Concentrations of progesterone in milk of cows administered an intravaginal progesterone insert.

Milk from pregnant cows contains concentrations of progesterone (P4) considered safe for human consumption. The objective of this study was to determine if concentrations of P4 in milk during administration of an intravaginal progesterone insert (CIDR insert) are less than concentrations of P4 in milk associated with pregnancy. Results have implications for human use of milk from cows receiving CIDR inserts. Holstein cows (N = 64; > 40 and < 150 d after calving) were administered 25 mg of PGF2alpha i.m. (study d 0) and 20 cows detected in estrus from 2 to 4 d later were assigned randomly to either control (N = 10; no further treatment) or CIDR insert (N = 10; 1.38 g of P4) inserted on study d 17 (14 +/- 1 d after estrus) and removed 7 d later. Composite milk samples were collected contemporaneously from each of the 20 estrous cycling cows and from 10 pregnant cows (> or = 60 and < or = 220 d of gestation) twice daily from study d 17 to 27. Concentrations of P4 in defatted milk samples were quantified using a validated radioimmunoassay. Mean logs of areas under the curve of concentrations of P4 from the afternoon on study d 17 through the afternoon on study d 27 were 3.05 ng day/ml for control, 3.33 ng day/ml for CIDR insert, and 3.81 ng day/ml for pregnant cows. Therefore, increased P4 due to pregnancy was 0.76 ng day/ml (3.81-3.05), whereas the increase in P4 due to CIDR insert was only 0.28 ng day/ml (3.33-3.05). Applying a 95% confidence interval to 0.28 ng day/ml provided an upper value of 0.70 ng day/ml, lower than the increase due to pregnancy. Because milk from pregnant cows is considered safe for human consumption, it follows that milk from cows administered CIDR inserts should also be considered safe, based on concentrations of P4.

Milk yield, health, and reproduction of dairy cows given somatotropin (Somavubove) beginning early postpartum.

Cows (n = 210) were assigned to the following treatments: uninjected controls through 130 d postpartum; zero to high, uninjected through 60 d then injected with 14 mg of bST/d from 61 through 130 d postpartum; low, 5 mg of bST/d from 14 through 130 d postpartum; low to high, 5 mg of bST/d from 14 through 60 d then 14 mg of BST/d from 61 through 130 d postpartum; and high, 14 mg of bST/d from 14 through 130 d postpartum. Cows given 5 mg of bST/d (low and low to high treatments) yielded 1.2 kg of FCM/d more and high group cows yielded 1.3 kg of FCM/d more than control cows between 14 and 60 d postpartum. Cows given bST yielded 2.7 to 4.1 kg of FCM/d more than control cows during 61 to 130 d postpartum. Overall, control cows yielded 35.1 kg of FCM/d, and bST-dosed cows yielded 2.2 to 3.2 kg/d more FCM. Low group cows had improved pregnancy rate (80.0%) and conception rate (82.2%) compared with high group cows (57.2 and 60.3%). Neither pregnancy (70.0%) nor conception rates (71.5%) of controls differed from other groups. However, low group cows had first service conception rate of 57.8% compared with 34.3% for high and 38.2% for low to high group cows. First postpartum estrus was observed in high group cows about 13 to 16 d later than in low and low to high group cows, whereas low group cows came into first estrus 9 d sooner than controls. Cows of high group had lower body condition than controls (2.5 vs. 2.9), but other groups did not differ (2.7 to 2.9) from controls. Health was not adversely affected. Early postpartum bST administration at 5 mg/d increases FCM and, perhaps, reproductive performance of dairy cattle compared with herdmates.

Milk yield of dairy cows receiving somatotropin (somavubove) daily with periodic 14-day interruption.

