Short communication: Effects of different blood buffers administered in electrolyte solution to grain-fed veal calves experiencing diarrhea.

Calf diarrhea can commonly lead to dehydration and metabolic acidosis due to the loss of fluid and electrolytes. The objective of this randomized clinical trial was to examine differences between treating male dairy calves experiencing diarrhea with either a basic bicarbonate electrolyte powder (BBP) composed of sodium bicarbonate (50.7 mmol/L); a mixed buffer powder (MBP) including sodium bicarbonate (33.8 mmol/L), sodium citrate (8.4 mmol/L), sodium acetate (6.3 mmol/L), and potassium citrate (1.9 mmol/L); or a liquid electrolyte (HAL) composed of sodium acetate (50.1 mmol/L). All 3 electrolyte solutions were standardized to provide 50 mmol/L blood buffers and a similarly strong ion difference (74.4, 74.9, and 82.6 mEq/L for BBP, MBP, and HAL, respectively). Holstein male calves (n = 80) were sourced from auction barns or local farms and delivered in 1 batch to the research facility. Calves were housed in individual pens and fed a 24% crude protein and 17% fat calf milk replacer (CMR) twice daily. Starter grain and water were offered ad libitum. Calves were randomly enrolled in 1 of the 3 treatments when experiencing either 2 consecutive days of a fecal score of 2 (runny, spreads easily) or 1 d with a fecal score of 3 (liquid devoid of solid material). Calves were blocked by the different enrollment criteria. The respective electrolyte solution was administered via esophageal tube 1 h after feeding CMR until the fecal score returned to 0 (normal consistency) or 1 (semiformed or pasty). Blood gas measurements were taken at 1, 8, and 24 h post the initial electrolyte feeding, and weight was measured at 1, 2, 7, 14, and 28 d postenrollment. Mixed repeated measure linear regression models were built to assess the effect that the electrolyte solutions had on the blood gas measurements and body weight. A total of 45 calves were enrolled in the trial with 14, 16, and 15 calves randomly assigned to the MBP, HAL, and BBP groups, respectively. As compared with BBP, MBP increased blood CO2 at 8 and 24 h, increased bicarbonate at 24 h, increased base excess at 8 and 24 h, and increased anion gap at 24 h. Calves in the BBP and HAL groups noted more severe eye recession when compared with the MBP group. Average daily gain did not differ between treatments at any time point. Although a severe dehydration challenge was not present, which should be considered a limitation of the study, MBP improved the acid-base status of calves compared with BBP, whereas HAL performed similarly to MBP.

Comparison of oral, intravenous, and subcutaneous fluid therapy for resuscitation of calves with diarrhea.

Neonatal diarrhea remains the primary cause of mortality in dairy calves around the world, and optimal treatment protocols are needed. The main goals of therapy are to restore hydration and electrolyte concentrations, correct strong ion (metabolic) acidemia, and provide nutritional support. Administration of oral electrolyte solutions (OES) has long been the primary method used to treat neonatal diarrhea in humans and calves because OES are capable of addressing each of the primary goals of therapy. In calves with moderate dehydration, we hypothesized that oral electrolytes would be as good as or better than small volumes of intravenous (IV) or subcutaneous (SC) fluids. Therefore, the main goal of this study was to compare the ability of a commercially available oral electrolyte solution (OES) administered alone or in combination with hypertonic saline with small volumes of IV or SC fluid therapy to resuscitate calves with diarrhea. Thirty-three Holstein calves from 5 to 14 d of age were utilized in this clinical trial. Diarrhea and dehydration were induced by adding sucrose to the milk replacer. In addition, hydrochlorothiazide and spironolactone were given orally and furosemide intramuscularly. Depression status, clinical hydration scores, fecal consistency, and body weight were recorded at regular intervals. Treatment began when calves had severe diarrhea and had a decrease in plasma volume of at least 10%. Calves were randomly assigned to 1 of 4 treatment groups of 8 to 9 calves per group: (1) OES; (2) OES with hypertonic saline (4 mL/kg, IV); (3) IV fluids (lactated Ringer's, 2 L); or (4) SC fluids (lactated Ringer's, 2 L). Treatments were given at 0 and 12 h. Changes in plasma volume, blood pH, electrolyte levels, and physical examination scores were determined before therapy and again at 1, 2, 4, 8, and 12 h after each treatment. All 4 treatments were ultimately successful in improving hydration as well as increasing blood pH; however, animals in both groups that received OES had much faster resuscitation than those in either the IV or SC fluid group. In conclusion, oral electrolyte products remain the gold standard for resuscitating diarrheic calves with moderate dehydration and acidemia and will likely perform better than small volumes of IV lactated Ringer's solution. Subcutaneous fluids by themselves are a poor treatment option and should be only be used as supportive therapy following the initial correction of hypovolemia and metabolic acidosis.

