Effect of gonadotropin-releasing hormone on clinical response and fertility in cows with cystic ovaries, as related to milk progesterone concentration and days after parturition

We gave gonadotropin-releasing hormone (GnRH) or an analog of GnRH to 264 lactating cows with cystic ovaries. The effects of milk progesterone concentration (MPC) and days after parturition (DAP) at diagnosis on clinical response 30 days after treatment and on subsequent fertility were examined. Palpation per rectum revealed ovarian cysts in 264 cows; 118 had true follicular cysts (MPC less than 1 ng/ml). Clinicians with more than 3 years of experience reported significantly more true cysts than did less experienced clinicians. Clinical response 30 days after treatment did not differ in 3 groups of cows (divided on the basis of MPC at treatment), but fewer cows with MPC less than 1 ng/ml were bred or conceived than were cows with MPC greater than or equal to 33 ng/ml. Days after parturition at diagnosis did not affect 30-day clinical response rate, but cows treated less than 35 DAP had significantly more days to first estrus and to conception than did cows treated greater than 90 DAP. Significantly more cows treated less than 35 DAP had MPC less than 1 ng/ml at treatment.     

Use of milk progesterone enzyme immunoassay for differential diagnosis of follicular cyst, luteal cyst, and cystic corpus luteum in cows

In 160 cows with ovarian cysts as determined by rectal palpation, differentiation was made of follicular cyst, luteal cyst, and cystic corpus luteum on the basis of milk progesterone concentrations estimated by an enzyme immunoassay before and at 10 days after cows were treated with gonadotropin-releasing hormone. Cows having a progesterone concentration in skim milk less than 1.0 ng/ml were considered to have follicular cysts and those with concentrations of 1.0 ng/ml or higher were regarded as the cases of luteal cyst or cystic corpus luteum. Luteal cyst was characterized by progesterone values remaining high in the cows for 10 days after treatment, and cystic corpus luteum was characterized by a decrease in progesterone concentration after cows were treated. By the rectal palpation procedure it was impossible to differentiate luteal cyst and cystic corpus luteum from follicular cyst. The frequencies of follicular cyst, luteal cyst, and cystic corpus luteum were 65%, 19%, and 16%, respectively. Of 104 cows with follicular cysts as defined by milk progesterone assay result, 73 (70%) responded to the treatment with gonadotropin-releasing hormone, the milk progesterone concentration increasing from 0.7 +/- 0.2 ng/ml (mean +/- SD) to 1.8 +/- 1.1 ng/ml. The accuracy of rectal palpation 10 days after treatment for judgment of luteinization of follicular cyst confirmed by milk progesterone analysis was only 30% (48 cows of 160).     

Effect of trenbolone acetate on ovarian function in culled dairy cows

The ovarian cycles of 48 culled dairy cows were monitored by assaying plasma progesterone concentrations. Twenty-four cows received a subcutaneous implant of 300 mg trenbolone acetate (Finaplix; Hoechst) at the beginning of the study. Of the implanted cows, two were pregnant, six continued to cycle although their peak progesterone concentrations were significantly lower than in control cows (5.65 +/- 0.71 compared with 8.19 +/- 0.47 ng/ml; P less than 0.01). Prolonged periods (13 to 92 days) of low progesterone concentrations (less than 1 ng/ml) occurred in 12 of the implanted cows. In six of seven cows in which normal cycles had not resumed by the time of slaughter two to five ovarian follicles of diameter greater than or equal to 10 mm were found post mortem. Persistent luteal function (greater than 35 days) occurred in the absence of pregnancy or gross uterine pathology in five of the implanted cows, two of which had recovered spontaneously by the time they were slaughtered. There was no difference in plasma luteinising hormone concentrations between the implanted and control cows. It is concluded that trenbolone acetate affected the ovarian cycle of the cows in several ways through changes other than the modification of tonic luteinising hormone secretion.     

Effect of large palpable ovarian follicles on response to prostaglandin administration in dairy cows with corpora lutea

We examined the response to exogenous prostaglandin F2α in cattle with or without palpable structures believed to be ovarian follicles. All animals had ovarian structures diagnosed by palpation as corpora lutea. The cows were placed into two groups: those with follicles which were estimated by the palpators to be ≤13 mm diameter (n=60); and cows with no palpable follicles or with follicles <13 mm diameter (n=133). Comparisons of proportion in estrus within five days, days to estrus, and milk progesterone levels failed to show significant differences between the groups.     

