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To describe effects of season on milk production in Holstein dairy cows and to determine the location and effectiveness of fans and sprinklers in the management of stress attributable to season.


Longitudinal observational study.


141 dairy herds for which owners used the Dairy Herd Improvement Association's database for production and reproduction record keeping.


Owners were interviewed to identify location of fans, shade structures, and sprinklers. Production and reproduction data were retrieved from the database, and a mixed model ANOVA was used to estimate effects of season, parity, and use of sprinklers, and fans on milk production.


Daily peak milk production decreased for all parity groups in the summer, but the effect decreased with increasing days in lactation. Use of sprinklers increased peak milk production in parity-1 and -3 or higher cows, but use of fans did not significantly alter effects of season. After calving in the summer, 305-day milk production decreased in parity-2 and -3 cows. This decrease was not significantly modified by the presence of sprinklers or fans.

Clinical Implications

Use of sprinklers may increase peak milk production in high-producing cows and could be recommended for reducing heat and total stress during this time. Production-oriented veterinarians should be cautious when recommending use of sprinklers and fans to increase production because of the wide confidence intervals describing their effectiveness. Management of parity-2 or higher cows so that they calve from October to June could increase 305-day milk production. (J Am Vet Med Assoc 1999;214:85–88)

Free access
in Journal of the American Veterinary Medical Association


Effects of vena caval banding on portal venous and vena caval hemodynamics were examined in 6 control dogs and in 10 dogs that had undergone attenuation (banding) of the abdominal part of the caudal vena cava and had dimethylnitrosamine-induced multiple portosystemic shunts (pss). Additionally, indocyanine green (icg) extraction and clearance after infusion to steady state were used to calculate hepatic plasma flow in these dogs. Sixteen dogs were randomly assigned to 2 groups: control (n = 6) or diseased(n= 10). Diseased dogs were administered dimethylnitrosamine (2 mg/kg, po, twice weekly) until multiple pss developed, as assessed by results of clinical laboratory tests, ultrasonography, and hepatic scintigraphy. Shunts were confirmed visually at celiotomy and by contrast portography. Venous pressures (caudal vena caval, portal, and hepatic) were recorded before and after vena caval banding for up to 7 days in dogs from both groups. Peritoneal cavity pressures were recorded in all dogs after closure of the body wall. To determine icg extraction and clearance, a bolus injection of icg (0.5 mg/kg, iv) was administered, followed by steady-state infusion of 0.097 mg/min. Extractions and clearances of icg were measured, and from these, hepatic plasma flow rates were determined immediately before and after banding and at 6 hours, 48 hours, and 7 days after banding.

The gradient (caudal vena caval pressure within 1 to 2 mm of Hg of portal pressure) between caudal vena cava and portal venous pressures established at banding was maintained after the first hour in both groups. Caudal vena cava pressures established at banding were maintained throughout the study, with the exception of the first hour in diseased dogs. Extraction ratios were higher in control dogs at all times, except at 48 hours. Clearance was higher in control dogs at all times. Hepatic plasma flow did not differ between groups, except immediately after banding, when flow was greater in diseased dogs, and differences were not found over time in either group. This study indicated that vena caval banding in this model of experimentally induced multiple pss increases and maintains caudal vena cava pressure, relative to portal venous pressure (after the first hour) for 7 days, and that calculated hepatic plasma flow is not persistently improved by vena caval banding.

Free access
in American Journal of Veterinary Research