Intergenerational effects of omega-6 fatty acids. 1. The reproductive rate of Border Leicester × Merino ewes is influenced by the diet fed to their dams around conception

The proportion of female lambs was previously higher when Merino dams were fed a diet high in omega-6 (n-6) based on oats and cottonseed meal compared with low in n-6 based on silage around mating. The effect of maternal diet on the reproductive success of the female offspring from these dams has not previously been examined. The aim of the present study was to determine whether the reproductive rate of Border Leicester × Merino ewes was higher when their Merino dams were previously fed a diet high in n-6 compared with low in n-6 around conception. Merino dams were fed diets based on either silage low in n-6 or oats and cottonseed meal high in n-6 fatty acids for ~40 days pre-mating only or 40 days pre-mating and 17 days post-mating in each of 2 years. The reproductive performance (proportion pregnant and fetuses conceived) of their Border Leicester × Merino ewe offspring born in each year was examined at their first mating. Ewe lamb birthweight and fat score at the time of mating was not significantly affected by the diet fed to their dams around mating. The proportion of Border Leicester × Merino ewes pregnant was not different, however the number of fetuses per ewe was significantly (P = 0.002) higher when their dams were fed a High n-6 compared with a Low n-6 diet around mating (1.64 ± 0.05 vs 1.42 ± 0.05 fetuses/ewe pregnant, respectively). The reproduction rate of ewes may be affected by diet fed to their dams in the peri-conceptional period and could be associated with fetal programming.

The effect of copper on the response of lambs to selenium supplementation when grazing a selenium deficient pasture

Two trials were undertaken with lambs grazing selenium deficient pasture to determine if copper would enhance liveweight and fleece-weight responses to selenium supplementation. In the first trial, lambs given selenium or selenium plus copper gained significantly more weight and had higher fleece-weights after 260 days than did control lambs or lambs given copper alone. Copper given alone or together with selenium had no significant effect on liveweight or fleece-weight when compared with control lambs and lambs that were given selenium alone respectively. This finding was confirmed in a second trial when growth and fleece-weights of selenium and selenium plus copper treated lambs were compared and no significant differences found. In both trials copper significantly raised liver copper levels. In selenium supplemented but not in selenium deficient sheep, copper significantly increased blood selenium levels.