Effects of individual variation in length, condition and run-time on return rates of wild-reared Atlantic salmon Salmo salar smolts.

Groups of wild-reared Atlantic salmon Salmo salar smolts were captured during their seaward migration on a tributary of the River Conon, Scotland, U.K., from 1999 to 2014 and tagged with passive integrated transponders (PIT). Fish that subsequently returned to the river after growing at sea were recorded automatically by a PIT-detector in a fish pass. Return rate was related directly to length and condition and inversely to day of the year that the smolt was tagged. Over years, as the study progressed, there was a significant increase in the proportion of smolts returning after two or more years at sea and no trend in returns of salmon having spent one winter at sea. There was no trend in the date of return of salmon across the study period. Fish that had spent more winters at sea returned earlier in the year.

Pharmacokinetics and distribution in interstitial and pulmonary epithelial lining fluid of danofloxacin in ruminant and preruminant calves.

The objective of this study was to compare active drug concentrations in the plasma vs. different effector compartments including interstitial fluid (ISF) and pulmonary epithelial lining fluid (PELF) of healthy preruminating (3-week-old) and ruminating (6-month-old) calves. Eight calves in each age group were given a single subcutaneous (s.c.) dose (8 mg/kg) of danofloxacin. Plasma, ISF, and bronchoalveolar lavage (BAL) fluid were collected over 96 h and analyzed by high-pressure liquid chromatography. PELF concentrations were calculated by a urea dilution assay of the BAL fluids. Plasma protein binding was measured using a microcentrifugation system. For most preruminant and ruminant calves, the concentration-time profile of the central compartment was best described by a two-compartment open body model. For some calves, a third compartment was also observed. The time to maximum concentration in the plasma was longer in preruminating calves (3.1 h) vs. ruminating calves (1.4 h). Clearance (CL/F) was 385.15 and 535.11 mL/h/kg in preruminant and ruminant calves, respectively. Ruminant calves maintained higher ISF/plasma concentration ratios throughout the study period compared to that observed in preruminant calves. Potential reasons for age-related differences in plasma concentration-time profiles and partitioning of the drug to lungs and ISF as a function of age are explored.

Slow and steady cell shrinkage reduces osmotic stress in bovine and murine oocyte and zygote vitrification.

