Short communication: A reproductive tract scoring system to manage fertility in lactating dairy cows.

We developed a reproductive tract size and position score (SPS) system as a reproductive management tool to identify lactating dairy cows with decreased fertility. This system, relying solely on transrectal palpation, considers the size (cervical and uterine) and position of the reproductive tract relative to the pelvis. Cows undergoing pre-breeding exams were identified as having reproductive tracts that were small (SPS1), medium (SPS2), or large (SPS3). Cows designated SPS1 had small and compact uterine horns that rested within the pelvic cavity; SPS2 cows had reproductive tracts that were intermediate in cervical and uterine horn diameter, with longer uterine horns resting partially outside the pelvic cavity; and SPS3 cows had reproductive tracts that were larger and rested mostly outside the pelvic cavity. Cows that were SPS1 had a higher rate of pregnancy per artificial insemination (43.3 ± 3.7%) than cows that were SPS2 (36.9 ± 3.6%) or SPS3 (27.7 ± 4.3%). The percentage of cows with an SPS2 score differed in pregnancies per artificial insemination compared with SPS3 cows. The average days in milk was similar for SPS1, SPS2, and SPS3 cows (104.3 ± 3.5, 98.4 ± 3.4, and 94.7 ± 7.7, respectively). Ultrasound measurements of the uterine horn and cervical diameter, and length measurements of the uterine horns, cervix, and vagina confirmed differences among the SPS groups derived by transrectal palpation. The ease with which transrectal palpation can be used to determine the size and position of the reproductive tract attests to the relevance and usefulness of this scoring system to identify less fertile lactating dairy cows. The ability to do so with ease provides an opportunity to make economically relevant management decisions and maximize reproductive efficiency in a given herd.

A polymorphism in XKR4 is significantly associated with serum prolactin concentrations in beef cows grazing tall fescue.

Fescue toxicosis is a common syndrome of poor growth and reproductive performance of beef cattle grazing endophyte-infected tall fescue infected with Lolium arundinaceum Schreb. Together with decreased feed intake, decreased growth rates and tissue necrosis due to vasoconstriction, depressed circulating serum prolactin concentrations are typically observed in cattle afflicted with fescue toxicosis. Polymorphisms within the XK, Kell blood group complex subunit-related family, member 4 (XKR4) gene located on BTA14 have been previously reported to be associated with rump fat thickness, residual feed intake, average daily feed intake and average daily gain in cattle. Associations also have been reported between XKR4 genotype and effectiveness of the dopamine antagonist iloperidone as a treatment of schizophrenia in humans. Domperidone, a related dopamine antagonist, mediates effects of fescue toxicosis on livestock, including restoring depressed concentrations of prolactin. A mixed-breed population of 592 beef cattle grazing endophyte-infected tall fescue was used to examine the association between XKR4 genotype and circulating prolactin concentrations. The SNP rs42646708 was significantly (P = 0.0002) associated with serum prolactin concentrations and explained 2.45% of the phenotypic variation. Effect of genotype at the SNP was tested across five breeds, with significant associations within both Angus (P = 0.0275) and Simmental (P = 0.0224) breeds. These results suggest XKR4 may play a role in mediating the negative effects of fescue toxicosis, and polymorphisms within this gene may be useful markers for selection for genetic resistance to the debilitating effects of endophyte-infected tall fescue.

A single nucleotide polymorphism in the dopamine receptor D2 gene may be informative for resistance to fescue toxicosis in angus-based cattle.

Fescue toxicosis (FT) reduces beef animal growth and fertility. Animals afflicted with FT typically have decreased circulating prolactin concentrations and thicker summer hair coats. Preliminary experiments examined the informativeness of a novel Dopamine Receptor 2 (DRD2) G/A SNP for resistance to FT. Steers grazed tall fescue containing a toxic (E+) or non-toxic (NTE) strain of endophyte. Decreased serum prolactin concentrations were observed in GG steers in May compared to AA steers when grazing E+ pastures (P < 0.02). In a second study, GG steers had decreased prolactin concentrations (P = 0.004) and increased hair coat scores (P = 0.01) relative to AA steers when grazing E+ pastures. Allele and genotypic frequencies were different (P = 0.016 and 0.026, respectively) between spring-calving and fall-calving herds grazing E+ pastures, such that the A allele and the AA genotype were more prevalent in spring-calving herds, suggesting active selection for the A allele. Regardless of calving season, AA heifers tended toward fewer days to first calf (733.6 ± 4.4 d) than did GG heifers (756.6 ± 9.2 days; P = 0.055). These results suggest that the DRD2 SNP may have use in selecting animals resistant to FT.

