The effect of human menopausal gonadotropin and equine chorionic gonadotropin on the reproductive performance of treated ewes with short-term progesterone injections and sponge during the non-breeding season.

This study investigated the effect of human menopausal gonadotropin (hMG) on reproductive efficiency of synchronized ewes with the sponge and progesterone (P4) injection-based protocols. In study 1, anoestrous ewes (n = 120) were used. Sixty ewes were treated with sponge (S) for 12 days. The injection of eCG (SeCG group, n = 30) or hMG (ShMG, n = 30) was given at the time of sponge removal. Thirty ewes received IM injection of P4, three times every 48 h and the injection of hMG was given 24 h after the third P4 injection (3PhMG group, n = 30), and 30 ewes were used as control group. Pregnancy was diagnosed on day 50 after the release of ram. In study 2, 60 ewes were randomly divided into two equal groups. In the treated group with antibiotics (n = 30), before inserting, the sponges were impregnated with the antibiotic penicillin G sodium (5,000,000 IU) and in the control group (n = 30), there was no added antibiotics. Before inserting and after removing sponges, a vaginal cytology sample was taken with a sterile cotton swab. The number of neutrophils in each sample was counted and analysed. The rate of oestrus and total pregnancy was greater in SeCG (96.7, 93.3%), ShMG (82.8, 93.1%) and 3PhMG (67.9, 89.3%) groups compared with the control group (13.8, 41.4%) (p < .05). No significant difference was found in single, twin and total lambing and pregnancy rates after injection of eCG and hMG during the non-breeding season (p > .05). A higher percentage of control ewes had the vaginal smear with neutrophils more than 50% (96.7% vs. 76.7%; p < .05). In conclusion, a single dose of hMG can induce fertile oestrus in synchronized ewes with P4 administered by either injection or intravaginally. Purulent discharge and percentage of neutrophils were significantly reduced in the synchronized ewes by the impregnated sponges with the antibiotic penicillin.

Effect of body condition loss in early lactation Holstein cows on plasma IGF-I, prolactin and NEFA during breeding period and its association with some reproductive indices.

The associations between early lactation changes in the body condition score (BCS) and mid-lactation levels of blood insulin-like Growth Factor-I (IGF-1), prolactin, insulin, nonesterified fatty acids (NEFA), milk production and some reproductive indices were investigated. Monthly milk yield and BCS were recorded. Blood samples were collected on days 60, 90, and 120 (±5 days) of lactation. Twelve and 17 cows showed BCS losses ≤0.75 and >0.75 on day 60, respectively. BCS losses ≤0.75 till day 60 after calving enhanced the IGF-I concentration on day 90 (57.8 ± 10.7 vs. 35.6 ± 17.8 ng/mL; p = .001). The differences in blood metabolites were prominent on day 90. Trends of insulin changes between day 60 BCS (p = .04) groups were different. Inverse correlations were detected between IGF-I and NEFA (-0.6, p = .001), IGF-I and milk production (-0.4, p = .05), NEFA and prolactin (-0.8, p < .001) on day 90. Higher percentages of cows with BCS loss >0.75 (day 60) showed their first heat after day 40 postpartum. In conclusion, irrespective of BCS at the time of breeding, the level of BCS loss during the first 60 days of lactation may affect further reproductive performance due to prolonged alterations of IGF-I, NEFA, prolactin and insulin levels. The extent of postpartum BCS loss may be a predictor of the metabolic status of cows during mid-lactation.

The effect of progesterone injection combined with prostaglandineF2α, GnRH and hCG administrations on the pregnancy and lambing rate of lactating and non-lactating fat-tailed ewes during the breeding season.

