An update on artificial induction of lactation in domestic animals

Introduction

In the last decades, genetic selection of dairy cows for high milk yield has negatively affected fertility, increasing the culling rates of animals due to reproductive failure. Infertility is considered one of the main reasons for culling and is among the costliest factors in dairy farms, involving direct costs associated to rearing or purchasing the animals, and indirect costs related to maintenance of unproductive animals in the system (Pritchard et al., 2013) [49] . In the year 2024-25 India's total milk production was 247.87 million tonnes, per capita milk availability of milk was 485 grams/day. During the same year total milk production of Gujarat was 19.28 million tonnes (BAHS, 2025) [16] . India remains the world's leading milk producer, contributing 24.76% of global output, yet reproductive inefficiency remains the primary silent economic drain (PIB, 2025) [48] . The annual growth rate of milk production is declining since last 5 years (Graph 1, BAHS, 2025) [16] . Major cause behind this declining growth is reduced per animal milk production. The average yield per animal per day in India is 9.05 kg/day/animal (Exotic/crossbred) and 3.86 kg/day/animal (BAHS, 2025) [16] . The surveillance of breedable zebu cattle, crossbred cattle and buffaloes (total 28,815) from 5 different regions of Gujarat revealed reproductive problems in 27.4, 26.6 and 34.5% animals, respectively. Among these infertile animals, the incidence of anestrus was maximum (23.34%) followed by repeat breeding (14.94%), subestrus (14.69%), uterine infection (12.91%), infantile genitalia/pubertal anestrus (9.64%) (Dhami et al., 2022) [17] . Over half of the cow population in repeat breeding animals are in productive years, aged 4-6 years, only 44.8% having 1 or 2 offspring(s) (Pongkapadang et al., 2025) [47] . As a solution to tackle this condition Artificial induction of lactation (AIL) aims to allow heifers and cows with superior genetic value that fail to conceive to remain in the herd, generating revenue until a new breeding opportunity arises (Busanello, 2025) [5] . Artificial induction of lactation is a physiological intervention that uses exogenous hormone treatments to stimulate mammary gland development (mammogenesis) and initiate milk secretion (lactogenesis) in non-pregnant, intact mammals (Noguchi et al., 2020) [43] . Artificial induction of lactation with the use of synthetic hormones which are likely natural mainly at the end of the pregnancy, ulating the physiological system of the animal a pregnancy and stimulating milk production (Freitas et al., 2010) [18] . Formation of normal colostrum can be achieved by injecting estrogen and progesterone and both the hormones are involved in control of selective transport of serum immunoglobulin into milk (Smith, 1971) [54] .

Status of artificial induction of lactation Global status

Globally, Artificial Induction of Lactation (AIL) is primarily utilized to maximize the lifetime productivity of genetically superior dairy cattle, particularly high-yielding breeds such as Holsteins, that fail to conceive following a dry period. Contemporary global approaches increasingly integrate AIL with advanced dairy technologies, including Automatic Milking Systems (AMS), reflecting a trend toward precision dairy management (Busanello, 2025) [5] . Standard global protocols commonly involve short-duration regimens, particularly 8-day protocols, often supplemented with Recombinant Bovine Somatotropin (RBST) to enhance lactational performance (Busanello, 2025) [5] . Success rates of induced lactation under global conditions generally range between 80% and 100%, with milk production achieving approximately 78-80% of natural lactation yields (Busanello, 2025) [5] . Furthermore, reproductive performance following induction has shown encouraging outcomes, with postinduction pregnancy rates reported to range from 41% to 71% (Ramgattie et al., 2014) [50] . Recent international research trends indicate a marked transition toward shortened protocols designed to reduce estradiol exposure, minimize treatment costs and improve animal welfare by limiting prolonged estrus-associated behavioral stress (Isola et al., 2024) [23] .

