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J A Abecia

Publications and source records attributed to J A Abecia.

18 recordsLinked to original sources
PubMed2007

Development of a simple enzyme immunoassay for the determination of ovine luteinizing hormone.

The present study describes the development and validation of a simple sensitive and specific sandwich enzyme immunoassay (EIA) for the quantification of ovine luteinizing hormone (LH) in plasma. Microtitre plates were coated with the capture antibody 518b7 anti-bovine LH. A second peroxidase-labelled anti-ovine LH antibody was used as tracer. A simple 3-step procedure was used for the sample analysis; (1) incubation of standards and samples with the pre-coated antibody plates for 2 h at 37 degrees C; (2) incubation with the peroxidase-labelled antibody for 1 h at room temperature; and (3) colour development with TMB substrate. A linear dose-response curve was obtained in the range 0-10 ng/ml (r2 > 0.99). The detection limit was 0.05 ng/ml, and the intra-assay and inter-assay coefficients of variation were 7% and 11.7%, respectively. The theoretical stability of microplates and reagents was calculated, this being greater than one year. Low or undetectable cross-reactivities were recorded for follicle-stimulating hormone, bovine thyroid-stimulating hormone, equine chorionic gonadotrophin and a gonadotrophin-releasing hormone (GnRH) analogue. The EIA was biologically validated by the determination of plasma LH concentrations of nine Rasa Aragonesa ovariectomized and estradiol-implanted ewes after a double GnRH challenge. In conclusion, this enzyme immunoassay provides an efficient, simple and sensitive method for the routine analysis of ovine LH.

Animals↗
PubMed2006

Effects of ageing and exogenous melatonin on pituitary responsiveness to GnRH in ewes during anestrus and the reproductive season.

The study examined the effect of melatonin implants on in vivo pituitary responsiveness to GnRH in control, fully productive (5.7+/-0.4 years old, n=17) and aged (10.7+/-0.3 years old, n=14) ovariectomized, estradiol-treated Rasa Aragonesa ewes. On 27 February, eight ewes in each age group received a single implant containing 18 mg melatonin. On 10 April, blood samples to be assayed for LH were collected at 10-min intervals over 4h (starting at 09:00 and 22:00 h). After samples 6 and 18 were collected, ewes received a single i.v. injection of GnRH (20 ng/kg liveweight). The pituitary response to GnRH was assessed using the difference between plasma LH concentrations before and after (highest value) each injection (DLH1, DLH2)), and the area under the LH response curve for 1h after each GnRH injection (AUC1, AUC2). On 23 September, the previously implanted ewes received a new melatonin implant and, on 17 November, all of the ewes were subjected to the same diurnal and nocturnal sampling protocols, again. Generally, non-implanted aged ewes exhibited a lower pituitary response to GnRH than did non-implanted control ewes, particularly in November and after the first injection (P<0.05 for DLH1 and AUC1 in both the diurnal and nocturnal tests). The response was significantly affected by the interaction of age and melatonin treatment, particularly in the diurnal tests (P<0.1 for DLH1 and AUC1, and P<0.05 for AUC2 in April; P<0.05 for DLH1, AUC1 and AUC2 in November), which indicated that exogenous melatonin increased LH levels after GnRH injections in aged ewes compared to non-implanted ewes, this effect being the opposite in control females. Thus, melatonin can restore in ewes the functionality of the neuroendocrine system, after it has been reduced by senescence.

Aging↗
PubMed2006

Effect of undernutrition on uterine progesterone and oestrogen receptors and on endocrine profiles during the ovine oestrous cycle.

In the present study, it was investigated whether undernutrition affected the binding capacity, immunoreactivity and mRNA expression for uterine oestrogen and progesterone receptors (ER and PR, respectively) in sheep, as well as whether the responses were associated with changes in plasma concentrations of progesterone (P4), oestradiol (E2), glucose, fatty acids, insulin, leptin and insulin-like growth factor (IGF)-I during the oestrous cycle. Twenty ewes were fed either 1.5 (C) or 0.5 (L) times their maintenance requirements and were killed on Day 5 or 14 of the cycle (Day 0 = oestrus). Compared with Group C, Group L had higher concentrations of non-esterified fatty acids and lower concentrations of insulin, leptin and IGF-I. Group L also had higher plasma concentrations of P4 during the final days of the luteal phase. At oestrus in both treatment groups, there were peaks in the concentrations of glucose, insulin and IGF-I. For ER and PR, transcript expression, binding capacity and immunoreactivity were higher on Day 5 than on Day 14 of the cycle. The binding capacities for ER and PR were lower in Group L than in Group C on Day 5. Group C showed more immunoreactive staining for ER than did Group L in two of five cell types, whereas no effect of treatment was observed for PR immunoreactivity. There was more PR mRNA in the uterine horn contralateral to the corpus luteum in Group C than in Group L ewes. We conclude that undernutrition impairs steroid receptor expression and binding capacity. This may alter the uterine environment and help explain the reductions in embryo survival.

