Follicular development and reproductive endocrinology during and after superovulation in heifers and mature cows displaying contrasting superovulatory responses

To understand the causes for poor response to superovulation in mature cows of high genetic potential, endocrine and follicular events during and after superovulation were compared in heifers (<2 yr old) yielding large numbers of embryos and cows (9 to 13 yr old) known to be poor embryo donors. Follicular development was monitored by daily ultrasonography. Blood samples were taken 2 to 3 times a day for the measurements of P4, E2, FSH and LH by RIA. Intensive blood collections at 15-min intervals for 6 h were also performed during preovulatory and luteal phases. The number of embryos produced in the heifers (15.2 +/- 2; mean +/- SEM) and the cows (0.6 +/- 0.4), was similar to the number of ovulatory follicles derived from ultrasonographic observations in the heifers (16.2 +/- 3.7), but not in the cows (7.8 +/- 2.8). Contrary to that observations in heifers, there was no increase in the number of 4- to 5-mm follicles in cows during superovulation. The number of larger follicles (>5 mm) increased during superovulation in both cattle groups, but it was significantly lower in cows than in heifers. During superovulation, the maximal E2 concentration was greater (P < 0.0001) in heifers than in cows. One cow showed delayed luteolysis during superovulation, while another had abnormally high FSH (>10 ng/ml) and LH (>3 ng/ml) concentrations following superovulation. All the cows had a postovulatory FSH rise which was not detected in the heifers. The results showed that attempts to improve superovulatory response in mature genetically valuable cows are hampered by a number of reproductive disorders that are not predictable from the study of the unstimulated cycle.     

Studies of FSH-P induced follicular growth in cows

Because cow ovaries do not contain a dominant follicle before Day 3 of the estrous cycle, we hypothesized that gonadotropin treatment early in the estrous cycle would induce growth of multiple follicles and could be used to induce superovulation. In Experiment 1, when 16 cows were treated with FSH-P beginning on Day 2 of the estrous cycle and were slaughtered on Day 5, all cows responded to gonadotropin treatment by exhibiting a large number ( approximately 19) of estrogenactive follicles >/= 6 mm. In Experiment 2, in response to FSH-P treatment from Day 2 to Day 7, and fenprostalene treatment on Day 6, 11 of 15 cows exhibited estrus and had a mean ovulation rate of 23.7 +/- 1.5. In Experiment 3, an FSH-P treatment regimen identical to that used in Experiment 2 was administered to cows beginning either on Day 2 (Day-2 cows; n=14) or Day 10 (Day-10 cows; n=11) of the estrous cycle. Twelve of 14 Day-2 cows and all Day-10 cows exhibited estrus after fenprostalene treatment. Day-2 cows exhibited 34.3 +/- 7.0 ovulations, which was less (P < 0.05) than that exhibited by Day-10 cows (48.3 +/- 4.4). However, the proportion of embryos recovered per corpus luteum was about 2-fold greater (P < 0.05) for Day-2 cows than for Day-10 cows (0.49 +/- 0.08 vs 0.27 +/- 0.06). These data indicate that beginning gonadotropin treatment early in the estrous cycle, when a dominant follicle is not present, provides an efficacious means to induce growth of multiple follicles and superovulation in cows. However, when FSH was administered for 6 d, beginning the treatment on Day 10 also resulted in a consistent and efficacious response.     

Repeatability of response to superovulation in Brangus cows

Repeatabilities of total numbers of ova (TO) and morphologically normal embryos (MNE) recovered following superovulation of Brangus cows were estimated from records of 210 attempts involving 75 cows. Repeatability of the number of TO recovered was 0.22 +/- 0.08 and the number of MNE recovered was 0.19 +/- 0.08. Overall mean numbers of TO and MNE were 9.0 and 5.0, respectively. The mean numbers of TO recovered were 8.9 from the first treatment, 9.5 from the second treatment, and 8.6 from the third treatment. The mean numbers of MNE recovered were 5.2 from the first treatment, 4.6 from the second treatment, and 5.2 from the third treatment. Regressions of TO or MNE numbers per collection indicated that the superovulatory response did not decline significantly with repeated superovulation.     

Superovulation induction in Japanese Black cattle by a single intramuscular injection of hMG or FSH dissolved in polyvinylpyrrolidone.

