It is with immense sadness that the International Committee of the International Symposium on Equine Reproduction learnt of the death of Professor W.R. (Twink) Allen on 6th June 2021, after a short illness. We send our deepest condolences to his partner Sandra Wilsher, his wife Diana, his three children, grandchildren and other family members.

Twink was internationally renowned for his numerous and excellent pioneering contributions to equine reproduction, although he also made significant advances to the understanding of reproduction in old and new world camelids, African wildlife (particularly the elephant) and even hedgehogs! The list of Twink’s qualifications and honours speaks for itself but among Twink’s highest honours were his appointment as a Commander of the British Empire (CBE), a Higher Doctorate (DSc h.c. multi) from Cambridge University, and Fellowship in the Royal College of Veterinary Surgeons (FRCVS). He was also awarded many other degrees and honours: BVSc (Syd), PhD (Cantab), ScD (Cantab), DESM, Dip ECAR, FRAgSE and FSB. Twink also took great pleasure in his role as an Emeritus Professor at Robinson College, University of Cambridge.

Working with Twink was intellectually stimulating, and his enthusiasm for science shone through. His work ethic was immense and he never shied away from undertaking difficult projects, followed by the timely publication of the data in beautifully written, scientific papers. Twink was not only active in fundamental research and the training of PhD students, but he was also a driving force in the development and translation of many advances to practical equine reproduction procedures. Beginning his career in Cambridge and Newmarket in the late 1960s, Twink was the right person, in the right place, at the right time to make major scientific advances in equine reproductive biology, many of them “firsts” and to apply those discoveries and new technologies to improve the fertility of the horse. In all, Twink was an author of over 300 scientific papers and numerous book chapters, beginning remarkably in 1969 with a single author paper in the pre-eminent scientific journal “Nature”; a unique achievement. He was also a life-long member of the Society for the Study for Reproduction and Fertility. Twink remained active in research to the end, flushing mares to recover early embryos only weeks before his untimely death.

Twink loved horses and was fascinated by all aspects of equine reproduction, but his particular area of expertise was early pregnancy in the mare - whether it be searching for the maternal recognition of pregnancy signal, the origin of the equine capsule, molecular mechanisms underlying implantation and the endometrial cup reaction or the causes of pregnancy loss. Regardless of the problem, he was continually looking for ways to improve the fertility of the horse and particularly the Thoroughbred. Nevertheless, he was equally passionate about research and education and he formed long-standing, fruitful collaborations with Prof Doug Antczak at Cornell University, USA, Prof Bob Moor FRS and Dr Francesca Stewart at the Babraham Institute, Dr Peter Rossdale at Rossdale and Partners, and Prof Marian Tischner at Krakow University, Poland; all became lifelong friends. These collaborations led to multiple honours, including his election to the Polish Academy of Sciences, the award of Honorary Doctorates from the Universities of Krakow, Gent and Helsinki and the prestigious Marshall Medal from the Society for Reproduction and Fertility and election to the Hall of Fame for Equine Research at the Gluck Equine Research Center (Lexington, Kentucky). In 2018, he was awarded a Lifetime Achievement Award from the International Symposia of Equine Reproduction.

