Christine Navarre

Development and in-vitro evaluation of sustained release poloxamer 407 (P407) gel formulations of ceftiofur.

The objective of this study was to develop sustained release Poloxamer 407 (P407) gel formulations of ceftiofur for treating foot infections in cattle. The formulations contained 25-35% (w/v) P407 alone or with polyvinyl pyrrolidone (PVP), carboxy methylcellulose (CMC), or hydroxylpropyl methylcellulose (HPMC) as an additive. The in-vitro release profiles of ceftiofur from the P407 formulations and the gel dissolution profiles were obtained simultaneously. Ceftiofur release followed zero order kinetics and correlated well with the weight percentage of P407 dissolved, indicating that the overall rate of release of ceftiofur is controlled by dissolution of the P407. An increase in P407 content from 25 to 35% resulted in a decrease in the rate of ceftiofur release. However, it appears that other factors may have also affected the drug release rate. Inclusion of PVP, CMC, and HPMC in the gel decreased the rate of release of ceftiofur to some extent. A decrease in the temperatures of the release medium decreased the release rate of ceftiofur, but not the rate of gel dissolution. The pH of the release medium showed a very slight effect on the release of ceftiofur and did not affect gel dissolution due to the non-ionic nature of P407.

Pluronic® F127 gel formulations of deslorelin and GnRH reduce drug degradation and sustain drug release and effect in cattle

The objective of this study was to compare the effectiveness of intramuscular sustained release Pluronic F127 (PF127) gel formulations of deslorelin, a potent GnRH agonist, and GnRH to their solution formulations in inducing the release of luteinizing hormone and formation of luteal tissue in cattle. Injectable gel formulations of deslorelin and GnRH were prepared using Pluronic F127 (25%, w/w), a block copolymer. PF127 gels sustained the in vitro release of deslorelin as well as GnRH at similar rates and reduced drug degradation in muscle tissue when compared to the solution formulations. Deslorelin, as well as GnRH, elicited desirable elevations in plasma LH and progesterone concentrations in vivo. When compared to the solution formulations, the gel formulations of both drugs induced a broader peak of LH. Also, the peak LH levels were lower and the peak times were delayed with the gel formulations compared to the solution formulations. While the solution dosage form of deslorelin and GnRH elicited similar responses, the PF127 gel formulation of deslorelin induced peak LH levels at an earlier time (3 h for deslorelin versus 5.25 h for GnRH). The results indicate that, deslorelin exerts a pharmacological effect in cattle. The LH response to deslorelin as well as GnRH can be altered by controlling the input or the release rate of the drug. PF127 gel formulations can sustain peptide release and reduce peptide degradation.

Influence of pH and Temperature on Kinetics of Ceftiofur Degradation in Aqueous Solutions

The objective of this study was to evaluate the stability of ceftiofur (1mgmL‐1)in aqueous solutions at various pH (1, 3, 5, 7.4 and 10) and temperature (0, 8, 25, 37 and 60°C) conditions. The ionic strength of all these solutions was maintained at 0.5 M. Ceftiofur solutions at pH 5 and 7.4 and in distilled water (pH = 6.8) were tested at all the above temperatures. All other solutions were tested at 60°C. Over a period of 84 h, the stability was evaluated by quantifying ceftiofur and its degradation product, desfuroylceftiofur, in the incubation solutions. HPLC was used to analyse these compounds.

A comparison of surface and rectal temperatures between sheared and non-sheared alpacas (Lama pacos)

The objective of this research was to determine if whole-body shearing would effect gross thermoregulation in alpacas. Eight mature, intact male alpacas were randomly assigned to one of two groups and maintained in outdoor pastures with adequate artificial shade from June through August (summer climate) in east central Alabama, USA. Group one animals (N=4) were sheared to remove all fiber to within 2cm of their skin. Group 2 animals (N=4) were left non-sheared. Sheared alpacas tended to have lower rectal temperatures during high ambient temperatures than did non-sheared alpacas (P=0.06). Thermographic studies of the scrotum revealed cooler surface temperatures in sheared versus non-sheared alpacas (P=0.05). Temperatures in the right medial thigh of sheared animals were 0.9 degrees C cooler than the thigh region of non-sheared animals in the morning (P<0.03). Right medial thigh temperatures were 1.6 degrees C cooler in sheared alpacas in the afternoon (P<0.01). Significant positive correlations were found in non-sheared animals between ambient temperature and rectal temperature in the morning (r=0.612, P=0.014). In sheared animals during the morning significant positive correlations were established between the Heat Stress Index (HSI) and the right medial thigh surface temperatures (r=0.648, P=0.003), the HSI and rectal temperature (r=0.729, P=0.0003), the ambient temperature and right medial thigh surface temperature (r=0.485, P=0.04), and the ambient temperature and the rectal temperature (r=0.823, P<0.0001). In the afternoon a significant positive correlation was found in the sheared alpacas between the HSI and the right medial thigh surface temperature, rectal temperature and surface scrotal temperature (r=0.538, P=0.02, r=0.543, P=0.019 and r=0.522, P=0.045), respectively. These data indicate that whole-body shearing of alpacas could have a beneficial effect on thermoregulation when used as a preventative measure against heat stress. Shearing may assist heat dissipation resulting in a cooler surface body temperature and rectal temperature in alpacas when challenged by the heat and humidity experienced in the summer months in the southeastern United States.

