Trace Mineral Feeding and Assessment.

Trace minerals are commonly supplemented in ruminant feeds as many common feeds are deficient in one or more of the trace minerals. The requirement of trace minerals needed to prevent classic nutrient deficiencies is well established, thus those cases most commonly occur when no supplement is provided. The more common challenge for the practitioner is to determine if additional supplementation is needed to enhance production or decrease disease occurrence.

Trace Mineral Supplementation of Beef Cattle in Pasture Environments.

The United States Department of Agriculture defines pastureland as "A land cover/use category of land managed primarily for the production of introduced forage plants for livestock grazing." The purpose of this article is to review trace mineral supplementation for beef cattle in this environment. Supplementation of trace minerals in these environments is accomplished with the use of a trace mineralized salt or a complete mineral-vitamin product that contains macrominerals, trace minerals, and vitamins. The form of the supplement may influence uptake and utilization. Supplementation may be augmented with pulse dosing with injectables or oral products.

Comparison of luteolysis and timed artificial insemination pregnancy rates after administration of PGF2α in the muscle or the ischiorectal fossa in cattle.

Prostaglandin F2α (PGF2α) is commonly injected intramuscularly (IM) in female cattle in synchronization protocols. A novel site for administration of PGF2α that improves beef quality assurance is the ischiorectal fossa (IRF). The objective of this study was to determine whether administration of PGF2α in the IRF results in a similar physiological response to an intramuscular injection. Yearling angus-cross heifers (n = 112) were blocked by weight and randomly assigned within blocks to be injected with 5 mL PGF2α either IM in the neck or in the IRF. Blood samples taken at 0, 8, 16, 24, 36, and 48 h post-injection were analyzed for serum progesterone concentration using a radioimmunoassay. Progesterone concentration curves for each heifer were plotted to determine luteolysis. The median times to luteolysis for neck and IRF injections were 18.1 h and 20.0 h, respectively (p = 0.06). Angus cross commercial beef cows (n = 1471) at least 30 days post-partum were blocked by age and randomly assigned within blocks to be injected with 5 mL PGF2α either IM in the neck muscle or in IRF as part of a 7-Day CO-Synch + CIDR synchronization protocol. Pregnancy diagnosis was performed via ultrasound at 60 days post insemination. Results were analyzed with Proc Glimmix (SAS). Pregnancy rates for neck and IRF injections were 52.6% and 57.2%, respectively (p = 0.06). In summary, injection of PGF2α in the IRF for synchronization of estrus and luteolysis did not differ from IM injection. Utilizing the ischiorectal fossa as an injection site for PGF2α may serve as an alternative that more closely aligns with beef quality assurance.

Associations of diet and breed with recurrence of calcium oxalate cystic calculi in dogs.

OBJECTIVE: To evaluate the long-term risk of recurrence of calcium oxalate (CaOx) cystic calculi in dogs of various breeds fed 1 of 2 therapeutic diets. DESIGN: Retrospective cohort study. Animals-135 dogs with a history of CaOx cystic calculi. PROCEDURES: Medical records for 4 referral hospitals were searched to identify dogs that had had CaOx cystic calculi removed. Owners were contacted and medical records evaluated to obtain information on postoperative diet, recurrence of signs of lower urinary tract disease, and recurrence of cystic calculi. Dogs were grouped on the basis of breed (high-risk breeds, low-risk breeds, and Miniature Schnauzers) and diet fed after removal of cystic calculi (diet A, diet B, and any other diet [diet C], with diets A and B being therapeutic diets formulated to prevent recurrence of CaOx calculi). RESULTS: Breed group was a significant predictor of calculi recurrence (as determined by abdominal radiography or ultrasonography), with Miniature Schnauzers having 3 times the risk of recurrence as did dogs of other breeds. Dogs in diet group A had a lower prevalence of recurrence than did dogs in diet group C, but this difference was not significant in multivariable analysis. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that Miniature Schnauzers had a higher risk of CaOx cystic calculi recurrence than did dogs of other breeds. In addition, findings suggested that diet may play a role in decreasing recurrence, but future prospective studies are needed to validate these observations.

