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Heat Stress on Bovine ReproductionJEROME A, S.K. SRIVASTAVA, R.K. SHARMA
India possesses 199.1 million cattle and 105.3 millionbuffaloes and ranks first in milk production in global worldmainly contributed by buffaloes Buffaloes is an integral component of Indian livestocksector. The contribution of buffalo to country’s total milkproduction is 56% (110 MT) DAHD, 2011 Milk productivity is much lower due to variousreproductive (anestrous, repeat breeding and post parturientdisorders) and non-reproductive disorders (diseases). The impact of infertility in terms of economic losses in Indianlivestock is not available Das et al. 2004
Acquired /environment or congenital/hereditary; Physiological, anatomical, Infectious Kodagali, 1968 Reproductive problems in buffaloes can be classified : Major (anestrum, repeat breeding and endometritis) Minor (cystic ovarian degeneration, parturient disorders). Infertility in buffaloes : Functional: Anestrus; repeat breeding, Infectious diseases of reproductive system & post-parturientdisorders.
onomic of the reproductive lossesbout 18-40% of cattle and buffaloes were culled mainly due to infertilitywhich incriminates direct losses to the farmer as well as to the geneticresource.oor reproductive performance leads to economic losses due to reducedproduction and additional cost on management.he outcome of impaired normal reproductive function: ub-fertility, infertility and sterility result in economic losses due to extendeddry period, late maturity, decreased calving percentage & decreased lifetimeproductivity. Khan et al. 2009
Anestrum Absence of periodic manifestation of estrus, with the absence of palpable follicular or luteal structures (smooth ovaries) or absence of normal physiological signs of estrus (Subestrus) Ovarian inactivity is more frequent (30%) in buffaloes on low level of feeding than in those given high level feeding. Ovarian inactivity constituted 28% of all the functional causes of infertility in postpartum buffaloes and 67% of all cases of inactive ovaries in these Buffaloes Rao and Sreemannarayana, 1982 Incidence of anestrum is buffalo 20-67% Purbey and Agarwal, 1982; Luktuke and Sharma, 1978 Season: more in summer (41–46%) than in other seasons (7–33%) Rao and Sreemannarayana, 1982
Incidence of anoestrus in buffaloes in various states State Incidence (%) Haryana 56-67 Punjab 19.84 West Bengal 50.84 UP 69.40 Gujarat 9.18 Tamilnadu 9.09 Madhya Pradesh 60.83 Andhra Pradesh 30.67 Punjab 67.11 Bihar 44.60 Karnataka 51.00 Andhra Pradesh 56.36 Khan et al. 2009
Summer/Heat stressMagnitude of forces external to the bodily system which tendto displace that system from its resting or ground state. Lee, 1965Estimate the stress to which the animal is exposed, the“temperature humidity index” (THI)- most used stress index for usein animal husbandry Thom, 1959Used to evaluate the impact of climatic conditions thatcontribute to heat stress on the production of livestock all overthe world Igono and Johnson 1990; West et al. 2003An optimal ambient temperature zone or the so called“thermoneutral zone ‟ within which no additional energy abovemaintenance is expended to heat or cool the body Yousef, 1985
The critical temperatures vary and depend upon age, level ofproduction, breed type and the degree of acclimatization Fuquay, 1981; Young, 1981; Shearer and Beede 1990Above the UCT, the thermoregulatory process is being activated inresponse to the signals of the hypothalamic thermoregulatory center-blood flow from internal organs to peripheral tissues increases,sweating and panting increase, and feed intake and nutrientabsorption decrease Shearer and Beede, 1990 Effect of heat stress on systems:Heat stress - dynamic characteristics of digestion, neuroendocrinefactors influencing digestion, Reduced feed intake -> reduced milkproduction.Efficiency of feed conversion and dry matter intake remaineddecreased during heat stress is also reduced Fuquay 1981; Wolfenson et al. 2000
During heat stress, water consumption increases and losses of potassium in sweatd Lipsett et al. 1961; Elnouty et al. 1980 Secretion of hormones associated with metabolism (thyroxine, somatotropin, and glucocorticoids) and water balance (antidiuretic hormone and aldosterone) are significantly reduced Anderson and Bates, 1984 Adrenal corticoids, mainly cortisol, elicit physiological adjustments that enable animals to tolerate stressful conditions. However, the effects of high temperatures on cortisol levels are inconsistentEffect of heat stress on al. 2004 Correa-Calderon et reproductive systems: redistribution of the blood flow from the body core to the periphery to increase sensible heat loss Hansen, 2009 Reduced perfusion of the placental vascular bed and retarded fetal growth Collier et al. 1982;Alexander et al . 1987