Status in India

In India, the application of artificial induction of lactation differs considerably from global objectives and is primarily directed toward preventing involuntary culling and addressing the growing stray cattle problem, influenced by cultural values and legal restrictions on cow slaughter (Lakhani et al., 2017) [32] . AIL serves as an important rehabilitative strategy for barren and nonproductive animals, restoring them to economic usefulness and converting financial liabilities into productive dairy assets (Inchaisri et al., 2010) [21] . Indian protocols generally rely on traditional 7-21-day induction schedules, with hormonal formulations tailored according to breed type. Crossbred cattle are typically managed using an estrogen-to-progesterone ratio of 1:2.5, whereas indigenous cows and buffaloes commonly receive a 1:1 ratio (Lakhani et al., 2017) [32] . Reported success rates in India range between 80% and 85%, although buffaloes frequently demonstrate comparatively lower responses to induction protocols. Milk yield following induction generally reaches 60-70% of natural lactation, which has been attributed to uncoupling of the somatotropic axis during induced lactation. Reproductive outcomes after induction indicate that many repeat-breeder cows regain normal estrous cyclicity, although conception rates remain moderate to relatively low under field conditions.

Mechanism of artificial induction of lactation

Artificial Induction of Lactation (AIL) is based on sequential hormonal stimulation intended to induce mammary development, initiate milk secretion and maintain lactation. Although AIL does not perfectly reproduce the endocrine profile of natural pregnancy, it utilizes key hormonal pathways involved in lactogenesis and galactopoiesis. Artificial induction protocols are primarily based on administration of estradiol, progesterone, prostaglandins, corticosteroids and bovine somatotropin. The initial phase of AIL relies on estradiol and progesterone administration to stimulate mammary gland development. These hormones promote the mammogenic changes necessary for lactation induction. Following this developmental phase, prostaglandins and corticosteroids are incorporated to facilitate transition toward milk secretion. Dexamethasonebased treatments are used during the final stage of induction to stimulate lactogenesis and trigger milk secretion. Endogenous prolactin release is an important component of the induction process. Stimulation of the mammary gland through massage or milking adaptation is used to promote prolactin release and support initiation of milk production. Busanello (2025) [5] notes that mammary gland massage was used specifically for endogenous prolactin liberation and further discusses that prolactin stimulation contributes to milk secretion. Maintenance of lactation after induction depends on continued stimulation of the mammary gland and hormonal support. Bovine somatotropin has been reported to improve milk yield responses through stimulation of epithelial cell proliferation and regulation of apoptosis, thereby contributing to maintenance of milk production. Additionally, increased milking frequency may provide further stimulation to sustain milk yield during induced lactation. (Busanello, 2025) [5]

Indications for artificial induction of lactation Mitigating involuntary culling

Reproductive failure is the leading cause of involuntary culling in Indian herds. In the context of India's record milk production of 247.87 million tonnes (2024-25), but with rising population, need of more production will also rise significantly (BAHS, 2025) [16] . That's why using AIL protocols in cows which are in their productive year and not conceiving.

Clinical utility in companion & lab animals

Dogs & Cats: In maternal death, AIL using dopamine antagonists (e.g., Metoclopramide, Domperidone), enables a non-parturient surrogate or the biological dam to produce milk, to synchronize milk production for orphaned neonates in small animals. In swine, employed as a colostrum supplement for large litters and Equines (Nurse Mares): In high-value Thoroughbred breeding, for the creation of "nurse mares" to foster orphaned foals. (Noguchi et al., 2020; Podico et al., 2022) [43,46] Research and Biotechnological applications Transgenic animals: AIL is a prerequisite for testing the milk of transgenic animals (e.g., for human therapeutic proteins) as early as 13 months of age, bypassing the long gestation and age at first calving delays. Pharmacokinetic Benchmarking: Provides a controlled physiological model to establish Hormonal Clearance Windows (typically 15-30 days) for public health safety). (Monzani et al., 2024) [41] Other indications: Prevents involuntary culling of highpedigree animals failing to conceive, Bypasses the 9-month (280-310 day) non-productive gestation lag, Exogenous steroid priming (E2/P4) can reset the hypothalamic-pituitaryovarian axis. 40-60% of induced cows subsequently conceived, In buffaloes to bypass silent heat and summer infertility, Addresses chronic conditions like Cystic Ovarian Disease (COD) or persistent anestrus, To study mammogenesis and lactogenesis without the metabolic interference of a developing fetus.

