Biomedical subjects

S Willard

Publications and source records attributed to S Willard.

9 recordsLinked to original sources

PubMed2006

Evaporative tunnel cooling of dairy cows in the southeast. I: effect on body temperature and respiration rate.

The techniques used to mitigate the effects of heat stress on lactating dairy cows are often overwhelmed in the southeastern United States, where elevated heat and humidity often persist for extended periods. A model free-stall barn located at the North Mississippi Branch Experiment Station in Holly Springs was used to evaluate the potential of tunnel ventilation with evaporative cooling to alleviate heat stress in lactating dairy cows. Two studies were conducted using 2 groups of 10 lactating Holsteins housed in the tunnel barn (inside) and 2 groups of matched herdmates housed in an adjacent covered free-stall barn (outside), which was cooled by fans and sprinklers during 2001 or by shade and fans alone in 2003. Peak daytime temperatures inside were 5.2 +/- 0.18 degrees C below that outside in 2001 and 3.1 +/- 0.20 degrees C lower in 2003. Although evaporative cooling increased humidity by 22%, cows housed in the tunnel barn received 84% less exposure to moderate heat stress (temperature-humidity index > 80) in both years. Cooling cows with evaporative tunnel ventilation reduced respiration rates by 15.5 +/- 0.56 breaths/min and rectal temperatures by 0.6 +/- 0.02 degrees C compared with shade and fans alone in 2003. Cooling cows with evaporative tunnel ventilation reduced respiration rates by 13.1 +/- 0.78 breaths/min and rectal temperatures by 0.4 +/- 0.03 degrees C compared with fans and sprinklers in 2001. Thus, tunnel ventilation cooling dramatically reduced the exposure to heat stress and improved the comfort of lactating dairy cows when compared with traditional cooling technologies under the conditions present in the southeastern United States.

Air Conditioning↗

PubMed2006

Evaporative tunnel cooling of dairy cows in the southeast. II: impact on lactation performance.

Heat stress has a dramatic impact on the dairy industry, reducing production and profitability throughout the southeastern United States. In many regions, management techniques can be used to mitigate the effects of heat stress, but available cooling technologies are often overwhelmed by the conditions of chronic heat stress present in southeastern United States. Although combining tunnel ventilation and evaporative cooling (evaporative tunnel cooling) seems to provide superior cooling for dairy cows, there is a dearth of reports on the impact of this technology on milk production. A model evaporative tunnel cooling facility in northern Mississippi was studied using 2 groups of 10 lactating Holstein cows housed in the tunnel barn and 2 groups of 10 matched herdmates housed in an adjacent naturally ventilated free-stall barn. Two 10-wk trials were performed in 2 yr beginning June 25, 2001, and May 26, 2003, in which cows housed outside were cooled by traditional fans and shade alone (2003) or with sprinklers (2001). In both years, the use of evaporative tunnel cooling decreased exposure to conditions of moderate heat stress by 84%. Cows cooled by evaporative tunnel ventilation increased feed intake by 12 and 11% over cows housed outside in 2001 and 2003, respectively. Evaporative tunnel cooling had no effect on milk composition, but increased milk yield over the 10-wk trial by 2.6 +/- 0.27 and 2.8 +/- 0.19 kg/cow per day in 2001 and 2003, respectively. In addition, somatic cell count was decreased 27 to 49% by evaporative tunnel cooling. Thus, under the range of environmental conditions present, evaporative tunnel cooling reliably reduced exposure to conditions of heat stress and improved milk production of lactating dairy cows during the summer season.

Air Conditioning↗

PubMed2003

The effects of GnRH administration postinsemination on serum concentrations of progesterone and pregnancy rates in dairy cattle exposed to mild summer heat stress.