Born in Auckland, New Zealand, Twink graduated in veterinary science from Sydney University (1965). Twink then entered general practice New Zealand, where he suffered a devastating car crash, spending almost 18 months in hospital and emerging with one leg substantially shorter than the other, which curtailed his career in clinical practice. Serendipity led to him embarking on a PhD Research Fellowship with Professor Roger Short FRS at the Department of Veterinary Medicine at Cambridge University (1966-1970), producing a thesis entitled “Pregnant Mare Serum Gonadotrophin”. He was then employed as a post-doctoral Fellow at the nearby Animal Research Station in Cambridge (1970-1972), which was a world renowned large animal reproduction research institute, supervised first by Mr L.E.A. (Tim) Rowson FRS and then Prof Thadeus R.R. Mann FRS. In a far sighted move to improve the efficiency of Thoroughbred breeding, Mr Peter Burrell CBE, then Director of the National Stud in Newmarket and Colonel Nat Frieze, Chairman of the Thoroughbred Breeders’ Association established the Equine Fertility Unit (EFU) in 1972 and appointed Twink as its Director. The EFU was initially based in a portacabin at the Animal Research Station, but moved to a purpose built facility at Mertoun Paddocks, Newmarket in 1989, where it remained until its closure in 2007. During this period, Twink supervised many PhD students and post-doctoral researchers, most of whom went on to successful careers within the field of reproduction; all maintained links with Twink as part of the “EFU family”. Twink was appointed as the Jim Joel Professor of Equine Reproduction at the University of Cambridge in 1995 and “retired” from Cambridge in 2007. Not remotely interested in retiring and “taking it easy” Twink then established the Paul Mellon Laboratory of Equine Reproduction at his home in Newmarket (2008-2015). However the opportunity to set up the Equine Reproduction Laboratory at the Sharjah Equine Hospital, U.A.E. arose in 2015, where he established a small herd of research mares and was performing clinical work with his personal and professional partner Dr Sandra Wilsher until 2 weeks before his untimely death.

The enormous scope of Twink’s work is astounding and matched by the importance of his findings; thus no obituary would be complete without detailing some of the key milestones in his academic career. In the 1970s, Twink developed the first robust laboratory assay for equine chorionic gonadotrophin (eCG). This proved invaluable during his collaboration with Dr Bob Moor FRS which solved a decades old puzzle, namely that the chorionic girdle portion of the equine fetal membranes is the progenitor tissue of the unique equine endometrial cups, which are embedded in the endometrium of the pregnant mare; these are the source of the equine-unique protein hormone, equine Chorionic Gonadotrophin (eCG). This is present in large quantities in the blood of early pregnant mares and other equids (Days 40-120 of gestation). eCG is responsible for the development of secondary or accessory corpora lutea in the mare’s ovaries, which secrete progesterone and thus maintain the mare’s pregnant state until the diffuse epitheliochorial placenta is sufficiently well established to assume the role of progesterone production. Twink’s fascination with the endometrial cups, which are composed of fetal cells (and therefore contain genetic material of paternal and maternal origin) and the associated cellular immune response around the base of the cups, led to his pioneering work with Prof Doug Antczak; this illuminated unique aspects of the fetal-maternal immunological relationship. The intensity of the immune response also defined the pattern of eCG levels in horses, donkeys and their reciprocal interspecies hybrids, that presaged the discovery of genomic imprinting. Furthermore, the extra-species donkey-in-horse model of early pregnancy loss could be explained by a failure of the donkey chorionic girdle to invade the horse endometrium and thus led to failure of the endometrial cup formation and initiation of placentation.

In the early 1970s, with Prof Tim Rowson, Twink drove the development and practical application of both surgical and non-surgical methods of embryo recovery and transfer in the mare, which is now common in equine reproductive practice internationally. A typical adventure involved Twink, with Drs Francesca Stewart and Alan Trounson, transporting 6 horse embryos in the oviducts of two rabbits by car along the Berlin corridor to Krakow in Poland in 1974 for transfer to recipient mares. This in turn led to the birth of 3 live foals in 1975, all in close and enjoyable collaboration with Professors Wadslaw Bielanski and Marian Tischner of the Institute of Animal Physiology in Krakow. Twink also pioneered the application of embryo transfer to hasten genetic progress in horse breeds that permit its use. Then there was the production by between-breed embryo transfer of “deprived” Thoroughbred-in-pony and “luxurious” pony-in-Thoroughbred pregnancies to study the influences of maternal and placental size on the development of the foal. Twink also used embryo transfer to break new ground in the preservation of endangered species; in collaboration with the late Dr Phil Summers of the Zoological Society of London, they undertook heroic and spectacularly successful extra-species embryo transfers among member species of the genus Equus, including zebra and the endangered Przewalski’s horse. An extension of the embryo transfer technique involved the successful bisection and reconstruction of horse embryos to create a number of pairs of genetically identical twin foals, all in collaboration with Drs Steen Willadsen, Robert Pashen and Lulu Skidmore. Twink then lead two important spin-offs from these technically difficult experiments; further study of the unique equine capsule with Dr Julio Oriol and in 1989, the establishment of the Camel Reproduction Centre (CRC) in Dubai, under the governorship of Twink, along with Professors Roger Short and Brian Heap FRS, with Lulu as its Scientific Director. The pioneering research of the CRC has covered many topics including camelid ovarian follicular dynamics, pregnancy and placentation, endocrinology throughout the cycle and pregnancy, maternal recognition of pregnancy, embryology and semen collection and analysis. There has been particular emphasis on embryo transfer, management of recipients and bisection, cooling and deep freezing of camel embryos as well as semen collection and analysis and artificial insemination.