Selection of Animals

Selection of animals for artificial induction of lactation should be based on several physiological and management criteria to optimize treatment success. Animals with a body condition score (BCS) of 3.25-3.75 on a 5-point scale are preferred, as they possess adequate energy reserves necessary for galactopoiesis. Multiparous animals, particularly those in the 2nd to 4th lactation, are considered ideal candidates because they possess more developed mammary ductal frameworks. Dry and non-pregnant animals are preferred to permit adequate systemic recovery before induction. Udder health is another critical criterion, and only animals with clinically healthy quarters, no history of mastitis and somatic cell counts below 200,000 cells/ml should be selected. Anatomical integrity, particularly sound teat morphology, is necessary to ensure effective mechanical milking stimulation. Animals should also possess a docile or trainable temperament to facilitate management throughout the treatment period. In addition, candidates should be properly vaccinated, dewormed and free from systemic diseases to support overall health and treatment response. (Lakhani et al., 2017) [32] Protocols

Photoperiod Manipulation

Photoperiod manipulation involves the strategic control of daily light and dark cycles to exogenously influence neuroendocrine pathways. In the context of domestic ruminants, the primary clinical and commercial goal is to stimulate, enhance, or restore lactation (galactopoiesis) by manipulating the biological circadian rhythms that dictate hormone secretion, often utilized as a synergistic adjunct to pharmacological artificial induction of lactation (AIL) protocols. Photoperiod manipulation begins with environmental light exposure, which is detected by intrinsically photosensitive retinal ganglion cells (ipRGCs) in the retina. The light signal is then transmitted through the retinohypothalamic tract to the suprachiasmatic nucleus (SCN) of the hypothalamus, the primary circadian regulator. Activation of the SCN suppresses sympathetic stimulation of the pineal gland, resulting in inhibition of melatonin synthesis. Consequently, circulating melatonin concentrations, the principal biochemical signal of darkness, are reduced. This reduction in melatonin subsequently modulates endocrine pathways, leading to altered prolactin secretion from the anterior pituitary gland and regulation of insulin-like growth factor-I (IGF-I) production through the somatotropic axis in the liver. (Dahl et al., 2000; Li et al., 2025) [14,33] Long-Day Photoperiod (LDPP): LDPP typically consists of 16-18 hours of light and 6-8 hours of darkness.

Physiological Effects: Sustained suppression of melatonin secretion. Increased circulating prolactin and IGF-I concentrations.

Results in enhanced metabolic and endocrine signals supporting active milk synthesis. Enhanced metabolic and endocrine signals supporting active milk synthesis and average increase of 2 to 3 kg/day (Lacasse et al., 2016) [30] .

Short-Day Photoperiod (SDPP): SDPP typically consists of 8 hours of light and 16 hours of darkness.

Physiological Effects: Increased systemic melatonin concentrations, Reduced circulating prolactin levels. Upregulation of target-tissue receptor expression, particularly prolactin receptors in mammary tissue. Roughly 40 to 60 days prior lactation. Results in subsequent 3 to 4 kg/day increase in milk yield when transitioned back to LDPP (Crawford et al., 2015) [12] .

Phytotherapy

Phytotherapy involves the use of plant-derived compounds (herbal galactagogues) to stimulate, maintain or augment milk production. With the rising global demand for organic dairy products and the strict regulation of synthetic galactopoietics like recombinant bovine somatotropin (rBST), phytotherapy offers a viable, non-hormonal and cost-effective alternative that leaves no toxic pharmacological residues in the milk (Patel et al., 2017) [45] .

