@conference {40605,
	title = {The effects of season on placental development and fetal growth in sheep},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {54},
	year = {1994},
	month = {Jan},
	pages = {227-230},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Autumn-born lambs have been reported to have lower birth weights  
than spring-born lambs by 0.4 to 1.0 kg, but the physiological basis of this  
difference is unknown.  This study examined the effects of season on fetal  
growth and placental development independent of the confounding effects of  
maternal nutrition.  Romney ewes (aged 5 and 6 years) were randomly  
allocated to groups mated in December (n=13) or March (n=13 with a similar  
live weight at mating (55.6{\textpm}1.8 vs 55.7{\textpm}1.9 kg, mean{\textpm}SE, P>0.10) and  
managed for a similar live weight at day 140 of gestation (62.5{\textpm}1.8 vs 62.9{\textpm}1.9  
kg, P>0.10).  At day 140 of gestation, measures of fetal growth and placental  
development, adjusted for litter size, were (December- vs March-mated):  
individual fetal weight (4.15{\textpm}0.16 vs 5.07{\textpm}0.16 kg, P<0.001); total fetal weight  
per ewe (6.42{\textpm}0.18 vs 7.14{\textpm}0.22 kg, P<0.01); caruncle number (114.5{\textpm}4.1 vs  
121.0{\textpm}4.2, P>0.10); placentome number (89.4{\textpm}4.2 vs 106.9{\textpm}4.3, P<0.01);  
caruncle occupancy, i.e. number of placentomes/number of caruncles  
(0.79{\textpm}0.03 vs 0.88{\textpm}0.03, P<0.05); and total placentome weight (564.7{\textpm}34.0 vs  
679.0{\textpm}34.9 g, P<0.05).  These results suggest that seasonal differences in birth  
weight of lambs are mediated not by differences in maternal nutrition but rather  
by a direct seasonal effect on placental size (specifically the formation of  
placentomes and hence total placental weight). 
 },
	issn = {1176-5283},
	author = {Jenkinson CMC and Peterson SW and MacKenzie DDS and McCutcheon SN}
}
