Ovarian Function In Dairy Cows Research Articles

Effect of repeated low doses of gonadotropin-releasing hormone on the secretion of luteinizing hormone and follicle-stimulating hormone, and ovarian function in dairy cows suffering from anovulation type I

The aim of the study was to evaluate the effect of repeated low doses of gonadotropin-releasing hormone (GnRH) agonist buserelin once a day for 5 days on follicle-stimulating hormone (FSH) and luteinizing hormone (LH) release, and ovarian function in dairy cows with anovulation type I. The study was conducted on 10 anovulatory Polish Holstein-Friesian cows. Cows in Group 1 (n = 5) received 4 µg of buserelin intramuscularly. once a day for 5 days. Control cows from Group 2 (n = 5) received saline. Concentrations of progesterone, FSH, and LH in the blood were analysed using radioimmunoassay (RIA). Ovarian structures were monitored weekly after the end of treatment by ultrasound for 4 weeks. Injections of buserelin increased FSH and LH concentrations. Release of FSH and LH was largely variable, but there was significant (P < 0.001) interaction between time and treatment during all treatment days. The number of follicles in the treatment group was significantly greater (P = 0.029) than in the control group on day 5, the diameter of follicles on day 12 was also larger (P < 0.01) in treated than in control cows. Ovulation occurred in 4 of the 5 treated cows, but only in 1 of the control cows in the 40 days after treatment. In conclusion, repeated low doses of GnRH analogue buserelin once a day for 5 days may increase the concentration of FSH and LH in dairy cows with anovulation type I.

Supplementation of rumen-protected lysine during the close-up period improves vaginal discharge clearance in Holstein dairy cows.

We aimed to evaluate the effects of rumen-protected lysine (RPL) supplementation during the close-up period on uterine involution and the resumption of ovarian function in dairy cows. Fifty-two multiparous Holstein cows were categorized based on parity and expected calving date and randomly assigned to the RPL or control (CON) groups. The RPL group received 80 g of RPL daily from day 21 before the expected calving date until parturition. Blood samples were obtained twice weekly from pre-supplementation to 6 weeks postpartum. The onset of luteal activity postpartum was determined via ultrasonography twice weekly for up to 6 weeks postpartum. Uterine involution was tracked at 3 and 5 weeks postpartum through the vaginal discharge score, percentage of polymorphonuclear cells (PMN) in endometrial cytology samples, presence of intrauterine fluid, and gravid horn diameter via ultrasonography. Before supplementation, the RPL group showed amino acid imbalance, which was improved by RPL supplementation. There were no significant differences in the onset of luteal activity, percentage of PMN, intrauterine fluid, or the diameter of the uterine horn between the two groups. The vaginal discharge score in the RPL group decreased from 3 to 5 weeks postpartum, whereas that in the CON groups did not decrease. The number of cows with clinical endometritis was lower in the RPL group. Overall, RPL supplementation during the close-up period enhanced vaginal discharge clearance, potentially averting clinical endometritis, but did not affect the first ovulation in dairy cows.

Intramammary lipopolysaccharide infusion alters gene expression but does not induce lysis of the bovine corpus luteum

