Ocular distribution and toxicity of intravitreal injection of triamcinolone acetonide in normal equine eyes

Objective  To determine ocular distribution and toxicity of a single injection of intravitreal triamcinolone acetonide (TA) in normal horses.
Animals studied  Six adult horses, donated to North Carolina State University.
Procedures  Six horses were injected intravitreally with either 10, 20, or 40 mg ( n  = 2 each) of TA. The opposite eye of each horse was injected with balanced salt solution (BSS). Ocular toxicity was assessed by biomicroscopy, tonometry, indirect ophthalmoscopy, and electroretinogram. Aqueous humor (AH), vitreous humor (VH), and plasma samples were collected. Horses were euthanized 7 or 21 days after injection and eyes enucleated for histopathology. TA concentrations in AH, VH, and plasma were measured by HPLC.
Results  Three control eyes and one TA eye developed inflammation after injection or collection of AH. Positive bacterial cultures ( Corynebacterium spp., Staphylococcus spp., and Streptococcus spp.) were obtained from three of these eyes. Other than transient corneal edema in TA injected eyes, which resolved by 7 days after injection, no other changes were observed. TA crystals were visible within the vitreous body. No evidence of TA toxic effect was noted on histopathology. TA was detected in all AH and VH samples from treated eyes following injection. Drug was not detected in the plasma.
Conclusions  There was no evidence of overt toxicity from intravitreal TA in normal horses and a single intravitreal injection resulted in TA ocular levels for 21 days. However, the risk for bacterial infections with intravitreal injection or anterior chamber aspirations in horses is high. Use of topical and systemic antibiotics after injection is recommended.     

Monthly model for genetic evaluation of laying hens. II. Random regression

1. We investigated the use of monthly production records for genetic evaluation of laying hens, derived from a test day model with random regression in dairy cattle and compared it with other models. 2. Records of 6450 hens, daughters of 180 sires and 1335 dams, were analysed using a model with restricted maximum likelihood (REML): traits considered were monthly and cumulative egg production. Five models were studied: (1) random regression with covariates derived from the regression of Ali and Schaeffer (Canadian Journal of Animal Science, 67: 637-644, 1987) (RRMAS), (2) random regression with covariates derived from quartic polynomial (RRMP4), (3) fixed regression with covariates derived from Ali and Schaeffer (FRM), (4) multiple trait (MTM) and (5) cumulative (CM). 3. The models were compared on the basis of Spearman rank correlations of individual breeding values and sire breeding values estimated from subsets of full-sib split data. The hens (about 10% per generation) which ranked highest on their estimated breeding values from different models were compared phenotypically with their full records. 4. The estimates of heritability resulting from RRMP4 were biased upward from the estimates obtained from MTM, so this model was discarded. The heritabilities for monthly productions from RRMAS and MTM showed a similar pattern. They were high for the 1st month of production, decreased to their lowest value at about month 5 of production and increased again to the end of lay. 5. Spearman rank correlations between animal breeding values estimated by monthly models (RRMAS, FRM and MTM) were high, between 0.91 and 0.98, whereas those between estimates of monthly models and CM were lower, from 0.85 to 0.87. The correlations estimated either from intermittent months of measurements (odd vs even months) or full records were generally high, from 0.93 to 0.99. Information from odd months of production could be sufficient for cost-efficient recording schemes. The RRMAS generally had the highest correlation of sire breeding values between subsets of full-sib records, followed by MTM, RM and CM. Monthly models selected hens with higher productivity than the cumulative model. 6. In conclusion, genetic evaluation based on monthly production may be better than using cumulative production and RRMAS appeared to be the best among the models tested here.     