Animals↗
PubMed2005

The effect of melatonin treatment on the ovarian response of ewes to the ram effect.

To determine the ovarian response to the ram effect after treatment with melatonin, on 8 March, 71 Rasa Aragonesa ewes were randomly assigned to either the treatment group and given an 18mg melatonin implant or the untreated group. On 19 April (day 0), rams were introduced into the flock. Melatonin treatment produced a significantly higher percentage of cyclic ewes at ram introduction (P<0.05). Melatonin-treated ewes had their first oestrus after ram introduction significantly earlier than did untreated ewes (P<0.0001), and the groups differed in the distribution of their ovarian response. Most (80%) of the treated ewes exhibited a silent ovulation followed by a cycle of normal duration, whereas about half (52%) of the untreated ewes exhibited a silent ovulation, a short cycle, and another silent ovulation followed by a cycle of normal duration (P<0.05). At ram introduction, melatonin-treated ewes, cyclic and non-cyclic, had higher mean plasma progesterone concentrations than did untreated ewes. The proportion of ewes that mated within the first 17 days of the mating period was significantly higher among the treated ewes than in the untreated ewes (P<0.0001). Furthermore, at lambing, 39% of the melatonin-treated ewes lambed within the first 17 days of the lambing period, while none of the untreated ewes lambed in that period. The untreated group exhibited peaks in mating between days 18 and 21, and particularly, between days 22 and 25, when the majority of ewes lambed; peaks did not occur in the treatment group. Treated and untreated ewes did not differ significantly in fertility, litter size and fecundity. In conclusion, melatonin treatment modifies the ovarian response to the ram effect in ewes, which leads to modifications in mating patterns, and consequently, the lambing curve.

Animals↗
PubMed2005

The effect of melatonin implants during the seasonal anestrus on embryo production after superovulation in aged high-prolificacy Rasa Aragonesa ewes.

The aim of this study was to assess the effect of melatonin implants administered in March on the ovarian cyclicity, ovulatory response and embryo production after repeated superovulation of selected high-prolificacy Rasa Aragonesa aged ewes. During the seasonal anestrus of two consecutive years, 113 superovulatory treatments have been performed. Ewes were treated (M) or not (C) with melatonin implants in March (day 0). All of them received intravaginal progestogen sponges on day 24 (recovery 1) and 80 (recovery 2) after melatonin implants insertion in year 1, and on day 28 and 77 in year 2. The intravaginal sponges were removed after 14 days. Superovulatory treatments consisted of eight doses in decreasing concentrations (2 mL x 2 and 1 mL x 6) of oFSH (Ovagen) administered twice daily starting 72 h before sponge removal. Seven days after the onset of estrus, embryos were recovered by laparotomy. Melatonin increased cyclicity only in recovery 2 year 2 (83% versus 42%; P < 0.05) but not in the other experimental periods. Among the 78% (88) ewes that ovulated and produced functional corpora lutea, melatonin implants tended to improve embryo viability in recovery 2 by increasing the number of blastocysts per superovulatory treatment (2.4 +/- 0.6 versus 1.1 +/- 0.4; P = 0.09), the rate of viability (67 +/- 9% versus 43 +/- 9%; P < 0.05), and freezability (55 +/- 9% versus 33 +/- 8%; P < 0.05). More specifically, melatonin induced a significant reduction of the number and rate of non-viable (degenerate and retarded) embryos in recovery 2 (0.4+/-0.1 embryos versus 1.3 +/- 0.3 embryos and 4 +/- 1% versus 22 +/- 6%, respectively; P < 0.05). Our results demonstrate that melatonin implants in March can improve at medium term (3 months after implantation) the viability of embryos collected from selected high-prolificacy Rasa Aragonesa aged ewes after superovulation.