Data from various studies indicate that the ovarian function in dairy cows can be compromised during intramammary infections. Therefore, in this study, we investigated if an experimentally induced mastitis has an effect on corpus luteum (CL) function in 14 lactating cows. On d 9 of the estrous cycle (d 1=ovulation), cows received a single dose of 200 μg of Escherichia coli lipopolysaccharide (LPS; dissolved in 10 mL of NaCL; n=8) or 10 mL of saline (control; n=6) into one quarter of the mammary gland. Measurements included plasma cortisol, haptoglobin, and progesterone (P4) concentrations, as well as luteal size (LTA) and relative luteal blood flow (rLBF). Sampling was performed on d 1, 4, and 8. On d 9, the main examination day, sampling was performed immediately before (0 h), every 1h (or at 3-h intervals for LTA and rLBF) until 9 h, as well as 12 and 24 h after treatment. Thereafter, measurements were taken on d 12, 15, 18, and then every 2 d until ovulation. Luteal tissue was collected for biopsy 24 h before and 6 h after treatment. Quantitative real-time PCR was applied to assess mRNA expression of steroidogenic factors (STAR, HSD3B), caspase 3, toll-like receptors (TLR2, -4), tumor necrosis factor α (TNFA), and prostaglandin-related factors (PGES, PGFS, PTGFR). Intramammary LPS infusion caused considerable inflammatory responses in the treated udder quarters. No decrease in plasma P4 concentrations was noted after LPS-challenge, and P4 levels did not differ between LPS-treated and control cows. Furthermore, LTA and rLBF values were not decreased after LPS challenge compared with the values obtained immediately before treatment. However, LPS infusion increased plasma levels of cortisol and haptoglobin compared with the control group. In the CL, mRNA abundance of TLR2 and TNFA was increased in cows after LPS-challenge (but not in control cows), whereas TLR4, steroidogenic, and prostaglandin-related factors remained similar to the mRNA abundance before treatment. In conclusion, intramammary LPS challenge induces systemic inflammatory reactions which alter the luteal mRNA abundance of TLR2 and TNFA but does not induce lysis of the CL.

Effects of prepartum oilseed supplements on subclinical endometritis, pro- and anti-inflammatory cytokine transcripts in endometrial cells and postpartum ovarian function in dairy cows.

Postpartum uterine infections affect ovarian function and delay ovulation in cattle. As dietary fats can affect immune cell function, we investigated the influence of prepartum diets on postpartum uterine inflammatory status (UIS) as assessed 25±1 days postpartum by endometrial cytology (normal: ≤8% polymorphonuclear cells (PMN) vs subclinical endometritis (SCE): >8% PMN) and associations between SCE, pro- and anti-inflammatory cytokine gene expression and ovarian function. During the last 5 weeks of gestation, dairy cows received a diet supplemented with 8% rolled sunflower (n=10) or canola seed (n=9) or no oilseed (n=9). Ovaries were scanned until 35 days postpartum. Prepartum diets did not influence SCE, but a preovulatory-size follicle developed sooner (P≤0.05), the interval to first ovulation was shorter and the proportion of cows ovulating within 35 days postpartum was greater in the sunflower seed group. Although mRNA expression of cytokines was not affected by diet, cows with SCE had higher (P≤0.05) expression of interleukin-1β (IL1B), interleukin-8 (CXCL8), IL10 and tumour necrosis factor-α (TNF) than normal cows. The interval (mean ± s.e.m.) from calving to preovulatory-size follicle was shorter (P≤0.05) in normal (13.2±0.9 days) than SCE cows (18.7±1.4 days). In summary, a prepartum diet supplemented with sunflower seed positively influenced postpartum ovarian function without affecting UIS or pro- and anti-inflammatory cytokine gene expression in endometrial cells.

Effect of site of starch digestion on metabolic hormones and ovarian function in dairy cows

Delayed resumption of postpartum oestrous cycles in dairy cows is linked to low plasma insulin status and associated changes in ovarian function. Previous studies showed that plasma insulin can be raised by increasing dietary starch concentration, but it is not known if rumen digestible starch and bypass starch would be equally effective. The objective of the two experiments reported here was to investigate whether site of dietary starch digestion influences metabolic hormones and ovarian function. Cows were fed on a standard diet from calving until 40 days postpartum and then fed on treatment diets until 70 days postpartum. In Experiment 1, six cows were transferred to each of five diets with a starch content of 190 g/kg DM, of which 0.40, 0.45, 0.50, 0.55 or 0.60 was bypass starch. In Experiment 2, eight cows were transferred to each of four diets containing concentrates with low (L) or high (H) starch content and predominantly grass (G) or maize (M) silages in a factorial design. Between 60 and 70 days postpartum, plasma insulin was not influenced by site of starch digestion in Experiment 1, but insulin was increased by H ( P = 0.020) and M ( P = 0.048) in Experiment 2. Dietary bypass starch content negatively influenced plasma glucagon concentration ( P = 0.046) and the insulin to glucagon ratio ( P = 0.005) in Experiment 1. Growth hormone, insulin-like growth factor-I and leptin did not vary among diets in either experiment. The number of small (< 5 mm) ovarian follicles before ovulation tended ( P = 0.056) to decrease with increasing dietary bypass starch content and was negatively related ( P = 0.046) to plasma glucagon in Experiment 1, but there was no other dietary effect on ovarian function in either experiment. The main conclusion from these experiments is that rumen digestible starch and rumen bypass starch can be equally effective for maintaining plasma insulin and ovarian function of high-yielding dairy cows in early lactation.

