Rumen indigestion and SARA, a related but more severe form of rumen indigestion, are important disease conditions that affect the health and economic performance of dairy herds. Clinical signs associated with rumen indigestion and SARA include a decrease in milk yield and rumen motility and diarrhea.1 In cattle, when the ratio of concentrate to effective fiber in the ration increases, the production of volatile fatty acids can exceed their rate of absorption by the rumen epithelium, causing the rumen pH to decrease. That decrease in rumen pH can cause rumen indigestion and potentially SARA. Subacute ruminal acidosis is defined as a rumen pH < 5.6 for a period ranging from 148 to 243 min/d or a rumen pH < 5.8 for a period ranging from 284 to 475 min/d, whereas rumen indigestion is defined as a disturbance in rumen motility often associated with a decrease in rumen pH that is less drastic than that observed with SARA or some other cause such as the ingestion of mycotoxins in moldy feed.1 Unfortunately, the onset of clinical signs associated with SARA are often delayed until after the period of pathologically low rumen pH, which makes diagnosis and early intervention to control SARA difficult.2,3 In addition to ration composition, rumen disorders can be caused by extended periods between feedings and restricted feeding subsequent to feed delivery errors.4 Rumen disorders can also develop during hot weather, particularly during extended periods of heat stress, because cows tend to avoid eating during the heat of the day and then overeat at night, when the ambient temperature is cooler.4
Monitoring milk fat percentage has been proposed as a diagnostic tool for assessing whether rumen indigestion and SARA are present at the herd level; however, the association between rumen indigestion or SARA and milk fat percentage is inconsistent, and herds with milk fat percentages within reference limits may still have rumen acidosis problems.4,5 Results of a report6 that summarized the findings of 23 studies indicate that many cows with a rumen pH < 5.8 have milk fat percentages that are within reference limits (3.0% to 3.5%), and milk fat percentage is poorly correlated (r = 0.39) with rumen pH. Moreover, the effects of rumen indigestion and SARA on milk production and milk components are usually transient and variable.3,7,8
Currently, the milking parlors on many commercial dairy operations are equipped with systems that can provide real-time data on milk yield and milk components for individual cows. Thus, the purpose of the study reported here was to identify alterations in milk components that could be used to detect cows with spontaneously occurring rumen indigestion. We hypothesized that lactating dairy cows with rumen indigestion or SARA would have detectable changes in milk components prior to the onset of overt clinical signs that would allow those cows to be identified and managed in a way that would improve their health and productivity and mitigate the need for prolonged medical treatment.
Days in milk
Receiver operating characteristic
Subacute ruminal acidosis
Afimilk Ltd, Kibbutz Afikim, Israel.
Ruminator, Products of Professor Geishauser, Guelph, ON, Canada.
pHTestr 30, Oakton Instruments, Vernon Hills, Ill.
SAS, version 9.4, SAS Institute Inc, Cary, NC.
1. Diseases of the alimentary tract II. In: Radostits OM, Gay CC, Hinchcliff KW, et al, eds. Veterinary medicine: a textbook of the diseases of cattle, horses, sheep, and goats. 10th ed. Philadelphia: Saunders Elsevier, 2007; 314–318.
2. Enemark JM, Jørgensen RJ, Enemark PS. Rumen acidosis with a special emphasis on diagnostic aspects of subclinical rumen acidosis: a review. Vet Zootech 2002; 20: 16–29.
3. Enemark JM, Jørgensen RJ, Kristensen NB. An evaluation of parameters for the detection of subclinical rumen acidosis in dairy herds. Vet Res Commun 2004; 28: 687–709.
4. Oetzel GR. Subacute ruminal acidosis in dairy herds: physiology, pathophysiology, milk fat responses, and nutritional management. Available at: citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.179.3298&rep=rep1&type=pdf. Accessed Feb 28, 2017.
5. Nordlund KV, Garret EF. Rumenocentesis: a technique for collecting rumen fluid for the diagnosis of subacute rumen acidosis in dairy herds. Bovine Pract 1994; 28: 109–112.
6. Allen MS. Relationship between fermentation acid production in the rumen and the requirement for physically effective fiber. J Dairy Sci 1997; 80: 1447–1462.
7. Enemark JM. The monitoring, prevention and treatment of subacute ruminal acidosis (SARA): a review. Vet J 2008; 176: 32–43.
8. Krause KM, Oetzel GR. Inducing subacute ruminal acidosis in lactating dairy cows. J Dairy Sci 2005; 88: 3633–3639.
9. National Research Council. Nutrient requirements of dairy cattle. 7th revised ed. Washington, DC: National Academies Press, 2001; 381.
10. Kaniyamattam K, DeVries A. Agreement between milk fat, protein, and lactose observations collected from the Dairy Herd Improvement Association (DHIA) and a real-time milk analyzer. J Dairy Sci 2014; 97: 2896–2908.
11. Diepersloot EJ. The use of technology for improved cow health to increase production and reproduction, in Proceedings. 47th Florida Dairy Prod Conf 2011; 30–36.
12. Oetzel GR. Monitoring and testing dairy herds for metabolic disease. Vet Clin North Am Food Anim Pract 2004; 20: 651–674.
13. Nordlund KN. Herd-based diagnosis of subacute ruminal acidosis. Available at: pdfs.semanticscholar.org/d9ec/7342c53e2721c82b44413fb2577e04c4fdd3.pdf. Accessed Feb 28, 2017.
14. Duffield T, Plaizier JC, Fairfield A, et al. Comparison of techniques for measurement of rumen pH in lactating dairy cows. J Dairy Sci 2004; 87: 59–66.
16. Dohoo I, Martin W, Stryhn H. Screening and diagnostic tests. In: Veterinary epidemiologic research. 2nd ed. Charlottetown, PE, Canada: VER Inc, 2009; 105–110.
17. Greiner M, Pfeiffer D, Smith RD. Principles and practical application of the receiver-operating characteristic analysis for diagnostic tests. Prev Vet Med 2000; 45: 23–41.
20. Alzahal O, Or-Rashid MM, Greenwood SL, et al. Effect of subacute ruminal acidosis on milk fat concentration, yield and fatty acid profile of dairy cows receiving soybean oil. J Dairy Res 2010; 77: 376–384.
21. Colman E, Fokkink WB, Craninx M, et al. Effect of induction of subacute ruminal acidosis on milk fat profile and rumen parameters. J Dairy Sci 2010; 93: 4759–4773.
23. Schmidt GH. Effect of insulin on yield and composition of milk of dairy cows. J Dairy Sci 1966; 49: 381–385.
24. Gowen JW, Tobey ER. On the mechanism of milk secretion: the influence of insulin and phloridzin. J Gen Physiol 1931; 15: 67–85.
25. Krause KM, Oetzel GR. Understanding and preventing subacute ruminal acidosis in dairy herds: a review. Anim Feed Sci Technol 2006; 126: 215–236.
27. Garrett EF, Pereira MN, Nordlund KV, et al. Diagnostic methods for the detection of subacute ruminal acidosis in dairy cows. J Dairy Sci 1999; 82: 1170–1178.