Heat stress at the cellular level Exposure of the oocyte to heat stress at the germinal vesicle stage or during early stages of maturation - deleterious effects on the internal of the oocyte for fertilization and further embryonic development is reduced. Payton et al. 2004; Roth and Hansen, 2004 Major damages are defects of the cytoskeleton Roth and Hansen, 2005 Cellular membranes can also be severely affected by exposure to elevated temperature, changes in membrane morphology and alteration in the ratio of protein to lipids and an increased fluidity of the membranes Kruuv et al. 1983; Vigh et al. 2007 During heat stress, heat shock proteins restore protein homeostasis to the pre-stress balance by refolding, repairing damaged proteins and stabilizing ribosomal RNA. Richter et al. 2010
development after fertilization or electrical activation. Hansen, 2009In bovine expression of LH receptor (LHr) mRNA may be associatedwith follicle selection. The expression of LHr mRNA higher in the dominantfollicleStress causes follicle deviation with low expression of LH receptorgene Beg et al. 2001; Nogueira et al.2010Depending on the duration and severity of heat stress, thesemechanismsultimately lead to an arrest of the cell cycle and a stagnation ofgrowth & proliferation and which result in the death of the cell byapoptotic enzymes Lindquist, 1986Key enzymes such as aromatase (rate limiting enzyme) - affected byestrogen systemically and locally on granulose cell functions inbovines Matsuda et al.2012
Heat stress on ovarian follicular dynamicsFollicular dynamics cattle (Ginther et al, 1989 ),Buffaloes (Taneja et al. 1996)Heat stress degreases the no. of small follicles – infertile oocyte Wolfenson et al. 1995Heat stress animals tend to have smaller size dominant folliclecompared other animalHeat stress affect the follicular dominance by decreaseproduction of estradiol beta and ovulation of in competentoocyte Wilson et al. 1998Heat stress causes co-dominance of the follicles and affect thedecrease oocyte competence. Sartori et al. 2004
Heat stress on buffaloesBuffaloes are seasonal breeders and susceptible to thermal stress Pandey and Roy,1966Effect of heat stress on systems:Heat stress increases water intake with increases temperature (30-40%) Roy et al. 1964Decrease urine output, increase specific gravity during summer Pandy and Roy,1969DM digestibility protein/energy ratio, BUN and Growth rate werealso found to decrease in heat stress conditions Moss, 1993; Habeeb et al. 2007Plasma protein, glucose, cholesterol and toal body water decreases Verma et al. 2000
Buffaloes exhibit alterations in hormonal secretion due to heatstress Madan 1988; Razdan 1988; Singh et al.2000Low T3,T4 and high PRL levels- negative feedback mechanism,exerts a suppressive effect onthe secretion of gonadotrophins andovarian steroids Razdan et al. 1981Cortisol increases, but insulin, aldosterone decreases in hot summerseason Zhengkang et al., 1994;Habeeb et al.,2007 Prolactin, Follicle stimulating hormone, LH, progesterone, estradiol-17b are directly affected by heta stress. Sheth et al. 1978; Razdan et al. 1981Thermal stress causes reduced luteinizing hormone (LH)frequency, poor follicle maturation and decreased oestradiolproduction in anoestrus buffaloes leading to ovarian inactivity Aboul-Ela and Barkawi 1988; Palta et al. 1997
Follicular characteristics & dynamicsPresence of quiescent ovaries in most of the buffaloes duringsummer months Nanda et al. 2003Slaughterhouse ovaries observed that anoestrus state of ovarieswas maximum (41.2%) between April and June Roy et al. 1972Non-cyclic buffaloes have lower follicle reserve than their cycliccounterpart Danell, 1987Summer anoestrus buffaloes:Showing the presence of CL - indicating a possibility of silent orunobserved oestrus,True anoestrus : dynamic follicular activity (smaller population offollicles without ovulation in the majority of the cases Rohilla et al. 2005
Therapeutics strategies for anestrum Management strategy: Reducing heat stress Improving estrus detection methods Feeding strategy Roughage feeding during night to buffaloes will reduce the heat stress in buffaloes Acharya, 1988 Feeding green fodders, ad - libitum water and min. mixture suppl. improve the efficiency of reproduction during summer Low fiber, high fermentable carbohydrate diets lower dietary heat increment compared with higher fiber diets. Sastry and Tripathi, 1988 Breeding Strategy Selection and breeding animals having heat stress tolerance with sweating competence, low tissue resistance, light coat structure and color. Das and Khan . 2010
Hormonal treatment Various hormonal treatment regimens are being used to overcome this problem, primarily aimed either at stimulating ovarian activity, inducing ⁄ synchronizing behavioural oestrus or controlling ovulation Barile 2005; De Rensis and Lopez-Gatius2007 PG based treatments An alternative approach suggested to do away with the acyclicity during summer season is fixed time artificial insemination using PGF2a or its analogues Sahasrabudhe and Pandit 1997; Chohan 1998 Oestrus induction rate achieved: high; conception rate, attributed to the difference in the interval between PGF2a administration and the commencement of oestrus and ovulation Baruselli 2001; Zicarelli 2003