Milk Progesterone Profile at and after Artificial Insemination in Repeat-Breeding Cows: Effects on Conception Rate and Embryonic Death

The aim of this study was to investigate whether the skim milk progesterone concentrations at artificial insemination (AI) and day of rise of post-ovulatory progesterone concentration thereafter affect the conception and embryonic death rates in repeat-breeding cows. Milk samples were obtained from 96 repeat-breeding cows that failed to conceive to three or more AIs. The samples were taken from the cows at the day of AI and three times/week until day 45 post-AI. Skim milk was obtained after centrifugation and used for progesterone assay. The cows with a progesterone concentration more than 0.5 ng/ml at AI showed a significantly higher incidence of late embryonic death than those having a progesterone concentration<0.5 ng/ml at AI (p<0.01). As the progesterone level at insemination rose, conception rate declined. A negative correlation was shown between conception rate and skim milk progesterone level at AI. Of 56 cows showing a rise of progesterone to 1 ng/ml or more within 6 days after AI, 28 cows (50%) conceived. On the contrary, only eight of 39 cows (20.5%) conceived when the progesterone rose up to 1 ng/ml after day 6 post-AI. We concluded that increased progesterone concentration at the time of AI and delayed rise of progesterone post-AI might lead to decrease in fertility in repeat-breeding cows.     

Reproductive performance of Holstein cows administered GnRH analog HOE 766 (Buserelin) 26 to 34 days postpartum

During the fourth week postpartum, 443 healthy Holstein cows milked thrice daily were randomly divided among four groups to receive 0, 2, 8 and 32 micrograms of the GnRH analog HOE 766. Intervals from calving to first estrus and to first breeding, from breeding to conception and conception rates at first breeding were calculated to measure treatment response, and progesterone was measured in the fat-free portion of milk samples collected twice weekly during the first 4 wk following treatment. Uterine involution at the time of treatment was estimated by palpation per rectum. Twenty percent of the cows examined were classified as having delayed uterine involution (abnormal). By analyzing milk progesterone patterns it was determined that 38% of the animals were in the luteal phase of an estrous cycle when treated. Cows without luteal tissue (less than 1 ng of progesterone/ml milk) given 8 or 32 micrograms of HOE 766 increased in progesterone to greater than or equal to 1 ng/ml within 7 d in 77 and 72% of the cows compared with 40 and 57% for cows receiving 0 and 2 micrograms (P less than .05). This increase in progesterone was followed by a normal estrous cycle within 4 wk in a higher proportion of cows treated with the two higher doses of GnRH analog (87 and 86%) compared with 67 and 70% of those receiving 0 or 2 micrograms of the analog (P less than .005). There were no treatment differences (P greater than .05) for other traits analyzed, but cows with a normal progesterone cycle were observed in estrus and were bred sooner (P less than .01) than those with irregular progesterone patterns. It was concluded that the GnRH analog hastened the onset of normal ovarian cycles in cows milked thrice daily.     

A routine 20-22 days post-service milk progesterone monitoring in dairy cows. Economic evaluation

Three hundred and sixty inseminated Holstein cows were monitored in a controlled trial for low milk progesterone concentration 21-23 days post-breeding. Information about low progesterone cows was given to herdsmen for the experimental group only. Of the cows in the experimental group with milk progesterone of less than or equal to 4.5 ng/ml, 56.0% were inseminated within 2 days of monitoring compared to 28.8% of the control animals. Of the cows reaching the 42-day rectal pregnancy diagnosis, 13.7% and 43.6% were negative for the experimental and the control groups respectively. Inter-service intervals were 34.5 +/- 14.5 days and 44.3 +/- 17.7 days for the experimental and control groups respectively. Pregnancy rates were the same for 264 cows served on routine progesterone monitoring and for 318 cows bred on behavioural oestrus when matched to farm and day of breeding. A gain of US $32.5 (an equivalent of 85 l milk) per lactation for a cow in the monitored herd was established using the data in a model of a 250-cow herd with a total pregnancy goal of 82.4%.     

