THIS ARTICLE IS SPONSORED BY THE MINNESOTA DAIRY HEALTH CONFERENCE.

Transcription

1 THIS ARTICLE IS SPONSORED BY THE MINNESOTA DAIRY HEALTH CONFERENCE. ST. PAUL, MINNESOTA UNITED STATES OF MINNESOTA

2 COMPONENTS OF A PROGRESSIVE REPRODUCTIVE ~AGEMENTPROG~ JetTrey S. Stevenson, Ph.D. Dept. of Anima Sciences Kansas State University Manhattan, KS TEL: FAX: Introduction Postpartum Reproductive Events. Initiating eary reestabishment of norma estrous cyces af ter caving is essentia to aow adequate time for cows to be inseminated and maintain a 12- to 13-month caving interva. Normay, intervas from parturition to first ovuation average 3 to 4 weeks in miking cows. Because most first ovuations are not preceded byestrus, interva to first heat averages about 5 to 6 weeks. Invoution of the previousy gravid uterus is another critica event that must occur during the eary postpartum period. The rate of invoution is somewhat remarkabe because by 20 days after caving, tissue soughing and hemorrhaging have ceased, and the size of the uterus has been reduced by more than 80%. By 40 days, the uterus has competey invouted except for isoated pockets of eukocytes. A of these events (invoution, first estrus, and first ovuation) are deayed in cows with periparturient probems such as dystocia; twinning; uterine infections; ovarian cysts; injury; or metaboic diseases such as ketosis, dispaced abomasum, and mik fever. Furthermore, a measures of reproductive efficiency are reduced in cows with periparturient probems compared with norma cows. Infertiity or reproductive faiure is often difficut to resove because of its mutipe causes. However, many new toos are avaiabe to dairy producers to enabe them to prevent, propery treat, and improve the overa reproductive heath of the dairy herd. Caving Intervas. Numerous studies have concuded that 12- to 13-month caving intervas are optima for achieving maxima annua mik yied and economie vaue for dairy producers. Conceptions occurring before 60 days in mik resuted in shorter caving intervas and reduced cumuative mik yieds of current and foowing annuaized actations. Caving intervas onger than optimum (> 14 months) resuted in cows spending a greater proportion of their productive herd ife in ater and ess profitabe stages of the actation curve. Moreover, economic osses associated with more or ess than optima caving intervas go undetected, because they represent ost potentia income in ieu of actua "out-of-the-pocket" expenses. Repacement Heifers. Proper scheduing and introduction of repacement heifers into the miking string are of equa importance. Heifers shoud enter the miking herd no ater than 2 years of age to maximize their ifetime performance and reduce maintenance costs. Inseminating growthy and we-deveoped heifers at younger ages offers the advantage of 169

3 earier recovcty of their rearing costs. As ong as specia attention is paid to the nutrition and growth of heifers, and proven sires with known caving ease (ess than 9% DBH [difficut first births]) are used as breeding sires, research has shown that heifers can cave earier than 2 years of age. It is not difficut to find exceent sires with acceptabe eves of caving ease because 39 of the top 100 Hostein sires in the USDA Sire Summary (January, 1994) had DBH scores of 8 or ess (9.2% is breed average for Hostein sires). Controed Breeding Programs. In managing the breeding of both heifers and cows, use of prostagandin-f 2C (PG) or one of its anaogs offers many options to the dairy producer. Beyond the broad concept of estrous synchronization, these products aow manipuation of the estrous cyc1e according to the goas and convenience of the herd manager, inc1uding managing insemination schedues of actating cows to optimize caving intervas and age at first breeding in heifers. The purpose of this report is to present some reaistic appications of current techniques avaiabe to aow dairy producers and veterinary practitioners to manage a progressive reproductive program. Periparturient Heath Treatment for Retained Pacenta. Retention of the feta membranes or retained pacenta (RP) is one of the most common postpartum reproductive abnormaities in dairy catte. The incidence of RP averages about 10% in Hosteins and is affected by dystocia, mik fever, abortion, twinning, nutrition~ deficiencies, sex of caf, and induced caving. If the pacenta has not been reeased by 24 hr after caving, it is unikey to do so for 4 to 8 days. Athough RP might cause reproductive probems itsef, it is a predisposing factor for cinica metritis, which is strongy associated with decreased reproductive performance. A successfu treatment for dairy cows with RP is one of the PG's. When injections of Boviene (2 cc; 1 mg s.c.) were given to cows with RP 6 hr after caving, 67% had expeed their pacenta by 4 days after caving compared with ony 45% of the controi cows given saine. In simiar protocos using Lutayse nor Estrumate, neither has produced positive resuts comparabe to Boviene in this appication. Variousy administered treatments of GnRH have met with success when given to dairy cows, which earier had an RP, in attempt to prec1ude the negative effects of resuting uterine infections on the reproductive performance of those cows. In two studies, administration of GnRH during the second week postpartum (days 10 to 18) resuted in earier first ovuation, more estrous cyc1es before day 60 postpartum, reduced interva from caving to first service and conception, and tendency for fewer services per conception. In one study, 378 cows with RP were treated with GnRH or saine on day 15 postpartum. However, the GnRH treatment was successfu in improving overa reproductive performance of ony 39 cows when first breeding began before an average of 80 days postpartum in severa herds. Husbandry of Cows with Retained Pacenta. Good husbandry of cows with RP is critica. A recent study utiized Hostein heifers that were induced to cave with a 170

