2009: Theriogenology Experiences and Reflections The 2009 Bartlett Address 1 2 Theriogenology Experiences and Reflections 3 B.E. Seguin 4 Professor Emeritus, College of Veterinary Medicine, University of Minnesota, St 5 Paul, MN, USA 6 7 Dr. Bartlett’s Influence 8 To start this story I go back to my first year in veterinary school at the 9 University of Minnesota. I worked in the Anatomy Department, and one of my 10 duties was to make bone preparations for teaching and display purposes. One 11 day I was asked if I would like to take on some extra work in this area and if so I 12 should contact a Dr. Bartlett at American Breeders Service (ABS) in DeForest, 13 WI. I did not know Dr. Bartlett but I certainly knew of the ABS Company, and 14 was therefore very excited to find out what this might be about. 15 Now I’d like to go back several years before to my teenage years in my 16 hometown of Alma Center in west-central Wisconsin. I was a “city-kid” if that is 17 possible in a town of some 400 people. My dad introduced me to all kinds of 18 animals but he especially liked birds and we raised chickens, ducks, pheasants 19 and homing pigeons. I was more interested in dairy cattle. All six of the major 20 breeds were raised on farms in our area. But Guernseys were my favorite as 21 they were raised by my good friend Fred Moseley and on the Seguin family farm 22 near Eau Claire, WI. As artificial insemination (AI) increased in popularity, I 23 21 became intrigued with bull studs, semen technology and the work of AI 24 technicians. So I was well aware of the ABS Company. The local veterinarian 25 lived just a few houses away. I found his practice in general, but especially the 26 reproductive part, compelling. So my intention for going to veterinary school was 27 to work with cattle, and especially cattle reproduction in dairy practice or possibly 28 the AI industry. 29 So I was very excited to find out what Dr. Bartlett had in mind. (Wouldn’t a 30 four-year scholarship be wonderful!)? As you can guess, what he was looking for 31 was someone to provide pelvis preparations for use in their training programs for 32 AI technicians. I was able to provide the specimens so my first paycheck for 33 theriogenology work was thanks to Dr. Bartlett! But the real reward for me was 34 the chance to get to know the veterinary staff at ABS: Drs. David Bartlett, Les 35 Larson and Willis Parker. From that point on, the possibility of a career similar to 36 theirs was my motivation whenever needed to get through veterinary school. A 37 fact that is not well known is that Dr. Bartlett was the first head of the Ob/Gyn 38 Department in the College of Veterinary Medicine at the University of Minnesota. 39 In 1984 Dr. Bartlett gave the first of these addresses at this same meeting in 40 Denver, Colorado. I encourage you to read that paper as it is a classic reflection 41 of Dr. Bartlett’s professionalism, intellect and dedication to our profession and 42 specialty.1 So I am deeply honored to speak to you today as this is the 25th 43 anniversary of the first Bartlett address given of course by Dr. Bartlett himself. 44 Student at the University of Minnesota Veterinary College 45 22 As veterinary students at Minnesota in the 1960’s most of us had heard 46 the legend of Dr. Ray Zemjanis long before we were to have him as a teacher. 47 He was on sabbatical for our 3rd year when we started our theriogenology 48 courses. However we were not shortchanged, as a very capable group remained 49 to carry on: Dick Schultz, Mel Fahning, Louis Archibald, Charles Gibson, Dennis 50 Copeland, John Ellery and Bob Wescott. They were all superb teachers, strong 51 mentors and excellent theriogenologists. During that year we took cow palpation 52 lab, which included several early morning trips to the Bartusch slaughterhouse 53 about 3 miles from campus. On these trips cows to be slaughtered that morning 54 were palpated and findings recorded by each student. The reproductive tracts 55 were recovered and returned to the Therio lab for review (and grading) that noon. 56 This nearly instant feedback helped us master the art and science of cow 57 