Determination of the digestible energy intake and apparent absorption of macroelements in pasture-fed lactating Thoroughbred mares

AIM: To measure the nutritive value of pasture in terms of digestible energy (DE) intake (DEI) and dry matter (DM) digestibility, and to determine the apparent absorption of macroelements in lactating Thoroughbred mares grazed on pasture. METHODS: DM intake (DMI) and DEI were determined from daily faecal DM output measured in grazing mares, divided by the DM indigestible fraction (1-digestible DM), measured in a digestibility trial using pasture-fed mares. Eight lactating mares and their foals, that had a mean age of 40 days, were grazed separately on 50x100 m areas of pasture and daily faecal DM outputs were recorded for 8 days. Five mares and their foals were then placed in individual bare 20x20 m corrals containing custom-made feeding stations for 14 days to determine the indigestible DM fraction. DM, gross energy content, crude protein (CP), soluble carbohydrate, acid detergent fibre (ADF), neutral detergent fibre (NDF), lipid, and macroelement composition of the pasture offered and faeces were determined and their digestibility and/or apparent absorption calculated. RESULTS: DM digestibility of the pasture was 0.6 and the DMI and DEI of a grazing 560 kg mare in early lactation nursing a foal growing at 1.34 kg/day was 13.6 (SE 0.8) kg/day and 146.9 (SE 8.4) MJ DE/day, respectively. Apparent absorptions of the macroelements measured were: Ca 0.75, P 0.43, Mg 0.63, Na 0.78, and K 0.72. CONCLUSIONS: Good quality ryegrass-white clover pasture that had a DE content of 10.8 MJ/kg DM, and a macroelement composition (g/kg) of Ca 3.33, P 3.0, Mg 1.67, Na 1.67, and K 24.2, will provide adequate DMI, DEI, and macroelement intake to lactating Thoroughbred mares.     

Evaluation of PCR to detect Theileria parva in field-collected tick and bovine samples in Tanzania

The ability of PCR to detect infections of Theileria parva, the cause of East Coast Fever, in field-collected tick and bovine samples from Tanzania was evaluated. PCR-detected infection prevalence was high (15/20, 75%) in unfed adult Rhipicephalus appendiculatus ticks that fed as nymphs on an acutely-infected calf, but low (22/836, 2.6%) in unfed adult R. appendiculatus collected from field sites in Tanzania. Tick infection prevalence was comparable to that in previous studies that used salivary gland staining to detect T. parva infection in field-collected host-seeking ticks. Of 282 naturally-exposed zebu calves, seven had PCR-positive buffy coat samples prior to detection of Theileria spp. parasites in stained buffy coat cells or lymph node biopsies. Evidence of Theileria spp. infections was detected in stained smears of lymph node biopsies from 109 calves (38.6%) and buffy coat samples from 81 (28.7%), while buffy coat samples from 66 (23.4%) were PCR-positive for T. parva. Implications of these findings for the sensitivity and specificity of the PCR are discussed.     

Detection of genomic DNA of the crayfish plague fungus Aphanomyces astaci (Oomycete) in clinical samples by PCR

A diagnostic procedure, based on a polymerase chain reaction method (PCR) was developed to detect infection of crayfish with the Oomycete Aphanomyces astaci. A set of oligonucleotide primers was designed to specifically amplify A. astaci DNA in the ITS region surrounding the 5.8S rDNA gene. The PCR amplifies a 115 bp amplicon. The specificity of the primers was demonstrated by testing on 27 A. astaci strains and against 20 non-A. astaci Oomycetes and 5 fungal species. Most of the non-A. astaci Oomycete or fungal species included in the study are either known parasites of freshwater crayfish cuticle or can be found in their natural environment. Specificity was also tested against crayfish tissue and some known parasites and bacteria infecting crayfish.

A protocol for the extraction of A. astaci DNA from infected crayfish tissue was developed. The optimised method allows the detection of two genome equivalents of purified A. astaci genomic DNA.

The method was tested on noble crayfish (Astacus astacus), artificially infected with A. astaci. Detection of A. astaci was possible at the very first time of sampling, which was 2 days after the beginning of spore exposure.     