STUDY QUESTION: Does the use of a new cryoprotectant agent (CPA) exchange protocol designed to minimize osmotic stress improve oocyte or zygote vitrification by reducing sublethal cryodamage? SUMMARY ANSWER: The use of a new CPA exchange protocol made possible by automated microfluidics improved oocyte and zygote vitrification with superior morphology as indicated by a smoother cell surface, higher sphericity, higher cytoplasmic lipid retention, less cytoplasmic leakage and higher developmental competence compared with conventional methods. WHAT IS KNOWN ALREADY: The use of more 'steps' of CPA exposure during the vitrification protocol increases cryosurvival and development in the bovine model. However, such an attempt to eliminate osmotic stress is limited by the practicality of performing numerous precise pipetting steps in a short amount of time. STUDY DESIGN, SIZE, DURATION: Murine meiotically competent germinal vesicle intact oocytes and zygotes were harvested from the antral follicles in ovaries and ampulla, respectively. Bovine ovaries were obtained from a local abattoir at random stages of the estrous cycle. A total of 110 murine oocytes, 802 murine zygotes and 52 bovine oocytes were used in this study. PARTICIPANTS/MATERIALS, SETTING, METHODS: Microfluidic devices were fabricated using conventional photo- and soft-lithography. CPAs used were 7.5% ethylene glycol (EG) and 7.5% dimethyl sulfoxide (DMSO) for equilibration solution and 15% EG, 15% DMSO and 0.5 M sucrose for vitrification solution. End-point analyses include mathematical modeling using Kedem-Katchalsky equations, morphometrics assessed by conventional and confocal microscopy, cytoplasmic lipid quantification by nile red staining, cytoplasmic leakage quantification by fluorescent dextran intercalation and developmental competence analysis by 96 h embryo culture and blastomere quantification. MAIN RESULTS AND THE ROLE OF CHANCE: The automated microfluidics protocol decreased the shrinkage rate of the oocyte and zygote by 13.8 times over its manual pipetting alternative. Oocytes and zygotes with a lower shrinkage rate during CPA exposure experienced less osmotic stress resulting in better morphology, higher cell quality and improved developmental competence. This microfluidic procedure resulted in murine zygotes with a significantly smoother cell surface (P < 0.001), more spherical cellular morphology (P < 0.001), increased cytoplasmic lipid retention in vitrified and warmed bovine oocytes (P < 0.01), decreased membrane perforations and cytoplasmic leakage in CPA-exposed murine zygotes (P < 0.05) and improved developmental competence of vitrified and warmed murine zygotes (P < 0.05) than CPA exposure using the current clinically used manual pipetting method. LIMITATIONS, REASONS FOR CAUTION: It is necessary to design the microfluidic device to be more user-friendly for widespread use. WIDER IMPLICATIONS OF THE FINDINGS: The theory and approach of eliminating osmotic stress by decreasing shrinkage rate is complementary to the prevalent osmotic stress theory in cryobiology which focuses on a minimum cell volume at which the cells shrink. The auto-microfluidic protocol described here has immediate applications for improving animal and human oocyte, zygote and embryo cryopreservation. On a fundamental level, the clear demonstration that at the same minimum cell volume, cell shrinkage rate affects sublethal damage should be broadly useful for cryobiology. STUDY FUNDING/COMPETING INTERESTS: This project was funded by the National Institutes of Health and the University of Michigan Reproductive Sciences Program. The authors declare no conflicts of interest.

Concentration of anti-Müllerian hormone in dairy heifers is positively associated with productive herd life.

Reliable biomarkers predictive of productive herd life (time in herd after birth of first calf) have heretofore not been discovered in dairy cattle. However, circulating concentrations of anti-Müllerian hormone (AMH) are positively associated with number of follicles or antral follicle count (AFC), ovarian function, and fertility, and approximately 25% of cows have a relatively low AFC and low AMH concentrations. The present study tested the hypothesis that heifers with the lowest AMH concentrations have suboptimal fertility and are removed from a herd for poor reproductive performance at a greater rate, and therefore have a shorter productive herd life compared with age-matched herdmates with higher AMH. To test this hypothesis, 11- to 15-mo-old Holstein heifers (n=281) were subjected to a single measurement of AMH. All heifers not removed from the herd had the opportunity to complete 2 lactations and start their third lactation after calving. During this time, performance and health parameters for each individual were recorded daily by herd managers. Results showed that the quartile of heifers with the lowest AMH concentration also had, on average, a shorter productive herd life (by 196 d), a reduced survival rate after birth of the first calf, the lowest level of milk production (first lactation), the lowest total percentage of cows pregnant (across all lactations), the highest culling rates (first and second lactations and overall), and the highest culling rate for poor reproduction (first lactation) compared with age-matched herdmates with higher AMH. We concluded that a single determination of AMH concentration in young adult dairy heifers may be a simple diagnostic method to predict herd longevity, and AMH may be a useful phenotypic marker to improve longevity of dairy cows.

Application of embryo transfer using in vitro produced embryos: intrinsic factors affecting efficiency.

Embryo transfer remains a viable approach to increase propagation of offspring from high genetic merit females. Although it is now over 60 years since the report of the birth of the first calf from embryo transfer, utilisation of embryo transfer technology worldwide is not widespread. Limitations of conventional procedures for superovulation and embryo transfer are not limited to but include variability in response to superovulation, the labour intensive nature of superovulation procedures, time required between collections and cost of technology. Recently, harvest of ova and transfer of in vitro produced embryos has received more attention as a potential alternative to conventional superovulation and subsequent embryo transfer. Aspiration of follicular ova and in vitro embryo production offers potential advantages in reducing loss of female germplasm occurring through the natural process of ovarian follicular atresia, can increase yield of embryos from elite donor cows beyond that possible with superovulation, and provides a means of salvaging genetic material from valuable animals at slaughter or those culled for disease control or other reasons. Recent evidence indicates poor ovum quality is a major factor limiting in vitro embryo production and discovery of a role for intrinsic factors such as ovum follistatin and cumulus cell cathepsins in control of ovum quality has led to ongoing research on new technologies to increase yield of transferable embryos.