Involvement of Plasma Progesterone, Oestradiol-17β and Cortisol in Ovulatory Response to Gonadotropin-releasing Hormone in Dairy Cows with Cystic Follicles

The aim of the present study was to examine the plasma concentrations of progesterone, oestradiol-17beta and cortisol in the cows with cystic follicle and to examine its relationship with the ovulatory response to gonadotropin-releasing hormone (GnRH). Eighty-five post-partum Holstein-Friesian cows with cystic follicles regardless of the presence of corpus luteum were studied. Follicular size, presence of corpus luteum and occurrence of ovulation were checked by palpation per rectum. Blood collection and palpation per rectum were conducted on days 0, 7 and 14. Gonadotropin-releasing hormone was administered at day 7. Plasma concentrations of progesterone, oestradiol-17beta and cortisol were determined. Progesterone concentrations of <3.2, 3.2-4.8 and >4.8 nmol/l were defined as low, intermediate and high, respectively. Sixty-three (74.1%) of 85 cows showed low (<3.2 nmol/l =1 ng/ml) progesterone concentrations on day 0. Only 40 (47.1%) of them showed low-low pattern of progesterone at days 0 and 7. In 27 (31.8%) of them, progesterone concentration had increased by day 14. Of 22 cows having high progesterone concentration (>/=4.8 nmol/l) on day 0, corpus luteum was not detected in 18 cows (21.2%). Only in 10 cows, cystic follicle disappeared after GnRH administration. However, only one of 27 cows in which progesterone pattern was low-low-high at days 0, 7 and 14 experienced ovulation of the cystic follicle. Significantly lower oestradiol-17beta concentration was found on day 7 in cows showing a low-low-low pattern than a low-low-high pattern of progesterone (43.0 +/- 4.6 vs 55.8 +/- 2.8 pmol/l, p < 0.05). There was no significant difference in cortisol concentration on any days (days 0, 7 and 14) between cows showing a low-low-low and low-low-high pattern of progesterone. These results suggest that approximately one-fifth of cows diagnosed to have ovarian cysts possess luteal cysts and that a high oestradiol-17beta concentration at the time of GnRH administration is involved in the subsequent ovulation of the follicle, although ovulated follicle may not be cystic.     

The ovarian response and fertility in cows with acidosis induced by acetic acid]

The effects of acetic acid administered at an amount of 300 to 600 g (5 to 10 mol) to the rumen of breeding cows, were investigated on ovulation, conception and progesterone levels in the blood and milk of cows with cloprostenol-induced (Oestrophan Spofa) oestrus at a dose of 500 micrograms i.m. In the group of 15 cows exposed to the acetic acid load five cows got in calf after the first insemination (33.3%), and 12 cows (80.0%) after all inseminations in 37.6 days after cloprostenol administration, with the insemination index 1.67 (Tab. I). In the control group (five cows) four cows (80.0%) got in calf after the first insemination, in total all five breeding cows got in calf in 20.6 days after cloprostenol administration, with the insemination index 1.2. In the experimental group of 15 cows a clinical examination of ovaries on day 7 after insemination revealed ovulation disorders in eight cows, that means in 53.3% of the animals (Tab. II). No ovulation disorders were observed in the control group of five cows. Progesterone levels in the blood showed high variability (Tab. III). In the group of cows administered acetic acid they were by more than a half lower (1.49; 0.67; 1.53 per ml) on days 7, 14 and 21 after insemination in comparison with the control group (3.35; 2.5; 3.38 ng per ml). The average progesterone levels in milk (Tab. IV) were 1.27 and 1.53 on day 7, 6.74 and 7.27 on day 14 and 3.52 and 11.85 ng per ml on day 21, respectively, the higher values apply to the control. It was not possible to evaluate reliably from the progesterone levels in the blood and milk if ovulation took place and if the corpus luteum was developing (Tab. V and VI). The clinical control of ovaries on days 7 and 8 after oestrus and insemination was more reliable to determine the ovulation disorders than the progesterone determination in the blood and milk of cows.     

