Fat mobilization in Pietrain and Large White pigs

Inulin supplementation induces expression of hypothalamic antioxidant defence genes in weaned piglets

Fibre plays an important role in diluting dietary energy density. Fibre is also implicated in the regulation of appetite, perhaps through direct effects in the brain. However, there is little information on this effect in pigs. Therefore, this study was conducted to investigate the effect of fibre type in regulating the expression of genes involved in appetite control, inflammation and antioxidant defence in the hypothalamus of weaned piglets. A total of 64 Duroc × Landrace × Yorkshire barrows at 37 days old were blocked by body weight and allotted to two dietary treatments, supplementation with either 0.25% cellulose (Solka-Floc) or inulin (INU) for 28 days, after which animals were killed for analysis. Pigs fed INU had a tendency (p = 0.06) for reduced feed intake in the first week, although this effect disappeared in subsequent weeks. Pigs supplemented with INU had lower expression of dopamine (dopamine receptor D2), serotonin (5-hydroxytryptamine receptor 1B), free fatty acid (GPR43) and neuropeptide Y receptor Y2 receptors in the hypothalamus (p < 0.05). Expression of the tryptophan hydroxylase 2 gene in the hypothalamus also tended (p = 0.09) to be lower for pigs fed INU. The abundance of antioxidant defence genes, superoxide dismutase (SOD1) and catalase, were greater (p < 0.05) but that of a proinflammatory gene, interleukin 1β, was lower (p < 0.05) in the hypothalamus of pigs fed INU. Therefore, consumption of INU causes downregulation of inflammation in the hypothalamus and regulation of the abundance of serotonin or dopamine receptors, and may also increase antioxidant defence through upregulation of SOD and catalase in weaned piglets.

Granadina kid goats v. Segureña lambs: food intake and performance during milk feeding from birth to 60 days

The morphological development of the sheep and the goat is different and this difference is manifested from early post-natal life. The main characteristic of kid goat carcasses is their low adipose tissue, and this is considered detrimental to quality. In an attempt to determine the nutritional causes of this, a study was performed with kid goats of the Granadina breed and lambs of the Segureña breed. Six kid goats and six lambs were slaughtered at birth, while a further eight kids and eight lambs were fed a milk replacer to satiety until the 60th day of life and slaughtered on the 61st day. Dry matter (DM) and metabolizable energy (ME) intakes and apparent digestibility of energy were determined in four balance periods between 8 and 60 days of life. From the intakes of ME and comparative slaughter data it was possible to calculate energy retention (ER), heat loss (HL) and energy retained as protein (ERp) and as fat (ERf) for kids and lambs. Kid goats showed a similar apparent digestibility of energy to lambs but had lower DM and ME intakes per kg metabolic body weight (M0·75) than lambs. For kids and lambs respectively these values were: 0·93 and 0·94; 45·4 and 50·1 g/kg M0·75 per day; 937 and 1033 kJ/kg M0·75 per day. Mean values for ER, HL, ERp and ERf rates were: 263, 674, 131 and 132 kJ/kg M0·75 per day for kid goats and, 343, 690, 132 and 211 kJ/kg M0·75 per day for lambs. Together with the different intake, kid goats showed a lower rate of ER and overall, a lower rate of ERf than lambs.

Chemical and dissected composition changes in weaned piglets

Twenty-four pigs were weaned at 21 days of age and given restricted feed allowances for the subsequent 8 days. Eight suckled pigs served as control and gained 320 g daily, of which approximately 40 g were lipid and 40 g protein. Pigs were slaughtered at 2-day intervals, physically dissected into non-carcass, carcass fatty tissue and carcass muscle plus bone, and these fractions were then analysed for water, protein and lipid. On average, weaned pigs made small positive body-weight gains. In comparison with suckled pigs, weaned pigs contained more water and less lipid but the same protein, and more non-carcass and less carcass fatty tissue but similar carcass muscle plus bone. Losses of lipid were offset by gains of water and associated with an increase in the percentage water content of carcass fatty tissue. At zero weight gain, pigs lost 43 g carcass fatty tissue, gained 37 g non-carcass, lost 56 g lipid and gained 53 g water, while carcass muscle plus bon e and protein gains were themselves not significantly different from zero. No change in carcass fatty tissue weight was associated with counterbalancing losses of lipid (18 g) and gains of water (15 g) and protein (3g). Lipid catabolism to support anabolism of essential body tissues commenced in the weaned pigs when weight gains fell below 193 g/day; this was about two-thirds of the gains achieved by the suckled control pigs. Plasma free fatty acid concentrations indicated that maximum lipid catabolism to occur on the 2nd day after weaning, and to reduce thereafter as body fat stores were progressively depleted.