Anestrus↗
PubMed2004

Effect of plane of nutrition on endometrial sex steroid receptor expression in ewes.

The effect of plane of nutrition on progesterone receptor (PR) and estrogen receptor alpha (ERalpha) expression in ovine endometrium was investigated. Rasa Aragonesa ewes (n=26) were fed diets to provide either 1.5 (Group C) or 0.5 (Group L) times the daily maintenance requirement and were slaughtered at Days 5 or 10 of the estrous cycle (Day 0=estrus). PR and ERalpha immunoreactivity were analyzed in eight endometrial cell compartments, defined by cell type and location. Group L had less PR immunostaining on Day 5 (P<0.05), which is consistent with lesser endometrial content of progesterone found in such animals. Most cell types of Group C had down regulation of PR at Day 10, but in Group L, this pattern was observed only in three cell compartments. The lesser PR contents found at Day 5 in Group L ewes may explain the lack of inhibition of PR. No effect of treatment or day of the estrous cycle was observed in ERalpha. Results indicate that endometrial PR is affected in a cell type, in specific manner, by plane of nutrition.

Animals↗
PubMed2002

The effect of melatonin implants on the response to the male effect and on the subsequent cyclicity of Rasa Aragonesa ewes implanted in April.

Rasa Aragonesa ewes were used to evalutate whether treatment with melatonin implants in spring could modify: (i) the response to the male effect in terms of oestrous behaviour and ovulation rate; and (ii) the maintenance of sexual activity and ovulation rate at medium term, i.e. over the next 306 days. On 12 April, 42 ewes were divided into two groups, with (M; n = 21) or without (C; n = 21) a subcutaneous implant containing 18 mg melatonin. On 17 May (day 0), three aproned rams were introduced to each group to induce a ram effect. Ewes were observed for oestrus daily. The rams were removed 40 days later after which one aproned ram was introduced daily. Oestrous detection continued until 28 February, 306 days after the first male-female contact. The ovulation rate was determined by endoscopy in the first three cycles after ram introduction and in September-October and January. Progesterone was assayed from blood samples taken on 6 May, 10 and from day 0 to day 22 after ram introduction. Luteal activity before ram introduction was seen in 33% (M) and 29 (C)% of the ewes, respectively. Significantly more M ewes showed oestrous behaviour during the first 40 days after ram introduction (M: 100%; C: 62%; P < 0.01). Similar differences were observed for ewes anovulatory at ram introduction (M: 100%, C: 47%; P < 0.01). These differences were maintained over the three oestrous cycles in both groups. Treatment with melatonin implants was without detrimental effect on cyclic functions in the following breeding season, after seasonal anoestrus. Melatonin treatment significantly increased (P < 0.05) the mean ovulation rate of the first (1.62 +/- 0.11 versus 1.31 +/- 0.13), second (1.78 +/- 0.15 versus 1.36 +/- 0.15) and third cycles (M: 1.73 +/- 0.12 versus C: 1.27 +/- 0.14). There was a significant interaction between the effects of cyclicity at day 0 and melatonin treatment on the ovulation rate in the first cycle (P < 0.05). The mean ovulation rates of both groups were similar at the beginning (September) and middle (January) of the subsequent breeding season. Overall, the results confirmed that melatonin implants, combined with the ram effect, improved the reproductive parameters of reduced-seasonality ewes during spring mating, without impairing sexual activity or ovulation rate during the subsequent breeding season.

Animals↗
PubMed2002

The effect of melatonin on the secretion of progesterone in sheep and on the development of ovine embryos in vitro.

