Production loss due to new subclinical mastitis in Dutch dairy cows estimated with a test-day model

Abstract

Milk, fat, and protein loss due to a new subclinical mastitis case may be economically important, and the objective of this study was to estimate this loss. The loss was estimated based on test-day (TD) cow records collected over a 1-yr period from 400 randomly selected Dutch dairy herds. After exclusion of records from cows with clinical mastitis, the data set comprised 251,647 TD records from 43,462 lactations of 39,512 cows. The analysis was carried out using a random regression test-day modeling approach that predicts the cow production at each TD based on the actual production at all previous TD. The definition of new subclinical mastitis was based on the literature and assumed a new subclinical case if somatic cell count (SCC) was >100,000 cells/mL after a TD with SCC <50,000 cells/mL. A second data set was created by applying an adjustment to correct low SCC for the dilution effect when determining if the previous test-day SCC was <50,000 cells/ mL. Thereafter, the loss was estimated for records with SCC >100,000 cells/mL. The production (milk, fat, or protein) losses were modeled as the difference between the actual and predicted production (milk, fat, or protein) at the TD of new subclinical mastitis, for 4,382 cow records, and 2,545 cow records after dilution correction. Primiparous cows were predicted to lose 0.31 (0.25-0.37) and 0.28 (0.20-0.35) kg of milk/d at an SCC of 200,000 cells/mL, for unadjusted and adjusted low SCC, respectively. For the same SCC increase, multiparous cows were predicted to lose 0.58 (0.54-0.62) and 0.50 (0.44-0.56) kg of milk/d, respectively. Moreover, it was found that the greater the SCC increase above 100,000 cells/mL, the greater the production losses. The estimated production losses were more precise than previously reported estimates.

Mediation analysis to estimate direct and indirect milk losses associated with bacterial load in bovine subclinical mammary infections

“…Total losses in test-day milk yield were estimated at 7.1 kg (for the average CFU in 'unP' cows). Halasa et al (2009) reported a loss of 0.31 kg in primiparous (and 0.58 kg in multiparous) cows for which SCC was >100 000 cells/ml after a test day with SCC <50 000 cells/ml, that is, suspected to suffer from a new subclinical mastitis.…”

A new somatic cell count index to more accurately predict milk yield losses

“…Only a few studies proposed the existence of the dilution effect from increased milk yield on the SCC (at the level of 200 000) in cows without IMI. High-milk-yielding cows without IMI have been thought to exhibit lower SCC than low-milk-yielding cows (Miller et al, 1993;Green et al, 2006;Halasa et al, 2009). Dilution-adjusted SCC values fitted the data better and resulted in a slightly reduced milk loss compared to the unadjusted SCC (Green et al, 2006).…”

“…The estimated SCCs of high-yielding dairy cows without IMI were found to be lower than those of low-yielding dairy cows (Green et al, 2006;Halasa et al, 2009;Boland et al, 2013). If the SCC concentration due to lower milk production in infected cows is neglected, the milk production loss might be overestimated.…”

“…In addition, we excluded the data for all cows in which the SCC between two consecutive milk recordings increased from less than 50 000 to more than 100 000. These numbers potentially indicate a suspected case of subclinical mastitis (Halasa et al, 2009). We also excluded data for which the sum of squared deviations at fitting of lactation curves through TDMY in MY305 according to the MilkBot model (Cole et al, 2012) was larger than 150 kg, which represents > 0.5 kg milk per production day.…”

“…mastitis. A new definition of subclinical mastitis assumed a new case if the SCC reached > 100 000 after a test day when the SCC was < 50 000 (Halasa et al, 2009). Therefore, the selection of an appropriate threshold for defining a noninfected udder depends on the purpose.…”