One of the interesting biological engineerings that have been introduced to the farm animal production is the man-made somatotrophin ( ST ) or growing endocrine ( GH ) . Exogenous ST has been used to increase production in farm animate beings. In dairy animate beings, ST has been shown to increase lactation public presentation ( Bauman and Vernon, 1993 ) . This consequence has been investigated extensively in dairy cowss after available of recombinant bovine ST ( rbST ) . rbST has been shown to increase milk output with minor alteration in milk composing. In add-on, rbST has been demonstrated that it could increase milk output efficaciously in dairy caprine animal ( Disenhaus et al. , 1995, Polratana et al. , 2004 ; Sallam et al. , 2005 ) . Although there are multiple factors that can find the magnitude of rbST consequence on milk output which include the nutritionary position and provender quality. Cows injected with rbST adjust their nutritionary position partially by altering voluntary nutrient consumption related to feed quality and their milk production. For the dairy animate beings fed in Thailand, lactation public presentation is attenuated partially by the insufficiency of nutritionary position. However, it has been shown that rbST could increase milk output in both dairy cattles and caprine animal ( Polratana et al. , 2004 ; Chaiyabutr et al. , 2005 ) . Interestingly, these experiments revealed that provender consumption was besides increased after rbST intervention ( Polratana et al. , 2004 ; Boonsanit et al. , 2010 ) . The consequence of rbST on milk production, feed consumption and alimentary digestibleness in breastfeeding caprine animal is an interesting position of this proposal.
Food consumption is a complex behaviour that provides energy and necessary foods to the organic structure. To guarantee that organic structure receives equal energy and alimentary particularly during lactation, this behaviour is controlled or influenced by multiple variety meats. The internal control of feed consumption includes the interplay between peripheral detection and signaling systems ( centripetal organ, GI piece of land and adipose tissue etc. ) and cardinal integrating ( the encephalon ) . Leptin ( from adipose tissue ) is an internal factor that produces anorexic effects on provender consumption. The repletion effects of leptin are besides observed in ruminants. Administration of human leptin in Ewe for 3 yearss decreased the voluntary dry affair consumption to about a 3rd of the preinfusion consumption ( Henry et al. 1999 ) . Furthermore, Chanchai et Al. ( 2010a ) found that disposal of rbST in dairy cattles decreased leptin concentration in all phases of lactation.
Aims of survey
Cardinal words ( Thai ) :
Cardinal words ( English )
Endocrinology facets on mammary secretory organ development and milk production
The physiology of lactation consists of mammary secretory organ development ( mammogenesis ) , the start of milk production ( lactogenesis ) and care of milk production ( galactopoiesis ) . The mammary secretory organ development is stimulated by oestrogen and Lipo-Lutin, somtotropin and IGF-I, lactogenic hormone and inhibited by mammary derived growing inhibitor. The lactogenesis is stimulated by lactogenic hormone, oestrogen, glucocrticoids, insulin and inhibited by Lipo-Lutin. The galactopoiesis is influenced by some endocrines such as somatotrophin, thyroid endocrines, and lactogenic hormone for stimulation and glucocorticoids, oestrogen for suppression.
Hormonal effects on mammary secretory organ development
Oestrogen stimulates mammary canal growing, and oestrogen and Lipo-Lutin act synergistically to excite lobule-alveolar development. Progesterone is elevated throughout gestation and oestrogen is peculiarly increased during the late gestation in the gnawer ( Mizoguchi et al. , 1997 ) . Therefore, chiefly canal and lobular growings occur during the first half of gestation, with lobule-alveolar growing happening during the 2nd half of gestation. In add-on, oestrogen besides stimulates the secernment of IGF-I endocrine and thereby increases the epithelial cells. Prolactine and growing endocrine ( ST ) are needed for the steroid endocrines to be effectual and degrees of lactogenic hormone, ST and insulin lessening during gestation. Thus, no mammogenic activity happens in the absence of growing endocrine and lactogenic hormone ( Tucker, 2000 ) .