Heat stress effects on the cumulus cells surrounding the bovine oocyte during maturation: altered matrix metallopeptidase 9 and progesterone production.

When the effects of heat stress are detrimental during maturation, cumulus cells are intimately associated with the oocyte. To determine the extent to which heat stress affects these cells, in this study, transcriptome profiles of the cumulus that surrounded control and heat-stressed oocytes (41 °C during the first 12 h only and then shifted back to 38.5 °C) during in vitro maturation (IVM) were compared using Affymetrix bovine microarrays. The comparison of cumulus-derived profiles revealed a number of transcripts whose levels were increased (n=11) or decreased (n=13) ≥ twofold after heat stress exposure (P<0.01), sufficient to reduce the development of blastocysts by 46.4%. In a separate study, quantitative PCR (qPCR) was used to confirm heat-induced differences in the relative abundances of the transcripts of five different genes (caveolin 1, matrix metallopeptidase 9, FSH receptor, Indian hedgehog homolog, and inducible nitric oxide synthase). Heat stress exposure resulted in >1.7-fold decrease in the protein levels of latent matrix metallopeptidase 9 (proMMP9). Heat-induced reductions in transcript levels were noted at 6 h IVM with reductions in proMMP9 protein levels at 18 h IVM (P=0.0002). Independent of temperature, proMMP9 levels at 24 h IVM were positively correlated with the development rate of blastocysts (R²=0.36; P=0.002). The production of progesterone increased during maturation; heat-induced increases were evident by 12 h IVM (P=0.002). Both MMP9 and progesterone are associated with the developmental competence of the oocyte; thus, it seems plausible for some of the negative consequences of heat stress on the cumulus-oocyte complex to be mediated through heat-induced perturbations occurring in the surrounding cumulus.

Disparate consequences of heat stress exposure during meiotic maturation: embryo development after chemical activation vs fertilization of bovine oocytes.

Consequences of heat stress exposure during the first 12 h of meiotic maturation differed depending on how and when bovine oocytes were activated. If heat-stressed oocytes underwent IVF at ~24 h, blastocyst development was less than for respective controls and similar to that obtained for nonheat-stressed oocytes undergoing IVF at 30 h (i.e. slightly aged). In contrast, if heat-stressed oocytes underwent chemical activation with ionomycin/6-dimethylaminopurine at 24 h, blastocyst development was not only higher than respective controls, but also equivalent to development obtained after activation of nonheat-stressed oocytes at 30 h. Developmental differences in chemically activated vs IVF-derived embryos were not related to fertilization failure or gross alterations in cytoskeletal components. Rather, ionomycin-induced calcium release and MAP kinase activity were less in heat-stressed oocytes. While underlying mechanisms are multifactorial, ability to obtain equivalent or higher development after parthenogenetic activation demonstrates that oocytes experiencing heat stress during the first 12 h of meiotic maturation have the necessary components to develop to the blastocyst stage, but fail to do so after fertilization.

Size and position of the reproductive tract impacts fertility outcomes and pregnancy losses in lactating dairy cows.