Mice deficient for corticotropin-releasing hormone receptor-2 display anxiety-like behaviour and are hypersensitive to stress.

Corticotropin-releasing hormone (Crh) is a critical coordinator of the hypothalamic-pituitary-adrenal (HPA) axis. In response to stress, Crh released from the paraventricular nucleus (PVN) of the hypothalamus activates Crh receptors on anterior pituitary corticotropes, resulting in release of adrenocorticotropic hormone (Acth) into the bloodstream. Acth in turn activates Acth receptors in the adrenal cortex to increase synthesis and release of glucocorticoids. The receptors for Crh, Crhr1 and Crhr2, are found throughout the central nervous system and periphery. Crh has a higher affinity for Crhr1 than for Crhr2, and urocortin (Ucn), a Crh-related peptide, is thought to be the endogenous ligand for Crhr2 because it binds with almost 40-fold higher affinity than does Crh. Crhr1 and Crhr2 share approximately 71% amino acid sequence similarity and are distinct in their localization within the brain and peripheral tissues. We generated mice deficient for Crhr2 to determine the physiological role of this receptor. Crhr2-mutant mice are hypersensitive to stress and display increased anxiety-like behaviour. Mutant mice have normal basal feeding and weight gain, but decreased food intake following food deprivation. Intravenous Ucn produces no effect on mean arterial pressure in the mutant mice.

Effect of experimental feed additives on aflatoxin in milk of dairy cows fed aflatoxin-contaminated diets.

Three studies were conducted to determine the potential of experimental feed additives (EFAs), clays or non-digestible yeast oligosaccharides, to reduce milk aflatoxin (AFM1) concentrations in lactating Holstein cows consuming aflatoxin-contaminated diets. All studies included a pre-treatment period and a 2-week experimental period in a randomized block design. During the pre-treatment period, cows received a total mixed ration (TMR) with no aflatoxin contamination. During both experimental weeks, all cows were fed a TMR containing aflatoxin-contaminated corn. During experimental week 1, cows received no EFA's in the TMR, but EFA's were included in the TMR for the second experimental week. In studies 1 and 2, the experimental period consisted of 2 weeks each lasting 7 days with 12 cows per treatment. Aflatoxin M1 concentrations were analysed by HPLC for milk samples collected on days 5-7 and days 11-14. In various experiments, treatments included control (no EFA), 100 g/cow daily of experimental Lallemand(®) product, 10 g/cow daily of MTB-100(®) -2004, (Alltech, Inc.), 10 g/cow daily of MTB-100(®) -2006, (Alltech, Inc.), 10 g/cow daily of experimental Alltech(®) product (Alltech, Inc.) and 227 g/cow daily of Astra-Ben 20(®) (AB-20(®) ; Prince Agri Products, Inc.). In study 3, the experimental period of 2 weeks each lasting 8 days and milk samples were collected from day 4 to 8 and day 11 to 16. Milk samples from study 3 were analysed for AFM1 concentrations by ELISA. For all experiments, changes in AFM1 concentrations because of the addition of EFA's were calculated. Four of the five EFAs tested in this study had no significant effect on AFM1 concentrations. However, the addition of AB-20(®) resulted in a significant decrease in AFM1 concentrations (60.4%). In summary, the addition of AB-20(®) to the diet of cattle appears to be effective for significantly reducing AFM1 concentrations in the milk of cows fed an aflatoxin-contaminated diet.

Short communication: Evaluation of serum immunoglobulin G concentrations using an automated turbidimetric immunoassay in dairy calves.

