Estrogen, progesterone, prolactin and glucocorticoids work synergistically at the onset of lactogenesis. Estrogen stimulates mammary ductal growth, and the combination of estrogen and progesterone regulates lobular-alveolar development of the mammary gland. This development does not occur in infertile animal or animals suffering from reproductive disorders due to relative absence of sex steroid hormones. Artificial induction of lactation can be induced in such animals by the combination of steroid hormones estrogen and progesterone. Additionally reserpine (tranquilizer- increases prolactin level) and dexamethasone (a synthetic glucocorticoid) can be used in induction protocols to increase the success rate. Artificial induction reduces the involuntary culling rate as well as the genetic losses. To save such genetically superior bovines, induction of lactation is the most appropriate technology used under Indian conditions. The treatment is more effective in well-fed animals with good body condition score and having normal teat and udder. Hormonal induction of lactation should be practice only in infertile animals; it should not be followed as a routine practice, as an alternate to normal lactation. Estrogen and progesterone in 1:2.5 ratios is effective in exotic and cross bred while 1:1 ratio is effective in indigenous cows and buffaloes for artificial induction because of short luteal phase. These methods of artificial induction of lactation yield 60 to 70% milk of previous lactation.
India, the largest producer of milk in the world, producing 146.3 million tones with per capita availability of 322 gm/day in 2014-2015 (DAHD&F).With increase in population the demand for milk and milk products will also increase. Decline in milk production and productivity of dairy animals may cause problem of food insecurity (FAO, 2009). Poor reproductive performance is main cause for limiting productivity of dairy cattle. 10 to 30% of lactation may be affected by infertility and reproductive disorders (Erb and Martin, 1980). Poor reproductive performance represents a significant loss to the producer. Economic benefits through sale of milk can be achieved from artificial induction besides establishment of normal reproductive cycles in anestrus or repeat breeder cows and prolonging the lifespan of genetically superior cows for milk yield. Artificial induction of lactation can reduce herd culling, economy losses and replacement costs derived from reproductive failure (Inchaisri et al., 2010).This is particularly important in tropical countries, where reproduction efficiency is seriously compromised (Walsh et al., 2010).The average milk yield per lactation in hormonally induced cows is about 90% of cows whose lactation derives from calving and this level of milk yield is high enough for keeping overall herd efficiency (Mellado et al., 2011). But, artificial induction should be considered as last option for initiating lactation in cows or buffaloes. Transgenic animals have been used for synthesis and secretion of therapeutic and nutritional proteins (Ayares, 2000). Artificial induction in heifers can significantly reduce the time required before collection of milk for biochemical testing of valuable pharmaceutical proteins in their milk. Artificial induction can also help in reducing the population of stray animals through rehabilitation and opportunity for exploiting high producing animals.
It is a combined process of milk secretion and its removal from mammary gland. Milk production is both an endocrine and exocrine function. It has two phases namely- Lactogenesis (initiation of lactation by prolactin, glucocorticoids) and Gatactopoiesis (maintenance of lactation by growth hormone). Other factors affecting milk composition includes breed, genetic variation within breed, health, environment, management practices, and diet of the animal.
Earlier, ovarian hormones estrogen and progesterone, alone or in combination were used to develop the mammary gland and initiate lactation (Hammond, 1944; Collier, 1976; Chakriyarat, 1978; Peel, 1978). Mammary duct growth is stimulated by estrogen, while estrogen and progesterone in combination stimulate lobule-alveolar development of the mammary gland (Tucker, 2000). Low average level of plasma concentrations of estrogen and progesterone before treatment were found in successfully induced cows (Erb et al., 1976). After the last day of 17β-estradiol and progesterone injection, progesterone declined rapidly and estrogen declined 7 d after treatment. This indicates that induced lactations are being more successful if cows started the lactation-induction treatment 3 to 8 d after estrus accompanied by ovulation (Erb et al., 1976). Success rates can be increased by using Reserpine, a tranquilizer that increases blood prolactin, and dexamethasone, a synthetic glucocorticoid, but these have not reduced the variation in milk yields recorded from induced cows (Collier, 1977; Chakriyarat, 1978; Peel, 1978). Glucocorticoids play a role in mammary gland development, leading to alveolar cell differentiation of the gland. Glucocorticoids compete with progesterone for mammary epithelial cell binding sites. Increase in circulating glucocorticoids at parturition is an essential initiating lactogenesis (Collier et al., 1975). Receptivity to reserpine and dexamethasone treatment following the initial estrogen and progesterone protocol can further be increased by administering prostaglandin F2α which removes the progesterone source (Corpus luteum). Blood prolactin levels in cattle surge several hours prior to parturition, (Ingalls, 1973; Tucker, 2000) and this is necessary for full lactogenesis (Fulkerson, 1979). Somatotropin administration at the start of milking also improve the milk yield (28.3 kg/d) compared with controls (24.1 kg/d) receiving only the estrogen-progesterone injections (Kensinger et al., 1998).The milk yield is increased as bST regulates the use and absorption of nutrients as they directly affects the receptors for endogenous bST located in hepatocytes and fat tissue. The activation of these receptors limits the systemic use of nutrients, promoting their assimilation to mammary gland (Manalu et al., 1991).Other effects of bST are supported by insulin-like growth factors (IGF-I and IGF-II)which increase the glucose assimilation creating an increase in the milk synthesis (Rivera et al., 2010). Treatment with bST, increases glucose production and decreases the oxidation process at the same, then hepatic glucose production increases and its assimilation is reduced (Bauman et al., 1988; Bitman et al., 1984).
