Evaluation of gonadotropin-releasing hormone hydrogen chloride at 3 doses with prostaglandin F2α for fixed-time artificial insemination in dairy cows.

The objectives of the current study were to evaluate the efficacy and field safety of GnRH HCl administered at 3 doses in fixed-time artificial insemination (FTAI) programs (Ovsynch) in dairy cows. A common protocol was conducted at 6 commercial dairies. Between 188 and 195 cows were enrolled at each site (total enrolled = 1,142). Cows had body condition scores ≥ 2 and ≤ 4, were between 32 to 140 d in milk, and were clinically healthy. Within pen and enrollment day (enrollment cohort), cows were assigned randomly in blocks of 4 to each of 4 treatments: (1) 25mg of PGF2α on d 7 with FTAI 72 ± 2 h later (control); (2) 100 µg of GnRH on d 0, d 7 a dose of 25mg of PGF2α, and the second administration of 100 µg of GnRH (T100) administered either at 48 ± 2 h (d 9) after PGF2α with FTAI 24 ± 2 h later or 56 ± 2 h (d 9) after PGF2α and FTAI 17 ± 2 h later; (3) same as T100 with both injections of 150 µg of GnRH (T150); and (4) same as T100 with both injections of 200 µg of GnRH (T200). Three sites selected the first option and 3 sites selected the second option for the timing of the second injection of all doses of GnRH. Cows were observed daily for signs of estrus and adverse clinical signs. Cows not returning to estrus had pregnancy diagnosis between 42 and 65 d following FTAI. Pregnancies per FTAI (P/FTAI) were analyzed as a binary variable (1 = pregnant, 0 = not pregnant) using a generalized linear mixed model with a binomial error distribution and a logit link function. The statistical model included fixed effects for treatment, random effects of site, site by treatment, enrollment cohort within site, and residual. Parity (first vs. second or greater) was included as a covariate. For demonstration of effectiveness, α=0.05 and a 2-tailed test were used. Fifty-two cows were removed from the study because of either deviation from the protocol, injury, illness, culling, or death. Among the remaining 1,090 cows, 33.9% were primiparous and 66.1% were multiparous. Back-transformed least squares means for P/FTAI were 17.1, 27.3, 29.1, and 32.2% for control, T100, T150 and T200, respectively. The P/FTAI for each GnRH dose differed from that of the control. No differences were detected in P/FTAI between GnRH doses. No treatment-related adverse events were observed. Mastitis was the most frequently observed adverse clinical sign, followed by lameness and pneumonia. This study documents the efficacy and safety of doses of 100 to 200 µg of GnRH as the HCl salt when used in Ovsynch programs.

Pharmacokinetics of ceftiofur crystalline-free acid sterile suspension in the equine.

Absolute bioavailability and dose proportionality studies were performed with ceftiofur in horses. In the absolute bioavailability study, thirty animals received either an intravenous dose of ceftiofur sodium at 1.0 mg/kg or an intramuscular (i.m.) dose of ceftiofur crystalline-free acid (CCFA) at 6.6 mg/kg. In the dose proportionality study, 48 animals received daily i.m. ceftiofur sodium injections at 1.0 mg/kg for ten doses or two doses of CCFA separated by 96 h, with CCFA doses of 3.3, 6.6, or 13.2 mg/kg. Noncompartmental and mixed-effect modeling procedures were used to assess pharmacokinetics (PK). CCFA was well absorbed with a bioavailability of 100%. AUC(0-∞) and C(max) increased in a dose-related manner following administration of the two doses of CCFA at 3.3, 6.6, and 13.2 mg/kg. The least-squares mean terminal half-life (t(½) ) following the tenth daily i.m. injection of ceftiofur sodium at 2.2 mg/kg was 40.8 h, but the least-squares mean t(½) following the second i.m. injection of CCFA at 6.6 mg/kg was 100 h. The time that plasma ceftiofur equivalent concentrations remain above a threshold concentration of 0.2 µg/mL has been associated with efficacy, and following administration of two 6.6 mg/kg doses of CCFA, the mean time above 0.2 µg/mL was 262 h. Simulations with the nonlinear mixed-effect PK model predicted that more than 97.5% of horses will have plasma ceftiofur equivalent concentrations >0.2 µg/mL for 96 h after the second 6.6 mg/kg dose of CCFA.

