Volume 12: Livestock Farming
5. Breeding programmes and techniques
Breeding management on farm
Fertility management
Use of artificial insemination on farm
Use of embryo transfer on farm

Fertility management

5.11 To achieve maximum annual output of milk from each cow, dairy farmers must ensure that each cow produces one calf per year. To this end, management of cow fertility has become an important aspect of dairy farming. Pregnancy lasts nine months, and cows are unlikely to recommence their 'oestrus' cycles less than two months from the date of calving. It is therefore generally agreed that the optimal average interval between calvings is 365 days. ¹ Calving is usually timed to occur in either autumn or spring, although in some herds, especially dairy herds, calves can be born throughout the year. ²

5.12 To ensure conception, mating needs to take place when the cow is in the fertile part of her reproductive cycle, that is, during oestrus. To get the timing right, the manipulation of ovarian activity is widely practised in livestock farming. ³ There are two options for the controlling the timing of oestrus in cows or heifers:

1. an injection of prostaglandin (PG) to bring the cow into heat within three to four days; or
2. administering progesterone to inhibit oestrus for a period of time, so that the cow comes into heat within two to three days of withdrawing the progesterone. ⁴

Use of artificial insemination on farm

5.13 Farmers in the UK have used AI since the 1940s, and by the end of 1950 there were almost 100 AI centres in operation serving over 60,000 farms. ⁵ About 1.9 million inseminations were performed across all breeds in the UK in 1986, increasing to over 2.1 million by 1994. ⁶ The vast majority of commercial dairy herds are now bred using AI. ⁷

5.14 AI services are regulated and subject to MAFF supervision to ensure high health standards and quality in the industry (see paragraphs 5.27-5.29).

Use of embryo transfer on farm

5.15 Embryo transfer involves transferring an embryo from one animal and implanting it in the uterus of another. It is a means of producing a large number of offspring from a single cow with desirable characteristics, such as high milk yield. It was introduced in the 1970s, and can now be carried out on the farm, non-surgically, and without anaesthetic. ⁸

5.16 The technique involves administering gonadotrophins to the donor cow to cause superovulation. These can be either Pregnant Mare Serum Gonadotrophin (PMSG), or pituitary Follicular Stimulating Hormone (FSH).

5.17 It is important to synchronise the donor's and recipient's oestrus, which may involve the use of hormones (see paragraph 5.12). When oestrus occurs, insemination of the donor cow is carried out two or three times. Embryos are collected from the donor cow seven or eight days after insemination, and eachis transferred to a surrogate cow, which carries the embryo for the rest ofthe pregnancy. ⁹

5.18 The Inquiry has received conflicting views on the source of FSH used for inducing superovulation in embryo transfer. On the one hand, it would appear that cattle pituitaries were used to prepare FSH. In the Veterinary Record in July 1988, members of the Veterinary Products Committee advised against this practice, in view of the possible risks of transmission of BSE. ¹⁰ Dr Thomas Little, Chief Executive of the Central Veterinary Laboratory (CVL), also thought that cattle tissue might have been used to prepare FSH. ¹¹ On the other hand, Mr Harry Coulthard, a veterinary surgeon, said that using cattle pituitaries to produce FSH had been considered in the past, but that the cost and difficulty in doing so in comparison with using pig and sheep pituitaries was prohibitive. Accordingly, he was certain that no cattle-derived FSH had been used in embryo transfer. ¹²

5.19 If cattle pituitaries had been the source of FSH, their use could have had implications for the transmission of BSE. The use of cattle products as raw materials for animal and human medicines is discussed in vol. 7: Medicines and Cosmetics.