The absorption of maternal antibodies associated with colostrum feeding is critical to the health of calves. Multiple assays have been described to assess serum immunoglobulin G (IgG) concentrations in calves. However, none are ideal for routine use on farms. The purpose of this study was to evaluate the reliability of a new commercially available immunoassay and portable analyzer for measuring serum IgG concentrations in dairy calves. Serum from 100 Holstein calves that had received colostrum was collected for this study. Immunoglobulin G concentrations were run on each calf using both the rapid immunoassay method and radial immunodiffusion assay. Serum IgG concentrations in calves from this study ranged from 460 to 3,640 mg/dL (mean ± SD: 1,515 ± 71) as measured by radial immunodiffusion and 402 to 3,586 mg/dL (mean 1,473 ± 70) as measured by the immunoassay. Based on regression analysis, the automated results closely paralleled those obtained by radial immunodiffusion with a coefficient of determination value of 0.98. Based on the results of this study, the immunoassay technique using the portable analyzer represents a reliable method that can be run within 15 min and provide an accurate serum IgG level. Although the cost is not insignificant, this assay could be easily implemented on a dairy farm to help monitor transfer of passive immunity.

Plasma pharmacokinetics and milk residues of flunixin and 5-hydroxy flunixin following different routes of administration in dairy cattle.

The objective of this study was to determine if the plasma pharmacokinetics and milk elimination of flunixin (FLU) and 5-hydroxy flunixin (5OH) differ following intramuscular and subcutaneous injection of FLU compared with intravenous injection. Twelve lactating Holstein cows were used in a randomized crossover design study. Cows were organized into 2 groups based on milk production (<20 or >30 kg of milk/d). All cattle were administered 2 doses of 1.1mg of FLU/kg at 12-h intervals by intravenous, intramuscular, and subcutaneous injections. The washout period between routes of administration was 7d. Blood samples were collected from the jugular vein before FLU administration and at various time points up to 36 h after the first dose of FLU. Composite milk samples were collected before FLU administration and twice daily for 5d after the first dose of FLU. Samples were analyzed by ultra-HPLC with mass spectrometric detection. For FLU plasma samples, a difference in terminal half-life was observed among routes of administration. Harmonic mean terminal half-lives for FLU were 3.42, 4.48, and 5.39 h for intravenous, intramuscular, and subcutaneous injection, respectively. The mean bioavailability following intramuscular and subcutaneous dosing was 84.5 and 104.2%, respectively. The decrease in 5OH milk concentration versus time after last dose was analyzed with the nonlinear mixed effects modeling approach and indicated that both the route of administration and rate of milk production were significant covariates. The number of milk samples greater than the tolerance limit for each route of administration was also compared at each time point for statistical significance. Forty-eight hours after the first dose, 5OH milk concentrations were undetectable in all intravenously injected cows; however, one intramuscularly injected and one subcutaneously injected cow had measurable concentrations. These cows had 5OH concentrations above the tolerance limit at the 36-h withdrawal time. The high number of FLU residues identified in cull dairy cows by the United States Department of Agriculture Food Safety Inspection Service is likely related to administration of the drug by an unapproved route. Cattle that received FLU by the approved (intravenous) route consistently eliminated the drug before the approved withdrawal times; however, residues can persist beyond these approved times following intramuscular or subcutaneous administration. Cows producing less than 20 kg of milk/d had altered FLU milk clearance, which may also contribute to violative FLU residues.

Low numbers of ovarian follicles ≥3 mm in diameter are associated with low fertility in dairy cows.

The total number of ovarian follicles ≥ 3mm in diameter (antral follicle count, AFC) during follicular waves varies among cattle of similar age, but AFC is highly repeatable within individuals. We hypothesized that lower AFC could be associated with reduced fertility in cattle. The AFC was assessed by ultrasonography for 2 d consecutively during the first wave of follicular growth of the estrous cycle, 4.6±1.43 d (mean ± SD) after estrus, in 306 Holstein-Friesian dairy cows approximately 70 d postpartum. Cows were classified into 3 groups based on AFC: low (AFC ≤15), intermediate (AFC=16 to 24), and high (AFC ≥25). During the cycle in which AFC was assessed and in subsequent cycles, cows were artificially inseminated (AI) following detection of estrus, and pregnancy status was assessed using ultrasonography. Cows with high AFC had 3.34 times greater odds of being pregnant at the end of the breeding season compared with cows with low AFC; the odds of a successful pregnancy at first service were 1.75 times greater in the intermediate compared with the low group. The predicted probability of a successful pregnancy by the end of the breeding period (length of breeding season was 86±16.3 d) was 94, 88, and 84% for the high, intermediate, and low AFC groups, respectively. No difference was evident among groups in 21-d submission rate (proportion of all cows detected in estrus and submitted for AI in the first 21 d of the breeding season), but the interval from calving to conception was shorter in the high (109.5±5.1 d) versus low (117.1±4 d) group, and animals with intermediate AFC received fewer services during the breeding season (2.3±0.1) compared with animals with low AFC (2.7±0.1). Lactating cows with ≤15 ovarian follicles have lower reproductive performance compared with cows with higher numbers of follicles, but the existence of a positive association between high numbers of ovarian follicles and fertility is yet to be established.