GnRH based treatments:Treatment protocol to reduce the variation in ovulation time,consequently synchronization of ovulation within a short-period oftime.Induction of follicular wave is also done by using eCG in ovsynchprotocol. A double insemination is recommended to approach thetime of ovulation for achieving better conception rates Barile etal. 2001Without any desired success (because of their limited half-life and awider variation in response contingent upon the follicular size andstage at the time of treatment De Rensis et al. 2005; Ramounet al.2007Clomiphene citrate, melatonin implants, bromocriptine have alsobeen reported for the treatment of seasonally anoestrus buffaloes.Ghuman et al. 2008; Verma et al. 1992Use of antioxidants (selenium, vitamin E and Zinc–Methionine) toimprove fertility during summer seasonAbou-Zeinaet al. 2009
Progesterone based treatment:Estrogen (Allen and Doisy, 1923) & progesterone (Corner andAllen, 1929) - isolated and synthesized, research interests havefocused on the effects of these steroids on reproduction acrossspecies of mammals.Exogenous progesterone would inhibit ovulation in rabbitsMakepeace et al. 1937Exogenous progesterone would inhibit estrus in cattlehristian and Casida, 1948Progestational compounds(progestins): to synchronize estrus andovulation in cattle Odde, 1990; Patterson etal. 1989Progestational compounds: 6chloro-6-dehydro-17-acetoxyprogesterone (CAP), dihydroxyprogesteroneacetophenide(DHPA), 6-methyl-17 acetoxy-progesterone (MAP), melengestrolacetate (MGA), norethandrolone, & progesterone.Progestins have been administered orally, as injectables, viaimplants, & intravaginal devices.
Early investigation of oral progestins primarily focused oninhibiting ovulation in women.1960’s , animal scientists began to explore the use of oralprogestins to control estrus and ovulation in cattle.Zimbleman and Smith.1963The progestational properties of MGA maintained pregnancy inovariectomized dairy heifers by feeding MGA. Zimbleman and Smith.1963100% suppression of estrus and ovulation in heifers fed MGA for a16 d duration at a rate of 0.5 mg/head/day Zimbleman and Smith, 1966Feeding a progestin can be difficult, especially controlling theamount of feed intake if animal are not used to being fed from afeed bunk.Therefore, alternative ways of administering progestins were tried.
Syncro-Mate B (SMB; Rhone Merieux Inc., Athens, GA). Thebiological action of norgestomet at the cellular level was mediatedvia binding to progesterone receptorsMoffatt et al., 1993SMB treatment consisted of a norgestomet (6 mg) implant, placed inthe ear for a duration of 9 d, with an injection of norgestomet (3mg)and estradiol valerate (5mg) administered at the time of implantinsertion.Syncro-Mate B is no longer available; however, intravaginalprogesterone-releasing devices replaced the norgestomet ear implant.PRID: Earliest intravaginal devices was referred to as theprogesterone releasing intravaginal device. Silastic coil, which isimpregnated with progesterone (6.75%). Progesterone is diffusedfrom the device into vaginal fluid and absorbed throughthe vaginal mucosa.CIDR: Recently approved for use as an estrus synchronization tool, isa new Controlled internal drug-releasing device (EAZI-BREED CIDR;Pharmacia-Upjohn, Kalamazoo, MI).
CrestarCrestar contains 3 mg of norgestomet in commercial preparations.Norgestomet is approved by FDA for use in cattle for estrussynchronization Darling 1993Chemically, norgestomet (17a-acetoxy-l l P- methyl-1 9-norpreg-4-ene-20,dione) is a modified 19-norprogesterone.Norgestomet has two other modifications: the presence of amethylgroup at the 11 position and acetate at the 17 position. Acetatehas been added to provide longer half-life in situSinkula 1978 Norgestomet has also been successfully used for resynchronization incattle and for estrus suppression and synchroni-zation in sheepFavero et al. 1995, Machado 1994, Kesler and Favero 1989;1997Gilbert et al. (1974) demonstrated that norgestomet is 15 times morebiologically active than progesterone when orally administered torabbits and 216 times more biologically active than progesterone
Wishart (1972) norgestomet is 321 times more potent thanprogesteroneNorgestomets principal mode of action for estrus synchronization isby suppressing estrus and progesterone biological activity to maintainpregnancy in ovariectomized heifers Favero et al. 1990Norgestomet is as effective as progesterone substitute in biologicalsystem in cattle. Crestar: includes a 9-day implant containing 3 mg of norgestomet and an intramuscular injection that consists of 3 mg of norgestomet and 5 mg of estradiol valerate that is administered at the time of implant insertion (cyclic) Chien 1978, Kesler et al.1995