Timing of ovulation in relation to onset of estrus and LH peak in yak (Poephagus grunniens L.)

Male yaks adapt to heat stress with enhancement of immunomodulation, anti-oxidation, and blood oxygen delivery

Yaks adapt to extremely low temperatures, but they are more susceptible to heat stress (HS). The adaptive mechanisms with crucial plasma protein markers regulating the response to HS remain elusive. In this study, data-independent acquisition proteomics were used to evaluate the thermal adaptability under chronic HS and thermal-neutral conditions. As a result, yaks increased body temperatures and respiratory rates in response to HS. Eight differential proteins mainly related to vasodilatation were decreased by HS, but another four proteins associated with blood oxygen delivery were presented at higher levels. Complement and coagulation cascades pathway was activated by HS, and more proteins were upregulated to protect against inflammation and oxidative stress by higher levels of antioxidant proteins. It is likely that yaks react to HS with enhancement of immunomodulation, anti-oxidation, and blood oxygen delivery, which is conducive to taking appropriate environment and nutrition management strategies to get healthy and high-performing yaks in low-altitude regions during summer.

Physiological and Metabolic Adaptation to Heat Stress at Different Altitudes in Yaks

Yaks have strong adaptability to extremely cold and hypoxic conditions but are susceptible to high ambient temperature when yaks are raised in low-altitude areas during the high-temperature season. Twenty-four adult male yaks with similar weights and ages were randomly divided into TN (Thermoneutral, altitude = 3464 m), LHS (Light heat stress, altitude = 1960 m), and MHS (Medium heat stress, altitude = 906 m) groups to evaluate adaptation strategies to HS. Non-targeted and targeted metabolomics were applied to investigate the effects of different extents of HS on yaks. LHS- and MHS-yaks showed higher rectal temperatures and respiratory rates than TN-yaks. MHS-yaks had higher levels of red blood cells (RBCs), hemoglobin (Hb), whole blood relative index of middle shear at a shear rate of 5 S-1 (WMS), whole blood relative index of high shear at a shear rate of 200 S-1 (WHS), Casson viscosity (CV), middle shear flow resistance at a shear rate of 5 S-1 (MSFR), and high shear flow resistance at a shear rate of 200 S-1 (HSFR) as compared to TN- and LHS-yaks. Differential metabolites and metabolic pathways, including fatty acid metabolism, lipid metabolism, glucose metabolism, and amino acid metabolism, were altered by HS. Metabolites in the glucose metabolism pathway in LHS- and MHS-yaks were lower than those in TN-yaks. However, LHS-yaks showed higher levels of metabolites in the HIF-1 signaling pathway compared to TN- and MHS-yaks. Most of the tricarboxylic acid cycle (TCA) intermediates and fatty acids were significantly decreased in MHS-yaks compared to the other two groups. As a whole, yaks raised at a low altitude (25.6 °C) suffered from severe HS, but they adapted to HS with vasodilatation for dissipating heat and the increased antioxidants and metabolite levels of energy substrates.

Reproduction in female wild cattle: Influence of seasonality on ARTs

Wild cattle species, often considered less alluring than certain conservation-dependent species, have not attracted the same level of interest as the charismatic megafauna from the general public, private or corporate donors, and other funding agencies. Currently, most wild cattle populations are vulnerable or threatened with extinction. The implementation of reproductive technologies to maintain genetically healthy cattle populations in situ and ex situ has been considered for more than 30 years. Protocols developed for domestic cattle breeds have been used with some success in various wild cattle species. However, inherent differences in the natural life history of these species makes extrapolation of domestic cattle protocols difficult, and in some cases, minimally effective. Reproductive seasonality, driven by either photoperiod or nutritional resource availability, has significant influence on the success of assisted reproductive technologies (ARTs). This review focuses on the physiological processes that differ in breeding (ovulatory) and non-breeding (anovulatory) seasons in female cattle, and the potential methods used to overcome these challenges. Techniques to be discussed within the context of seasonality include: estrus synchronization and ovulation induction, ovarian superstimulation, artificial insemination (AI), multiple ovulation embryo transfer (MOET), and ovum pick-up (OPU) with in vitro fertilization (IVF) and embryo transfer (ET).

