Effect of maternal mineral supplementation with calcium and magnesium on immune response and energy regulation of ewes and their lambs

Metabolic disorders like hypocalcaemia and pregnancy toxaemia cause major production loss for the Australian sheep industry. These disorders occur due to a deficiency in feed base and pasture. High requirements of ewes to minerals such as calcium (Ca) and magnesium (Mg) at late gestation and early lactation for fetal growth and colostrum/milk production make ewes vulnerable to metabolic disorders. It has been shown that Ca and Mg are vital for a number of physiological processes in improving energy regulation and boosting immune system. The aim of this PhD study was to evaluate the effect of Ca and Mg supplementation on mineral profile, immune response and energy profile of pregnant ewes and their lambs. A series of experiments were conducted such as a pilot trial from two weeks before lambing to 4 weeks after lambing which was followed by another study at which ewes received a long-term supplementation with Ca and Mg from one month before lambing to one month post lambing. In another study, the effect of Ca and Mg was investigated in ewes grazing on barley forage from lamb marking to weaning. Blood, urine and milk samples from ewes and blood from lambs were collected to investigate the effect of mineral supplementation. The findings of this PhD study showed that supplementation with Ca and Mg improved ewes metabolic status. The regulation of energy in ewes supplemented with Ca and Mg was more efficient than unsupplemented ewes. Ewes in this study underwent a period of immune suppression from one week before lambing to lambing which make ewes more susceptible to infection. There was a decreased in leukocyte function and total oxidant capacity in blood of ewes at these time points. However, supplementation of ewes with Ca improved their immune responses which has many implication on the reproductive performance of ewes.The efficiency of immune responses in lambs born from supplemented mother was greater which has many impacts on their future life. Long-term maternal supplementation improved weight gain of lambs at marking. Lamb weight at around lamb marking is an important factor affecting weaning weight which might cause an early weaning occur. Early weaning may be a good strategy to increase productivity and also to make sure that ewes have a greater period to rest and recover their body condition. The effect of mineral supplementation on energy regulation was further investigated by evaluating the effect of mineral supplementation on the expression level of genes regulating energy balance. This study indicated that high energy demands of twin-bearing ewes at late gestation imposed an increase in the expression level of genes mediating energy balance. It is concluded that supplementation of ewes with Ca and Mg at gestation and lactation can improve the immunity and energy balance of ewes and their lambs.