There are multiple factors that contribute to reduced fertility in lactating dairy cows. Recently, a reproductive tract size and position score (SPS) system was developed as a management tool to identify dairy cows with decreased fertility. The aim of this study was to evaluate the association between the SPS on fertility outcomes such as ovulation failure, pregnancy per artificial insemination (P/AI), concentration of pregnancy-associated glycoproteins (PAGs), and pregnancy loss in lactating dairy cows. Primiparous and multiparous lactating Holstein cows (n = 869) were enrolled at two locations. Location 1 (Loc. 1) in Minas Gerais, Brazil (n = 613) and location 2 (Loc. 2) in Agassiz, British Columbia, Canada (n = 256). At the time of AI (d 0), cows were classified as SPS (small [SPS1], medium [SPS2], or large [SPS3] sized reproductive tract) and ovulation failure was determined at 48 h and 7 d post-AI via ultrasonography (Loc. 2 only). Blood samples were collected on d 24 and 31 of gestation for quantification of PAGs and pregnancy diagnosis was performed via ultrasonography at d 31 and 60 post-AI (Loc. 1) and at d 31 ± 3 and 60 ± 3 post-AI (Loc. 2). Cows diagnosed pregnant at d 31 post-AI but not pregnant at d 60 were defined to have undergone late embryonic pregnancy loss. Parity was found to impact SPS (P < 0.01), as primiparous cows had a higher frequency of SPS1 and lower frequency of SPS3 when compared with multiparous cows (SPS1: 42.6 vs. 15.0%; SPS3: 7.0 vs. 22.0%, respectively). Cows classified as SPS3 had greater ovulation failure at 48 h (P = 0.04) and 7 d post-AI (P = 0.05). Cows classified as SPS1 had greater P/AI when compared to SPS2 and SPS3 (45.9 ± 3.3 vs. 37.4 ± 2.6 and 29.1 ± 3.5%, respectively; P = 0.004). There was no interaction between parity and SPS on P/AI. Pregnancy loss between 31 and 60 d post-AI was increased in cows classified as SPS3 compared to SPS2 and SPS1 (24.3 ± 0.05 vs. 11.6 ± 0.02 and 9.4 ± 0.02%, respectively; P = 0.04). Cows classified as SPS1 and SPS2 had greater concentrations of PAGs at 31 d post-AI when compared to SPS3 at both Loc.1 (P < 0.01) and Loc. 2 (P < 0.01). There was no interaction between SPS and pregnancy loss on PAGs at 24 and 31 d post- AI for either Loc. 1 (P = 0.75 and P = 0.76, respectively) or Loc. 2 (P = 0.61 and P = 0.81, respectively). In conclusion, cows that were classified as SPS3 had greater ovulation failure, reduced P/AI, similar concentrations of PAG on d 24, but decreased on d 31, and a greater incidence of pregnancy loss. Thus, size and position of the reproductive tract is associated with fertility and this scoring system could be used to make reproductive management decisions on dairy operations.

Developmental competence of bovine embryos from heat-stressed ova.

Because multiple ovulation embryo transfer procedures are occasionally performed in cows experiencing heat stress, the goal of this study was to assess the developmental competence of otherwise morphologically normal embryos from heat-stressed ova. To this end, the ability of compact morulae from heat-stressed and non-heat-stressed bovine ova to undergo blastocyst development after culture at 38.5 or 41.0 degrees C was examined. It was hypothesized that heat-induced perturbations in the ooplasm carry over to increase the susceptibility of the preattachment embryo to heat stress. Initially, ova were matured at 38.5 or 41.0 degrees C. The consequences of heat stress did not include altered cleavage, but did reduce the proportion of 8- to 16-cell-stage embryos (55.3 vs. 50.6%; SEM +/- 1.9). Although proportionately fewer, compact morulae from heat-stressed ova were equivalent in quality to those from non-heat-stressed ova (2.1 and 2.1; SEM = 0.04). Culture of compact morulae from non-heat-stressed ova at 41.0 degrees C did not affect blastocyst development (71.9 and 71.5%; SEM = 3.0). Furthermore, the development of compact morulae from heat-stressed ova was similar to that of non-heat-stressed ova after culture at 38.5 degrees C (68.2 vs. 71.9 and 71.5%; SEM = 3.0). However, blastocyst development was reduced when compact morulae from heat-stressed ova were cultured at 41.0 degrees C (62.3 vs. 71.9, 71.5 and 68.2; SEM = 3.1). In summary, reduced compaction rates of heat-stressed ova explained in part why fewer develop to the blastocyst stage after fertilization. The thermolability of the few embryos that develop from otherwise developmentally challenged ova emphasizes the importance of minimizing exposure to stressor(s) during oocyte maturation.

Ergot alkaloid exposure during gestation alters. I. Maternal characteristics and placental development of pregnant ewes1.