Effects of maternal environment during gestation on ovarian folliculogenesis and consequences for fertility in bovine offspring.

Mammals such as cattle, swine, sheep and humans are born with a highly variable number of ovarian follicles and oocytes in the ovaries that dwindle during ageing and are never replenished. This variation in the ovarian reserve is reflected in the numbers of antral follicles in the ovaries at all ages after birth. As numbers of follicles in ovaries are determined during gestation, the role of maternal nutrition and health during gestation (at time of ovarian development in their foetuses) has been investigated as factors that may impact oogonia proliferation and thus follicle numbers post-natally. These studies have found that both nutrition and health impact numbers of follicles in their offspring. The idea that numbers of follicles and oocytes in ovaries impact fertility is a long-held belief in reproductive biology. This has recently been tested in cattle, and it has been shown that cows with a relatively high number of antral follicles in ovaries have higher pregnancy rates, shorter calving to conception intervals and fewer artificial inseminations during the breeding season compared with cows with a lower number of follicles, and similarly, heifers with many follicles had higher pregnancy rates than those with fewer follicles. Studies summarized in this review highlight the importance of the maternal environment during gestation in determining the size of the ovarian reserve in their offspring and also the contribution of the ovarian reserve to subsequent fertility in cattle.

FSH stimulated bovine granulosa cell steroidogenesis involves both canonical and noncanonical WNT signaling.

Gonadotrophins play key roles in follicular development; however, the underlying molecular mechanisms are not fully understood. Follicle stimulating hormone (FSH) regulation of aromatase and subsequent estradiol (E2) production relies on ß-catenin, a key effector of WNT signaling. We previously demonstrated that treatment with the canonical WNT inhibitor, IWR-1, reduced FSH induced bovine granulosa cell E2 production in vitro. Here we demonstrated that intrafollicular injection in vivo with IWR-1 alters steroidogenesis and triggers a significant decrease in estrogen to progesterone ratio in the IWR-1 treated follicles compared to diluent injected control follicles. We next examined markers of canonical and noncanonical WNT signaling in dominant and subordinate follicles collected at different stages of follicular development and showed that protein for both CTNNB1 (canonical pathway) and phosphorylated (p)-LEF1 (noncanonical pathway) was significantly elevated in dominant compared to subordinate follicles at the early dominance stage of development. Therefore, we hypothesized that canonical and/or noncanonical WNT ligands modulate FSH stimulated E2 production. Hence, we examined the effects of specific WNT ligands on FSH stimulated E2 production in the absence of endogenous WNT production in vitro. Universal WNT signaling inhibitor, LGK-974 was able to inhibit FSH stimulation of E2 and reduce the abundance of proteins linked to canonical and noncanonical WNT pathway activation. Supplementation with the canonical ligand WNT2b did not affect the inhibitory effects of LGK-974 on FSH stimulated E2 production but rescued the LGK-974 mediated inhibition of CTNNB1 (canonical pathway) but not p-LEF1, p-JNK or p-P38 abundance (noncanonical pathway) abundance. In contrast, WNT5a treatment rescued FSH stimulated estradiol production and indices of activation of both the canonical (CTNNB1) and noncanonical (p-LEF1, p-JNK and p-P38) WNT signaling pathways in LGK-974 treated granulosa cells. Taken together, these results suggest that both canonical and noncanonical WNT pathways activation is linked to FSH stimulation of E2 production by bovine granulosa cells.

Does size matter in females? An overview of the impact of the high variation in the ovarian reserve on ovarian function and fertility, utility of anti-Müllerian hormone as a diagnostic marker for fertility and causes of variation in the ovarian reserve in cattle.