Mammary-derived growing inhibitor ( MDGI ) is produced by mammary epithelial cells. It acts in an autocrine mode to suppress cell growing and particularly to bring on distinction in mammary epithelial tissue. MDGI degrees addition in mammary secretory organ two hebdomads prior to birth and are high in breastfeeding cattles.
ST stimulates the growing of canals during mammary secretory organ development near pubescence and lobule-alveolar growing during gestation. Injection of ST increases growing of the parenchyma and entire mammary cell Numberss in cowss ( Radcliff, 1997 ) . This occurs via action of IGF-I. The negative effects of high feeding degree on mammary growing near pubescence may be due to increased local production of IGFBP-3, which binds IGF-I to suppress it.
Hormonal effects on lactogenesis
There is considerable species variableness in the effects of endocrines on lactogenesis. Oestrogen stimulates the release of lactogenic hormone from the anterior pituitary and increases the figure of prolactin receptors in mammary cells. There is a rush of prolactin several hours before birth. But lactogenic hormone is non of import during ruminant lactation. In dairy caprine animal, suppression of lactogenic hormone secernment has merely little influences on milk output and disposal with lactogenic hormones did non increase milk output ( Jacquemet and Prigge, 1991 ) .
Glucocorticoids bind to receptors in mammary tissue to increase the development of the unsmooth endoplasmic Reticulum and other ultrastructural alterations to increase the secernment of I±-lactalbumin and I?-casein. Adhering to the corticoid adhering globulin ( CBG ) reduces the activity of glucocorticoids in serum. During the periparturient period, degrees of the CBG lessening and free glucocorticoid degrees addition. Glucocorticoids besides suppress the immune system, which may lend to the increased incidence of mastitis during early lactation ( Kehrli, 1991 ) .
Insulin is of import in exciting glucose consumption and the look of milk protein cistrons required for lactogenesis. Insulin concentration was low during lactation in most species ( Neville and Picciano, 1997 ) . It would be of import for shunting the foods off from organic structure terminals and had more available foods for milk synthesis.
Progesterone has been suggested to work by increasing the mammary threshold to prolactin, by changing the secernment of lactogenic hormone from the hypophysis or moving as a glucocorticoid receptor adversary. The degree of Lipo-Lutin is high during gestation and serves to suppress lactogenesis until merely before birth and its concentration depends each species, around 6-130 ng/ml in the rat, 35 ng/ml in sheep ( Mellor et al. , 1987 ) . The degree decreases about 2 yearss before birth to take the suppression of milk synthesis.
Hormonal effects on galactopoiesis
Thyroid endocrines are required for maximum milk production. During lactation there is reduced transition of tetraiodothyronine ( T4 ) to the active endocrine liothyronine ( T3 ) in liver and kidney, but increased transition to T3 in the mammary secretory organ. This may be enhanced the precedence of the mammary secretory organ for metabolites compared to other organic structure tissues. Administration of thyroid endocrine causes a impermanent addition in milk production for several hebdomads, but milk output was unchanged when thyroid hormones disposal to animal for more than seven hebdomads ( Blaxter et al. , 1949 ) .
High degrees of exogenic glucocorticoids and oestrogen lessening milk production. Prolactin is required for the care of milk production in rats, with lessenings in milk output of 50 % or more after bromocriptine disposal and much less effectual in ruminant. Furthermore, lactogenic hormone and IGF-I degrees addition with effects of long twenty-four hours photoperiod. These contribute for increasing milk output in cowss ( Dahl et al. , 2000 ) . These may be explained that lactogenic hormone has negative effects on the IGFBP-5 protein and IGFBP-5 is a factor which inhibits cell endurance by bring oning programmed cell death ( Flint et al. , 2001 ) .
Overview of somatotrophin
ST is a protein endocrine synthesized from somatotroph cell of anterior pituitary secretory organ. The construction of ST ( about 191 aminic acids ) is comparative species specific in which bovine ST and porcine ST portion up to 90 % similar amino acid sequence ( Table 1 ) , while human ST portions merely 35 % similarity ( Bauman and Vernon, 1993 ; Etherton and Bauman, 1998 ) .