4 prostagandin injection (500 JJ,g Estrumate ) on day 274 of pregnancy. Sixteen heifers retained their pacentas and were assigned randomy to either aow their pacentas to be expeed without intervention (RP eft) or to attempt manua remova of the pacenta for 15 minutes on day 3 af ter caving (RP removed). These two treatment groups were compared with 17 heifers with out RP's (seven of whom were induced to cave but did not retain their pacenta). Attempted or successfu manua remova of the RP proonged the interva from caving to first appearance of a functiona corpus uteum (CL) by 20 days, increased interva to first service, increased the severity of uterine infection, and proonged the presence of pathogenic bacteria in the uterus compared with aowing the pacenta to expe spontaneousy. In those heifers in which the pacentas were untreated the characteristics described were not different from those in the controi group. Treatments with GnRH and/or Prostagandin. Since the mid 1970's, a number of studies have vaidated the benefit of utiizing GnRH as a prophyactic treatment for postpartum dairy cows. Injections of GnRH were first demonstrated to induce ovuation and norma cycing activity in dairy cows as earyasday 14 postpartum. Use of GnRH is effective in inducing ovuation in 80 to 90% of the dairy cows treated around days 10 to 14 postpartum. Those CL formed in response to GnRH are responsive to an injection of prostagandin in approximatey 5 to 6 days. Various studies have examined the reproductive performance of cows treated with both hormones in the eary postpartum period. The rationae for giving GnRH 10 to 18 days postpartum, foowed by a prostagandin in about 10 days, is bas ed on the observation that fertiity of dairy cows during the norma breeding period is directy proportiona to the number of estrous cyces occurring before breeding and the idea that GnRH shoud enhance the chances of earier cycing activity foowed by a prostagandin to reduce the ength of the first induced estrous cyce. One theory for the beneficia effects of these hormones and the increase in the number of estrous cyces in treated cows is the conditioning effect of severa heat periods on the uterine environment. Norma uterine contractions during estrus probaby aid in preparing the uterus for subsequent pregnancy. Injections of GnRH aso hasten the process of uterine invoution. Severa studies have shown that cows with periparturient disorders (reproductive or metaboic) are ikey to benefit from GnRH given 10 to 18 days postpartum. In an earier study, cows were cassified before day 18 postpartum as abnorma based on enargement of one or both uterine horns; poor uterine tone; an enarged; infamed or diated cervix; itte ovarian activity; or a significant puruent; mucopuruent; or boody vuvar discharge. When treated with 100 JJ,g GnRH at 12 to 18 days postpartum, abnorma cows responded with earier first estrus, and fewer days open and services per conception, where as simiary treated, norma cows had no improvement after GnRH treatment. In a further study (Tabe 1), marked improvement in the reproductive performance of cows occurred as evidenced by reduced days open and fewer services per conception in norma and abnorma cows when treated with either GnRH or PG, but not both, except for fewer services per conception in norma cows treated with GnRH and PG. A recent study in Forida found the PG injections given around day 26 postpartum improved reproductive 171

5 performance m: dairy cows, with previous dystocia and(or) RP at caving, better than injections of GnRH or the combination on GnRH on day 12 and PG on day 26 postpartum. Tabe 1. Fertiity Traits Associated with Postpartum Treatments with GnRH and/or Prostagandin F 2 (X (PG) days 10 to 14- Saine- GnRH- Saine- GnRH- Trait days 20 to 24- Saine Saine PG PG No. cows Days open Norma Abnorma a Services / conception Norma Abnorma Source: Adapted from Benmrad and Stevenson (1986) J. Dairy Sci. 69:800. 8Different (P <.05) from saine-saine group within heath status Various treatments of dairy cows with PG have demonstrated profertiity effects when cycing cows (i.e., most cows assumed to be cycing with a functiona CL at the time of treatment with PG) were treated during the eary postpartum period before the onset of the breeding period (i.e., before 40 to 60 days postpartum). When PG was given on day 26 and/ or day 40 af ter caving, interva to first estrus was deayed, but treatments reduced intervas to conception compared with pacebo-treated contros. Prebreeding Anestrus Attempts to induce cycing activity in dairy cows with proonged anestrus (smooth ovary cows with no ovuation [anovuation] and no observed estrus [anestrus]) have been few. The incidence of anovuation, which incudes those cases in which dairy cows have proonged or deayed intervas to first postpartum ovuation, ranges from 2 to 22% (average = 5%). Recent observations in one Caifornia dairy herd with a roing herd average exceeding 20,000 b, based on evauation of mik progesterone, indicated that about 15 to 20% of cows in their first actation and 5 to 10% of oder cows were not cycing before 60 days postpartum. Probems associated with negative energy baance and periparturient probems are probaby contributing to this greater incidence of anovuation. High mikproducing cows that os e more weight and body condition, and fai to maintain adequate dry matter intakes are sower to cyce than cows of simiar mik-producing abiity that consume more dry matter. A paucity of information exists assessing treatments for resoving the probem of anovuation in dairy cows. One French study found that reguar monitoring of anovuatory 172