The contribution of fat mobilization to the regulation of fat deposition in growing Large White and Piétrain pigs

The contribution of fat mobilization to the regulation of fat deposition was investigated in intensively fed, rapidly growing pigs of the breeds Large White and Pietrain. The results indicate that no quantitative differences in fat mobilization parameters existed between the breeds. In both breeds the concentration of non-esterified fatty acids i n blood serum, measured 8h after a meal, was very low, and the fatty acid composition of the non-esterified fatty acids did not reflect the variation in fatty acid composition of the body fat that existed between groups of pigs within each breed. Additionally, the fraction of body fat that was mobilized per day was calculated to be zero for both breeds. It is concluded from these results that the observed differences in fat deposition between Large White (195g/day) and Pietrain (130g/day) were definitely not the consequence of fat mobilization.

Energy metabolism during late gestation and lactation in multiparous sows in relation to backfat thickness and the interval from weaning to first oestrus

Ten crossbred, fourth or fifth parity sows were divided into 2 groups - high (H) and low (L)- according to their backfat thickness 9 days before parturition. Body weight, backfat thickness and litter weight were recorded repeatedly during a 5 week lactation period. The length of the interval from weaning to first oestrus was also noted. All sows were fed a commercial diet (11.9 MJ/kg, 14.5% crude protein). During gestation, daily food intake was 2.2 kg/sow, while during lactation it was 3.0 kg/sow plus 0.4 kg/piglet. Blood samples were drawn on day 9 before parturition and on days 2, 7, 14 and 21 of lactation. The samples were analysed to determine concentrations of glucose, urea nitrogen, creatinine, triglycerides, free fatty acids and beta-hydroxybutyric acid. In both groups, concentrations of free fatty acids and urea nitrogen were low on day 9 before parturition while those of triglycerides were high, indicating anabolism regardless of backfat thickness. During the first week of lactation, concentrations of free fatty acids increased in the H-group but not in the L-group, and concentrations of urea nitrogen were higher in the H-group. These differences, together with the greater loss of weight observed in the H-group, indicate that catabolism of maternal fat and protein depots was more pronounced in the H-group than in the L-group during this time. On day 14 of lactation, both groups showed equally low concentrations of free fatty acids, decreasing creatinine concentrations and stable triglyceride and urea nitrogen concentrations. Furthermore, weight loss during the second and third weeks of lactation was low in both groups. These facts, taken together, indicate that the catabolic rate was decreasing in both groups during this period. No differences in return to oestrus interval were noted between the groups. The present study indicates that under a restricted feeding regime the catabolic rate during the first week of lactation is higher in sows with higher backfat thickness in late gestation. As lactation progresses, a more balanced metabolism is achieved regardless of backfat thickness, which may tend to reduce differences in return to oestrous interval.

Acute metabolic effects of adrenergic agents in swine

A pig model in vivo was used to confirm the unique specificity for stimulation of porcine adipose tissue lipolysis by norepinephrine analogues in vitro. Plasma free fatty acid and blood glycerol concentrations were monitored as probable indicators of adipose tissue lipolysis. Plasma glucose and lactate concentrations, blood pressure, and heart rate were monitored also. Norepinephrine analogues were infused intravenously. Several compounds, classified as either beta 1- or beta 2-adrenergic agonists, that stimulated lipolysis in vitro also increased plasma free fatty acid and blood glycerol concentrations in vivo. Tazolol (beta 1) and quinterenol (beta 2) did not stimulate lipolysis in vitro and likewise did not elevate plasma free fatty acid or blood glycerol concentrations in vivo. Clenbuterol and zinterol did not stimulate lipolysis in vitro but elevated plasma free fatty acid concentrations in vivo, implying indirect effects. Isoproterenol stimulation of plasma free fatty acid and blood glycerol concentrations in vivo was antagonized by propranolol, implying the beta-adrenergic nature of the receptors. Infusion of purported beta 1- and beta 2-adrenergic antagonists suggested control of lipolysis in vivo predominantly by beta 1-adrenergic receptors; however, because the results in vitro do not indicate this specificity, differential pharmacodynamics of the antagonists are suggested rather than designation of receptor subtypes. There was no evidence for alpha-adrenergic mediated inhibition of adipose tissue lipolysis in vivo, confirming observations in vitro.

