A note on the effect of active immunization against somatostatin on milk production and growth in sheep

Abstract

It has been reported that a purified extract from sheep hypothalami inhibited growth hormone (GH) release in rats. This somatotropin-release-inhibiting factor (SRIF), or somatostatin, is a tetradecapeptide and has been prepared synthetically (Brazeau, Vale, Burgus, Ling, Butcher, Rivier and Guillemin, 1973). In addition, _SRIF has been reported t o inhibit the release of other hormones which have major effects upon growth and metabolism such as insulin (Koerker, Ruch, Chideckel, Palmer, Goodner, Ensinck and Gale, 1974), glucagon (Ruch, Koerker, Carino, Johnson, Webster, Ensinck, Goodner and Gale, 1973) and thyroid stimulating hormone (Vale, Rivier, Brazeau and Guillemin, 1974). Furthermore, SRIF has also been shown to be present in large quantities i n the gastrointestinal tract where it controls the release of many gut hormones (Schusdziarra, Zyzhar and Rouiller, 1980). Somatostatin seems, therefore, to be centrally involved in regulating digestion and absorption of food and the subsequent distribution of the absorbed nutrients into tissues within the body. Its removal from the blood circulation by passive immunization increased GH concentrations in plasma in rats (Arimura and Schally, 1976) and prevented decreases in GH concentration as a result of stress (Arimura, Smith and Schally, 1976). Similarly, removal of SRIF by active immunization has been reported to result in higher plasma GH levels in lambs (Varner, Davis and Reeves, 1980; Spencer, Garssen and Hart, 1983b). However, this increase in circulating GH did not appear to have a constant effect in later studies and resulted in inconclusive effects on sheep growth. Laarveld, Chaplin and Kerr (1986) and Spencer, Garssen and Bergstrom (1983a) observed increased growth with improved food efficiency in crossbred and Dutch moor lambs respectively, immunized against SRIF, whereas Varner et al. (1980) reported a significantly lower growth rate in male Columbia lambs and others (Fitzsimons and Hanrahan, 1984; Galbraith, Wigzell, Scaife and Henderson, 1985; Garssen, Welling and Spencer, 1984) concluded that immunization against SRIF did not affect growth in crossbred lambs. It has also been reported that immuno-neutralization of SRIF can lead to enhanced milk production early in lactation n i goats (Spencer and Garssen, 1985).

Acute or chronic immunoneutralization of somatostatin does not affect growth hormone or thyroid hormone secretion in sheep

“…A significant elevation in basal plasma GH levels (Varner et al 1980) and the GH response to arginine (Varner et al 1980;Spencer et al 1983 ) has been observed in male lambs actively immunized against SRIF. However, as in the current study, active immunization against SRIF failed to increase plasma GH parameters in ruminant animals in many other studies (Spencer & Williamson, 1981;Spencer et al 1983Ä;Laarveld et al 1986;Bass et al 1987;Deligeorgis et al 1988;Vicini et al 1988 ;Mears, 1990 ;Sun et al 1990 ;Trout & Schanbacher, 1990). Laarveld et al ( 1986) and Van Kessel et al (1990) suggested that SRIF immuniza¬ tion may improve growth under cold environmental conditions through an influence on thyroid function.…”

“…Active immunization against SRIF has resulted in improved growth rate (Spencer & Williamson, 1981;Spencer et al 1983 ,/>;Laarveld et al 1986;Deligeorgis et al 1988;Vicini et al 1988;Mears, 1990;Sun et al 1990) in ruminant species, but an elevation in plasma GH has rarely been observed (Varner et al 1980;Spencer et al 1983 ). A thyroid hormone response to SRIF immunization has been observed in neonatal lambs (Van Kessel et al 1990) and has been implicated as a potential mechanism resulting in growth stimulation (Laarveld et al 1986;Van Kessel et al 1990).…”

Effects of Active Immunization against Somatostatin or its Analogues on Milk Protein Synthesis of Rat Mammary Gland Cells

“…Although the level of anti-SRIF antibody was maintained from the late pregnancy till the lactation period, milk protein synthesis did not increase during this period. This result agreed with several studies (Deligeorgis et al, 1988;Yi et al, 1999), which revealed growth performance and/or milk production was not affected by active immunization against SRIF. It appears that several factors including genotype, nutrition, species, and age, influenced the effect of active immunization against SRIF on the milk production.…”

Potential of immunization for increasing animal production

“…Effects on animal growth have been apparently contradictory, several studies reporting increased growth rates, some no effect and even one describing a decreased growth rate in sheep (see Spencer 1987). It has been proposed that the effects may be more pronounced in slower-growing, unimproved breeds and the effects may be greater in females than in males (Deligeorgis et al 1988). GH also stimulates milk production in ruminants and there is at least one report that active immunization against somatostatin increases milk yield in goats (Garssen et al 1987).…”