Twink was an early exponent of using reproductive hormones to advance and assist the onset of reproductive cyclicity in the Thoroughbred mare. Thus with Dr Mike Cooper and Ray Newcombe, he developed the practical application of prostaglandin F analogues (Equimate and Estrumate) to manipulate the oestrous cycle of the mare. This was followed by the successful trialling and application of allyl trenbolone (Regumate) and gonadotrophin-releasing hormone (GnRH) analogues (Deslorelin) to hasten reproductive cyclicity in the mare, all with the collaborative assistance of the stud farm veterinary practitioners in Newmarket, notably Peter Rossdale, Bob Crowhurst, Donald Simpson, Richard Greenwood and David Ellis.

Further examples of Twink’s ability to “think outside the box” was the determination, in collaboration with equine surgeon Huw Neal, that blockage of the oviducts in mares can be a cause of infertility, which can be simply overcome by the laparoscopic application of PGE2 gel to the external surface of the oviduct. And last, but certainly not least, in collaboration with Dr Eric Palmer, Twink initiated the early development and practical application of the technique of transrectal ultrasonography to Thoroughbred horse breeding; this has proved invaluable for the accurate visual assessment of follicular growth, ovulation and corpus luteum development and for the early accurate diagnosis of singleton and twin pregnancy and early pregnancy failure. This work was also carried out in collaboration with the Newmarket veterinary practitioners and the technique of “scanning” has since revolutionised horse breeding throughout the world. Moreover, as a direct result of many of these advances, Thoroughbred stallion fertility increased from just under 70% in the 1970s to well above 90% in the space of 20 years, largely because these techniques gave a detailed insight into the reproductive status of mares which failed to conceive after mating, meaning they could be covered more often and thus improve their chance of conception, within the relatively short breeding season.

Of course, this rather dry, factual information does little to describe the colourful personality that Twink was. No-one who met Twink could ever forget him! He travelled extensively, visiting many countries and virtually all continents where he made many, long lasting friendships. He had an unrivalled energy and “joie de vivre”, held very strong views about many subjects and loved nothing better than a robust discussion, usually around the kitchen table with a well-made i.e. strong gin and tonic, which continued through animated dinners, hosted with his wife Diana. He was a well-known figure around Newmarket and took great delight in following the careers of his three children and many grandchildren, including cheering on his son-in-law Frankie Dettori. However, the number and range of Twink’s friends throughout the world was truly astounding and once a friendship was made, it was loyal, steadfast and generous. Twink delighted in encouraging young scientists and if they worked hard, he gave them every opportunity and indeed the confidence to spread their wings and fly. He also revelled in asking probing questions at scientific meetings, but had an equal talent for communicating with horse owners and breeders; he was in his element when asking the local veterinary practices (Newmarket Equine Hospital and Rossdale and Partners), stud farm owners and managers what their equine reproduction problems were, doing the necessary scientific research and then hosting social evenings to report their outcome. Wherever he went, Twink integrated quickly and became a leader within the local community.

