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NC1006: Methods to Increase Reproductive Efficiency in Cattle (Rev. NC-113)

Statement of Issues and Justification

Reproductive efficiency of cattle operations is suboptimal primarily due to: 1) failure of estrous cycles to resume after parturition, 2) poor fertility, and 3) poor detection of estrus in operations that use artificial insemination (AI). In attempts to improve reproductive efficiency, systems have been developed for programmed breeding. The recent research by the NC-1006 project has been instrumental in designing, testing, and optimizing systems that can be used for programmed artificial insemination (AI) in dairy and beef cattle herds. Many aspects of these reproductive management systems need to be optimized with basic research addressing mechanisms that reduce fertility in cattle and applied research to maximize economic benefits to livestock producers using available resources (i.e., FDA-approved hormones, labor, and facilities). Two major issues remain a focus for NC-1006 investigators and these will be addressed in studies during the next 5 years of research. 1) Recent research has demonstrated that anovulation is a surprisingly large problem in lactating dairy cows. For example, in the last joint project on lactating dairy cows by the NC-1006 committee, we found that 26.7% of lactating dairy cows were anovulatory following the voluntary waiting period. Recent studies by NC-1006 researchers that were discussed at our most recent technical committee meeting have continued to confirm a similarly high percentage of anovulatory cows based on multiple blood samples and multiple ultrasound evaluations of the ovaries. Thus, it seems clear that anovulation is becoming a more significant problem in lactating dairy cows. Modifying the Ovsynch protocol to synchronize the time of ovulation in lactating cows may substantially further reduce labor inputs for reproductive management; however, it may be possible to improve fertility with this treatment (one of the purposes of the current proposal). 2) In many beef cattle operations as many as 40 to 60% of cattle are anestrus at the beginning of the breeding season. None of the conventional programs prior to 1992 were designed to induce normal estrous cycles in anestrous cows. Adding a progesterone insert at the time of the GnRH injection improves fertility, especially in cows not cycling at the onset of the breeding season (contribution of the current NC-1006 project). Further refinement and success of these treatments should increase the convenience and appeal of applying AI to suckled beef cows. The current proposal, will test new treatments that are designed to synchronize ovulation in cycling cows and induce a fertile ovulation in anestrous cows and to determine the effects of a progesterone insert on embryonic survival.

JUSTIFICATION:

The Food Animal Integrated Research Symposium (FAIR 95) identified the need to "increase efficiencies of producing food from animals as a primary objective for future animal research." One of the key research areas with this objective was to "improve scientific understanding of reproductive mechanisms." Since FAIR 95, FAIR 2002 was convened as the second national conclave to establish consensus on animal agriculture research and education priorities for the 21st century. Six goals were established for FAIR 2002, each with its own set of objectives. The first of those goals was to "strengthen global competitiveness" and develop systems to keep U.S. animal agriculture competitive for the 21st century. Objective 1 of that goal is to "enhance production efficiency and economic strategies at the farm and ranch level." To achieve partly this objective, the report indicates that "research on different farming systems is needed to achieve efficiencies in reproduction." The NC-1006 committee is a long-standing group that has contributed greatly to the increase in reproductive efficiency of cattle since its inception in the early 1970's. Its long-term goal has been and continues to be consistent with the recent consensus goals set forth by FAIR 2002.

Our project encompasses the breadbasket states of the north-central region of the U.S. Included from that region in the current NC-1006 project are representatives from the Agricultural Experiment Stations of Iowa, Indiana, Illinois, Kansas, Michigan, Missouri, Minnesota, Ohio, and Wisconsin. Table 1 illustrates statistical information regarding the significance of the dairy and beef cattle industries in those nine states. It is clear that the numbers of dairy and beef cattle and their products, milk and meat, produced in the north-central region contribute a significant proportion (26-48%) of total production of the U.S. dairy and beef industries. Commodity receipts from sales of cattle and calves plus dairy products in the north-central region are significant, amounting to nearly $16 billion. Reproductive inefficiency is one of the most costly and production-limiting problems facing both the dairy and cow-calf industries. For example, in the six mid-western states that comprise the Heart of America Dairy Herd Improvement Association, 17.4% of the dairy cows in 1999 were culled because of reproductive failure. It was only exceeded by death (18.2%) as the leading cause of culling (1999 Heart of America Annual DHIA Summary). Similar statistics are reported by other DHIA organizations in the U.S.

