Effect of rumen emptying on biting rate of cows grazing Brachiaria brizantha at three stocking rates in Yucatán, México.

The experiment was carried out in the east of Yucatan, in pastures of B. brizantha. It was of three months duration during the end of the rainy season. Four rumen cannulated cows with an average weight of 442 kg were used at all of three stocking rates: Low (2LU/ha), Medium (4LU/ha) and High (6LU/ha), to evaluate the effect of an empty rumen on the rate of biting, which was measured as the time taken to take 20 uninterrupted bites on ten occasions. The measurements were made on two sequential days at 09.00 h, the first under normal conditions, the second with an empty rumen. There was no effect (P<0.050 of rumen emptying on the rate of biting which was 24 bites per minute when the animals were normal, and 25 bites a minute when the rumen was empty. On the other hand, there was a reduction of 8% in the rate of biting for the animals at the high stocking rate compared with the low and medium stocking rates. The finding that bite rate was not affected by an empty the rumen is evidence which gives confidence in the use of cannulated animals as collectors of representative samples of forage under grazing conditions.