Postpartum Ovarian Cyclicity Research Articles

Field Trial on Progesterone Cycles, Metabolic Profiles, Body Condition Score and their Relation to Fertility in Estonian Holstein Dairy Cows

Resumption of luteal activity postpartum and fertility were investigated in an Estonian Holstein high milk production and good fertility dairy herd. Body condition was scored after every 10 days in 54 multiparous dairy cows (71 lactations) calving inside from December to March during 4-year period. Blood samples were taken 1-14 days before calving and 1-14, 28-42 and 63-77 days after calving: analytes estimated were serum aspartate aminotransferase (AST), glucose, ketone bodies, total cholesterol, non-esterified fatty acids and triglycerides. The general linear mixed model was used to compare the data for cows with different characteristics in luteal activity postpartum based on their milk progesterone profiles. Forty-five per cent of cases had abnormal profiles; delayed resumption of ovarian cyclicity postpartum (DC) was the most prevalent abnormality. There was no difference in body condition scores between the groups. The DC and prolonged luteal phase groups had higher serum AST activity (p < 0.01) 1-14 days postpartum compared with normal group. The DC group also had higher cholesterol and triglyceride values (p < 0.05) 28-42 days postpartum and higher milk fat/protein ratio (p < 0.01) on the first month of lactation compared with normal profile group. Despite long post-calving anoestrous period (71 +/- 5.0 days; mean +/- SEM) DC group had 64.7% first service pregnancy rate (normal group 48.6% and PLP group 37.5%). This study did not find any detrimental effect of prolonged anovulatory period postpartum on subsequent fertility.

Whole sunflower seeds as a source of polyunsaturated fatty acids for grazing dairy cows: Effects on metabolic profiles and resumption of postpartum ovarian cyclicity

Intake of polyunsaturated fatty acids (PUFA) could modify follicular dynamics and reduce the length of the interval from calving to first ovulation (ICOV) in dairy cows, associated with changes in metabolites (i.e. cholesterol) or hormones (i.e. IGF-I). To test this hypothesis, 48 cows were stratified in two groups (primiparous or multiparous) and within each group were randomly assigned to three treatments to begin at calving: 0 kg (SS0), 0.7 kg (SS0.7) and 1.4 kg (SS1.4) of whole sunflower seeds (WSS) per cow per day. The experimental period lasted for 60 days after calving and the diets, which consisted of direct grazing of improved pastures, whole-plant wheat silage and concentrates, were designed to be isocaloric and isoproteic (1.6 Mcal NEL/kg DM, 16.7% CP). Ovaries were examined by ultrasound three times per week from day 8 postpartum (PP) until first PP ovulation. Body condition score (BCS) was determined and blood samples were collected weekly from calving to characterize the metabolic profiles. In treatments SS0.7 and SS1.4, 7/8 and 6/8 primiparous cows ovulated the first follicular wave PP, compared with only 1/8 primiparous cow in treatment SS0, while there were no treatment differences in multiparous cows. The ICOV was 44, 21 and 19 days for the primiparous, and 22, 21 and 25 days for the multiparous cows, in treatments SS0, SS0.7 and SS1.4, respectively. Treatments had no effect on BCS, plasma IGF-I and metabolic profiles except that NEFA and urea were increased by WSS supplementation. Intake of PUFA (WSS up to 1.4 kg/day or 6.7% of the diet) during early lactation reduced the ICOV in primiparous grazing dairy cows in early lactation but not in multiparous cows, and while the precise mechanism for these results is unclear, it was not related to changes in the plasma concentrations of IGF-I or cholesterol.

Ovarian Cyclicity and Reproductive Performance of Holstein Cows Carrying the Mutation of Complex Vertebral Malformation in Japan

This study was carried out on 71 lactating Holstein Friesian cows to investigate the resumption of ovarian cyclicity postpartum and the reproductive performance in cows carrying the mutation of complex vertebral malformation (CVM) compared with control ones. The cows were distributed in two dairy farms in Hiroshima Prefecture, Western Japan. Blood samples were collected from the cows to detect carrier cows with CVM mutation. Furthermore, plasma samples were collected weekly after calving from control cows (n = 10) and CVM carrier cows (n = 10), until 10 weeks postpartum to investigate the day of first ovulation and the resumption of ovarian cyclicity postpartum. The reproductive parameters were investigated and compared with control and CVM carrier cows. Thirty-six cows were diagnosed to be CVM carriers by DNA examination and confirmed later by DNA sequencing. The pedigree analysis of the carrier cows revealed that they were daughters of six types of CVM carrier semen that still was used in dairy farms in Western Japan. In terms of reproductive indices, there were no significant differences between the control and the CVM carrier cows on the day of the first ovulation postpartum and the interval from calving to first insemination. However, CVM carrier cows significantly required more inseminations per conception and showed a significantly longer period to conception and subsequent calving than control ones. In conclusion, the reproductive performance of the CVM carrier cows was lowered through conception failure that might indicate the occurrence of intra-uterine mortality in those cows.