Nutrition, Metabolism, and Fertility in Dairy Cows: 3. Amino Acids and Ovarian Function

Plasma insulin concentrations influence resumption of ovarian activity in postpartum dairy cows, and plasma insulin can be manipulated by changing dietary starch and fat supply. The objective of this experiment was to investigate the role of dietary amino acids in altering peripheral metabolic hormones and ovarian function. Thirty-two cows were fed a standard diet from calving until 40 d in milk (DIM), and then 8 cows were transferred to each of 4 dietary treatments until 70 DIM. The 4 diets were designed to supply either low (diets 1 and 2) or high (diets 3 and 4) levels of metabolizable protein (MP), containing either low (diet 1 and 3) or high (diets 2 and 4) proportions of Leu. Leucine was manipulated with heat-treated lupins and corn gluten meal. Estrus was synchronized at 60 DIM. Between 60 and 70 DIM, energy intake and energy balance were similar among diet groups, although cows receiving high MP containing high Leu had a greater milk yield than other groups (means: 37.8, 37.1, 37.4, 39.4±standard error 0.85 kg/d for diets 1 to 4, respectively). Interactions between MP and Leu were found for insulin, glucagon, and the ratio between them. Insulin was not affected by Leu in diets with low MP but was decreased by greater Leu in diets with high MP (means: 0.37, 0.32, 0.46, 0.39±SE 0.031 ng/mL for diets 1 to 4, respectively). Glucagon was not affected by MP in diets with low Leu but was increased by greater MP in diets with high Leu (means: 92, 81, 88, 95±SE 6.0 pg/mL for diets 1 to 4, respectively). For the low-MP treatments, the insulin-to-glucagon ratio was greater with high Leu; for the high-MP treatments, the insulin-to-glucagon ratio was greater with low Leu (means: 4.28, 5.42, 5.16, 4.22±SE 0.456 for diets 1 to 4, respectively). There was no effect of MP or Leu on ovarian follicle numbers or reproductive hormones. Based on hormonal and ovarian responses, we conclude that altering metabolic hormones through manipulation of amino acid supply and balance is unlikely to have a significant effect on ovarian function in dairy cows.

Nutrition, Metabolism, and Fertility in Dairy Cows: 2. Dietary Fatty Acids and Ovarian Function

Plasma insulin has important implications for ovarian function in dairy cows. Previous work demonstrated that plasma insulin increased with increasing dietary starch and decreasing dietary fatty acid concentrations. The objective of this experiment was to investigate hormonal and ovarian responses to dietary fatty acid content with no change in other dietary components. Thirty cows were fed a standard diet from calving until 40 d in milk (DIM) and then 6 cows were transferred to each of 5 diets containing 0, 8, 15, 23, and 30 g/kg of dry matter (DM) of calcium salts of palm fatty acids (CaPFA; Megalac) until 70 DIM. Estrus was synchronized at 60 DIM. Between 60 and 70 DIM, energy intake, milk yield, and energy balance were similar among diet groups. Plasma insulin decreased when dietary concentration of CaPFA exceeded 15 g/kg of DM (insulin: 0.46, 0.41, 0.46, 0.33, 0.28±SE 0.034 ng/mL for diets containing 0 to 30g of CaPFA/kg of DM, respectively). Maximum plasma insulin to glucagon ratio was observed with 15g of CaPFA/kg of DM (ratios: 3.99, 4.33, 4.67, 3.45, 2.89±SE 0.156 for diets containing 0 to 30g of CaPFA/kg of DM, respectively). Plasma concentrations of growth hormone, insulin-like growth factor-I and leptin did not vary between diets. The number of small (<5mm) ovarian follicles was negatively related to plasma insulin concentration (r = −0.328) and was stimulated by CaPFA supplementation at all rates tested compared with cows receiving zero CaPFA (small follicles preovulation: 6.7, 11.2, 11.5, 11.3, 11.9±SE 1.48 for diets containing 0 to 30g of CaPFA/kg of DM, respectively). The number of medium-sized follicles, and diameters of the ovulatory follicles and corpora lutea, were not affected by CaPFA supplementation. It is concluded that dietary total fat concentration should be below 50 g/kg of DM to avoid depressing plasma insulin concentration in cows at the start of the breeding period.