Two experiments were carried out in order to determine whether melatonin can improve secretion of progesterone in vivo, and its effect on embryonic development in vitro. In the first experiment, blood samples were collected from 5 ewes at 15 min intervals for 2 h at 7 and 10 days after withdrawal of progestagen pessaries. The first hour constituted a control period, which ended with an intravenous administration of 3 microg/(kg bw)(0.75) melatonin. All the ewes on day 7 and three of the ewes on day 10 showed a progesterone response to melatonin challenge, defined as an increase in the plasma progesterone concentration in at least two consecutive samples during the post-treatment period above the mean+2SD of the values in the pre-treatment period. A paired t-test revealed a significant effect of melatonin on the overall plasma progesterone concentrations before and after the challenge, both on day 7 (pre, 0.61 +/- 0.11; post, 0.73 +/- 0.13 ng/ml; p<0.01) and day 10 (pre, 1.16 +/- 0.19; post, 1.30 +/- 0.20 ng/ml; p<0.05). Ninety-one thawed embryos (46 morulae and 45 blastocysts) were used in the second experiment, being cultured with or without 1 microg/ml melatonin. If the embryos were blastocysts when the culture started. melatonin increased the percentage that had hatched after 24 h of culture (p<0.01), and there was a lower percentage of degenerated embryos at the end of the incubation period (p<0.05). It may be concluded that melatonin treatment in sheep can increase both fertility and prolificacy by improving luteal function and embryonic survival.

Animals↗
PubMed2001

Differences in reproductive performance, embryo development, interferon-tau secretion by the conceptus and luteal function in ewe lambs synchronized in oestrus before or after the spontaneous onset of luteal activity preceding puberty.

In mid-September, 1 month before the insertion of intravaginal pessaries to induce sexual activity, blood samples were collected every 4 days from 16 ewe lambs aged 7 months, in order to determine the incidence of ovulations by measurement of plasma progesterone concentrations. It has been studied whether the response to a progestagen treatment of ewe lambs apparently close to puberty could be modified by the onset of the ovarian events preceding puberty. The effect of the presence or absence of ovulations prior to progestagen treatment on the potential reproductive performance (fertility, litter size and fecundity), embryo development [embryo quality and interferon-tau (IFNtau) secretion], luteal function (progesterone secretion in vitro) and endometrial progesterone content was studied in seven ovulating (Ov+) and nine nonovulating ewe lambs (Ov-) on day 14 after mating. The best potential reproductive results were obtained with Ov+ animals, although these differences could not be initially attributed to either different progesterone secretion in vitro or concentration of endometrial progesterone. Irrespective of the experimental groups, secretion of progesterone by luteal tissue from ewe lambs with normal embryos was significantly greater (p<0.05) than that of animals with abnormal embryos or with no embryos. Normal embryos secreted a higher amount of IFN-tau than those embryos classified as abnormal (p<0.07). In conclusion, ewe lambs which exhibit luteal activity before puberty have the highest levels of reproductive performances after a progestagen treatment. Corpora lutea from ewe lambs with normal embryos had higher rates of progesterone secretion in vitro and their embryos had a higher IFN-tau production by the embryos, indicating greater capacity for subsequent development.

Animals↗
PubMed1999

A preliminary report on the effect of dietary energy on prostaglandin F2 alpha production in vitro, interferon-tau synthesis by the conceptus, endometrial progesterone concentration on days 9 and 15 of pregnancy and associated rates of embryo wastage in ewes.

Two groups of ewes were fed to provide 1.70 x (high energy group; n = 15) or 0.56 x (low energy group; n = 15) energy requirements for maintenance of liveweight from 14 d before a synchronized mating in November until slaughter at 9 or 15 d after mating. We investigated the effects on interferon-tau (IFN tau) secretion by the conceptuses, prostaglandin F2 alpha (PG) production in vitro by endometrial tissue, and associated rates of embryo mortality, endometrial progesterone content and progesterone production by luteal tissue. No differences between groups in pregnancy rate were detected on Day 9 between the 2 groups. Proportionately (6/6 vs 2/5), there were more pregnant ewes in the high energy group on Day 15, although this difference did not reach significance (P = 0.06). The proportion of corpora lutea represented by embryos was significantly lower in undernourished ewes (P < 0.05). Secretion in vitro of PG was lower in the 2 pregnant ewes of the low energy group on Day 15, and it was accompanied by higher IFN tau secretion by conceptuses recovered from these ewes. However, the limited number of pregnant ewes recorded on Day 15 prevented any statistical comparison. Neither mean endometrial content of progesterone nor ovarian venous progesterone concentrations and production of progesterone by luteal were affected by nutrition. The provisional results of the present experiment indicate that undernutrition may induce a reduction in the rate of secretion of IFN tau and can therefore increase production of PG from the endometrium. This could initiate luteolysis. The lower pregnancy rates observed in underfed ewes could be mediated through this alteration in the signal of maternal recognition of pregnancy. However, these findings remain to be shown in further experiments including a larger number of animals, as they only represent data from 2 undernourished animals.