The efficacy of a single intramuscular dose of 450 or 600 international units (IU) of human menopausal gonadotropin (hMG) or 30 mg of follicle stimulating hormone (FSH), each dissolved in 30% polyvinylpyrrolidone K-30 (PVP), for superovulation treatment was compared to that of superovulation induction by administration of a total dose of 600 IU hMG given in declining doses twice daily over a 3-day period. A total of 48 Japanese Black cows were used for the investigation. Oestrus was observed within 60 h after PGF2alpha administration in all cows in the hMG groups. In the hMG group that received a single dose of 600 IU hMG (n = 12), oestrus was observed less than 36 h after treatment in one cow. In contrast, oestrus was not observed in 3 of the 12 cows (25%) in the FSH group. Neither the average number of recovered ova/embryos nor the number of transferable embryos per collection differed significantly among the hMG groups. However, the average number of transferable embryos was not significantly higher in cows treated with a single dose of 600 IU of hMG than in cows treated with a single 30 mg dose of FSH (7.5+/-4.5 vs. 2.1+/-2.8). The number of cows from which more than three excellent grade embryos were collected was highest in the group that received a single dose of 600 IU hMG (9/12, 75%) and lowest in the group that received a single 30 mg dose of FSH (2/9, 22%). The differences between groups in the percentages of cows with three or more excellent embryos between treatments were not statistically significant. The proportion of recovered ova/embryos classified as excellent was highest in the group that received 600 IU hMG in declining doses and lowest in the group that received a single 30 mg dose of FSH (55.2% vs. 30.2%; P < 0.05). The recovery rate of unfertilized ova was lowest in the group that received a single dose of 600 IU hMG and highest in the group received a single 30 mg dose of FSH (18.3% vs. 48.8%; P < 0.05). Although the differences in recovery results between the groups were not statistically significant, the recovery rates in hMG groups were higher than that the FSH group. These findings suggest that superovulation can be induced adequately in Japanese Black cows using one injection of 450 to 600 IU hMG dissolved in PVP.     

Use of real-time ultrasound to identify multiple fetuses in beef cattle

To examine the feasibility of producing multiple births in beef cattle by means of superovulation, realtime ultrasound was used to identify cows carrying multiple fetuses. Three replicates of the superovulation experiment were conducted with groups of 52, 25 and 89 purebred Angus cows, respectively. Both uterine horns of cows from Replicate 1 were examined via the rectum using ultrasound at averages of 43 (range = 30 to 68 days), 51 (range = 38 to 76 days) and 126 (range = 113 to 151 days) days after AI. Cows in Replicate 2 were examined in the same fashion at averages of 55 and 97 days post insemination. In Replicate 3 the number of fetuses was estimated on a single date (average number of days post insemination = 49 days). Across the 3 replicates, the number of fetuses was most accurately assessed at an average of between 49 and 55 days post insemination. In most instances for which comparability between ultrasound estimations and calving results was low, the lack of correspondence was likely due to embryo mortality in cows identified as carrying multiple fetuses. For all 3 replicates combined, only 1 cow diagnosed with a single fetus produced multiple calves at birth when the diagnoses were conducted at 49 to 55 days post insemination. Real-time ultrasound can be used to accurately identify open cows and to differentiate between cows carrying single or multiple fetuses.     

An <Emphasis Type="Italic">Msp</Emphasis>I polymorphism in the inhibin alpha gene and its associations with superovulation traits in Chinese Holstein cows

To identify a predictor to forecast superovulation response on the basis of associations between superovulation performance and gene polymorphism, the PCR–RFLP method was applied to detect an A>G transition determining an MspI polymorphism at position 192 in the exon I of the bovine inhibin alpha (INHA) gene and evaluate its associations with superovulatory response in 118 Chinese Holstein cows treated for superovulation. Association analysis showed that cows with the GG genotype resulted in a significant increase in the number of ova (TNO) than AG and AA genotypes in the first (P = 0.023), second (P = 0.004) and third (P = 0.002) superovulation treatments and produced more transferable embryos (NTE) than that of AG and AA genotypes in the third (P = 0.045) superovulation treatment. Moreover, individuals with GG genotype produced more transferable embryos than AA (P < 0.05) genotype in the second superovulation treatment and all cows without superovulation response were mutations with genotypes of AA and AG. These results indicate that INHA gene can be used as a predictor for superovulation in Chinese Holstein cows, and imply that cows with AA genotype should be excluded for superovulation practices.     

