Patterns of late embryonic and fetal mortality and association with several factors in sheep1

Dixon, A.B.; Knights, M.; Winkler, J.; Marsh, Debbie J.; Pate, Joy L.; Wilson, Matthew E.; Dailey, R. A.; Seidel, G.E.; Inskeep, E. K.

doi:10.2527/jas.2006-129

Cited by 86 publications

(99 citation statements)

References 53 publications

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“…Further study is thus required to determine if lamb separation and progesterone injections are beneficial in less-fertile ewes. Pregnancy losses between pregnancy assessment and term were consistent with those observed by Dixon et al (2007), who reported that 15% of pregnant ewes spontaneously terminated pregnancy. Cognie et al (1975) observed particularly high levels of embryonic mortality in lactating ewes in spring, and Mavrogenis and Chimonides (1992) reported that abortions were twice as frequent (P < 0.01) in accelerated compared with annual lambing systems.…”

Section: Discussionsupporting

confidence: 75%

Strategies for rapid rebreeding of lactating ewes in the spring

Goff

Notter

Vanimisetti

et al. 2014

Animal

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Rapid rebreeding of winter-and spring-lambing ewes is essential if ewes are to lamb more than once per year, but fertility of lactating ewes is often low and early weaning of lambs may be undesirable in forage-based production systems. Selection to improve fertility in spring matings has been successful and led to development of ewes with a reduced seasonal anestrus. Potential for rapid rebreeding of lactating out-of-season breeding (OOS) ewes was tested in three studies. In Experiment 1, effects of short-term lamb removal on rebreeding was evaluated over 2 years using 71 January-lambing OOS ewes. At an average of 63 days postpartum, 36 ewes had lambs removed for 72 h, and all ewes were joined with rams. Circulating progesterone levels indicated that 74% of ewes ovulated before lamb separation; 91% of ewes mated within 5 weeks of ram exposure, 85% were diagnosed as pregnant and 75% lambed. The average interval between lambings was 225 days. In contrast to results observed in cattle, none of the measured variables was affected by lamb separation ( P > 0.20). Experiment 2 compared rebreeding performance of 24 OOS and 23 St. Croix ewes that lambed in January and averaged 60 days postpartum at ram introduction. More OOS ewes ovulated, mated and became pregnant during the first 21 days of ram exposure (83.3%, 58.3%, and 41.7%, respectively; P < 0.001) compared with St. Croix ewes (26.1%, 0%, and 0%, respectively). After 39 days of ram exposure, pregnancy rates still favored OOS ewes (66.7% v. 39.1%; P = 0.06), but the percentage of ewes that lambed did not differ ( P > 0.20) between OOS (47.8%) and St. Croix ewes (34.8%). In the third study, 34 March-lambing OOS ewes were exposed to rams on May 3 at an average of 40 days postpartum to characterize their reproductive performance. After 39 days of ram exposure, 52.9 ± 8.7% of the ewes had mated, and 38.2 ± 8.5% were diagnosed as pregnant. However, only 20.6 ± 7.0% of the ewes produced viable lambs, suggesting a high level of uterine insufficiency. Spring fertility of lactating OOS ewes in these studies was one of the highest reported in the literature and indicated that selection for fertility in spring mating would improve reproductive performance in accelerated lambing programs. However, exposure of lactating OOS ewes to rams at 30 to 50 days postpartum was associated with high prenatal lamb mortality.

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Section: Discussionsupporting

confidence: 75%

Strategies for rapid rebreeding of lactating ewes in the spring

Goff

Notter

Vanimisetti

et al. 2014

Animal

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“…Little is known about the adverse effects of stress during gestation in farm animals; however, other research confirmed that stress following conception in sheep can result in early embryonic loss and reduced implantation rate (Edey 1966;Dixon et al 2007). Embryonic loss was significantly higher in ewes subjected to environmental stress after mating (Doney et al 1976).…”

Section: Fitness Consequences Of Stress: Follicular Development and Omentioning

confidence: 99%

Influences of the stress endocrine system on the reproductive endocrine axis in sheep (Ovis aries)