The objective was to compare the effect of human chorionic gonadotropin (hCG) and gonadotropin-releasing hormone (GnRH) on the pregnancy and lambing rate of treated ewes with a short-term progesterone (P4) injection during the breeding season. In Exp 1, non-lactating ewes (n = 158) were used and received P4 , three times every 48 h and received PGF2α along with the last dose of P4. Ewe received hCG (n = 79, 3PHCG, IM) or GnRH (n = 79, 3PGnRH, IM) 24 h after the last dose of P4 treatment. In the Exp 2, lactating ewes (n = 62) received P4 and hCG (n = 24, 3PHCG) or GnRH (n = 24, 3PGnRH) similar to Exp 1, or considered as control (n = 14) and received PGF2α 48 h before ram release. Rams were released into the studied ewe's flock 24 h after the hCG or GnRH administration, and pregnancy diagnosis was performed on day 50 after ram release. In Exp 1, all reproductive indices were not significant between groups except twin lambing rate, that was higher in the 3PHCG (11.3%) compared with the 3PGnRH (1.9%) group (p = .05). There were no significant differences in overall pregnancy and lambing rates between 3PHCG (70.9% and 67.1%) and 3PGnRH (69.6% and 68.4%) groups (p > .05). In Exp 2, all reproductive parameters were not significant between 3PHCG and 3PGnRH groups (p > .05). There was significant difference in overall oestrous rate between control (35.7%) and treatment (3PHCG, 70.9% and 3PGnRH, 79.2%) groups. To conclude, administration of GnRH can be a good alternative to hCG injection under field conditions.

Reproductive efficiency of treated Karakul ewes with short-term progesterone and hCG injections during the non-breeding and breeding seasons.

The aim of this study was to evaluate reproductive efficiency of ewes following a short-term treatment with progesterone (P4) plus human chorionic gonadotropin (hCG) injections. In Exp 1, ewes (n = 65) were used during the non-breeding season and received P4, three times every other day (n = 22, 3PHCG, IM) or a single dose of P4 (n = 21, PHCG). We injected hCG in all ewes 24 h after the P4 treatment, and distilled water in control group (n = 22). Blood collection were performed on days -13, -6 and + 8 relative to ram release. In Exp 2, during the breeding season, ewes (n = 66) were assigned to the 3PHCG (n = 33) and control (n = 33) groups described for Exp 1, and subsequently received PGF2α 48 h before ram release. Pregnancy diagnosis was performed on day 42 after the ram release which was done 24 h after the hCG injection. In Exp 1, Estrus, pregnancy rate at induced estrus, and lambing rates at the first cycle were greater in 3PHCG (81.8%, 59.1% and 54.5%) group compared with the PHCG (38.1%, 23.8% and 19%) and control (0%, 0% and 0%) groups (P < 0.05). In Exp 2, Estrus, pregnancy rate at induced estrus, and lambing rates at the first cycle were greater in 3PHCG (75.8%, 57.6% and 51.5%) group compared with the control (39.4%, 30.3% and 27.3%) groups (P < 0.05). To conclude, hCG injection 24 h after P4 administration is an effective protocol to induce fertile estrus during non-breeding season, and synchronize estrus and lambing of ewe in the breeding season.

Effects of intravenous butaphosphan and cyanocobalamin to late pregnant ewes on the metabolic indices around parturition and weight gain of their lambs after birth.

BACKGROUND: Management and control of metabolic disorders in sheep around parturition is important. and various researchers have suggested different managerial solutions. Butaphosphan and cyanocobalamin are widely used for curing metabolic disorders resulting from poor nutrition, inadequate management or diseases. OBJECTIVES: It was hypothesised that butaphosphan and cyanocobalamin could improve the metabolism of ewes around parturition. METHODS: Twenty-eight clinically healthy 3-year-old pregnant Afshari ewes from 21 days before parturition were enrolled into four equal groups: control (Ctrl), B+C1, B+C2 and B+C3. The Ctrl group only received intravenous normal saline and B+C1, B+C2 and B+C3 ewes, respectively, received an intravenous combination of 10% butaphosphan and 0.005% cyanocobalamin at 2, 4 and 6 ml/ewe, on Days 19-21, 10-12 and 1-3 before parturition. Blood samples were taken from all the ewes on Days 21, 12 and 3 before lambing at parturition day and on days 3, 12 and 21 after parturition. A body condition score of all the ewes was assessed at blood sampling days, and lambs born from the ewes were weighed at birth and every 2 weeks up to 3 months. Serum concentrations of glucose, cortisol, non-esterified fatty acids, beta-hydroxy butyric acid, triglyceride, cholesterol, high-, low- and very-low-density lipoproteins, aspartate aminotransferase and alanine aminotransferase were measured. RESULTS: This drug combination decreased circulating glucose, cortisol, lipid profile and hepatic enzymes via dose-dependent manner, 6 ml of this drug compound/ewe was more potent than 4 and 2 ml/ewe. The lambs' weight from mothers receiving 6 ml of this combination was significantly higher than those of the others. CONCLUSIONS: It may be suggested that the intravenous administration of 6 ml/ewe of this combination for 3 consecutive days in three states before parturition had prophylactic effects on metabolic disorders of ewes and enhanced the lambs weight gain after birth.

