The case for pre-parturient selenium and iodine supplementation of ewes for improving lamb survival

Lamb survival is an issue of high relevance to the Australian sheep industry, as lamb survival rates have direct bearing on overall reproductive performance of the sheep, and also constitute a main concern from an animal welfare perspective (Mellor and Stafford 2004). Both genetic and management factors play an important role in this complex issue (Hinch and Brien 2014). Ewe nutrition is of particular relevance as the intrauterine growth conditions prepare the lamb for the crucial transition to life outside the uterus. Effects of body condition of the ewe during various stage of the pregnancy have been investigated in detail, yet much less is known about the critical role of micronutrient provision to the ewe. Although several risk factors for Se and I subclinical deficiencies exist in Australia, determining micronutrient status in sheep or pasture is not straightforward.