Important factors that influence dairy herd productivity are the type and incidence of disease in the herd. The basis of disease control programs includes knowledge of the frequency and biological effect of disease, and information on the effectiveness of control procedures.
Most studies report incidence rates of only common, easily diagnosed clinical diseases, such as mastitis, lameness, milk fever, retained placenta, or displaced abomasum. The frequency of subclinical disease is much more difficult to discern.
The cost to obtain subclinical disease information is inflated by the need to use screening tests for diagnosis (eg, culture or somatic cell count [SCC] for mastitis, fecal culture or ELISA for paratuberculosis). However, the high cost of subclinical diseases such as mastitis or paratuberculosis might justify the considerable expense of a control program, and veterinarians can play a vital role in designing these programs.
There is zero tolerance for some diseases that have serious consequences for public health. For example, the diagnosis of even one case of bovine spongiform encephalopathy, brucellosis, rabies, or tuberculosis in areas thought to be free of those conditions is cause for immediate action.
Influence of Disease on Productivity of Dairy Cattle
Increased mortality rate or culling, decreased milk or component yield, and decreased reproductive efficiency are all potential results of disease in adult cows. Milk production is often profoundly decreased in cows with clinical disease. The duration of acute clinical disease is often short; however, the effects of the disease can persist throughout lactation.
In dairy cows, early lactation is the highest risk period for many diseases. Disease during early lactation can decrease peak milk yields and therefore contribute to lower total lactational yields. Through advances in animal husbandry, nutrition, and health management programs, in concert with close involvement of veterinarians, many dairy farms have minimized clinical syndromes associated with infectious and metabolic disease.
The trend toward larger units and shrinking profit margins has encouraged a shift toward optimizing dairy herd or group productivity by decreasing the incidence of subclinical diseases such as ketosis, mastitis, acidosis, lameness, and laminitis, which can have major impacts.
Infectious disease still represents a major source of loss to dairy industries worldwide. In Britain, outbreaks of foot-and-mouth disease (as well as of bovine spongiform encephalopathy) are dramatic examples of the disastrous effects of infectious diseases on productivity. Other serious infectious diseases (eg, tuberculosis, brucellosis, bluetongue, and vesicular stomatitis) continue to affect livestock around the world.
In North America, more common infectious diseases that must be actively controlled include diseases caused by the contagious mastitis pathogens Mycoplasma bovis, Staphylococcus aureus, and Streptococcus agalactiae; bovine viral diarrhea; salmonellosis; paratuberculosis; and pneumonia. Excellent control programs have been developed for most of these diseases; however, the adoption of these programs is quite variable.
The effects of disease on the productivity of dairy cows can be direct (eg, mastitis can cause a profound decrease in milk yield) or indirect (eg, lameness can lead to decreased feed intake, thus causing decreased milk yield).
Disorders that occur in early lactation can also cause cascading effects that ultimately decrease productivity over the entire lactation period. For example, cows diagnosed with hypocalcemia are at increased risk of retained placenta, complicated ketosis, mastitis, and displaced abomasum. In addition, hyperketonemia can lead to increased risk of displaced abomasum and decreased milk production.
The timing of early-lactation disorders is an important determinant of their impacts. Hyperketonemia (blood concentration of beta-hydroxybutyrate ≥ 1.2 mmol/L) in the first week of lactation and hypocalcemia (total calcium concentration ≤ 1.95 mmol/L) persisting to or occurring on day 4 post partum are associated with decreased milk production (1, 2) and poorer reproductive outcomes (2, 3).
In contrast, hyperketonemia occurring in the second week of lactation might not have negative reproductive and production associations (2), and hypocalcemia resolving by day 4 is associated with improved milk yield outcomes (1). Thus, the timing post partum must be considered when investigating herd problems.
Mastitis is another disease that decreases cumulative milk yield; a 335-kg loss is associated with mastitis occurring in the first 21 days (4).
Productivity losses in dairy cows resulting from subclinical disease are often considerable. The best-described relationship between subclinical disease and productivity might be the effect of subclinical mastitis on milk yield. Each 2-fold increase in SCC > 50,000 cells/mL caused a loss of 0.4 kg milk/day in primiparous cows and 0.6 kg milk/day in multiparous cows, with total lactational milk yields estimated to be decreased by 80 kg for primiparous cows and by 120 kg for multiparous cows for each 2-fold increase in the geometric mean SCC > 50,000 cells/mL (5).