Effects of Pre-ovulatory Follicular Fluid of Repeat Breeder Dairy Cows on Bovine Fertility Transcriptomic Markers and Oocytes Maturation and Fertilization Capacity.

The current study aimed to determine the effects of the preovulatory follicular fluid (FF) of normal heifer (NH) and repeat breeder cows with subclinical endometritis (SCE) or without (nSCE) on oocyte maturation (Experiment 1) and fertilization rates (Experiment 2). Moreover, the pattern of gene expression of cumulus oocyte-complexes was evaluated in Experiment 1. In Experiment 1, nuclear maturation in the nSCE group was higher, compared to that in the SCE group (P = 0.05). In addition, the oocyte nuclear maturation in the normal heifer was significantly higher, in comparison to that of SCE groups (P < 0.05). Furthermore, the mean percentage of normal oocyte fertilization was higher in the nSCE group, compared to that in the SCE group (P < 0.05). The expressions of growth differentiation factor, GDF9; steroidogenic acute regulatory, StAR and follicle-stimulating hormone receptor, FSHr in the NH group were significantly higher, compared to those in SCE and nSCE groups (P < 0.05). Moreover, the expressions of all genes in the nSCE group were not significant, in comparison to those in the SCE group (P > 0.05). The supplementation of oocyte maturation medium with FF from pre-ovulatory follicles of repeat breeder cows resulted in less oocyte maturation and cumulus cell expansion. In conclusion, the lower fertility in RB cows could be ascribed to the lower oocyte maturation rate and less expression of GDF9, StAR, and FSHr in the cumulus-oocyte complexes.

The effect of prostaglandin and gonadotrophins (GnRH and hCG) injection combined with the ram effect on progesterone concentrations and reproductive performance of Karakul ewes during the non-breeding season.

The effect of prostaglandin and gonadotrophins (GnRH and hCG) combined with the ram effect on the progesterone (P4) concentrations and reproductive performance of Karakul ewes was investigated during non-breeding season. Ewes (n = 93) received a male effect and were divided into two treatment groups including GnRH - hCG (hCG, n = 32), GnRH - GnRH (GnRH, n = 30) and a control (n = 31) group. This study was carried out from April (hormonal injection) to October (lambing). The first doses of GnRH (4.2 µg, Buserelin) were injected at the beginning of the study in treatment groups. These ewes were treated with hCG (250 IU) or the second GnRH dose five days later. All animals received two injections (ten days apart) of 150 µg PGF2α five days after the hCG or the second GnRH injection. Mating was initiated two days after the second prostaglandin injection and lasted for 34 days. Blood samples were collected by jugular venipuncture on days -10, -5, 0 (first PGF2α injection), 17 and 30 during the study. Pregnancy diagnosis was performed through transabdominal ultrasonography on day 40 after the removing of ram. Conception rate was 93.8, 90 and 87.1% in the hCG, GnRH and control groups, respectively. Lambing rate tended to increase in the hCG group compared with the control group (87.1 versus 58.1%; p < .1). There was no significant difference in P4 concentrations among studied groups in identical sampling times (p > .05). In conclusion, the administration of prostaglandin and hCG in combination with the ram effect tended to decrease lambing period. In other words this protocol tended to increase lambing rate at the first cycle. Treatment with hCG or GnRH did not increase serum P4 concentrations of treated Karakul ewes during the non-breeding season.

Effects of follicular fluid of preovulatory follicles of repeat breeder dairy cows with subclinical endometritis on oocyte developmental competence.

