Relative Effectiveness of Estrous Synchronization Methods in the Ewe

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1 South Dakota State University Open PRAIRIE: Open Public Research Access Institutional Reposiry and Information Exchange South Dakota Sheep Field Day Proceedings and Research Reports, 1985 Animal Science Reports 1985 Relative Effectiveness of Estrous Synchronization Methods in the Ewe K. F. Hoppe South Dakota State University A. L. Slyter Follow this and additional works at: Recommended Citation Hoppe, K. F. and Slyter, A. L., "Relative Effectiveness of Estrous Synchronization Methods in the Ewe" (1985). South Dakota Sheep Field Day Proceedings and Research Reports, Paper This Report is brought you for free and open access by the Animal Science Reports at Open PRAIRIE: Open Public Research Access Institutional Reposiry and Information Exchange. It has been accepted for inclusion in South Dakota Sheep Field Day Proceedings and Research Reports, 1985 by an authorized administrar of Open PRAIRIE: Open Public Research Access Institutional Reposiry and Information Exchange. For more information, please contact

2 RELAT IVE EFFECT IVENESS OF ESTROUS SYNCHRON IZAT ION METHODS IN THE EWE (PROGRESS REPORT ) K. F. HO PPE AND A. L. SLYTER Depar tment of An ima l and Range Sciences Ag ricultural Experiment Stat ion SHEEP Summary Two methods of synchronizin T estrus, sing le in jection and dual injections of prostagland in F2 a (PGF) were compared. Re lative effect iveness was determined by measuring number of ewes conceiving by day after last injection, number of ewe s conceiving by day after initial exposure fertile, dates of first mating and number of lamb s born per ewe lambing. No significant differences in parame ters measured due treatments were found. However, trends suggest synchronization did occur, especially ob servable in dates of first mating. Lack of statistical differences may be due unexpected synchrony in the control treatment which would not be consistent with previous reports from this station. (Key words : Estrus, Ewe, Prostag landin F2a, Synchronization) Introduction The value of synchronization is in reducing the breeding period. Prostagland in F2 a (PGF ) has been demonstrated effectively synchronize ewe s during the normal breeding season. Different me thods of synchronizing estrus with PGF have been proposed. The purpose of this trial was compare the relative effectiveness of a singular PGF injection vs. a dual injection of PGF 10 days apart a control for synchronizing estrus in the ewe during the normal breeding season. Experimental Procedure Purebred Hampshire (n=75) and purebred Columb ia (n=72) ewes were randomly allotted one of three groups : 1-10 mg PGF, 2-10 mg PGF or a control group, during the September-Ocber breed ing seas0n. The controls received no injection. The 1-10 mg PGF treatment invo lved a single 10 mg PGF IM injection given, 4 days after exposure, ewes which had not mated. The 2-10 mg PGF treatment involved two 10 mg PGF IM injections given 10 days apart with the last injection concurrent with the 1-10 mg PGF treatment. were not allowed with the 2-10 mg PGF treatment ewes unt il after the second injection. All ewes were exposed epid idymecmized teaser for two weeks prior the 35 day breed ing period. A flushing ration Prepared for Sheep Day, June 6, Lu talyse, courtesy of The Up john Company, Kalamazoo, MI