These production effects have been confirmed. According to one report, cows with relatively high SCC (250,000 cells/mL) produced 1.6 kg/day less milk than di cows with low SCC (50,000 cells/mL) (6). In addition, it was shown that the duration of elevated SCC matters, because cows with chronic infections lost more milk than did cows with new infections, with daily losses rising from US $1.20 in the first month to US $2.06 per cow by the tenth month (7).
Bovine leukemia virus (BLV) infection is another subclinical disease with important economic consequences, primarily through its negative effects on milk production and animal longevity. Control strategies should be encouraged.
Diseases that delay or inhibit conception have a negative effect on dairy herd productivity by prolonging the time cows spend in lower-producing stages of lactation, by decreasing the number of offspring for replacements or for sale, and by increasing the likelihood that an animal will be culled prematurely.
Several diseases have been associated with decreased conception rates. The likelihood of conception is decreased for cows that experience retained placenta, metritis, or ovarian cysts (8, 9, 10).
The effect of disease on longevity of dairy cows has been investigated. A large proportion of cow culling is considered involuntary (necessitated by disease, injury, or death) rather than driven by low production. The premature removal of a cow from the herd decreases lifetime milk yield. Reproductive failure and mastitis are consistently recorded as the top two reasons for culling.
For More Information
Puerto MA, Shepley E, Cue RI, Warner D, Dubuc J, Vasseur E. The hidden cost of disease: II. Impact of the first incidence of lameness on production and economic indicators of primiparous dairy cows. J Dairy Sci. 2021;104(7):7944-7955.
Kuczewski A, Hogeveen H, Orsel K, et al. Economic evaluation of 4 bovine leukemia virus control strategies for Alberta dairy farms. J Dairy Sci. 2019;102(3):2578-2592.
Mann S, McArt JAA. Hyperketonemia: a marker of disease, a sign of a high-producing dairy cow, or both?Vet Clin North Am Food Anim Pract. 2023;39(3):307-324.
References
Seely CR, Leno BM, Kerwin AL, Overton TR, McArt JAA. Association of subclinical hypocalcemia dynamics with dry matter intake, milk yield, and blood minerals during the periparturient period. J Dairy Sci. 2021;104(4):4692-4702. doi:10.3168/jds.2020-19344
Rodriguez Z, Shepley E, Endres MI, Cramer G, Caixeta LS. Assessment of milk yield and composition, early reproductive performance, and herd removal in multiparous dairy cattle based on the week of diagnosis of hyperketonemia in early lactation. J Dairy Sci. 2022;105(5):4410-4420. doi:10.3168/jds.2021-20836
Seely CR, McArt JAA. The association of subclinical hypocalcemia at 4 days in milk with reproductive outcomes in multiparous Holstein cows. JDS Commun. 2023;4(2):111-115. doi:10.3168/jdsc.2022-0279
Puerto M A, Shepley E, Cue RI, Warner D, Dubuc J, Vasseur E. The hidden cost of disease: I. Impact of the first incidence of mastitis on production and economic indicators of primiparous dairy cows. J Dairy Sci. 2021;104(7):7932-7943. doi:10.3168/jds.2020-19584
Hortet P, Seegers H. Calculated milk production losses associated with elevated somatic cell counts in dairy cows: review and critical discussion. Vet Res. 1998;29(6):497-510. https://pubmed.ncbi.nlm.nih.gov/9851006
Potter TL, Arndt C, Hristov AN. Short communication: Increased somatic cell count is associated with milk loss and reduced feed efficiency in lactating dairy cows. J Dairy Sci. 2018;101(10):9510-9515. doi:10.3168/jds.2017-14062
Hadrich JC, Wolf CA, Lombard J, Dolak TM. Estimating milk yield and value losses from increased somatic cell count on US dairy farms. J Dairy Sci. 2018;101(4):3588-3596. doi:10.3168/jds.2017-13840
Giuliodori MJ, Magnasco RP, Becu-Villalobos D, Lacau-Mengido IM, Risco CA, De La Sota RL. Metritis in dairy cows: risk factors and reproductive performance. J Dairy Sci. 2013;96(6):3621-3631. doi:10.3168/jds.2012-5922
Ribeiro ES, Lima FS, Greco LF, et al. Prevalence of periparturient diseases and effects on fertility of seasonally calving grazing dairy cows supplemented with concentrates. J Dairy Sci. 2013;96(9):5682-5697. doi:10.3168/jds.2012-6335
Ribeiro ES, Gomes G, Greco LF, et al. Carryover effect of postpartum inflammatory diseases on developmental biology and fertility in lactating dairy cows. J Dairy Sci. 2016;99(3):2201-2220. doi:10.3168/jds.2015-10337
