Heat stress is responsible for $897 million of loss to the United States dairy industry, primarily through
depressed feed intake and resulting losses in milk production. Heat stress for dairy cattle is common even in
the Northeast; for instance, data from Penn State’s local weather station demonstrates that ambient
temperature can reach as high as 38°C with almost 100% relative humidity during summer; these conditions
are deemed as severe heat stress for dairy cows. Farmers and researchers have discovered and utilized many
methods to minimize the negative impact of heat stress, including fans, sprinklers, and shades. For many
farms, these methods are either cost prohibitive or do not fit within their management system. Ghrelin is a
hormone that exists in active (acylated) and inactive (non-acylated) forms and that is involved with modulation
of feed intake, thermogenesis, energy expenditure, adipogenesis, and locomotive activity. Octanoic acid (OA)
is an important substrate of the ghrelin acylation process and dietary OA supplementation has been shown to
stimulate appetite and decrease body core temperature in rats and humans. However, few studies about
dietary OA supplementation had been conducted on dairy cows. Therefore, we propose to evaluate the effects
of dietary OA on lactating dairy cows under moderate heat stress conditions. The objectives are to: investigate
the impact of dietary OA on plasma active ghrelin concentration, core body temperature, dry matter intake, and
milk production under moderate heat stress conditions.
The project has not finished yet so there’s no succinct statement of research conclusion at this time.
The objectives of this project are:
1. Investigate the impact of dietary octanoic acid on plasma acylated ghrelin concentration in dairy cows under moderate heat stress;
2. Investigate the impact of dietary octanoic acid on core body temperature in dairy cows under moderate heat stress;
3. Investigate the impact of dietary octanoic acid on dry matter intake and energy intake in dairy cows under moderate heat stress;
4. Investigate the impact of dietary octanoic acid on milk and component production under moderate heat stress.
The purpose of this project is to help farmers mitigate the negative impact of heat stress on dairy cows with dietary
octanoic acid (OA) supplementation. Heat stress is a challenge to cow welfare and profitability to dairy farmers
world-wide. Heat stress was previously perceived to be a problem in areas where summer is long and hot, such as
Southern United States, Latin American Countries, or Southeast Asian Countries. But studies show that heat
stress also causes damage in “cooler” areas such as Northern United States and Canada, Udomprasert and
Williamson, (1987) reported, conception rate can decrease 11% in summer compare to winter in Minnesota, USA.
For instance, data from Penn State’s local weather station demonstrates that ambient temperature can reach as
high as 38°C with almost 100% relative humidity during summer; these conditions are deemed as severe heat
stress for dairy cows. Main contributors for heat stress related economic losses are: reduced milk production,
impaired reproduction, increased health related problems, and increased culling rate (St-Pierre et al., 2003). The
negative impact of heat stress on dairy cows is a growing problem because of the extra metabolic heat produced
with the increasing milk production and unfavorable genetic relationship between selecting for milk production and
heat stress (Ravagnolo and Misztal, 2000).
Dietary OA supplementation has been shown to stimulate appetite and decrease core body temperature in rats
and humans. If OA has the same effects in cattle, it could be a potent mitigator of heat stress. However, few
studies have explored dietary OA supplementation in dairy cows.
Our proposal addresses following themes in sustainable agriculture:
1.Reduced health risks for dairy cows. Our proposal will contribute toward an alleviation of heat stress and, as a
consequence, associated related health risks.
2.Improved productivity. Less heat stressed dairy cows will eat more feed, produce more milk, and become more
3.Reduction of costs and increased net farm income. With less heat stress related diseases and improved
reproduction, farmers can reduce disease treatment and reproductive costs. This, coupled with reduction in milk
production loss, will improve net farm income.
4.Improved quality of life for farmers and their employees. Based on the benefits mentioned above, farmers will
have more income to spend, fewer sick cows to handle, and more spare time to enjoy with families and friends.
Experimental Design and Treatments
Eight primiparous late lactation Holstein cows would be assigned to treatments in a 2 x 2 Latin square design with
14-d period, which included a 7-d washout and 7-d treatment period. Cows would be housed in a tie-stall barn
located at the Penn State University Dairy Production Research and Teaching Center.
