Buckeye Dairy News: VOLUME 23, ISSUE 3

Mr. Jason Hartschuh, Extension Educator, Crawford County, Agriculture and Natural Resources, Ohio State University Extension, and Dr. Aaron Wilson, Climate Research Specialist, Ohio State University Extension

Heat stress can lead to major challenges for lactating cows during peak milk production and dry cows during the transition period. It can even cause challenges for calves before and after birth. In the U.S., heat stress is estimated to generate between $1.69 and $2.36 billion in total annual loss to the livestock industry.

While the upper limit of the thermal neutral zone for dairy cows is 68°F and for calves at one month of age is 77°F, heat stress includes more than just temperature. Heat stress factors in the humidity as well. For this reason, we utilize a temperature-humidity index (THI). While cooling should begin as soon as we leave the thermal neutral zone, heat stress for cows begins around a THI of 72, with 72 to 79 causing mild stress. At 79 to 88 THI, cows enter moderate heat stress which occurs at 80°F and 90% relative humidity (RH) or 85°F and 60% RH. Low end mild heat stress results in a milk production loss of 2.5 lb/cow/day, while the upper end of mild to moderate heat stress leads to 6 lb/cow/day of lost production. Figure one can be a useful tool for operating your cooling system. In the Stress Threshold (tan zone), fans should be operating. As the stress increases, more heat mitigation practices are needed. Besides monitoring environmental conditions, signs of heat stress can include increased breaths per minute, which should be between 40 to 60 under normal conditions. While not convenient, rectal temperature may also be used, which under normal conditions is between 101.2 to 102.5°F. If over 5 to 10% of your herd exceeds 105°F, your herd is in the emergency level of heat stress and additional cooling is definitely needed.

Figure 1. Temperature Humidity Index (THI) for cattle. Lactating dairy cows are at greater risk for heat stress when the THI exceeds 68.

The latest summer outlooks from the Climate Prediction Center call for an elevated probability of above average temperatures in Ohio for the month of June, as well as the June-August period (Figure 2). There are also indications that precipitation is likely to be above average throughout the period as well. While predicting THI for individual days is not possible this far in advance, the outlooks suggest a tendency toward higher values (warm temperatures and more moisture), especially during the first half of the summer.

To mitigate heat stress, cattle respond in a few natural ways and we can assist in these efforts. First, providing shade cloth will assist cattle as they naturally seek shade, especially for calves living in hutches. Second, cattle increase their sweating. This can lead to dehydration even as it provides evaporative cooling. We can supplement this response with a well-designed soaker system. They will also increase water intake by 1.2 to 2 times normal rates, leading to water needs per cow of up to 52 gal/day. Frequent checking to ensure adequate available water is critical, including drinking space, well-capacity, and water flow rates to keep your cows cool this year. Also, work with your nutritionist to make plans for ration adjustments before heat stress sets in, not after the effects are felt in your bulk tank. Lastly, walk your barns on a regular basis to check fan performance. The ideal wind speed in your barn should be around 5 mph.

Figure 2. Probabilistic temperature (left) and precipitation (right) outlooks from the NOAA Climate Prediction Center. Colors represent the probability of above, below, and near normal conditions for June-August 2021.

Dr. Maurice Eastridge, Professor and Extension Dairy Specialist, Department of Animal Sciences The Ohio State University

The North American Intercollegiate Dairy Challenge (NAIDC) program began in 2002 (https://www.dairychallenge.org/) and the first regional program began in the northeast in 2003. Since that time, Midwest, southern, and western regional dairy challenges have been organized. In addition, Ohio State hosts a local dairy challenge each fall semester to provide training for students in the dairy herd management course and other college students. Students from the Agricultural Technical Institute also have participated for several years, and during the past two years, students from Wilmington College have participated.

Dairy Challenge provides the opportunity for students to experience the process of evaluating management practices on a dairy farm and to interact with representatives in the dairy industry. The program is held in a contest format for undergraduate students whereby they are grouped into teams of three to four individuals. Locally, veterinary and graduate students are invited to attend the farm visit and participate in a meeting later in the evening with the contest judges to discuss observations on the farm. A farm in central Ohio is selected and records from the farm are made available to students. Typically, students are taken to the farm for a visit to interview the owner and to observe the facilities for about two hours. Then the teams of students return to campus to finalize their assessment into a presentation for the following day. The students present their findings to a panel of judges consisting of individuals from the University and from allied industries.

Midwest Regional Dairy Challenge

The 2021 Midwest Regional Dairy Challenge was hosted by Ohio State, Michigan State and Purdue universities. We were planning to host the event in Ft. Wayne, IN, but due to the pandemic, the event had to be held virtually. With the virtual nature of the program, the structure was changed whereby it was held February 16 through March 2. Dr. Roger Thomson at Michigan State worked feverishly in gathering records and videos of a herd in MI to use for the program. Given the virtual nature of the program and the difficulty in students working remotely with students from other universities, the teams this year were organized by schools for which they attend. The two following teams from Ohio State participated: Team 4 - Paul Bensman, Deanna Langenkamp, Sarah Lehner, and Robert Vance; Team 11 - Brietta Latham, Amanda Schmitmeyer, Ashley Stroud, and Laura Tavera. Team 4 placed second among the teams in their grouping.

National NAIDC

Due to the onset of the COVID-19, the 2020 National NAIDC program scheduled for March 26-28 in Green Bay, WI was cancelled. With the ongoing pandemic, the 2021 National NAIDC program was held virtually during April 14-16 and was hosted by the NAIDC Board with the gracious offerings by a herd in WI. The Ohio State contest team consisted of Paul Bensman, Brietta Latham, Sarah Lehner, and Caleb Rykaczewski. They took first place among the teams in their judging panel. Paul graduated this semester and is seeking employment in the feed industry; Brietta has been accepted into a graduate program at Washington State University; Caleb will be pursuing a MS degree in the OSU Department of Animal Sciences; and Sarah will be a senior during this next academic year with dual majors in Animal Sciences and Agribusiness and Applied Economics. The coaches for the Columbus based campus students are Dr. Maurice Eastridge and Dr. Benjamin Wenner.

Ohio State University Team, 2021 NAIDC Virtual Contest, received a First Place (Left to Right): Paul Bensman, Brietta Latham, Caleb Rykaczewski, and Sarah Lehner.