The mechanism whereby the inherently high variation in ovary size and the total number of high-quality oocytes in ovaries (ovarian reserve) impact on ovarian function and fertility, diagnostics to measure the size of the ovarian reserve and the factors that cause variation in the ovarian reserve are unknown. Our results show that cattle can be phenotyped reliably based on the number of antral follicles growing during follicular waves (antral follicle count, AFC). Young adult cattle with a consistently low v. a high AFC have smaller gonads, a markedly diminished ovarian reserve and many other phenotypic characteristics usually associated with ovarian aging and infertility. A powerful new approach based on a single measurement of serum concentration of anti-Müllerian hormone (AMH) is described to test the longstanding hypothesis that the size of the ovarian reserve is positively associated with fertility. Also, new evidence shows that maternal environment has a critical role in regulation of the high variation in the ovarian reserve and perhaps fertility in offspring. These results support the conclusion that the inherently high variation in the ovarian reserve, potentially caused by alterations in the maternal environment, has a negative impact on ovarian function that may result in suboptimal fertility in young adult cattle, and a single AMH measurement can be used reliably in future studies to determine if fertility is suboptimal in young adult cattle with low circulating AMH concentrations and a correspondingly diminished ovarian reserve.

Short communication: serum immunoglobulin G and total protein concentrations in dairy calves fed a colostrum-replacement product.

Neonatal calf health is largely dependent on the ingestion and absorption of maternally derived antibodies via colostrum administration. The objective of this study was to evaluate the efficacy of a commercially available plasma-derived colostrum-replacement (CR) product as compared with bovine colostrum. Holstein calves were removed from the dam immediately after birth and randomly allocated to 1 of 3 groups. Group 1 calves (n=22) were fed 1 package of the CR product; group 2 calves (n=22) were fed 2 packages of the CR product; and group 3 calves (n=22) were fed 3 L of bovine colostrum. Blood samples were collected from all calves 24h after colostrum or CR feeding and analyzed for serum IgG and total protein concentrations. Calves fed bovine colostrum had significantly higher serum IgG and total protein concentration than calves in either group fed the CR product. Group 1 calves (1 package of CR product) had a significantly higher incidence of failure of transfer of passive immunity than calves in groups 2 or 3. The results of this study indicated that 2 packages of this CR product achieved adequate IgG concentrations in calves. However, calves fed 1 package of this CR product consistently had failure of transfer of passive immunity.

Paroxysmal high-grade second-degree and persistent third-degree atrioventricular block in cats.

INTRODUCTION: Both paroxysmal high-grade second-degree and persistent third-degree atrioventricular block (AVB) are recognised in cats. Our aim was to document the presentation, echocardiographic data, comorbidities and outcome in affected cats from a single referral hospital, including those that underwent epicardial pacemaker implantation (EPI). ANIMALS, MATERIALS AND METHODS: This retrospective study included 64 cats diagnosed with persistent third-degree or paroxysmal high-grade AVB, for which detailed patient history was available. Non-parametric testing, Kaplan-Meier curves and Cox proportional hazard testing were performed. RESULTS: Atrioventricular block was persistent in 43 cats (67%) and paroxysmal in 21 (33%). Forty-seven cats (74%) were referred for cardiac complaints (e.g. collapse, arrhythmia, tachypnea), 6 (9%) had non-specific complaints and AVB was an incidental finding in 11 cats (17%). Median duration of clinical signs prior to presentation was 21 days (1-1138 days). Thirty-nine (63%) cats had echocardiographic abnormalities; 13 (20%) presented with congestive heart failure. Forty-five (70%) cats had one or more comorbidities. Fifteen cats underwent EPI with immediate resolution of signs in 12 cats. Following EPI, two and four cats experienced major and minor complications, respectively. Forty-seven cats died; median survival time was 799 days (all-cause mortality). Cardiac-related death occurred in 17 cats (36%); median survival in these cats was 132 days. Heart failure on presentation was the only independent risk factor for cardiac death (p=0.002). CONCLUSIONS: Outcome in cats with AVB was variable, although most had good medium- to long-term survival. Cardiac death occurred in a minority of cats. Pacemaker implantation was effective in relieving clinical signs.

Evidence that high variation in antral follicle count during follicular waves is linked to alterations in ovarian androgen production in cattle.