palpation and reproductive physiology. This slaughterhouse resource was the 58 backbone of the Minnesota program and where we really learned the techniques 59 described in the Zemjanis textbook Diagnostic and Therapeutic Techniques in 60 Animal Reproduction.2 Ray Zemjanis returned as we started our 4th year. Those 61 of you who knew him you can imagine the surprise we experienced that first day 62 in lecture. Even though his reputation had proceeded him and we knew we could 63 learn a great deal from this man, his hardcore, old school, no nonsense approach 64 was a shock to say the least. If we answered when doing cow palpation with “I 65 think I found ------“, he would respond, “Your clients won’t care about what you 66 THINK you found, they expect you to KNOW what you found.” Of course he 67 23 was right and we gained great respect for the teaching system he established 68 and the principles he professed. 69 Colorado State University 70 Toward spring of my 4th year, a notice was posted that the veterinary 71 college at Colorado State University (CSU) was looking to fill an internship 72 position in bovine reproduction. Anyone interested should contact Dr. Ed Carroll 73 at the “Bull Farm”. That address sounded perfect! I went to the library to see 74 what I could learn about Dr. Carroll and found his paper on BSE of 10,940 beef 75 bulls,3 which was the basis for the formation of the group that would become the 76 Society For Theriogenology. I applied and was fortunate to be offered the 77 position. The Bull Farm was an exciting place where I worked with Drs. Carroll, 78 Les Ball and Lloyd Faulkner. We did lots of bull work and more cow work (both 79 beef and dairy) than I had imagined. Also present at CSU were Dr. Bill Pickett 80 with his equine research program and Dr. Jim Wiltbank working on beef cow 81 reproductive management systems. Their detailed approach to controlled 82 experimental design in animal reproductive studies made a strong impression. I 83 had many “interesting” mornings with Dr. Pickett and his graduate students 84 collecting semen in their seasonality study in stallions and in a boar project. 85 These experiences plus a growing concern at that time about seminal vesiculitis 86 in bulls started me thinking that research in bovine reproduction and possibly 87 even graduate school might be something to consider. Dr. Carroll and I did a 88 small trial on seminal vesiculitis in yearling bulls in the hopes of creating the 89 24 basis for a possible graduate degree project. [Unfortunately Ed’s life was far too 90 short; he was a valuable resource to our profession.] The days at CSU flew by. 91 Michigan State University 92 Fortunately for me there was a bovine theriogenology residency/MS spot 93 at Michigan State University with Drs. Dave Morrow, Wayne Oxender and Fayne 94 Oberst. I got off to rocky start with Dr. Morrow when he wanted me to write an 95 application for an NIH postdoctoral fellowship. My first reaction was to question if 96 a veterinarian was even eligible, but indeed we are (or were). About the last 97 thing I thought I wanted to be doing was to be confined to a desk when there 98 were field trips, clinic cases and experiments to be done. But I did the 99 application and have been grateful to Dr. Morrow ever since as it was funded 100 about 2 years later. My Master’s thesis was on the cycle-altering effects of 101 endometrial irritation in cows,4 which started my career-long search for better 102 control of the timing of estrus and ovulation in cattle. Two review papers by Dr. 103 O.J. Ginther were available on the utero-ovarian relationship in cattle.5,6 I still 104 feel these should be must read literature for graduate students and/or residents 105 in theriogenology. At that time we were still talking about the uterine luteolysin 106 and the luteolytic factor, but this would soon change. 