A mechanistic model for predicting the nutrient requirements and feed biological values for sheep

The Cornell Net Carbohydrate and Protein System (CNCPS), a mechanistic model that predicts nutrient requirements and biological values of feeds for cattle, was modified for use with sheep. Published equations were added for predicting the energy and protein requirements of sheep, with a special emphasis on dairy sheep, whose specific needs are not considered by most sheep-feeding systems. The CNCPS for cattle equations that are used to predict the supply of nutrients from each feed were modified to include new solid and liquid ruminal passage rates for sheep, and revised equations were inserted to predict metabolic fecal N. Equations were added to predict fluxes in body energy and protein reserves from BW and condition score. When evaluated with data from seven published studies (19 treatments), for which the CNCPS for sheep predicted positive ruminal N balance, the CNCPS for sheep predicted OM digestibility, which is used to predict feed ME values, with no mean bias (1.1 g/100 g of OM; P > 0.10) and a low root mean squared prediction error (RMSPE; 3.6 g/100 g of OM). Crude protein digestibility, which is used to predict N excretion, was evaluated with eight published studies (23 treatments). The model predicted CP digestibility with no mean bias (-1.9 g/100 g of CP; P > 0.10) but with a large RMSPE (7.2 g/100 g of CP). Evaluation with a data set of published studies in which the CNCPS for sheep predicted negative ruminal N balance indicated that the model tended to underpredict OM digestibility (mean bias of -3.3 g/100 g of OM, P > 0.10; RMSPE = 6.5 g/100 g of OM; n = 12) and to overpredict CP digestibility (mean bias of 2.7 g/100 g of CP, P > 0.10; RMSPE = 12.8 g/100 g of CP; n = 7). The ability of the CNCPS for sheep to predict gains and losses in shrunk BW was evaluated using data from six studies with adult sheep (13 treatments with lactating ewes and 16 with dry ewes). It accurately predicted variations in shrunk BW when diets had positive N balance (mean bias of 5.8 g/d; P > 0.10; RMSPE of 30.0 g/d; n = 15), whereas it markedly overpredicted the variations in shrunk BW when ruminal balance was negative (mean bias of 53.4 g/d, P < 0.05; RMSPE = 84.1 g/d; n = 14). These evaluations indicated that the Cornell Net Carbohydrate and Protein System for Sheep can be used to predict energy and protein requirements, feed biological values, and BW gains and losses in adult sheep.     

Effect of long- or short-term feeding of alpha-tocopheryl acetate to Holstein and crossbred beef steers on performance, carcass characteristics, and beef color stability.

Three experiments were conducted to examine the effects of vitamin E supplementation on feedlot cattle. Vitamin E supplementation did not affect feedlot performance or carcass characteristics of cattle fed a high-concentrate diet (P greater than .1). The major finding was the effectiveness of vitamin E in extending the color stability of displayed beef (P less than .01). Color stability during display of longissimus lumborum steaks from cattle supplemented with 300 IU/d for 266 d, 1,140 IU/d for 67 d, or 1,200 IU/d for 38 d was extended by 2.5 to 4.8 d. Gluteus medius steaks had an extended color display life of 1.6 to 3.8 d. The accumulation of lipid oxidation products, but not aerobic microbes, associated with displayed longissimus lumborum was suppressed for muscle from vitamin E-supplemented steers. Taste panelists detected no difference among longissimus lumborum steaks from control and vitamin E-supplemented steers but found (P less than .01) steaks aged for 21 d to be more tender than steaks aged for 7 d. Supplementing cattle with vitamin E should reduce economic losses associated with discolored beef during retail display.     

Infectious dermatitis in a ball python (Python regius) colony.

Seven wild-caught ball pythons (Python regius), including six gravid females and one male, were obtained from Africa and were housed in a government animal facility in Research Triangle Park, North Carolina. Upon arrival, the snakes were found to be infested with ticks (Aponomma latus), which were manually removed. Four weeks following arrival, vesicular skin lesions began to appear on the snakes. Despite treatment of all affected female snakes with amikacin (5 mg/kg i.m., every 3 days) and cefotaxime (25 mg/kg i.m., every 3 days), the condition progressed and five of the female snakes died 7 wk after arrival. The remaining male and one female improved after an increase in environmental temperature, with ecdysis followed by healing. Physiologic stress, ectoparasites, and shipping may have predisposed the snakes to sepsis.