Radioimmunoassay of milk progesterone as a tool for fertility control in smallholder dairy farms

This study focused on the use of radioimmunoassay of progesterone in milk for the diagnosis of post-partum ovarian cyclicity and accurate detection of oestrus and non-pregnancy in cows in the artificial insemination (AI) programme in Bangladesh. In Investigation 1, milk samples were collected on day 0 (day of AI), day 9-13 and day 21-24 from 444 milking cows of various breeds presented for the first postpartum insemination by 413 farmers living at 182 villages/regions in Mymensingh District from 6 AI centres and sub-centres. Each cow was then examined three times after each AI until it stopped returning to oestrus. Sixty to 90 days after the last AI, the cows were examined per rectum to confirm the pregnancy. Milk progesterone data on day 21-24 contributed to a clear diagnosis with respect to non-pregnancy in 100% cows, indicating a possible use of this progesterone assay for identifying non-pregnant cows in AI programmes. In Investigation 2, milk progesterone was monitored two times in a month with a 10-day interval in 88 cows. The samples were taken between 10 days after calving and the first detected oestrus, followed by two more samples 10 days apart. The proportion of cows accurately detected in oestrus was 30%. Another 30% were stated to be in oestrus when they were not (false positive) and 40% were not detected when they were in oestrus (false negative). The mean intervals between calving and oestrus and between calving luteal activity were 40 to 362 days (median=120, n=82) and 34 to 398 (median=111, n=64) days, respectively. The body condition scores at calving and at the initiation of luteal activity influenced the interval between calving and luteal activity (p < 0.05). Cows suckled twice daily initiated luteal activity earlier than their counterparts suckled several times daily (p < 0.05). Determination of progesterone in milk on day 21-24 is a good means for detecting non-pregnant cows.

Prostaglandins and reproduction in female farm animals

Prostaglandins impact on ovarian, uterine, placental, and pituitary function to regulate reproduction in female livestock. They play important roles in ovulation, luteal function, maternal recognition of pregnancy, implantation, maintenance of gestation, microbial-induced abortion, parturition, postpartum uterine and ovarian infections, and resumption of postpartum ovarian cyclicity. Prostaglandins have both positive and negative effects on reproduction; they are used to synchronize oestrus, terminate pseudopregnancy in mares, induce parturition, and treat retained placenta, luteinized cysts, pyometra, and chronic endometritis. Improved therapeutic uses for prostaglandins will be developed when we understand better their involvement in implantation, maintenance of luteal function, and establishment and maintenance of pregnancy.

Relationships between body condition score, body weight, and some nutritional parameters in plasma and resumption of ovarian cyclicity postpartum during pre-service period in high-producing dairy cows in a subtropical region in Japan

The objective of this study was to investigate the relationships among body condition score (BCS), body weight and plasma metabolite concentrations, and resumption of ovarian cycles postpartum in high-producing dairy cows in a subtropical region in Japan. The study was conducted between May 2001 and January 2003 in a commercial dairy farm in Hiroshima. Cows were kept in free-stall barns with sawdust and wood shavings for bedding, and fed a total mixed ration consisting of alfalfa, timothy and oat hay, corn, tofu ground-wet, beet pulp, cottonseed and soybean. Milk samples were collected twice weekly from 2 to 11 weeks postpartum, and progesterone concentrations in skim milk were determined by ELISA. At 8 and 2 weeks before calving and 3, 5, 7, 9, and 11 weeks after calving, both BCS and body weights were determined and blood samples were collected to determine plasma concentrations of total cholesterol (T-cholesterol), non-esterified fatty acids (NEFA), total protein, and urea nitrogen. The average 305 days milk yield was 10,422 kg. Out of 110 cows, 44.5% had normal resumption (ovulation occurred ≤45 days after calving, followed by regular ovarian cycles), 33.6% had a prolonged luteal phase (luteal activity >20 days), 12.7% had delayed first ovulation (no ovulation until ≤45 days after calving), 4.6% had a short luteal phase (luteal activity <10 days, except in the first cycle), and the remaining 4.6% had cessation of cyclicity (no luteal activity ≥14 days between cycles). The BCS of cows with delayed first ovulation were lower than the BCS of cows with normal resumption and prolonged luteal phase at 5 weeks (2.9 ± 0.1 versus 3.1 ± 0.1 and 3.2 ± 0.1; P < 0.05), 7 weeks (2.8 ± 0.1 versus 3.1 ± 0.1 and 3.2 ± 0.1; P < 0.01), 9 weeks (2.7 ± 0.1 versus 3.0 ± 0.1 and 3.2 ± 0.1; P < 0.01) and 11 weeks (2.6 ± 0.1 versus 3.0 ± 0.1 and 3.2 ± 0.1; P < 0.01) after calving. None of the plasma parameters differed ( P > 0.05) among different groups of cows. Cows loosing ≥1 unit BCS after calving had a prolonged interval to commencement of luteal activity, and were at greater risk of having delayed first ovulation. Poor postpartum nutritional status was associated with delayed first ovulation postpartum. Regular monitoring of BCS before and after calving would be useful in nutritional management, and help in preventing delayed first ovulation in high-producing dairy cows.

