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Submitted to: Meeting Proceedings
Publication Type: Proceedings Publication Acceptance Date: 1/6/2008 Publication Date: 3/20/2008 Citation: Geary, T.W. 2008. Management Strategies to Reduce Embryonic Loss in Beef Cattle. Proceedings XII Course on New Approaches to Production and Reproduction in Cattle, March 6-7, 2008 Uberlandia, Brazil (Portuguese only)CD only. pg 51-60. Interpretive Summary: There are no “silver bullets” for eliminating embryonic mortality in beef herds. This paper describes early pregnancy and some of the factors involved and likely causes of embryonic mortality in beef herds that will enable producers to limit its effect in their herds. The most important concept that producers need to understand is that anything that can affect early embryo divisions and growth will likely affect its synchrony with its maternal environment and decrease its ability to produce adequate signal in time for maternal recognition of pregnancy. Factors involved and discussed in this paper include genetic factors, nutritional factors, plant toxins, environmental stresses, the role of hormones, age and male fertility. Technical Abstract: Mechanisms involved in pregnancy establishment and maintenance in cattle are complex. Approximately 95% of matings, regardless of whether they are by artificial insemination or natural service, result in fertilization. However, rarely do 70% of these matings result in a pregnancy that is maintained through gestation. The majority of pregnancy losses occur from fertilization until day 27 of gestation during the period defined as early embryonic mortality. Adequate progesterone concentrations during the preceding estrous cycle and during early pregnancy, along with proper nutrition are important for an ideal maternal environment. Inadequate energy, excess protein (especially rumen degradable protein), and both thermal and handling stress are able to cause early embryonic mortality by decreasing progesterone, increasing uterine prostaglandin release, decreasing uterine pH, and increasing blood urea nitrogen and ammonia. Heat stress is the major limitation to embryo survival in Brazil, and mechanisms that affect the thermal tolerance of cattle there are the primary driver of improving reproductive performance. Understanding the role that managers can assume to control some of these variables should result in greater pregnancy establishment and maintenance as well as an economic return for their efforts. |