The effects of ketoprofen on ovarian function in dairy cows

Two experiments were conducted to investigate the effects of ketoprofen on ovarian function in dairy cows. In experiment I, eight non-milking dairy cows were administered a 0.9% saline solution daily from day 8 (day −3) of ensuing synchronized estrous cycle at 24-h intervals over 4 days (control observation). After an estrous cycle rest, the cows were given the recommended daily therapeutic dose (3 mg/kg, i.m.) of ketoprofen (Ketofen 100; 10%, Merieux/Webster, Australia) from day 8 (day −3) of the synchronized estrous cycle at 24-h intervals over 4 days. All cows received an intramuscular injection of prostaglandin \({\text{F}}_{{{\text{2}}\alpha }}\) (30 mg, Lutalyse) either 6 h before the first treatment of saline solution or 6 h before the first injection of ketoprofen. Ultrasonography of the ovaries was performed daily from the day before (day −4) experimental treatments until day 2 after induced estrus, to monitor the growth of the ovulatory follicle and ovulation, and then on day 9 after estrus to determine the presence and the size of the corpus luteum. In experiment II, five non-milking dairy cows were used in two successive observations. The plasma preovulatory estradiol-17β peak and progesterone concentrations were determined, and ovarian ultrasonography was performed to determine ovulation and corpus luteum development. Results obtained from experiment I showed that the diameter of dominant ovulatory follicle on day of estrus was significantly (p<0.05) higher in saline-treated estrous cycle compared to that of ketoprofen-treated cycles (13.8±1.3 vs 10.9±0.4 mm). Furthermore, by 48 h after standing estrus, ovulation had taken place in seven of eight saline-treated estrous cycles, whereas only three ketoprofen-treated cows had ovulated by 48 h after standing estrus (p<0.05). A significantly (p<0.05) higher mean estradiol-17β peak was observed in ketoprofen-treated estrous cycles at estrus compared to that of the control estrous cycles (experiment II). Additionally, a significant (p<0.05) daily increase in the mean plasma progesterone concentration was observed after ketoprofen treatment beginning from day 0 to 6 of the subsequent estrous cycle (p<0.05). The results of the present study demonstrate that administration of ketoprofen during the pre- and periovulatory period of the estrous cycle in dairy cows impairs final growth of ovulatory follicle, leading to a disturbance in the normal process of ovulation.

Relationship between endotoxin and prostaglandin (PGE 2 and PGFM) concentrations and ovarian function in dairy cows with puerperal endometritis

