Fat mobilization in Pietrain and Large White pigs

Abstract

I .Two experiments were done with Pietrain and Large White pigs (about 50 kg bodyweight) to determine whether fat mobilization is enhanced in the stress-sensitive Pietrains (which also produce pale, soft, exudative (PSE) meat).2. In Expt I , plasma glucose and insulin concentrations and free fatty acid (FFA) concentrations and composition weremeasured in five Pietrains and five Large Whites after feeding, during an infusion of norepinephrine (2.5 yg/kg body-weight per rnin), 16 and 21 h after the withdrawal of food and following insulin administration (0.3 IU/kg body-weight). The entry rate of oleic acid was measured 4 h after feeding. Body composition and longissimus dorsi pH measurements were made on killing the pigs 4 d after the experiment.3. After feeding, the Pietrains tended to have lower concentrations of glucose and insulin in plasma compared with the Large Whites, and higher concentrations of FFA. The Pietrains also had a faster entry rate of oleic acid into body tissues. In fasting (16 h) these differences in hormone and metabolite concentrations were also present and relationships between them and body development could be detected. Pietrains had higher concentrations of FFA and lower concentrations of insulin than Large Whites at a particular stage of the development of fat and muscle (subcutaneous fat weight i longissimus muscle weight).4. The fatty acid composition of FFA resembled that of the backfat triglycerides in fasting and during norepinephrine infusion but not in the fed state. In particular the proportion of fatty acid 18 : I was low in the fed pigs and that of 18 : 2 was high. The contrast in FFA composition between the fed and stimulated state was greater in the Large Whites.5 . The Pietrains were less sensitive to the antilipolytic action of insulin. Glucose and FFA concentrations were similar in both breeds during the norepinephrine infusion although insulin concentrations were increased to a larger extent in the Large Whites at the termination of the infusion. .In Expt 2, anaesthetized Pietrain and Large White pigs were given constant infusions of norepinephrine alone (2.5 ,ug/kg body-weight per min) and norepinephrine 4-propranolol (2, 10 and 20 ,ug/kg body-weight per min) or phentolamine (2 and 10 yg/kg body-weight per min). The aim was to determine whether the breeds differed in their sensitivity to norepinephrine when conscious responses to the hormone were prevented.

Chemical and dissected composition changes in weaned piglets

“…This could have been an adaptive response or, more likely, because the extent of the depletion of the lipid reserves necessitated it. Levels of FFA at 2 days post weaning (800 to 1500/xmol/l) were similar to those observed in starved 50 kg pigs by Wood et al (1977), showing that the young pigs at this stage could mobilize fatty acids as effectively as older pigs. However, by 6 and 8 days post weaning FFA levels were much lower (300 to 600/imol/l) suggesting a progressive failure to mobilize fat as the stores depleted.…”

“…This suggests (in common with Wood et al (1977)) a role for fat catabolism as a normal means of body composition control. Approximately 82% of CFT, 35 % of NC and 24% of CMB was as lipid.…”

“…Regression constants were found to be not significantly different from zero and were suppressed. To assess the extent of lipid catabolism occurring, blood samples (10 ml) were taken from the aorta by venipuncture immediately prior to slaughter and free fatty acid (FFA) concentrations determined by the method of Wood, Gregory, Hall and Lister (1977).…”

Hematological and biochemical changes following an acute stress in control and somatostatin-immunized pigs

“…A decrease in FFA level has been reoorted immediately following stress (Spencer 1980) even though it peaked 60 min after a noradrenaline infusion (Wood et al 1977). …”

Growth as affected by general hormonal factors and hormonal balances, and the limitations of such studies

“…1977). Wood et al (1977) (Ashmore, 1974 Forbes, 1978). However, these fluctuations are less marked than in humans or rats (Wagner and Oxenreider, 1972 ;Trenkle, 1977 ;Trenkle and Topel, 1978).…”