Control of the somatotrophin release and mechanism of action
The secernment of ST, basal and episodic forms, from anterior pituitary secretory organ is regulated by the interplay of the two chief hypothalamic peptides ; growing endocrine let go ofing factor ( GHRF ) and somatostatin ( SS ) ( Fig.1 ) . GHRF is a 44 amino acid peptide synthesized by cells in the arcurate karyon of the hypothalamus ( Fig. 1 ) . It is secreted from neuron- secrectory nervus terminuss and transported to the anterior pituitary secretory organ by the hypophyseal portal system. GHRHF binds to a G-linked protein receptor in somatropes, exciting in camp and triping GH release via the written text factor. Somatostatin is produced in the periventricular karyon of the hypothalamus. It is 14 amino acids that is found in many tissues outside the hypothalamus. This includes the CNS and delta cells of endocrinal pancreas and intestine. SS inhibits the release of GH from the anterior hypophysis by cut downing camp concentrations within the somatotropes. SS besides inhibits several other endocrines and metabolites such as PTH, calcitonin, stomachic HCl, acetylcholine ( Hossner et al. , 2005 ) .
Table 1 Amino-acid sequence of somatotrophins from assorted species.
Porcine ( Pacific Time )
Bovine ( bST )
Sheep ( oST )
Human ( hST )
Porcine ( Pacific Time )
Bovine ( bST )
Sheep ( oST )
Human ( hST )
Porcine ( Pacific Time )
Bovine ( bST )
Sheep ( oST )
Human ( hST )
Porcine ( Pacific Time )
Bovine ( bST )
Sheep ( oST )
Human ( hST )
Although the consequence of GHRF and somatostatin is stimulation and suppression of ST synthesis and secernment, nevertheless, the mechanism of pulsatile secernment of ST is still ill-defined ( Mueller et al. , 1999 ; McMahon et al. , 2001 ) . It is good known that ST produces wide scope of physiological maps including: postpartum growing ( bone & A ; musculus ) , foods metamorphosis, transition of cell rhythm, control of immune system, bosom and encephalon map, mammary secretory organ and lactation. These maps of ST can be divided into somatogenetic and metabolic effects. The first effects are the stimulation of cell proliferation while the latter effects change the whole organic structure metamorphosis by partitioning of all foods to back up the specific action of ST. ( Bauman and Vernon, 1993 ; Etherton and Bauman, 1998 ) . With the broad scope of ST map, it suggests that the mechanism of ST action should be tightly regulated. Somatotropin mediates its map straight via growing endocrine receptors ( GHR ) or indirectly via insulin like growing factor ( IGF ) system ( Bauman and Vernon, 1993 ; Brooks and Waters, 2010 ) . The direct consequence of ST is transmembrane receptor belong to category I cytokine receptor super-family. The look of GH receptor has been demonstrated in many variety meats or tissues, eg. liver, adipose tissue, bosom, encephalon, kidney etc. This broad distribution of GHR indicates the pleotropic consequence of ST ( Kopchick et al. , 2002 ) . One of the most of import go-betweens from the ST-IGF axis is IGF-I. IGF-1 belongs to a household of insulin-like growing factors ( IGFs ) that portions near structural homology to the precursor signifier of insulin ( pro-insulin ) . Although go arounding IGF-I which acts as endocrinal manner appear to come chiefly from liver, the local production of IGF-I as paracrine or autocrine has been known every bit good ( LeRoith et al. , 2001 ) .
Recombinant bovine growing endocrine ( rbGH ) or rbST refers to bovine growing endocrine that is manufactured in a research lab utilizing familial engineering. This man-made endocrine is approved by United State of American Food and Drug Administration ( US FDA online ) and marketed to dairy husbandman to increase milk production.
United states secret service
( – ) ( – )
GHRF ( + )
( – ) ( – )
Carbohydrate, lipid, protein and mineral metamorphosis
Figure 1. Regulation of growing endocrine release
To do rbST, the plasmid of a bacteria is cut by enzymes, and so combined with a cow ‘s Deoxyribonucleic acid. It is reintroduced to the bacteria, placed in a agitation armored combat vehicle and allowed to multiply, so separated and purified before bringing to the husbandman ( Roush, 1991 ) . This modern engineering permitted the development of rbST, which provided an limitless beginning of ST for research and for commercial application. Recombinantly derived bST merchandises differ somewhat from bST derived pituitary secretory organ which the fabrication procedure can add a few excess amino acids to replace for the terminal alanine residue ( Table 2 ) ( Hammond et al. , 1990 ) . The figure of excess amino acids differs from 0 to 9, depending on the peculiar fabrication procedure.
