Long-Term Growth after Hypophyseal Stalk Transection and Hypophysectomy of Beef Calves

Abstract

Hypothalamic hormones regulate episodic and basal secretion of hormones from the anterior pituitary gland that affect metabolism and growth in cattle. This study focused on long-term growth in young calves subjected to hypophysectomy (HYPOX), hypophyseal stalk transection (HST), and sham operation control (SOC). Cross-bred (Hereford x Aberdeen Angus) and Hereford, and Aberdeen Angus calves were HYPOX (n ϭ 5), HST (n ϭ 5), or SOC (n ϭ 8) at 146 Ϯ 2 days of age, whereas another group was HST (n ϭ 5) or SOC (n ϭ 7) at 273 Ϯ 5 days of age. Body weight was determined every 21 days from birth to 1008 days of age. Anterior vena cava blood was withdrawn at 4-day intervals from day 64 -360 for RIA of GH, TSH, T 4 , T 3 , and LH, and at 20-min intervals for 480 min to determine episodic hormone secretion. Daily feed intake was determined in HST and SOC calves during an 80-day period. Birth weight averaged 35 Ϯ 1 kg (Ϯ SE) and was 142 Ϯ 4 kg at 126 days and 208 Ϯ 8 kg at 252 days before surgery. From day 146-1008, growth was arrested (P Ͻ 0.001) in HYPOX (0.06 Ϯ 0.01 kg/day) compared with SOC (0.50 Ϯ 0.04 kg/day) calves. Growth continued but at a significantly lower rate (P Ͻ 0.05) in calves HST at 146 days (0.32 Ϯ 0.07 kg/day) and 273 days (0.32 Ϯ 0.06 kg/day) compared with SOC (0.50 Ϯ 0.09 kg/day). Growth continued to be impaired to 1008 days, but more so in those HST at 146 days (432 Ϯ 43 kg BW) than 273 days (472 Ϯ 5 kg BW) and less (P Ͻ 0.05) than SOC (586 Ϯ 37 kg BW). Daily feed intake was consistently less (P Ͻ 0.05) in HST compared with SOC calves. Although episodic GH secretion was abolished and peripheral serum GH concentration remained consistently lower in HST (2.4 ng/ml) than SOC (5.5 ng/ml; P Ͻ 0.01), the calves continued to grow throughout 1008 days. Peripheral serum TSH concentration was less (P Ͻ 0.05) HST compared with SOC calves. There was an abrupt decrease (P Ͻ 0.001) in serum T 4 (4-fold) and T 3 (3-fold) concentration after surgery that remained to 360 days in HST compared with SOC calves. At the time calves were killed, pituitary gland weight was markedly reduced (P Ͻ 0.001) in HST (0.18 Ϯ 0.01 g/100 kg BW) compared with SOC (0.54 Ϯ 0.03 g/100 kg BW). Histological examination of pituitary glands from HST calves indicated the persistence of secretory GH and TSH cells in the same areas of the adenohypophysis as SOC calves. Coronal sections of the gland stained with performic acid-Alcian blue-periodic acid-Schiff-orange G, revealed GH and TSH secreting cells in HST calves similar to controls. These results indicate that long-term growth continues, but at a slower rate, after hypophyseal stalk transection of immature calves in spite of complete abolition of episodic GH secretion and consistently decreased basal secretion of GH, TSH, T 4 , and T 3 compared with sham-operated animals. Growth was abolished after hypophysectomy of immature calves in which circulating GH and TSH was undetectable. (Endocrinology 140: [2405][2406][2407][2408][2409][2410][2411][2412][2413][2414] 1999)

Pregnancy, parturition, and lactation in hypophyseal stalk-transected beef heifers

“…In coronal sections of pituitary glands from HST and SOC heifers stained with performic acid-Alcian blueperiodic acid (PAS)-Schiff-orange G, acidophils, basophils, and chromophobes were present. Pituitary and thyroid histology in these HST and SOC heifers was similar to that observed after long-term growth in HST and SOC calves (Anderson et al 1999).…”

Growth Hormone Secretion: Molecular and Cellular Mechanisms and In Vivo Approaches

“…5, A-C; Refs. [102][103][104][105][106]. An interpretation of these observations is that the reduced pituitary GH content reflects depressed GH synthesis due to decreased GHRH stimulation.…”

Protein nutrition of the neonate

“…Irrespective of the species glutamate + glutamine contribute 20 % of total milk amino acids, and 40 % of the total amino Davis et al (1994). Animal growth data: (r), man (Dewey et al 1996); (y), (o), chimpanzee and gorilla respectively (Smith & Leigh, 1998; S Leigh, personal communication); (f), cattle (Anderson et al 1999); (v), sheep (Greenwood et al 1998); (X) rat ; (q), pig.…”