107 The Dairy Science Department at MSU had a very active Reproductive 108 Physiology group that included Drs. Harold Hafs, Alan Tucker, Ed Convey, Jack 109 Britt and Wayne Oxender plus a large number of graduate students. It was the 110 exciting place to be. I was accepted into a Ph.D. program with the Dairy Science 111 group with Wayne Oxender as my advisor. Graduate students were officed six 112 25 per room so there were many stimulating discussions. There were always lots of 113 trials being planned and conducted and many needed the assistance of a 114 veterinarian so my days were always busy. 115 If you know Wayne Oxender, you know that something interesting was 116 always going on when he was around. In those days, Select Sires and Michigan 117 Animal Breeders had a bull stud on the edge of campus. They allowed us to use 118 25 two-year-old Holstein bulls housed in tie stalls for our experiment. The 119 purpose was to study five anterior pituitary hormones possibly involved in the 120 process by which false mounting bulls increases the number of sperm per 121 ejaculate. Each bull was treated and then bled via the tail vein eight times in a 122 24-hour period. That barn was all muscular energy, testosterone and flying 123 hooves. Somehow we all survived and I was able to present the project at the 124 ASAS meeting in Lincoln, NE. 125 Prostaglandin! Today the activity of prostaglandin F2α (PGF2α) in cattle 126 is taken for granted but in 1972 prostaglandin was pretty much unheard of. One 127 day at the weekly graduate seminar Tom Louis reviewed some recent work in lab 128 animals that showed some negative effects on corpus luteum (CL) function by a 129 compound, which was thought to be what we had been calling the uterine 130 luteolysin. As I remember many of us present thought “This is a Dairy Science 131 Department, what in the world does this work have to do with cows?” Little did 132 we appreciate where this was going to take us. Shortly thereafter, Dr. Hafs went 133 to visit Dr. Jim Lauderdale at the Upjohn Company about the possibility of some 134 trials with a new compound that was PGF2α. Soon Tom Louis, John Stellflug, 135 26 and I were sent to the University’s dairy to select heifers and cows for the initial 136 trials with this product. Late one night we were in the research barn getting 137 everything ready for the start of the project when the manager of the dairy farm 138 walked through. It must have been obvious to him that we could hardly contain 139 our excitement. He asked what company was sponsoring the project. We were 140 only thinking about how the project would get us started on our graduate work 141 but he was looking for an investment opportunity! In the first trials cows were 142 treated by intrauterine infusion in the ipsilateral vs. contralateral horn to the CL 143 and the heifers by intravaginal deposit vs. IM injection in diestrus vs. metestrus. 144 There were no adverse reactions and to our amazement, the CLs that were 145 present at the time of treatment were soon disappearing. When the heifers went 146 out for heat detection on the third day after treatment they lined up in standing 147 heat like elephants in the circus. These two projects resulted in two of the first 148 publications on the action of PGF2α in cattle.7,8 Many other experiments with 149 PGF2a followed to further define dose effects, routes of administration, intervals 150 to estrus and ovulation, etc. Then it was time for fertility trials where we had very 151 good results.9 A review of potential uses of PGF2α in cattle was presented at the 152 first SFT conference by Wayne Oxender.10 153 There were some other PGF2α experiments and experiences with 154 unexpected events. Several surprises occurred at the Chatham Experiment 155 Station in the Upper Peninsula of Michigan where we used beef cattle for one of 156 the first PGF2α fertility trials. The first was that we would take a commercial 157 plane to Chatham, which sounded great, but it was a very bumpy ride in a small 158 27 commuter plane and it made 3 or 4 stops! A second surprise was the weather. 159 We left Lansing on a beautiful spring day but in the UP it was still winter with 160 more than a foot of snow still on the ground. Another surprise was the cattle. 