Table 2.The merchandises of rbST on the market
Amino acerb replace for alanine ( 191 )
Treatment with rbST has been shown to increase milk output with minor alteration in milk composing. Although the exact mechanism that rbST stimulates mammary secretory organ activity is still ill-defined, several groundss supported that the pharmacological consequence of rbST on lactation seemingly mediate chief via IGF dependent tract. First, IGF receptor was successfully demonstrated from mammary tissue, while GHR look was really scarce at mRNA degree and could non be detected at protein degree. Second, the closed extract of ST to the mammary arteria failed to bring forth the consequence on milk output, whereas the same extract by IGF-I significantly increased milk production. Addendum with rbST dramatically increased circulatory IGF-I ( Etherton and Bauman, 1998 ) . In Thailand, the consequence of rbST on milk production has been extensively investigated in crossbred dairy cowss ( Chaiyabutr et al. , 2009 ; Boonsanit et al. , 2010 ; Chanchai et al. , 2010b ; Chanchai et al. , 2010c ) . In add-on, milk output from dairy caprine animal besides increased after rbST addendum ( Polratana et al. , 2004 ) . It was concluded from above experiments that rbST better the lactation public presentation in crossbred dairy cowss and dairy caprine animal in hot and humid environment of Thailand.
Recombinant somatotrophin and alimentary metamorphosis
Consequence of recombinant bovine somatotrophin on saccharide metamorphosis ( glucose )
Consequence of recombinant bovine somatotrophin on N metamorphosis
Consequence of recombinant bovine somatotrophin on fat metamorphosis
Consequence of recombinant bovine somatotrophin on provender consumption and alimentary digestibleness
Supplemented with rbST has been shown to impact provender consumption in dairy animate being ( Polratana et al. , 2004 ; Boonsanit et al. , 2010 ; Chanchai et al. , 2010a ) . Some experiments have been demonstrated no consequence of rbST on provender consumption ( Disenhaus et al. , 1995 ; Chadio et al. , 2000 ; Chaiyabutr et al. , 2005 ; Chaiyabutr et al. , 2007 ; Sallam et al. , 2005 ) . This disagreement information suggested that these consequences likely came from the difference in experimental status and reflected that this behaviour was controlled by multiple factors. In crossbred dairy cowss fed in Thailand, there was no important consequence of rbST on provender consumption ( Chaiyabutr et al. , 2007 ) . However, the latter probe from the same group reported that an addition provender intake in the crossbred dairy cowss treated with rbST compared with control at all phase of lactation ( Boonsanit et al. , 2010 ; Chanchai et Al, . 2010a ) . In dairy caprine animal and Ewe, dry affair consumption did non differ significantly between control and rbST intervention ( Disenhaus et al. , 1995 ; Chadio et al. , 2000 ; Sallam et al. , 2005 ) . However, Polratana et Al ( 2004 ) found that dry affair consumption of dressed ore in rbST injected caprine animal was significantly higher than control group during late lactation. As reference above, the addition feed consumption may depend on the addition in milk production, energy position, environmental status and the foods of diet ( peculiarly energy ) . Overall, dairy animate beings supplemented with rbST appear to set their voluntary provender consumption in relation to the extra food required for increased milk output.
In add-on, rbST disposal in dairy cattles had no consequence on alimentary digestibleness when comparison to command in full lactation rhythm and besides no important difference between cooled cow and non-cooled cow ( Chanchai et al. , 2010b ) in understanding with other surveies that carried out in breastfeeding American bisons ( Khattab et al. , 2008 ) . Most of old surveies have been done foods digestibleness on dairy cowss or American bisons when administrated with rbST. Therefore, it remains to look into the consequence of bST on alimentary diegestibility of dairy caprine animal during early period in this proposal.