Tall fescue [Lolium arundinaceum (Scheyreb.) Darbysh] is the primary cool season forage grass in the Southeastern United States. Most tall fescue contains an endophytic fungus (Epichloë coenophiala) that produces ergot alkaloids and upon ingestion induces fescue toxicosis. The objective of this study was to assess how exposure to endophyte-infected (E+; 1.77 mg hd-1 d-1 ergovaline and ergovalinine) or endophyte-free (E-; 0 mg hd-1 d-1 ergovaline and ergovalinine) tall fescue seed fed during 2 stages of gestation (MID, days 35-85/LATE, days 86-133) alters placental development. Thirty-six, fescue naïve Suffolk ewes were randomly assigned to 1 of 4 fescue treatments: E-/E-, E-/E+, E+/E-, or E+/E+. Ewes were individually fed the same amount of E+ or E- seed mixed into total mixed ration during MID and LATE gestation. Terminal surgeries were conducted on day 133 of gestation. Ewes fed E+ fescue seed had elevated (P < 0.001) ergot alkaloid excretion and reduced (P < 0.001) prolactin levels during the periods when fed E+ seed. Ewes switched on day 86 from E- to E+ seed had a 4% reduction (P = 0.005) in DMI during LATE gestation, which translated to a 2% reduction (P = 0.07) in DMI overall. Average daily gain was also reduced (P = 0.049) by 64% for E-/E+ ewes during LATE gestation and tended to be reduced (P = 0.06) by 33% overall. Ewes fed E+ seed during LATE gestation exhibited a 14% and 23% reduction in uterine (P = 0.03) and placentome (P = 0.004) weights, respectively. Caruncle weights were also reduced by 28% (P = 0.003) for E-/E+ ewes compared with E-/E- and E+/E-. Ewes fed E+ seed during both MID and LATE gestation exhibited a 32% reduction in cotyledon (P = 0.01) weights, whereas ewes fed E+ seed only during MID gestation (E+/E-) had improved (P = 0.01) cotyledon weights. The percentage of type A placentomes tended to be greater (P = 0.08) for E+/E+ ewes compared with other treatments. Other placentome types (B, C, or D) did not differ (P > 0.05). Total fetal weight per ewe was reduced (P = 0.01) for ewes fed E+ seed during LATE gestation compared with E-; however, feeding E+ seed during MID gestation did not alter (P = 0.70) total fetal weight per ewe. These results suggest that exposure to ergot alkaloids during LATE (days 86-133) gestation has the greatest impact on placental development by reducing uterine and placentome weights. This, in turn, reduced total fetal weight per ewe by 15% in ewes fed E+ seed during LATE gestation (E-/E+ and E+/E+).

Alteration in testicular cell components following transiently induced ischaemia in prepubertal bulls.

The aim of the present study was to evaluate transient testicular ischaemia (induced using elastrator bands) in Jersey calves on testicular morphology and development. Treatments (at 27 +/- 5 days of age) consisted of control (0 h banding) and banding for 2, 4 or 8 h (n = 4 in each group). After castration (at 60 +/- 5 days of age), the right testis was used for calculation of cell components per testis according to the point-counting method. Bodyweight (59.8 +/- 6.2 kg) and scrotal circumference (SC) at banding (9.1 +/- 0.2 cm) did not differ between groups. Fresh testis weight, scrotal temperature immediately before band removal and daily SC growth were decreased in ischaemic (4 and 8 h) testes compared with controls (P < 0.05). In addition, the number of Sertoli and Leydig cells was significantly reduced in the 8 h ischaemic treatment group (P < 0.05). Transiently induced ischaemia significantly decreased the number of germ cells in the 8 h ischaemic treatment group (13 +/- 5 x 10(6) cells) compared with the 0, 2 and 4 h ischaemic treatment groups (38 +/- 6, 32 +/- 6 and 33 +/- 5 x 10(6) cells, respectively; P < 0.05). These results suggest that transiently induced ischaemia for 8 h significantly decreases the number of germ, Sertoli and Leydig cells in prepubertal testis.

Assessment of semen quality and fertility in young growing beef bulls exposed to ergot alkaloids.

The objective of this study was to evaluate semen quality and fertility in beef bulls grazing the ergot alkaloid (EA) producing tall fescue cultivar, Kentucky 31 (KY31), compared to a novel endophyte (NE) cultivar lacking EA. Two studies were conducted over a 3-year period. In studies 1 (n = 10; ages ≥ 24 mo) and 2 (n = 53 over two years; ages 12-16 mo), Angus (AN) bulls were stratified by body weight (BW), body condition score (BCS), and scrotal circumference (SC), and then allotted to graze either KY31 or NE for 56 days. Semen samples were collected, and BW, BCS, and SC were evaluated at the start of treatment (TRT) on day (d) 0 and every 28 days to the end of each study. In addition, blood samples were collected on d 0 and every 28 days for assessment of circulating prolactin (PRL) levels in study 2. On d 56, for both studies, semen from bulls (n = 2 per treatment in study 1 and n = 4 per treatment in study 2) with similar and acceptable quality were extended, kept at 19° C, and used for timed artificial insemination (TAI) of primi- and multiparous AN and AN- crossbred females. Pregnancy was evaluated at 35 and 90 days post-TAI via transrectal ultrasonography to determine pregnancy rates. Serum PRL concentrations showed a TRT by d effect (P ≤ 0.05), with values for bulls grazing KY31 decreased on d 28 and d 56 of grazing compared to NE. In studies 1 and 2, bull BW and BCS were affected by d (P ≤ 0.05), but not by TRT. No TRT or TRT by d effect on semen quality was observed in either study; however, d impacted both velocity and concentration in study 2 (P ≤ 0.05). In study 1, TAI pregnancy rates at 35 days post-TAI were lower (P ≤ 0.05) in the group inseminated with semen from bulls grazing KY31; however, in study 2, pregnancy rates did not differ due to treatment 35 post-TAI (P > 0.05). Grazing KY31 negatively impacted serum PRL concentrations, supporting previous observations; however, consumption of KY31 had no effect on growth or semen quality of AN bulls ranging from 12 to ≥24 mo of age. Furthermore, fertility data is inconsistent between studies and requires further investigation.

