Research that has found a two-fold difference in the amount of epithelial tissue in the mammary glands of foetal lambs whose dams were well fed throughout pregnancy compared to dams fed at maintenance levels could have important implications for sheep farm management in New Zealand – and perhaps human nutrition.
Catriona Jenkinson, who will graduate with a Doctor of Philosophy in Animal Science from Massey University at the Palmerston North ceremonies next week, says her research highlighted the important role nutrition during pregnancy appears to play in determining the size of the mammary tissues of the female offspring. “Such a difference, if only partly translated into growth of the udder in the mature animal, has considerable practical implications.” This research is contributing to further work on the effect of long-term maternal under-nutrition on mammary gland development of the foetal lamb, its impact on future milk yield and hence, the ability of that lamb, in later life, to meet the energy requirements of her offspring.
Dr Jenkinson says in a mature animal it is the amount of epithelial tissue that dictates the secretory ability of the gland. ”We don’t know what relationship there is between the size of the tissue at birth and the future ability to lactate but a two-fold difference is huge. There has got to be some effect.”
Dr Jenkinson says if there is a relationship between the size of the tissue at birth and subsequent lactational performance, and this is confirmed to be linked to the feed available to the ewe during pregnancy, then New Zealand farmers may need to rethink how they manage their flocks. “Farmers traditionally feed ewes well in late gestation but feed maintenance levels or below during early gestation and mating. Perhaps nutrition at this early stage is more important than we realise.”
She says her work has implications agriculturally and clinically. There is evidence from other studies that restricting the feeding levels of the pregnant ewe differentially influences growth of the foetal lamb and its size at birth. However, until now, there were no data on the effects on foetal mammary gland development. “Most research has tended to focus on the growth of the mammary glands around puberty and pregnancy with the implicit assumption that development of the mammary gland during early life is irrelevant to this later period.”
She also questions the widespread use of the rodent as a model for mammary gland development in the ruminant given the significant differences between the two species in the growth of the gland and its subsequent composition and architecture in adult life. In fact, the developmental pattern for ruminants more closely follows that of humans.
Dr Jenkinson is a postdoctoral fellow with the National Research Centre for Growth and Development, based at Auckland University. She is currently seeking funding for further research to verify her results.
Reducing the mortality rate of new born lambs was the aim of Julie Everett-Hincks PhD research.
Currently lamb death rates cost New Zealand farmers over $600 million annually. And as sheep farmers strive to increase production by lifting lambing percentages, particularly increasing the number of triplet lambs born, it is becoming increasingly important to ensure lambs survive to maturity.
Dr Everett-Hincks researched ways of improving the survival of triplet lambs by investigating the genetics, behaviour and management of the ewe-lamb relationship under commercial farming conditions.
Her research found that triplet lambs require more care as they are constrained by the environment provided by their dam. In particular, triplet lamb behaviour and subsequent survival was affected by maternal nutrition in late pregnancy. “Lambs born to poorly feed ewes were slower to stand, locate their dam’s udder and reunite with the dam after separation. However, triplet survival was similar to twin lamb survival when ewe nutrition was not restricted in late pregnancy.”
“Lamb behaviour has a huge effect on lamb survival. We need to look further at that jointly with ewe behaviour. It appears that feeding levels during pregnancy directly affect lamb behaviour. This has implications for human health also because, Ewes not fed very well in late pregnancy, implications for human.
Dr Everett-Hincks is currently employed at AgResearch Invermay. She will receive her doctorate at Massey University’s Palmerston North graduation ceremonies next week.