The aims of the present study were to determine the concentrations of lipopolysaccharide (LPS), hormonal progesterone, estradiol-17ß, insulin growth factor (IGF-1) and magnesium in the serum and the preovulatory follicle follicular fluid (FF) in repeat breeder (RB) cows without (nSCE) or with subclinical endometritis (SCE), and further to examine the effects of this FF on developmental competence of cattle oocytes. In Experiment 1, 13 of 23 clinically healthy Holstein RB cows were identified (uterine PMNs) to have SCE. The cows were estrous synchronized, and 6-12 h after detection of standing estrus, FF and blood of the preovulatory follicles were collected. The mean (±SD) LPS (862.3 ± 148.1 compared with 1063.4 ± 262.8 EU/ml, P = 0.04) and estradiol-17ß (188.9 ± 15.8 compared with 162.0 ± 31.5 ng/ml, P = 0.02) concentrations of FF was different between nSCE and SCE cows. In Experiment 2, FF of RB cows with relatively lesser (nSCE, n = 4) and greater (SCE, n = 4) percentages of uterine PMNs was separately added to the oocyte maturation medium for in vitro embryo production. Addition of FF from SCE cows to the oocyte maturation medium resulted in a lesser rate of development to the blastocyst stage than that of the nSCE cows (21.9 ± 1.8 compared with 27.8 ± 2.5%, P < 0.05). Results of the present study indicate greater FF LPS concentration may result in a lesser quality microenvironment milieu for the final stages of oocyte maturation in RB dairy cows with subclinical endometritis. In addition, supplementation of oocyte maturation medium with FF of preovulatory follicles from RB cows with subclinical endometritis resulted in a lesser potential of in vitro oocyte developmental competence.

Effects of hypertonic dextrose and paraffin solution as non-antibiotic treatments of clinical endometritis on reproductive performance of high producing dairy cows.

The objective of this study was to compare the reproductive performance of cows affected by clinical endometritis (CE) following treatment with an intrauterine infusion of 50% dextrose solutions (DEX) and liquid paraffin (LP) as alternative therapies with routine treatments including PGF2α injection and intrauterine infusion of oxytetracycline (OTC). Moreover, the reproductive indices of cows treated with endometritis were compared with those of healthy ones. At postpartum reproductive tract examination (28-35 DIM) in one Iranian dairy farm, cows with CE without any selection were assigned to four groups: (a) OTC, a common treatment in Iran, was administered (5 g) to 396 cows, (b) PGF2 α (PG) was injected to 496 cows, (c) dextrose solution (DEX): intrauterine infusion of 50% dextrose solution (200 ml) was done in 427 cows, and (d) liquid paraffin (LP) was administered (100 ml) to 423 cows via intrauterine route. We further assigned 2,233 clinically healthy cows to the control group. The incidence of endometritis was 41.6% in this study. Based on the results of reproductive indices including median days to first AI, days open (DO), first service conception rate, conception rate in 2nd and 3rd services, conception rate in all three services, pregnancy rate < 100 days and pregnancy rate < 200 days, except for median days to first AI in other reproductive indexes, reproductive performance was significantly lower in LP group compared with the healthy cows and other treatment groups (p < 0.05). Except for the first service conception rate and proportion of cows pregnant before 100 days in milk (DIM), there existed no significant difference between the DEX group and the control as far as reproductive performance is concerned (p ≥ 0.05). The first service conception rate was recognizably lower in DEX group compared with OTC and PG (p < 0.05). In conclusion, the use of a non-antibiotic special solution of dextrose 50% is a good alternative to antibiotic agents concerning the treatment of CE in dairy cows.

Characterization of polymorphism in the FSH receptor gene and its impact on some reproductive indices in dairy cows.

Follicle stimulating hormone (FSH) is released from the anterior pituitary gland and has an important role in female fertility. As FSH is a glycoprotein polypeptide hormone which cannot pass through the cell membrane, its influence on target cells must be mediated by the FSH receptor (FSHR). Accordingly, any kind of mutation in FSHR can affect reproduction in dairy cows. In this study, the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used for recognition of a point mutation (A/G: position -278) located in the FSHR gene in Iranian dairy cows. The association was evaluated of this mutation with reproductive performance. Blood samples were collected from 79 cows in a dairy farm in Iran and genotyped based on this single nucleotide polymorphism (SNP). The 5'-flanking regions of FSHR gene were successfully amplified and produced a fragment of 211bp in all cases. Three different patterns were, however, produced following restriction digestion with FaqI enzyme. The molecular results showed the existence of three different genotypes of AA, AG and GG among examined cows. In this study percentages of genotypes were 51.9%, 43.2% and 4.9% for AA, AG and GG genotypes, respectively. Allele frequencies were 73.5% and 26.5% for A and G, respectively. Results indicate that cows lacking allele G had desirable fertility in which a greater percentage (53.7%) of cows lacking Allele G (AA) had services per conception (SPC) of <2 in the previous lactation; while a lesser percentage of cows with Allele G (28.9%) had SPC of <2 (P<0.05). There was no difference in the days non-pregnant (DNP) and calving to first service interval among cows with these genotypes (P>0.05). Calving to first service interval was 69.9 ±12.3 in cows with Allele G and 74.73±13.9 in cows without Allele G (P>0.05). Percentage of cows with repeat breeder syndrome (SPC >3) was also 15.6% and 27.6% in cows without Allele G and with Allele G, respectively, but these values were not different (P>0.05). It can be concluded that the A to G mutation within the upstream region of FSHR gene (position -278) may affect some reproductive variables in Holstein dairy cows.