3 consisting of brome grass-alfalfa pasture supplemented with 0.34 kg (0.75 lb ) ground corn per head per day was fed during the prebreeding and breed ing periods. On day 1 teaser were replaced with semen tested purebred Hampshire or Columb ia, at the rate of 1 ram per 19 ewes, for controls and the 1-10 mg PGF group in single sire purebred groups. Each ram was exposed a random samp le of ewes from each treatment group and data were pooled across for analysis. A mark ing mixture cons isting of grease and wool brand ing paint was applied on the chest area of the ram daily. Breeding marks were taken at 24 hour intervals between hours. The sing le injection of 10 mg PGF was given on day 5 (0800 h) as was the second injection for the 2-10 mg PGF group. were removed on day 35 for the contro l and 1-10 mg PGF treatments and on day 39 for the 2-10 mg PGF group (Tab le 1). Results and Discussion Parame ters measured were days concep tion after last injection, days conception after initial exposure fertile, date of first mating and number of lamb s born per ewe lambing. Tab le 2 depicts number of ewes conce iving by day after last injection. No statistical dif ference was found for number of ewes conceiving by day after last injection for tre atment, breed or treatment x breed interact ion using analysis of variance procedures (Table 3). A bimodal distribution trend for ewes conce iving by day after last injection does seem appear for the 1-10 and 2-10 mg PGF treatments wh ich may be representing two estrous periods 17 days apart. This would suggest the ewes were synchronized but only part conce ived at the first estrus. Also of particular notation is the high percent of contro l ewes conceiving by day 6 which theorectically would not be expected. This may be due the use of teaser prior the breed ing period. Phys ical contact, sight and smell may have stimu lated ewes show estrus. Teaser were with ewe s for 14 days. Day 3 for controls would correspond day 17 after introduction of teaser. This was not evident in the treated groups. Number of ewes conceiving by day after exposure fertile were not statistically different among treatments (figure 1). The Columb ia breed conceived earlier than the Hamp shire (P<.05). The treatment x breed inter act ion was not significant ind icating breeds responded similarly across treatments. Treatment, breed or the treatment x breed interaction for date of firs t mating after exposure were not different (P>.05). A trend for synchronized mat ing appeared in the treated groups. Twenty-three and 24 ewes from the 1-10 mg PGF and 2-10 mg PGF groups, respectively, mated on the third day after injection compared none of the control ewes on a comparab le date. Number of lamb s born per ewe lamb ing did not differ (X 2 = treatments ) among 6 8

4 TABLE 1. SYNCHRONIZATION PROCEDURE. Treatment Day -14 Day -5 Day 1 Day 5 Day 35 Day Control No teaser ferti le remov ed mg PGF Single 2 teaser fertile Inj ect ion removed O'I \.0 PGF 2-10 mg PGF First Second teaser removed PGF PGF and exposed fertile 1 Lutalyse 2 Single ewes not previously marked.

5 TABLE 1. SYNCHRONIZATION PROCEDURE. Treatment Day -14 Day -5 Day 1 Day 5 Day 35 Day Control No teaser ferti le remov ed mg PGF Single 2 teaser fertile Inj ect ion removed O'I \.0 PGF 2-10 mg PGF First Second teaser removed PGF PGF and exposed fertile 1 Lutalyse 2 Single ewes not previously marked.

6 TABLE 2. NUMBER OF EWE S CON CEIVING BY DAY AFTER LA ST INJECTION. Days after lnj ect ion Treatment Cont rol 1-10 mg PGF 2-10 mg PGF

7 TABLE 3. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR INTERVALS TO CONCEPTION, DATE OF FIRST MATING AND NUMBER OF LAMB S BORN. Days after last Days after Julian date of Number of Lambs Inj ection Exposure first mating after born per ewe Conception fertile Exposure Lambing Conception Fertile L.S.Means ±S.E. L.S.Means± S.E. L.S.Means±S.E. L.S.Means Control 5.92 ± ± ± lomg PGF ± ± ± " I-" lomg PGF ± ± Hampshire ± ± ± Columbia ± o ± ±

8 TABLE 3. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR INTERVALS TO CONCEPTION, DATE OF FIRST MATING AND NUMBER OF LAMB S BORN. Days after last Days after Julian date of Number of Lambs Inj ection Exposure first mating after born per ewe Conception fertile Exposure Lambing Conception Fertile L.S.Means ±S.E. L.S.Means± S.E. L.S.Means±S.E. L.S.Means Control 5.92 ± ± ± lomg PGF ± ± ± " I-" lomg PGF ± ± Hampshire ± ± ± Columbia ± o ± ±

9 TRTcCQNTRQL 9 N E 5 w 4 E 3 s 2 \ o-l-j, ""--L-J.-i...1-_.._ l l i l l l l l l l ' l2345 DAY TRT=lXlOMG PGF i l 1 1 l , DA!RT=2X 1 0MG PGF N E 5 w 4 E 3 s 2 l _._._...._....._..._. ; l i i i l l i DAY Figure 1. Number of ewes conceiv ing by day after exposure fertile. 72

10 Controls unexpectedly mated and conce ived predominately during the first half of the firs t estrou s cycle after exposure fertile. This is not characteristic of past synchronization trials at this station. However, the two me thods of synchronizing estrus resulted in similar synchrony of estrus. 73