Subject: Effect of Bicar®Z supplementation on lactating dairy cows during Summer

The objective of this study was to evaluate the effectiveness of sodium bicarbonate Bicar®Z on the production of milk during Heat Stress.

The study was conducted by :

  • Baucells Joaquim, Centre Veterinari Tona S.L.
  • Torrellardona Josep, Associate Professor, Department of Medical Pathology,Universitat Autònoma de Barcelona – UAB
  • Moreira Bruno, Student of the 6th year of the MSc in Veterinary Medicine, Faculty of Veterinary Medicine ‐ University of Lisbon, Portugal.


Conditions of the study: trial conducted on 197 lactating cows in Spain

The study was conducted in a farm located in La Garrotxa (Girona, Spain). A total of 197 lactating Holstein cows were used.

Animals were distributed in three groups: two Treatment Groups and one Control Group.

Control cows (n=87) were fed a TMR diet once daily and treatment cows (n=111) received the same diet, but with the addition of 250 g per cow per day of sodium bicarbonate (Bicar®Z).

The study was conducted in two periods, considered as being the hottest during the year:

  • Period 1: the month of July
  • Period 2: the month of August

Temperature, humidity and rainfall were collected daily and the Temperature‐Humidity‐Index (THI) was calculated using the following formula:

THI= (1.8xT+32) ‐ ((0.55‐0.0055xRH) x (1.8xT‐26))

T=Temperature; RH=Relative Humidity.

Daily milk production and dry matter intake by group were determined daily. At the end of each period, respiration rate, rectal temperature and urine samples from a subset of cows (n=14 per treatment group) were collected.



Results indicate that the THI index average was just under the threshold of heat stress. However, at the hottest times of the day, the THI was at 86 and 88 for period 1 and 2, respectively. These THI are moderate to severe, and may result in an increase in respiratory rate and body temperature, and result in reduced milk production ranging from 3 to 7 kg of milk daily.

These results suggest that cows were at least during part of the day under heat stress conditions, which justifies the use of prevention measures and provide an adequate set‐up for the test of feeding Bicar®Z in heat‐stressed cows:

  • Rectal temperature was reduced by 0.52 ºC on average in cows fed Bicar®Z. This reduction is relevant for dairy cows and has been associated with a reduction of milk production (Zimbelman et al., 2009).
  • Urinary pH tended to decrease in the Bicar®Z treatment.
  • Bicarbonate concentration in the urine was also reduced with the Bicar®Z treatment, but potassium concentration was not affected.

Overall, data suggest that animals had some degree of heat stress, and that the addition of Bicar®Z appears to reduce some of them.

Production performance was better with Bicar®Z, likely with an above‐average response.

Milk production increased by 4.3 kg of milk, likely due to higher dry matter intake for the treatment group compared with control group (reduction of 2.2 kg of dry matter daily).


Conclusions: what can you learn from this study?

The experiment was conducted under heat stress conditions and the addition of Bicar®Z reduced some of the indicators of heat stress (rectal temperature, urinary bicarbonate and pH), and improved dry matter intake and milk production compared with control animals.

BicarZ Study 2 Effect of sodium bicarbonate supplementation on lactating dairy cows during summer