Embryo production by repeated superovulation of commercial donor cows

Mature beef cows of 13 major and several minor breeds were repeatedly superovulated by injections of follicle stimulating hormone (FSH) and prostaglandin F2 alpha (PGF). Embryos were collected nonsurgically 6 to 8 days after artificial insemination. The average number of transferable embryos per collection was measured on the basis of all cows started on superovulation. Within groups of cows superovulated from two to ten times, embryo production per collection declined with repeated collections. This decline was not apparent in the pooled data when the mean number of embryos per collection the first through the tenth collection was 5.6, 5.1, 4.9, 5.0, 4.3, 5.1, 5.0, 5.0, 5.4, and 5.6 embryos, respectively. Embryo production at the first collection was one of the criteria for selecting cows for repeated superovulation. Cows superovulated more than three times had the highest embryo production at the first collection. The decline in embryo production with repeated superovulation could not be corrected by increasing the FSH dose. The number of embryos per collection was significantly correlated in cows superovulated repeated times. The correlation coefficients varied from 0.32 in cows superovulated twice to 0.35 in cows superovulated 10 times. The predictability of embryo production from cows that were selected to remain in the embryo transplant program, and were superovulated more and more times, did not increase. Some cows continued to produce embryos after 20 repeated superovulations. The results indicated that a cow should be superovulated two or three times before being discarded as a poor embryo producer.     

Genetic parameters for first lactation test-day milk flow in Holstein cows

Genetic parameters for test-day milk flow (TDMF) of 2175 first lactations of Holstein cows were estimated using multiple-trait and repeatability models. The models included the direct additive genetic effect as a random effect and contemporary group (defined as the year and month of test) and age of cow at calving (linear and quadratic effect) as fixed effects. For the repeatability model, in addition to the effects cited, the permanent environmental effect of the animal was also included as a random effect. Variance components were estimated using the restricted maximum likelihood method in single- and multiple-trait and repeatability analyses. The heritability estimates for TDMF ranged from 0.23 (TDMF 6) to 0.32 (TDMF 2 and TDMF 4) in single-trait analysis and from 0.28 (TDMF 7 and TDMF 10) to 0.37 (TDMF 4) in multiple-trait analysis. In general, higher heritabilities were observed at the beginning of lactation until the fourth month. Heritability estimated with the repeatability model was 0.27 and the coefficient of repeatability for first lactation TDMF was 0.66. The genetic correlations were positive and ranged from 0.72 (TDMF 1 and 10) to 0.97 (TDMF 4 and 5). The results indicate that milk flow should respond satisfactorily to selection, promoting rapid genetic gains because the estimated heritabilities were moderate to high. Higher genetic gains might be obtained if selection was performed in the TDMF 4. Both the repeatability model and the multiple-trait model are adequate for the genetic evaluation of animals in terms of milk flow, but the latter provides more accurate estimates of breeding values.     

Anti-mullerian hormone is an endocrine marker of ovarian gonadotropin-responsive follicles and can help to predict superovulatory responses in the cow

The major limitation to the development of embryo production in cattle is the strong between-animal variability in ovulatory response to FSH-induced superovulation, mainly due to differences in ovarian activity at the time of treatment. This study aimed to establish whether anti-Müllerian hormone (AMH) was an endocrine marker of follicular populations in the cow, as in human, and a possible predictor of the ovarian response to superovulation. Anti-Müllerian hormone concentrations in plasma varied 10-fold between cows before treatment and were found to be highly correlated with the numbers of 3- to 7-mm antral follicles detected by ovarian ultrasonography before treatment (r=0.79, P<0.001) and the numbers of ovulations after treatment (r=0.64, P<0.01). Between-animal differences in AMH concentrations were found to be unchanged after a 3-mo delay (r=0.87, P<0.01), indicating that AMH endocrine levels were characteristic of each animal on a long-term period. The population of healthy 3- to 7-mm follicles was the main target of superovulatory treatments, contained the highest AMH concentrations and AMH mRNA levels compared with larger follicles, and contributed importantly to AMH endocrine levels. In conclusion, AMH was found to be a reliable endocrine marker of the population of small antral gonadotropin-responsive follicles in the cow. Moreover, AMH concentrations in the plasma of individuals were indicative of their ability to respond to superovulatory treatments.     

