Introduction Reproductive strategies: How to use nature to optimize results Dominik Burger Natural breeding strategies of horses high fertility high efficiency since 55 million years European Practitioners Symposium on Equine Reproduction, 8-9 February 2018, Ghent Belgium typical social groups: harems, bachelor stallion and transitional bands Introduction Introduction vs. modern breeding strategies due to Purpose of use Culture Politics Economics Hygiene Safety Other Social interactions and reproductive efficiency University of Hanover - Sabine Meinecke-Tillmann - Harald Sieme Reproductive biology University of Nottingham Behavioral biology European Evolutionary State Studs biology Association, Spanish Riding School etc. Model «copy of nature» The role of the mares Conventional stable Stable with free-moving stallion (24h/7d) The mares - seem in many cases to «choose» the stallion - determine time of copulation - initiate precopulatory interactions in 88 % of cases (McDonnell et al., 2000) 1
Mate choice by the mare Teasing Preferences of mares depending on oestrus cycle for visual, vocal and odour traits - Larger and older males (Burger/ Meuwly et al., PLOS One accepted 2018) - Low-pitched voices (Lemasson et al., 2015) - Other. Burger et al., 2010 Sexual selection mechanisms? Oxytocin? Oxytocin pg/ml Oxytocin secretion in oestrous mares exposed to stallions 26 teasing tests = 13 mares x 2 cycles Madill et al. 2000 Nikolakopoulos et al. 2000 basal value teasing following teasing min Käser R., Bruckmaier R.M., Thomas S., Sieme H., Wedekind C., Burger D., Theriogenology 86, 2222-2229, 2016 Oxytocin secretion in oestrous mares exposed to stallions Oxytocin secretion in oestrous mares exposed to stallions Intra-individual variation among mares 30.0 25.0 Oxytocin pg/ml 20.0 15.0 10.0 Example Mare Maya: Datenreihen1 6489 with stallion 1 with stallion 2 5.0 0.0 1 3 5 7 9 1113 151719 212325 272931 333537 394143 454749 515355 575961 6365 Time (min) Käser R., Bruckmaier R.M., Thomas S., Sieme H., Wedekind C., Burger D., Theriogenology 86, 2222-2229, 2016 Käser R., Bruckmaier R.M., Thomas S., Sieme H., Wedekind C., Burger D., Theriogenology 86, 2222-2229, 2016 2
22 mares from 16th February 30th April 80 p = 0.028 mares exposed to stallions ovulated significantly earlier Days 60 40 with stallion: 23.6±12.6 d without stallion: 45.0±23.5 d after study start Permanent stallion contact and onset of cyclic activity in 22 mares Wespi, B., Sieme, H., Wedekind, C., Burger, D., Theriogenology 82, 2, 189-194, 2014 20 0 No stallion Treatment Stallion Wespi, B., Sieme, H., Wedekind, C., Burger, D., Theriogenology 82, 2, 189-194, 2014 22 mares from 16th February 30th April Mate choice by the stallion? Number of ovulations 3 2 1 0 p = 0.029 in consequence: exposure to stallions led to more ovulation cycles during observational period: with stallion: 2.80±0.42 ov. without stallion: 1.83±1.03 ov. Neue Studien Besamung von Privatstuten mit permanentem Hengstkontakt Präferenzen des Hengstes in Abhängigkeit von MHC, Parasitenbelastung etc. Pheromone in Speichel, Urin, Kot, Vaginal- und Klitorissekret? Fruchtbarkeit No stallion Stallion Treatment Wespi, B., Sieme, H., Wedekind, C., Burger, D., Theriogenology 82, 2, 189-194, 2014 Harem stallion in nature Bachelor stallion bands - continuous survey of mares reproductive status by olfaction - herd cohesion: keeping together of all horses in harem keeping away of other stallions - provider of protection - incest avoidance (transitional bands) - eventually assistant harem stallion tolerated - large grouping of 2-17 stallions of all ages - numerous play fights measure of strength and determination of social positions - hierarchy foals (Bourjade, 2007) - sneak breeding (eg. young fillies) 3
Breeding of free-running horses Sperm competition theory Up to 33% of offspring in harems by subordinate or sneaker bachelor stallions (Asa, 1999). Harems Bachelor stallion bands (Bachmann) in species where males have to compete for fertilisation of eggs (Parker 1970; Birkhead and Moller 1998) because sperm production is costly (Wedell et al. 2002) predicts ejaculate characteristics to be plastically adjusted to the social environmenet(parker and Pizzari 2010) insects fish rodents sperm number (Birkhead and Pizzari 2002) sperm velocity (Fitzpatrick et al. 2009) affects sperm production or allocation «strategic ejaculation»? «Strategic ejaculation» Mare s factors? Results Time of oestrus cycle of mare «Strategic ejaculation» * => stallions ejaculating in the presence of oestrous teaser mares show reduced oxidative degeneration of seminal cell membranes over a period of at least 48 hours (p< 0.001) Jeannerat E, Janett F, Sieme H, Wedekind C, Burger D (2017) Scientific Reports 7, 44339 4
«Strategic ejaculation» Phase I: Tolerance test 23 experienced breeding stallions 4 days, daily trials max. 15 minutes each 15/23 (65.2%) with good acceptance 8/23 (34.8%) with bad acceptance 3 dangerous situations Phase II: Comparison collection on ground vs. on dummy 2 x 6 experienced breeding stallions (7.83 ± 4.37 year-old) 5 semen collections (cross-over design) electronic balance Phase II: Comparison collection on ground vs. on dummy Total sperm count: Ø 24.7% less sperms/ejaculate (p<0.05) «Strategic ejaculation» Phase II: Comparison collection on ground vs. on dummy Weight on hindquarters (% of total body weight) 5
Bachelor vs. Harem status Results Mean sperm number Experiment: 6 + 6 adult breeding stallions with proven fertility stabling with/ without mare in a crossed design August December 2 x 9 weeks Mean sperm number (x 10 9 ) after exposure to a mare: p = 0.04 after exposure to stallions: Order of exposure Burger D., DolivoG., Wedekind C., d PLoS ONE 10(11), 2015 Burger D., DolivoG., Wedekind C., d PLoS ONE 10(11), 2015 Breeding of free-running horses - preceded by ø 2 mountings without erection - duration < 1 minute - quiet event + afterward relaxation phase - during 1 to max. 2 days: multiple breedings / mare (ø 6; Steinbjörnssonet al., 1999) with an interval of minutes up to 1-2 hours Artificial insemination Current insemination regimes: one insemination pre- or postovulatory ± after ovulation induction two inseminations after ovulation induction Squires, E.L. (2009) J Equine Vet Sci 29, 268-273 Multiple inseminations/ cycle -Vidament et al., 1997 -Vidament et al., 1999 -Barbacini et al., 1999 -Siemeet al., 2005 vs practice: objective 1x Semen availability Economic aspects EndometriUs? Effect of AI-frequency on pregnancy rates and pregnancy loss rates in Hanoverian mares (%) 70 60 50 40 30 NRR-33 PRC PLRC 20 10 Vidament et al., 1997 0 1x 2x 3x 4x AI-frequency (Sieme et al. 2005) 6
Take Home Message The understanding of social interactions and reproductive strategies of stallions and mares - opens up new ways with potential impact on welfare, ethical and economical aspects in breeding and keeping of horses fertility libido problems handling and management 7