Biomedical subjects

D D Magee

Publications and source records attributed to D D Magee.

3 recordsLinked to original sources

PubMed1999

Effects of environmental management on seasonal decrease in milk production in dairy cattle.

OBJECTIVE: 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. DESIGN: Longitudinal observational study. ANIMALS: 141 dairy herds for which owners used the Dairy Herd Improvement Association's database for production and reproduction record keeping. PROCEDURE: 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. RESULTS: 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.

Animal Husbandry↗

PubMed1996

Management of summer infertility in Texas Holstein dairy cattle.

The objectives of this study were to describe the impact of season on pregnancy odds and the effect of specific herd management practices to modify seasonal effects. Pregnancy odds were significantly associated with herd, season, days in milk, and milk production, and with 3 interactions: milk production-by-days in milk, milk production-by-parity, and season-by-days in milk. The estimate of relative risk for summer insemination resulting in pregnancy was 0.66 at 60 d post calving and 0.53 at 160 d post calving. Shade in the lounging area, holding pen or dry cow areas, and fans in the lounging area had positive effects on summer pregnancy odds. Fans in the dry cow area were associated with a reduced odds of pregnancy. Sprinklers did not significantly modify the effect of season on pregnancy odds. The strong seasonal decrease in pregnancy odds was less severe on farms that provided shade in the lounging areas, holding pens and dry cow areas and fans in lounging areas. Insemination strategies can also be adapted to increase the pregnancy odds.

Journal Article↗

PubMed1995

Outcome of scrotal hydrocele in 26 bulls.

Changes in scrotal sonograms and semen quality were monitored in 26 bulls with idiopathic scrotal hydrocele over a 4-month period. After 120 days, scrotal hydrocele had resolved (ultrasonographically, fluid was not detectable within the vaginal process) in 85% (22/26) of the bulls. Percentage of bulls with unilateral scrotal hydrocele that resolved was higher than that for bulls with bilateral hydrocele (94 vs 62.5% or 17/18 bulls vs 5/8 bulls, respectively). After 120 days, 77% (20/26) of the bulls passed a breeding soundness evaluation. At 90 days, semen quality was satisfactory in more of the bulls with unilateral disease (9/18) than with bilateral disease (1/8). The finding of multifocal echodensities in the testicular parenchyma was not correlated with a poor breeding soundness score or with a high number of spermatozoal abnormalities. The prognosis for full recovery in bulls with scrotal hydrocele likely depends on the severity and duration of the condition.

Animals↗