Anoestrus in Indigenous Cattle and Buffalo
Cattle and buffaloes become infertile when they are neither fertile nor completely sterile and are delayed or irregular for production of annual live calf. Although causes of infertility are many and may be complex, anestrous and repeat breeding have been identified as the main factors responsible for this malady. It was reported that 10 to 30 % of lactation yield may be affected by infertility and reproductive disorders and 3 to 6 % of the herd is culled every year in developed countries for these reasons. Although authentic information regarding the economic losses of infertility under Indian condition is not readily available, the extent of the problem is likely to be greater in tropical countries. As per the reports of ICAR (2002) 18 – 40 % cattle are culled every year in India due to infertility or sterility Anestrous, repeat breeding, cystic ovarian degeneration, uterine and tubal disorders have been observed as the most common gynaecological problems in cattle and buffaloes in India. Anestrus is one of the most commonly occurring reproductive problems in cattle and buffalo in India, affecting livestock productivity and economics to a great extent. The problem is more severe in sub urban and rural areas of the country. It is a functional disorder of the reproductive cycle which is characterized by absence of overt signs of estrus manifested either due to lack of expression of estrus or failure of its detection. Anestrus is observed in post pubertal heifers, during pregnancy, lactation and in early postpartum period in adult animals. In heifers, it poses a herd problem possibly due to low plane of nutrition, stress of seasonal transition or extremes of climatic conditions. Expression of overt signs of estrus is greatly affected by heat stress in buffaloes. Modern feeding and managemental practices also accentuate the problem in commercial dairy farms. Incidence of anestrus though varies in the different managemental system but it is more in buffalo than the cattle, and especially during summer .
Incidence
A large variation on incidence of anestrus has been reported in literatures depending upon species, breed, parity, season, level of nutrition, managemental conditions, geographic environment The period of postpartum anoestrus is usually longer in buffalo than the cattle under similar management conditions (Jainudeen and Hafez, 1993). In comparison to cows, buffaloes have lesser number of preantral and antral follicles, smaller sized pre– ovulatory follicle and greater tendency of follicular atresia which might be responsible for high incidence of anestrus in buffaloes.
Classification of Anestrus
Based on ovarian activity, anestrus cow has broadly been classified into ovulatory, anovulatory and inactive. Wiltbank et al. (2002) classified the anovulatory anestrus into three classes i.e. anovulation with follicular growth up to emergence; anovulation with follicular growth up to deviation but not ovulatory one; anovulation with follicular growth up to ovulatory size. Estrus based on the above information’s and for the ease, anestrus has been classified accordingly for better understanding (Figure 1)
Physiological Anestrus—- Ovulatory anestrus— 1. Gestational anestrus
——————Anovulatory anestrus– 1. Prepubertal anestrus 2. Lactational anestrus 3. Postpartum anestrus
Pathological causes of anestrus———- Congenital and hereditary causes of anestrus 1. Ovarian aplasia 2. Ovarian hypoplasia 3. Freemartin
————- Acquired anestrus———— Ovulatory anestrus– 1. Sub-estrus 2. Unobserved estrus 3. Presistent corpus luteum
—— Anovulatory anestrus—- 1. Anovulatory anestrus –I 2. Anovulatory anestrus –II 3. Anovulatory anestrus –III
Physiological Anestrus:
Animals remain anestrus during certain physiological stages which does not related to infertility viz., before puberty, during pregnancy, lactation and early postpartum period. Accordingly, physiological anestrus has been classified into pre–pubertal, gestational, lactational and post-partum anestrus.
Prepubertal Anestrus:
The reasons of pre–pubertal anestrus includes low LH pulse frequency that results in insufficient growth of follicles and high threshold for positive feedback effect of estradiol on LH surge.