Protein and mRNA expression of follicle-stimulating hormone receptor and luteinizing hormone receptor during the oestrus in the yak (Bos grunniens)

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) have a central role in follicle growth, maturation and oestrus, but no clear pathway in the seasonal oestrus of yak (Bos grunniens) has been found. To better understand the role of FSH and LH in seasonal oestrus in the yak, six yaks were slaughtered while in oestrus, and the pineal gland, hypothalamus, pituitary gland, and gonads were collected. Using real-time PCR and immunohistochemical assays, we determined the mRNA and protein expression of the FSH and LH receptors (FSHR and LHR) in these organs. The analysis showed that the FSHR mRNA expression level was higher in the pituitary gland tissue compared with LHR (p < .01) during oestrus. By contrast, there was low expression of FSHR and LHR mRNA in the pineal gland and hypothalamus. FSHR mRNA expression was higher than that of LHR (p < .05) in the ovary, whereas LHR mRNA expression was higher than that of FSHR (p < .01) in the uterus. FSHR and LHR proteins were located in the pinealocyte, synaptic ribbon and synaptic spherules of the pineal gland and that FSH and LH interact via nerve fibres. In the hypothalamus, FSHR and LHR proteins were located in the magnocellular neurons and parvocellular neurons. FSHR and LHR proteins were localized in acidophilic cells and basophilic cells in the pituitary gland, and in surface epithelium, stromal cell and gland epithelium in the uterus. In the ovary, FSHR and LHR protein were present in the ovarian follicle. Thus, we concluded that FSHR and LHR are located in the pineal gland, hypothalamus, pituitary and gonad during oestrus in the yak. However, FSHR was mainly expressed in the pituitary gland and ovaries, whereas LHR was mainly expressed in the pituitary gland and uterus.

Identification of candidate miRNAs and expression profile of yak oocytes before and after in vitro maturation by high-throughput sequencing

Small RNA represents several unique non-coding RNA classes that have important function in a wide range of biological processes including development of germ cells and early embryonic, cell differentiation, cell proliferation and apoptosis in diverse organisms. However, little is known about their expression profiles and effects in yak oocytes maturation and early development. To investigate the function of small RNAs in the maturation process of yak oocyte and early development, two small RNA libraries of oocytes were constructed from germinal vesicle stage (GV) and maturation in vitro to metaphase II-arrested stage (M II) and then sequenced using small RNA high-throughput sequencing technology. A total of 9,742,592 and 12,168,523 clean reads were obtained from GV and M II oocytes, respectively. In total, 801 and 1,018 known miRNAs were acquired from GV and M II oocytes, and 75 miRNAs were found to be significantly differentially expressed: 47 miRNAs were upregulated and 28 miRNAs were downregulated in the M II oocytes compared to the GV stage. Among the upregulated miRNAs, miR-342 has the largest fold change (9.25-fold). Six highly expressed miRNAs (let-7i, miR-10b, miR-10c, miR-143, miR-146b and miR-148) were validated by real-time quantitative PCR (RT-qPCR) and consistent with the sequencing results. Furthermore, the expression patterns of two miRNAs and their potential targets were analysed in different developmental stages of oocytes and early embryos. This study provides the first miRNA profile in the mature process of yak oocyte. Seventy-five miRNAs are expressed differentially in GV and M II oocytes as well as among different development stages of early embryos, suggesting miRNAs involved in regulating oocyte maturation and early development of yak. These results showed specific miRNAs in yak oocytes had dynamic changes during meiosis. Further functional and mechanistic studies on the miRNAs during meiosis may beneficial to understanding the role of miRNAs on meiotic division.

Application of sensitive enzymeimmunoassay for determination of testosterone in blood plasma of yaks (Poephagus grunniens L.)