Efficacy of intramammary infusion of ceftiofur hydrochloride at drying off for treatment and prevention of bovine mastitis during the nonlactating period.

This study evaluated the efficacy of intramammary infusion of ceftiofur hydrochloride for the treatment of intramammary infections present at the last milking of lactation and for prevention of new intramammary infections during the nonlactating period. Cows were randomly assigned to five treatments (untreated negative control, 125, 250, and 500 mg of ceftiofur, and a positive control group receiving 300 mg cephapirin benzathine). A dose of 125 mg of ceftiofur per mammary quarter was effective for treatment of existing infections present at the time of milk cessation, but only the 500-mg dose of ceftiofur per mammary quarter was effective for both treatment of existing intramammary infections at the time of milk cessation and for prevention of new intramammary infections during the nonlactating period.

Influence of prepartum pirlimycin hydrochloride or penicillin-novobiocin therapy on mastitis in heifers during early lactation.

A study was conducted in 2 dairy research herds to determine whether prepartum therapy of heifer mammary glands with penicillin-novobiocin or pirlimycin hydrochloride was effective for reducing the percentage of heifers and mammary quarters infected with mastitis pathogens during early lactation. Almost 96% of Jersey heifers (67 of 70) and 71.3% of quarters (199 of 279) were infected 14 d before expected calving. Of the quarters infected at 14 d before expected parturition, 75% (54 of 72) were uninfected following treatment with penicillin-novobiocin; 87% (61 of 70) were uninfected following treatment with pirlimycin, and 56% (32 of 57) were uninfected in the untreated negative control group. The majority of intramammary infections in Jersey heifers were due to coagulase-negative staphylococci (61%), Streptococcus species, primarily Streptococcus uberis (19%), and Staphylococcus aureus (8%). Almost 73% of Holstein heifers (40 of 55) and 34.3% of mammary quarters (73 of 213) were infected 14 d before expected calving. Of the quarters infected at 14 d before expected parturition, 76% (19 of 25) were uninfected following treatment with penicillin-novobiocin; 59% (17 of 29) were uninfected following treatment with pirlimycin, and 26% (5 of 19) were uninfected in the untreated negative control group. The majority of intramammary infections in Holstein heifers were due to coagulase-negative staphylococci (44%) and Staph. aureus (30%). In both herds, the bacteriological cure rate was significantly higher in heifer mammary glands treated with penicillin-novobiocin or pirlimycin hydrochloride than in untreated controls. Prepartum therapy of heifer mammary glands with penicillin-novobiocin or pirlimycin hydrochloride significantly reduced the percentage of heifers and quarters infected with mastitis pathogens during early lactation.

Survey of intramammary infections in dairy heifers at breeding age and first parturition.

A survey was conducted to determine and contrast prevalence of IMI in nulligravid and primigravid dairy heifers pre- and postpartum. Contrasts were made to evaluate the risk factors of location of dairy, trimester of gestation, and season of sampling on IMI. Twenty-eight dairies in California, Louisiana, Vermont, and Washington were studied. Lacteal secretions were collected aseptically from heifers at breeding age (8 to 19 mo) from one side of the gland and again at 4 d postpartum from all quarters. Of the quarters sampled, 65.6% prepartum and 64.0% postpartum were free of IMI. The percentages of quarters with IMI from coagulase-negative staphylococci or Staphylococcus aureus IMI were 27.1 and 9% prepartum and 21.8 and 2.9% postpartum. Staphylococcus aureus IMI were most prevalent in Louisiana during the months other than summer. Location, herd, and season significantly influenced prevalence of IMI. The prevalence of IMI was greatest during the last trimester of pregnancy, ranging from 49.2% in the winter to 36.8% in the summer. The significant effects of herd location and season suggest that management variables influence prevalence of heifer IMI. Because prevalence of IMI was greatest during the last trimester of pregnancy compared with prevalence during earlier stages of pregnancy, the heifer may be most susceptible to this disease during this period of first gestation.