Androgens have an important role in ovarian follicular growth and function, but circulating androgen concentrations are also associated with ovarian dysfunction, cardiovascular disease, and metabolic disorders in women. The extent and causes of the variation in androgen production in individuals, however, are unknown. Because thecal cells of follicles synthesize androstenedione and testosterone, variation in production of these androgens is hypothesized to be directly related to the inherently high variation in number of healthy growing follicles in ovaries of individuals. To test this hypothesis, we determined whether thecal CYP17A1 mRNA (codes for a cytochrome P450 enzyme involved in androgen synthesis), LH-induced thecal androstenedione production, androstenedione concentrations in follicular fluid, and circulating testosterone concentrations were lower in cattle with relatively low versus high number of follicles growing during follicular waves and whether ovariectomy reduced serum testosterone concentrations. Results demonstrated that cattle with a low follicle number had lower (P<0.05) abundance of CYP17A1 mRNA in thecal cells, reduced (P<0.01) capacity of thecal cells to produce androstenedione in response to LH, lower (P<0.01) androstenedione concentrations in ovulatory follicles, and lower (P<0.02) circulating testosterone concentrations during estrous cycles compared with animals with high follicle number. Also, serum testosterone in cattle with low or high follicle number was reduced by 63 and 70%, respectively, following ovariectomy. In conclusion, circulating androgen concentrations are lower in cattle with low versus high number of follicles growing during follicular waves, possibly because of a reduced responsiveness of thecal cells to LH.

Inherent capacity of the pituitary gland to produce gonadotropins is not influenced by the number of ovarian follicles > or = 3 mm in diameter in cattle.

We hypothesised that higher serum FSH concentrations in cattle with low v. high follicle numbers during follicular waves are caused by a different capacity of the pituitary gland to produce gonadotropins. Dairy cows with high (> or = 30; n = 5) and low (< or = 15; n = 5) follicle numbers were selected and serum concentrations of oestradiol and FSH during an oestrous cycle were measured. Cows were ovariectomised at oestrus and bled frequently up to 8 days after ovariectomy. After 33 days, cows were injected with gonadotropin-releasing hormone (GnRH) and bled intensively up to 8 h after GnRH injection. One day later, animals were injected with follicular fluid (FF) from bovine follicles and were bled intensively up to 2 days after the first injection. Serum concentrations of FSH and LH were measured. After 2 days, cows were killed and their pituitary glands collected. Prior to ovariectomy, serum oestradiol concentrations were similar between groups, whereas FSH concentrations were higher in cattle with low v. high numbers of follicles. No differences were detected in serum gonadotropin concentrations after ovariectomy, GnRH injection or FF challenge between groups. The results indicate that the inherent capacity of the pituitary gland to secrete gonadotropins does not differ between cattle with high v. low numbers of follicles during follicular waves.

Efficacy and pharmacokinetics of pantoprazole in alpacas.

BACKGROUND: Despite frequent clinical use, information about the pharmacokinetics and efficacy of pantoprazole in camelids is not available. OBJECTIVES: To examine the pharmacokinetics of both IV and SC pantoprazole and to determine whether pantoprazole administration would increase 3rd compartment pH in alpacas. ANIMALS: Six healthy adult alpacas. METHODS: Alpacas were fitted with a 3rd compartment cannula for measuring gastric pH. After recovery, alpacas received 1 mg/kg pantoprazole IV, q24h for 3 days or 2 mg/kg SC q24h for 3 days. Alpacas received both IV and SC pantoprazole, with a minimum of 3 weeks between treatments. Third compartment pH was recorded and plasma samples were taken for pharmacokinetic analysis. RESULTS: Pantoprazole induced a slow but sustained increase in 3rd compartment pH when given by both the IV and SC routes. Third compartment pH was significantly increased as compared with baseline values (1.81+/-0.7; mean+/-SD) at 24 (2.47+/-0.8), 48 (3.53+/-1.0) and 72 hours (4.03+/-1.3) after daily IV administration of pantoprazole. Third compartment pH increased from 1.73+/-0.6 at baseline to 3.05+/-1.1, 4.02+/-1.4, and 3.61+/-1.6 at 24, 48, and 72 hours after SC administration, respectively. Pharmacokinetic analysis demonstrated that pantoprazole had a short elimination half-life (0.47+0.06 h) and a high clearance rate (12.2+/-2.9 mL/kg/min) after both IV and SC administration. CONCLUSIONS AND CLINICAL RELEVANCE: Based on the results of this study, pantoprazole represents a safe and effective drug for increasing 3rd compartment pH in camelids. Either IV or SC administration is likely to be an effective treatment for gastric ulcers.