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Description:
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Records of embryo production in Red Brahman donor cows (n=50 ) and F1
recipients (n=531 ) were evaluated from the collection day to the birth of the
embryo produced . The effects of the sire of the donor and the embryo , protocol ,
season -protocol , and body condition of the donor on the total number of good ,
degenerated , unfertilized , and total embryos were evaluated . The number of
donors collected for protocols 1 , 2 , and 3 were 50 , 39 , and 46 respectively . The
production of good transferable embryos , and embryos /collection for protocols 1 ,
2 , and 3 were 171 (4 .6 ) , 152 (4 .6 ) , and 208 (6 .3 ) respectively . The final status
of each recipient was recorded as non -pregnant , resorption , abortion , and live
calf . The model used to analyze pregnancy state was : protocol , embryo stage ,
embryo quality , corpora lutea size , and season . The effects of sire of the embryo ,
season -protocol , protocol , embryo stage , embryo quality , body condition score ,
and corpora lutea size on gestation length and birth weight were analyzed .
Season -protocol affected (P <0 .05 ) the number of degenerated embryos . Mean
number of degenerated embryos were higher (P <0 .05 ) during winter for
protocols 2 and 3 than during other seasons . The ratio for good embryos differed
(P <0 .01 ) by sire of donor .
The final status of recipients was affected (P <0 .01 ) by protocol . The maximum
percentage of live calves and the minimum percentage of non -pregnant
recipients were achieved for protocol 3 . Gestation length differed (P <0 .01 ) by sire of the embryo , season -protocol ,
protocol , and body condition score . Spring -protocol 3 resulted in the shortest
while Fall -protocol 2 resulted in the longest mean gestation length . Calf birth
weight differed (P <0 .05 ) by season -protocol and by embryo quality . The lightest
birth weights resulted from embryo quality grade 2 and from spring -protocol 3 .
These results indicate that using protocols that combine 17 ? ? -estradiol , FSH
and GnRH (protocol 3 ) during the spring in conjunction with selection for sire of
donor can increase embryo production by Red Brahman cows . Use of protocol 3
with donors in the spring , selection of embryo sire for short gestation length and
transfer of quality grade 2 embryos can be used to minimize the incidence of
dystocia in recipients . |