Cull beef cow sales makeup 15-20% of cow-calf herd total income (NAHMS, 1997). Over 27% of beef cows are culled because of reproductive failure or reproductive problems. Based on numbers of operations, that percentage is 34% of all cull cows. Further, these percentages increase with herd size: <50 cows (16%), 50-99 cows (30%), 100-299 cows (51%), and ƒ.ƒr300 cows (69%). Only the western region (46%) has greater culling for reproductive failure than the north-central region (37%). The NAHMS survey concluded that "by optimizing reproductive performance, producers can decrease forced culls" (i.e., cows sold for involuntary reasons).

Losses that occur because of reproductive failure are partly due to mismanagement of resources and the lack of adoption of appropriate technologies to sustain greater reproductive efficiencies. In the 1997 NAHMS survey of beef cattle producers, questions were posed regarding use of various reproductive technologies on ranches. Of the 1,190 producers surveyed, AI was used by only 13.3% of the operations; pregnancy palpation by only 34.5%; and estrus synchronization by 11.9% of operations. Of interest to our NC-1006 committee!&s long-term objectives were the reasons why estrus synchronization was not employed on those cow-calf operations surveyed. Their reasons were: "it doesn't work"(2%), "time and labor issues"( (36%), "lack appropriate facilities" (8%), "cost"(13%), "too complicated" (20%), and "other" reasons (21%). It was likewise interesting that those similar reasons were given, almost to the percentage point, for why those operations had not adopted the use of AI.

During the last 10 years, the NC-1006 project has contributed greatly to the development of several breeding programs to maximize pregnancy rates (Objective 1 of the current 1997-2002 project). These successes directly address the objections or reasons given by cow-calf producers for not adopting reproductive technologies. Information accrued by our group led to the development of the Ovsynch protocol (Pursley et al., 1995; 1997a,b; 1998) and its variations (i.e., the Cosynch protocol, progestins + the Ovsynch protocol) used in beef cattle (Thompson et al., 1999; Stevenson et al., 2000). These protocols generally increased pregnancy rates beyond controls because in both dairy and beef cattle, they induce fertile estrus and ovulation in postpartum cows that have not resumed estrous cycles by the end of the volunteer waiting period (dairy cows) or at the onset of the breeding season (beef cows).

During the past 5 years, our group conducted two cooperative experiments. The first experiment involved testing the efficacy of adding progesterone (via a progesterone-releasing intravaginal insert; CIDR-B; InterAg, Hamilton, NZ) to the Ovsynch protocol in lactating dairy cows. This experiment was replicated at seven (IL, KS, IN, OH, MI, MO, and WI) of the nine experiment stations involved in NC-1006 (Pursley et al., 2001). Addition of the CIDR to the Ovsynch protocol increased pregnancy rates in cows that had not resumed estrous cycles before the onset of the protocol from 34.7% (n = 95) with the Ovsynch protocol alone to 55.2% (n = 87) with the protocol plus addition of the CIDR. Overall, pregnancy rates increased from 40.9% (n = 320) to 50.8% (n = 313), respectively. In addition, we have reported that pregnancy rates after the Ovsynch protocol are improved further when the protocol is applied to cows in their early luteal phase (Vasconcelos et al., 1999) or when estrous cycles of cows are presynchronized with one (Cartmill et al., 2001) or two (El-Zarkouny et al., 2001) injections of PGF2ƒp administered 14 days apart, with the second or only injection given 12 days before the onset of the Ovsynch protocol. In a second experiment a similar protocol in suckled beef cows was tested where the Cosynch protocol was compared to the Cosynch protocol + supplemental progesterone provided by the CIDR (Lamb et al., 2001). This experiment was replicated at four (IL, KS, MN, and MO) of the seven stations. We found that pregnancy rates were increased from 48% (n = 188) with Cosynch protocol alone to 58% (n = 177) with the same protocol plus the CIDR. Both of these protocols were carried out without any estrus detection and all cows were inseminated at one fixed time.

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