Changes in the testis seminiferous tubules and interstitium in prepubertal bull calves immunised against inhibin at the time of gonadotropin administration.

The aim of the present study was to evaluate the effects of gonadotropin administration at initiation of inhibin passive immunisation in Jersey bull calves (age 27 +/- 5 days) on testicular morphology and development. Primary treatments consisted of control (keyhole limpet haemocyanin, KLH; n = 9) or immunisation against inhibin (INH; n = 9). Subsets of calves were randomly assigned within primary treatments (TRT) to receive saline ( n = 3 per TRT), follicle-stimulating hormone (FSH; n = 3 per TRT) or gonadotrophin-releasing hormone (GnRH, n = 3 per TRT). The right testis was removed (age 118 +/- 5 days) to determine volumes of testicular components and cell numbers per testis using stereology. Data were analysed using the MIXED procedure of the SAS program. Antibody titres against inhibin were increased in INH bulls compared with KLH bulls (P < 0.05). In addition, a significant immunisation x hormone treatment interaction was noted for the number of germ cells. Administration of FSH at the time of initial immunisation against inhibin significantly increased the number of germ cells (92.2 +/- 9 x 10(6) cells) compared with INH+saline bulls (54.9 +/- 10 x 10(6) cells), with INH+GnRH bulls having an intermediate number of cells (64.5 +/- 9 x 10(6) cells; P < 0.05). These results suggest that gonadotropin administration at the time of inhibin immunisation increases the number of germ cells in the testis.

Early in vitro fertilization improves development of bovine ova heat stressed during in vitro maturation.

The objectives were to examine the development of embryos derived from control (38.5 degrees C) or heat-stressed ova [41.0 degrees C during the first 12 h of in vitro maturation (hIVM)] when in vitro fertilization (IVF) was performed at 16, 18, 20, 24, or 30 hIVM. Effects of heat stress in compromising ovum development depended on when IVF was performed (in vitro maturation temperature x IVF time interaction). When IVF was performed at 24 or 30 hIVM, fewer heat-stressed ova developed to the blastocyst stage compared with the respective controls. In contrast, when IVF was performed at 16, 18, or 20 hIVM, more heat-stressed ova developed to the blastocyst stage compared with the respective controls. Performing IVF earlier than usual was beneficial, because the ability of heat-stressed ova to develop to the blastocyst stage was improved when IVF was performed at 18 or 20 vs. 24 hIVM. Blastocyst stage and quality were equivalent to non-heat-stressed controls regardless of IVF time. Control ova undergoing IVF at 20, 24, 30, or 32 hIVM and heat-stressed ova undergoing IVF at 16, 18, 20, or 24 hIVM were compared for blastocyst development by multisource regression. Although linear and quadratic slopes were similar, heat stress reduced the peak and shifted the developmental response of ova by 7.3 h. In other words, obtaining optimal blastocyst development from heat-stressed ova would depend on performing IVF at 19.5 hIVM compared with 26.7 hIVM for non-heat-stressed controls. Heat-induced reductions in peak blastocyst development significantly reduced the window of time available to perform IVF and obtain > or = 20% blastocyst development. In summary, results support an effect of heat stress to hasten developmentally important events during oocyte maturation. The inability of earlier IVF to fully restore the development of heat-stressed ova to that of non-heat-stressed controls highlights the importance of further study.

Influence of a prostaglandin synthesis inhibitor administered at embryo transfer on pregnancy rates of recipient cows.