Trace mineral feeding and assessment.

This article gives practitioners an overview of trace mineral requirements, supplementation, and assessment in dairy herds. In addition, a step-by-step guideline for liver biopsy in cows is provided with interpretive results from a sample herd.

Fibre digestibility, abundance of faecal bacteria and plasma acetate concentrations in overweight adult mares.

The purpose of the present study was to compare digestibility of grass hay, faecal and plasma volatile fatty acid (VFA) concentrations, and faecal bacterial abundance in overweight and moderate-condition mares. Five overweight adult mixed-breed mares and five adult mixed-breed mares in moderate condition were housed individually and limit-fed orchard grass (Dactylis glomerata) hay at 20 g/kg body weight (as fed) daily for 14 d. Forage DM and fibre digestibility were determined using AOAC methods; digestible energy was measured using bomb calorimetry; plasma and faecal VFA concentrations were determined by use of GC and MS; faecal Firmicutes, Bacteroidetes, Fibrobacter succinogenes, Ruminococcus flavefaciens and total bacteria abundance was determined by quantitative real-time PCR using previously designed phylum-specific 16S ribosomal RNA gene primers. No differences in hay digestibility, faecal VFA concentrations or faecal bacterial abundance were detected between overweight and moderate-condition mares. Mean plasma acetate concentrations were higher (P = 0·03) in overweight (1·55 (range 1·43-1·65) mmol/l) v. moderate-condition (1·39 (range 1·22-1·47) mmol/l) mares. We conclude that the higher plasma acetate in overweight mares should be further investigated as a potential link between gut microbes and obesity in horses.

A study of the level and dynamics of Eimeria populations in naturally infected, grazing beef cattle at various stages of production in the Mid-Atlantic USA.

There is little information available on the species dynamics of eimerian parasites in grazing cattle in the central Appalachian region of the United States. Therefore, the objective of this study was to describe the level of infection and species dynamics of Eimeria spp. in grazing beef cattle of various age groups over the course of a year in the central Appalachian region. Rectal fecal samples were collected from male and female calves (n=72) monthly from May through October 2005, heifers only (n=36) monthly from November 2005 to April 2006, and cows (n=72) in May, July, and September, 2005. Eimeria spp. oocysts were seen in 399 of 414 (96%) fecal samples collected from the calves from May through October. Fecal oocysts counts (FOC) in the calves were lower (P<0.05) in May than all other months and no significant differences were detected from June through September. Eimeria spp. oocysts were detected in 198 of 213 (92%) of fecal samples collected from the 36 replacement heifers monthly from November to April and monthly mean FOC did not differ during this time period. The prevalence of oocyst shedding increased to 100% in calves in September and remained near 100% in the replacement heifers during the sampling period. Eimeria spp. oocysts were also detected in 150 of 200 (75%) samples collected in May, July, and September from the cows and mean FOC did not differ significantly over the sampling period. Eimeria spp. composition was dominated by Eimeria bovis in fecal samples collected from calves, replacement heifers and cows. Mixed Eimeria spp. infections were, however, common in all groups and 13 Eimeria spp. oocysts were identified throughout the sampling period.

Characterization of the fecal bacteria communities of forage-fed horses by pyrosequencing of 16S rRNA V4 gene amplicons.

The diversity of the equine fecal bacterial community was evaluated using pyrosequencing of 16S rRNA gene amplicons. Fecal samples were obtained from horses fed cool-season grass hay. Fecal bacteria were characterized by amplifying the V4 region of bacterial 16S rRNA gene. Of 5898 mean unique sequences, a mean of 1510 operational taxonomic units were identified in the four fecal samples. Equine fecal bacterial richness was higher than that reported in humans, but lower than that reported in either cattle feces or soil. Bacterial classified sequences were assigned to 16 phyla, of which 10 were present in all samples. The largest number of reads belonged to Firmicutes (43.7% of total bacterial sequences), Verrucomicrobia (4.1%), Proteobacteria (3.8%), and Bacteroidetes (3.7%). The less abundant Actinobacteria, Cyanobacteria, and TM7 phyla presented here have not been previously described in the gut contents or feces of horses. Unclassified sequences represented 38.1% of total bacterial sequences; therefore, the equine fecal microbiome diversity is likely greater than that described. This is the first study to characterize the fecal bacterial community in horses by the use of 16S rRNA gene amplicon pyrosequencing, expanding our knowledge of the fecal microbiota of forage-fed horses.