6 cows with mik progesterone tests to determine when cows began to cyce after an injection of GnRH was successfu in reducing the interva to first breeding compared with no treatment or treatments with GnRH but with out progesterone monitoring. Some fied observations by veterinary practitioners and dairy producers have suggested that treating such anovuatory cows with progestin for severa days appeared to induce ovarian cyces. In some preiminary work, we found that impanting two anovuatory dairy cows (> 100 days postpartum) with Syncro-Mate-B impants (one impant per ear containing 6 mg norgestomet per impant) induced ovuation in both cows, one of which was preceded by estrus. In a more recent study utiizing GnRH in dairy cows in an aggressive herd monitoring and ovarian papation protoco, reproductive performance was improved compared with controis without GnRH treatments. Cows not responding to an initia treatment with GnRH were foowed up with a second treatment 14 days ater. If cows cyced spontaneousy eary postpartum or responded to the first or second injection of GnRH, they had higher pregnancy rates at 180 days in mik; overa reduced caving intervas; and, in some cases, required fewer services per conception. Avaiabe Products for Controing Estrus CurrentIy, three prostagandin products are abeed for use in cattie. However, ony Lutayse and Estrumate are abeed for use in actating dairy cows. Lutayse or PG, the first prostagandin product ceared by the FDA in the U.S., is identica to the substance naturay produced by the uterine endometrium.. It is capabe of inducing uteoysis or the demise of the corpus uteum (CL). The two remaining PG's are chemica anaogs of Lutayse produced by various substitutions on the termina carbons of the fatty acid-ike structure, which increase their pasma haf-ife but not their efficacy. Athough inferences have been made about the reative efficacy of these products bas ed on their onger pasma haf-ives, a three PG's are equay effective in their abiity to yse and destroy the CL in the nonpregnant cow or heifer. Furthermore, the abe caims of a three PG's provide evidence for their efficacy as abortifacients in heifers through 150 days of pregnancy. At the present time, ony one progestin product (Syncro-Mate-B ) is approved by the FDA for the use in ony dairy heifers. Heat Detection Vountary signs of heat such as mounting and standing in dairy cattie are infuenced by many factors. Those factors that are most important on dairy farms are: 1) number of sexuay active animas in a group, 2) freedom for sexuay active animas to interact, 3) freedom from interfering activities, 4) ambient temperature, and 5) footing conditions. Behaviora signs of heat require that at east two animas interact. Secondary signs such as butting, icking, and head-resting are infuenced ess by environmenta conditions than are the primary signs of heat, such as mounting and standing. Most experienced observers utiize these secondary signs to pick out cows that are most ikey to be in heat even when the immediate environmenta conditions imit mounting and standing activity. 173

7 A cow Wi not be detected to stand if no other anima is avaiabe to mount. Mounting activity is stimuated strongy byestrogen and inhibited by progesterone. Thus, mounting frequency is consideraby greater for cows in proestrus or estrus than for cows that are out of heat or in midcyce with a functiona CL. Once there are four or more sexuay active animas (proestrus or estrus ) in a group, mounting activity wi normay be sufficient for maxima efficiency of heat detection. Tabe 2 indicates reative mounting activity that one might expect to observe in various ocations and conditions on dairy farms. These empirica vaues are based on data from severa pubished and unpubished studies and on casua observations made on many farms. A vaue of 1.0 is assigned to mounting activity expected to occur on a reativey dry, grooved, concrete aey. A high index means more mounting activity. Activities or conditions that restrict interactions among cows infuence whether cows show heat. Cows that are eating or are crowded in hoding pens or aeys do ess mounting. Cows that are on sippery aeys, frozen ground, or any surface that makes footing tenuous show ess mounting activity. Cows in heat are more ikey to mount one another if the other cows are oose rather than tied. Perhaps this indicates that freedom to interact before mounting is important for maximum expression of mounting activity. Cows that have foot probems, regardess of whether the probem is structura, subcinica, or cinica, apparenty show ess mounting activity. Many of the foot probems that affect mounting activity can be aeviated by proper foot care (foot. baths, dry cows on dirt, etc.) and reguar hoof trimming. No firm experimenta evidence shows that high eves of mik yied infuence mounting or standing activity. Evidence exists energy baance during the eary postpartum period can infuence whether a cow is detected in heat at the beginning of the first postpartum cyce. Apparenty, cows experiencing a severe negative energy baance can produce enough estrogen to eicit an i surge without causing them to show heat. Once cyces have begun, energy baance does not seem to affect intensity or duration of heat, but might affect fertiity. Extremes in temperature affect intensity of heat. Mounting activity is ower on very "hot" or "cod" days than on days when the temperature is near the thermoneutra zone of the cow (30 to 50 o F). Heats may appear to be shorter when the temperatures are extreme, but it is uncear whether this is because of ess mounting activity or because of ess wiingness to stand. 174

