Extended lactation in high-yielding dairy cows. II. Effects on milk production, udder health, and body measurements.

The objective of this prospective field study was to evaluate the effects of extending the lactation period of high-yielding dairy cows on milk production, udder health characteristics, and development of body condition. On 40 d in milk (DIM), an examination of the genital tract (transrectal palpation, sonography, vaginoscopy) was performed. Cows without signs of clinical endometritis were blocked by parity and were randomly allocated to 1 of 3 experimental groups with a voluntary waiting period of 40, 120, and 180 d, respectively (G40, n = 135; G120, n = 141; G180, n = 139). Mean daily milk and energy-corrected milk production did not differ between the 3 groups regarding the first 305 d or for the whole lactation (d 1 and up to dry off, culling, or 600 DIM). In late lactation (306 to 600 DIM), G40 had lower average productivity (23.8 kg) compared with G120 (26.5 kg), with G180 showing intermediate values (25.7 kg). The extended lactation groups showed greater persistency, as the rate of decline based on a Wilmink function was lower for G120 (c = -0.063 and -0.045 for milk and energy-corrected milk, respectively) and G180 (c = -0.061 and -0.047) compared with G40 (c = -0.071 and -0.056). We found no difference between the 3 groups regarding the evaluated udder health characteristics (somatic cell count, incidence of mastitis, and days off milk due to mastitis). More cows in G180 (7.9%) were culled due to low productivity compared with G40 (0.7%) and as a tendency compared with G120 (2.8%). Moreover, cows of G180 showed higher median body condition score at the time of dry off compared with cows of both G40 and G120 (3.50 for G180 vs. 3.25 for both G40 and G120). At the time of dry off, G180 cows also had greater backfat thickness (25.0 mm) compared with both G40 (22.2 mm) and G120 cows (21.6 mm). Based on our results, the extension of the voluntary waiting period of high-yielding cows up to 120 d has no adverse effects regarding milk production, involuntary culling, udder health, or BCS gain.

Extended lactation in high-yielding dairy cows. I. Effects on reproductive measurements.

The objective of this prospective field study was to evaluate the effects of extending the lactation period on various reproductive measurements of high-yielding Holstein cows. On 40 d in milk (DIM), cows were gynecologically examined (transrectal palpation, sonography, vaginoscopy). Cows without signs of clinical endometritis were blocked by parity and were randomly allocated to 1 of 3 experimental groups with a voluntary waiting period (VWP) of 40, 120, and 180 d, respectively (G40, n = 135; G120, n = 141; G180, n = 139). Cows of G120 and G180 were reexamined at the end of the VWP. If natural estrus was detected within 46 d after the end of the VWP, an artificial insemination was performed. If no estrus was detected, the respective cows were synchronized by applying the classical Ovsynch protocol. We found no difference in the proportion of cows in which estrus was detected between 40 to 86 DIM or in the days to first estrus between the 3 groups. Estrus detection in this period was lower in cows with body condition score <3 on 90 DIM compared with body condition score ≥3 (61.5 vs. 76.0%) and in cows with high energy-corrected milk production (ECM) on 92 DIM [58.6 vs. 70.1%, for cows with higher and lower than the median (39.9 kg) ECM, respectively]. The proportion of cows that estrus was detected within 46 d after the VWP was greater in G120 (88.9%) and G180 (90.8%) compared with G40 (70.4%). These effects were more apparent in cows with high ECM. The rate of estrus detection and of becoming pregnant in this period was greater for G120 (hazard ratio = 2.2 and 1.6, respectively) and for G180 (hazard ratio = 2.4 and 1.8) compared with G40. Cows in both groups with extended lactation had greater overall first service conception rates (G120 = 48.9%; G180 = 49.6%) and a lower number of services per pregnant cow (G120 = 1.56 ± 0.1; G180 = 1.51 ± 0.1) compared with G40 (36.6%; 1.77 ± 0.1). We observed no difference in pregnancy loss or in the proportion of cows culled up to 305 d of lactation between the 3 groups. The number of Ovsynch protocols per 1,000,000 kg of ECM was reduced by 75% in G180 and by 74% in G120 compared with G40 (5.9 vs. 7.1 vs. 25.1). In conclusion, extending the lactation of dairy cows can improve main reproductive measurements in high-yielding cows.

Effect of astaxanthin on the quality of boar sperm stored at 17°C, incubated at 37°C or under in vitro conditions.