Development of Ovulation Synchronization and Fixed Time Artificial Insemination in Dairy Cows

Recently, reproductive management has become more difficult as a result of increased herd size. Problems with missing estrous signs and decrease in conception rate by artificial insemination (AI) performed at wrong timing have caused low AI conception rates. In 1995, ovulation synchronization and fixed-time AI (Ovsynch/TAI) was developed in the USA as a new reproductive technology, which was accepted as an useful reproductive management tool in many countries. However, no information on the use of Ovsynch/TAI was available in Japan. It was, therefore, warranted to show the ovulation rate and conception rate after Ovsynch/TAI using gonadotropin releasing hormone analogue (GnRH-A, fertirelin acetate) and prostaglandin F2alpha (PGF2alpha)-THAM, both were commercially available in this country. The conception rate after Ovsynch/TAI has been known to vary among different herds and individuals. Investigation and analysis of factors affecting the conception rate was also warranted to improve the conception rate. A series of experiments were carried out to establish Ovsynch/TAI using domestically produced GnRH-A and PGF2alpha and to study factors affecting conception rate after Ovsynch protocol. Ovsynch using 100 microg GnRH-A and 25 mg PGF2alpha were observed using ultrasonography. As a result, a high synchronization rate of ovulation at 16 to 20 h after the second GnRH injection was confirmed. The conception rate after Ovsynch/TAI was compared in 87 cows with the conception rate after AI at estrus induced by PGF2alpha (139 cows). Conception rate after Ovsynch/TAI was higher than the figure after AI at induced estrus (59.1% vs 20.9%, P<0.05). The dose of GnRH-A was also studied and a practical dose of GnRH-A was found to be 50 microg per cow. To clarify some factors affecting the conception rate after Ovsynch/TAI, 1,558 cows were investigated for the state of their ovaries, days after calving, parity, season, ovarian cyclicity postpartum and nutritional state at the day of Ovsynch. The overall conception rate after Ovsynch/TAI was 51.5%. Fifty-six cows (3.6%) showed estrus at 6 to 7 d after the first injection of GnRH-A. The conception rate after Ovsynch/TAI was low in cows that were 40 to 60 d postpartum, those in their 5th lactation or more, those bred in July to August, and those recovering ovarian cyclicity later than 56 d postpartum. The conception rate after Ovsynch/TAI was high in cows in which body condition score (BCS) was 3.75 at dry period and 3.0 at the day of Ovsynch. In conclusion, Ovsynch/TAI is an effective tool for the reproductive management of dairy cows. A steady and sufficient conception rate after Ovsynch/TAI could be expected by taking the factors affecting the conception rate into the consideration.

The Acyclic Period Postpartum in Automatic and Conventional Milking

The acyclic postpartum period in cows is prolonged due to frequent suckling when compared with twice daily milking. In conventional milking systems twice daily milking is common, while in automatic milking systems (AMS) three or more milkings are performed in early lactation. In this study, the hypothesis was tested that an increased milking frequency in AMS causes a delay in resumption of ovarian cyclicity postpartum and increases days open in German Fleckvieh cows (n = 124). Calvings were equally distributed throughout the 1-year experimental period. All cows were housed in one barn. Sixty-three cows were milked in an AMS (AC) and 61 cows were twice daily milked in a conventional milking parlour (PC). Forty-two AC and 36 PC remained in the herd until conception. After parturition, milk samples were analysed for progesterone twice weekly to record the ovarian activity until pregnancy was diagnosed. The first and the second ovulation were determined by the progesterone profile of each individual cow. The mean milking frequency during the first 3 weeks after parturition was higher in AC (3.17 +/- 0.09 milkings/day) than in PC (milked twice daily). The individual mean milking frequency of AC for the first 3 weeks of lactation ranged from 2.0 to 5.9 daily milkings. The time span from parturition until the first and second ovulation did not differ between AC and PC. However, first ovulation was observed earlier in primiparous (23 +/- 1 days) than in multiparous cows (29 +/- 1 days, P < 0.05). Within AC no relationship between milking frequency and duration of the acyclic period was observed. Days open did not significantly differ between AC and PC and between primiparous and multiparous cows. In conclusion, the increased milking frequency in AMS did neither cause a delay in resumption of ovarian cyclicity postpartum nor did it increase days open.