Thirty multiparous (cows) and 15 primiparous (heifers) lactating Holstein cattle were used in a 112-d study to examine the effects of pattern of administration of recombinantly derived bST on 3.5% FCM yield. Ten cows and 5 heifers each received either no injection (controls), 14 mg of bST daily, or four repetitions of 14 mg of bST/d for 14 d followed by 14 d of no injection (intermittent bST). Because there was an interaction between treatment groups and parity, analyses were performed separately for cows and heifers. All cows and heifers produced more FCM when given bST than controls. Comparing FCM only during the last 7 d of each period of injection for the intermittent bST group with contemporary daily injected cattle indicated that cows produced equivalent amounts of milk at those times, whereas heifers given daily bST produced 3.4 kg/d more than intermittently injected animals. Furthermore, over each of the four repetitive periods, cows and heifers given daily or intermittent bST responded similarly, although heifers given continuous bST produced more FCM than the intermittent group during each of periods 2 through 4. We conclude that daily administration of bST lends itself to dosing termination during established lactation with concomitant decline of FCM; resumption of bST allows milk yields of cows to achieve levels comparable with those prior to short-term interruption.

Degradation of growth hormone releasing factor analogs in neutral aqueous solution is related to deamidation of asparagine residues. Replacement of asparagine residues by serine stabilizes.

The incubation of a solution of the human growth hormone releasing factor analog, [Leu27] hGRF(1-32)NH2 at pH 7.4 and 37 degrees, resulted in extensive degradation of the sample. The major degradation products were identified as the peptides [beta-Asp8, Leu27] hGRF(1-32)NH2 and [alpha-Asp8, Leu27] hGRF(1-32)NH2, produced by deamidation of the Asn8 residue. When tested as growth hormone (GH) secretagogues in cultured bovine anterior pituitary cells, [beta-Asp8, Leu27] hGRF(1-32)NH2 was estimated to be 400-500 times less potent than the parent Asn8 peptide, while [alpha-Asp8, Leu27] hGRF(1-32)NH2 was calculated to be 25 times less potent than the parent Asn8 peptide. Three additional analogs of [Leu27] hGRF(1-32)NH2 containing either Ser or Asn at positions 8 and 28 were prepared and evaluated for their GH releasing activity and stability in aqueous phosphate buffer (pH 7.4, 37 degrees). Based on disappearance kinetics, [Leu27] hGRF(1-32)NH2 had a half-life of 202 h while the other analogs had the following half-lives: [Leu27, Asn28] hGRF(1-32)NH2 (150 h); [Ser8, Leu27, Asn28] hGRF(1-32)NH2 (746 h); and [Ser8, Leu27] hGRF(1-32)NH2 (1550 h). After 14 days, incubated samples of the Asn8 analogs lost GH releasing potency, while the Ser8 analogs retained full potency. The potential for loss of biological activity brought about by deamidation of other engineered peptides and proteins should be considered in their design.

Effects of infusions of various doses of bovine growth hormone-releasing factor on blood hormones and metabolites in lactating Holstein cows.

In two experiments, the effects of i.v. infusions of various doses of bovine GH-releasing factor (GRF) on blood hormones and metabolites in lactating Holstein cows were determined. In experiment 1, cows were infused with GRF (0, 3.125, 6.25, 12.5, 25.0 or 50.0 mg/cow per 24 h) for 24 h. Blood was sampled at -1, 5, 11, 15 and 23 h relative to the start of the infusion. The serum concentration of somatomedin C (SM-C) before infusion was 303 +/- 8 (S.E.M.) micrograms/l. Doses of GRF of between 3.125 and 50.0 mg were equipotent in stimulating (P less than 0.05) SM-C by 1.5- to 2.5-fold. GRF-induced increases in SM-C occurred by 11 h from the start of the infusion. In experiment 2, primiparous cows were infused with GRF (0, 1 or 3 mg/24 h) for 20 days. Blood was sampled for 12 h on days 1, 10 and 19. The 1 mg dose of GRF increased (P less than 0.05) blood concentrations of SM-C (on days 10 and 19) and glucose (on day 19), but did not affect blood concentrations of prolactin, insulin, cortisol, tri-iodothyronine (T3), thyroxine (T4), non-esterified fatty acids (NEFA) or glucose. The 3 mg dose of GRF increased (P less than 0.05) blood concentrations of SM-C (on days 10 and 19), T3 (on days 10 and 19), insulin (on day 19), NEFA (on days 1, 10 and 19) and glucose (on day 19), but did not affect blood concentrations of prolactin, cortisol or T4. We conclude that these data are consistent with the hypothesis that the galactopoietic effect of exogenous GRF in dairy cattle is mediated by increased secretion of GH.