The visual appearance and somatic cell count of mammary secretions collected from primigravid heifers during gestation and early postpartum.

Mammary secretions, obtained before and after calving, were examined for visual appearance, SCC, and bacteriology as part of a larger study determining the prevalence of IMI in 1588 primigravid heifers. Appearance of secretions was categorized into five groups: thin and watery, honey-like, serumy, milky, or thickened colostrum. Precalving secretions were further characterized as low viscosity (thin and watery, serumy, or milky) or high viscosity (honey-like and thickened colostrum). Postcalving secretions were further characterized as normal (milky, thickened colostrum) or abnormal (thin and watery, serumy, or honey-like). Infected precalving quarters (81%) had low viscosity secretions. Quarters that were uninfected precalving (75%) had high viscosity secretions. Greater than 90% of all postcalving milk samples appeared to be normal, regardless of geographic location, season, or bacterial infection status. Only 77% of the samples from quarters infected with contagious and noncontagious mastitis pathogens had normal appearance. Precalving SCC from bacteriologically negative quarters were lower than SCC from infected quarters. Similarly, postcalving SCC were lower from the bacteriologically negative quarters than from the infected quarters. Infected quarters had higher mean SCC than the uninfected quarters during both pre- and postcalving periods.

Profitable dispensing.

The dairy practitioner is the best source of information on medication that the dairyman has. The same practitioner should also be the best source of the actual product. Some organization and effort can make the difference between a small profit and a large one derived from this part of the practice.

Neural catecholamine deficiencies in the porcine stress syndrome.

A study was conducted to compare catecholamine concentrations in nervous tissues of stress-susceptible (SS) and stress-resistant (SR) pigs that were physically stressed. Ten pigs were included in each group on the basis of results of halothane screening tests, blood typing analysis, and examination for serum creatine kinase (CK) activities at 6 weeks of age. The nervous tissues analyzed included the substantia nigra (SN) and the caudate nucleus (CN) which were taken from pigs as soon as possible after death and frozen in liquid nitrogen. Tissues were radioenzymatically assayed for dopamine, norepinephrine, and epinephrine concentrations. The SS pigs exhibited significantly greater (P less than 0.001) CK activity concentrations than did those SR pigs before and after physical stress. Concentrations of dopamine, norepinephrine, and epinephrine in the CN of SS pigs were significantly lower (P less than 0.05) than those in the CN of SR pigs. Similarly, the SN of SS pigs had lower dopamine, norepinephrine, and epinephrine concentrations than did the SN of SR pigs. The catecholamine deficiencies observed in the porcine stress syndrome seem to have similarities with certain human extrapyramidal diseases.

Urinary and caudate nuclei catecholamine levels in stress-susceptible and normal swine.

Eight stress-susceptible and eight normal pigs were used in the first portion of the study. Urine samples were collected for 24 hr over 4 consecutive days while the pigs were kept in metabolism cages. Each 24-hr sample was assayed for epinephrine, norepinephrine and dopamine. Urinary levels of dopamine were lower (P < .01) in the stress-susceptible pigs. No significant differences in urinary epinephrine or norepinephrine were observed. The second portion of the study evaluated the catecholamines in the caudate nucleus of the brain. Six stress-susceptible and six control pigs were examined. Immediately after exsanguination, caudate nuclei were excised and frozen in liquid nitrogen. The caudate nuclei were assayed for catecholamines within 2 to 3 days of freezing. Caudate nuclei dopamine levels were lower (P < .01) in stress-susceptible pigs (5,961 ng/g) than in control pigs (10,878 ng/g). No significant differences in norepinephrine levels of the caudate nuclei were observed between the two groups.