8 Tabe 2. Reative Indexes of Mounting Activity Location of cows during heat detection Miking parior Feedbunk whie eating Hoding pen Dry concrete aey Dry concrete aey + movement Dry dirt ot Dry dirt ot + movement Mounting Index Source: J.H. Britt, persona communication Insemination Protocos after Prostagandin Various cacuations and research trias have shown that most cycing catte injected once with PG and then reinjected 10 to 14 days ater, regardess of their response to the first injection, shoud be at a stage of the cyce (days 5 to 17) at which uteoysis woud occur after the second of two injections. This theoretica projection generay has proved correct (athough not as wei in actating dairy cows uness injections are given 14 days apart) and served as a basis of one of four protocos promoted by the suppiers of the various PG's in their marketing information containing the abeied usages. Four schedued breeding programs are iustrated in Tabe 3. Program A consists of injecting a catte twice with PG 14 days apart. Inseminations foow ony the second of two injections. According to the abeied directions of each suppier, inseminations can be made according to observed heats or by appointment at 72, 80, or hr after the second injection. Program B is a variation of Program A, in which a animas detected in heat af ter the first injection are inseminated based ony on heat detection and ony the remaining noninseminated catte are reinjected 14 days ater and then inseminated according to the choices given above for Program A Program e consists ofbreeding for 6 days to: 1) detect estrus in those catte that are on days 17 through 21 of their cyces that woud come into heat spontaneousy but woud not respond to the injected PG, and 2) aow those catte recenty in heat to deveop a el (to at east day 6 of the cyce) that can respond to an injection of PG before ony undetected and noninseminated catte receive a first and ony injection of PG on the seventh day. Inseminations in this program shoud foiow heat detection or timed inseminations at 72, 80, or hr after PG. Program D is designed to be used af ter catte are papated for the presence of a functiona el. Success of this program requires great expertise by the veterinary practitioner because of the difficuty of assessing functionaity of the el based on papation per rectum or on the use of a 175

9 commercia miik progesterone test to vaidate high concentrations of progesterone in mik. Catte with a functiona CL are injected and then inseminated ike any of those after a second injection of PG in the previous programs. Tabe 3. Schedued Breeding Programs Utiizing Prostagandins (PG) Program A Program B Program C Program D Inject a femaes Inject a femaes Papation or with PG - tirst with PG - tirst positive mik P 4 injection injection test: Inject a femaes with PG 14 days ater-second injection Inseminate Detect heat and A. for 14 days Inject ony femaes not yet bred with PG 14 days after the first injection Inseminate Detect heat and breed for 6 days Inject ony femaes not yet bred with PG on day 7 Inseminate Must have a functiona CL Inject a eigibe femaes with PG Inseminate Factors Atering Success of Various Prostagandins Protocos Stage of the Estrous Cyce. Some earier reports had suggested a potentia seasona infuence on the timing of estrus after PG. However, it is cear in reports of the ast 20 years that the interva to heat after PG in both cows and heifers varies according to the stage of the cyce in which the injection occurs. Injections given on days 5 through 8 resuted in the shortest intervas to estrus (average = 49 hr), compared with days 8 to 11 (average = 70 hr) or days 12 to 15 (average = 62 hr). When heifers were inseminated according to signs of estrus, pregnancy rates were simiar regardess of the stage of cyce. However, when heifers were inseminated at 80 hr after the second of two PG injections, pregnancy rates were ower than when they were bred according to detected estrus. This reduction in pregnancy rate undoubtedy occurs be cause approximatey 60% of the heifers inseminated at 80 hr are bred too ate reative to the onset of estrus after the second injection of PG. When using one or two injections of PG (i.e., Programs A or B in Tabe 3), it is recommended to inseminate heifers according to signs of heat after the second injection (Program A) or after both injections (Tabe 4). Furthermore, we have found that heifers not observed in estrus by 80 hr after the second injection wi conceive to a fixed- 176

