Characterization of pregnancy-associated glycoproteins and progesterone as a predictor of twins and conceptus loss in high-risk-pregnancy Holstein cows

The objective of this study was to characterize plasma concentrations of pregnancy-associated glycoprotein (PAG) and progesterone (P4) as predictors of twins and pregnancy loss in Holstein cows with high-risk pregnancies. High-risk pregnancy was characterized using transrectal ultrasonography 37 d after artificial insemination (AI) based on the following criteria: small embryo size <15 mm, n = 10), slow heartbeat (<60 beats per minute, n = 11), and extra-amniotic membrane (additional amniotic membrane, n = 3). A cohort of twins (n = 41) diagnosed at d 37 post-AI was also enrolled. Each high-risk and twin pregnancy cow was paired with a cow of the same parity carrying a normal singleton at d 37 post-AI (control, n = 65). Blood samples were collected to measure PAG and P4 at d 37, 44, and 51 post-AI. Statistical analysis was performed using ANOVA, logistic regression, and receiver operator characteristic (ROC) curve with JMP software (SAS Institute Inc., Cary, NC). Pregnancy loss at d 51 post-AI was greater in high-risk pregnancies than in controls and twins (control = 1.5%; high-risk = 87.5%; twins = 12.2%). Concentration of PAG at d 37 post-AI did not differ among groups (control = 5.3 ± 0.7; high-risk = 4.8 ± 1.2; twins = 4.0 ± 0.9 ng/mL). Concentration of P4 at d 37 post-AI was greater in twins than in high-risk pregnancies and control, and lesser in high-risk pregnancies than in controls (control = 7.0 ± 0.3; high-risk = 5.9 ± 0.4; twins = 8.4 ± 0.3 ng/mL). Regression and ROC analysis for PAG at d 37 post-AI did not find a threshold to predict pregnancy loss or twins. Regression and ROC analysis for P4 at d 37 post-AI found that a threshold of 6.5 ng/mL predicted pregnancy loss with an area under the curve (AUC) of 0.64, and a threshold of 7.2 ng/mL predicted twins with AUC of 0.71. In summary, pregnancy loss and twins were predicted with only moderate accuracy by P4 concentration at d 37 post-AI, and the variability in PAG concentrations at d 37 post-AI was not sufficient to generate a threshold to predict pregnancy loss and twins in Holstein lactating cows.

Judicious use of prophylactic antimicrobials to reduce abdominal surgical site infections in periparturient cows: part 1 - a risk factor review

Surgical site infections (SSI) are an uncommon, but significant, consequence of surgical interventions. There are very few studies investigating SSI risk in veterinary medicine, and even fewer in cattle, despite the fact that major surgeries are commonly conducted on livestock. Furthermore, the suboptimal conditions under which such surgeries are frequently performed on livestock could be considered an important risk factor for the development of SSIs. With increasing public concern over the contribution of veterinary-prescribed antimicrobials to the emergence of antimicrobial-resistant bacteria in people, there is widespread scrutiny and criticism of antimicrobial use in livestock production medicine systems. While the causal link between antimicrobial resistance in livestock and people is heavily debated, it is clear that the prevalence of antimicrobial resistance, in any population, is closely correlated with the antimicrobial 'consumption' within that population. As the veterinary profession explores ways of addressing the emergence and selection of antimicrobial-resistant bacteria in food-producing animals, there is a need for veterinarians and producers to carefully consider all areas of antimicrobial use, and employ an evidence-based approach in designing appropriate clinical protocols. This paper aims to review current knowledge regarding the risk factors related to abdominal SSI in periparturient cows, and to encourage practitioners to judiciously evaluate both their standard operating procedures and their use of antimicrobials in these situations. In a second paper, to be published in a subsequent issue of Veterinary Record, these principles will be used to provide specific evidence-based recommendations for antimicrobial use in bovine abdominal surgery.

Corium tissue expression of genes associated with inflammation, oxidative stress, and keratin formation in relation to lameness in dairy cows