Elevated uterine luminal concentrations of prostaglandin F(2alpha) (PGF(2alpha)) have been negatively associated with embryo quality and pregnancy rates. Two studies were performed in cows to determine PGF(2alpha) release from uterine endometrium following embryo transfer and to investigate administration of flunixin meglumine (FM), a prostaglandin synthesis inhibitor, on pregnancy rates following embryo transfer. In Experiment 1, blood samples were collected prior to and after embryo transfer from the posterior vena cava via saphenous vein cannulation. Serum profiles of PGF(2alpha) indicated that manipulation of the reproductive tract during embryo transfer was followed by increased release of PGF(2alpha) from the uterine endometrium. In Experiment 2, estrus (day=0) was synchronized in recipient animals and a single embryo transferred 7 days after estrus. At the time of non-surgical embryo transfer, animals were randomly assigned to receive either FM (FM; n=1300) or remain untreated (control (CON); n=797). Data collected at transfer included stage of embryo development, embryo quality, technician, and transfer quality score. Overall pregnancy rates of cows receiving FM (65%) were higher than control cows (60%; P<0.02). Pregnancy rates following transfer of quality 1 (good) embryos did not differ (P>0.05) between treatments. However, pregnancy rates of quality 2 (fair) embryos were higher in animals receiving FM than in CON (P<0.01). Moreover, pregnancy rates of transferred morula- and blastocyst-stage embryos were higher in FM-treated than in controls (P<0.06 and P<0.04, respectively). In conclusion, uterine release of PGF(2alpha) is elevated following embryo transfer and administration of a PGF(2alpha) synthesis inhibitor at the time of embryo transfer improved pregnancy rates in cows.

Fertility aspects in yearling beef bulls grazing endophyte-infected tall fescue pastures.

During a 2-year study, yearling beef bulls were used to determine the effects of grazing on endophyte-infected tall fescue on endocrine profiles, semen quality and fertilisation potential. Bulls were allotted to graze tall fescue pastures infected with Neotyphodium coenophialum (E+; n = 20 per year) or Jesup/MaxQ (Pennington Seed, Atlanta, GA, USA; NTE; n = 10 per year). Bulls were grouped by scrotal circumference (SC), bodyweight (BW), breed composites and age to graze tall fescue pastures from mid-November until the end of June (within each year). Blood samples, BW, SC and rectal temperatures (RT) were collected every 14 days. Semen was collected from bulls every 60 days by electroejaculation and evaluated for motility and morphology. The developmental competence of oocytes fertilised in vitro with semen from respective treatments was determined. Bulls grazing E+ pastures had decreased BW gain (P < 0.01), increased overall RT (P < 0.01) and decreased prolactin (P < 0.01) compared with animals grazing NTE pastures. Neither percentage of normal sperm morphology nor motility differed between bulls grazed on the two pasture types. Semen from E+ bulls demonstrated decreased cleavage rates (P = 0.02) compared with semen from NTE bulls. However, development of cleaved embryos to the eight-cell and blastocyst stages did not differ between the two groups. In conclusion, semen from bulls grazing E+ tall fescue resulted in decreased cleavage rates in vitro, which may lower reproductive performance owing to reduced fertilisation ability.

Effects of induced clinical mastitis during preovulation on endocrine and follicular function.

The objective of the study was to determine if experimentally induced clinical mastitis before ovulation resulted in alterations of endocrine function, follicular growth, or ovulation. On d 8 (estrus = d 0), cows were challenged (TRT; n = 19) with Streptococcus uberis or were not challenged (control; n = 14). Forty-eight hours after induction of luteal regression on d 12, blood samples were collected to determine estradiol-17beta, LH pulse frequency, and occurrence of the LH surge. Ovaries were scanned to monitor follicular growth and ovulation. Cows with clinical mastitis (n = 12) had elevated rectal temperatures, somatic cell counts, and mammary scores. Estrus and ovulation occurred in 4 of 12 clinically infected cows and in all control cows. Cows that were challenged but did not develop clinical mastitis (n = 5) displayed estrus and ovulated. Due to differences in expression of estrus, cows were further subdivided for analyses into 4 groups: control, TRT-EST (infected cows that displayed estrus; n = 4), TRT-NOEST (infected cows that did not display estrus; n = 8), and NOMAS (cows that were inoculated but did not develop mastitis; n = 4). Ovulation rate was 100% for CON, NOMAS, and TRT-EST compared with 0% for TRT-NOEST cows. Size of the ovulatory follicle ("presumed" ovulatory follicle in TRT-NOEST cows) was similar for all groups. Frequency of LH pulses was decreased in TRT-NOEST compared with CON, TRT-EST, and NO-MAS. Estradiol-17beta increased over time in CON, NO-MAS, and TRT-EST cows, but did not increase in TRT-NOEST cows. Cows with clinical mastitis may exhibit estrus and ovulate normally or have disruptions in normal physiology including decreased LH pulsatility, absence of an LH surge and estrous behavior, suppressed estradiol-17beta, and failure to ovulate.