The effect of Zataria multiflora extract on the clinical endometritis and reproductive indices in lactating Holstein dairy cows.

In the present study, the effect of intrauterine infusion of Zataria multiflora extract on the clinical endometritis was investigated. Vaginal examination, transrectal palpation and ultrasonography were used to inspect the genital tract at 30-40 days in milk and two weeks later the same approach was applied. Cows with clinical endometritis were randomly divided into three treatment groups: Z. multiflora extract (n = 56), penicillin + streptomycin (pen + strep, n = 55), and placebo (n = 20). Cervical cytology, reagent strip test and cell counting by means of Neubauer hemocytometer were carried out in both examinations. Clinical cure rate of cows with endometritis of score 1 were 45.5, 34.5 and 53.6% in placebo, pen + strep and Z. multiflora, respectively. Clinical cure rate of cows with endometritis of score 2, 3 were 66.7, 84.6 and 56.0% in placebo, pen + strep and Z. multiflora, respectively. Overall, proportions of successfully treated cows were 55.0, 58.2 and 54.7% in placebo, pen + strep and Z. multiflora, respectively (p > 0.05). In placebo, none of the parameters were significantly different between first and second examination, while we found the significant differences in percentage of neutrophils and leukocyte esterase activity in other groups (p < 0.05). First service conception rate of cows was higher in Z. multiflora compared to other groups; however, this difference was not significant. In conclusion, pen + strep and Z. multiflora extract can be effective on the clinical endometritis and may improve reproductive performance. The extract of Z. multiflora can be useful as an alternative therapy for treatment of clinical endometritis in lactating dairy cows.

Relationship between season, lactation number and incidence of clinical mastitis in different stages of lactation in a Holstein dairy farm.

The aim of the present study was to compare the occurrence and duration of clinical mastitis in different seasons, stages of lactation period and parities in a Holstein dairy farm in Iran. A retrospective epidemiological survey from April 2005 to March 2008 was conducted on 884 clinical mastitis cases of 7437 lactations. Data of each case including calendar-date of mastitis onset, days in milk (DIM) of mastitis onset (early: 0-74 DIM; middle: 75-150 DIM, and late ≥ 150 DIM), duration of mastitis, and parity (1, 2, and ≥ 3) were recorded. Based on date of mastitis onset, cases were classified into stages of lactation. Moreover, beginning of mastitis was seasonally categorized. Duration of clinical mastitis after treatment in early lactation was less than late lactation in the first-parity cows (p = 0.005). In early lactation period, the first-parity cows suffered clinical mastitis in days earlier than two other parity groups (p < 0.001). Moreover, in late lactation period, the first-parity cows had clinical mastitis in days later than cows in the third and more parities (p = 0.002). Occurrence of clinical mastitis in summer increased in late lactation period but in winter increased in early lactation period (p = 0.001). In addition, occurrence time of clinical mastitis in summer were in days later than in spring (p = 0.02) and winter (p = 0.03) in early lactation period. In conclusion, occurrence of mastitis in winter and spring during early lactation and in summer during late lactation period were more prevalent especially in lower parities.

Luteal activity of Abadeh ecotype does in summer and winter and the effect of kisspeptin-10 on luteinizing hormone secretion in the anestrus does.

