Economic modeling of the use of gonadotropin-releasing hormone at insemination to improve fertility in dairy cows

Economic and sensitivity analysis methods were used to evaluate financial returns from use of gonadotropin-releasing hormone (GnRH) at the time of insemination to enhance fertility of dairy cows. A computer spread sheet was used to determine the best service(s) for GnRH treatment, the increase in conception rate required for economic benefit from treatment, and how profits from GnRH treatment are affected by drug cost, herd reproductive efficiency, and production costs. Financial returns increased from use of GnRH at insemination under most herd conditions. Herds with conception rates less than or equal to 45% benefited from GnRH treatment at any 1 or 2 inseminations. Herds with conception rates greater than or equal to 60% benefited from GnRH treatment only at second or later services. Selection of second and/or third insemination as the GnRH treatment service usually resulted in the greatest total return. The enhancement of fertility necessary to achieve the break-even point with GnRH treatment at third service was 2% for low- and 5% for high-conception-rate herds. Base-line herd conception rates, estrus detection efficiency, replacement costs, value of excess days not pregnant, and cost of treatment had the greatest effect on returns from treatment. Herds with high conception rates and low replacement costs were likely to realize the least benefit from GnRH treatment at insemination. On the basis of our findings, we concluded that GnRH treatment at insemination is a profitable procedure under most herd conditions. Optimal treatment regimens for specific herds may best be determined by using herd performance and management data for calculating returns.     

Observations following intravenous xylazine administration in steers

Xylazine was used on 84 occasions to anaesthetise 34 steers, (17 Herefords and 17 Friesians) between 10 and 24 months of age with bodyweights ranging from 209 to 563 kg. Xylazine as a 2 per cent solution was injected intravenously; the mean dose for the Hereford steers was 0.228 mg/kg and for the Friesian steers 0.274 mg/kg. On 21 occasions xylazine only was used. On the other occasions the xylazine was supplemented with local or regional analgesia. The Hereford steers became recumbent after injection of xylazine more readily than the Friesian steers and took longer to recover. In addition the Hereford steers showed fewer reactions to surgical stimulation than the Friesians. It is concluded that xylazine should be supplemented with some form of effective analgesia whenever a surgical operation is performed.     

Use of tilmicosin in a severe outbreak of respiratory disease in weaned beef calves

Severe respiratory disease, associated with seroconversion to bovine respiratory syncitial virus (BRSV), caused the death of two cattle and necessitated antibiotic treatment of 70 calves (rectal temperature of 39.6°C or greater) from a group of 96 (73%) during an 8-day period. Tilmicosin injection resulted in a reduction in median rectal temperature from 40.3°C to 39.2°C and 39.0°C for the first and second days after treatment. The rectal temperature was 39.5°C or lower in 72% (48 of 67) and 96% (64 of 67) of cattle 1 and 2 days after tilmicosin treatment, respectively. Ten cattle were re-treated with tilmicosin 6 to 16 days after the first treatment. Our study demonstrated that bovine respiratory syncytial virus infection could cause severe respiratory disease in a beef herd that had no previous history of BRSV-related disease. Secondary bacterial invasion after BRSV infection was controlled effectively by tilmicosin treatment but repeat antibiotic treatments were occasionally necessary due to bacterial re-infection of the respiratory tract.     

Survey of desert bighorn sheep in California for exposure to selected infectious diseases

From February 1983 to June 1985, 188 desert bighorn sheep (Ovis canadensis nelsoni, = 161 and Oc cremnobates, = 27) from 18 herds in 17 mountain ranges and one captive herd were caught, marked, and had blood, fecal, and nasal mucus samples collected. Nasal swab specimens were cultured bacteriologically and virologically specifically for parainfluenza-3 (PI-3) virus. Bacterial flora differed from herd to herd. Pathogenic pneumophilic bacteria (eg, Pasteurella sp) seldom were found. Parainfluenza-3 virus was isolated from 6 bighorn sheep in 3 herds. Fecal specimens were examined for parasite ova and low numbers of lungworm (Protostrongylus sp) larvae were found in feces from 2 herds. Sera were evaluated for antibodies against respiratory syncytial virus, ovine progressive pneumonia, infectious bovine rhinotracheitis, PI-3, bovine viral diarrhea, brucellosis, leptospirosis, contagious ecthyma, bluetongue, and epizootic hemorrhagic disease. Blood clots were cultured virologically for bluetongue and epizootic hemorrhagic disease. Serologic evidence of bluetongue and/or epizootic hemorrhagic disease was found in 9 herds, and bluetongue virus (serotypes 10,11,13 and 17) was isolated from 3 herds. Antibody titers against PI-3 and respiratory syncytial virus were found in 9 and 13 herds, respectively. Evidence of bovine viral diarrhea infection was found in 6 herds, whereas infectious bovine rhinotracheitis was found in only 1 herd. Antibody titers against contagious ecthyma were found in 9 of 18 herds in California, and active lesions were seen occasionally. Evidence of ovine progressive pneumonia, leptospirosis, or brucellosis was not found.     

Relation among body condition score, milk production, and serum urea nitrogen and cholesterol concentrations in high-producing Holstein dairy cows in early lactation.