Many events were initiated by Twink, indeed he loved “a project” and approached them all with immense determination and energy. Perhaps his most notable legacy is the International Equine Reproduction Symposium (ISER). With the support of John Hughes, Doug Mitchell, Bill Pickett and Peter Rossdale, Twink organised and ran the First International Symposium of Equine Reproduction in Cambridge in July, 1974. The aim of the symposium was to provide a forum for biologists and veterinarians to exchange and argue their views, to review the present state of knowledge, to produce guidelines for future research, and to foster international friendship and collaboration. The first proceedings entitled “Equine Reproduction” were edited by I.W. Rowlands, W.R. Allen and P.D. Rossdale and published as a supplement of the Journal of Reproduction and Fertility. These symposia continue to be held every four years, with the abstracts published for posterity. In recognition of his immense contributions to equine reproduction, Twink was Honorary Chair of ISER VI in Caxambu, Brazil (1994) and delivered the John Hughes Memorial Lecture entitled “Sex, science and satisfaction: a heady brew” at ISER X (2010) in Lexington, Kentucky. It was fitting that Twink received the Lifetime Achievement Award at ISER XII (2018) in Cambridge, UK. Arising from his desire to encourage participation in ISER, Twink was instrumental in setting up the International Equine Reproduction Trust which raises funds to support young researchers’ travel to attend ISER, regardless of their financial circumstances. A completely different but equally notable project, demonstrating Twink’s commitment to his local community, was the establishment of a fund and appointment of a sculptor to erect the “Newmarket Stallion”, a bronze statue of a rearing stallion and handler on the roundabout adjacent to the July Racecourse; this is an eye-catching and fitting welcome to the “Headquarters” of the Thoroughbred flat racing and breeding industry in the United Kingdom.

Privately, in his younger days Twink loved to ride and gained his Thurlow Hunt “buttons” awarded for a substantial contribution to the hunt. He frequently attended the Rowley Mile and July racecourses in Newmarket, chatting to friends and trainers with obvious great enjoyment. His taste in music was diverse and he was equally at home listening to opera at the Metropolitan in New York or his beloved Robinson College choir in Cambridge or musicals; he was also a country and western devotee! Most will remember Twink’s exploits on the dance floor at scientific conferences, where he could jive to virtually any type of music, not stopping until he had danced with all the ladies present.

Twink enjoyed returning to New Zealand which he called “God’s Country” on a regular basis, visiting his family as well as his favourite childhood beach, Piha, on the west coast of Auckland. More recently, Coopers Beach in Northland became a favourite haunt. There, Twink would soak up some sunshine, swim, catch a snapper and “slurp some gin” with old friends. Always the educator and generous in spirit, Twink would make time to catch up with his Kiwi colleagues and give a seminar or two for the local vets and breeders. His visits were treasured, and every word, story or snippet was held in the highest esteem by everyone he met.

Twink was a unique character who had a profound influence on many lives. As the grandfather of equine reproduction, his death marks the end of an era and he will be sorely missed by his family and many friends. And many more far and wide will echo our thanks to Twink for all the amazing and happy experiences. But the spirit of Twink will survive in all his students, friends and colleagues. As a proud New Zealander, the last verse from one of his favourite songs “Pokarekare Ana” is poignant: “My love will never be dried by the sun, It will be forever moistened by my tears”. On behalf of everyone who had the honour of knowing and working with you, rest in peace my dear friend.

A small family funeral was held in Dubai, UAE on 15th June 2021.

If you would like to be informed of a future memorial event, please email Mrs Jan Wade: janwade@btopenworld.com

Donations towards the W.R. (Twink) Allen Young Researcher Fellowship can be made to the International Equine Reproduction Trust.

£ Sterling: Sort code: 20-60-38; Account number: 10513504

$US dollars: Sort code: 20-60-38; Account number: 48697766

E Euros: Sort code: 20-60-38; Account number : 88875966