Mechanism of action: Phytoestrogenic Effects: Steroidal sapogenins structurally mimic endogenous estradiol. Bind to estrogen receptors, prompting proliferation of mammary epithelial cells & ductal branching (Kumar et al., 2014) [29] , Rumen Kinetics and Nutrient Partitioning: Saponins stimulate anaerobic fermentation in the rumen, modifying the volatile fatty acid (VFA) profile. This increases the post-ruminal availability of bypass proteins and gluconeogenic precursors required for milk lactose and protein synthesis (Li et al., 2023). [51] Galactomannans, Diosgenin, Trigonelline: Potent phytoestrogenic activity.

Increases daily milk volume & elevates fat and protein percentages.

Anise (Pimpinella anisum) Fennel (Foeniculum vulgare) (Iommelli et al., 2025) [22] Anethole (phytoestrogen) Inhibit dopamine receptor. Increase serum prolactin levels & stimulate lactogenesis.

Included in commercial polyherbal galactagogue formulations such as Payapro and Galactin Vet.

Moringa (Moringa oleifera) (Kholif et al., 2016) [27] Rumen-bypass protein, essential amino acids: Enhances rumen microbial protein synthesis & improves nutrient availability for milk production. Mare: Foaling sometimes results in an orphan foal. To raise an orphan foal, it is necessary to find an alternative milk source such as bottle-feeding or acquiring a nurse mare. The induction of lactation can offer practical and economical advantages. 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 diet should contain a higher proportion of concentrate. These mares were not previously pregnant, so their physiological adaptation differs from normal postpartum mares. They may not consume large volumes of feed like postpartum mares. Increasing dietary concentrate helps meet energy and nutrient demands (Daels, 2006) [13] .

Dried moringa leaves Moringa leaf extract increased milk yield by 65%

Selection of mares: Mare must have given birth and successfully nursed a foal at least once in their life, Mares that have raised several foals tend to have a mammary gland that is more developed and a more predictable maternal behavior, Mares must be in good body condition (BCS 5-6 on 1-9 scale), free of disease and mammary abnormalities, gentle and calm, must be willing to stand confined behind a contention bar for prolonged periods of time and have a history of being a "good mother", The success does not seem to be influenced by the age of the mare nor by the interval since the last foaling (Daels, 2006) [13] Pre-treatment Management: Mare should be fed as a natural nursing mare from Day 1 of treatment, Before initiating hormonal therapy maintain mare under artificial photoperiod for \~8 weeks (14.5 h light, 9.5 h darkness) Purpose: Advance cyclicity Improve prolactin response to sulpiride (Korosue et al., 2012) [28] Adoption: Introduction to foal 1. The discipline method: The disciplinary action is a ple action-reaction technique by which the mare is discouraged to act against the foal. Gradually the actions shift from physical action to voice cues and within hours mares were conditioned not to react when the foal attempted to nurse.

Vaginal method:

The foal held near the mare's head while vaginal-cervical stimulation performed through vigorous massage of the external cervix with slight dilation attempts. This was done twice for two minutes at a ten-minute interval. During and after stimulation, the foal remained close to the mare's head and shoulder to allow sniffing and licking.