161 Some of you will remember the Chianina beef breed that was imported from Italy 162 for crossbreeding to add some size to our native beef cows. It turned out their 163 other highly heritable traits were how high they could jump and how slow they 164 were to reach puberty. The heifers used were ½ and ¾ Chianina yearlings. 165 Although well grown and in good condition, many were not yet cycling and they 166 all could jump. It was a long day. You have probably seen the warning on the 167 Lutalyse® bottle that says exposure to this product may cause breathing 168 problems or an asthmatic attack in some people. I have never seen such a 169 problem with the commercial product but for these first trials PGF2α came to us 170 in powder form that we had to dissolve in PSS. I had usually done this in a large 171 well-ventilated room but that day I did it in a closed up car. As I mixed the two, 172 some of the PGF2α powder became airborne and I experienced a weird 173 respiratory episode. This did not last long but I was convinced of two things: 174 PGF2α is a potent substance and it is true that it’s half is very short. On our last 175 trip to Chatham an experiment station cowboy named Blacky took us Coho 176 fishing in a local river. When we could not get a bite by hook and line, he just 177 illegally used a dip net to catch a few under a state highway bridge. 178 There was also some mare reproductive research done in our group. Pat 179 Noden was another of the graduate students. Her Ph.D. thesis was on using 180 PGF2α for estrus control in mares.11 The day the first mare was treated I was at 181 28 the campus dairy barn. I received a phone call that there was an emergency at 182 the Bennett farm where the research horses were kept. By the time I was 183 contacted and got over there, all was quiet and no one was around. The only 184 thing that seemed unusual was a large wet spot in the treatment area! While we 185 had never seen any side effects from PGF2α in cattle, Pat had just seen the first 186 sweating reaction in a mare caused by PGF2α treatment. This reaction in mares 187 to PGF2α is well known now but was a shock that day. 188 Another surprise occurred when Dr. Hafs wanted to try PGF2α in bulls. He 189 had a research interest in sperm output and collection efficiency of AI bulls. He 190 wanted to see if an injection of PGF2α might mimic the affect seen with false 191 mounting. The initial trials were done in rabbits where the most obvious affect 192 was a marked increase in fecal expulsion. 193 One disappointing aspect of the early PGF2α work for me personally was 194 that we did not have approval to do research trials in lactating dairy cows. This 195 was my major interest area and where most of us thought the greatest use would 196 occur. 197 Gonadotropin Releasing Hormone: At the same time that the PGF2α 198 research was starting at MSU, Drs. Jack Britt and Ed Convey and several 199 graduate students were studying uses of gonadotropin-releasing hormone 200 (GnRH) in cattle reproduction. An early project by Britt et al. described the basic 201 effect of GnRH on LH release and showed great promise for the use of GnRH to 202 induce early postpartum ovulation and CL formation in cows.12 Another project 203 that became my Ph.D. thesis compared the luteotropic effects of hCG and GnRH 204 29 in normal cattle and in dairy cows treated for ovarian follicular cysts.13,14 An 205 interesting part of this work happened when several bovine practitioners were 206 asked to find cows with follicular cysts for this trial. Even though it was specified 207 that the cysts had to be follicular in type, 40% had enough progesterone to be 208 luteal cysts if not normal CLs. When in 10 to 14 days I went to examine and treat 209 the cows, most of that 40% no longer had the ovarian structure originally thought 210 to be a follicular cyst. A review of potential uses of GnRH in cattle was presented 211 at the first SFT conference.15 212 University of Minnesota Faculty 213 With completion of my graduate program at MSU, it was time to find a real 214 job. Back at the University of Minnesota there was a temporary position to be 215 filled while Ray Zemjanis went to Africa to teach for two years. The 216 Theriogenology group had changed greatly since my