10 time insemination at 72 to 80 hr after the second injection about as wei as heifers inseminated according to detected heat. This fixed-time insemination is successfu because about 10 to 20% of the heifers that are in heat af ter the second injection are not detected in estrus. Fixed-Time Inseminations in Lactating Daiy Cows Simiar variation in the intervas to estrus have been observed in dairy cows given PG at various stages of the estrous cyc1e. We have observed that various fixed-time inseminations af ter the second of two injections of PG (11 days apart) in dairy cows resuted in ess than acceptabe pregnancy rates. When cows were inseminated either at 80 hr, with or without an injection of GnRH at 72 hr, or at hr (doube insemination) after the second of two injections, pregnancy rates ranged from 23 to 31%, compared with 51% in controi cows inseminated according to signs of heat but without prior injections of PG. Tabe 4. Fertiity of Daiy Heifers in 45 Michigan Herds with Different A.I. Schedues aer Prostagandins (PG) Pregnancy rate, % Schedue for insemination No. Mean Min. Max. Insemination at estrus Mer first PG Af ter second PG b 33.3 b Insemination at 80 hr after second PG No observations made for estrus c 6.7 c ,b Observations made but no detection c oc 73.3 c Source: Adapted from Fogwei et a. (1986) J. Dairy Sci. 69: ,b'CVaues acking a common superscript etter differ (P <.05). Range QB,b 79.9 b 73.3 b Severa factors account for the poor resuts achieved after fixed-timed inseminations of actating dairy cows. Injections of PG were ony 85% effective in regressing the functiona CL (defined as high [> 1 ng/ml serum concentrations of progesterone at the time of the injection and ow [< 1 ng/ml concentrations 24 to 48 hr ater) regardess of whether it was after the first (40 to 46 days postpartum) or at second (51 to 57 days postpartum) injection of PG. This efficacy of induced uteoysis was simiar to that in other studies with cows (91 to 92%) but ess than that observed with heifers (95 to 100%). Another imitation to success was that 15% of a cows had ow concentrations ofprogesterone (no CL) at the time of the second injection. One third of these cows was anestrus and 177

11 the remaining 'two-thirds were cycing but had ow progesterone at the time of the second injection and had high progesterone at the time of the first injection. This atter category suggested that cows were anovuatory, had ovuatory disturbances, or were at an unresponsive stage of the estrous cyce (days 17 to 21 or days O to 4) prior to the second injection because they faed to respond to the first injection 11 days earier. More recent work in Israe with actating dairy cows has shown some promising resuts with fixe d-time inseminations. When two injections of PG were given to primiparous cows at 11 versus 14 days apart, 84% of those receiving injections 14 days apart conceived within 30 days of their first service compared with 62% of those given injections 11 days apart. Unobserved Estrus In spite of the probems discussed above, there is pace for fixe d-time inseminations in dairy cows. Cows that fa to exhibit estrus (or whose heats are misse d) at various stages after caving wi have deayed intervas to first service and generay onger than average caving intervas. In addition, cows with unobserved heats after insemination, which are found open at pregnancy examination (40 to 50 days after the most recent service) generay have onger than acceptabe caving intervas. Both types of cows mentioned are candidates for PG. Cows with unobserved estrus, which might be difficut to detect in estrus because of subte or weak signs of heat, are best handed according to Program D in Tabe 3. Earier work suggested that about 90% of these cows are cycing but not detected in heat. In our study, every cow with a papabe. CL (based on assignment of cows by the various veterinary practitioners in 16 commercia dairy farms) was assigned on an atemate basis to serve as a controi (no treatment) or to receive PG. A controi cows were inseminated according to heat observations made by the dairy producers and a PG-treated cows were ikewise observed for heat and bred accordingy. However, those cows not detected in heat by 72 hr after the injection of PG were doube inseminated at 72 and 96 hr after PG. Cows treated with PG conceived 20 days sooner than contros even though pregnancy rates were simiar to those of controis and ony 53% of the treated cows were detected in heat (Tabe 5). Therefore, 47% of the cows inseminated after PG were not observed in heat and their pregnancy rate was 44% foowing a doube insemination at 72 and 96 hr. Without timed inseminations, we woud have ost 36 potentia pregnancies after treatment with PG. Another study reported neary equa success with ony one fixed-time insemination at 80 hr. The success of the resuts achieved in Tabe 5 (Program D) depended upon a high degree of accuracy in diagnosing a functiona CL (91 % accuracy in Tabe 5). The hazard of ovarian papation per rectum for identifying accuratey a functiona CL were reported recenty in a summary of four studies. The accuracy of diagnosis was verified by concentrations of serum progesterone at the time of papation. The accuracy of diagnosing a functiona CL papated per rectum was 82% (ranged from 79 to 85%) and the accuracy of diagnosing no functiona CL was 70% (ranged from 61 to 75%). In other words, 18% of the cows diagnosed to have a CL did not have high concentrations of progesterone and 30% of the cows with high concentrations of progesterone in their serum were diagnosed as not having functiona CL. Use of mik progesterone tests for determining ow (no CL) 178

