- Animals: sheep
- Animal Production: general animal production
- Education and Training: extension
Lamb losses before weaning and increased labor around lambing time increase financial burdens and anxiety for sheep farmers. Understanding the biology of maternal behavior can help improve lambing time management and reduce stress. Ewes with higher levels of estradiol display better maternal behavior, while cortisol levels are increased at parturition in ewes showing decreased lamb grooming. This project will use 24 artificially-reared (having received little or no maternal care) ewes and 24 naturally-reared ewes. Each of these groups will be half (12 ewes) first-time lambers and half experienced ewes. Prior to breeding, frequent blood samples will be taken to determine baseline estradiol and cortisol and then, after dog stress, to measure elevated cortisol. These ewes will be bred and blood samples again taken prior to and following lambing. Behavioral measures of maternal care will be obtained from video recorded immediately following parturition. Ewes that were artificially reared should show increased cortisol responses to dog stress and to the stress of parturition, and should show corresponding deficits in maternal grooming. Positive correlations are expected between maternal grooming and estradiol levels both before breeding and immediately prior to parturition, while a negative correlation with grooming is expected with regard to cortisol levels, confirming previous work in other breeds. By better understanding the relationship between maternal care, estrogen, and cortisol, I hope to be able to better equip sheep and goat farmers to maximize the maternal input from their dams and encourage their dams to shoulder more of the burden at birthing time.
Project objectives from proposal:
1. To examine the relationship between circulating estradiol levels, estradiol-to-progesterone ratios (E2:P4) and cortisol responses to acute stress in non-pregnant ewes for nulliparous (not previously lambed) and multiparous ewes artificially-reared or ewe-reared as lambs.
2. To confirm the relationship between immediate maternal care in parturient ewes with circulating estradiol and E2:P4 levels, and acute cortisol response to parturition.
3. To compare the levels of maternal care for artificially-reared and ewe-reared ewes within primiparous (first time lambers) and multiparous ewe groups and to determine if these relationships are related to concentrations of estradiol, E2:P4 levels, and cortisol both prior to breeding and at parturition