奶牛发情期的奶孕酮分析

<正> 影响奶牛人工授精成功率的主要原因是对发情期能否正确判断,适时输精。据1981年联邦德国Bavarian动物健康服务机构的报告,输精时间不正确,是影响奶牛繁殖率的重要因素。由于孕酮含量在发情周期中呈规律性变化,在发情期显著下降,因此可     

Relationship between the first ovulation within three weeks postpartum and subsequent ovarian cycles and fertility in high producing dairy cows

The aim of this study was to investigate the relationship between the first ovulation within 3 weeks postpartum and subsequent ovarian cycles and fertility in high producing dairy cattle in Hokkaido, Japan. In Experiment 1, 110 cows (44 primiparous and 66 multiparous) were used to determine the effects of the first ovulation within 3 weeks postpartum on subsequent ovarian cycles. Milk samples were collected twice weekly from 7 to 100 days postpartum. The first ovulation was identified by an increase in milk progesterone (P4) to more than 1 ng/ml within 3 weeks postpartum. The numbers of cows showing ovulation and anovulation within 3 weeks postpartum were 31 (70.5%) and 13 (29.5%) in the primiparous cows and 35 (53.0%) and 31 (47.0%) in the multiparous cows, respectively. The patterns of ovarian resumption after calving were classified into two types (normal ovarian cycles and abnormal ovarian cycles) on the basis of milk P4 concentrations. Initiation of normal ovarian function in cows ovulated within 3 weeks postpartum occurred earlier than in anovulated cows regardless of the number of calvings (primiparous, 27.8 days vs. 44.4 days; multiparous, 30.6 days vs. 55.7 days; P<0.01). Out of the multiparous cows that ovulated within 3 weeks postpartum, initiation of normal ovarian function followed by a normal luteal phase was earlier than when it was followed by an abnormal luteal phase (25.5 days vs. 40.4 days; P<0.05). Milk P4 concentrations after the first ovulation were lower than those after the second ovulation in both the primiparous and multiparous cows (P<0.05). In Experiment 2, 22 multiparous cows were used to determine the effects of the first ovulation within 3 weeks postpartum on subsequent fertility. Blood samples were collected once a week from 0 to 3 weeks postpartum. The interval from parturition to first service in ovulated cows was shorter than in anovulated cows (68.4 days vs. 94.8 days; P<0.05). The conception rate by 100 days after calving tended to be higher in ovulated cows than in anovulated cows (50.0% vs. 16.7%, P=0.09). In conclusion, our data strongly suggests that ovulation within 3 weeks postpartum is a crucial phenomenon for subsequent resumption of ovarian function and conception, and thus it can be used as an index of subsequent reproductive performance.     

奶牛早孕诊断乳汁孕酮临界值的确定

随机选择健康荷斯坦母牛６３头，其中发情周期牛５头，配后１８－２４天牛３０头和通过直接确定的怀孕牛２８头，按程序采集末乳乳样。用放射免疫测定法（ＲＬＡ）测定乳汁孕酮（ＭＰ４）浓度。以发情第３天ＭＰ４浓度加上２倍标准差为未孕临界值的土限，以配后１８－２４天怀孕牛ＭＰ４浓度的平均值减去１倍标准差为怀孕临界值的下限。结果表明，奶牛ＭＰ４早孕诊断临界值为：≥７．１９ｎｇ／ｍｌ为怀孕，〈４．７２ｎｇ／ｍｌ为未     

Body condition and frequency of ovarian cysts in Brown Swiss cows during the first 40 days of lactation

For this investigation 50 Brown Swiss cows from 21 different farms were used. Twenty-five peripartal overconditioned cows (back fat thickness > 38 mm) were compared with 25 peripartal not overconditioned animals (back fat thickness < 38 mm). On days 20, 30 and 40 post partum the ovaries were examined sonographically and 10, 15, 20, 30 and 40 days after calving plasma concentrations of progesterone and 17-beta estradiol were determined. In peripartal overconditioned animals 12 ovarian cysts were found while only one cyst was present in not overconditioned cows (P < 0.05). At first examination all ovarian cysts were classified by ultrasound as follicle theca cysts (progesterone < 0.5 ng/ml plasma). Follow examinations resulted in 3 cysts which persisted as theca cysts while 8 cysts became luteinized and 2 cysts completely regressed. There was no indication of increased plasma progesterone and/or estradiol concentrations in overconditioned cows with higher fat deposit before of ovarian cysts had occurred.     