Animal Feed↗
PubMed1998

Opioidergic and nutritional involvement in the control of luteinizing hormone secretion of postpartum Rasa Aragonesa ewes lambing in the mid-breeding season.

The role of endogenous opioids and nutrition on the inhibition of luteinizing hormone (LH) secretion during the postpartum period was investigated in a Spanish breed of sheep lambing in the mid-late breeding season. Two groups of adult Rasa Aragonesa ewes housed in individual pens and lambing on 30 December were fed during the suckling period to provide maintenance requirements and the production of 1.1 (M; n = 8) or 0.55 (L; n = 8) kg of milk per day. On days 10, 20 and 30 after lambing, the effect of a treatment with the opiate receptor antagonist naloxone (1 mg/kg at four hourly intervals) on LH secretion was assessed in half of the ewes of each group, the remaining females receiving four saline injections. After weaning, animals were fed to provide requirements for maintenance of liveweight. Blood samples were collected twice a week from day 20 postpartum until the end of March, and assayed for progesterone and prolactin. Although underfed ewes showed significantly lower mean plasma concentrations during the control period on day 20 postpartum, nutrition did not seem to modify LH secretion before naloxone or saline injections. Moreover, no differences between nutritional groups in the response to naloxone injections on pattern of LH secretion were found. In fact, naloxone treatment induced an increase of mean LH concentrations on days 10, 20 and 30 postpartum (at least, P < 0.05), of LH pulse frequency on days 20 and 30 (P < 0.05), and of LH pulse amplitude on days 10 and 20 (P < 0.05). Underfed ewes during the postpartum period showed a slower decline in plasma prolactin levels, with significant differences on days 29, 36 and 39 after lambing (P < 0.05). Only 3 M ewes ovulated before the onset of the seasonal anoestrus period. It is concluded that endogenous opioids are involved in the inhibition of LH secretion during the early suckling period of a reduced seasonality breed of sheep without any influence of nutrition on the response to naloxone treatment; however, ewes underfed before weaning failed to reactivate their cyclicity prior to the onset of the seasonal anoestrus.

Animal Nutritional Physiological Phenomena↗
PubMed1998

Effect of undernutrition on the distribution of progesterone in the uterus of ewes during the luteal phase of the estrous cycle.

The effect of undernutrition on ovarian and uterine venous progesterone concentrations and endometrial progesterone content on Days 5 and 10 of the estrous cycle were studied. Forty ewes were synchronized using progestagen pessaries. At pessary withdrawal, the ewes were fed diets to provide either 1.5 or 0.5 times the daily maintenance requirement (Group H, n = 20 and Group L, n = 20, respectively). Ewes fed the low nutrition diet (Group L) had higher mean peripheral progesterone concentrations than those fed the high plane diet (Group H; P < 0.05) but lower endometrial progesterone content on Day 5 (P < 0.05). Neither ovarian nor uterine venous levels were affected by nutrition on either Day 5 or 10. Progesterone concentrations in blood samples collected ipsilateral to ovaries bearing a corpus luteum (CL) were higher than in the contralateral samples (P < 0.001). It is concluded that undernutrition can produce a reduction of endometrial content of progesterone the first week after mating. Since no differences in ovarian venous concentrations were observed, it remains to be shown whether this variation is due to other variables, such as the population of endometrial progesterone receptors or other nonhormonal factors.

Animals↗
PubMed1997

Effect of level of dietary energy and protein on embryo survival and progesterone production on day eight of pregnancy in Rasa Aragonesa ewes.

