Effect of slow-release somatotropin on the pattern of milk yield between and within injection intervals.
Thirty-six Alpine goats (10 primiparous and 26 multiparous) were used to study the milk yield response induced by recombinant bST administered in a sustained-delivery vehicle. Eighteen goats were injected with recombinant bST at 4-wk intervals from about 7 wk postpartum for 12 wk. Patterns of milk yield were highly affected by injection of recombinant bST. Milk yield of treated goats increased from day of injection, peaked between d 3 to 5 after treatment, and then decreased progressively. This pattern of response was well fitted by a curve containing two exponential terms: Yi = A x [exp(-k1di - exp(-k2di)], where Yi = daily relative response of treated goats to recombinant bST, computed as a deviation of least squares means of milk yield at day i (i = 0,..., 26) of the treatment interval from least squares means of milk yield at d 27 of the treatment interval; A = constant; k1 and k2 = response rate parameters; and di = day from treatment (i = 0,..., 27). Administration of recombinant bST also improved persistency of lactation, and the overall milk yield response to exogenous hormone was 300 g/d (13.9%) higher than the yield of untreated goats. This response was due to both the short-term response immediately after injection (53%) and the medium-term effect on lactation persistency.
Gallo
L
L
Department of Animal Science, University of Padova, Legnaro, Italy.
Bailoni
L
L
Schiavon
S
S
Carnier
P
P
Ramanzin
M
M
Andrighetto
I
I
Bittante
G
G
D000818:Animals; D002417:Cattle; D003692:Delayed-Action Preparations; D005260:Female; D006041:Goats / Q000502:physiology*; D013006:Growth Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D007279:Injections, Subcutaneous; D007700:Kinetics; D007774:Lactation / Q000187:drug effects*; D011994:Recombinant Proteins / Q000494:pharmacology
D003692:Delayed-Action Preparations; D011994:Recombinant Proteins; D013006:Growth Hormone