Serum progesterone levels in post-partum dairy cows after repeated application of the prostaglandin F2 alpha analogue D (+) cloprostenol sodium

Reproductive management programmes based on strategic use of prostaglandin F2 alpha (PGF2 alpha) to induce and synchronize oestrus in post-partum dairy cows are widespread. Repeated shortening of the oestrous cycle during early lactation in high-yielding dairy cows, however, could impair corpus luteum function and thus decrease fertility. The objective of this study was to analyse the effect of repeated treatments with the prostaglandin F2 alpha analogue D (+) cloprostenol sodium on progesterone concentrations indicative of a functional corpus luteum in post-partum dairy cows. Furthermore, the influence of milk production, parity and endometritis on progesterone concentrations under these circumstances were studied. Eighty-four cows of a commercial dairy operation were treated three to four times with D (+) cloprostenol sodium (Preloban; Hoechst Roussel Vet, Wiesbaden, Germany) at 14-day intervals, starting 22-28 days post-partum. Blood samples were collected prior to treatment 1 (sample 1) and 14 days after treatments 1, 2 and 3 (samples 2-4) and serum progesterone (P4) levels were determined. The percentage of cows with P4 levels < 1 ng/ml decreased from 51% in sample 1 to 23% in samples 3 and 4. More primiparous cows had low P4 levels 14 days after the second treatment than older cows (P < 0.05). Cows with low progesterone levels in sample 3 or 4 had lower protein contents in milk on the second milk test day post-partum and in their cumulative milk yield of the first 100 days of lactation. Clinical endometritis at post-partum examination did not influence progesterone levels after treatment with PGF2 alpha. Repeated application of PGF2 alpha (more than twice) in the post-partum period does not influence serum progesterone levels 14 days after treatment. Failure to develop luteal tissue after treatment contributed to the conception failures after first service.     

Plasma progesterone concentrations in dairy cows with cystic ovaries and clinical responses following treatment with fenprostalene

Sixty-two dairy cows diagnosed as having cystic ovarian degeneration were used to study the correlation between rectal palpation findings and plasma progesterone concentrations and the response of cysts to treatment using fenprostalene, a luteolytic agent. Rectal palpation accurately determined the presence of luteal cysts as confirmed by plasma progesterone concentrations of 3 ng/mL or more. Treatment with fenprostalene was very effective for luteal cysts: a high percentage of treated cows exhibited estrus within seven days after treatment. The conception rate following artifical insemination during the induced estrus was 87.5% (21/24). Rectal palpation was much less accurate for the diagnosis of follicular cysts. Cows diagnosed as having follicular cysts had wide variations in plasma progesterone concentrations. Response to fenprostalene treatment was poor in cows with nonluteinized cystic follicles associated with low progesterone concentrations. However, cows diagnosed as having follicular cysts, but with progesterone concentrations of 1 ng/mL or more, responded better to fenprostalene treatment than cows with low progesterone concentrations.

It was concluded that, if correctly diagnosed, luteal cysts can be successfully treated with fenprostalene, and conception rates following treatment can be expected to be normal.

     

Diagnosis of luteal and follicular ovarian cysts by palpation per rectum and linear-array ultrasonography in dairy cows.

The purpose of this study was to determine and compare the accuracy of palpation per rectum and linear-array ultrasonography for diagnosing follicular vs luteal ovarian cysts in cows. Forty-seven examinations of ovarian cysts from 28 cows were diagnosed by palpation per rectum as either a firm, thick-walled structure (luteal cyst) or a soft, thin-walled structure (follicular cyst) during weekly herd examinations. The ovaries of each cow were then examined by ultrasonography. Ultrasonograms of cysts greater than 25 mm in diameter were diagnosed as luteal or follicular cysts and were recorded on videotape for evaluation by a second clinician. Serum progesterone concentrations at the time of examination were determined by radioimmunoassay and used to classify luteal (greater than 0.5 ng/ml) or follicular (less than or equal to 0.5 ng/ml) cysts. Selection of this discriminatory level was based on response of a proportion of cows with luteal cysts that were given 25 mg of prostaglandin F2 alpha at the time of diagnosis by ultrasonography. Sensitivity and specificity of palpation per rectum for diagnosis of type of ovarian cyst were low (43.3 and 64.7%, respectively). In contrast, sensitivity and specificity of ultrasonography were considerably higher (86.7 and 82.3%, respectively). Agreement between the 2 methods of diagnosis was 57.4%. Overall agreement between the 2 clinicians' diagnoses by ultrasonography was 85.1%. On the basis of our findings, we confirm that luteal and follicular cysts cannot be accurately differentiated by palpation per rectum alone. These data suggest that linear-array ultrasonography is more effective than palpation per rectum for diagnosing type of ovarian cyst in cows.     