Effects of abnormal ovarian cycles during pre-service period postpartum on subsequent reproductive performance of high-producing Holstein cows

The primary objective of this study was to investigate the effects of abnormal ovarian cycles during the pre-service postpartum period on subsequent reproductive performance of high-producing Holstein cows. The study was conducted in a commercial dairy farm with approximately 150 lactating cows, in a subtropical region of Japan. Animals were kept in free-stall barn, and fed a total mixed ration. Cows that calved from June 2001 to July 2002 were included in the study. Milk samples were collected twice weekly from 2 to 11 weeks postpartum, and progesterone concentrations in skim milk were determined by ELISA. After a voluntary waiting period of 40 days, cows detected in estrus were bred by artificial insemination (AI). Pregnancy was confirmed by palpation per rectum 40–70 days after AI. Out of a total of 91 cases, 39 (42.9%) had normal ovarian cycles (ovulation within 45 days after calving, followed by normal ovarian cycles), 32 (35.2%) had prolonged luteal phase (i.e. luteal activity for >20 days), and 12 (13.2%) had anovulation or delayed first ovulation (i.e. first ovulation did not occur until >45 days after calving). The remaining (8.8%) had other types of abnormalities. When compared with cows with a normal ovarian cycle, prolonged luteal phase cows had a lower 100 days AI submission rate, conception rate and pregnancy rate (84.2% versus 56.3%; P<0.05, 50% versus 16.7%; P<0.05 and 42.1% versus 9.4%; P<0.01, respectively), and longer intervals to first AI and to conception (67±6 days versus 98±7 days and 95±9 days versus 136±11 days; P<0.01 for each). Similarly, when compared with cows with normal ovarian cycles, those with anovulation had lower 100 days conception rate and pregnancy rate (50% versus 0%; P<0.05 and 42.1% versus 0%; P<0.01, respectively), and longer intervals to first AI and to conception (67±6 days versus 93±12 days; P<0.05 and 95±9 days versus 155±14 days; P<0.01, respectively). Survival analysis of the data for calving to conception interval showed that cows with prolonged luteal phase or anovulation were getting pregnant at a slower rate, and took longer to get pregnant than the cows with normal resumption of ovarian cyclicity postpartum. In conclusion, abnormal ovarian cycles during the pre-service period postpartum adversely affected reproductive performance, including AI submission rate, pregnancy rate, interval to first AI, and calving to conception interval in high-producing Holstein cows.

Resumption of postpartum ovarian cyclicity in high-producing Holstein cows

The objective of this study was to investigate the resumption of ovarian cyclicity postpartum in high-producing dairy cows in commercial dairy farms under subtropical conditions. The cows were kept in a free-stall or tie-stall barn. Milk samples were collected from cows twice weekly, and progesterone in the skim milk was assayed by double-antibody ELISA. Cows were examined rectally and vaginoscopically at 2-week intervals after calving. Body condition score (BCS) and body weights were taken before and after calving. A cow was considered to have resumed ovarian cyclicity on the day of ovulation if followed by regular ovarian cycles. Thirty seven percent ( n=20/54) of the cows had normal resumption of ovarian cyclicity (resumption within 45 days after calving), and 63% ( n=34/54) had delayed resumption (resumption did not occur until >45 days after calving). Delayed resumption Type I (one or more ovarian cycles with luteal phase >20 days, i.e. prolonged luteal phase; 31.5%) and delayed resumption Type II (first ovulation did not occur until ≥45 days after calving, i.e. delayed first ovulation; 24.1%) were the most common types of delayed resumptions. Almost half (46.3%) of the cows did not resume their ovarian cyclicity until >65 days postpartum. Cows with delayed resumption Type I had a higher incidence of abnormal cervico-vaginal discharge (64.7%) and incomplete uterine involution (94.1%) compared to cows with normal resumption ( P<0.01). The BCS of cows with delayed resumption Type II were lower than those of normal resumption cows at 5 weeks and later in the postpartum period ( P<0.05). Approximately two-thirds of high-producing cows had delayed resumption of ovarian cyclicity postpartum. Prolonged luteal phase and delayed first ovulation were two important ovarian dysfunctions that delayed postpartum resumption of cyclicity in high-producing dairy cows.

Effects of body condition score in cows peripartum on the onset of postpartum ovarian cyclicity and conception rates after ovulation synchronization/fixed-time artificial insemination.