In vitro metabolic degradation of a bovine growth hormone-releasing factor analog Leu27-bGRF(1-29)NH2 in bovine and porcine plasma. Correlation with plasma dipeptidylpeptidase activity.

A bovine growth hormone-releasing factor analog, Leu27-bGRF(1-29)NH2, was rapidly hydrolyzed to Leu27-bGRF(3-29)NH2 when incubated at 0.03 mM with porcine and bovine plasma at 37 degrees C in vitro (t1/2 = 8.4 min and 22.1 min, respectively). The site of cleavage was the same as that reported by Frohman et al. (J. Clin. Invest. 78, 906-913, 1986) for the GRF/human plasma system and was suggested by the authors to be due to the presence of dipeptidylpeptidase IV (DPP-IV) in human plasma. The DPP-IV-like activity of porcine plasma, determined with Gly-Pro-p-nitroanilide as substrate at pH 7.6 was about 2- to 3-fold higher than that of bovine plasma and seems to correlate well with the more rapid degradation of the GRF analog in porcine plasma. The hormone half-life was extended to 83.3 min when Leu27-bGRF(1-29)NH2 was incubated in vitro with bovine plasma in the presence of an equimolar amount of diprotin A (a competitive DPP-IV inhibitor). Dipeptidylpeptidase II-like activity of porcine and bovine plasma (which may overlap with substrate specificity of DPP-IV) was measured with Lys-Ala-beta-naphthylamide and at pH 7.6 was found to be relatively low (3% and 21% of the corresponding plasma DPP-IV activities). Tyr-beta-naphthylamide was hydrolyzed slowly by porcine plasma and not degraded at all by bovine plasma, which suggests that the sequential cleavage from the GRF N-terminus starting with Tyr at position 1 is not dominant.(ABSTRACT TRUNCATED AT 250 WORDS)

Food intake alters the serum growth hormone response to bovine growth hormone-releasing factor in meal-fed Holstein steers.

The hypothesis that endocrine or nutritional factors related to feeding may affect pituitary responsiveness to an acute challenge with bovine GH-releasing factor (1-44)-NH2 (GRF) was examined in steers. In these experiments, either steers were trained to consume their total daily food allotment in a 2-h period (meal-fed) or food was withheld at the normal time of feeding (sham-fed). In the first of three experiments, the serum GH pattern was determined around the time of feeding in meal-fed and sham-fed steers. The temporal GH rhythm in both groups appeared to be synchronized to the time of feeding, with limited pulsatile GH activity occurring 2-3 h after feeding. Baseline secretion of GH and total area under the GH response curve were lower (P less than 0.01) in meal-fed compared with sham-fed steers. In the second experiment, 50 micrograms GRF was injected i.v. in meal-fed steers at -4, -2, 0, +2, +4, +6 and +8 h relative to the time of feeding. The number of steers responding to GRF (53%), the amplitude of the GH peak (15.8 micrograms/l) and the area under the GH response curve (0.6 arbitrary units) were lower (P less than 0.001) after than before feeding (90 +/- 6 (S.E.M.)%, 61.3 +/- 3.2 micrograms/l and 2.0 +/- 0.3 units respectively). Of those steers responding to GRF, the GH response was significantly reduced following feeding compared with before feeding. In the third experiment, 50 micrograms GRF was injected i.v. in sham-fed steers at -4, -2, 0, +4 and +6 h relative to the time of sham-feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Recombinant-DNA-derived bovine growth hormone from Escherichia coli. 2. Biochemical, biophysical, immunological and biological comparison with the pituitary hormone.

Bacterially synthesized, recombinant-DNA-derived bovine growth hormone (r-bGH), prepared as described in the preceding paper in this journal, has been characterized in comparison with pituitary bovine growth hormone (pit-bGH). The characterization criteria include sodium dodecyl sulfate/polyacrylamide gel electrophoresis, automated N-terminal sequence analysis, amino acid composition, isoelectric focusing, reverse-phase high-performance liquid chromatography, ultraviolet absorbance, analysis for free protein thiol, sizing by gel filtration, circular dichroism, radioimmunoassay and biological activity in the hypophysectomized rat weight-gain assay. In every respect the r-bGH appears to be virtually identical to pit-bGH.

