@conference {41124,
	title = {Are cattle capable of producing litters of calves?},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {59},
	year = {1999},
	month = {Jan},
	pages = {216-218},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Early embryo survival was examined in recipient heifers following the transfer of either 5 or 15 (Expt 1, N=19), or either 2 or 10 (Expt 2, N=46) in vitro produced embryos transferred into the same uterine horn. In Expt 1, the mean {\textpm} s.e. number of conceptuses per pregnant recipient was 2.5 {\textpm} 0.6 and 10.8 {\textpm} 0.8 (P<0.001) in recipients receiving either 5 or 15 embryos. Overall, 63 {\textpm} 4\% of embryos survived (mean {\textpm} s.d.), with no difference among recipients receiving 5 embryos and examined on Day 15, or receiving 15 embryos and slaughtered on either Day 15 or Day 22 (56 {\textpm} 10\%, 77 {\textpm} 5\% and 68 {\textpm} 5\%, respectively, X{\texttwosuperior} = 3.67, NS). Survival was inexplicably lower on Day 22 in recipients receiving 5 embryos (24 {\textpm} 9\% vs. 69 {\textpm} 4\%, X{\texttwosuperior} = 19.15, P<0.001). Pregnancy rate was similar in heifers receiving either 5 or 15 embryos (9/9 vs. 8/10, X{\texttwosuperior} = 2.01, NS), and the mean {\textpm} se number of conceptuses per pregnant recipient was 2.5 {\textpm} 0.6 vs. 10.8 {\textpm} 0.8, (P<0.001). In Expt 2, embryo survival was 80 {\textpm} 5\% and 73 {\textpm} 2\% (NS), and the mean {\textpm} s.e. number of conceptuses per pregnant recipient 1.6 {\textpm} 0.2 and 7.3 {\textpm} 0.3 (P<0.001) in recipients receiving either 2 or 10 embryos. These preliminary results demonstrate that recipient cattle are apparently capable of supporting large numbers of viable conceptuses (5-15) up until at least the fourth week of pregnancy. Whether these can be maintained to term is yet to be demonstrated, although published evidence suggests that the biological limit may be 5 calves per cow at term. },
	issn = {1176-5283},
	author = {McMillan WH and Peterson J and Thompson J and Pugh PA}
}