Gestational Anestrus:
The elevated level of progesterone during pregnancy exerts negative feedback effect on GnRH secretion from hypothalamus and reduces LH pulse frequency resulting into anestrus. However, some cattle and buffaloes exhibit estrus during early pregnancy (known as gestational estrus) which is seen most often during first four months of pregnancy
Postpartum Anestrus:
Following parturition, all the females undergo through anestrus for a variable but short period of time, known as postpartum anestrus. The period of postpartum anoestrus is usually longer in buffalo than the cattle under similar management conditions probably due to low LH secretion during early postpartum period (Perera, 2011) Under normal conditions, buffaloes resume cyclicity by 30–90 days however; only about 45% of Indian buffaloes resume cyclicity within 90 days postpartum and rest 55% remain in anestrus for about 150 daysThe physiological postpartum anestrus cannot be avoided and is useful to allow uterine involution prior to first postpartum anestrus.
Lactational Anestrus:
Higher level of prolactin in high yielding animals suppresses GnRH secretion and ultimately reduces production of gonadotrophins from pituitary, resulting into anestrus. Pathological Causes Of Anestrus: Certain pathological conditions i.e. ovarian agenesis, dysgenesis or derangement of follicular–luteal dynamics leads to anestrus causing infertility and pose a herd problem. Such conditions may be congenital or acquired.
Classification of anestrus
In buffalo, the anestrus is observed in post-pubertal heifers, during pregnancy, lactation, early postpartum period and during low breeding season. Classification of anestrus in cattle as described by Roberts (1971) can be used also in case of buffalo. He classified the anestrus into two types, i.e. Class I–female with a normal functional corpus luteum and Class II–female with no functional corpus luteum.
Class I anestrus includes (i) Anestrus due to pregnancy, (ii) Anestrus due to persistent corpus luteum (CL), (iii) Anestrus due to ‘weak’ or ‘silent’ estrus, and (iv) Anestrus due to unobserved estrus. Anestrus due to pregnancy is a physiological condition; anestrus due to unobserved estrus is the management problem. However, the anestrus due to persistent CL and silent estrus are the reproductive problems of animals concerned. Persistent CL is usually observed in association with some uterine pathology such as pyometra, fetal maceration, mucometra, mummified fetus and other disease states. Anestrus due to weak estrus or ‘silent estrus’ or ‘silent ovulation’ is the inherent characteristic of buffalo (Zicarelli et al.,1997) that is one of the major problems in buffalo breeding.
Class II anestrus includes anestrus due to small or inactive ovaries with no functional corpus luteum palpable per rectum. These are non-cycling cows. It is termed as ‘true anestrus’. From the clinical point of view, anestrus can be classified broadly into two categories, viz. silent estrus and true anestrus (Noakes et al., 2001). In the first form, the animal possesses a palpable CL in one ovary, but has not been detected in estrus due to subestrus or silent estrus, whereas in the second form, the animal has no palpable CL and does not exhibit estrus because she is acyclical (true anestrus). Silent estrus or quiet ovulation is clinically characterized by failure of overt signs of estrus, though the follicular development and ovulation occurs normally. Sub estrus is common during the post pubertal period in heifers and early post–partum (30 to 120 days) in high yielding animals. Progesterone secreted from regressing CL of previous cycle potentiates the action of estrogen and seems to favour the manifestation of estrus in next cycle (King et al., 1976; Allrich, 1994). Thus, lack of progesterone priming results in sub–estrus. Such conditions have been frequently reported in dairy buffaloes especially in the early postpartum period, during the humid and hot season, in malnutritioned and suckled buffaloes (Shah, 1990; Badr, 1993; ElWishy 2007; Singh et al., 2013) and may be the one of the reasons of prolonged calving interval in buffaloes (Singhal et al., 1984; Barkawi et al., 1986). Due to the high (20–80%) incidence of sub estrus, large numbers of buffaloes are left unbred and substantially contribute to more days open (Honparkhe et al. 2008).