The aim of the study was to investigate the effect of the antioxidant astaxanthin on boar semen. Twenty ejaculates from 10 boars (two ejaculates/boar) were extended and split in three groups: semen control (SC), solvent control (C; semen with dimethyl sulfoxide, the diluent of astaxanthin) and semen with astaxanthin (A) in concentration 0.5 µmol/L. Sperm quality parameters (motility and kinetics, morphology, viability, functional integrity of sperm plasma membrane by Hypo-Osmotic Swelling Test [HOST] and DNA integrity) were assessed at 0, 24 and 48 hr of storage at 17°C (experiment I), before (0 hr) and after (1 hr) of sperm thermal resistance assay at 37°C (experiment II) and finally before (0 hr) and after (1 hr) sperm in vitro incubation (38.5°C, 5% CO2 , maximum humidity [experiment III]). In experiment I, group A performed overall better than group SC and as a tendency better than group C regarding viability. Total motility, rapid spermatozoa and HOST remained constant across time in group A, whereas they decreased in the remaining groups. In experiment II, regarding motility and viability, group A displayed better results across time than the other two groups. In experiment III, viability and total motility decreased in groups SC and C, while in group A, these parameters were not significantly different between the examination time points. In conclusion, astaxanthin has a beneficial and protective effect on boar semen quality under the investigated conditions.

Selected steps of swine ICSI method to overcome seasonal effect and achieve acceptable early embryonic development, a preliminary study.

Porcine intra cytoplasmic sperm injection's (ICSI) efficacy by selected protocol steps was investigated. Three trials per year's period (hot, medium, cold) were carried out. Only large size follicles (6-8mm) were aspirated, brilliant cresyl blue (BCB) test was performed and only the BCB+ oocytes were in vitro maturated (40h) and involved to ICSI process. The presumptive embryos were in vitro cultured (15h). Raw boar semen and SpermCatch® as slowing medium were used. No differences were observed between periods regarding early embryonic development and maturation competence. ICSI achieves acceptable porcine early embryonic development rates under the investigated conditions.

Breed differences of bull frozen-thawed semen.

The objective of this study was to investigate the quality of frozen-thawed semen from different bull breeds. Commercial frozen-thawed bull semen samples (26 per breed, 130 totally) of five breeds (Holstein [Η], Brown Swiss [BS], Limousin [L], Belgian Blue [BB], Blonde d' Aquitaine [BA]) were used. After thawing, each semen sample was subjected to thermal resistance test (TR) for 0.5 and 1 hr at 38°C and hypo-osmotic swelling test (HOST) for 1 hr at 150 mOsm at 37°C. Additionally, all samples were evaluated at times 0 hr (thawing), 0.5 hr (TR), 1 hr (TR) for kinetics by CASA [progressive, immotile, rapid, medium, slow moving spermatozoa, curvilinear velocity (VCL), average path velocity (VAP), straight line velocity (VSL), linearity (LIN), straightness (STR), beat cross-frequency (BCF), amplitude of lateral head displacement (ALH), wobble (WOB)]. Moreover, directly after thawing, all semen samples were evaluated for morphometry, morphology, viability and DNA fragmentation. Statistical analysis was conducted using a mixed model for repeated measures. The results showed (a) higher VCL after thawing in H, L breeds compared to BB and BA, (b) higher VAP after thawing in L compared to BB, BA, (c) higher values of progressive spermatozoa after TR in H, BS compared to BB, BA, (d) higher values of rapid spermatozoa after thawing and 0.5 hr of TR in H, BS, L compared to BB, BA, (e) lower viability in BA after thawing compared to H, BS, BB, (f) lower morphological abnormalities in H compared to L, BB, (g) higher head length in Η compared to BB. No significant differences were observed in the results from HOST and DNA fragmentation between breeds. In conclusion, quality characteristics of frozen-thawed bull semen are dependent on the breed. Frozen semen from BB and BA breeds should be handled more carefully after thawing, as it is more sensitive to stress.

Combined use of Ovsynch and progesterone supplementation after artificial insemination in dairy cattle.

