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Miniature Brahman cattle at the USDA ARS Subtropical Agriculture Research Station in Brooksville, FL have normal proportioned growth but are approximately 70% of mature height and weight when compared with Brahman cattle in the same herd. Pedigree analyses suggest that the condition is inherited through a recessive allele. The miniature Brahman cattle in the Brooksville herd have been used for studies of growth and reproduction, but the underlying causative mutation is unknown. Presumably, the miniature condition could arise from a mutation in the GH gene. The objective, therefore, was to clone the GH cDNA from Brooksville miniature Brahman cattle, compare its sequence to normal Brahman cattle, and test the biological activity of the native GH protein. Messenger RNA was isolated from the pituitary, and a cDNA for the protein coding region of the GH gene was amplified by reverse-transcription polymerase chain reaction (PCR) from each of 2 miniature Brahman bulls. The cDNA were cloned into plasmid vectors, and top and bottom strands were sequenced by automated DNA sequencing. The sequence of both cDNA clones derived from miniature cattle differed from Bos indicus GH (GenBank AF034386) at base number 641 because there was a cytosine (C) instead of a thymine (T). The C to T change encoded a mutation (threonine to methionine) at amino acid 200 (T200M mutation). The mutation was confirmed by sequencing of an additional 2 miniature cattle and comparing their sequence to 2 normal cattle. The threonine is located in the fourth alpha helix of GH and is 1 of 8 amino acids that participate in binding of GH to the GH receptor. Twelve miniature Brahman and 9 normal Brahman cattle were tested by using a restriction fragment length polymorphism analysis that employed the BsmBI restriction enzyme (specific for the mutated nucleotide). The 12 miniature Brahman cattle were homozygous for the mutation (-/-). Seven of the normal Brahman cattle were homozygous for the wild-type allele (+/+), and 2 were heterozygous (+/-). When tested in a cell-based bioassay, GH isolated from the pituitary of -/- cattle (n=4) had approximately 60% activity when compared with GH isolated from the pituitary of +/+ cattle (n=5). In summary, miniature Brahman cattle were homozygous for a single nucleotide polymorphism that encodes a mutation in an amino acid involved in binding of GH to the GH receptor. Cattle of normal size had at least 1 copy of the normal GH allele. Threonine 200 in bovine GH is required for normal growth in cattle.

Twelve pregnant Brahman cows were randomly assigned to one of two treatment groups: 1) transported in a stock trailer for 24.2 km, unloaded at a second farm and penned for 1 hr, and then returned to the original farm (TRANS, n = 6); or 2) walked through the handling facilities (SHAM, n = 6). Treatments were repeated at 60, 80, 100, 120, and 140 d of gestation. Calves were delivered by cesarean section on d 266 of gestation. The male:female ratio was 4:2 and 5:1 for the TRANS and SHAM treatment groups, respectively. Before calf removal and severance of the umbilical blood flow, a blood sample was collected from the calf to determine plasma concentrations of adrenocorticotropin (ACTH) and cortisol. The calf was then sedated and exsanguinated, after which pituitary and adrenal glands were collected. The adrenals were immediately weighed, and a cross-section from the left adrenal was stored in 4% paraformaldehyde until being embedded in paraffin. Eight sections from each adrenal were sliced (5 microns), fixed, and then stained with Harris' hematoxylin and eosin. Areas of the cortex and medulla were calculated with a computerized digitizing unit and tracing of the viewed section. The TRANS calves had heavier body weights (BW) (28.7 vs. 23.9 +/- 1.8 kg; P < 0.07), pituitary glands (12.63 vs. 8.24 +/- 1.10 g/kg BW; P < 0.008), and heart weights (5.58 vs. 5.17 +/- 0.58 g/kg BW; P < 0.05) than did the SHAM calves. Plasma concentrations of ACTH and cortisol did not differ between SHAM and TRANS calves (57 vs. 82 +/- 14 pg/ml and 7.0 vs. 6.7 +/- 0.9 ng/ml, respectively; P > 0.2). Adrenal gland weight and medulla-to-cortex ratio did not differ between SHAM and TRANS calves (0.61 and 0.73 +/- 0.03 g and 0.97 and 0.99 +/- 0.12 g, respectively; P > 0.2). These results suggest that the altered response to stress in prenatally stressed calves is not associated with morphological changes in the adrenal gland but may be due to effects of prenatal stress on the fetal pituitary.

