Quantitative and Qualitative Assessment of Milk Production after Pharmaceutical Induction of Lactation in the Mare

Abstract

The induction of lactation is performed in ruminants by steroidogenic impregnation, followed by drugs intended to increase prolactin secretion. The aim of this study was to induce lactation in barren mares and to evaluate milk production. Five treated and 5 control mares were used in June and September in year 1, and 12 mares were used in year 2. Mares were administered a vaginal pessary (500 mg altrenogest and 50 mg estradiol benzoate) for 1 week. The 2nd week, another sponge with 100 mg estradiol benzoate was administered, together with 50 mg/100 kg body weight (BW) sulpiride in oil (IM q12h). All mares were milked by hand. Drug treatment was stopped after I L was obtained. Milk production and composition and plasma prolactin concentration were measured. In year 2, the same steroid treatment was applied, but mares received sulpiride (n = 6) or domperidone (1.1 mg/kg PO q12h) (n = 6). A milking machine and oxytocin injections 1 minute before the start of milking were used. In year 1, all treated mares started milking within 1-5 days after sulpiride treatment. Mean daily milk production was 0.88 +/- 0.52 L/500 kg BW. Milk immunoglobulin G (IgG) contents increased in all mares (IgG concentration range, 14-92 g/L). Plasma prolactin increased during sulpiride treatment (range. 27.7 +/- 2.9 to 43.7 +/- 6.7 ng/mL [before] to 289.0 +/- 7.8 ng/mL during treatment, P < .001). In year 2, results were similar to those in year 1, with peak IgG concentrations ranging from 4.2 to 106.7 g/L and a larger daily milk production (3.13 +/- 0.75 with sulpiride and 3.45 +/- 0.51 L/500 kg BW with domperidone). In conclusion, lactation can be induced in mares within 2 weeks, and some mares produce good-quality colostrum.

Successful Induction of Lactation in a Barren Thoroughbred Mare: Growth of a Foal Raised on Induced Lactation and the Corresponding Maternal Hormone Profiles

“…The obtained milk volumes per milking after correction for body weight were lower than those of naturally lactating mares [9], but were comparable with those of mares with induced lactation [2]. A previous report suggested that a mare with induced lactation was ready for adoption when milk production reached 3 to 5 l per day for a 500-kg horse [4].…”

“…In recent years, some reports have demonstrated that lactation without a preceding pregnancy has been induced using a treatment that includes estrogen, progesterone, and a dopamine D2 antagonist aimed at increasing prolactin (PRL) secretion in mares [2,6,31]; this has similarly been shown in cows [1,3,30]. Furthermore, another study has shown that there is no significant difference in body weight between the foals adopted by mares with induced lactation and the control foals that remained with their natural mothers at the age of weaning [4].…”

Pharmacological Overview of Galactogogues

“…Adverse effects reported in women were headache, fatigue, extrapyramidal symptoms, acute dystonic reactions, and endocrine disruption [2, 50]. In equine, sulpiride used at dose of 1.1 mg/kg PO twice a day [54] and 0.5 mg/kg intramuscularly (IM) twice a day increased PRL blood concentration and milk production [38]. …”

Ovarian and PGF2α responses to stimulation of endogenous PRL pulses during the estrous cycle in mares

“…Sulpiride, a dopamine receptor antagonist, stimulates PRL secretion. In mares, most studies using sulpiride treatments have involved lactation [19,20] and the anovulatory and ovulatory seasons [9,21,22]. Increasing PRL concentrations by dopamine antagonists stimulates ovarian follicular development and hastens the first ovulation of the ovulatory season [21,22].…”