The aim of this study was to examine whether the nutritional state of cows peripartum was associated with the recovery of ovarian function and conception rates after synchronization of ovulation and fixed-time artificial insemination (OVSYNCH/TAI). The effect of the interval in days from calving to the first ovulation on conception rates after OVSYNCH/TAI was also investigated. Conception rates of cows after OVSYNCH/TAI (n=39) were 43.6%. The conception rates of cows with a body condition score (BCS) of 2.75-3.25 at 30 d postpartum and on the day of OVSYNCH treatment were significantly higher than in cows with a BCS < or =2.5 (P<0.05). The percentage of cows establishing ovarian cyclicity before 55 d postpartum in cows with a BCS of 2.75-3.25 at 30 d postpartum and on the day of OVSYNCH treatment were significantly higher than in cows with a BCS < or =2.5 (P<0.05). The conception rates after OVSYNCH/TAI in cows which recovered ovarian cyclicity within 34 d postpartum were significantly higher than in cows with first ovulation > or =56 d (P<0.05). These results indicated that the nutritional state in cows peripartum influenced the conception rates after OVSYNCH/TAI and the postpartum ovarian cyclicity and also suggested that the conception rates after OVSYNCH/TAI decreased in cows with delayed recovery of ovarian cyclicity.

Postpartum Reproductive Function: Association with Energy, Metabolic and Endocrine Status in High Yielding Dairy Cows

The effect of energetic, metabolic and endocrine status upon onset of ovarian cyclicity as well as time empty and conception at first service was assessed in 90 multiparous Holstein cows (mean 9'500 kg energy-corrected milk/305 d) in a research farm in Switzerland. Dry matter intake, milk yield and body weight were measured daily from week 2 antepartum (a.p.) through wk 20 postpartum (p.p.). Milk composition was determined 4 times/wk and milk acetone was measured weekly. Blood samples for the determination of glucose, non-esterified fatty acids (NEFA), cholesterol, creatinine, albumin, urea, s-hydroxybutyrate (BHBA), leptin, insulin, insulin-like growth factor-1 (IGF-1), growth hormone, 3,5,3'-triiodothyronine (T 3 ) and thyroxine (T 4 ) concentrations, and of activities of aspartate amino transferase (ASAT), lactate dehydrogenase (LDH) and glutamate dehydrogenase (GLDH) were taken 2 wk a.p. and in wk 1-16 and 20 p.p. between 0730-0900. Cows were gynaecologically examined weekly. The onset of first ovulation was specified by skim milk progesterone determination by a radioimmunoassay (twice/wk) and by rectal palpation. Energy balance (EB) traits were calculated and expressed as accumulated negative EB from parturition to EB equilibrium (AUC), EB nadir (EBN), rate of EB recovery following EBN (EBR), time from parturition to EBN (DEBN), and time from parturition to EB equilibrium (DEBE). Results: Resumption of ovarian cyclicity postpartum was not reflected by any of the EB traits. However, a small degree of EBN and a fast EBR were related to a short period from parturition to conception. Survival analysis with timevarying covariates revealed that high plasma concentrations of T 3 and T 4 p.p. were significantly associated with a high chance of an early start of the ovarian cycle, and high concentrations of glucose and cholesterol were associated with a short time empty, respectively. Conception at first service was positively associated with EB at first service and with progesterone concentration at 10-13 d after first service. However, leptin, as most other metabolic and endocrine traits, was not associated with any of the reproductive traits. In conclusion, thyroid hormones may play an important role in the onset of the ovarian cycle p.p., and a good energy status enhances the chance of conception at first service and shortens time empty.

Effect of diet and GnRH administration on post-partum ovarian cyclicity in autumn-lambing ewes

Using autumn-lambing ewes, this study investigated (i) the effects of diet on gonadotrophin secretion and responsiveness of the hypothalamic-pituitary-ovarian axis to exogenous GnRH during the early post-partum period; and (ii) whether ovulation prior to completion of uterine involution results in an increased incidence of aberrant ovarian cycles. Thirty-two ewes rearing 1.9±0.12 lambs were equally allocated to two dietary treatments at lambing (22 October ±0.2 day). Diets comprised ad libitum hay and 1.5 kg per ewe per day of one of two concentrates (11.5 MJ ME, 195 g CP per kg) containing 300 g kg −1 cracked maize grain ( M) or 300 g kg −1 sugar beet pellets ( S). Half of the ewes on each diet ( G) received 25 i.v. injections of 250 ng GnRH in 2 ml 0.9% saline at 2 h intervals from days 12–14 post-partum while remaining ewes ( N) were monitored for the resumption of spontaneous ovarian cyclicity. Blood samples were obtained from all ewes throughout the study (lambing to 18 December) for measurement of circulating hormone concentrations and the uteri and ovaries of all ewes were examined via laparoscopy on day 21 post-partum. There were no effects of dietary treatment on ewe daily live weight loss, lamb daily live weight gain or the immediate post-partum increase in circulating FSH concentrations. Diet did not affect insulin concentrations or LH pulse frequency on day 12 post-partum but LH pulse amplitude was lower in ewes fed concentrate M compared to concentrate S (1.4±0.10 versus 1.7±0.12 ng ml −1, respectively, P<0.05) and this was associated with an increased interval to the resumption of spontaneous ovarian cycles (35±3.1 versus 26±2.1 day, respectively, P<0.05). Administration of exogenous GnRH increased ( P<0.05) the proportion of ewes on both diets that ovulated within 20 days of parturition and advanced the onset of ovarian cyclicity in ewes fed concentrate M by 9.5 days (significance of interaction, P<0.05). Four ewes, all of which ovulated before day 22 post-partum, had extended luteal activity while in remaining ewes, duration of the first luteal phase was inversely related to the time of first ovulation ( r 2=0.16, P<0.05). Results demonstrate that (i) the onset of ovarian cyclicity is influenced by diet and can be advanced by administration of exogenous GnRH; and (ii) ovulation during the early post-partum period is associated with an increased incidence of extended luteal activity.