Administration of synthetic human pancreatic growth hormone-releasing factor for five days sustains raised serum concentrations of growth hormone in steers.

Serum GH concentrations in steers were examined during extended treatment with synthetic GH-releasing factor(1-44)NH2 (GRF). The results indicate that GRF given as frequent microinjections stimulate and sustain raised serum GH concentrations for at least 5 days in steers. The GH secretory pattern remained episodic and was characterized by a significant increase in the amplitude of the GH pulses without a change in the number of GH pulses per day. In the first of two experiments, young Holstein steers received 0, 0.05, 0.5 or 5.0 mg GRF during a 24-h period as microinjections every 3.75 min. The 5.0 mg GRF/24h dose significantly increased baseline GH, amplitude of GH pulses and area under the GH curve compared with the other treatments. The number of GH pulses/24 h was similar for all doses of GRF. In a second experiment with Holstein steers, administration of 3.6 mg GRF/day for 5 days increased serum GH concentrations throughout the duration of the treatment without altering the temporal GH secretory pattern. The GH response to GRF did not diminish from days 1 to 5 of treatment suggesting that there was no pituitary desensitization.

Growth hormone response of steers injected with synthetic human pancreatic growth hormone-releasing factors.

Four Holstein steers (312 kg) in a 4 X 4 Latin-square design were injected iv with 0, 100, 300 and 1,000 micrograms of a 44 amino acid growth hormone-releasing factor, hpGRF-44 NH2 in Exp. 1. Blood was collected at 20-min intervals from -1 to +6 h. All doses of hpGRF-44 NH2 stimulated an increase in serum growth hormone (GH) concentrations, whereas prolactin and luteinizing hormone concentrations were unaffected. Steers injected with the 1,000-micrograms dose appeared to have a biphasic release of GH that was not observed at the other doses. Amplitude of the GH peak after the 1,000-micrograms dose tended to be higher (P less than .15) than the peak caused by either the 300-micrograms or 100-micrograms dose, and the latter two were similar. Area under the GH response curve increased (P less than .05) with increasing doses of hpGRF-44 NH2. Endogenous episodic secretion of GH resumed within 6 h after injection of 100 micrograms hpGRF-44 NH2, but not after either the 300-micrograms or 1,000-micrograms dose. In Exp. 2, six Holstein steers (352 kg) in a 6 X 6 Latin-square design received an iv injection of 0, 10, 25, 50 and 100 micrograms hpGRF-44 NH2 and 100 micrograms hpGRF-40 OH. Blood was collected at 20-min intervals from -1 to +4 h, with additional samples at 5, 10 and 15 min. Four of six steers responded to 10 micrograms hpGRF-44 NH2, but all of the steers responded to all other doses of hpGRF-44 NH2 and to hpGRF-40 OH.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of bovine growth hormone administered in various patterns on nitrogen metabolism in the Holstein steer.

Understanding the relationship between the components of the growth hormone (GH) secretory pattern and metabolism may provide a basis for designing studies aimed at exploring how to manipulate GH secretion to stimulate protein gains. In a 4 X 4 Latin square design with one additional period to replicate the first treatment period, eight Holstein steers, 195 kg, were assigned to receive the following treatments: 1) 10-day iv infusion (1) of GH; 2) 10 d of six iv pulse injections (P) of GH daily; 3) 10-d combination of infusion and pulses (IP) and 4) controls (C) receiving no injections or infusions. The GH dose was 48 micrograms/kg-1.d-1. Daily feed, total urine and total fecal collections were made for nitrogen (N) determination. Individual samples for d 3 through 6 (collection A) and d 7 through 10 (collection B) were pooled for analysis. Concentrations of GH were determined in blood samples collected on d 10. In collection A, and N metabolism measures were similar among all treatment groups; however, in collection B, treatment of steers with exogenous GH increased the apparent digestion coefficients for dry matter (P less than .01) and dietary N (P less than .01) and also increased the percentage N retained (P less than .01) and the retention of metabolizable N (P less than .05). Metabolic responses were similar among the different patterns of administration. The positive effects on metabolism during collection B not found in collection A were due to length of treatment with GH, as indicated by the fact that none of the measures of metabolism were changed with time in the controls. Serum concentrations of GH were increased (P less than .001) in GH-treated steers compared with controls. These results support the hypotheses that treatment of normal, growing steers with exogenous GH stimulates nitrogen accretion and that pattern of administration does not significantly affect the N response.