Sow: Inducing lactation in non-pregnant pigs is explored as a way to manage modern production challenges, such as Large Litter Sizes: Genetic selection has increased litter sizes beyond the capacity of a single sow's natural colostrum supply. Piglets require at least 200g of colostrum in the first 24 hours, it can reduce culling rates and replacement costs due to reproductive failure. (Noguchi et al., 2020) [43] [11] Dogs and Cats: Artificial induction or pharmacological stimulation of lactation is required when milk production is absent or inadequate during the neonatal period. The neonatal stage in dogs and cats is critical for survival, growth, and immune protection. In carnivores, early neonatal immunity and development depend heavily on maternal mammary secretions. Failure of normal lactation therefore becomes a clinically significant reproductive and neonatal management problem. Postpartum lactation disorders may occur in small animals, including agalactia (absence of milk secretion), hypogalactia (insufficient milk production). In such situations, pharmacological stimulation of lactation may be required to support neonatal survival and reduce dependence on artificial rearing (Jensen, 2016) [25] . Continued milk production therefore requires adequate hormonal stimulation and suckling stimulus. (Orfanou et al., 2010) [44] .

Prolactin: Primary hormone regulating milk synthesis in mammals, Dopamine: physiological inhibitor of prolactin, Dopamine Inhibitors: increase prolactin concentrations & stimulate milk production, these drugs remove dopaminergic inhibition of prolactin release, thereby stimulating lactogenesis (Jensen, 2016) [25] .

Protocols Used in Bitches (Metoclopramide protocol)

In bitches, a metoclopramide protocol can be used to stimulate lactation by administering metoclopramide, a dopamine antagonist, at a dose of 0.2-0.5 mg/kg orally or subcutaneously every 8 hours for 5-10 days, or until adequate milk production is achieved; its mechanism of action involves dopamine receptor blockade, which increases prolactin secretion and thereby promotes lactogenesis, while frequent suckling by puppies is necessary to maintain prolactin release, and adequate hydration and nutrition of the dam are essential for successful milk production. (Keller et al., 2018) [26] Milk Residues and Effects on Animals in Artificial induction of lactation Following artificial induction of lactation, estradiol residues decline rapidly after treatment cessation and return to physiologic levels, with a Maximum Residue Limit (MRL) of 0.04 µg/kg, while progesterone, an endogenous hormone with no established MRL, may accumulate temporarily in milk fat because of its lipophilic nature but returns to baseline concentrations after protocol withdrawal. Estradiol and progesterone residues generally peak within the first 7 days and decline to baseline levels within 14-21 days; therefore, a milk withdrawal period of 21-30 days after protocol initiation is recommended. Dexamethasone has an MRL of 0.3 µg/kg and is rapidly eliminated, resulting in only short-term concentrations in milk fat, with residues typically declining to safe levels within 72-96 hours after administration (Zanatta et al., 2022; Busanello, 2025) [58,5] . (Gümen and Wiltbank, 2002) [20] Cystic Ovarian Disease (COD): High E2 doses disrupt the LH surge Metabolic Stress (Churakov et al., 2021) [9] Negative Energy Balance (NEB): Induced animals lack the gradual metabolic adaptation of late pregnancy, leading to acute spikes in NEFA.

Skeletal System (Abuelo, 2025) [1] Hypocalcemia: a sudden increase in calcium excretion to support colostrum and milk production, straining calcium homeostasis. Behavioral Changes (Noguchi et al., 2020) [43] Persistent Estrus (Nymphomania): Exogenous Estrogen Benzoate induces "bulling" behavior, leading to physical injuries or mounting trauma.

Conclusion

Artificial induction of lactation is an effective physiological strategy for initiating milk production in non-pregnant animals through controlled exogenous hormonal manipulation. When combined with appropriate animal selection, it serves as a valuable tool in modern veterinary reproduction, dairy herd management and biotechnological research. Beyond cattle, artificial lactation induction has practical applications in nurse mare programs for foal fostering, management of agalactia in canines and support of orphan rearing in sheep and goats. Adjunctive approaches such as photoperiod manipulation and phytotherapy may further enhance milk yield and lactational performance. Artificial induction protocols can also facilitate production of normal colostrum, while the quality and composition of milk produced are generally comparable to those obtained during natural lactation. Milk yield typically reaches approximately 60-80% of that achieved during natural lactation. Furthermore, potential hormonal residues in milk can be effectively managed through adherence to appropriate withdrawal periods.

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