12 or high (CL present) concentrations of progesterone generay are more accurate (> 95 % ), but aso more costy than papation. A generaized management scheme for handing open cows (those not yet inseminated or those open at pregnancy diagnosis ) is shown in Tabe 6. Tabe 5. Item No. cows Pregnancy rates, % Response of Dairy Cows with Unobserved Estrus to Prostagandin F 21 (PG) Inseminated at estrus, % Inseminated at h Observed in standing estrus, % Interva from treatment to conception, d Controi ± 6 Source: Adapted from Punkett et a. (1984) J. Dairy Sci. 67:380. 8Different (P <.05) from controi cows. PG Tabe 6. Decision Tree: Cows Not Vet Inseminated or Diagnosed Not Pregnant Use papation or mik progesterone to determine if there is a functiona CL: YES NO!! Inject PG... +wait 2 weeks YES A. breed Heat? NO!! A. at hr Heat after 96 hr? - reinseminate 179

13 U se of Prostagandin in Reproductive Management Schemes Weeky Insemination Groups. Athough estrous synchronization of many cows or heifers is not feasibe in most dairy situations except in arge herds or where seasona caving is practiced, use of PG for handing sma groups or breeding custers of cows and heifers that enter the breeding period based on caving or birth date, respectivey, is desirabe. This type of system works wei when couped with a weeky or biweeky herdheath visit by the veternary practitioner. A summary in Tabe 7 highights one method in which eigibe cows or heifers entered their respective breeding groups when found to have a functiona CL. Miking cows given PG were inseminated 11 days earier and conceived 18 days sooner than controis after assignment to the study. Furthermore, heifers treated in a simiar fashion with PG were inseminated 13 days sooner and conceived 18 days earier than their untreated herdmates. This type of reproductive management, coup ed with inseminations based on good heat detection, is another exampe of utiizing Program D (Tabe 3). Tabe 7. Use of Prostagandin F 211 (PG) in Reproductive Management of Cows and Heifers Item Controi cows PG cows Controi heifers PG heifers No. of femaes Assigned to studf Days to first service 81 ± 1 70 ± 1 b 21 ± 2 8 ± 1 b Days to conception 111±3 93 ± 3 b 38 ± 4 20 ± 3 b Source: Adapted from Seguin et a. (1983) JA VMA 183:533. adays postpartum for cows or months of age for heifers when entering the breeding group. bdifferent (P <.01) from controi within cow or heifer coumns. Monday Injections of Prostagandin. Based on the distribution of estrus after PG in the previous study (Tabe 7) about 88% of a first inseminations in cows coud be given on 4 days of the week. This transated subsequenty into 82% of a repeat inseminations of cows that retumed to estrus (not pregnant) occurring on 4 days of the 40-hr work week. From these responses, it was suggested that Monday use of PG coud aow most of the inseminations to occur on Wednesday through Saturday as iustrated in Figure 1. Simiar programs have been proposed in which eigibe cows (at east 40 to 50 days postpartum) were formed into sma breeding groups or custers (Tabe 8) and given PG (generay without knowedge of stage of the estrous cyce) on Monday mornings. Group cows into 3-week custers so that the freshest cow in the group meets the minimum 180

14 50 40 % O Figure 1. EZ CONTROL.PGF MON TUE WEO THU FRI SAT SUN Percentage of 205 actating dairy COWS observed in estrus after an injection of PG (PGF). Adapted from Seguin et a. (1983) JAVMA 183:533. acceptabe eective waiting period (EWP; 40 to 60 days). For exampe, if the EWP were SO d, then a custer woud consist of cows that are SO to 71 days in mik are injected on a Monday morning. Cows that fa to conceive shoud repeat to heat during the breeding week of a second custer that woud receive PG 3 weeks after (on Monday) the first custer of cows was injected. This cyce continues aowing the first services and repeat inseminations to occur during the same week, thus aowing most inseminations to occur during 1 week out of every 3 weeks. Tabe 8. Three-Week A.I.-Breeding Custers 3 weeks 3 weeks 3 weeks Estrus/AI I week I Estrus/AI I week I Estrus/AI I week I 1st custer Synchronization treatment I 1st A Repeat I A I Repeat I A I 2nd custer Synchronization treatment Ist A Repeat I A I 3rd custer! etc. Syncbronization treatment I 1st A! etc. Atemativey, cows are injected with PG on Monday morning and observed for heat during that week (Tabe 9). Cows not showing estrus are re-injected on the foowing Monday. This procedure is repeated on a tbird Monday if needed. Any cow not detected in heat after a tbird Monday injection of PG shoud then be presented for a reproductive examination by the herd veterinary practitioner. A recent study compared the weeky administration of PG to open cows to a system in which a open cows with a CL identified weeky by ovarian papation were administered PG. Cows receiving weeky doses of PG had 181