The aim of this experiment was to investigate the effects of dietary protein and energy on ovulation rate and embryo survival to day 8 of pregnancy, and the associated concentrations of progesterone in jugular, ovarian and uterine veins, in a Spanish breed of sheep. In mid-October, three groups of ewes were fed to provide 1.5 x (H; n = 9), 0.5 x (L; n = 12) or 0.5 x plus 7.44 g CP/MJ ME (LP; n = 8) energy requirements for maintenance of live weight from day -14 relative to a synchronized mating on day 0. A significant effect of nutrition on ovulation rate was observed (H: 2.22 +/- 0.16; L: 1.50 +/- 0.16; LP: 1.88 +/- 0.12 corpora lutea; P < 0.05). Mean LH and progesterone concentrations were affected by nutrition on day 7, L ewes showing the highest mean LH level (P < 0.01), while H ewes presented the lowest mean LH concentration and the highest mean plasma progesterone concentration (P < 0.01). Laparotomies were performed on six animals of each group on day 8 to determine the effect of nutrition on embryo development. A significantly higher percentage of embryos recovered from L and LP ewes presented an earlier stage of development (morulae or early blastocysts) (P < 0.001), while 100% embryos of H ewes were expanded blastocysts. The ratio expanded blastocysts/corpora lutea was significantly higher in H ewes (0.86) when compared with L and LP groups together (0.57; P < 0.05). Mean progesterone concentration in the ovarian vein was 800-fold higher than mean jugular venous levels with no differences between groups. Samples from ovarian veins contralateral to corpus luteum-bearing ovaries showed mean progesterone concentrations significantly lower than samples opposite to corpus luteum (ipsilateral: 1037.84 +/- 138.45; contralateral: 30.4 +/- 11.22 ng/ml; P < 0.001). Mean progesterone concentration in the uterine vein was approximately 30-fold higher than in jugular and similar in both uterine horns and treatments. No effect of nutrition on pregnancy rate was observed (H: 89%; L: 92%; LP: 100%). These results suggest that neither dietary energy nor protein are able to modify pregnancy rate or progesterone concentrations in ovarian and uterine veins eight days after mating. However, the delay in embryo development observed in the embryos collected from L and LP ewes may give rise to compromised embryo growth and development some days later.

Animal Nutritional Physiological Phenomena↗
PubMed1995

Effect of exogenous melatonin and plane of nutrition after weaning on estrous activity, endocrine status and ovulation rate in Salz ewes lambing in the seasonal anestrus.

Forty-nine Spanish Salz ewes lambing in the second fortnight of March (20 March +/- 1.5 d) were used to determine the effects of exogenous melatonin and postweaning nutrition on endocrine status, date of first estrus and ovulation rate. Experimental design was a factorial defined by 2 postweaning planes of nutrition, 1.80 (high) and 1.35 (low) times the maintenance requirements, and treatment with a single 18-mg subcutaneous implant of melatonin (M) 32 d after lambing or no treatment control (C). Mean weaning to first estrus interval was shorter in treated than in control ewes (50.8 +/- 4.2 vs 87.6 +/- 6.3 d; P < 0.01). Considering both the treated and control animals together, the ratio between mean night and daytime plasma melatonin levels was significantly correlated with the implant insertion-first estrus interval on Day 5 (0.67; P < 0.01) and Day 35 (0.63; P < 0.05) after implantation. Melatonin implants induced a significant increase of mean LH concentrations at Days 14 and 33 after implantation (P < 0.01) without any significant influence of plane of nutrition. Ovulation rate was higher for treated than control ewes in the second estrus (P < 0.05). An interaction between plane of nutrition and exogenous melatonin on ovulation rate at the second cycle after weaning was detected (P < 0.01), being close to the significance in the first, fourth and fifth cycles (P < 0.1). These results suggest that exogenous melatonin in April may be an effective way of advancing the breeding season and enhancing ovulation rate associated with a low rather than a high plane of nutrition.

Journal Article↗
PubMed1993

Effect of plane of protein after weaning on resumption of reproductive activity in Rasa Aragonesa ewes lambing in late spring.

The effect of protein supplementation after weaning on the resumption of reproductive activity in a Spanish breed of ewes (Rasa Aragonesa) with a reduced seasonality was studied. Two equal groups of ewes were weaned in the first 2 weeks of July. From weaning to the end of the experiment both groups were fed identical energy-content rations but with different protein levels (high, Group H; low, Group L). The mean time between weaning and first detected estrus was 64 days. No differences between groups were found either in relation to this interval or in the ovulation rate in the first estrus. Ewes showing a multiple ovulation rate in the first cycle anticipated the onset of sexual activity after weaning. Significant differences in the ovulation rate were detected between the 2 groups from September to the end of the experiment (1.55 vs 1.05 corpora lutea for Groups H and L, respectively; P<0.001). In conclusion, the effect of a protein supplement after weaning in Rasa Aragonesa ewes lambing in late spring is reflected at mid-term in the early breeding season, with an evident rise of ovulation rate in the nutrient supplemented group.

Journal Article↗