Relationships between the plasma concentrations of insulin-like growth factor-I in dairy cows and their fertility and milk yield

The relationships between insulin-like growth factor-I (IGF-I) and the fertility and milk yield of Holstein-Friesian dairy cows were investigated. The concentration of IGF-I in blood was measured weekly from one week before to 12 weeks after calving in 177 multiparous cows and at four times during this period in 142 primiparous cows; the concentration of IGF-I in milk was measured in 50 of the multiparous cows. The plasma concentrations of IGF-I were higher in the primiparous than in the multiparous animals. In the primiparous cows, high concentrations of IGF-I before calving were associated with longer calving to conception intervals. Conversely, in the multiparous cows low concentrations of IGF-I before and after calving were associated with a failure to conceive, despite repeated services. Multiparous cows with IGF-I concentrations of greater than 25 ng/ml in the week after calving were 11 times more likely to conceive to first service than those with lower concentrations. Concentrations of IGF-I greater than 50 ng/ml at first service increased the likelihood of conception five-fold. Cows with higher peak milk yields had lower plasma concentrations of IGF-I and took longer to return to ovarian cyclicity. The negative relationship between milk yield and return to cyclicity was stronger in the multiparous cows (P < 0.002) than in the primiparous cows (P < 0.04). The concentrations of IGF-I in milk followed a different pattern and were not associated with the changes in plasma IGF-I or fertility.     

Comparison of different methods of diagnosis of cystic ovarian disease in cattle and an assessment of its treatment with a progesterone-releasing intravaginal device

The aims of this study were to assess the accuracy of different common methods of differentiating between follicular and luteal ovarian cysts, and to monitor the response of the cysts to 12 days treatment with a progesterone-releasing intravaginal device (PRID). On the basis of agreement between the different methods, 25 of the 46 cases examined were diagnosed as follicular and 14 as luteal cysts; for the other seven cases the methods disagreed. The use of ultrasound was more accurate in diagnosing follicular cysts than luteal cysts, and combined with plasma progesterone concentrations gave the most accurate assessment of cyst type (92 per cent for follicular cysts and 82 per cent for luteal cysts). The mean (se) plasma progesterone concentration was lower in the cows with follicular cysts than in those with luteal cysts (0.29 [0.05] v 3.90 [0.63] ng/ml; P<0.05). Luteal cysts had thicker walls (5.3 [0.04] v 2.5 [0.2] mm; P<0.0001), and the wall thickness of all the cysts was positively correlated with plasma progesterone concentration (r=0.52, P<0.0004). Cows with luteal cysts had more additional follicles greater than 5 mm in diameter (P<0.01). In cows with follicular cysts and other follicles greater than 5 mm in diameter, the mean oestradiol concentration was 7.9 (1.8) pg/ml compared with 24.2 (3.1) pg/ml (P=0.002) in cows without other follicles greater than 5 mm in diameter on either ovary. At the time of PRID removal, plasma progesterone concentration had increased in the cows with follicular cysts to 1.59 (0.06) ng/ml (P<0.05) and decreased in the cows with luteal cysts to 0.87 (0.01) ng/ml (P<0.05), although there was no change in original cyst structure in 45 per cent of the cases. However, new ovarian structures were frequently observed during the treatment. The overall pregnancy rate for cows with both types of cyst after treatment was 50 per cent after three inseminations, but the first service pregnancy rate was only 18 per cent for cows with follicular cysts and 28 per cent for cows with luteal cysts. After treatment, the fertility of cows with follicular cysts was similar to that of paired herdmates, whereas cows with luteal cysts took 40 days longer to calve again than healthy herdmates. However, the culling rate was higher for cows with follicular cysts (41 v 11 per cent).     