First ovulation and ketone body status in the early postpartum period of dairy cows

The effect of ketone body status on occurrence of first ovulation during early lactation was assessed in 84 multiparous dairy cows under field conditions. Animals were equally distributed across 8 farms and were controlled by the same herd fertility monitoring program. Cows were visited twice antepartum and 6 times postpartum at weekly intervals between 5:30 and 8:30 AM. On these occasions, body condition scores and milk yields were measured, blood and milk samples were taken, cows were gynecologically examined, and parameters of reproduction were determined. The onset of first ovulation was specified by milk progesterone determination and rectal palpation. Cows starting postpartum ovarian cyclicity within or after 30 d were classified as early and late responders (ER and LR, respectively). Resumption of the estrous cycle within 30 d postpartum is considered optimal under practical conditions, and classification based on this threshold value resulted in groups of equal size and equal distribution of ER + LR cows within farms. Ketone bodies measured were βhydroxybutyrate in serum and acetoacetate and acetone in serum and milk. Blood serum and milk ketone body concentrations during the first 6 wk of lactation were higher in LR than in ER, whereas plasma glucose and nonesterified fatty acid and milk fat, protein and urea concentrations did not differ between groups. Maximal concentrations of ketone bodies from parturition to first ovulation were better predictors of the onset of the estrous cycle than mean or minimal concentrations over the same period. Milk acetone and serum β-hydroxybutyrate concentrations provided the most reliable information with regard to resumption of ovarian activity of all ketone bodies.

Serum cholesterol and triglycerides in postpartum beef cows and their relationship to the resumption of ovulation

The variations in lipid metabolism according to the physiological stage and their relationship to the resumption of postpartum ovarian cyclicity were assessed in Limousine beef cows fed a grass diet over 3 yr. Weekly blood samples were collected from 59 cows beginning 10 wk before to 20 wk after calving to evaluate serum cholesterol and triglyceride concentrations and electrophoretic lipoprotein fractions. After parturition, progesterone concentrations were also measured at weekly intervals to determine time of resumption of ovulation. Cows were categorized by resumption of postpartum ovarian cyclicity into 3 groups : early (4 to 6 wk post partum, n=36); mid (7 to 10 wk post partum, n=46) and late (after 11 wk post partum, n=38). Higher serum triglyceride values (P<0.05) were observed during the last 10 wk of pregnancy (0.36 ± 0.15 g/L) than during the first 20 wk of suckling (0.29 ± 0.09 g/L). Cholesterol values decreased significantly (P<0.05) at the end of pregnancy, were minimal (1.01 ± 0.03 g/L) at parturition, and increased again up to 9 wk post calving. Increased cholesterolemia and low serum triglyceride values after calving could be linked to the increased bovine α-lipoprotein fraction and decreased β fraction. Serum triglyceride concentrations were not related to the resumption of postpartum ovarian cyclicity. Higher serum cholesterol values were observed from 2 wk before to 4 wk after calving in cows with early rather than mid and late resumption of ovarian cyclicity. Therefore, modifications in lipid metabolism during the puerperium seem to be related to resumption of cyclicity during the early postpartum period.

Resumption of oestrous and ovarian cyclicity during the post-partum period in autumn-lambing ewes is not influenced by age or dietary protein content