Prerequisites for Artificial Induction
It is a simple and inexpensive method with rapid accomplishing protocols showing high success rates with greater quantity and longevity of milk production. It is acceptable for human consumption as there are no side effects on human health been reported.
Animal should have good genetic merit for milk production, healthy and with good body condition. Repeat breeder or anestrus cow with clinically normal teats and udder is preferred. It can also be used in dry and non-pregnant animals. The treatment is more effective in well fed bovines with an optimum level of protein in diet (Ludri et al., 1996)
Hormones/Drugs used for Lactation Induction
Hormones play an important role in the development and function of the mammary gland. Several drug combinations are used for induction of lactation. Lobule-alveolar development of the mammary gland is stimulated by combination of estrogen and progesterone (Tucker, 2000). Addition of other hormones (prolactin and glucocorticoids) which work synergistically along with estrogen and progesterone for the onset of galactogenesis, can further enhance milk yield from induced lactation (Tucker, 2000; Akers, 2003; Mohan et al., 2009)
|Induction Protocol Used||Results||Name of Worker|
|Day 1 to 7: 17β-estradiol (.1 mg/kg BW/day), and progesterone (.25 mg / kg BW / day)||
|Smith and Schanbacher (1973)|
|Day 1 to 7: 17β-estradiol (.1 mg/kg BW/day), and progesterone (.25 mg/kg BW/day
Day 18,19,20: (20 mg/cow/day) to 6 heifers and 10 cows
|69% success rate (success > 9 kg milk / d at peak yield)||Collier et al., (1975)|
||Dabas and Sud, 1989|
||Deshmukh et al., 1993|
|Day 1-7: Estrogen and progesterone (1:1)||Lactation induced successfully in Tharparker cows heifer||Singh et al., 1994|
||92% success rate for
||Jewell Tracey, 2002|
||Mellado et al., 2006|
0.1mg/kg) and Dexamethasone
0.2 (20 mg/animal)
||Mohan et al., 2009|
||Freitas et al., 2010|
||Ramgattie et al., 2014|
Day 1-7 (0.1 mg of 17β—estradiol and 0.25 mg of progesterone dispensed per kg body weight of the animal
Day 1-7 (0.1 mg of 17β—estradiol and 0.125 mg of progesterone dispensed per kg body weight of the animal
||Hooda et al., 1996|
||Singh et al., 2002|
For good results, a thorough and frequent massage of udder is essential. In additional, one should start frequent milking as soon as secretion commences. Massage of udder and frequent milking will stimulate the hypophysis (pituitary gland) to secrete the hormones which promote mammary gland development, synthesis of milk and milk secretion (Heidrich and Renk, 1967). Owing to secretion of hormones in the milk, the milk of treated animal should not be put for human consumption for about 30 days from the start of the hormonal therapy. Treated animals require separate special housing as they may show signs of heat. Cows and buffaloes with artificially induced lactation generally produce 60 to 70% of normal milk yield that they had yielded in the previous lactation after calving.