Effect of strategic feed supplementation on productive and reproductive performance in yak cows

A total of 2230 yak cows (5-13 years of age) in two populations with different milking systems were investigated. One population had a system of milking once a day (MOD), and the other population twice a day (MTD). The average milk yield of MOD cows was 0.7 +/- 0.2 kg/day within a milking period of 109 +/- 9 days. This compared with an average of 1.24 +/- 0.3 kg/day in 127 +/- 6 days in MTD yaks (p < 0.01). The cows showed a calving rate of 71% under the MOD system and 51.4% under the MTD system. Three farms with a total of 104 MTD cows between six and 12 years of age were used to provide three different feeding groups. The groups were fed with, or without oat hay or highland barley straw in amounts of 1-1.5 kg/head/day from December to April. The three farms were designated as Farm I, Farm II, and Farm III. Farm I had 41 cows with body weight of 230 +/- 67 kg each for grazing with no supplement (GNS). Farm II had 30 animals with body weight of 216 +/- 28 kg each for grazing + oat hay (GOH). Farm III had 33 animals body weight of 221 +/- 34 kg each for grazing + highland barely straw (GBS). The calving rates of the cows in GOH and GBS were 23 and 19% higher, respectively, than GNS cows (p < 0.01), and the highest rate reached 76.7% in GOH. The live weight loss of the cows in GNS was considerably higher (p < 0.01) than in the two other groups. Ten GOH cows and 12 GNS cows were used to collect milk samples for measuring the progesterone concentration using RIA kits provided by IAEA/FAO: Milk was sampled every five days from calving until 90 days postpartum. In the unsupplemented group, milk progesterone (P4) levels suggested that cows had started cyclic ovarian activity by 40 days postpartum, whereas only 25% had been observed in estrus. In the supplemented group, 80% of cows had started cyclic ovarian activity by the same time and 70% had been seen in estrus. Two types of cyclic activity in terms of progesterone changed were found. With Type I (normal), 50 and 80% of cows from GNS and GOH, respectively, had cyclic changes of P4 in milk at 40 days postpartum. With Type II, the P4 levels in the milk remained 0.89 ng/ml until 90 days postpartum. A total of 46 grazing cows between five and 13 years of age (body weight 214 +/- 68 kg) was used to collect blood samples to measure concentrations of nutrient of metabolites at two weeks pre-calving and at two weeks, two months and four months postcalving, respectively. The concentrations of nutrient metabolites [albumin, globulin, urea, beta-hydroxybutyrate (BHB) and inorganic phosphorus] suggested general underfeeding of energy and protein in the winter/late pregnancy period with some recovery in lactation. Energy constraints appeared again as the summer progressed. No dietary phosphate deficiency was found. BHB and albumin testing on serum yaks could be a useful tool to identify poor nutritional status during the winter and so illustrate the need for supplementation.     

Changes in plasma metabolic hormone concentrations during the ovarian cycles of Japanese black and holstein cattle

The aim of the present study was to investigate the changing profiles of plasma metabolic hormones during the ovarian cycles of beef and dairy cattle. We used 16 non-pregnant, non-lactating Japanese Black beef cattle (6 heifers and 10 cows; parity=2.3 +/- 0.8) and 12 multiparous Holstein dairy cows (parity=3.0 +/- 0.3). Blood samples for hormonal analysis (growth hormone, GH; insulin-like growth factor-I, IGF-1; insulin; and progesterone, P4) were obtained twice weekly for 40 days before artificial insemination for Japanese Black cattle and from 50 to 100 days postpartum for Holstein cows. Luteal phases were considered normal if the P4 concentrations for at least 3 time points over the course of 7 days remained above 1 ng/ml and at least 2 of the time points were above 2 ng/ml. The patterns of the ovarian cycles were classified into two types (normal or abnormal, such as having prolonged luteal phase and cessation of cyclicity) on the basis of the plasma P4 profiles. The plasma concentrations of IGF-1 in both breeds increased transiently during the preovulatory period when the P4 levels were low and decreased to lower levels during the luteal phase when the P4 levels were high. The plasma concentrations of insulin in the 3(rd) week of normal ovarian cycles when the plasma P4 concentration dropped to less than 1 ng/ml were higher than those at other time points in the Japanese Black cattle, but not in the Holstein cows. The plasma concentrations of GH did not change during the ovarian cycle in either breed. In conclusion, the present study indicates that the plasma IGF-1 concentration increases during the follicular phase (low P4 levels) and decreases during the luteal phase (high P4 levels) in non-lactating Japanese Black and lactating Holstein cattle. The results suggest that ovarian steroids, rather than nutrient status, may be related to the cyclic changes in IGF-1 secretion from the liver in cattle.