Abstract
Simple SummaryAn experiment was designed to determine the effect of diet and type of pregnancy on the mammary gland development, measured by the transcriptional expression of genes involved in angiogenesis and cell turnover/lactogenesis. To that end, twin and single-bearing ewes were fed naturalized pasture or red clover from day −45 pre-partum until day +60 post-partum, taking samples of mammary tissue at day −10, +30 and +60 post-partum. The results showed that the group of twin-bearing ewes fed red clover was the best combination to increase the expression of genes associated to angiogenesis and cell turnover/lactogenesis in the mammary gland.These trials were carried out to determine firstly the effect of diet and type of pregnancy on the transcriptional expression of genes involved in angiogenesis and cell turnover/lactogenesis inside the sheep mammary gland from late gestation to late lactation. Eighteen Ile de France sheep, 8 twin- and 10 single-bearing ewes were alloted into two groups according to their diet, either based on ad libitum naturalized pasture or red clover hay plus lupine from day −45 pre-partum until day +60 post-partum. Samples from diets and mammary glands were collected at day −10 pre partum (time 1), day +30 (time 2) and day +60 post-partum (time 3) and analyzed by qRT-PCR. Additionally, samples from longissimus dorsi muscle were taken from lambs twice, at weaning and 45 days later, to determine the effect of the maternal treatment with regard to diet and type of pregnancy, on the mRNA expression of genes involved in lipid metabolism. The data was processed using the lme4 package for R, and SPSS Statistics 23.0 for Windows®. The results showed that the group of twin-bearing ewes fed red clover showed a higher expression of genes involved in angiogenesis before lambing and in cell turnover/lactogenesis during late lactation, explained by a lamb survival mechanism to delay apoptosis as a way to keep a secretory cells population and boosted by the diet quality, assuring a longer milk production potential during late lactation. Regarding lambs, apparently the maternal diet would influence the transcriptional expression of lipogenic enzymes in the longissimus dorsi muscle after weaning, but further studies are necessary to validate these results. In summary, Twin-bearing ewes fed red clover performed best at increasing the expression of genes associated with angiogenesis and cell turnover/lactogenesis in the mammary gland.
Highlights
Sheep production is mainly based on pastures and faces serious problems regarding lamb survival and growth from birth until weaning, especially in twin-bearing ewes [1], which is in accordance withAnimals 2019, 9, 589; doi:10.3390/ani9090589 www.mdpi.com/journal/animalsAnimals 2019, 9, 589 the physiological negative energy balance present in peripartum [2,3]
It is possible to recognize as angiogenic factors certain proteins like VEGF and their receptors VEGFR1 and VEGFR2, ANGPT1 and ANGPT2, and RTK [7]
The objectives of this study were to determine the effect of diet and type of pregnancy on the transcriptional expression of genes involved in angiogenesis and cell turnover/lactogenesis in the mammary gland of twinand single-bearing ewes fed two diets, and to report the effects on the transcriptional expression of genes involved in the lipid metabolism of lamb muscle after weaning
Summary
Sheep production is mainly based on pastures and faces serious problems regarding lamb survival and growth from birth until weaning, especially in twin-bearing ewes [1], which is in accordance withAnimals 2019, 9, 589; doi:10.3390/ani9090589 www.mdpi.com/journal/animalsAnimals 2019, 9, 589 the physiological negative energy balance present in peripartum [2,3]. It is known that milk production and its persistence are influenced by the metabolic status of the animals [4]. With regard to the synthesis of milk, the microcirculation in the mammary gland provides the necessary nutrients and oxygen for the lactotrophic mammary cells and allows for the removal of metabolites [5]. There are precedents upon which to state that the processes of angiogenesis and cell proliferation normally occurring in the mamary gland during each lactantion are outdated in time. It is possible to recognize as angiogenic factors certain proteins like VEGF and their receptors VEGFR1 and VEGFR2 (which promote proliferation, survival, migration and differentiation of endothelial cells), ANGPT1 and ANGPT2 (the antagonist protein of ANGPT1, being able to induce endothelial cell apoptosis), and RTK [7]. Some proteins associated to cell turnover/lactogenesis are BAX, BCL2, CCND1, IGF1 and its receptor IGF1R, plus the binding proteins IGFBP3 and IGFBP5, TGFB1 and their receptors TGFB1R1 and TGFB1R2, and LPTR [8]
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