Narayan

Parisella

2017

Italian Journal of Animal Science

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The hypothalamic-pituitary-adrenal (HPA) axis and the hypothalamic-pituitary-gonadal (HPG) axis systems are inversely related in humans and animals. Although livestock animals, such as sheep (Ovis aries), tend to be well adapted to their environment, it is known that the livestock production processes subject animals to a multitude of physical and psychological stressful stimuli that have the potential to elevate the HPA axis activity. Chronic stress is one of the major challenges in sheep production, as it is difficult to detect and can result in prolonged dysfunction of the HPA axis, causing downstream negative physiological effects such as immunosuppression, increased susceptibility to disease and reproductive dysfunction. The elevation of HPA axis activity during chronic stress has been suggested as the primary neuroendocrine mechanism underlying the aetiology of reproductive dysfunction in sheep. Research in sheep has demonstrated that glucocorticoids act on the HPG axis at the level of the hypothalamus and hypophyseal portal system to decrease gonadotrophin secretion and at the level of the pituitary gland to reduce responsiveness and sensitivity of gonadotroph cells and their receptors to GnRH. Sheep farming enterprises rely on the breeding efficacy of ewes to optimise lambing percentage and reproductive success in order to ensure a profitable business. This review discusses the influences of the HPA axis on the HPG axis and defines any significant reproductive function consequences caused by stress in ewes and places them into perspective for sheep management and productivity.ARTICLE HISTORY

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“…Excessive rates of embryonic loss and fetal mortality are economically detrimental to the sheep industry, and a portion of this loss can be attributed to progesterone concentrations during pregnancy. Dixon et al (2007) found an increase in complete and partial pregnancy loss at day 25 of gestation in ewes that had less than 2 ng/ml of progesterone. In addition to the work in sheep, a number of studies in cows have determined a positive relationship between plasma progesterone concentrations and retention of pregnancy (Starbuck et al, 2004;Larson et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Concomitant changes in progesterone catabolic enzymes, cytochrome P450 2C and 3A, with plasma insulin concentrations in ewes supplemented with sodium acetate or sodium propionate

Lemley

Koch

Blemings

et al. 2008

Animal

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Progesterone is essential for maintaining pregnancy, and several authors have suggested that low peripheral concentrations of progesterone may be responsible for high rates of embryonic loss. The primary organ involved in the catabolism of progesterone is the liver, and cytochrome P450 2C and 3A sub-families account for a large proportion of this catabolism. Elucidating a mechanism to decrease progesterone catabolism, thereby increasing embryonic and uterine exposure to progesterone, seems a logical approach to ameliorate high rates of embryonic loss. The objectives of the current experiment were to determine the pattern of insulin secretion after supplementing feed with either sodium acetate or sodium propionate and to determine any association between the differential patterns of insulin secretion with the hepatic activity of cytochrome P450 2C and 3A and progesterone clearance. Sixteen ovariectomized ewes were fed 3 kg/day for 10 days of a diet consisting of 50% corn silage, 38% triticale haylage, 12% soybean meal and 600 ml of 3.5 M sodium acetate (energy control; n 5 8) or 2.0 M sodium propionate (gluconeogenic substrate; n 5 8). Equal portions of the ration (1 kg as-fed basis along with 200 ml of 3.5 M sodium acetate or 2.0 M sodium propionate) were offered three times daily at 0600, 1400 and 2200 h. Concentrations of insulin in plasma were determined immediately before feeding and at 15, 30, 60, 90, 120, 180, 240 and 300 min after feeding. Progesterone clearance from peripheral circulation (ng/ml per min) was measured by giving a 5 mg injection of progesterone into the left jugular vein and collecting blood via the right jugular vein at 0, 2, 4, 6, 8, 10, 15, 20 and 30 min afterwards. Liver biopsies were taken 1 h after feeding to determine cytochrome P450 2C and 3A activities. Insulin concentrations in ewes supplemented with sodium propionate were elevated at 15, 30 and 60 min after feeding compared to the sodium acetate group. Cytochrome P450 2C and 3A activities were decreased 1 h after feeding in the sodium propionate-treated ewes relative to sodium acetate. Insulin appears to down-regulate cytochrome P450 activity, which could be used to decrease the catabolism of progesterone during early gestation, thereby increasing peripheral concentrations of progesterone and, consequently, embryonic exposure to progesterone.

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Patterns of late embryonic and fetal mortality and association with several factors in sheep1

Cited by 86 publications

References 53 publications

Strategies for rapid rebreeding of lactating ewes in the spring

Strategies for rapid rebreeding of lactating ewes in the spring

Influences of the stress endocrine system on the reproductive endocrine axis in sheep (Ovis aries)

Concomitant changes in progesterone catabolic enzymes, cytochrome P450 2C and 3A, with plasma insulin concentrations in ewes supplemented with sodium acetate or sodium propionate

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