Objectives were to (1) determine the feasibility of performing hoof biopsies without impairing locomotion; (2) evaluate the feasibility of using biopsied tissue for quantitative PCR; and (3) compare relative gene expression among claws for several target genes. Biopsies were performed on 6 Holstein cows, yielding 4 tissue specimens per cow from front leg, right limb, and medial claw (claw position 3); rear leg, left limb, and lateral claw (claw position 5); and rear leg, right limb, medial claw (claw position 7). Cows were monitored for lameness daily for 7 d post-biopsy and then weekly for 8 wk. Histopathological analysis confirmed that tissue collected was from between the stratum corneum and dermis. Biopsied tissue was used for RNA extraction, including evaluation of yield and purity. The profile by claw position of 19 genes with key functions in cell differentiation, proliferation, inflammation, and keratin formation was assessed via quantitative reverse transcription-PCR. Other than transient disturbances in locomotion score in some cows during 2 to 4 d post-biopsy, no signs of pain, locomotion impairment, or clinical lameness were observed post-biopsy. Total RNA yields averaged 259.7±100, 447.8±288, and 496.4±118 μg/mg of tissue for claw positions 3, 5, and 7, respectively. The biopsy procedure was successful for obtaining corium for gene expression. Among 5 keratin proteins analyzed, only keratin 5 was expressed. Transcripts related to inflammation and oxidative stress (STAT3, MYD88, SOD2, and TLR4) were among the more abundant in corium tissue, but expression did not differ between claws. Biotinidase (BTD) expression was greater in claw 3 versus claw 5, whereas the ligand-activated nuclear receptor retinoic acid receptor-α (RXRA) was greater in claws 3 + 5 compared with claw 7. Overall, results from this pilot study revealed modest differences at the transcriptome level, suggesting that biotin availability and lipid metabolism differ between claw positions, whereas inflammation and oxidative stress seem to play an important role across claws. More comprehensive studies of the hoof transcriptome are required to improve our understanding of the mechanisms that link environmental and dietary factors to development of lameness.

Partial replacement of forage with nonforage fiber sources in lactating cow diets. I. Performance and health

Seventy-eight Holsteins were fed for 112 d to evaluate performance and health responses to diets varying in source and concentration of fiber. Three diets based on different carbohydrate feeding strategies were formulated. These diets contained low concentrations of forage and neutral detergent fiber (NDF) (12.6% forage NDF, 19.5% total NDF), adequate NDF and forage (20% forage NDF, 24.8% total NDF), or low forage with additional NDF from cereal byproducts (12.7% forage NDF, 33.4% total NDF). Responses to sodium bicarbonate supplementation (0 or 0.8% of diet DM) were evaluated for each carbohydrate strategy, and bicarbonate improved performance on all diets. Eight cows were used concurrently in a Latin square experiment to evaluate the linearity of milk fat concentration response to increasing concentrations of byproduct NDF in low-forage diets. Considering both trials, cereal byproduct NDF was only 27% as effective as NDF from alfalfa silage in eliciting a milk fat concentration response, which was less than predicted from previous experiments. This difference was not because of the short duration of previous experiments nor because of nonlinearity in the response to byproduct NDF. Low-forage diets fed for 112 d did not result in major health disorders for midlactation cows. However, several indicators suggested that cows fed low-forage, high-NDF diets might be less susceptible to ruminal acidosis than those fed diets containing low forage and low NDF, especially during times of dietary transition. Although the effective fiber value in various feeds is variable and difficult to quantify, the value of byproduct fiber needs to be considered when balancing the carbohydrate fraction of dairy rations.

Diagnostic methods for the detection of subacute ruminal acidosis in dairy cows

Two experiments were conducted 1) to validate a field protocol for the determination of ruminal pH and 2) to develop a strategy to interpret ruminal pH data from groups of cows. In the first experiment, ruminal fluid was collected from 30 lactating dairy cows. Ruminal fluid pH was 0.28 pH units lower for fluid collected by rumenocentesis than for fluid collected through a ruminal cannula. Concentrations of volatile fatty acids were correspondingly higher in samples collected by rumenocentesis. A portable pH meter capable of measuring pH of a very small volume of ruminal fluid yielded very similar pH readings as did a standard meter with a pH probe. Filtration or aspiration of ruminal fluid had no effect on pH. In the second experiment, a strategy was developed to use ruminal pH values from a subsample of cows to distinguish between groups fed either a low or higher forage diet. Groups could be distinguished using a cut point of 5.5 ruminal pH, a sample size of 12 cows, and a critical value of 3 or more cows below the cut point. This strategy had the lowest theoretical error rate for herds with either a high or low prevalence of cows with a low ruminal pH.

Comparison of topical application of three products for treatment of papillomatous digital dermatitis in dairy cattle

OBJECTIVE

To test the effectiveness of 3 topical sprays for treatment of papillomatous digital dermatitis (PDD) in dairy cattle.

DESIGN

Prospective field trial.

ANIMALS

48 lactating cows with PDD randomly assigned to 4 groups of 12 cows each.

PROCEDURE

For 3 weeks, cows in each group were treated topically with oxytetracycline solution (100 mg/ ml), acidified ionized copper solution, acidified sodium chlorite solution, or a placebo (tap water). Cows were milked 3 times daily, and at each milking, lesions were washed with a pressure hose and treatment solutions were sprayed on the lesions. Degree of lameness was graded before and after 3 weeks of treatment.

RESULTS

Mean lameness score decreased (ie, cows were less lame) for all 3 treatment groups, but increased for the control group.

CLINICAL IMPLICATIONS

Daily application of topical solutions was effective in decreasing degree of lameness associated with PDD in cattle tested.