Effect of fasting on hormones and metabolites in plasma of fast-growing, lean and slow-growing obese pigs.

Plasma concentrations of glucose, free fatty acids (FFA), insulin and growth hormone (GH) were determined immediately after food removal and then hourly for 24 hours. Blood was sampled from six lean and six obese pigs at 10 weeks of age via indwelling catheters. Plasma glucose decreased but was similar in both pig strains shortly after feed removal; at the end of the 24-hr fast, plasma glucose was higher (P less than .01) in lean pigs. Plasma FFA concentrations were similar in lean and obese pigs and increased five-fold within 24 hr of fasting. Plasma insulin was higher (P less than .05) in obese pigs than in lean pigs immediately after food removal only (21.4 +/- 3.0 vs 9.8 +/- 2.4 microU/ml). Pattern of GH secretion over 24 hr was episodic; average plasma GH was lower in obese pigs than in lean pigs (2.8 +/- .7 vs 9.4 +/- 1.9 ng/ml). In summary, FFA mobilization was similar in lean and obese pigs, GH concentrations were lower in plasma of obese pigs and relative differences in plasma glucose and insulin between pig strains were influenced by time after feed removal.

Effects of high altitude and hypophagia on mineral metabolism of rats.

Electrolyte excretion and balance were compared in meal-eating, adlibitum-fed rats maintained in Denver (1,600 m) and on Pikes Peak (4,300 m) and in meal-eating rats maintained in Denver but pair-fed to the Pikes Peak animals. Most of the changes in excretion and balance at Pikes Peak were attributable to hypophagia. At both elevations, equivalent decrements in mineral intake led to nearly equivalent decrements in mineral excretion. Comparisons of the Pikes Peak and Denver pair-fed animals, however, revealed certain changes that were unique to high altitude. These included a marked and sustained reduction in ammonia excretion over the 13-day period of exposure. The higher elevation also produced an enhanced sodium excretion on day 1 of exposure and a reduced sodium balance over the first 6 days. Potassium balance showed no changes unique to high altitude during the first 6 days on Pikes Peak but was significantly reduced during week 2 of exposure. The urinary sodium:potassium ratio was elevated during the first 4 days at 4,300 m, but this effect was attributable to altitude on day 1 only. Enhanced calcium and magnesium excretions, relative to those observed in the pair-fed rats, were observed over the middle and latter portions of the exposure period. The balance of these two minerals showed no altitude-dependent effects. Chloride and phosphate excretions showed an altitude-dependent reduction during day 1 and week 1 of exposure, respectively. These changes were associated with more positive balances. It is concluded that the altitude-dependent effects on mineral metabolism are largely, if not entirely, attributable to hypocapnia and associated alkalosis.

Neurochemical coding for feeding in sheep and steers.

Feeding responses of sheep and steers were compared following intraventricular injection of alpha-adrenergic agonists and antagonists in 2-hr. tests. In sheep, injection of the alpha-agonist 1-norepinephrine (1-NE) (140-1,120 nmoles) increased feed intakes 288% and 388% compared with intakes following synthetic cerebrospinal fluid. This response was blocked by the alpha-antagonist phenoxybenzamine, whereas the antagonist alone decreased feed intake. The beta-adrenergic antagonist propranolol did not modify the 1-NE response. A purer but weaker alpha-agonist, 1-phenylephrine, also resulted in increased feed intake that was blocked by phenoxybenzamine. In contrast to the feeding responses of sheep, 1-NE caused hypophagia in steers, reducing intakes as much as 58% in 2-hr. tests over doses ranging 42-27,800 nmoles. Phenoxybenzamine blocked the 1-NE-induced hypophagia in steers; when injected alone, it increased feed intakes 181% of control values. Changes in feeding following 1-NE injections are probably not attributable to changes in temperature, fat mobilization, or stupor. The data support the hypothesis of an alpha-adrenergic-coded system for feeding in sheep and for satiety in steers.