Body condition scoring (using a 5-point scale with quarter-point divisions) was performed on 66 Holstein dairy cows that began their second or later lactation in August, September, or October 1988. Body condition was scored, beginning on postpartum day 4(+/- 1) and subsequently at postpartum days (+/- 1) 18, 32, 46, 60, 73, and 87. Blood samples were obtained on the same dates. Kilograms of milk produced per cow was measured daily. Body condition score and changes in body condition score were evaluated in relation to daily milk production, cumulative 80-day milk yield, and serum urea nitrogen and cholesterol concentrations. Average daily milk production during week 1 was indicative of cumulative 80-day production, but not of 305-day milk yields. Cows that calved with body condition score greater than or equal to 3.50 did not differ in average daily milk production, cumulative 80-day milk yield, or 305-day milk yield, compared with cows that calved with body condition score less than 3.50. Cows that calved with body condition score greater than or equal to 3.50 lost more condition than did cows that calved with body condition score less than 3.50. Body condition score at calving and amount of body condition loss interacted with the rate of change in daily milk production. Serum urea nitrogen concentration did not differ for cows grouped by cumulative 80-day milk production or for cows grouped by amount of condition loss. Serum cholesterol values were higher than previously reported values and increased directly with milk production. Serum cholesterol values were inversely related to condition loss but changes in cholesterol concentration were not related to condition loss.     

Leaching of dissolved organic carbon and nitrogen under cotton farming systems in a Vertisol

Leaching with deep drainage is one of the loss pathways of carbon (C) and nitrogen (N) in cropping fields. However, field studies in irrigated row cropping systems are sparse. A 3‐year investigation on C and N leaching associated with deep drainage was overlaid on a long‐term experiment on tillage practices and crop rotations in Australia. The treatments included cotton (Gossypium hirsutum L.) monoculture and cotton–wheat (Triticum aestivum L.) or maize (Zea maize L.) rotations with maximum or minimum tillage. The deep drainage C and N concentrations at 0.6 and 1.2 m depth were measured after furrow irrigation with ceramic cup samplers during the 2014–15, 2015–16 and 2016–17 cotton seasons. Pre‐planting dissolved organic carbon (DOC) concentration in soil at 0.6–1.2 m depth during 2016–17 was 64 mg kg^?1 for maximum tilled cotton monoculture, 36 mg kg^?1 for minimum tilled cotton monoculture and 39 mg kg^?1 for cotton–wheat, and in maize and cotton subplots 51 and 41 mg kg^?1, respectively. Post‐harvest DOC values in soil were similar in all treatments (average of 32 mg DOC kg^?1). Total organic carbon (TOC) losses in deep drainage were equal to 2%–30% of TOC gained in irrigation water. Oxidized N losses in deep drainage ranged from 0.7% to 12% of applied N (260 kg ha^?1). NOx‐N concentrations in leachate under maize systems (20 mg L^?1) were up to 73% lower than those in cotton systems (75 mg L^?1). Maize sown in rotation with cotton can improve cotton yield, reduce N leaching and improve N use efficiency of subsequent cotton.     

Enhanced degradation of atrazine under field conditions correlates with a loss of weed control in the glasshouse

Enhanced degradation of atrazine has been reported in the literature, indicating the potential for reduced residual weed control with this herbicide. Experiments were conducted to determine the field dissipation of atrazine in three cropping systems: continuous Zea mays L. (CC) receiving atrazine applications each year, Gossypium hirsutum L.-Z. mays rotation (CCR) receiving applications of atrazine once every 2 years and a no atrazine history soil (NAH). Subsequent laboratory and greenhouse experiments were conducted with soil collected from these cropping systems to determine atrazine degradation, mineralization and residual weed control. Field dissipation of atrazine followed first-order kinetics, and calculated half-life values for atrazine combined over 2003 and 2005 increased in the order of CC (9 d) = CCR (10 d) < NAH (17 d). Greenhouse studies confirmed that the persistence of atrazine was approximately twofold greater in NAH soil than in CC or CCR soil. Biometer flask mineralization studies suggested that enhanced degradation of atrazine was due to rapid catabolism of the s-triazine ring. Glasshouse efficacy studies revealed a loss of residual weed control in CC and CCR soil compared with NAH soil. These data indicate that, under typical Mississippi Delta field conditions and agronomic practices, the persistence of atrazine may be reduced by at least 50% if the herbicide is applied more than once every 24 months. Glasshouse studies suggest that under these conditions a loss of residual weed control is possible.     

Use of glargine and lente insulins in cats with diabetes mellitus

The goals of this study were to compare the efficacy of once-daily administered Glargine insulin to twice-daily administered Lente insulin in cats with diabetes mellitus and to describe the use of a high-protein, low-carbohydrate diet designed for the management of diabetes mellitus in cats. All cats with naturally occurring diabetes mellitus were eligible for inclusion. Baseline testing included a physical examination, serum biochemistry, urinalysis and urine culture, serum thyroxine concentration, and serum fructosamine concentration. All cats were fed the high-protein, low-carbohydrate diet exclusively. Cats were randomized to receive either 0.5 U/kg Lente insulin q12h or 0.5 U/kg Glargine insulin q24h. Re-evaluations were performed on all cats at weeks 1, 2, 4, 8, and 12, and included an assessment of clinical signs, physical examination, 16-hour blood glucose curve, and serum fructosamine concentrations. Thirteen cats completed the study (Lente, n = 7, Glargine, n = 6). There was significant improvement in serum fructosamine and glucose concentrations in all cats but there was no significant difference between the 2 insulin groups. Four of the 13 cats were in complete remission by the end of the study period (Lente, n = 3; Glargine, n = 1). The results of the study support the use of once-daily insulin Glargine or twice-daily Lente insulin in combination with a high-protein, low-carbohydrate diet for treatment of feline diabetes mellitus.