graduation. Now Ed 217 Mather, Howard Whitmore, Borje Gustafsson (newly hired from Sweden) and 218 Bob Wescott were the faculty, and residents included Shirley Johnston, John 219 Hurtgen and Rolf Larsen. Also working closely with the Theriogenology group 220 were the Reproductive Physiology group from the Department of Animal Science: 221 Ed Graham, Bo Crabo, Alan Hunter and Jon Wheaton. Members of both 222 departments participated in the Theriogenology Graduate Program, in which 12 223 to 15 veterinarians were enrolled. Later Ed Mather moved to Michigan State 224 University and Borje Gustafsson and Howard Whitmore went to the University of 225 Illinois. They were replaced by Ray Zemjanis returning from Africa, Norm 226 Williamson from the University of Melbourne and myself. After completing her 227 30 Ph.D., Shirley Johnston joined the faculty as Small Animal Theriogenologist. Dr. 228 Mel Fahning returned to the program after several years in private practice and 229 bovine ET business. These were rewarding times with an excellent teaching and 230 clinic program for veterinary students, and productive teaching and research with 231 veterinary residents and graduate students in Theriogenology. 232 With a series of graduate students we continued studying applications for 233 PGF2α and GnRH in cattle. Now we had two PGF2α products (Estrumate® and 234 Lutalyse®) to work with. Despite ads to the contrary we could find no significant 235 difference in the luteolytic potency between these two products in dairy cows.16 236 We did however make some interesting observations on factors affecting results 237 with either product when treating unobserved estrus in dairy cows. We did 238 several fertility trials in cooperating private beef herds. Cooperating farmers 239 would assure us that the entire herd was ready for the breeding season when we 240 planned for the first PGF2α injection. But a pretrial palpation would almost 241 always find at least a few pregnant cows! A good lesson for everyone involved 242 was that, at least in the first year of a PGF2α controlled breeding program for 243 beef herds, never treat cows prior to checking that some might still be pregnant. 244 We also looked at the efficacy of the PGF2α products to induce abortion in 245 feedlot heifers17 and causes of the variation in the timing of estrus after PGF2α 246 treatment. Then the fun began when it became possible to do PGF2α 247 application trials in lactating dairy cows; first in individual cows with unobserved 248 estrus18 and later in herd breeding programs.19,20 Today many dairy herds use 249 31 multi-product, multi-treatment programs for breeding that eliminate estrus 250 detection altogether. 251 One of the real highlights of my faculty career came in 1984-85 when I 252 was able to go on sabbatical leave at the Swedish Veterinary College. At that 253 time the Ob/Gyn Department included Drs. Stig Einarsson, Kjell Larsson, Hans 254 Kindahl as well as many excellent staff and graduate students. Their courses, 255 facilities, clinical service and research were first class. I could not speak 256 Swedish so I did very limited lecturing; rather I mostly helped the graduate 257 students with their research projects. My own research efforts that year were to 258 focus on measuring a PGF2α metabolite. This was thwarted by a small technical 259 detail that became a painful lesson. We changed to a new source of tubes for 260 blood collection without testing to see if the new tubes affected assay results. 261 After all samples had been collected, we learned that the new tubes somehow 262 interfered with the assay negating nearly a years’ work. My family and I will 263 never forget the hospitality and friendships we enjoyed that year. 264 We returned to Minnesota to some changes. Ray Zemjanis retired and 265 was replaced by Harry Momont. Norm Williamson moved to the veterinary 266 school in New Zealand and Jerry Olson joined us. Shirley Johnston moved into 267 administration. Harry Momont moved on to the veterinary school in Wisconsin. 268 Margaret Root Kustritz came on board to work in small animal theriogenology 269 and Mats Troedsson joined our group specializing in equine theriogenology. 