Blood concentrations of progesterone, 13,14-dihydro-15-keto-prostaglandin F2alpha (PGFM) and endotoxin, and uterine fluid concentrations of prostaglandin E 2 (PGE 2), PGFM and endotoxin were evaluated in 14 dairy cows with puerperal endometritis (mild ( n=6) and heavy ( n=8)). Endotoxin was measured using a quantitative kinetic assay. Cows with heavy endometritis had significantly higher concentrations of plasma PGFM ( P<0.01) and uterine fluid PGE 2 and endotoxin ( P<0.05) than cows with mild endometritis. Concentrations of PGFM in plasma and uterine fluid, of PGFM and PGE 2, and PGE 2 and endotoxin in uterine fluid were positively and significantly ( P<0.05) correlated. The presence of endotoxin in plasma was detected in one out of six mild and in eight out of eight heavy endometritis cows. Peak plasma endotoxin concentrations (0.08–9.14 endotoxin units/ml (EU/ml) were observed between 1 and 12 days postpartum (pp) and thereafter amounts generally remained below 0.1 EU/ml (last day of detection: Day 27 pp). Abnormal ovarian function was observed in six cows (four with prolonged anoestrus and two with long luteal phase after the first postpartum ovulation). Plasma endotoxin concentrations were detected in the anoestric cows. The results suggest that: (i) concentrations of uterine fluid endotoxin and PGE 2 and of plasma PGFM are related to the degree of endometritis; (ii) absorption of endotoxin from the uterus to the bloodstream occurs, mainly in heavy endometritis cows; and (iii) there is a relationship between uterine infection, endotoxin production and resumption of pp ovarian activity.

Relationship among insulin-like growth factor-I, blood metabolites and postpartum ovarian function in dairy cows.

The relationship among nutritional status, systemic insulin-like growth factor-I (IGF-I) and ovarian function early postpartum were investigated. A total of 27 Holstein-Friesian cows, 10 that cycled normally within 20 days postpartum, 5 diagnosed with follicular cysts, 8 with persistent corpus luteum (CL) after the first ovulation postpartum and 4 with inactive ovaries were used for the study. Blood samples were collected 1-3 times per week, for 60 days pre- and postpartum, for IGF-I, progesterone, estradiol, free fatty acids (FFA), blood urea nitrogen (BUN), and aspartate aminotransferase (AST) determination. Inactive ovary and cystic cows had a higher body condition score before calving and lost more condition than normal or persistent CL cows. Immediately postpartum, IGF-I levels were higher and rose sharply in cows that cycled normally than in cystic, inactive ovary or persistent CL cows. At calving and early postpartum, FFA was higher in inactive ovary and cystic than in normal and persistent CL cows. There was a significant strong positive relationship between IGF-I and BUN, and strong negative relationships between IGF-I and FFA and AST in all groups. There was a positive relationship between serum IGF-I and estradiol in normal cystic and inactive ovary cows. This study found that overconditioned cows during the dry period or at calving, lost more body condition postpartum. These cows also had a deeper and longer period of negative energy balance (NEB), poor liver function and low circulating IGF-I concentrations early postpartum. Such cows were likely to have poor reproductive function as seen in development of cystic ovaries, persistent CL and inactive ovary. Changes in serum IGF-I early postpartum may help predict both nutritional and reproductive status in dairy cattle.

Preovulatory follicular status and diet affect the insulin and glucose content of follicles in high-yielding dairy cows

Insulin and glucose may be limiting factors for ovarian function in dairy cows genetically selected for high milk yield. The effects of nutrition on the intrafollicular content of insulin and glucose were investigated in Israeli Holstein dairy cattle fed a basic total mixed ration and producing 34–39 kg of milk daily. In experiment 1, carried out in 11 oestrus-synchronised cows, little variation in insulin concentration was found in plasma sampled during the luteal phase, but high variation was found in plasma sampled during the follicular phase. Therefore, in order to prevent confounding the effects of diet and of phase in cycle in the following experiments, experimental diets were fed during the luteal phase of synchronised oestrus cycles. In experiment 2, designed as Latin-Square, six cows received sequentially diets containing 17.1 (control) or 19.7% of crude protein, using two sources of supplementary protein, i.e. soyabean meal (SBM) and corn gluten meal (CGM), differing in ruminal degradability and leucine content. When dry matter intake was used as covariant, plasma insulin on day 16 was 29.5 and 26.4% higher in cows fed diets containing SBM and CGM than in the control ( P<0.05). In experiment 3, 17 cows were individually fed the basic diet and then switched to isoenergetic diets containing SBM ( n=5), CGM ( n=6) or corn grain (CG, n=6) given from day 10 to 16 of the synchronised oestrus cycle. On the eve of day 16, and in the morning of day 17, they were administered PGF 2α and the content of 26 largest follicles was aspirated by using the transvaginal ovum pick-up technique. Follicles were sorted into two classes (preovulatory and subordinate) according to oestradiol concentration and the progesterone:oestradiol ratio in follicular fluid (FF). Higher concentrations of insulin (0.282 versus 0.127 ng/ml, P<0.0001) and of glucose (0.614 versus 0.386 g/l, P<0.002), were found in FF from preovulatory follicles. The insulin concentration in the FF of cows fed the CG diet was 26% higher than in their counterparts fed CGM ( P<0.04), SBM being intermediate. Dietary effects did not reach significance in subordinate follicles. The finding that preovulatory follicular status is associated with increased intrafollicular insulin and glucose suggests that insulin is involved in follicular maturation. The nutritional effect on intrafollicular glucose and insulin may have practical implications to optimise feeding in dairy cows during phases of the oestrus cycle.

