❞ كتاب The Effect of Constant Delivery of Gonadotropin Releasing Hormone on Fertility of Cattle ❝

The Effect of Constant Delivery of Gonadotropin Releasing Hormone on Fertility of Cattle

The Effect of Constant Delivery of Gonadotropin Releasing Hormone on Fertility of Cattle من كتب طب بيطرى

ABSTRACT

Four hundred and three (403) postpartum beef cows,
synchronized with the norgestomet and estradiol valerate
bovine estrus synchronization procedure, were included in
three experiments. In the first experiment, 78 of the
178 cows were administered biodegradable microcapsules
containing 180 pg GnRH manufactured to biodegrade (and
release GnRH relatively constantly) in approximately
three days. In the second experiment, 38 of the 90 cows
were implanted with osmotic pumps designed to deliver 2.5
pg of GnRH per hour for six days. The third experiment
consisted of two trials. In the first trial, 21 of the
41 cows were implanted with biodegradable implants
manufactured to delivery 250 pg of GnRH (relatively
constantly) over a four day period. In the second trial,
46 of the 94 cows were implanted with same implant as in
trial 1 except the implants were coated so that there was
a slight delay in initiating delivery after implantation.
The constant delivery of GnRH during the proestrus period
reduced pregnancy rates when GnRH was administered via
osmotic pumps, microcapsules, and implants. Constant
delivery implants with a delay in release after
implantation, however, had no effect on pregnancy rates.
In summary, constant delivery of GnRH, via all of the
delivery systems, was not considered a valid method of
enhancing fertility in proestrus cattle. . المزيد..