The objective of this study was to evaluate whether administration of GnRH postinsemination would improve reproductive performance in heat-stressed dairy cattle. Estrous cycles of Holstein cows were synchronized using the OvSynch protocol and cows were artificially inseminated. Cows were then administered the following treatments: control (no GnRH; n=37), GnRH (100 microg) on Day 5 (GnRH-D5; n=34), or GnRH (100 microg) on Day 11 (GnRH-D11; n=34) postinsemination. Cows were provided access to both fans and sprinklers, and environmental data was collected hourly. Rectal temperatures and blood samples were obtained from cows on Days -9, -2, 0 (AI) and on alternate days from Day 5 to Day 19 postinsemination. Blood serum was collected for the analysis of progesterone (P(4)) by RIA. In a subset of cows (n=6/treatment) ultrasonography was performed on alternate days from Day 5 to Day 19 postinsemination to assess numbers of corpora lutea (CL) and CL cross-sectional areas. Pregnancy status of cows was confirmed at Day 30 postinsemination. Environmental data indicated that cows experienced mild heat stress during the trials (mean daily THI=73-77). Serum P(4) was greater (P<0.05) after Day 9 for GnRH-D5 cows and after Day 15 for GnRH-D11 cows through Day 19 postinsemination. The number of CLs present for GnRH-D5 cows was greater (P<0.05) on Day 17 than in either the control or GnRH-D11 treatment groups. On Day 17 postinsemination, both the GnRH-D5 and GnRH-D11 cows were observed to have greater (P<0.05) total CL tissue area than control cows. The interval from insemination to when serum P(4) returned to <1 ng/ml (i.e. luteolysis and return to estrus) did not differ (P>0.10) among treatment groups. Control cows (19%) tended to exhibit lower pregnancy rates (P<0.08) compared to the GnRH-D5 and GnRH-D11 treatment groups combined (35%). In summary, the treatment of heat-stressed dairy cows with GnRH postinsemination (Day 5 or 11) results in the appearance of more CL tissue, increased serum concentrations of P(4) and a tendency toward greater pregnancy rates.

Animals↗

PubMed2001

Evaluation of the early conception factor (ECF) test for the detection of nonpregnancy in dairy cattle.

The ability to detect conception and/or conception failure in cattle would be beneficial to producers in formulating reproductive management plans. A new diagnostic test, the early conception factor (ECF) test, has been developed forthis application yetthe accuracy of this test has not been adequately determined. The objectives of this study were to evaluate the effectiveness of the ECF test for detecting the nonpregnant cow, and to compare the reliability of serum versus milk ECF tests relative to actual pregnancy rates. In Trial 1, Holstein heifers were synchronized, the animals were bred (timed-AI), and serum ECF tests were performed 72 h later. Heifers exhibiting a negative ECF test after AI were re-synchronized, bred again, and re-tested for ECF for up to three services. Relative to actual pregnancy rates, a negative ECF test was correct (i.e., true negative) 38.5% of the time over the three services. In Trial II, Holstein heifers were bred (AI) after observed estrus and serum ECF tests conducted between Days 1 and 3 and Days 7 and 9 after AI. In this trial, only 44.4% and 55.6% of the confirmed nonpregnant heifers were identified correctly by serum ECF analysis at Days 1 to 3 and Days 7 to 9 post-AI respectively. In Trial III, 40 lactating cows were synchronized, the animals were bred (AI), and serum and milk ECF tests were performed on Days 3, 9, 15, 21 and 30 after AI. Pregnancy diagnosis (ultrasound on Day 30 and palpation on Day 51) confirmed that 50% of the cows were pregnant to AI, while serum and milk ECF analysis indicated a 100% and 37.5% predicted pregnancy rate, respectively, at 30 d post-AI. Moreover, results of the serum and milk ECF tests disagreed with one another 36.9% of the time overall, while agreement between ECF and actual pregnancy rates were 50.6% and 45.6% for milk and serum respectively. Additionally in Trial III, a negative ECF result only identified 5% and 28.8% of nonpregnant cows overall for serum and milk tests respectively (i.e., true negatives), with a high incidence of false positive ECF results noted (47.5% and 31.3% for serum and milk, respectively). Collectively, these data indicate that the current ECF test cannot accurately identify the nonpregnant cow with the precision needed by the dairy producer.

Animals↗

PubMed2001