15 a 30% highe:r; pregnancy rate per unit of time. We recenty competed a simiar study in which cows were given PG based on a high mik progesterone test and compared that system to using no PG's but ony inseminating based on natura heats. The resuts are shown in Tabe 10. Use of PG improved neary a measures of reproductive performance. Tabe 9. Monday Morning Program for Cows Not Vet Inseminated or Diagnosed Not Pregnant PGF 2 o: :1-1 ~Ii---±I ~I~±I---:!I::---I NO HEAT?... Re-inject next Monday MTWHFSS Heat./ and A. I I I I I I I NO HEAT?... M T W H F S S Heat./ and A. etc. Re-inject Tabe 10. Reproductive Performance' of Dairy Cows Given Weedy Injections of Prostagandin F 2 o: (PG) Versus Using No PG (Contro) in aschedued Breeding Program Treatmenta Trait Controi Mik P4 + PG No. of cows Days to first service First-service pregnancy rate, % Percentage bred once in first daysb Caving interva Pregnant by 120 days, % Overa pregnancy rate, % Souree: Adapted from Stevenson et a. (1994) J. Dairy Sei. n:xxx. SE P vaue Controi eows were inseminated when estrus was deteeted by visua observation without the use of PG. Cows in the mik progesterone (P 4) + PG group were inseminated when estrus was deteeted by visua observation after an injeetion of PG foowing a high mik P 4 test. Cows in the atter group were tested for high or ow mik P 4 status and given injeetions of PG aeeordingy, for up to 3 weeks

16 bdays from beginning of breeding period (42 days postpartum) for contros and days from first estimate of mik P 4 in the mik P" + PG group. We attempted to examine the cost effectiveness of our two treatments (mik progesterone + PG vs controi) reative to the cost of each pregnancy achieved. Cost comparisons for our two treatments are summarized in Tabe 11, in addition to those of two other PG systems. Costs were estimated to approach reaistic vaues for mik P 4 tests, PG, and individua papations of cows. An additiona cost was added to our controi group because of its onger caving interva. Studies assessing the cost of days open beyond 365 days (12-month caving interva) range from $.25 to $4.68 per day open beyond 85 d, but may be more accuratey estimated by determining the optima days open and days to first service as a function of actation number based on cumuative mik and number of caves. We conservativey used the estimate of $1 per day open for controis beyond that which was achieved in the mik P 4 + PG group, for a tota of $23.30 per pregnancy in the contros. The cost per pregnancy in contros was $30.32 compared with a ower cost of $20.59 for the treated cows. To make the cost per pregnancy equa in our two treatment groups, the cost of 1 day open beyond 85 days woud have to equa ony $.35. In comparson to simiar estimates of cost in the previous study, weeky injections of PG cost $17.69 per pregnancy and that for papation + PG was $ Tabe 11. Cost Comparison for Breeding Programs Invoving Ony Visua Detecion of Estrus (Controi), Mk Progesterone (p.) + Prostagandn F 2a (PG), Weeky Bind Injecions of PG, and Papation + PG Treatmenr MikP4 Weeky Papation Item Controi + PG PG + PG No. of cows assigned No. of pregnancies Cost of mik P" ($3 each) O 864 O O Cost of PG ($3 each) O No. of injectionsjpregnancy O Cost of papations ($2 each) Cost of onger days open ($1 jday) b 1235 O O O ~ ota costs, $ Costjpregnancy, $ Source: Stevenson et a. (1994) J. Dairy Sci. 77:xxx. -Controi cows were inseminated when estrus was detected by visua observation without the use of PG. Cows in the mik progesterone (P,,) + PG group were inseminated when estrus was detected by visua observation after an injection of PG foowing a high mik P" test. Cows in the atter group were tested for high or ow mik P" status and given injections of PG accordingy, for up to 3 weeks. Information for the ast two treatments was adapted from a recent report (12) in which weeky injections of PG were given bindy 183

17 without knowedge' of utea or P 4 status (weeky PG) or when injections of PG were given to cows with a papabe corpus uteum (papation + PG). In both of the atter cases, treatments continued unti inseminations occurred or the cow was cued from the herd. bncuded was an assessment of $23.30 per controi cow ($1 per day open) that did not conceive unti 23.3 days ater than the mik P 4 + PG group. Median days open were 97 and 110 days for the atter two groups in another study, which were simiar to that in our mik P 4 + PG group (average = 101 days). Uses of GnRH to Improve Fertiity at Insemination Repeat Breeders. Administration of GnRH or one of its agonists to repeat breeders (cows that generay faied to conceive af ter at east two previous services) at the time of insemination has improved fertiity in amost a studies. We recenty pubished a six-herd study in which we tested a singe versus a doube insemination with or without the GnRH treatment, hypothesizing that the repeat breeder is ovuating ater after estrus than more fertie cows. A singe injection of GnRH given at the time of a singe insemination (according to the AM-PM rue) consistenty produced the highest pregnancy rates in a six herds (Tabe 12). Tabe 12. Pregnancy Rates in Repeat Breeders after GnRH Administration and Singe or Doube Insemination Singe ~emination No No Trait Injection GnRH injection No. of cows Pregnancy rate, % b 33 8 Source: Adapted from Stevenson et a. (1990) J. Dairy ScL 73: ,bpercentages without common superscript etters differ (P <.05). Doube Insemination GnRH ,b 184