Cows would be fed once daily at 1000 h at approximately 110% of expected dry matter intake and daily refusals
would be weighed and recorded. Treatments will be sodium bicarbonate control (3% of diet DM), and octanoic
acid at 3% of diet DM (OA; Food grade octanoic acid, Sigma-Aldrich, St. Louis, MO). The control was designed to
provide equal amount of DM as the OA treatment. The basal diet will be mixed in a Kuhn RC 250 mixer and the
treatments mixed into the basal diet in portable mixer (Rissler TMR mixer 1050, Rissler, Mohnton, PA) before
Determination of the Trial Period
According to historical climate data from the National Climatic Data Center (https://www.ncdc.noaa.gov/cdoweb/
search) for State College, PA. since 2001 the average of daily maximum temperature was 26°C while the
average of daily maximum relative humidity was 97 %. These conditions indicate that cows will be in slight to
moderate heat stress on an average of at least 10 h per day in August. According to the daily milk yield data
collected from the Penn State University Dairy Production Research and Teaching Center’s milking system
(AfiMilk; SAE Afikim, Israel), since 2001, cows’ daily milk yield was highest in May (39.72 kg/cow/day), and then
gradually decline each month during summer. While cows’ daily milk yield was lowest in August (36.85
kg/cow/day) and September (36.52 kg/cow/day). Based on these numbers, we decided that August are the
optimal time for this project.
Feed Sampling and Analysis
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Diet fresh and refusal weight would be recorded daily, diet and refusal DM will be evaluated weekly for DMI
determination (72 h in a forced-air oven at 55°C). Nutrient composition of experimental diets would also be
evaluated weekly by Cumberland Valley Analytical Services (Maugansville, MD). Daily energy intake would be
calculated based on the DMI and nutrient composition. The control diet was selected because the treatment is not
expected to change the rumen fermentation and physical fill of the diet. This approach was also described by
Urrutia et al. (2019).
Milk Sampling Analysis
Cows will be milked twice daily at 0500 and 1700 h, milk yield will be determined by an integrated milk meter
(AfiMilk; SAE Afikim, Israel). Milk samples will be collected the day before treatment period and on day 3, 6, and 7
of the treatment period. Milk samples will be sent to local DHIA laboratory (Dairy One DHIA) for components
Blood Sampling Analysis
Blood sample would be collected the day before treatment period and on day 3, 6, and 7 of treatment period at
0930 h before feeding to determine their pre-prandial plasma acylated ghrelin concentration (Sugino et al., 2002;
Bradford et al., 2008). Blood would be collected into tubes containing potassium EDTA (Vacutainer, Becton
Dickinson, Franklin Lakes, NJ) and then placed on ice. Within 60 min of collection, samples would be centrifuged
at 2,000 * g for 15 min, plasma would be collected, and samples would be frozen at 20°C for subsequent
analyses. Acylated ghrelin would be measured with the Ghrelin RIA kit (GHRA-88HK, Sigma-Aldrich, St. Louis,
Core Body Measurements
Core body temperature would be measured vaginally with a thermometer twice per day during the treatment
period at 0930 h and 1400 h.
Data would be analyzed as repeated measures in SAS (version 9.4, SAS Institute Inc., Cary, NC) and the model
will include the random effect of cow, period, and treatment groups, and the fixed effects of a covariate (observed
value for response variables on the day before treatment period), treatment, day of treatment, and their
The response variables of the analysis are: pre-prandial plasma acylated ghrelin concentration, core body
temperature, daily DMI, daily milk yield, and milk fat percentage. Differences between treatment groups would be
declared significant at P < 0.05, and tendencies at 0.05= < P < 0.10.
The project has not finished yet, so at this point, there’re no results to report.
The project has not finished yet, so at this point, there’s no conclusion to report.
Education & Outreach Activities and Participation Summary
Had several discussions with farmers and other faculties in the Ag science department.
The project has not finished yet, so at this point, there’s no outcome to report.
The project has not finished yet, so at this point, there’s no knowledge to report.