Ewe nutrition during pregnancy : effects on the development of twin fetuses : a thesis presented in partial fulfilment of the requirements for the degree of Master of AgriScience in Agriculture at Massey University, Palmerston North, New Zealand

Martín, N.P. (2011). Ewe nutrition during pregnancy: Effects on the development of twin fetuses. A thesis presented in partial fulfilment of the requirements for the degree of Master of AgriScience in Agriculture. At Massey University, Palmerston North, New Zealand. This study set out to investigate the effects of dam nutrition during pregnancy on the anatomical development of twin fetuses, with particular focus on the fetal mammary gland. Ewes were fed at 3 different levels in early pregnancy (day 21 to 50, Low (LD21-50) vs. Medium (MD21-50) vs. High (HD21-50)) and 2 different levels in mid- to late-pregnancy (day 50 to 140, Medium (MD50-140) vs. High (HD50-140)). At D140, 58 twin-bearing ewes were euthanised, and dam and fetal organs were collected and weighed. HD21-50 ewes were heavier than LD21-50 and MD21-50 ewes at D50. At D140, HD50-140 ewes were heavier, in better condition score and gained more weight than MD50-140. Ewe nutrition in either period had no effect on the total placental membranes weight, gravid uterus weight, total placentome number or their level of eversion at D140. Nutritional treatments in both early and mid- to late-pregnancy failed to affect fetal weight or general size measurements (crown-rump length, girth circumference, femur or fore-leg length). The semitendinosus muscles from LD21-50-HD50-140 fetuses were heavier than LD21-50-MD50-140 and HD21-50-HD50-140 after adjustment for fetal weight. Fetuses from LD21-50 dams had lighter mammary glands compared to the MD21-50 and HD21-50 fetuses, and these differences remained after adjustment for fetal weight. Maternal nutrition affected other organs and glands, including thyroids, liver, brain and ovaries. The results indicate a critical window of early mammary gland development between days 21 to 50 of gestation, as the fetal mammary glands for the group restricted in early gestation remained lighter, independent of fetal weight or size. A larger cohort of these animals has been kept to monitor their lifetime performance. This work has the potential to change current farming practices and possible review of the fundamentals of human nutrition and health