Differentiation of Gastrointestinal Diseases in Adult Cattle

An understanding of diagnostic tests and procedures for gastrointestinal diseases of adult cattle assists the practitioner in differentiating the more common gastrointestinal disturbances. A systematic approach to differentiating these conditions is used, targeting abdominal distention, anterior abdominal pain, and diarrhea.

A comparison of physical examination and clinicopathologic parameters between sheared and nonsheared alpacas (Lama pacos)

The purpose of this study was to determine the physiological changes associated with chronic heat stress in sheared versus nonsheared alpacas. Fourteen intact male adult alpacas were randomly assigned to one of the two groups: Group S alpacas were sheared to within 2cm of their skin; Group NS alpacas were not sheared. These animals were maintained from June through August in east central Alabama. Data collected in the morning, every two weeks, included vital signs, body weight, body condition score, complete blood counts, serum chemistries and electrolytes, whole blood selenium, and plasma cortisol. S and NS groups were contrasted using the repeated measures analysis of variance, and pertinent correlations with weather parameters were calculated. Clinical heat stress was not evident in any animals during the study. Significant differences between treatment groups were seen in rectal temperature (P=0.0095), sodium concentration (P=0.0219), and blood urea nitrogen (BUN) (P=0.0189). The mean rectal temperature of the NS group was above the normal range on five sampling times compared to only once for the S group. However, mean sodium and serum urea nitrogen levels were within normal limits in both groups at all sampling times. Rectal temperature of only the S group was positively correlated to weather parameters. Sodium of both S and NS groups and BUN of the NS group were negatively correlated with weather parameters. This study indicates that there are differences between sheared and nonsheared alpacas in physical examination and clinicopathologic parameters that can be correlated with changes in ambient conditions. These differences suggest that nonsheared alpacas are less heat tolerant than sheared alpacas. Therefore, shearing is recommended for animals exposed to similar conditions.

Differentiation of Gastrointestinal Diseases of Calves

Bovine practitioners are commonly faced with gastrointestinal problems in calves. Being able to diagnose gastrointestinal problems properly is pivotal in developing proper preventive and treatment strategies. This article discusses the common gastrointestinal diseases, including diarrhea of calves, with the focus on antemortem diagnosis and differentiation of these diseases.

Salivary Gland Thrombostasin Isoforms Differentially Regulate Blood Uptake of Horn Flies Fed on Control- and Thrombostasin-Vaccinated Cattle

ABSTRACT Thrombostasin (TS) is an anticlotting protein found in saliva of Haematobia irritons (horn flies). The polymorphic nature of the ts gene was first associated with success of horn flies blood feeding on a laboratory host, New Zealand White rabbits. In this study, we report results of similar studies testing blood uptake of horn flies feeding on a natural host, cattle. These studies confirmed the association of ts genotype with blood uptake of horn flies and showed that it was host species specific. In contrast to rabbits, blood uptake volumes of homozygous ts10 horn flies were lower than those of other ts genotypes when fed on control (ovalbumin-vaccinated) cattle. Cattle vaccinated with recombinant protein isoforms, rTS9 or rTB8, resisted horn fly feeding by yielding lower blood volumes compared with flies feeding on control cattle. The specific impact of vaccination, however, varied by ts genotype of flies, Cattle vaccinated with isoform rTS9 resisted flies of ts2, ts9, and tb8 genotype. Vaccination with isoform rTB8 produced resistance to ts8, ts9, and tb8 genotype flies. Horn flies of genotype ts10 were not affected by vaccination with either TS isoform and fed as well on rTS9- and rTB8-vaccinated as on control-vaccinated cattle. These experimental results confirm the efficacy of vaccines targeting horn fly salivary proteins and provide new insight into the dynamics of horn fly-cattle interactions in nature.

Fluid Therapy in Small Ruminants and Camelids

Body water, electrolytes, and acid-base balance are important considerations in the evaluation and treatment of small ruminants and camelids with any disease process, with restoration of these a priority as adjunctive therapy. The goals of fluid therapy should be to maintain cardiac output and tissue perfusion, and to correct acid-base and electrolyte abnormalities. Hypoglycemia, hyperkalemia, and acidosis are the most life-threatening abnormalities, and require most immediate correction.

Salivary Gland Thrombostasin Isoforms Differentially Regulate Blood Uptake of Horn Flies Fed on New Zealand White Rabbits

ABSTRACT Thrombostasin (TS) is a previously characterized anticlotting protein with multiple isoforms found in the saliva of horn flies. In this report, the effect of TS isoforms on blood feeding was assessed using individual flies that carried corresponding ts allelles. Laboratory studies of horn fly blood feeding were conducted using colony-reared flies fed on New Zealand White (NZW) rabbits. After timed 20-min feeding periods, each fly was characterized for gender, blood volume uptake, and ts genotype. The results showed that mean blood volumes obtained by individual flies were not related to fly gender but were correlated to the ts genotype(s) carried by each fly. A fly having one or both fe alleles coding for the TS9 isoform took less blood than those possessing one or both fe alleles coding for the TS10 isoform. These results confirm the significant role that TS plays in horn fly feeding and highlight the differential impact of TS protein isoforms that vary by as few as three amino acids.