[Hematological effects produced on horses and sheeps pasturing upon Brachiaria radicans Napper (Tanner grass) in winter time (author’s transl)].

This research study examined the impact of Brachiaria radicans Napper, or Tanner grass, on the blood composition of horses and sheep during the winter months, indicating minor anemia in sheep but no significant negative effects as compared with summer.

Introduction and Methods

• The research involved two mares and twelve adult castrated sheep of the ‘Ideal’ breed.
• These animals were pastured on a field predominantly made up of Brachiaria radicans Napper for one and two months respectively.
• The study was conducted during winter, when Brachiaria radicans Napper takes on a yellow-green color – differing from its usual green color during the warmer seasons.
• The researchers conducted weekly clinical and hematological evaluations to observe any changes or trends in the animals’ health and blood composition.

Results

• The typical symptoms of intoxication that were observed in previous research when the grass was green did not occur during this winter study period.
• On examining the blood samples, the researchers noted a mild anemia in the sheep. This anemia manifested as macrocytic (larger than normal red blood cells) and hypochromic (decreased amount of hemoglobin in the red blood cells).
• Additionally, some of the red blood cells exhibited basophilic stippling (dots in red blood cells under a microscope), leading to the presence of anisocytosis (red blood cells of unequal sizes).
• Unlike in previous studies conducted during other seasons, no methemoglobin (a form of hemoglobin that does not bind to oxygen well) and Heinz bodies (a form of damage to hemoglobin caused by oxidant damage) were detected in the blood samples of sheep.

Interpretation and Conclusion

• The Brachiaria radicans Napper grass had low levels of nitrate, a compound that had previously been suggested as the possible cause of intoxication in the animals.
• Given the lack of observed harmful effects and the low nitrate levels in the Brachiaria radicans Napper, the researchers concluded that if there was any toxicity, it must be due to some other component of the plant.
• This study demonstrates a change in the impacts on the animals’ blood composition based on the time of year and the state of the Brachiaria radicans Napper growth, indicating that the plant may have different effects on the animals during different seasons.