Real-time evaluation of milk quality as reflected by clotting parameters of individual cow's milk during the milking session,between day-to-day and during lactation

Real-time analysis of milk coagulation properties as performed by the AfiLab™ milk spectrometer introduces new opportunities for the dairy industry. The study evaluated the performance of the AfiLab™ in a milking parlor of a commercial farm to provide real-time analysis of milk-clotting parameters –Afi-CF for cheese manufacture and determine its repeatability in time for individual cows. The AfiLab™ in a parlor, equipped with two parallel milk lines, enables to divert the milk on-line into two bulk milk tanks (A and B). Three commercial dairy herds of 220 to 320 Israeli Holstein cows producing ∼11 500 l during 305 days were selected for the study. The Afi-CF repeatability during time was found significant (P < 0.001) for cows. The statistic model succeeded in explaining 83.5% of the variance between Afi-CF and cows, and no significant variance was found between the mean weekly repeated recordings. Days in milk and log somatic cell count (SCC) had no significant effect. Fat, protein and lactose significantly affected Afi-CF and the empirical van Slyke equation. Real-time simulations were performed for different cutoff levels of coagulation properties where the milk of high Afi-CF cutoff value was channeled to tank A and the lower into tank B. The simulations showed that milk coagulation properties of an individual cow are not uniform, as most cows contributed milk to both tanks. Proportions of the individual cow's milk in each tank depended on the selected Afi-CF cutoff. The assessment of the major causative factors of a cow producing low-quality milk for cheese production was evaluated for the group that produced the low 10% quality milk. The largest number of cows in those groups at the three farms was found to be cows with post-intramammary infection with Escherichia coli and subclinical infections with streptococci or coagulase-negative staphylococci (∼30%), although the SCC of these cows was not significantly different. Early time in lactation together with high milk yield >50 l/day, and late in lactation together with low milk yield<15 l/day and estrous (0 to 5 days) were also important influencing factors for low-quality milk. However, ∼50% of the tested variables did not explain any of the factors responsible for the cow producing milk in the low – 10% Afi-CF.     

Follicular development and superovulation response in cows administered multiple FSH injections early in the estrous cycle

To determine whether follicular development, superovulation and embryo production were affected by the absence or presence of a dominant follicle, cows were administered injections of FSH twice daily in the early (Days 2 to 6, estrus = Day 0) or middle stage (beginning on Day 10 or 11) of the estrous cycle. Treatment with FSH early in the cycle stimulated follicular development in 83 to 100% of all cows from 4 groups evaluated at different times after PGF2alpha treatment on Days 6 and 7. However, the proportion of cows with > 2 ovulations varied from 31 to 62.5%, indicating that induction of follicular development may occur in the absence of superovulation. When compared with cows treated in the middle of the cycle, no differences were observed in the proportion of cows with > 2 ovulations (31 vs 20%), ovulation rate. (26.0 +/- 6.3 vs 49.6 +/- 25.8), production of ova/embryos (13.3 +/- 3.2 vs 14.4 +/- 3.4), or the number of transferable embryos (8.0 +/- 3.6 vs 5.4 +/- 1.5; early vs middle, respectively). The proportion of the total number of embryos collected that were suitable for transfer was greater (P<0.01) in cows treated early in the cycle (60%) than at midcycle (37.5%). The diameter of the largest follicle observed by ultra-sound prior to initiation of FSH treatment in the early stage of the cycle (10.0 +/- 2.0 mm) was smaller (P<0.05) than at midcyle (16.8 +/- 1.3 mm). These results demonstrate that superinduction of follicular development is highly consistent after FSH treatment at Days 2 to 6 of the cycle and that superovulation and embryo production are not less variable than when FSH is administered during the middle of the cycle. However, superovulation in the early stage of the cycle may increase the proportion of embryos suitable for transfer.     