270 One Last Trial 271 32 Over the years we had done many projects looking at various means to 272 maximize control of the timing of estrus and ovulation in cattle. These included 273 endometrial irritation, estradiol cypionate (ECP), PGF2α, GnRH, hCG, removal of 274 the ovary containing the preovulatory follicle,21 etc. 275 The last experiments I undertook involved two protocols that were tested 276 for potential to improve AI submission and pregnancy rates achieved by using 277 PGF2α (Lutalyse®, Pfizer Animal Health, New York, NY, USA) in dairy cows with 278 unobserved estrus judged to have a PGF-responsive CL by ovarian palpation. In 279 Expt 1, 151 cows were selected and treated with PGF2α. Cows in the 280 experimental group were treated with 1.5 cc (3 mg) of ECP IM at 30-34 hrs after 281 PGF2α while controls had no further treatment. Significantly more cows treated 282 with PGF2α plus ECP were seen in estrus and AI’d within 6 days of PGF2α than 283 were cows treated only with PGF2α (91% vs. 53%). Estrus behavior was more 284 tightly synchronized for cows treated with PGF2α plus ECP than for cows treated 285 only with PGF2α. Resulting conception rates were similar (55% vs. 58%). 286 Therefore pregnancy rate 6 days after PGF2α was higher for cows treated with 287 PGF2α plus ECP than for cows treated only with PGF2α (50% vs. 31%). In Expt 288 2, 197 cows were similarly selected and treated but all cows were AI’d at 72-76 289 hrs after PGF2α without regard for estrus behavior. There was no significant 290 difference in pregnancy rates between groups, 40% for 98 PGF2α plus ECP 291 cows versus 35% for 99 cows treated only with PGF2α. Results showed that a 3 292 mg dose of ECP 30-34 hrs after PGF2α treatment 1) can increase AI submission 293 and pregnancy rates in unobserved estrus dairy cows judged by palpation to 294 33 have a functional CL when AI’d based on detection of estrus, 2) can tighten the 295 estrus response pattern of responding cows, and 3) but did not improve 296 pregnancy rate results when cows were AI’d by appointment at 72-76 hrs after 297 PGF2α. 298 I did not publish this research although I believe it demonstrates significant 299 results for controlling estrus and ovulation with the combined use of PGF2α and 300 ECP. Unfortunately, the work is now nearly irrelevant because of public health 301 concerns regarding estradiol in the human food supply and the fact that ECP is 302 no longer marketed for use in dairy cattle. Nonetheless, these findings were a 303 rewarding culmination to 35 years of theriogenology research. I am pleased to 304 have had the opportunity to share them with you today. 305 Graduate Students 306 Working with graduate students has probably been the most rewarding 307 part of my career. I totally enjoyed the chance to help them search for goals, 308 answers and their future. In fact most of these ladies and gentlemen gave more 309 to me than I gave to them. Every one of them educated me in some way. I have 310 been able to visit many places and do many things. With Ahmed Tibary, I saw 311 great horsemanship and some of the world’s most beautiful Arabian horses in 312 Morocco. I saw beef production and the AI industry in Argentina with Miquel 313 Fortin. I reviewed theriogenology curricula and graduate programs at 3 314 veterinary colleges in Thailand with Preeyphan Udompresert. By the 315 recommendation of Juan Ramono, I visited dairy farms and gave CE lectures for 316 veterinary practitioners in Uruguay. With translation help from Stephano 317 34 Romagnoli, I lectured at the veterinary school in Pizza, Italy and to practitioners 318 in Sardinia. From Ting Q. Zhang, I learned about China. When I started, my 319 world was quite small but by these relationships it is now much more complete. I 320 cannot list you all here but please know that I am grateful for the experiences we 321 shared. Thank you! 322 Retirement and Beyond 323 Bovine theriogenology and academia have been very good to me and my 324 family (wife Trish, daughter Ann, son Tony, daughter-in-law Sarah Beth, and 325 granddaughter Avery). I cherish the memories. After 35 years it was time to 326 walk away – while I could still hit a golf ball. Since golf season is short in 327 Minnesota, I soon needed another activity. It has been surprising what a 328 veterinary education and a theriogenology career prepared me for. For 6 years 329 now I have done corneal excisions on organ donors as an eye procurement 330 technician for the Minnesota Lions Eye Bank. This too has been an interesting 331 and rewarding experience. 