Induction of Lactation and Adoption of Orphan Foals

Introduction

When facing an orphan foal due to the death of the mare or unwillingness to accept her foal, it is critical to find an alternative to feed the foal and create a suitable social environment for the upbringing of the foal. Most of the time, a nurse mare that will raise the foal as her own can be located. In some regions of the country, specialized farms offer nurse mares. But, in other areas, locating a nurse mare can be difficult. Other options include feeding a replacement formula using a bottle or bucket. There are excellent milk replacements on the market that enable us to feed an orphan foal to weaning age with excellent body development. However, prolonged bottle-feeding of an orphan foal often results in a horse with poor social skills that can interfere with its future use.

The induction of lactation can offer practical and economical advantages. Lactation has been induced in ruminants using steroids (progesterone and estrogen) as a short-term treatment followed by a wide variety of drugs aimed at increasing prolactin secretion. These treatment protocols have resulted in lactation with milk production ranging between 25 and 82 % of a physiological, post-partum lactation. As a general observation, an induced lactation does not start with a production of colostrum. Several products (domperidone and sulpiride) have been used in recent years to increase endogenous prolactin secretion in mares either to advance the onset of reproductive activity in anestrous mares in early spring or to counter the ill effects of fescue toxicosis in pregnant mares at term.

Lactation can be induced in non-parturient mares that have foaled in previous years using a treatment that includes estrogen, progesterone and a dopamine D2 antagonist (sulpiride or domperidone). The initial treatment protocol for induction of lactation in mares consisted of a 2-wk treatment in which progesterone, estrogen, and a dopamine D2 antagonist (sulpiride) were administered daily. Mares were milked 1-2 days after the start of sulpiride treatment, and in some experiments, milking was continued after the end of treatment. The results of these studies indicated that lactation can be induced in mares that have foaled in previous years. Perhaps the most encouraging observation was that when regular milking (6-7x per day) was continued after the end of hormonal treatment, milk production continued at a constant rate for 7 or more days (see Figure 1).

A comparison between sulpiride and domperidone indicated that both products are effective in inducing milk production. The quality of the milk produced during these induced lactations appeared similar to a normal post-parturient lactation even though the production of colostrum was only observed occasionally (2). Several attempts have been made to induce the production of colostrums but so far results have been disappointing and do not warrant inducing a mare for the purpose of producing colostrums.

More recent studies indicate that progesterone and/or estrogen are essential for the induction since a treatment based on sulpiride administration only does not induce lactation in [...]