Identification of bovine prolactin in seminal fluid, and expression and localization of the prolactin receptor and prolactin-inducible protein in the testis and epididymis of bulls exposed to ergot alkaloids.

The objectives of this study were to determine (1) the presence and expression levels of bovine prolactin receptor (PRLR) and prolactin-inducible protein (PIP) in bovine testis and epididymis, and (2) the presence and concentrations of prolactin (PRL) present in seminiferous fluid in bulls consuming diets with (E+) or without (E-) ergot alkaloids. Bulls (n = 8) were sacrificed after 126 days (group A) of E+ or E- treatment or 60 days after all bulls (n = 6) were switched to the E- ration (group B). End point and real-time quantitative reverse transcription-polymerase chain reaction and immunohistochemistry were conducted on testis and epididymis samples to establish the presence and relative expression of PRLR and PIP. Seminal fluid samples obtained from bulls consuming E- and E+ diets were subjected to RIA for PRL. Both PIP and PRLR were present in testis and epididymis as determined by reverse transcription-polymerase chain reaction and immunohistochemistry. Prolactin-inducible protein mRNA abundance was affected by time of slaughter in testis and epididymis head, respectively (P < 0.05). Prolactin receptor mRNA expression was affected by time of slaughter in the epididymis (P < 0.05) and differed in testis samples because of treatment (P < 0.05). Radioimmunoassay establishes the presence of PRL in seminal fluid; however, differences in the concentration of PRL over two separate studies were inconsistent, possibly because of differences in diet. The presence and localization of the PRLR are consistent with expression data reported for other species, and the presence of PIP and PRL in seminal fluid is consistent with data generated in humans.

Bulls grazing Kentucky 31 tall fescue exhibit impaired growth, semen quality, and decreased semen freezing potential.

Serum prolactin (PRL) and testosterone concentrations, body weight, body composition, semen quality, and semen freezing potential for bulls grazing the toxic tall fescue (Lolium arundinaceum [Schreb.] Darbysh. = Schedonorous arundinaceum [Schreb.] Dumort.) cultivar Kentucky 31 (E+) compared with a novel endophyte cultivar lacking ergot alkaloids (E-) were evaluated. Angus bulls were allotted to treatment (Day 0) and grazed E+ or E- for 155 days. Treatment-by-day interaction was significant (P < 0.05) for serum PRL concentrations with E+treated bulls exhibiting reduced PRL values compared with E- control bulls, but no differences were observed for serum testosterone concentrations (P > 0.05). Further, bulls on the E+ treatment exhibited decreased total gain, average daily gain, and body weight by Day 140 (P < 0.05) compared with the E- bulls. Rump muscle depth was lower because the treatment in bulls grazing E+ compared with E- (P < 0.05) and intramuscular fat in the E- bulls compared with the E+ group was higher by Day 155 (P < 0.05). Analysis of ejaculates showed significant treatment × day effects for sperm concentration with lower values observed for bulls on the E+ treatment (P < 0.05). The percent normal morphology was reduced in ejaculates from E+ bulls compared with E- bulls (P < 0.05), and the difference was due to an increase in abnormal sperm present in the E+ ejaculates from Day 84 to 140 (P < 0.05). In addition, spermatozoa motility and progressive motility were decreased on thawing in semen samples from E+ bulls compared with E- bulls (P < 0.05).

Alterations in embryo development in progestogen-supplemented cows administered prostaglandin F2alpha.

The objective was to examine effects of elevated prostaglandin F2alpha (PGF) on embryo development in cows supplemented with exogenous progestogen. Cows were artificially inseminated at estrus (Day 0) and a synthetic progestogen supplemented in the feed from Days 3 to 8. Cows were allotted randomly to receive either 15 mg PGF (TRT) or saline (CON) at 06:00, 14:00 and 22:00 h from Days 5 to 8. Blood samples were collected at 06:00 and 22:00 h from Days 5 to 8 for determination of progesterone and 13,14-dihydro-15-keto-PGF2alpha (PGFM). Single embryos were recovered on Day 8, assigned a quality score, and stage of development recorded. Progesterone was lower from Days 5 to 8 in TRT versus CON cows (P = 0.0001). Concentrations of PGFM from Days 5 to 8 were elevated in TRT compared to CON cows (P = 0.0001). Embryo quality was reduced in TRT cows compared to CON cows (P = 0.059). Percentage of embryos considered transferable was decreased by administration of PGF (P = 0.003). Sixty-four percent of TRT embryos were retarded in development at Day 8, whereas 80% of CON embryos had developed to expanded blastocysts (P = 0.003). In conclusion, treatment of progestogen-supplemented cows with PGF reduced quality and retarded development of embryos. Decreased fertility in conditions causing elevated concentrations of PGF may result from altered embryo development and quality.

