Hormonal Response of Male Dairy Calves Infused with Growth Hormone-releasing Factor and/or Actively Immunized against Somatostatin

Growth, Feed Digestibility and Carcass Characteristics of Male Dairy Calves Infused with Growth Hormone-releasing Factor and/or Actively Immunized against Somatostatin

“…This effect of SRIF immunization between days 79 and 111 can be explained by the reduced GH, IGF-1 and TSH levels (Roy et al, 1999) observed during this period, and by the lower nutrient intake observed in SRIF-IMM calves during the faecal and urine collection period (days 102-109). Hence, these effects of SRIF immunization on growth and hormone secretion would indicate that the SRIF antibodies raised in these animals might have functioned more as binding proteins than as immunoneutralizing antibodies, thus protecting SRIF from degradation in the blood and thereby enhancing its delivery to SRIF receptor sites (Roy et al, 1999). Nutrient digestibility was not affected by SRIF immunization, which is in agreement with previous results by Vicini et al (1988).…”

“…SRIF antibody titers ranged from 4.5 -39.7% and were significantly higher in SRIF-IMM than in control calves (7.4 vs. 2.0%; SD=1.7; Roy et al, 1999). Half of the animals within each immunization treatment were infused continuously for 32 days (days 79-111) with saline, whereas the other half were infused with hGRF(1 -29)NH 2 (3.33 ng min −1 kg −1 BW) according to a 2×2 completely randomized factorial design.…”

“…The immunization procedure was conducted according to the 1988 guidelines of the Canadian Council on Animal Care. Antibody determination and titers have been reported elsewhere by Roy et al (1999).…”

The early story of growth hormone-releasing factor in rats, swine, and cattle

“…In a companion paper (Roy et al, 1999b), using the same protocol previously described ( 94), the continuous infusion of GRF for 32 days in fast-growing young male steers maintained elevated GH concentrations without affecting IGF-1, TSH, T 4 and PRL concentrations at the end of the infusion period.…”