Adrenergic control of lipolysis in swine adipose tissue

Most potential adrenergic compounds did not stimulate lipolysis in swine adipose tissue slices. Most of the sympatholytic agents antagonized lipolysis. Most beta 1- and beta 2-adrenergic agonists were not active but many were active with rat adipose tissue. Catecholamines (epinephrine, norepinephrine and isoproterenol), the resorcinol containing beta 2-agonists (terbutaline, metaproterenol and fenoterol) and the beta 1-agonist, dobutamine were active. The beta 1-antagonists were generally more potent and efficacious than the beta 2-antagonists. The swine adipose tissue adrenoceptor was not readily classified as either beta 1- or beta 2-specific.

Glucagon and tolbutamide as insulin secretagogues in the pig (Sus domesticus)

1. Glucagon tolbutamide, either alone or in combination, were injected i.v. into pigs and the effect upon plasma glucose and insulin concentrations measured. 2. Glucagon gave similar insulin responses to those seen in humans, but insulin responses to tolbutamide were less than in humans. 3. Combined doses of glucagon and tolbutamide gave similar, though reduced, responses to those seen in humans. At the highest combined doses applied, glucose concentration remained reduced for up to 6 hr. The insulin responses were approximately equal to the sum of the responses to each substance given alone.

The effect of chronic neonatal guanethidine treatment on body composition in pigs

The effect of neonatal guanethidine administration (30 mg/kg/day) during the first 32 days of life on body composition at 20 weeks of age, was assessed in two breeds of pig which were known to differ in their sympathetic responsiveness. Guanethidine administration increased the proportion of fat and decreased the proportion and absolute weight of lean in the Pietrain breed; and it had no effect in Gloucester Old Spots. Thus it can be inferred that endogenous noradrenaline is responsible for promoting leanness in a pig breed with known sympathetic overactivity.

Autonomic and non-autonomic control of cardiovascular function in stress-sensitive pigs

The T-wave characteristics, heart rate, stroke volume, cardiac output and blood pressure were examined in acidosis-prone Pietrain and acidosis-resistant Gloucester Old Spot pigs, before and after autonomic blockade with propranolol, atropine and phentolamine. Assessments were made at normal arterial blood pH and pCO2, and at either the same age or live weight in the two breeds. T-wave amplitude was influenced by alpha-adrenergic activity in the absence of beta-adrenergic and parasympathetic receptor activation. The initial cardiac output was 25% greater in the Pietrains, and 75% of this breed difference was due to autonomic factors. Myocardial chronotropic responsiveness to noradrenaline was similar in the two breeds. Initial blood pressure was greater in the Gloucester Old Spots because of a non-autonomic factor, and vasopressor responsiveness to noradrenaline was greater in the Gloucester Old Spots. Although acidosis-prone pigs may be afforded some degree of protection from a sympathetic crisis by having a low vasopressor responsiveness to adrenoreceptor stimulation, enhanced catecholamine output is the likely cause of their stress-induced myocardial lesions. A high catecholamine output may also account for the reduced body fatness in this type of pig.

Autonomic responsiveness in stress-sensitive and stress-resistant pigs

The responsiveness of the autonomic nervous system was studied in twenty-six 140 day old thiopentone anaesthetized lean stress-sensitive Pietrain (P) and fatter stress-resistant Gloucester (G) pigs, using the Valsalva like manoeuvre (VLM), and the i.v. tyramine, noradrenaline (NA) and phenylephrine tests. The heart rate responses to the VLM and tyramine tests were greater in P. The pressor response to NA was lower in P, and the change in heart rate per unit change in blood pressure-during phenylephrine infusion was the same in the two breeds. The sympathetic nervous system in P was, therefore, more responsive than that in G, and this was attributable to a higher pre-adrenoreceptor responsiveness in P. The potentially greater sympathetic responsiveness in stress-sensitive pigs could account for their greater leanness, their stress-induced metabolic acidosis, and for their susceptibility to myocardial failure.