The objective of this study was to evaluate the effects of different Ovsynch protocols combined with progesterone (P4) supplementation after artificial insemination (AI) of Holstein-Friesian cows. Cows were randomly synchronized at 52 to 63 d after parturition with either the classical Ovsynch protocol (GnRH on d 0, PGF(2α) on d 7, GnRH 48 h after PGF(2α)) or with a modified Ovsynch protocol (second GnRH 60 h after PGF(2α)). On d 4 after timed AI (TAI), the cows were blocked by parity and randomly divided into 2 groups. Half of the cows were supplemented with P4 (P4+) by applying a P4-releasing intravaginal device intravaginally for 14 d, whereas the other half remained untreated (P4-). In 50% of randomly chosen cows, plasma P4 was measured on d 4, 5, and 18 after TAI. Sonographic pregnancy diagnosis was performed on d 33 after TAI in a total of 398 cows. Health status and body condition score (BCS) of all cows were examined at several stages of the study. Cows in the modified Ovsynch protocol tended to have higher P4 values on d 4 after TAI than cows in the classical Ovsynch protocol (2.1 ± 0.2 vs. 1.6 ± 0.2 ng/mL), but no difference in pregnancy per AI (P/AI) was observed between the 2 Ovsynch protocols (38.4% vs. 44.1%). Independent of the Ovsynch protocols, P4+ cows tended to have higher P/AI compared with P4- cows (44.4% vs. 38.1%). The retention of fetal membranes and BCS at the time of insemination affected P/AI. Moreover, an interaction between BCS at the time of insemination and P4 supplementation was apparent; that is, the difference in P/AI between P4+ and P4- cows was significant in cows with BCS ≥3.25. Progesterone-supplemented cows showed higher P4 values on d 5 (4.9 ± 0.2 vs. 2.6 ± 0.2) and d 18 (7.8 ± 0.2 vs. 6.3 ± 0.2) after TAI, respectively. In conclusion, the elongation of the time interval between the injections of PGF(2α) and the second GnRH from 48 to 60 h had no effect on P/AI. Progesterone supplementation after insemination improved the P/AI of the Ovsynch protocols, but this effect was more apparent in cows with BCS ≥3.25.

Short communication: Variance and autocorrelation of deviations in daily milk yield are related with clinical mastitis in dairy cows.

Daily milk production, and fluctuations therein, can provide information on health and resilience of dairy cows. We studied variance and autocorrelation of deviations in daily milk yield in relation to the occurrence of clinical mastitis (no, early or later in lactation). Individual lactation curves were fitted to 305-d lactations of 414 dairy cows using quantile regression. Log-transformed variance (lnVar) and autocorrelation of the quantile residuals of daily milk yield (predicted - observed) were evaluated for intervals until 30 and until 305 days in milk (DIM). Cows were classified as having no mastitis (n = 249), early mastitis that first occurred before 30 DIM (n = 29); or later mastitis (n = 136). Subsequently, linear models were used to assess effects of mastitis and parity class (primiparous or multiparous) on lnVar and autocorrelations; and logistic regression analyses were performed to predict mastitis from lnVar or autocorrelation and parity. From 10 to 30 DIM, lnVar was greater for cows with early mastitis than for cows with no or late mastitis, and autocorrelation tended to be lower for cows with early mastitis than for cows with no mastitis. The lnVar and autocorrelation from 10 to 30 DIM were not predictive of late mastitis. From 10 to 305 DIM, lnVar was greater and autocorrelation was lower for both cows with early and late mastitis than for cows with no mastitis; and both were predictive of having mastitis in the 305-d lactation. Primiparous cows had lower lnVar than multiparous cows. In cows without mastitis, autocorrelation values were positively correlated with lnVar. Results confirm that increased lnVar is associated with clinical mastitis.

Increased risk of conception failure in German Holstein Friesian cows with chronic endometritis.

The objective of this retrospective field study was to evaluate the effect of chronic clinical endometritis (CCE) on days open in German Holstein Friesian cows. Two hundred and sixty-four cows diagnosed with CCE from day 14 to 42 postpartum were included in this study. A Cox's proportional hazards regression model with stepwise forward selection for days open was used and the variables type of vaginal discharge, ovarian cysts and a marked loss of body condition score proved to be significant with hazard ratios of 1.5, 2.0 and 1.9 respectively. Although not remaining in the model, a weak positive effect of treatment for CCE and a negative effect of high milk production could also be found in the univariate analysis. These results suggest that the suppression of fertility of animals diagnosed with CCE varies according to the different symptoms, which could be used to support decisions regarding treatment. Management factors such as a marked loss in body condition and high milk production prolonged the number of days open of animals with CCE.

Method agreement between three different chambers for comparative bull semen computer assisted sperm motility analysis.

