leptin and body mass index (kg/m_a3) and subcutaneous fat (Considine et al., 1996; Lonnqvist et al., 1995). In vitro adipocytes obtained from women secrete more leptin than those of men (Casabeill et al., 1998). Furthermore, testosterone inhibits the expression of the leptin gene in the rat (Wu-Peng et al., 1999). The aim of this study was to examine whether gender, age and body conformation influenced plasma leptin and thyroid hormone concentrations in the horse. Materials and method Pre-slaughter body weight and height were recorded in a random group of mares (n=5), geldings (castrated males: n=7) and stallions (n=3) destined for human consumption. Their age was estimated by dental examination. Immediately post-mortem, a jugular vein blood sample was collected into a heparinised tube, which was centrifuged at 2500 rpm for 10 minutes. Plasma was stored in liquid nitrogen until analysed for plasma concentrations of leptin and thyroid hormones using human ELISA (DRG Instruments) and RIA kits (ICN Pharmaceuticals Ltd), respectively. Statistical differences between groups were assessed using General Linear Model, Analysis of Variance. Regression analysis was used to determine whether plasma leptin concentration was related to body conformation and age.