18 Concusions These are somewhat exciting times for dairy producers and practitioners because of the new arsena of hormones avaiabe for controing estrous cyces and improving fertiity. Using Boviene seems to assist cows in reeasing a retained pacenta. Most studies have demonstrated that using GnRH as a foiow-up treatment (day 10 to 18 postpartum) for dairy cows with periparturient probems such as retained pacenta improves their subsequent reproductive performance. Recent rep orts demonstrate that injections of PGF 2G around day 28 postpartum are especiay effective in improving reproductive performance in dairy cows with previous dystocia and(or) retained feta membranes. Prophyactic treatment of eary postpartum cows with GnRH (days 10 to 18) or prostagandin F 2G (days 20 to 40) improved their reproductive performance in most studies as wei. Injections of GnRH at the time of insemination during ate estrus in repeat-service cows effectivey improves pregnancy rates. As with a new technoogies and hormona therapies, it is critica that attention be paid to consistent heat detection and good A. technique. Use of hormones wi not repace, ony suppement, good management procedures and common sense. Heifers. Programs A and B (Tabe 3) seem to be best suited for breeding repacement heifers (Tabe 3). Program B wi require ess PG per pregnancy than Program A, but it necessitates two periods of heat detection for each breeding group or custer formed. Many recommend injecting heifers to be inseminated and then observe for estrus and bre ed for at east 5 days af ter the first injection, then reinject the remaining noninseminated heifers 14 days after the first injection ofpg and inseminate according to heat detection for 5 more days. We have found that any heifer not observed in heat by 72 hr after the second of two injections shoud be timed inseminated at 72 hr, not 80 hr, which works wei for cows. The reason for the earier fixed-timed insemination at 72 hr is because heifers come into estrus about 10 to 12 hr earier than cows. Inseminating heifers at 72 hr after the second injection in the absence of detected heat wi produce pregnancy rates neary equa to those of heifers bred according to heat observations. Program D is a viabe aternative, if the veterinary practitioner visits the herd on a weeky or biweeky basis aid can work cosey with the dairy producer in managing the breeding groups in conjunction with routine ovarian papation as demonstrated in Tabe 3. Use of Syncro-Mate-B has merits for inseminating groups of heifers based on heat detection or fixed-time inseminations. Pregnancy rates seem to be simiar when heifers are inseminated based on detection of estrus or a fixe d-time insemination is used at 48 to 54 hr after remova of the 5MB impant. A heifers shoud be ins.eminated with semen from caving-ease sires and cave by 24 months of age. Cows. Two approaches for inseminating cows are appropriate. Injecting cows once with PG is effective for inducing estrus, if cows are between days 5 and 17 of their estrous cyce. About 60% of cows shoud respond to PG by coming into heat at any given time, if estrous cyces are neary randomy distributed across the herd. REMEMBER that these resuts are bas ed on identifying ALL cows in heat and doing so with neary 100% ACCURACY. Inseminations shoud be based so ey on heat detection in the case where ony one injection 185

19 of PG is given without evauating the CL status by papation or performing a mik progesterone test. This approach, which fits the weeky (Monday morning) breeding group or custer concept, is idea for handing cows bindy without knowedge of ovarian status or recent heat periods. 'A second approach for cows that fai to be inseminated by 80 to 100 days postpartum (whatever toerabe imit is set by management), as wei as those cows found open at pregnancy diagnosis, Program D is a recommended method of treatment (Tabe 3). Cows with a positive mik progesterone test or diagnosed to have a functiona CL by papation shoud be given PG and then watched for estrus. Those not caught in heat by 72 hr shoud be inseminated at 72 hr and re-inseminated at 96 hr after PG. The objective is to get these probem cows inseminated and possiby pregnant before giving up and designating them as reproductive cus. One must remember that cows with unobserved heats might have subte, weak, short periods of estrus and might benefit from a fixed-time insemination(s). H two injections of PG are used to synchronize estrus, an interva of 14 days is recommended. Regardess of the program (Tabe 3) seected, the best resuts occur foiowing good heat detection. Timed inseminations have a roe, but we must continue to concentrate on achieving better heat detection. 186