Effect of passive immunization against testosterone on reproductive hormone secretion and ovarian function in dairy cows and pubertal beef heifers

Multiparous dairy cows were divided in 3 groups from Day 5 up to Day 56 post partum: high energy level (Group H, n=10), low energy level (Group L, n=10) and low energy level plus anti-testosterone bovine immunoglobulins (Group LI, n= 10). Undernutrition decreased body weight, body condition score, milk yield and energy balance in Groups L and LI compared to Group H (P<0.05), but had no effect on secretory pattern of LH. Passive immunization against testosterone increased LH secretion in Group LI (P<0.05). Follicular score and the presence of follicles ≥ 10mm on the ovary were not affected by underfeeding but were higher in Group LI than in Group L after immunization (P<0.01). The duration of the first luteal phase was shorter in Group H than in Groups L and LI and maximum progesterone levels reached were higher in Group LI than in Group H (P<0.01). Reproductive performance was not depressed by underfeeding and immunization. In the pubertal beef heifers maintained in anestrus by undernutrition had very low LH secretion. After passive immunization against testosterone, the increase of LH pulses number became almost significant (P=0.07). Following injection of exogenous LH, the number of follicles ≥ 9mm was higher in immunized (Group I, n=8) than in control heifers (Group C, n=7). Group I developed a dominant follicle sooner and of greater size than Group C. Passive immunization against testosterone increased LH secretion and follicular development.

Incidence and Treatment of Abnormal Postpartum Ovarian Function in Dairy Cows

The objectives of this study were to determine 1) the incidence of abnormal postpartum ovarian function in a large dairy herd in North Central Florida and 2) the effectiveness of gonadotrophin releasing hormone (GnRH) in treating this condition. The study was conducted from April 1988 to June 1989.

Incidence and treatment of abnormal postpartum ovarian function in dairy cows

The objectives of this study were to determine 1) the incidence of abnormal postpartum ovarian function in a large dairy herd in North Central Florida and 2) the effectiveness of gonadotrophin releasing hormone (GnRH) in treating this condition. The study was conducted from April 1988 to June 1989. The internal genitalia of the cows were initially examined per rectum (Day 0) between 19 and 29 (23 ± 0.25) d after calving and again 14 d later (Day 14) for evidence of uterine involution and ovarian activity. The presence of a palpable corpus luteum (CL) and retrospective determination of plasma progesterone (P4) concentrations > 1 ng/ml were the criteria used to assess ovarian activity. Cows possessing a palpable CL and P4 concentrations > 1 ng/ml on Day 0 were determined to be cycling normally. A total of 1356 cows was used in this study. On Day 0, two groups were formed: Group 1 consisted of normal, cyclic cows, Group 2 of noncyclic cows. On Day 0, alternate cows in Group 2 were treated with GnRH (100ug i.m). On Day 14, the previously nontreated cows in Group 2 were further divided into two groups, forming Group 3, nontreated cows and Group 4, cows treated with GnRH at this time. Group 5 was comprised of cows from Group 2 that did not respond to treatment with GnRH on Day 0; these cows were treated on Day 14 with GnRH (100ug i.m). Group 6 was comprised of nontreated cows from Group 2 that responded spontaneously (presence of a CL) by Day 14. Reproductive parameters evaluated were the percentage of cows pregnant within 180 d after calving and at the end of the study, the number of days open and the number of services per conception. Data were statistically analyzed using Chisquare and survival analysis. The results of this study indicate that the incidence of abnormal postpartum ovarian function in this herd was 30.2% and that the nontreated cows experienced more days open and required more services per conception than the treated cows, those that were cycling normally on the initial examination, and those that responded spontaneously by Day 14.