Effects of elevated concentrations of prostaglandin F2 alpha on pregnancy rates in progestogen supplemented cattle.

An experiment was performed to determine the effect of elevated prostaglandin F2 alpha (PGF2 alpha) on pregnancy rates of progestogen-treated bred cows in the presence or absence of luteal tissue. Ninety-one beef cows were bred (Day 0) and assigned randomly to receive either 3 mL saline (CON), 15 mg PGF2 alpha, or 15 mg PGF2 alpha + lutectomy (P + L) administered intramuscularly (i.m.) at 8 h intervals on either Days 5-8, 10-13, or 15-18 postbreeding. Lutectomies were performed by transrectal digital pressure before initiation of treatment on Day 5, 10, or 15 for the respective treatment groups. All cows were fed 4 mg/day of melengesterol acetate from two days prior to initiation of treatment until Day 30 postbreeding. Mean concentrations of 13,14-dihydro-15-keto-PGF2 alpha (PGFM) were increased in cows administered PGF2 alpha and P + L treatments (398 +/- 23 and 413 +/- 22 pg/ml, respectively; p < 0.01) compared to the CON group (80 +/- 29 pg/ml) regardless of treatment group. Mean concentrations of oxytocin (OT) were increased in cows given PGF2 alpha on Day 10 and 15 (p < or = 0.0001) and tended to be increased on d 5 when compared to CON and P + L treatment groups on Day 5. Pregnancy rates were reduced (p < or = 0.03) in the PGF2 alpha treatment group (23%) and by Day 5-8 compared to CON (72%). Lutectomy tended to improve pregnancy rate in P + L (5-8; 55%) compared to PGF2 alpha (5-8; p = 0.1). Pregnancy rates tended (p < or = 0.07) to increase in the PGF2 alpha treatment groups on Days 5-8 treatment (23%, 50%, and 60% for Days 5-8, 10-13, and 15-18, respectively). The later the treatments were initiated pregnancy rates did not differ between treatments given on Days 10-13 and 15-18. In conclusion, the most susceptible period of embryonic growth to the negative effects of PGF2 alpha was during morula to blastocyst development. Removal of luteal tissue diminishes the negative effects of PGF2 alpha through interruption of the luteal oxytocin-uterine PGF2 alpha feedback loop.

Effects of administration of oxytocin on embryonic survival in progestogen supplemented cattle.

Embryonic survival after administration of oxytocin (OT) was examined in 42 beef cows. All cows were bred (Day 0) and randomly assigned to receive either 25 mL saline (CON; n = 10), 100 IU OT + 20 mL saline (OT; n = 12), 100 IU OT + 1 g flunixin meglumine (OT + FM; inhibitor of prostaglandin endoperoxide synthase; n = 10), or 100 IU OT + lutectomy (OT + LUT; n = 10) administered (i.m.) at 8-h intervals on Days 5-8 after mating. Lutectomies were performed by transrectal digital pressure prior to initiation of treatments (0600, Day 5). All cows were fed 4 mg/head/day of melengesterol acetate (an orally administered exogenous progestogen) through Days 3-30 and were bled by jugular venipuncture at 0600 and 0700 h on Day 5 for determination of 13,14-dihydro-15-keto-PGF2a (PGFM). Pregnancy rates, as determined by transrectal ultrasonography at Day 30, were reduced in OT (33.3%) and OT + LUT (30%) groups compared to CON and OT + FM (80%; p < or = 0.03). Number of short cycles were increased in OT (n = 6/12) group compared to CON (n = 0/10; p < or = 0.009) and OT + FM (n = 1/10; p < or = 0.045). Mean change in PGFM from the 0600 to 0700 h bleed was different (p < or = 0.01) between the OT + LUT (31.6 +/- 11.0 pg/mL) group versus CON (-11.2 +/- 10.6 pg/mL) and OT + FM (-13.8 +/- 10.6 pg/mL) groups. Administration of oxytocin appears to decrease embryonic survival by stimulating uterine PGF2a. Thus, previous reports indicating that removal of the corpus luteum during progestogen supplementation and prior to PGF2a administration increases embryonic survival can be explained through interruption of the luteal oxytocin-uterine PGF2a feedback loop.