Effect of long-term administration of human growth hormone-releasing factor and (or) thyrotropin-releasing factor on hormone concentrations in lactating dairy cows

1991 ◽  
Vol 8 (1) ◽  
pp. 99-108 ◽  
Author(s):  
P. Lacasse ◽  
D. Petitclerc ◽  
G. Pelletier ◽  
L. Delorme ◽  
J. Morisset ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Dairy Cows ◽  
Human Growth Hormone ◽  
Human Growth ◽  
Growth Hormone Releasing Factor ◽  
Lactating Dairy Cows ◽  
Term Administration

EFFECT OF A GROWTH HORMONE-RELEASING FACTOR ANALOG ON GROWTH HORMONE, INSULIN-LIKE GROWTH FACTOR 1 AND MILK PRODUCTION IN DAIRY COWS

1990 ◽  
Vol 70 (2) ◽  
pp. 525-535 ◽  
Author(s):  
H. LAPIERRE ◽  
G. PELLETIER ◽  
D. PETITCLERC ◽  
P. GAUDREAU ◽  
P. BRAZEAU ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Growth Factor ◽  
Dairy Cows ◽  
Milk Production ◽  
Human Growth Hormone ◽  
Block Design ◽  
Human Growth ◽  
Insulin Like Growth Factor ◽  
Growth Hormone Releasing Factor ◽  
Releasing Factors

In a first experiment, 21 cows (98 d in lactation, 609 kg BW) were randomly used to determine the dose-response release of growth hormone (GH) to [desamino-Tyr1, D-Ala2, Ala15] growth hormone-releasing factor (1–29)NH2 analog (GRF-A; 0, 0.12, 0.37, 1.11 and 3.33 μg kg−1 BW) or to human growth hormone-releasing factor (1–29)NH2 (GRF; 3.33 and 10.00 μg kg−1 BW) after s.c. administration. The interaction (P < 0.01) between the two releasing factors and the doses on GH concentrations indicated that the analog was more potent than the original molecule; at the 3.33 μg kg−1 BW dose, the analog elicited a 3.5 times higher GH response than GRF. In a second experiment, the effects of daily s.c. injections for 10 d of either saline, GRF (10 μg kg−1 BW) or GRF-A (0.6 or 1.8 μg kg−1 BW) on GH concentrations and lactational performance were determined using 32 cows (n = 8 per treatment) averaging 91 d in lactation and subjected to a random block design. The three releasing factor treatments similarly increased GH concentrations measured during the 8 h following the injection on d 1 and 10. GRF at the dose of 10 μg kg−1 BW and the analog at the doses of 0.6 and 1.8 μg kg−1 BW increased milk yield by 9.6, 11.7 and 17.6%, respectively, when compared to the control; both releasing factors had no effect on milk composition. Insulin-like growth factor I concentrations were increased 8 h after the last injection, from 73.4 ng mL−1 in control cows to an average of 107.6 ng mL−1 in treated cows. Results show that the [desamino-Tyr1, D-Ala2, Ala15] human growth hormone-releasing factor (1–29)NH2 analog is more potent than human growth hormone-releasing factor (1–29)NH2 in stimulating GH release and milk production in dairy cows. Key words: Growth hormone-releasing factor, analog, growth hormone, milk production, insulin-like growth factor 1, cows (dairy)

EFFECT OF TWO-MONTH TREATMENT WITH GROWTH HORMONE-RELEASING FACTOR ON GROWTH HORMONE RELEASE IN DAIRY COWS

1988 ◽  
Vol 68 (3) ◽  
pp. 731-740 ◽  
Author(s):  
H. LAPIERRE ◽  
G. PELLETIER ◽  
D. PETITCLERC ◽  
P. DUBREUIL ◽  
J. MORISSET ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Dairy Cows ◽  
Human Growth ◽  
Initial Study ◽  
Dose Effect ◽  
Hormone Release ◽  
Growth Hormone Releasing Factor ◽  
Gh Secretion ◽  
Lactating Dairy Cows ◽  
Key Words Growth Hormone

Two experiments were conducted to examine the effect of a human growth hormone-releasing factor fragment (hGRF(1–29)NH2) on growth hormone (GH) secretion in lactating dairy cows. An initial study was conducted on 12 lactating dairy cows to determine the dose effect (5, 10 and 20 μg kg−1) of a subcutaneous (s.c.) injection of hGRF(1–29)NH2 on GH secretion. The three doses induced similar GH response, with peaks and areas under the curve (AUC) of 38.5, 41.2 and 38.0 ng mL−1, and 3496, 4112 and 4079 ng mL−1 min at 5, 10 and 20 μg kg−1, respectively. In a second study, the GH response after daily s.c. injections of saline (n = 8) or 10 μg kg−1 of hGRF(1–29)NH2 (n = 9) for 57 d was evaluated in dairy cows averaging 252 d in lactation. Blood samples were collected on d 1, 15, 29, 43 and 57 of treatment. On the last day of treatment, the GRF-induced GH peak was higher than on the first day, 46.8 vs. 25.2 ng mL−1, while the AUC was not different, 4010 vs. 2684 ng mL−1 min. Finally, to determine if the pituitary's ability to release GH was modified after 57 d of GRF treatment, the 17 cows were challenged with an intravenous injection of hGRF(1–29)NH2 (1 μg kg−1). Control cows had a lower peak (21.8 vs. 32.2 ng mL−1) but a similar AUC (2190 vs. 2579 ng mL−1 min) than GRF-treated cows. Hence, in lactating dairy cows, (1) s.c. administration of hGRF(1–29)NH2 induced a similar GH release with doses ranging from 5 to 20 μg kg−1 and (2) the GRF-induced GH peak was higher after 57 d of GRF treatment while the AUC was not different. Therefore, 2-mo GRF treatment of dairy cows during their two last month of lactation does not result in a decreased GH response to GRF. Key words: Growth hormone-releasing factor, growth hormone, cows (dairy)

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