Post-partum, ovarian function in dairy cows as revealed by concentrations of oestradiol-17 β and progesterone in defatted milk

Concentrations of oestradiol-17 beta and progesterone in defatted milk have been used to study the post-partum restoration of ovarian function in 52 autumn-calved dairy cattle. In 32 cows the first preovulatory peaks in oestradiol-17 beta concentration (indicative of imminent ovulation) were less than or equal to 15 days and in 49 cows less than or equal to 49 days post partum. Delay to first ovulation was mainly due, not to failure of ovarian secretion of oestradiol-17 beta at preovulatory level, but to failure of oestradiol-17 beta at this level to exert its normal preovulatory function. Longer intervals to first ovulation were associated with longer intervals from calving to the clearance of placental oestradiol-17 beta, high peak milk yields and high body weight losses, suggesting that in high-yielding dairy cows these factors (themselves inter-related) may be associated with others, which are the immediate cause of the inhibition of the normal, preovulatory function of oestradiol-17 beta. Forty-eight per cent of cows had short, first ovulation cycles. Ovarian function, comprising oestradiol-17 beta secretion at preovulatory level, normal preovulatory function of oestradiol-17 beta and normal corpus luteum progesterone secretion were almost fully restored in this herd by the 49th day post partum.

Use of Concentrations of Progesterone and Estradiol-17β in Milk in Monitoring Postpartum Ovarian Function in Dairy Cows

Data from artificial insemination, rectal palpation, and hormone assays were used to characterize postpartum reproductive activity in 54 dairy cows. Progesterone and estradiol-17β were measured in milk samples collected for 120 d (Trial 1) or 65 d (Trial 2). Progesterone was higher and estradiol was lower in milk than in serum. Values for both hormones in milk were highly correlated with those in serum. Most cows (64%) had short first luteal phases (≤12 d). First rise (28 d) in progesterone was later (33.4 vs. 24.9 d) for cows having short rather than normal (>12 d) luteal phases. Cows were classified as having a short luteal phase followed by a normal luteal phase or as having normal luteal phases for the first two estrous cycles. Estradiol for the 6 d prior to each luteal phase was higher preceding the second phase than the short phase or those preceding both phases of cows with normal phases. Follicular function prior to ovulation, as measured by estradiol, was not responsible for short-lived corpora lutea. Concentrations of progesterone in milk in the late luteal phase prior to insemination were related to fertility.

Effect of active immunization against androstenedione on ovarian function in dairy cows and prepubertal gilts

Two experiments were performed to assess the effects of immunization against androstenedione on ovarian function in cows during the first 100 days after calving and in gilts at the onset of puberty. Seven Holstein-Friesian cows were immunized against androstenedione-11α-human serum albumin (AND-HSA) at 3 weeks before and at 3 weekly intervals after calving and compared with ten cows immunized against HSA. Titres against androstenedione were significant but low and variable (1: 280-1: 4). Two cows with the highest titres exhibited abnormal ovarian function which could be attributable to treatment. One cow developed a large follicular cyst and nymphomania. The other cow exhibited mild super ovulation in her first cycle after calving and multiple ovulations during later cycles. Other cows in the AND-HSA group also had a tendency to develop larger than normal follicles and follicular cysts. Groups of twelve prepubertal gilts were immunized against either androstenedione 11α-hemisuccinyl bovine serum albumin (AND-BSA) or BSA at 100, 121 and 142 days of age. Titres against AND were significant but were low and variable (1: 2500-1: 10). There was no effect of immunization against AND on onset of ovulation, puberty or ovulation rate in the first or second ovulatory cycles.