Clinical and behavioral evaluations of cattle with experimental ruminal acidosis by short chain fatty acids

Thirteen, rumen cannulated, Nellore cows (544.2 ± 47 kg) were used in two different studies. The first one was carried out to set up a standard model for induction of rumen acidosis by short chain fatty acid (RASCFA) in heavier cattle (n= 3 cows) with the use of citrus pulp (CF) (1.65% BW of CF into the rumen). The remaining, studied the effect of RASCFA on ruminal metabolism, behavior changes, clinical and diagnostics aspects (n=10). The cows were housed in individual tie stalls and fed twice a day 75% coast-cross hay and 25% commercial concentrates, for 45d before the trials, with feed intake (FI) monitored. The standard model caused initially rumen lactic acidosis, but after some corrections (g CP = BW 0.75 x 54.7) induced RASCFA adequately (rumen pH between 5.8 and 5.2 for at least 5h). On the day before and for three consecutive days after induction the following variables were recorded every 5 min: time spending for rumination (TR), for feeding intake (TFI), for idle laying down (ILD) or idle standing (IS). On the day before and during the day of induction an intraruminal bolus for measuring rumen, pH each 5 min, were installed. Rumen fluid, blood, fecal and urine samples were collected and clinical examination carried out every three hour on the day of induction. Rumen movements (RM) were also recorded on the 2ndand 3rd d 9h after the morning feeding. The rumen pH of RASCFA was always lower than the basal time and the lasting of acidosis was 547 ± 215 min, minimum pH 5.38 ± 0.16 and the average pH during acidosis 5.62 ± 0.1. The rumen acidosis was caused mainly by SCFA (maximum 118.4 ± 9.3 mM/L), L-lactic acid (7.17mM/L) and D-lactic acid (0.56 mM/L) on the 6thh. Osmolality was maximum at the 3rdh (405.5 ± 45.2 mOsm/L) mostly caused by lactic acid and glucose. FI was reduced 66.3 % on the 1std and 48% on the 2ndd returning to normal status on the 3rd d (basal 10 ± 1,23 kg). The FI was positively influenced by the average rumen pH (R2 = 0.679), the RM (R2 = 0.807), and MR (R2 = 0.739), but negatively by the rumen osmolality (R2 = 0.546). The time for consumption of 1 kg DM was higher on the 1std (94 min) and 2nd d (90 min) but recovery on the 3rd d (basal 32 ± 4 min). The TR was reduced on the 1st d (58.4%), 2nd d (48.7%) and 3rd d (20.9) (basal 450 ± 68 min) and was mostly positively influenced by the average rumen pH (R2 = 0.8077). The IS hasnt change, but ILD time increased by 38.9% on the 1std, 26.6% on the 2ndd returning to normal on the 3rdd (basal 380 ± 60 min). The ILD time was negatively influenced by the minimum rumen pH (R2 = 0.466) and the neurological depression status (R2 = 0.616). The neurological depression status was positively influenced by the rumen minimum pH (R2 = 0.639) and positively by the level of rumen L-lactic acid (R2 = 0.3733). The tests of redox potential, titratable acidity and time for reduction of methylene blue, along with rumen pH, are good alternatives for diagnosing RASCFA. (AU)