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Somatic cell counts, mastitis infection prevalence, and mastitis pathogen distribution in compost bedded pack and sand freestall farms
The objective of this research was to describe the relationships among SCC, mastitis infection prevalence (MIP, percent of cows with SCS>3.9), and mastitis pathogen distribution (MPD) in 8 compost bedded pack (CB) and 7 sand freestall (SF) farms in Kentucky from May 2013 to January 2014. The same observer evaluated cow hygiene scores (HYS, Cook and Reinemann, 2007) bi-weekly for 50 cows per herd. Throughout the study, producers collected aseptic milk samples from all quarters displaying clinical mastitis signs for bacteriological culturing. Test-day SCC and MIP were obtained from DHIA. The MIXED procedure of SAS (SAS Institute, Inc., Cary, NC) was used to assess fixed effects of barn type (BT), maximum ambient temperature (MT), and HYS on SCC and MIP. Stepwise backward elimination removed non-significant interactions (P≥0.05) with main effects remaining in the model regardless of significance. A χ2 analysis was conducted using the FREQ procedure of SAS to determine MPD between BT. Maximum ambient temperature, BT, and MT×BT were significant predictors of MIP (P<0.05). As MT increased, MIP increased more rapidly in CB than in SF (P<0.05). Calculated MIP LSMeans(±SE) for CB and SF herds were 30.67 ± 3.02% and 25.33 ± 3.12%, respectively (P<0.05). Hygiene score and BT×MT were significant predictors of SCC (P<0.05). With increasing MT, herd SCC increased more rapidly in CB than in SF (P<0.05). Somatic cell count LSMeans(±SE) for CB and SF were 255,700 ± 24,269 cells/mL and 223,520 ± 25,163 cells/mL, respectively (P≥0.05). Table 1 summarizes MPD frequency by BT. Results of this study demonstrate potential challenges for managing mastitis in CBP.
Table 1. Frequencies of pathogens isolated from clinical mastitis cases in compost bedded pack (CB) barns and sand freestall (SF) barns1,2
Pathogen isolated1 |
CB2 (Total number of cases = 219) (Mean number of cows = 1208) |
SF2 (Total number of cases = 109) (Mean number of cows = 629) |
Coagulase negative staphylococci |
16(7%) |
4(4%) |
Environmental streptococci |
32(15%) |
21(19%) |
Escherichia coli |
63(29%) |
19(17%) |
Gram-positive Bacillus species |
4(2%) |
1(1%) |
Staphylococcus aureus |
7(3%) |
6(6%) |
Yeast species |
5(2%) |
2(2%) |
Klebsiella species |
4(2%) |
4(4%) |
Other gram-negative species |
28(13%) |
14(13%) |
Other gram-positive species |
6(3%) |
8(7%) |
No growth |
32(15%) |
20(18%) |
Contaminated samples |
20(9%) |
8(7%) |
Missing samples |
2(1%) |
2(2%) |
1Number of pathogens isolated per species (percent of total samples per barn type).
2 χ2 analysis indicated no significant differences for mastitis pathogen distribution between barn types (P≥0.05).
Keywords: mastitis, sand freestall barn, compost bedded pack barn