Influence of two-stage weaning with subsequent transport on body weight, plasma lipid peroxidation, plasma selenium, and on leukocyte glutathione peroxidase and glutathione reductase activity in beef calves.

An experiment was conducted to assess the effects of two-stage weaning and subsequent transport on oxidative stress markers in calves. Thirty-six crossbred Angus steers (243+/-20.8 kg; 221+/-19.7 days) were allotted to control, fenceline (FL), and nose-clip (NC) weaning groups. Steers were weighed and blood samples were collected on days -7, 0 (pre-transit) and 7 surrounding transport. Leukocytes were analyzed for glutathione peroxidase and glutathione reductase activity, whereas malondialdehyde and Se were measured in plasma. Data were analyzed using PROC MIXED with the Tukey-Kramer adjustment applied post hoc. No treatment effects were detected for blood variables or weights. Glutathione peroxidase activity was not altered by time (P = 0.27). Glutathione reductase activity, Se, and malondialdehyde declined (P<0.001) from day -7 to 7 in all steers. Treatmentxdate interaction was detected for malondialdehyde (P<0.02). Control and FL steers gained weight (P<0.03), whereas NC steers did not gain weight between days -7 and 0 (P = 0.81). All weaning treatment groups gained weight between days 0 and 7 (P<0.05). Results suggest that two-stage weaning has little effect on examined markers of oxidative stress.

The effect of weaning method on coccidial infections in beef calves.

Weaning is often cited as a stressful event that can precipitate clinical coccidiosis in cattle. Recently, two-stage weaning methods have been investigated as a means to reduce stress in calves. The objective of this study was to investigate the effect of weaning method on fecal oocyst count (FOC) and Eimeria spp. composition. A group of 108 beef calves (190-240 days of age) were allocated to three treatments on day -7: a fenceline weaned group where calves could see and hear their dams, but were physically separated from them by a fence (FL), a noseclipped group where suckling was prevented (NC), and a group left with their dams to be traditionally weaned (TW) by abrupt separation on day 0. On day 0, noseclips were removed from the NC calves and all groups were completely separated from their dams. The steers (n=50) were transported 172 km to another farm, and heifers (n=58) were taken to distant fields on the same farm. Rectal fecal samples were collected from all calves on days -7, 0, and 14. Steers were also sampled on days 7, 28, and 42. A group of steers (n=24) from each of the treatments previously described were fitted with pedometers and intensively observed on days 1-4. The Modified McMaster's test and Wisconsin sugar flotation test were used for quantification and identification of Eimeria spp. oocysts. Clinical coccidiosis was not observed during the study. Fecal oocyst counts did not differ between treatment groups on any sampling day. Differences between steer and heifer FOC were not detected. Treatment had no effect on species composition, but time effects were detected in the steers. The mean percentage of E. bovis was lower (P<0.05) on days 28 and 42 than all other sampling days. The decrease in the percentage of E. bovis was accompanied by an increase (P<0.05) in the percentage of E. canadensis on days 28 and 42. Behavioral observation showed that TW steers exhibited higher levels of stress related behavior (P<0.05) following complete separation, although this was not reflected in FOC.

Association of classical semen parameters, sperm DNA fragmentation index, lipid peroxidation and antioxidant enzymatic activity of semen in ram-lambs.