The daily and peak milk yields of induced animals were similar to or greater than the average daily or peak milk yields reported for cattle in several tropical countries (Ageeb, and Hillers 1999; Tambi 1991). In some previous lactation-induction studies, peak milk yields were reached 7 to 8 weeks on onset of lactation (Smith and Schanbacher 1973 and Tervit 1980). The daily mean (11 kg) and peak (15 kg) yields for the induced animals in this study was very favorable compared with the daily average of 10 kg for untreated cattle while the time to attain peak milk production for un-stimulated cows was 8.7 ± 1.8 weeks and 12.7 ± 1.8 weeks for the stimulated animal (Ramgattie et al., 2014). Delayed peak yield in induced cows may be due to the less secretary tissue present at the beginning of lactation as compared with non-induced cows, as mammary development occurs over 20d period in the former and during the last month of gestation (Knight and Wilde, 1993). Induced cows are also less sensitive to cell proliferation (Finucane et al., 2008) and have a longer postpartum period of secretory tissue proliferation. Greater degree of uncoupling and slower recoupling of the somatotropic axis can also delay mammary development, and in turn would prolong maximum parenchyma volume, which is necessary for peak milk yield (Lucy et al., 2009)
It more profitable to induce lactation in non-breeder cows compared to purchasing replacement heifers as for induced cows net present value (NPV) was $520 US greater than that for replacement heifers (Magliaro et al., 1999; Kensinger, 2000). However, no economic benefit in using artificial induction was reported by Macrina et al., 2011. Net present value for an induced cow (1966) was significantly greater than that for a first-lactation cow (1946) (Magliaro et al., 2004). Obtaining a calf from an infertile animal is an additional profit.
Net Present Value (NPV) Values for Induced and Culled Animals (Ramgattie et al., 2014)
|Lactation Induced Cow||7397.70|
|Lactation Induced Heifer||5483.14|
|Replacement Cow ( Pregnant)||6302.24|
|Replacement Cow (Not Pregnant)||3430.40|
Milk Yield and Quality
When induced heifers (responders) were compared with natural lactation the differences in milk compositions (fat, protein and lactose) were slight and non-significant (Ball et al., 2000). There was no effect of the artificial inductions of lactation protocols on milk composition and somatic cell count (SCC) (P>0.05) (Freitas et al., 2010). Milk production of induced cows has been variable, ranging from 63 to 106% from the best previous lactation (Magliaro et al., 2004). The milk yield was significantly (P<0.05) greater in pre-synchronized heifers with PGF2α (.25 mg) I/m as compared to non-synchornized heifers (Mohan et al., 2009). Uniform development of follicles following luteolysis coupled with metoclopramide therapy may be the reason for increased yield in pre-synchronized animals (Tracy 2002, Shridhar and Narayana 2006).
Photoperiod is one of the most important environmental factors affecting milk yield (Dahl et al., 2000). As for lactogenesis, increased secretion of prolactin is an important factor which is further associated with increased temperatures and longer photoperiod (Akers et al., 1981). Complete treatments during warmer months, the success of the induction scheme in prepubertal heifers is increased (Kensinger et al., 1979)
Smith and Schanbacher, (1973) have reported that following induced lactation animals exhibit intense estrus activity. Hormonal induction has no apparent effect on reproduction, natural lactating and induced heifers averaged 1. 2 inseminations each (Ball et al., 2000). Time taken to exhibit estrus after hormonal treatment (87-231 days) was longer in buffaloes as compared to cattle (91-152 days) (Chakravarty et al., 1991). 30-90% pregnancy rates are reported after artificial induction of lactation (William et al., 1995, Narendran and Hacker, 1974; Peel et al., 1981). 41.4% cows having reproductive problems have been reported pregnant after artificial induction of lactation (Freitas et al., 2010). The difference in conception rate may be due to variation in feeding regimes, detection of estrus and time of insemination.
Progesterone Vaginal Inserts
Replacing progesterone injections by intravaginal progesterone devices during the first seven days of the protocol can help in reducing the stress to the animals. Steroids delivery using intravaginal devices has been attempted by several authors (Davis et al., 1983; Lucy et al., 2001; Lima et al., 2009; Rivera et al., 2011). P4 concentrations in plasma increased in both groups of cows under induced lactation (P4-INS: induction lactation protocol by administration of P4 using two vaginal progesterone inserts and P4-INJ: induction lactation protocol by administration of progesterone using only injections), and it indicates that no matter the source of progesterone administration, P4 concentrations with the induced lactationis similar to that observed in late pregnancy dairy cows (Rivera et al., 2015). Progesterone supplementation through vaginal devices has been resulted in a linear increase of this hormone (Lima et al., 2009).
Induced lactation can be an alternative for high producing cow with low fertility. Artificial induction of lactation by using hormones can be used as an alternative to normal lactation, further it helps in reducing culling losses in herd and increasing profits. It should only be practiced when the animal is rendered infertile and all efforts to correct reproductive disorders/ abnormality fail. During the course of lactation animals come in to estrus and some of them become pregnant which improves the breeding efficiency besides bringing animal in to milk. The milk produced by this technique is similar in composition to milk produced after normal calving and in most cases fit for human consumption after a week’s time. Economic profit can also be generated from heifers by hormonal lactation induction as compared to rearing of replacement cow.