The aim of this study was to compare computer assisted sperm analysis (CASA) results of frozen thawed bull semen using three different chambers. Sixty bull frozen semen samples were thawed (37°C; 30 sec), extended in PBS (30×106 spermatozoa/mL; 37°C) and incubated (37°C; 2 min). Each semen sample was analyzed by CASA [total motility, progressive (pro)/ non-progressive/rapid/medium/slow movement spermatozoa, VCL, VSL, VAP, ALH, BCF, LIN, STR, WOB and hyperactive spermatozoa] using three different chambers: a Makler® chamber (MC; 10 µm); a Leja 4 chamber slide (LC; 20 µm); and a Glass slide covered with a coverslip (GSC; 10.3 µm). The Makler chamber gave higher values compared to both the LC and GSC for almost all examined parameters. No systematic effect was evident between LC and GSC for VCL, VSL, VAP, LIN, STR, WOB, ALH, and BCF. Method agreement between MC and LC was generally moderate, between MC and GSC poor and between LC and GSC moderate to good. In general, narrower limits of agreement were found in samples with lower values. In conclusion, the CASA outcomes could be influenced by the analysis chambers. This finding should be taken into consideration when comparing results from different laboratories.

Body condition loss and increased serum levels of nonesterified fatty acids enhance progesterone levels at estrus and reduce estrous activity and insemination rates in postpartum dairy cows.

Data from 96 Holstein Friesian cows on a commercial dairy farm were used to investigate whether body condition and serum levels of nonesterified fatty acids (NEFAs) postpartum (pp) affect progesterone (P4) levels, estrous activity, and fertility in dairy cows. The examination period started 14 days before the expected calving date and ended either when a cow was inseminated or at a maximum of 90 days pp. Body condition score (BCS; 1-5 scale) and backfat thickness (BFT) were determined every 2 weeks. Blood for analysis of NEFA and P4 concentrations was sampled weekly during the first 35 days pp and then every 48 hours until an ovulation was observed. Transrectal ultrasonography of the ovaries started at 21 days pp and was performed after blood sampling. If cows were not inseminated because of silent ovulation, sampling and ultrasonography continued on Days 7, 14, and 18 after ovulation and again every 48 hours until the next ovulation. Estrous activity was continuously measured with the Heatime estrus detection system. Pregnancy controls were performed ultrasonographically 28 and 42 days after AI. Cows with increased NEFA levels at 28 days pp had an increased risk of maintaining minimum P4 levels above 0.4 ng/mL at first recognized estrus (P = 0.03). Higher NEFA levels at Day 7 were associated with lower probability for a cow to have elevated P4 levels (≥2 ng/mL) by Day 35 pp, indicating delayed commencement of luteal activity (C-LA). Estrous activity was not influenced (P > 0.10) by minimum P4 concentrations at estrus, but more animals with C-LA until Day 35 pp showed estrous activity compared to cows without C-LA throughout this period (P = 0.006). Estrous activity was lower in cows with a low BCS 14 days pp (P = 0.02) and with a low BFT 42 days pp (P = 0.03). Moreover, the probability to exhibit estrus was reduced with higher NEFA levels at 21 days pp (P = 0.01). Eighty-five cows were inseminated and 37 (44%) got pregnant after insemination. Higher NEFA levels, especially 14, 28, and 42 days pp, were associated with lower probability to inseminate a cow. Regarding the cows that were inseminated, no influence of BCS, BFT, or NEFA levels on pregnancy per artificial insemination was found. In conclusion, cows with higher loss of body condition and elevated NEFA concentrations had higher P4 concentrations during estrus, a reduced estrous activity and insemination rate, but no depression in pregnancy per artificial insemination.

Application of computed tomography for the evaluation of obstetrically relevant measurements in German Holstein-Friesian calves.

The aim of this study was to measure obstetrically relevant dimensions in calves manually and via computed tomography and to investigate their relationship with the dimensions of fetal body parts that are accessible to the obstetrician during early stages of vaginal delivery. Twenty Holstein-Friesian stillborn calves (Bos taurus) weighing 41.1 ± 3.7 kg (33.6-46.5 kg) were examined and the maximum height (H), width (W), circumference (C) and cross-sectional area (A) of their body was determined. The largest (P < 0.05) one-dimensional variable was the height of the thorax in the region of cranial sternum (H-Thorax; 29.3 ± 1.3 cm), and the largest (P < 0.05) two-dimensional variables were the cross-sectional area of the shoulder region at greater tubercles of the humeri (A-Shoulder; 307 ± 27 cm²) and of the thorax in the region of cranial sternum (A-Thorax; 306 ± 25 cm²). The dimensions of the front legs, which included the circumference of the canon bone and width of the fetlock joint, did not correlate (P > 0.05) with H-Thorax, A-Shoulder and A-Thorax. There were moderate significant correlations between the perpendicular height of the head (H-Head) and A-Thorax (r = 0.65, P < 0.05) and between the circumference of the head (C-Head) and A-Shoulder (r = 0.64, P < 0.05) and A-Thorax (r = 0.52, P < 0.05), but other relationships (P > 0.05) between the dimensions at the level of the head and H-Thorax, A-Shoulder and A-Thorax were not significant (P > 0.05). The results of this study show that the shoulders and thorax are the obstetrically most relevant calf dimensions, but the size of these variables cannot be reliably predicted by evaluating the dimensions of the forelimbs and head of calves during delivery.