Polymorphisms of the bovine luteinizing hormone/choriogonadotropin receptor (LHCGR) gene and its association with superovulation traits

The major limitation to the development of embryo transfer technique in cattle is the highly variable between individuals in ovulatory response to FSH-induced superovulation. The objective of this study was to identify a predictor to forecast superovulation response on the basis of associations between superovulation performance and gene polymorphism, variation in the bovine luteinizing hormone/choriogonadotropin receptor (LHCGR) gene was investigated using PCR-single-strand conformational (PCR-SSCP) and DNA sequencing. Four single nucleotide polymorphisms (SNPs) of G51656T, A51703G, A51726G and G51737A were identified at the intron 9 of the LHCGR gene in 171 Chinese Holstein cows treated for superovulation, and evaluated its associations with superovulatory response. Association analysis showed that these four SNPs had significant effects on the total number of ova (TNO) (P < 0.05). Moreover, the A51703G and A51726G polymorphisms significantly associated with the number of transferable embryos (NTE) (P < 0.05). In addition, significant additive effect on TNO was detected in polymorphisms of G51656T (P < 0.05) and A51703G (P < 0.01), and the A51703G polymorphism also had significant additive effects on NTE (P < 0.01). These results indicate that LHCGR gene is a potential marker for superovulation response and can be used to predict the most appropriate dose of FSH for superovulation in Chinese Holstein cows.     

Embryonic loss in superovulated cattle caused by the 1;29 Robertsonian translocation

The effect of the 1;29 Robertsonian translocation on fertility was studied using embryos resulting from matings of nine carrier cows and two carrier bulls. Embryos were collected from the following three mating groups utilizing superovulation: normal bull cross normal cow, normal bull cross translocation carrier cow, and translocation carrier bull cross normal cow. The proportion of ova which were fertilized did not vary among the groups, indicating that fertilization rates were not affected by the translocation. The translocation cows did yield fewer embryos on average than did cows with normal karyotypes, which may suggest ovulation rates are reduced (at least after superovulation attempts) in cattle carrying the 1;29 translocation. Twenty of 39 embryos successfully karyotyped had abnormal chromosome complements. All four of the theoretically predicted karyotypes and two additional abnormal combinations were found. Eight of 39 (20.5%) embryos karyotyped had unbalanced karyotypes which would have resulted in embryonic loss. The proportion of embryos with unbalanced karyotypes, was slightly higher when the cow (36%) carried the translocation than when the bull (19%) did. Results of this study indicate that fertility is impaired due to the presence of this translocation. The major loss in reproductive potential appears to be due to embryonic loss rather than fertilization failure.     

Effects of inbreeding on ovarian responses and embryo production from superovulated Mantiqueira breed cows

The objective of the present experiment was to evaluate the effects of different levels of inbreeding on ovarian response and embryo production from superovulated cows. One hundred and thirteen Mantiqueira cows (a medium-size, Bos taurus native dairy cattle breed), with inbreeding coefficients ranging from 0 to 30%, were allocated into five classes of inbreeding and subjected to superovulation treatment. At induced estrus, cows were mated with Mantiqueira bulls (with minimal inbreeding). Six to eight days after mating, the cows were slaughtered, ovarian structures counted and embryos recovered by flushing the uterine horns and oviducts. Sire, season, age, weight, parity and age at first calving of donors did not significantly affect ovarian response or embryo production and quality. There were no effects of inbreeding class on number of total corpora lutea (CL) or number of CL present in the right ovary. However, the number of CL in the left ovary was reduced (P<0.05) in cows with Class 5 (>9%) of inbreeding. The number of transferable, but not the number of non-transferable embryos or the total number of embryos from cows with Class 5 of inbreeding, was lower (P<0.05) than those of cows from Classes 0 to 4 (<9%) of inbreeding. There was a quadratic decrease in the number of transferable embryos as inbreeding coefficient increased (Y=11.077+0.34X-0.0529X(2); R(2)=0.91, P<0.01), but no significant linear or quadratic effect of inbreeding on total number of embryos or number of non-transferable embryos. In conclusion, an inbreeding coefficient>9% reduced the quality of bovine embryos at the initial stage of development.     