AbstractThe objective was to determine the effect of age and dietary protein content on post-partum oestrous and ovarian cyclicity in autumn-lambing ewes. Twenty-four multiparous (age 4·5 (s.e. 0·61) years) and 24 primiparous (age 1·5 years) ewes which lambed on 28 October (s.e. 0·2) and were rearing 2·0 and. 1·7 (s.e. 0·13) lambs, respectively, were equally allocated to two dietary treatments in a 2 × 2 factorial design. Diets comprised a d libitum hay supplemented with concentrate (12·5 MJ metabolizable energy per kg dry matter (DM) and either 210 or 140 g crude protein per kg DM), offered at a daily allowance of 1·2 kg per ewe from lambing to weaning (18 December) and 0·4 kg per ewe thereafter. Throughout the study (3 November to 24 May) ewes were group-housed in straw-bedded pens under natural photoperiod at 57°N and their live weights and body condition scores were assessed at 2-week intervals. A raddled vasectomized ram was continually present with each group and ewes marked by the ram were recorded thrice weekly. Blood samples were obtained thrice weekly for measurement of peripheral progesterone concentrations and ovulation rate was determined by laparoscopy during January and March. There was no significant effect of dietary protein content on any of the variables measured. For multiparous and primiparous ewes, mean live weights and body condition scores at lambing were 79·5 (s.e. 1·41) v. 58·4 (s.e. 1·54) kg (P &lt; 0·001) and 2·5 (s.e. 0·05) v. 2·2 (s.e. 0·05) (P &lt; 0·001) and daily live-weight losses over the suckling period were 153 (s.e. 19·3) v. 85 (s.e. 21·1) glday (P &lt; 0·05). Intervals from parturition to first overt oestrus were 39 (s.e. 3·2) v. 33 (s.e. 2·3) days and to the onset of ovarian cyclicity were 29 (s.e. 4·9) v. 25 (s.e. 1·5) days. Durations of ovarian cyclicity were 133 (s.e. 27·1) and 110 (s.e. 5·7) days (P &lt; 0·01) during which 7·6 (s.e. 0·32) and 6·5 (s.e. 0·34) (P &lt; 0·05) ovarian cycles were recorded respectively. Fifteen ewes had initial short cycles (≤10 days), six had prolonged cycles (≥21 days) and 11 had extended inter-luteal phase intervals (≥8 days). All ewes had recent ovulations at the January laparoscopy but only 19 multiparous and nine primiparous ewes had ovulations in March. Mean ovulation rates were: January 2·2 (s.e. 0·14) and 1·4 (s.e. 0·13) (P &lt; 0·001), and March 1·6 (s.e. 0·23) and 1·2 (s.e. 0·15) for multiparous and primiparous ewes, respectively. It is concluded that, for ewes lambing at their normal time of mating, (i) the strong seasonal drive for reproduction results in the resumption of oestrous and ovarian cyclicity during the early post-partum period; (ii) initial luteal phases may be of short or extended duration; (Hi) there is no effect of age or dietary protein content, within the range studied, on the onset of ovarian cyclicity; and (iv) multiparous ewes experience a greater number of ovarian cycles and achieve higher ovulation rates than primiparous ewes.

Factors in the resumption of ovarian activity and uterine involution in postpartum dairy cows

As a step toward clarifying intricate relationships among the factors responsible for delay of postpartum ovarian cyclicity and uterine involution in high-producing dairy cows, we analyzed the clinical, production, and environmental findings derived from 72 Holstein—Friesian dams in one dairy herd for 13 consecutive months. The interval from calving to resumption of ovarian activity ranged from 13 to 64 days, the average being 25 ± 13 days SD. Variation in the number of days between calving and first ovulation was largely accounted for by the factors included in the investigative model ( r 2=0.75, P<0.001), as shown by covariance analysis. The greatest effect on resumed ovulation was, by far, that of the daily level of total digestible nutrients (TDN) at resumption of the postpartum ovarian activity ( P<0.001), although the puerperal condition was also shown to play a significant role ( P<0.05) on the resumption of ovulation. Dams without puerperal complications ovulated markedly earlier (at 22 days) than those encountering puerperal complications (≥ 31 days). The greatest influences on the uterine involution were puerperal condition ( P<0.001) and parity ( P<0.01), followed by season of calving ( P<0.05). Age at calving, daily 4% fat corrected milk yield, daily TDN and crude protein levels had no significant bearing on involution. The puerperal condition had the most noticeably widespread influence in governing both ovarian activity and uterine involution in postpartum cows, while a level of TDN intake played an important role in the resumption of ovarian activity.

Parturition and periparturient reproductive and metabolic hormone concentrations in prenatally androgenized beef heifers.

