Equibreed NZ loves a challenge and researching practical questions that will help our breeders optimise results is one of the most exciting aspects of our work. Some of the projects that we are involved in are:

The effects of weather on the predictability of ovulation

Stallion fertility and dietary supplementation

Epididymal sperm - freezing and fertility

Sex-sorted stallion sperm and its fertility



1: McConaghy FF, Green LA, Colgan S, Morris LH. Studies of the pharmacokinetic profile, in vivo efficacy and safety of injectable altrenogest for the suppression of oestrus in mares. Aust Vet J. 2016 Jul;94(7):248-55.

2: Gibb Z, Grupen CG, Maxwell WM, Morris LH. Field fertility of liquid stored and cryopreserved flow cytometrically sex-sorted stallion sperm. Equine Vet J. 2017 Mar;49(2):160-166.

3: Gibb Z, Morris LH, Maxwell WM, Grupen CG. Dimethyl formamide improves the postthaw characteristics of sex-sorted and nonsorted stallion sperm. Theriogenology. 2013 Apr 15;79(7):1027-33.

4: Gibb Z, Butler TJ, Morris LH, Maxwell WM, Grupen CG. Quercetin improves the postthaw characteristics of cryopreserved sex-sorted and nonsorted stallion sperm. Theriogenology. 2013 Apr 1;79(6):1001-9.

5: Clulow JR, Buss H, Evans G, Sieme H, Rath D, Morris LH, Maxwell WM. Effect of staining and freezing media on sortability of stallion spermatozoa and their post-thaw viability after sex-sorting and cryopreservation. Reprod Domest Anim. 2012 Feb;47(1):1-7.

6: Gibb Z, Morris LH, Maxwell WM, Grupen CG. Use of a defined diluent increases the sex-sorting efficiency of stallion sperm. Theriogenology. 2011 Mar 1;75(4):610-9.

7: Clulow JR, Evans G, Maxwell WM, Morris LH. Evaluation of the function of fresh and frozen-thawed sex-sorted and non-sorted stallion spermatozoa using a heterologous oocyte binding assay. Reprod Fertil Dev. 2010;22(4):710-7.

8: Clulow JR, Evans G, Morris LH, Maxwell WM. Factors influencing the "sortability" of stallion spermatozoa into X- and Y-chromosome bearing populations. Anim Reprod Sci. 2009 Jul;113(1-4):220-8.

9: Clulow JR, Mansfield LJ, Morris LH, Evans G, Maxwell WM. A comparison between freezing methods for the cryopreservation of stallion spermatozoa. Anim Reprod Sci. 2008 Nov;108(3-4):298-308.

10: Clulow JR, Buss H, Sieme H, Rodger JA, Cawdell-Smith AJ, Evans G, Rath D, Morris LH, Maxwell WM. Field fertility of sex-sorted and non-sorted frozen-thawed stallion spermatozoa. Anim Reprod Sci. 2008 Nov;108(3-4):287-97.

11: Clulow JR, Maxwell WM, Evans G, Morris LH. A comparison of duck and chicken egg yolk for cryopreservation of stallion sperm. Aust Vet J. 2007 Jun;85(6):232-5.

12: Buss H, Clulow J, Sieme H, Maxwell WM, Morris LH, Sieg B, Struckmann C, Rath D. Improvement of the freezability of sex-sorted stallion spermatozoa. Anim Reprod Sci. 2005 Oct;89(1-4):315-8.

13: Weston VL, McLeay L, Morris LH. The in vitro response of equine epididymal and ejaculated spermatozoa to caffeine. Anim Reprod Sci. 2005 Oct;89(1-4):272-5.  

14: Morris LH. Challenges facing sex preselection of stallion spermatozoa. Anim Reprod Sci. 2005 Oct;89(1-4):147-57. Review.

15: Morris LH. Low dose insemination in the mare: an update. Anim Reprod Sci. 2004 Jul;82-83:625-32. Review.

16: Morris LH, Tiplady C, Allen WR. Pregnancy rates in mares after a single fixed time hysteroscopic insemination of low numbers of frozen-thawed spermatozoa onto the uterotubal junction. Equine Vet J. 2003 Mar;35(2):197-201.

17: Morris LH, Randall AE, King WA, Johnson WH, Buckrell BC. The contribution of the male to ovine embryogenesis in an in vitro embryo production system. Anim Reprod Sci. 2003 Jan 15;75(1-2):9-26.

18: Morris LH, Allen WR. An overview of low dose insemination in the mare. Reprod Domest Anim. 2002 Aug;37(4):206-10. Review. PubMed PMID: 12173985.

19: Li X, Morris LH, Allen WR. In vitro development of horse oocytes reconstructed with the nuclei of fetal and adult cells. Biol Reprod. 2002 May;66(5):1288-92.

20: Lindsey AC, Morris LH, Allen WR, Schenk JL, Squires EL, Bruemmer JE. Hysteroscopic insemination of mares with low numbers of nonsorted or flow sorted  spermatozoa. Equine Vet J. 2002 Mar;34(2):128-32.

21: Morris LH, Allen WR. Reproductive efficiency of intensively managed Thoroughbred mares in Newmarket. Equine Vet J. 2002 Jan;34(1):51-60.

22: Li X, Morris LH, Allen WR. Influence of co-culture during maturation on the developmental potential of equine oocytes fertilized by intracytoplasmic sperm injection (ICSI). Reproduction. 2001 Jun;121(6):925-32.

23: Li X, Morris LH, Allen WR. Effects of different activation treatments on fertilization of horse oocytes by intracytoplasmic sperm injection. J Reprod Fertil. 2000 Jul;119(2):253-60.

24: Morris LH, Hunter RH, Allen WR. Hysteroscopic insemination of small numbers of spermatozoa at the uterotubal junction of preovulatory mares. J Reprod Fertil. 2000 Jan;118(1):95-100.

25: Morris LH, Fairles J, Chenier T, Johnson WH. Segmental aplasia of the left paramesonephric duct in the cow. Can Vet J. 1999 Dec;40(12):884-5.



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Welcome to the first frozen embryo foal born in New Zealand - by Orame VDL for East Coast Performance Horses. Embryo freezing is now a reality in New Zealand! This option opens up so many opportunities for our breeders. Embryo freezing means that we can collect and freeze the embryo while your mare is in competition or still at home with its foal. The embryo can be "made at EquiBreed NZ" or shipped to EquiBreed NZ. The surrogate mare can be organised at a time that suits the breeder and only one surrogate (recipient) mare is needed for each embryo instead of the 2 mares that we traditionally set up. This saves the breeder lots of money! It is also possible to include embryo freezing in fertility programmes for tricky mares or late foaling mares. So you can freeze embryos anytime between Sept - May to fit in with your busy schedule and then transfer them into a surrogate this season or next season. Contact Dr Lee Morris to discuss how this new technology works for you.

Talk to the team