Dose of FSH-P as a source of variation in embryo production from superovulated cows

Various superovulation treatments were evaluated retrospectively in a commercial embryo transfer program. When it appeared that embryo production was dependent on the dose of FSH-P, a dose response curve to FSH-P was developed and embryo production compared using several treatment regimes. There was a significant effect of dose of FSH-P on embryo production in superovulated cows. At doses in excess of 28 mg, embryo production declined from 5.9 transferable embryos per collection (28 mg) to 2.7 (60 mg). Total embryos collected declined from 14.9 to 6.8 and the percent transferable from 57% to 40%. There was no advantage in using a five-day treatment over a four-day treatment regimen or in using a level over a declining dose regimen. There was a large individual variation in cow response rendering decisions on treatment changes based on single records unreliable. The percentage of zero collections increased with dose rate. Adoption of a 28-mg dose rate in commercial donors resulted in the embryo production forecast by these studies.     

Effect of recombinant bovine somatotropin (rBST) on follicular IGF-I contents and the ovarian response following superovulatory treatment in dairy cows: a preliminary study

Somatotropin and FSH act synergystically on insulin-like growth factor-I (IGF-I) synthesis in ovarian follicles; IGF-I regulates several granulosa cell specific functions and may thereby be beneficial in bovine superovulation. In a series of 3 experiments we investigated the effects of recombinant bovine somatotropin (rBST) on several parameters of the superovulatory response in dairy cows. A total of 81 Holstein Friesian crossbred dairy cows received either 640 mg rBST or the vehicle (controls) on Day 4 or 13 of the superovulation schedule. Superovulation was induced with 2500 IU PMSG on Day 9. The cows were artificially inseminated on Day 13. In Experiment 1, on Days 4, 8, 11, 13 and 17 4 to 5 animals each were slaughtered to obtain follicular fluid, endometrium and plasma. The rBST application increased IGF-I contents in plasma and follicular fluid on Days 8, 11 and 13 (P < 0.05) in the treated cows when compared with that of the controls. Plasma and follicular IGF-I contents were correlated closely (rBST: r = 0.90, n = 10; control: r = 0.94, n = 9). The number of antral follicles increased following rBST treatment, and on the day of artificial insemination (AI) twice as many follicles > 4 mm were counted in the rBST treated animals than in the control group. In Experiment 2, the flushing of 38 donors on Day 7 after AI resulted in more transferable embryos in the rBST group than in the control group (4.2 +/- 1.0 vs 2.5 +/- 0.7; P < 0.05). In contrast, in Experiment 3 involving 21 animals when rBST was administered at the time of AI the superovulation response was not altered. It is concluded that rBST increases follicular and plasma IGF-I contents and thereby has profound effects on follicular and early embryonic development.     

Environmental and cow-related factors affect cow locomotion and can cause misclassification in lameness detection systems

To tackle the high prevalence of lameness, techniques to monitor cow locomotion are being developed in order to detect changes in cows’ locomotion due to lameness. Obviously, in such lameness detection systems, alerts should only respond to locomotion changes that are related to lameness. However, other environmental or cow factors can contribute to locomotion changes not related to lameness and hence, might cause false alerts. In this study the effects of wet surfaces, dark environment, age, production level, lactation and gestation stage on cow locomotion were investigated. Data was collected at Institute for Agricultural and Fisheries Research research farm (Melle, Belgium) during a 5-month period. The gait variables of 30 non-lame and healthy Holstein cows were automatically measured every day. In dark environments and on wet walking surfaces cows took shorter, more asymmetrical strides with less step overlap. In general, older cows had a more asymmetrical gait and they walked slower with more abduction. Lactation stage or gestation stage also showed significant association with asymmetrical and shorter gait and less step overlap probably due to the heavy calf in the uterus. Next, two lameness detection algorithms were developed to investigate the added value of environmental and cow data into detection models. One algorithm solely used locomotion variables and a second algorithm used the same locomotion variables and additional environmental and cow data. In the latter algorithm only age and lactation stage together with the locomotion variables were withheld during model building. When comparing the sensitivity for the detection of non-lame cows, sensitivity increased by 10% when the cow data was added in the algorithm (sensitivity was 70% and 80% for the first and second algorithm, respectively). Hence, the number of false alerts for lame cows that were actually non-lame, decreased. This pilot study shows that using knowledge on influencing factors on cow locomotion will help in reducing the number of false alerts for lameness detection systems under development. However, further research is necessary in order to better understand these and many other possible influencing factors (e.g. trimming, conformation) of non-lame and hence ‘normal’ locomotion in cows.     