Extraction methods in bovine obstetrics: comparison of the demanded energy and importance of calf and traction method in the variance of force and energy.

In a previous study we could demonstrate that in terms of the required forces alternate traction is preferable to simultaneous traction for the obstetrical delivery of calves. The aims of this study were to examine the required energies for delivery of calves and to compare the effects of the factors of calf and traction method on the forces and energies required for the delivery. In a biomechanical in vitro model 12 stillborn Holstein-Friesian calves were pulled through the pelvic specimen of a cow at a controlled speed using two electric motors. Traction was applied simultaneously (ST) to both legs or alternately (AT) to one leg at a time to advance it 10 cm (AT 10) or 5 cm (AT5). Energies on each limb were measured digitally using load cells. The lowest energy for the entrance of the elbows in the pelvis was necessary using AT10 (19.9 ± 7.2 kJ, P < 0.05). In contrast, for the entrance of the chest, AT10 (104.9 ± 24.7 kJ) demanded 9% (P < 0.01) and 16% (P < 0.001) more energy than AT5 (96.7 ± 21.0 kJ) and ST (90.5 ± 24.9 kJ), respectively. Simultaneous traction tended to be better than AT5 (P = 0.09). Variance component estimates revealed that the factor calf contributed the main effect to the emerging forces and required energy. The traction method was responsible for up to 13% of the variance in most of the cases, but it accounted for 42% of the variance regarding the forces on the lower limb as the chest entered the pelvis. Based on these findings, the decision of the clinician whether or not to perform a manual traction should depend mainly on the calf. However, when such a decision has been made, alternate limb traction, 10 cm at a time, should be used until both elbows have entered the pelvis and a simultaneous traction should then be applied to complete extraction of the chest.

Application of computed tomography for the evaluation of obstetrically relevant pelvic parameters in German Holstein-Friesian cows.

The aim of this study was to use computed tomography for the evaluation of the suitability of external pelvimetry to determine obstetrically relevant parameters. External pelvimetric measurements obtained in vivo using calipers and internal pelvimetric measurements obtained in vitro using computed tomography were taken in 30 German Holstein-Friesian cows (Bos taurus). All measurements were highly reproducible with intraclass correlation coefficients >or=98%. Hip width was the external variable with the highest correlation to internal variables, particularly pelvic inlet area and circumference, pelvic volume, medial horizontal diameter of the pelvic inlet, and the narrowest horizontal diameter of the midpelvis (r(2) > 0.60, P<0.0001). The pelvic inlet area and circumference, the pelvic volume, and the diagonal diameter of the pelvis were sufficiently predicted with the aid of external pelvic measurements and age (r(2)>or=0.80, P<0.0001). The results of this study show that external pelvimetry yields reliable information about the size of the pelvis when the age of the cow is considered.

Extraction forces in bovine obstetrics: an in vitro study investigating alternate and simultaneous traction modes.

Whether extraction of a calf in longitudinal anterior presentation should be carried out by simultaneous or alternate traction on the forelimbs remains controversial. Because most recommendations are based on empirical observations rather than on scientific studies, the aim of this study was to develop an in vitro model to objectively compare the forces occurring during alternate and simultaneous traction. In a biomechanical in vitro model, 12 dead Holstein-Friesian (Bos taurus) calves were pulled through the prepared pelvic specimen of a cow at a controlled speed using two electric motors. Traction was applied simultaneously (ST) to both legs or alternately (AT) to one leg at a time to advance the calf 5 cm (AT 5) or 10 cm (AT 10). Forces on each limb were measured digitally using load cells. In all cases, two peaks of maximum force occurred during the extraction of the cranial part of the body. The first peak was observed when the elbows were pulled into the pelvis, and the second peak occurred when the chest emerged from the pelvis. Up to and including entry of the elbows into the pelvis, the maximum force on a single limb (341+/-106 N) was lowest (P<0.01) using AT10. The maximum traction forces acting on a single limb using AT5 (411+/-86 N) and ST (431+/-127 N) did not differ (P>0.05). During extraction of the thorax, the maximum force acting on a single limb was lower (P<0.0001) using ST (352+/-98 N) compared with AT5 (432+/-79 N) and AT10 (547+/-115 N). Based on these findings, alternate-limb traction, 10 cm at a time, should be used until both elbows have entered the pelvis. Simultaneous traction should then be applied to both forelimbs to complete extraction of the chest.