Role of leptin on provender consumption and energy balance
Leptin is protein hormone secreted from the adipose tissue into the circulation. This endocrine meets the standards of adiposeness signals which play an of import function for the control of provender consumption and organic structure weight. First, the concentration of plasma leptin has positive relationship with organic structure fat mass. Second, exogenic leptin decreases nutrient consumption and organic structure weight, and increases energy outgo. Third, leptin signals to the encephalon after release by the adipocyte and gives information about the position of the organic structure energy shops. Leptin receptors are located in several hypothalamic karyon. Leptin non merely influenced on provender consumption and organic structure weight, but besides affected on other physiological maps such as: reproduction, the immune and inflammatory response, angiogenesis by assorted biological mechanisms ( Schwartz et al. , 2000 ; Wood and Seeley, 2000 ; Kershaw and Flier, 2004 ) . In add-on to the extended probe of leptin consequence was found in rat and mouse, the consequence of leptin on provender consumption has besides been studied in dairy animate being ( Henry et al. , 1999 ; Blache et al. , 2000 ; Morrison et al. , 2001 ; Leury et al. , 2003 ; Liefers et al. , 2003 ; Whitley et al. , 2005 ) . Voluntary provender consumption decreased about one tierce after 3 yearss leptin disposal in Ewe ( Henry et al. , 1999 ) . However, the anorexic consequence of leptin was lost when turning and big sheep were ill-fed ( Morrison et al. , 2001 ) . In crossbred dairy cowss, plasma leptin was lower in rbST intervention compared with control. The lower of plasma leptin in rbST treated cattles was associated with an addition of feed consumption ( Chanchai et al. , 2010a ) . These consequences suggested that the consequence of rbST on feed consumption appeared to be mediated partially by influence of plasma leptin.
From above information, it is of import to transport out this experiment in dairy caprine animal during early wet period and to understand the relationship between plasma leptin and rbST induced feed consumption in consistent with addition of milk production.
Effectss of recombinant bovine somatotrophin on lactation public presentation
Milk yield bit by bit increased in both dairy cowss and caprine animal after treated with rbST. rbST systematically consequences in a greater extremum milk output and an increased doggedness in output over the lactation rhythm in both temperate and tropical zone ( Bauman and Vernon, 1993 ; Etherton and Bauman, 1998 ) . In dairy cowss, an increased milk output after rbST disposal is found of all paras. However, the magnitude of the addition in milk production differs to be due to the phase of lactation. In general, little response is found when breastfeeding animate beings are injected rbST in early lactation prior to top out output. In add-on, rbST additions milk yield by 10 % when administered in early to mid-lactation, and by 40 % in late lactation ( Bauman and Vernon, 1993 ) . In Thailand, rbST increased lactation public presentation by 22 % during early lactation ( Chaiyabutr et al. , 2009 ) . Chanchai et Al. ( 2010a ) and Boonsanit et Al. ( 2010 ) who studied the influence of chilling system in crossbred dairy cowss treated with rbST ( 500 milligram rbST/dairy cattle/two hebdomads ) during hot & A ; humid conditions reported that the milk output of cooled cattles ( ambient temperature from 29 – 32 0C and comparative humidness from 70 – 78 % ) treated with rbST was somewhat higher than non-cooled cattles ( ambient temperature about 34 0C and comparative humidness from 50 – 64 % ) .
Similarly, milk output rose significantly over the full experimental clip when breastfeeding caprine animals supplemented with rbST ( Disenhaus et al. , 1995 ; Gallo et al. , 1997 ; Chadio et al. , 2000 ; Sallam et al. , 2005 ) . In Thailand, addendum with 250 milligrams rbST every 2 hebdomads in dairy caprine animal doubled milk output during late lactation ( Polratana et al. , 2004 ) . It remains to be investigated whether milk output during early period of lactation in dairy caprine animal still response at this dosage of rbST. The relationship of milk production responses to dose and phase of lactation in breastfeeding animate beings are shown in Table 3.
Table 3 The relationship of milk production responses to dose and phase of lactation.
Milk output ( kg/d )
Dairy animate being