Multivariate analysis of factors associated with calving interval and calving rate in dairy cows

We collected data on reproductive events of cows (n = 2116) that included dates of calving, first service, last artificial insemination before pregnancy examination, pregnancy examination, abortion, diagnosis of cystic ovary, and treatment with prostaglandin. We used multivariate analysis to evaluate the relationship between the interval from insemination to pregnancy examination and the length of calving interval, adjusting for other factors affecting the calving interval. The effect of the interval from insemination to pregnancy examination on calving rate was estimated using logistic regression analysis. The calving interval was long for cows with a short interval from artificial insemination to first pregnancy examination, it was at a minimum at 55 d and increased thereafter. Other factors affecting the calving interval were cystic ovaries, prostaglandin treatment, abortion, number of artificial inseminations, and days to first service. The calving rate was low among cows with a short interval to pregnancy examination, reached a maximum at 48 d, and then declined. Other factors affecting the calving rate were abortion, number of artificial inseminations and whether the cow was bred by a clean-up bull.     

Unexpected Decrease in Milk Production after Fenbendazole Treatment of Dairy Cows during Early Grazing Season

Gastrointestinal nematodes (GIN) infection can impair milk production (MP) in dairy cows. To investigate whether MP would be optimized by spring targeted-selective anthelmintic treatment in grazing cows, we assessed (1) the effect on MP of an anthelmintic treatment applied 1.5 to 2 months after turn-out, and (2) herd and individual indicators associated with the post-treatment MP response. A randomized controlled clinical trial was conducted in 13 dairy farms (578 cows) in western France in spring 2012. In each herd, lactating cows of the treatment group received fenbendazole orally, control cows remained untreated. Daily cow MP was recorded from 2 weeks before until 15 weeks after treatment. Individual serum pepsinogen and anti-Ostertagia antibody levels (expressed as ODR), faecal egg count and bulk tank milk (BTM) Ostertagia ODR were measured at treatment time. Anthelmintic treatment applied during the previous housing period was recorded for each cow. In each herd, information regarding heifers’ grazing and anthelmintic treatment history was collected to assess the Time of Effective Contact (TEC, in months) with GIN infective larvae before the first calving. The effect of treatment on weekly MP averages and its relationships with herd and individual indicators were studied using linear mixed models with two nested random effects (cow within herd). Unexpectedly, spring treatment had a significant detrimental effect on MP (-0.92 kg/cow/day on average). This negative MP response was particularly marked in high producing cows, in cows not treated during the previous housing period or with high pepsinogen levels, and in cows from herds with a high TEC or a high BTM ODR. This post-treatment decrease in MP may be associated with immuno-inflammatory mechanisms. Until further studies can assess whether this unexpected result can be generalized, non-persistent treatment of immunized adult dairy cows against GIN should not be recommended in early grazing season.     

Buserelin in a superovulatory regimen for Holstein cows: II. Yield and quality of embryos in commercial herds

The gonadotropin releasing hormone analog, Buserelin, was tested in a superovulatory regimen in cows by administering 8 mug of it at the following times: Group I (12 cows), 48 h after the first prostaglandin F(2) alpha (PGF) injection: Group II (11 cows), 54 h after PGF: Group III (10 cows), 24 h after standing estrus was first observed; and Group IV (12 cows), served as superovulated controls. The cows were lactating Holsteins between 45 and 143 d post partum, with at least one estrus prior to superovulation. The number of embryos collected from Groups I, II, III and IV 7 d after estrus averaged 4.5, 8.1, 6.4 and 5.6, respectively (P>0.05). The fertilization rate in the three groups receiving Buserelin was 83 versus 76% for controls (P<0.10). Blood and milk samples taken just before starting follicle stimulating hormone treatment at the expected estrus and at the time of embryo recovery were tested for progesterone concentration, and results from a rapid ELISA test were useful in identifying cows that a) were unsuitable for superovulation, b) should have been in estrus but were not observed standing and c) produced few, if any, embryos.