Rumen pH: The best moment to obtain a rumen liquid sample is between 5 to 8 hours after offering fresh TMR. It is generally assumed that a herd has no SARA problems when all animals tested (minimum of 12 from the herd or pen) by rumenocentesis have a pH equal or greater than 5.8 (Tajik and Nazifi. 2011).
If the pH of one third or more of the cows tested is between 5.6 and 5.8, or less, the group is then considered at a high risk of SARA. When more than 25% of the animals have ruminal pH’s below 5.5, then the herd is considered to have SARA. It is also important to know the length of time during which the ruminal pH was below 5.6.
A one-time intake of grain that dropped the ruminal pH suddenly, but only for a short time may not be as damaging compared to low effective fiber diet that maintain acid conditions over a longer period of time.
- Rumen activity: In a herd with good rumen health, between 50 and 75% of the cows that are lying down should be chewing their cud. It is advisable to repeat this observation throughout the day as most rumination activity occurs during the evening and night.
- The incidence of laminitis within a herd should be under 10%.
- Milk fat percent: Values below 2.5% should not exceed 10% of the individual Holstein cows tested.
- Manure: In general, manure from cows with SARA is more liquid and foamy. In addition, it may contain mucous or mucin casts, fiber particles larger than 0.4 inches, bubbles, and undigested grain particles. Manure can be analyzed with the NASCO Digestion Analyzer (NDA); according to recommendations by the Miner Institute (Cotanch and Darrah, 2012), less than 50% of the manure sample should be retained in the sieves according to the following distribution:
Sieve Sieve opening (mm) % Retained Top 4.76 <10% Middle 2.38 10 - 20% Bottom 1.59 10 - 20%
- Particle size of the diet: The Penn State particle size separator (PSPSS) allows for the evaluation of particle size in TMR’s. The material retained on each sieve should follow the distribution below:
Suggestions for TMR particle size Sieve Sieve opening (mm) % Retained Top 19 2 - 8% Middle 8 30 - 50% Bottom 1.8 30 - 50% Tray - ≤ 20
The PSPSS allows corroborating if cows are selecting finer particles of the TMR. In order to do this, it is necessary to verify the uniformity of the TMR throughout the day (every 6 h) and that of the refusals. The material retained in each sieve of the PSPSS should not vary more than 5 percentage units compared to the TMR just fed. If it does, then the cows are likely sorting the TMR.