Congenital And Hereditary Causes Of AnestruS: Ovarian agenesis or aplasia (absence of ovary) is extremely rare condition and probably crop up due to inherited autosomal dominant gene. Bilateral aplastic or gonadless heifers appear normal until breeding age but fail to show estrus and normal development of udder at puberty and are sterile. Such reports from India are meager. Ovarian dysgenesis has been identified as ovarian hypoplasia and freemartin. Ovarian hypoplasia (incomplete development of ovary) is caused by single autosomal recessive gene with incomplete penetration. It may be unilateral or bilateral. The incidence of ovarian hypoplasia in Indian cattle has been reported between 0.08–4.3%. Whereas it is less than 1 per cent in Indian buffaloes with a slightly high incidence (1.46%) in Jaffarabadi buffalo In Free martin (sterile heifer born co–twin with bull calf) the ovaries usually fails to develop and remain hypoplastic resulting into anestrus. The incidence of freemartinism in Indian cattle and buffaloes has been reported low i.e. between 0.10 to 0.20% (Sharma et al.,
Anestrus due to persistent corpus luteum (PCL):
In this type of anestrus, the follicular growth proceeds through all the developmental stages and undergo ovulation and CL formation which subsequently turn into anestrus due to failure of luteal regression. This is probably due to absence of estrogenic dominant follicle at the time of luteal regression) secreting adequate estradiol to induce the formation of uterine oxytocin receptors and consequently resulting in to pulsatile release of PGF2α for luteolysis. Retained corpus luteum may also be associated with embryonic death when death of embryo occurs after maternal recognition of pregnancy where corpus luteum persists until resorption of embryo.
Sub–Estrus/Silent Estrus/Quite Ovulation:
Sub estrus is common during the post pubertal period in heifers and early post– partum (30 to 120 days) in high yielding dairy cows. Progesterone secreted from regressing CL of previous cycle potentiates the action of estrogen and seems to favours the manifestation of estrus in next cycle. Thus, lack of progesterone priming results in sub– estrus. Such conditions have been frequently reported in dairy buffaloes especially in summer months (Singh et al., 2013) and may be the one of the reasons of prolonged calving interval in buffaloes. Other causes of sub estrus are heat stress, nutritional deficiencies, overweight, foot lesions, aging and ergotism (fescue toxicity) but most common cause considered for sub estrus is the failure of estrus detection.
Anestrus Due To Failure To Observe Estrus/Unobserved Estrus:
Estrus detection is critical aspect of dairy herd management where artificial insemination is being practiced. Earlier, it was reported that intensity and duration of standing estrus is shorter in Bos indicus cattle as compared to Bos taurus cattle, probably due to small follicular diameter (Bo et al., 2003). However, recent studies indicate that there is no difference in intensity and duration of estrus between Bos taurus and Bos indicus cowsIn high yielding cows, many times the estrus cycles become irregular in terms of its intensity and duration of standing estrus resulting in low estrus detection rates. The condition may be due to low estrogen concentration, insulin and IGF–I mediated deficiency of follicular growth.
Pathogenesis:
The concentration of gonadotrophins are almost negligible in late gestation and for a short duration following parturition due to strong inhibition of hypothalamic– pituitary axis through negative feedback effect of high progesterone secreted by corpus luteum and placenta and estrogen from placenta during last trimester of pregnancy. The concentration of FSH rises within 3–5 (ranges 2 to 7) days after parturition whereas restoration of LH pulsatility and LH surge mechanism takes rather longer period than the FSH (14–28 days). Moreover, growth and maturation of follicle also depends upon bioavailability of insulin, insulin like growth factor (IGF)– I and their binding proteins. Both insulin and IGF–I are potent stimulators of steroidogenesis and granulosa and theca cells proliferation as well as oocytes growth and maturation. Hence, inadequate LH pulse frequency, low concentration of insulin and IGF–I impede the follicular growth and reduces the chance of ovulation. These conditions appear to occur in a state of under nutrition/malnutrition; (Ramoun et al., 2012) and negative energy balance. In a state of negative energy balance, the circulating concentration of non–esterified fatty acid (NEFA) due to mobilization of body reserves and endogenous opioids increases which in turn decreases the pulsatile secretion of LH. Ultimately, follicles become atretic and then regress. The process of follicular growth and regression occurs over and again till the above state of affairs persists resulting into anovulatory anestrus.