The literature indicates that sire breed of calf influences beef calf performance. However, there is little information concerning sire breed of calf effects on reproduction in beef cows. In this experiment, Angus (A), Brahman (B), or Tuli (T) bulls were bred to 136 Brahman (B) cows to examine sire breed of calf influence on peripartum hormone profiles and the length of postpartum anestrus. Cows were bled from 7 d prepartum to 28 d postpartum to determine peripartum hormone concentrations. Cows carrying AB calves had greater (P < 0.05) prepartum estradiol-17 beta concentrations than did cows carrying BB and TB calves. Prepartum and postpartum progesterone concentrations did not differ between cows with AB, BB, and TB calves. Cows with TB calves had lower (P < 0.01) 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) concentrations than did cows with AB and BB calves during the early postpartum period. Adjusting for birth weight removed the sire breed of calf effect on postpartum PGFM concentrations, but not prepartum estradiol-17 beta. Postpartum anestrus was shorter (P < 0.05) for cows nursing BB calves (84 +/- 6 d) than for cows nursing AB (101 +/- 6 d) or TB calves (110 +/- 7 d). Adjustment for estradiol or PGFM concentrations did not reduce sire breed of calf effects on the length of postpartum anestrus. Further work is heeded to determine how calf genotype may modulate the postpartum reproductive function of the dam.

The actions of corticotropin-releasing hormone (CRH), vasopressin (VP), the synthetic glucocorticoid dexamethasone (DEX), and mifepristone (RU 486), a glucocorticoid antagonist, on the secretion of adrenocorticotropin (ACTH) by cultured fallow deer corticotrophs were studied in vitro. On Day 5 of primary culture, corticotrophs were challenged for up to 4 hr with medium alone (Control), CRH, VP, DEX, forskolin (FSK), phorbol ester (TPA), cyclic AMP (cAMP), and/or RU 486 at various concentrations and combinations. CRH, VP, FSK and TPA each stimulated (P < 0.01) the secretion of ACTH in dose- and time-related manners. Relative to Control, CRH at 0.001 and 0.1 microM and VP at 0.01 and 1 microM increased (P < 0.01) medium concentration of ACTH by 7.3-, 13.5-, 3.7- and 9.0-fold, respectively. There was a treatment x incubation time interaction (P < 0.01) such that at 30-min posttreatment, CRH-induced ACTH secretion tended (P < 0.10) to be less than that obtained via VP treatment, whereas at 1, 3, and 4 hr posttreatment, medium concentration of ACTH from cells treated with 0.1 microM CRH was greater (P < 0.05) than that in cells treated with 1 microM VP. At equimolar doses of 0.01 and 0.1 microM, CRH was 3.4- and 3.0-fold more potent (treatment x dose, P < 0.05) than VP. Cotreatment with 1 microM DEX reduced (P < 0.001) the stimulatory effects of CRH (0.1 microM), VP (1 microM), FSK (10 microMs), TPA (0.1 microM), and cAMP (0.001 M). However, the coaddition of RU 486 (1 microM) to the CRH plus DEX- and the FSK plus DEX-treated wells partially negated the inhibitory effects of DEX. RU 486 completely negated the inhibitory effects of DEX on the VP-, TPA-, and cAMP-stimulated secretion of ACTH. These data indicate that CRH is a more potent stimulator of ACTH secretion than is VP in primary culture of fallow deer pituitary cells. This study also demonstrates the utility of an in vitro culture system to investigate stress-related hormonal interactions in cervids.

Twenty-nine prepubertal Holstein heifers were assigned by age to one of three age groups to determine if the prepubertal bovine uterus could respond to an oxytocin stimulus. Group 1 heifers were 6 to 7 months of age (AGE1; n = 11), group 2 heifers were 8 to 9 months of age (AGE2; n = 11) and group 3 heifers were 10 to 11 months of age (AGE3; n = 7). Blood samples were collected via an indwelling jugular catheter. Four samples were collected at 15-min intervals prior to oxytocin administration to determine basal 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) concentrations. Each heifer received 100 IU of oxytocin i.v., blood sampling continued at 5 min intervals for the next 30 min and for an additional 90 min at 15-min intervals. Heifers were considered responders to oxytocin if mean PGFM concentrations increased at least 1.5 times the SD of their basal PGFM concentration. Age of the heifer (P less than .0001) and responder status (P less than .05) affected plasma PGFM. Plasma PGFM was higher in AGE1 and AGE3 heifers than AGE2 (P less than .0001). The number of responders was greatest at AGE3 (P less than .03) with AGE1 and AGE2 being similar. Mean basal PGFM was lower (P less than .04) at AGE2 than AGE1 with AGE3 being intermediate. In addition, basal PGFM at AGE1 tended to be lower (P less than .08) in the responders than in the non-responders, while AGE2 basal PGFM did not differ between responders and non-responders (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)