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 multiparous Holstein cows (Parity = 3.27 ± 1.50, DIM = 202 ± 36 d, BW = 702 ± 84 kg) were 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 were housed in a tie-stall barn located at the Penn State University Dairy Production Research and Teaching Center. Cows were fed once daily at 0800 h at approximately 110% of expected dry matter intake. Treatments were empty control (no supplementation) and octanoic acid (Food grade octanoic acid, Sigma-Aldrich, St. Louis, MO) at 600ml (550 g) /day (OA). The basal diet will be mixed in a Kuhn RC 250 mixer and the treatments were mixed into the basal diet manually in the feed trough pre-feeding. Rectal temperatures (RT) were measured vaginally with a thermometer twice per day during the treatment period at 0730 h and 1600 h. Fresh feed samples and refusals were collected at the beginning of each treatment period. The nutritional value of the TMR was analyzed by Near-Infrared Reflectance spectroscopy (NIR) procedures (Cumberland Valley Analytical Services Inc., Maugansville, MD).
Milk Sampling Analysis
Cows were milked twice daily at 0700 and 1900 h, milk yields were determined by an integrated milk meter (AfiMilk; SAE Afikim, Israel). Milk samples were collected the day before on days 3, 6, and 7 of each treatment period. Milk samples were sent to the local DHIA laboratory (Dairy One DHIA) for components evaluation.
Blood Sampling Analysis
Blood samples were collected on days 3, 6, and 7 of each treatment period at 1600 h to determine plasma acylated ghrelin concentration (aGhr). Blood samples were collected into tubes containing potassium EDTA (Vacutainer, Becton Dickinson, Franklin Lakes, NJ) and then placed on ice. Plasma was harvested within 15 min of blood collection by centrifugation at 2,000 x g for 15 min. Plasma samples were treated with 50 μL of 1 N HCl and 10 μL of phenylmethylsulfonyl fluoride (PMSF) per mL of plasma for acylated ghrelin concentration analysis by RIA. All plasma samples were then frozen and stored at -20 ℃.
Data were analyzed as repeated measures in SAS (version 9.4, SAS Institute Inc., Cary, NC). Repeated measures method was used to analyze RT, DMI, milk components, and aGhr. The model included the effects of treatment and test day. Test day was the repeated variable, cow was the subject. The compound symmetry, autoregressive 1, and spatial power covariance structures were tested for every analysis, the model had the lowest Akaike’s information criterion, Akaike’s information criterion with correction, and Bayesian information criterion values was selected to analyze that trait. The Kenwood Rogers method was used to adjust the denominator degrees of freedom. Results are reported as least squares means of the treatment. Differences were declared significant at P ≤ 0.05 and tendencies at 0.05 < P ≤ 0.10.
The data are being analyzed, I will update the results after it’s finished.
The data are being analyzed, I will update the conclusion after it’s finished.
Education & Outreach Activities and Participation Summary
Had several discussions with farmers and other faculties in the Ag science department.
The data are being analyzed, I will update this section after it’s finished.
The data are being analyzed, I will update this section after it’s finished.