The aims of the present study were to evaluate luteal activity in Abadeh ecotype goat during summer and winter and also the effect of a single dose kisspeptin-10 injection on the secretion of luteinizing hormone (LH) in female anestrous goats. In the first study, progesterone (P4) concentration in 10 goats in summer (n = 6) and winter (n = 4) were measured every other day. Moreover, in summer group, a male teaser goat was left in the herd on days of sampling for one hour. Goats with P4 concentration ≥1 ng mL(-1), at least two consecutive measurements, were considered with luteal activity. In the second study, the anestrous phase was confirmed by P4 measurement 20 and 10 days before the kisspeptin injection in five female Abadeh ecotype goats (4 to 5 years old). The goats were given a single IV injection of saline (2 mL) as control group and the same goats (1 hr after the last blood sampling) were given kisspeptin (1 µg kg(-1)) as treatment group. The blood samples were collected at -60, -40, -20 and 0 min (before injection), and 10, 20, 30, 40, 50, 60, 80, 100, 120 and 140 min after the injection and LH concentration were measured. A single IV injection of 1 µg kg(-1) of kisspeptin-10 did not stimulate the release of LH in female anestrous goats. In summer, in the presence of teaser goat, luteal activity was seen in all goats. In the absence of male goat in winter, some goats showed luteal activity and others showed anestrus.

Characterization of single nucleotide polymorphism in the 5'-untranslated region (5'-UTR) of Lactoferrin gene and its association with reproductive parameters and uterine infection in dairy cattle.

Uterine infection is one of the reproductive diseases that can have disturbing postpartum uterine health in cattle. Therefore, identification of resistant genotypes to uterine infection is important. Lactoferrin (LF) is one of the major antimicrobial compounds in the normal uterine discharges of cows. We hypothesized that allelic diversity in LF gene may contribute to susceptibility or resistance to uterine infection. We investigated the single nucleotide polymorphism genes identified in the 5' untranslated region (5'-UTR, position +32) of the LF gene using Allele-specific PCR method in cows with and without uterine infection. Blood samples were collected from 89 multiparous Holstein dairy cows with a history of uterine infection (n = 51), and cows without disease as the control group (n= 38). The results indicated the presence of different proportion of polymorphisms (G > C) in the 5'-UTR area of cows in the all groups. The results of Allele specific PCR was in complete agreement with sequencing method. Statistical analysis did not show any statistically significant correlation between disease and SNP in 5'-UTR. While, there was a significant difference in the mean of reproductive parameters of cows without polymorphism compare to those of with SNP in 5'-UTR. Cows with +32:CC genotype and +32:GC genotype (cows with SNP in UTR) had lower average of services per conception and days open compared to cows with the +32:GG genotypes. However, no significant difference in the calving to first service was found between these genotypes. Further studies will be required to determine critical SNPs in LF gene and status of the risk of uterine infection and embryo survival in cows.

Factors affecting the occurrence of postpartum prolonged luteal activity in clinically healthy high-producing dairy cows.

The objective was to characterize risk factors affecting the occurrence of prolonged luteal phase (PLP) in postpartum, clinically healthy, high-producing dairy cows. Transrectal ultrasound examinations of the reproductive tract were performed twice weekly, from the 1st to 8th wk after calving in 151 multiparous clinically healthy lactating Holstein cows (mean ± SD of peak milk yield = 56.7 ± 7.4 kg). Serum samples were collected twice weekly to measure progesterone and every 2 wk to detect ß-hydroxybutyrate (ßHB), and α1-acid glycoprotein (AGP). Body condition score (BCS) was recorded weekly after calving. Based on the serum progesterone profile, 52 (34.4%) cows had normal ovarian activity (NLA), whereas 36 (23.8%) cows had a prolonged luteal phase (PLP), the most prevalent type of abnormal pattern of luteal activity. Furthermore, 63 cows with short luteal activity, delayed first ovulation, or cystic ovaries were excluded from this study. Serum AGP concentrations, as an indication of postpartum chronic endometritis, were not different (P > 0.05) between cows with NLA and PLP. Categories of peak milk yields (kg) were positively correlated with the incidence (%) of cows with PLP (r = 0.87, P = 0.02). Furthermore, milk yield peak, day of milk yield peak, mean milk yield (8 wk in milk), and milk yield on the expected day of luteolysis were higher (P < 0.05) in cows with PLP than NLA, and cows with PLP had greater loss of BCS (P = 0.007) than those with NLA. The likelihood of cows with PLP decreased by 0.9-fold for every 1 d delay of commencement of luteal activity (C-LA). Moreover, the likelihood of cows with PLP increased by 1.8-fold for each 1 mmol/L increase in the 1st wk serum ßHB concentrations. In conclusion, higher mean of milk yield, greater BCS loss, earlier C-LA, and later peak milk yield were the major risk factors affecting the occurrence of postpartum PLP in clinically healthy, high-producing dairy cows.