Primiparous Angus x Simmental heifers (n = 43) in a single-calf heifer (SCH) system (i.e., heifers are bred, calved, and placed in drylot pens with their calves at side and fed to slaughter weights) were studied to evaluate the effects of prenatal androgenization on parturition and on periparturient reproductive and metabolic hormone concentrations. Seven prenatally androgenized (PA) and seven control (C) heifers were used for blood collection to characterize parturient and lactation endocrine profiles; all heifers were used for blood collection to characterize postpartum ovarian cyclicity. Serum concentrations of progesterone, estradiol, testosterone, 13,14-dihydro-15-keto-PGF2 alpha (PGFM), and prolactin from 10 d before to 3 d after parturition were similar for PA and C heifers. Calf birth weights (34.7 +/- .9 kg) and calving ease scores (1.34 +/- .14) were similar between treatments. Postpartum ovarian cyclicity was similar; only 6 of 22 PA (27.3%) and 3 of 21 C (14.3%) heifers were cyclic by 70 d postpartum, based on weekly serum progesterone concentrations. Serum concentrations of insulin, triiodothyronine (T3), and prolactin at 35, 70, and 105 d of lactation were similar for PA and C heifers; thyroxine (T4) concentrations were similar at 35 and 70 d but greater (P < .01) at 105 d of lactation in PA heifers than in C heifers. Although mean serum concentrations of insulin, T3, and T4 were similar between treatments, prolactin concentrations were greater (P < .05) in C than in PA lactating heifers. We conclude that PA heifers are similar to C heifers with respect to parturition and to periparturient reproductive and metabolic hormone concentrations. Therefore, management requirements of PA primiparous beef heifers seem to be similar to those of C primiparous beef heifers, and PA heifers can be used successfully in a SCH system.

The influence of nutrient status of post-partum ewes on ovarian cyclicity and on the oestrous and ovulatory responses to ram introduction

We have assessed, in post-partum Merino ewes ( n = 120) lambing during the ovulatory season, the influence of nutrient status on the onset and cessation of ovarian cyclicity and on the oestrous and ovulatory responses to ram introduction. Two flocks were studied from mid-pregnancy onwards; flock R + + included vasectomized rams (8%) and flock R - + was isolated from rams until Day 1 of the study when the ewes were 21–37 days post partum. Within each flock, from mid-pregnancy until Day 7, three groups of ewes ( n = 20/group) received normal or restricted nutrition, or restricted nutrition with a supplement of lupins and oats from Day - 14 to Day 7. After Day 7 all ewes received similar normal nutrition. All ewes received progestagen from a pessary from Day - 7 to Day 1. On Day 1 the rams were removed from flock R + + and new vasectomized rams (10%) were introduced into both flocks. Compared with ewes of normal nutrient status, the ewes of reduced nutrient status had a longer ( P<0.05) interval to first oestrus (65.1±3.4 vs 37.7±3.2 days, mean±s.e.m.), an earlier ( P<0.05) cessation of oestrous cycles as assessed from the time of the last observed oestrus within the period of study (to Day 115) (110.5±5.6 vs 128.5±4.0 days) (flock R + +) and a lower ( P<0.001) incidence of oestrus (4/20 vs 14/20) within 14 days of ram introduction, but a similar ( P>0.05) incidence of ovulation (as assessed from plasma progesterone on Day 13) (15/19 vs 19/20) (flock R - +). Short-term nutrient supplementation did not affect these responses. The occurrence of oestrus within 14 days of ram introduction was similar ( P>0.05) in the ewes receiving normal nutrition in flock R - + and flock R + + (14/20, 14/20). These results demonstrate that reduced nutrient status of post-partum ewes can (a) delay the onset of ovarian cyclicity post partum; (b) inhibit the occurrence of ram-induced oestrus (but not ovulation); and (c) hasten the onset of cessation of oestrous cycles.

Gonadotropin-Releasing Hormone Secretion during the Postpartum Anestrous Period of the Ewe1

An increase in episodic release of LH is putatively the initial event leading to the onset of postpartum ovarian cyclicity in ewes. This experiment was conducted to determine the relationship between hypothalamic release of GnRH and onset of pulsatile secretion of LH during postpartum anestrus. Control ewes (n = 7) were monitored during the postpartum period to determine when normal estrous cycles resumed. In controls, the mean interval from parturition to the first postpartum estrus as indicated by a rise in serum progesterone greater than 1 ng/mg was 25.8 +/- 0.6 days. Additional ewes (n = 4-5) at 3, 7, 14, and 21 days postpartum (+/- 1 day) were surgically fitted with cannula for collection of hypophyseal-portal blood. Hypophyseal-portal and jugular blood samples were collected over a 6- to 7-h period at 10-min intervals. The number of GnRH pulses/6 h increased (p less than 0.05) from Day 3 postpartum (2.2 +/- 0.5) to Days 7 and 14 (3.6 +/- 0.2 and 3.9 +/- 0.4, respectively). A further increase (p less than 0.05) in GnRH pulse frequency was observed at Day 21 postpartum (6.4 +/- 0.4 pulses/6 h). Changes in pulsatile LH release paralleled changes observed in pulsatile GnRH release over Days 3, 7, 14, and 21 postpartum (0.83 +/- 0.3, 2.8 +/- 0.4, 2.9 +/- 0.6, and 4.0 +/- 1.1 pulses/6 h, respectively). GnRH pulse amplitude was higher at Day 21 than at Days 3, 7, or 14 postpartum. These findings suggest that an increase in the frequency of GnRH release promotes the onset of pulsatile LH release during postpartum anestrus in ewes.