332 If you have not already done so, I encourage you to register as an organ 333 donor, discuss your wishes with your next of kin and give the gift of life or sight to 334 someone in need. 335 References 336 1. Bartlett DE: Theriogenology: from concept to actuality Proc Annu Conf 337 Soc Therio 1984; p. 221-234. 338 2. Zemjanis R: Diagnostic and therapeutic techniques in animal 339 reproduction, 2nd ed. Baltimore: The Williams & Wilkins Co; 1970. 340 35 3. Carroll EJ, Ball L, Scott JA: Breeding soundness in bulls—a summary of 341 10,940 examinations. J Am Vet Med Assoc 1963;142:1105-1111. 342 4. Seguin BE, Morrow DA, Louis TM: Luteolysis, luteostasis, and the effect 343 of prostaglandin F2α in cows after endometrial irritation. Am J Vet Res 344 1974; 35:57-61. 345 5. Ginther OJ: Utero-ovarian relationships in cattle: physiologic aspects. J 346 Am Vet Med Assoc 1968;153:1656-1664. 347 6. Ginther OJ: Utero-ovarian relationships in cattle: applied veterinary 348 aspects. J Am Vet Med Assoc 1968;153:1665-1671. 349 7. Louis TM, Hafs HD, Seguin BE: Progesterone, LH, estrus and ovulation 350 after prostaglandin F2α in heifers. Proc Soc Exp Biol Med 1973; 143:152-351 155. 352 8. Louis TM, Hafs HD, MorrowDA: Intrauterine administration of 353 prostaglandin F2α in Cows: progesterone, estrogen, LH, estrus and 354 ovulation. J Anim Sci 1974;38:347-353. 355 9. Lauderdale JW, Seguin BE, Stellflug JN, et al: Fertility of cattle following 356 PGF2α injection. J Anim Sci 1974;38:964-967. 357 10. Oxender WD: Prostaglandins in domestic animals. Proc Annu Conf Soc 358 for Therio 1975. 359 11. Noden PA, Oxender WD, Hafs HD: Estrus, ovulation, progesterone and 360 luteinizing hormone after prostaglandin F2α in mares. Proc Soc Expt Biol 361 Med 1974; p. 145. 362 36 12. Britt JH, Kittok R, Harrison DS: Ovulation, estrus and endocrine response 363 after GnRH in early postpartum cows. J Anim Sci 1974;39:915-919. 364 13 Seguin BE, Oxender WD, Brit JHt: Effect of human chorionic gonadotropin 365 and gonadotropin-releasing hormone on corpus luteum function and 366 estrous cycle duration in dairy heifers. Am J Vet Res 1977;38:1153-367 1156,1977. 368 14. Seguin BE, Convey EM, Oxender WD: Effect of gonadotropin-releasing 369 hormone and human chorionic gonadotropin on cows with ovarian 370 follicular cysts. Am J Vet Res 1976;37:153-157. 371 15. Seguin BE: Applications of gonadotropin releasing hormone (GnRH) in 372 domestic animals. Proc Annu Conf Soc for Therio 1975. 373 16. Seguin B, Momont H, Baumann L: Cloprostenol and dinoprost 374 tromethamine in experimental and field trials treating unobserved estrus in 375 dairy cows. Bovine Pract 1985;20:85-90. 376 17. Refsal KR, Seguin BE: Estradiol 17beta cyclopentylpropionate and 377 prostaglandin F2α for induction of abortion during the first trimester of 378 pregnancy in feedlot heifers. J Am Vet Med Assoc 1981;179:701-703. 379 18. Seguin BE, Gustafsson BK, Hurtgen JP, et al: Use of the prostaglandin 380 F2α analog cloprostenol (ICI 80,996) in dairy cattle with unobserved 381 estrus. Theriogenology 1978;10:55-64. 382 19. Seguin BE, Tate DJ, Otterby DE: Use of cloprostenol in a reproductive 383 management system for dairy cattle. J Am Vet Med Assoc 1985;183:533-384 537. 385 37 20. Seguin BE, Momont HW, King VL, et al: Breeding programs for dairy 386 herds using prostaglandin F2α products to save labor: field trial evaluation 387 of reproductive performance. Bovine Pract 1999;33:106-112. 388 21. Fortin MR, Seguin BE, Momont HW, et al: Interestrous intervals in cows 389 after unilateral ovariectomy at estrus to prevent corpus luteum 390 development. 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