Compensatory growth in runt pigs is not mediated by insulin-like growth factor I.

Abstract

Runt pigs grow more slowly and never reach the same body weight as age-matched littermates. We hypothesized that IGF-I would be reduced in the runts and that postnatal nutrition would alter IGF-I concentration and tissue expression. Runt and control littermates were removed from 20 crossbred sows 20 to 28 h after birth. Tissues were collected from a baseline group (n = 4). The remaining pigs were fed porcine milk replacer at either 70 or 120 g/kg BW for 14 d (n = 8). Feed intake and body weight were measured daily, with plasma samples collected by jugular venipuncture throughout the experiment. Expression of IGF-I mRNA was measured in the liver and gastrocnemius with an RNase protection assay. At d 0, runts were significantly smaller than controls in all measurements, except brain weight. During the 14 d, the relative rate of growth was significantly faster and more efficient in runts than in controls; however, runts never attained the same absolute body weight as controls. Circulating IGF-I was significantly reduced at d 0 but was similar to that in controls by d 2 of feeding. The IGF-I mRNA expression in liver or gastrocnemius muscle was not different between control and runts at d 0 or 14 and was not affected by dietary intake. This study has shown that runt pigs grow in a compensatory manner for at least the first 2 wk of life. However, this growth response does not seem to be mediated by IGF-I.

Identifying the limitations for growth in low performing piglets from birth until 10 weeks of age

“…When expressed in g/day, ADFI of LP piglets was lower when compared with HP piglets. This was also observed by Ritacco et al (1997). They claimed, however, that regardless of their intake level small piglets grow more efficiently than controls, which implies a higher G : F for the small piglets.…”

“…The brain is one of the first organs to mature and has the first priority in normal development (Widdowson and McCance, 1960). Brain sparing, a physiological adaptation mechanism from the foetus to increase the delivery of oxygenated blood to the brain at the expense of other organs, has been studied in animal species such as rats (Desai and Crowtheri (1996)), pigs (Widdowson and McCance, 1960;Ritacco et al, 1997) and in humans (Winick et al, 1970) during periods of maternal nutrient restriction. Our results showed that there were no differences in absolute brain weight between performance groups, indicating that brain development has had priority relative to other organs in LP piglets.…”

Growth and development of adipose tissue and gut and related endocrine status during early growth in the pig: impact of low birth weight

“…The influence of birth weight on TH is controversial in the pig. Although Ritacco et al (1997) found no effect of birth weight on plasma TH concentrations, Bauer et al (2000b) described an increased plasma T 4 concentration in LBW piglets. This was associated with an improved calf muscle blood supply and progressed contractile function.…”

“…By chemical analysis of the whole body at birth, it has been reported that LBW piglets have less fat and protein and more water than their littermates (Rehfeldt and Kuhn, 2006). Even though linear correlations between BWs and various organ weights have been reported, the extent of weight variation differs between the organs examined (Table 1; Widdowson, 1971;Ritacco et al, 1997;Bauer et al, 1998 and2000a;Mostyn et al, 2005; R. D'Inca and I. Le Huë rou-Luron, unpublished data).…”

“…In these animals, IGF-I infusion is able to restore BW and composition to normal . This higher efficiency of IGF-I infusion in LBW piglets can be explained by their lower plasma IGF-I concentration between birth and 3 days of age Ritacco et al, 1997;Schoknecht et al, 1997;Table 4). A positive correlation between birth weight and plasma IGF-I has been reported in many mammalian studies (Thieriot-Prevost et al, 1988).…”