Relationships between insulin-like growth factor-I, milk yield, body condition score, and postpartum luteal activity in high-producing dairy cows.

The relations between body condition score (BCS), milk yield, serum insulin-like growth factor-I (IGF-I) profile, and luteal activity were investigated in postpartum dairy cows. Seventy-one healthy high-producing multiparous Holstein cows were subjected to transrectal ultrasound scanning twice weekly from the first to the eighth week postpartum. Blood samples were collected twice weekly to measure serum progesterone (P4) and every 2 weeks to detect serum IGF-I concentrations. BCS was monitored weekly after calving. Cows with serum P4 concentrations ≥1 ng/ml on at least two consecutive samplings were considered to have commenced luteal activity. Commencement of luteal activity (C-LA) was observed earlier than 45 days postpartum in 71.8% of cows while 28.2% showed C-LA later than 45 days. Prolonged luteal phase was the most common abnormal pattern of luteal activity observed. Cows with a C-LA earlier than 45 days postpartum had higher (P ≤ 0.05) mean serum concentrations of IGF-I than those with later C-LA. In addition, cows which showed C-LA earlier than 45 days postpartum had more optimal productive indices including shorter calving to conception interval and calving to first service interval (P ≤ 0.05), and fewer services per conception (P = 0.07). C-LA was significantly later in cows that lost more than 0.5 BCS units within 3 weeks postpartum than in those that lost less than 0.5 units BCS during the same interval (P = 0.02). We conclude that high-producing dairy cows with higher postpartum serum IGF-I concentrations have earlier commencement and normal luteal activity, and better reproductive performance. Severity and duration of BCS loss adversely affect commencement of luteal activity.

Effects of first postpartum progesterone rise, metabolites, milk yield, and body condition score on the subsequent ovarian activity and fertility in lactating Holstein dairy cows.

Seventy multiparous healthy lactating Holstein cows (fat-corrected milk yield = 7,561.8 kg) were monitored from 14 days before to 70 days after calving. Transrectal ultrasound scanning was performed twice weekly from 7 to 65 days postpartum. Blood samples were also collected twice weekly to measure serum P(4) and biweekly to detect serum beta-hydroxybutyrate (betaHB) and nonesterified fatty acid (NEFA) concentrations. Body condition score (BCS) was taken biweekly after calving. Based on the serum P(4) profile of 59 cows (11 cows were excluded due to the occurrence of postpartum diseases) studied, 27 (45.8%) had normal ovarian activity, while 21 (35.6%), six (10.1%), three (5.1%), and two (3.4%) had delayed ovulation (DOV), prolonged luteal phase (PLP), short luteal phase (SLP), and cessation of ovarian activity, respectively. Cows with PLP had an earlier ovulation compared to that of cows with normal ovarian activity (23.16 +/- 4.02 vs 31.9 +/- 8.35 days; P < 0.05). PLP cows also had a greater mean +/- standard deviation peak milk yield (44.2 +/- 5.8 vs 37.2 +/- 5.7 kg/day, 75 days postpartum; P < 0.05) than cows with normal postpartum ovarian activity. The PLP group also had greater milk production in the previous lactation period. Logistic regression analysis indicated that cows with P(4) concentration > or =1 ng/ml on day 24 after calving were more at risk for PLP by 1.1 for each 1 kg increase in mean peak milk yield during 75 days after calving. BCS was lower in cows with DOV compared to that of cows with normal ovarian activity at any time after calving (P < 0.05). Serum betaHB concentrations in DOV cows were significantly higher than that of normal cows on day 42 after calving (0.69 +/- 0.29 vs 0.54 +/- 0.12 mmol/L, P < 0.05). No significant difference was found in the mean concentrations of NEFA between cows in different groups at any time after calving (P > 0.05). The concentrations of P(4) on days 28 and 31 were negatively correlated with betaHB concentration on day 42 after calving in cows with normal ovarian activity (R = -0.44, P = 0.02). In conclusion, these findings suggest that early ovulation and hence early postpartum P(4) rise in addition to the high milk production could partly be responsible for the occurrence of PLP in dairy cows.