As an alternative to radioimmunoassays, a simple, highly sensitive and quick enzymeimmunoassay (EIA) for determination of testosterone in blood plasma of yaks on microtitreplates using second antibody coating technique and testosterone-horseradish peroxidase as a label has been developed for the first time. The wells of the microtitreplate were coated with affinity-purified goat immunoglobulin (antirabbit IgG) that binds the hormone specific antibody. The EIA was carried out directly in 20 mICROl of plasma after 1:10 dilution with assay buffer. The testosterone standard curve ranged from 0.2 to 200 pg/well. The sensitivity of the assay was 0.20 pg/well. Testosterone standard curve in buffer showed parallelism with serially diluted yak plasma containing high endogenous testosterone. Intra- and inter-assay coefficients of variation (CV) determined using pooled plasma was found 5.24 and 8.54%, respectively. Recovery of known concentrations of added testosterone in charcoal stripped plasma was linear (r=0.98). For biological validation of testosterone enzymeimmunoassay, the blood samples were collected from yak cows at -2h before and thereafter at 2h interval until 24h. after gonadotropin releasing hormone (GnRH) administration. There was a rapid increase (p<0.01) of luteinizing hormone (LH) and testosterone 2 and 6h after GnRH administration. Plasma testosterone concentration in normal adult yak bulls was found to be 0.52+/-0.09 ng/ml. In conclusion, the EIA developed in this study is simple, highly sensitive, valid and sufficiently reliable method for estimation of testosterone directly in yak plasma.

Efficacy of Heatsynch protocol for induction of estrus, synchronization of ovulation and timed artificial insemination in yaks (Poephagus grunniens L.)

The objective of this study was to test the efficacy of induction of estrus, synchronization of ovulation and timed artificial insemination in anestrous yaks using the Heatsynch protocol. In Experiment 1, 10 anestrous yaks were administered an analogue of gonadotropin releasing hormone (GnRH) followed by prostaglandin (PG)F2alpha 7 days later and then estradiol cyponate (ECP) 24 h after that. Ovulation was detected by rectal palpation at 2h intervals beginning at the initial signs of estrus. Blood samples were collected at 2h intervals beginning at the time of ECP injection up to 2h after the occurrence of ovulation for the determination of LH and progesterone. All the animals responded to the Heatsynch protocol with expression of estrus and synchronization of ovulation. The mean time interval from the ECP injection to ovulation was 59.4+/-2.62 h (range 50-72 h). The interval from the LH peak to ovulation was 30.2+/-2.3 h. The high degree of synchrony in ovulation could be attributed to the synchrony in the timing of LH peaks. In Experiment 2, 10 anestrous yaks were treated with the Heatsynch protocol (as in Experiment 1) and TAI was performed at 48 and 60 h after the ECP treatment. Concurrently, 16 cycling yaks were inseminated approximately 12 h after detection of spontaneous estrus. Pregnancy rates were similar in both groups, 40% for TAI and 43.75% for yaks inseminated following spontaneous estrus (p>0.05). From this study, two conclusions can be drawn. First, the Heatsynch protocol can be successfully used to induce and synchronize estrus in anestrous yaks and, second, ovulation following the Heatsynch protocol is synchronized adequately to permit the use of fixed time AI in this species.

Oestrous Behaviour and Timing of Ovulation in Relation to Onset of Oestrus and LH Peak in Mithun (Bos frontalis) Cows

The objectives of the study were to evaluate the oestrus behaviour and to determine the timing of ovulation in relation to onset of oestrus and the pre-ovulatory LH surge in mithun (Bos frontalis). For this purpose, the blood samples collected at 15-min intervals for 9 h period following onset of oestrus and thereafter, at an interval of 2 h till 4 h post-ovulation for three consecutive cycles from 12 mithun cows were assayed for plasma LH and progesterone. Ovulation was confirmed by palpation of ovaries per rectum at hourly intervals. Various signs of behavioural oestrus were also recorded. The common signs of oestrus and their frequency of occurrence in mithuns were following and mounting by male mithuns (100%), standing to be mounted (100%), frequent urination (62.33%), raising of tail (65.23%), swelling of vulva (54.26%) and congestion of vulvar mucous membrane (69.87%). The pre-ovulatory LH surges consisted of several pulses (2.92 +/- 0.26 pulses/animal; range, 1-4). The mean (+/-SEM) peak level of LH for individual mithun varied from 6.99 +/- 0.44 to 12.69 +/- 2.10 ng/ml and the mean pooled LH peak concentration was 9.10 +/- 0.60 ng/ml. The highest peak (highest amplitude of LH during LH surge) was 10.83 +/- 0.76 ng/ml (range, 8.07-16.49 ng/ml). The duration of LH surge was 6.98 +/- 0.22 h (6-8 h). Onset of LH surge was at 1.23 +/- 0.17 h post-oestrus onset (range, 0.25-2.25 h). Mean plasma progesterone stayed low (<0.24 ng/ml) during the entire duration of sampling. Ovulation occurred at 26.92 +/- 0.31 (range, 26-29 h) after the onset of oestrus and 18.63 +/- 0.35 h (range, 17-20.75 h) after the end of LH surge. The occurrence of the highest LH peaks within a narrow time frame of 2- to 5-h post-oestrus onset in mithuns could have contributed to the animals ovulating within a narrow time interval. These results are very promising from a practical standpoint of potential success when AI program in this species is implemented in a big way. Furthermore, the results of the occurrence of LH pulses during pre-ovulatory LH surges, which are required for ovulation in this species of animals, is unique and species specific.