The objective was to determine relationships among classical semen characteristics, sperm chromatin structure assay (SCSA), lipid peroxidation and antioxidant enzymatic activity in ram-lamb semen. Fifty-seven ram-lambs were electroejaculated, and routine semen evaluation was conducted (as part of a breeding soundness evaluation). The percentage of sperm DNA fragmentation index (%DFI) and the percentage of sperm with abnormally high DNA stainability (HDS; immature spermatozoa) were determined by SCSA using the metachromatic properties of acridine orange. Semen was centrifuged at 800 x g for 15 min to separate spermatozoa and seminal plasma and the aliquots were stored at -70 degrees C until analyzed. Lipid peroxidation, superoxide dismutase (SOD), and glutathione peroxidase (GPx) levels in seminal plasma and spermatozoa were measured by spectrophotometric assays. The classical semen parameters were negatively related to lipid peroxidation and GPx activity in spermatozoa; motility and morphology were negatively related to %DFI (P < 0.05). Based on Kruskal-Wallis pair-wise comparison of median values among breeding soundness outcome groups, %DFI was lower in the satisfactory group compared to other groups (P < 0.05) and the lipid peroxidation and GPx activity in seminal plasma and spermatozoa were lower in satisfactory and questionable groups (P < 0.05). However, the SOD was lower in the unsatisfactory group (P < 0.05). In summary, classical semen parameters were negatively related to % DFI, lipid peroxidation and GPx activity in ram-lamb spermatozoa and seminal plasma. There were indications that SOD and GPx have crucial protective roles against the toxic effect of reactive oxygen species (ROS) in ram-lamb semen.

Peroxidative protection of parenteral admixture by D-alpha-tocopherol.

High lipid:low dextrose (HL:LD) parenteral admixtures (PAs) are becoming commonplace in the nutritional support of veterinary patients. Lipid peroxidation before administration appears to be an unwanted sequela of high lipid content in PAs that can lead to oxidative injury of biologic membranes in vivo. The purpose of this in vitro study was to measure hydroperoxides in HL:LD PAs and to determine the optimal dose of d-alpha-tocopherol to minimize peroxidation in these PAs during a 24-hr period. Detectable concentrations of hydroperoxides were present in all PAs. D-alpha-tocopherol appeared to significantly minimize peroxidation of HL:LD PAs in vitro. These results have clinical implications for parenteral feeding in critically ill patients.

Fibrocartilaginous embolic myelopathy in a calf.

A 5-month-old Angus heifer with a history of acute hindlimb paresis that quickly progressed to lateral recumbency was necropsied. Gross lesions included a 6-cm segment of gray to brown discoloration and softening of the right ventrolateral spinal cord between T2 and T3. Microscopically, there was liquefactive necrosis of ventrolateral white and gray matter, and multiple intravascular emboli partially or completely occluded many intralesional and adjacent spinal and meningeal arteries and veins. Emboli were alcian blue positive, consistent with fibrocartilage of the nucleus pulposus of the intervertebral disk. No gross abnormalities were detected in the vertebrae or intervertebral disks. Fibrocartilaginous embolic myelopathy appears to be very rare in cattle; however, it should be considered in cases of acute, nonprogressive spinal cord dysfunction.

Reduced serum insulin-like growth factor (IGF) I is associated with reduced liver IGF-I mRNA and liver growth hormone receptor mRNA in food-deprived cattle.

Nutritional deprivation decreases blood insulin-like growth factor I (IGF-I) concentrations in a variety of species. In this study, we explored the underlying mechanism by determining the effects of food deprivation on the levels of total IGF-I mRNA and total growth hormone receptor (GHR) mRNA, as well as the levels of individual IGF-I mRNA variants and GHR mRNA variants in the liver of steers. Food deprivation for nearly 3 d decreased the levels of serum IGF-I by 63% (P < 0.01), and this decrease was associated with a 75% decrease (P < 0.01) in total IGF-I mRNA in the liver. The food deprivation-induced decrease in liver total IGF-I mRNA was associated with an equivalent decrease in the levels of both class 1 and class 2 IGF-I mRNA. In addition to IGF-I mRNA, food deprivation also decreased the levels of total GHR mRNA in the liver (P < 0.05), and this decrease was associated with a decrease in the liver expression of GHR mRNA variants 1C3 (P < 0.05) and 1A (P = 0.08). Food deprivation did not affect the levels of two other major GHR mRNA variants, 1B and 1C2, in the liver. These results demonstrate that the food deprivation-induced decrease in circulating IGF-I in steers is associated with a coordinate decrease in the expression of different IGF-I mRNA variants and a specific decrease in the expression of GHR mRNA variants 1C3 and 1A in the liver.