Diagnosis Of Anestrus
Based on the information viz., failure of displaying the overt signs of estrus by the animals after attaining puberty or 60–90 days post-partum; Such cases are diagnosed when presented for pregnancy diagnosis. Many times, owners’ complaint that they are not able to detect estrus or have not seen any signs of estrus in that particular animal since long.
Progesterone:
Estimation:True anestrus is usually characterized by a lack of ovarian progesterone production.Presence of basal level (0.5–1 ng/ml) of progesterone in the blood samples at an interval of 8–10 days further confirms the diagnosis. If the concentration of progesterone is more than 1ng/ml, it is suggestive of presence of corpus luteum and anestrus in such situation might be due to unobserved estrus/silent estrus/persistent corpus luteum.
Per Rectal Examination:
Pregnancy can be a prominent cause of anestrus and therefore must be ruled out by careful examination of ovary and uterus when any animals present for gynecological examinations. On per rectal examination, ovaries are smooth, small and inactive with the absence of corpus luteum in true anestrus cattle and buffaloes, however, follicles may develop up to prematuration stage and get atretic (Ghuman et al., 2010). Functional corpus luteum can be palpated in case of silent estrus/unobserved as well as in anestrus due to persistent corpus luteum.
Ultrasonography:
Different stages of follicular growth and type of anestrus can easily be detected by ultrasonography. Transrectal ultrasonographic examination of anestrus buffaloes cows which are not seen in oestrus for 60 or more days postpartum at 12 days revealed 45% inactive ovaries55% silent ovulation or missing heat (Rahman et al., 2012). It can also differentiate between persistent follicle and persistent CL.
Treatment
Anestrus can be treated according to their cause various therapeutic agents including hormonal and non–hormonal compounds have been used extensively for the restoration of cyclicity in anestrus cattle and buffalo by several workers. In order to ensure effective treatment, the health and nutritional status of the animals must be in good conditions. Besides deworming, the supplementation of vitamins, minerals and antioxidants in feed are useful to improve health status of the animals.
Utero–Ovarian Massage: Utero–ovarian massage is the oldest, simplest, cheapest and effective method to induce estrus in anestrus cattle and buffaloes Estrus induction in cattle and buffalo varies between 40 to 80% following utero– ovarian massage daily/on alternate day/weekly for 3–4 weeks .
Lugol’s Iodine
Lugol’s iodine treatment is cheaper and effective means of management of anestrus but response has been variable (45 to 91.7%) among cattle and buffaloes. It is presumed that painting of Lugol’s iodine on posterior part of the cervix causes local irritation and brings about reflux stimulation at anterior pituitary for secretion of gonadotrophins and consequently cyclicity.
Estrogens Based Treatment
Exogenous administration of estrogen produce estrus signs in anestrus animals with or without concurrent ovulation. In presence of dominant follicle, estrogen administration results in expression of estrus and ovulation because of its positive feedback effect over pituitary for LH surge.
Progesterone Based Treatment: Exogenous administration of progesterone mimics the luteal phase of the estrus cycle by exerting negative feedback effect over hypothalamus and pituitary for LH release. Upon withdrawal of progesterone, the normal follicular phase of the cycle is stimulated. However, for such treatment seem to be effective, abrupt decrease in progesterone level is required at the end of treatment .
Treatment with CIDR : The addition of GnRH and eCG to a progesterone-based CIDR protocol substantially improves the estrus induction and pregnancy rates in postpartum anestrous buffaloes (Azawi et al., 2012).
Compiled & Shared by- This paper is a compilation of groupwork provided by the
Team, LITD (Livestock Institute of Training & Development)
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