Calves Born from Anestrus Yaks (Poephagus grunniens L.) Subjected to Ovsynch and Superovulation Treatment

An attempt was made to induce estrus and ovulation in eight anestrus yaks by use of the Ovsynch protocol. Six out of eight yaks were successfully induced into estrus, and ovulation occurred in all the responding yaks 1-2 days after the second GnRH administration. Out of the six animals that responded to the treatment, two mated naturally with yak bulls, and calves were obtained from them. The other four animals were further administered a superovulatory regimen of Folltropin (FSH-P). Following Folltropin and Ilerin (a PGF(2alpha) analog) treatment, the animals were subjected to natural insemination. Only one animal in which natural mating occurred was flushed non-surgically for embryo recovery 7 days post-insemination. Thereafter, all the donor animals were administered with Ilerin. After 48-72 h, they came into heat and mated naturally with yak bulls, and calves were obtained from them after expiration of the normal gestation period. Following superovulation, the average numbers of palpable corpora lutea in the right and left ovaries were 2.25+/-0.6 and 1.75 +/-0.3, respectively. Three embryos were recovered by non-surgical flushing from a single animal. One embryo was transferred to a recipient yak, who produced one female calf after 258 days. This is the first report of production of a yak calf through embryo transfer-technology.

Relationship of plasma estradiol-17beta, total estrogen, and progesterone to estrus behavior in mithun (Bos frontalis) cows

The objectives of this study were (1) to establish the characteristics of estrus behavior in mithun cows (n = 12) and (2) to determine the relationships between this behavior and the plasma concentrations of estradiol-17beta (E2), total estrogen, and progesterone. Estrus was detected by visual observations of estrus signs, per recta examination of genitalia and bull parading thrice a day for three consecutive cycles. Among the behavioral signs of estrus, the cow to be mounted by bull (100%) was the best indicator of estrus followed by standing to be mounted (92%). Per rectum examination of genital organs revealed relaxed and open os externa of cervix, turgid uterus, and ovaries having palpable follicles in all animals. The mean (+/-SEM) length of estrus cycle and duration of estrus were recorded to be 21.8 +/- 0.69 days and 12.6 +/- 1.34 h, respectively. Endocrine profiles during the peri-estrus period showed that the mean highest peak concentrations of E2 (27.29 +/- 0.79 pg/ml) and total estrogen (45.69 +/- 2.32 pg/ml) occurred at -3.90 +/- 2.27 and -3.89 +/- 2.26 h prior to the onset of estrus, respectively. Plasma progesterone concentration was basal (0.14 +/- 0.001 ng/ml) during the peri-estrus period. Plasma E2 and total estrogen were found to increase from 6 days before estrus to reach a peak level on the day of estrus and decline thereafter to basal level on day 3 of the cycle. The plasma progesterone concentration was the lowest on the day of estrus showing gradual increase to register a peak level on day 15 of the cycle. Estrus behavior was found to be positively correlated with the maximum peak concentration of E2 (r = 0.89; P < 0.0001) and total estrogen (r = 0.66; P = 0.019) during the peri-estrus period. The mean total estrogen concentration during the peri-estrus period was significantly correlated with estrus behavior (r = 0.60; P = 0.04). The correlations between the estrus behavior and E2:progesterone ratios at 6 days before the onset of estrus (r = 0.92) and on the day of estrus (r = 0.95) was significant. The total estrogen:progesterone ratios at 6 days before the onset of estrus and on the day of estrus were also positively correlated with the estrus behavior (r = 0.86 and 0.88). In conclusion, our results suggest that the maximum peak concentration of E2 and total estrogen and mean level of total estrogen during the peri-estrus period and the E2:progesterone and total estrogen:progesterone ratios on 6 days before the onset of estrus and on the day of estrus are the important factors contributing the behavioral manifestation of estrus in mithun cows.