Dados do Trabalho

Título

EFFECT OF DOUBLE PRE-MILKING TEAT DISINFECTION ON TEAT CLEANLINESS SCORE, BACTERIAL COUNT, AND MASTITIS IN PASTURE-GRAZED DAIRY COWS

Titulo em português

EFEITO DA DUPLA ANTISSEPSIA DOS TETOS PRÉ-ORDENHA NO ESCORE DE LIMPEZA DO TETO, CONTAGEM BACTERIANA E MASTITE EM VACAS LEITEIRAS A PASTO

Contribuição para a sociedade (opcional)

Teat cleanliness impacts the milk somatic cell count (SCC) and the occurrence of mastitis. The use of double pre-milking teat disinfection can be an alternative to reduce initial contamination when teats are soiled. We evaluated the use of double pre-milking teat disinfection in cows in a grazing system for its effectiveness in reducing teat skin bacterial count, SCC, and mastitis occurrence. Under environmental conditions that lead to lightly soiled teats before milking, double pre-milking teat disinfection is not required.

Introdução (obrigatório)

Environmental conditions, such as rainfall and relative humidity, are known to influence the cleanliness of teats, particularly in pasture-grazed dairy herds (MORTON et al., 2014). The teat cleanliness score and the initial level of contamination impact the effectiveness of pre-milking procedures and have consistently been associated with higher SCC and an elevated risk of subclinical udder infections (CÓRDOVA et al., 2018).
A previous study evaluating the use of double pre-milking teat disinfection in confined cows with greater soiling of teats found that double teat disinfection was more effective in cleaning the cows’ teat skin, reducing Staphylococcus spp. and total bacterial count, and reducing the total bacterial count on the milkers’ gloves compared to a single disinfection (NIERO et al., 2024).
Our objective is to compare conventional and double pre-milking teat disinfection efficacy in teat cleanliness, bacterial counts, and subclinical and clinical mastitis incidence in pasture-grazed dairy cows.

Material e métodos (obrigatório)

The experiment was conducted from November 2021 to July 2022. Sixteen cows were divided into two similar groups and randomly assigned to either conventional (CONV) or double pre-milking teat disinfection (DD). The CONV treatment involved: (1) forestripping 3 streams of milk per quarter, (2) applying a disinfectant with lactic acid and hydrogen peroxide, (3) allowing 30 seconds of contact time, and (4) drying with a paper towel. The DD treatment involved: (1) applying the disinfectant, (2) forestripping 3 streams of milk per quarter, (3) reapplying the disinfectant, (4) allowing 30 seconds of contact time, and (5) drying with a paper towel. These procedures were performed daily. The cows, under a grazing system, remained in the same environment. Every fifteen days, we evaluated the teat cleanliness score (TCS; 0 = clean to 4 = extremely dirty) and teat skin bacterial count (Figure 1) before (PRE) and after (POST) treatment. Milk samples were collected to evaluate SCC, and clinical mastitis was recorded. Based on SCC in two subsequent analyses, with a breakpoint set at 200,000 cells/mL, the cows were classified as having new, cured, chronic, or no subclinical mastitis. Meteorological data were collected on the previous day and the day of sample collection. Figure 1. Bacterial colonies of (A) Staphylococcus spp. on Baird Parker agar, (B) Streptococcus spp. on modified Edwards agar, (C) coliforms (yellow arrow) and Gram-negative non-coliforms (blue arrow) on MacConkey agar, and (D) total bacterial count on Plate Count Agar. Teat bacterial count and SCC were log10 transformed. Variance analysis with repeated measures using the MIXED procedure was applied to teat bacterial count, TCS, and SCC. Statistical differences were defined at the 5% level.

Resultados e discussão (obrigatório)

The results of TCS and bacterial count are presented on Table 1. Table 1. Mean ± standard deviations (SD) for teat cleanliness score (TCS), teat bacterial count before (PRE) and after (POST) treatment for conventional premilking teat disinfection (CONV) and double premilking teat disinfection (DD) treatments. Variables N Treatment P-value CONV SD DD SD TCS_PRE 277 2.13 0.12 2.16 0.12 0.84 TCS_POST 277 1.00 0.08 0.92 0.09 0.41 Dif_TCS 277 -1.11 0.08 -1.25 0.10 0.18 Teat bacterial count1             CCOL_PRE 160 3.25 0.15 3.21 0.17 0.86 CCOL_POST 160 1.10 0.19 0.67 0.22 0.08 Dif_CCOL 160 -2.14 0.21 -2.51 0.24 0.16 GNNCOLC_PRE 194 3.56 0.13 3.59 0.15 0.85 GNNCOLC_POST 194 1.32 0.18 1.21 0.21 0.67 Dif_GNNCOLC 194 -2.22 0.15 -2.36 0.18 0.52 STEC_PRE 254 3.23 0.17 3.34 0.15 0.56 STEC_POST 254 1.27 0.18 1.15 0.22 0.59 Dif_STEC 254 -1.87 0.14 -2.06 0.17 0.32 STAC_PRE 257 4.22 0.17 4.27 0.19 0.76 STAC_POST 257 2.95 0.22 3.18 0.25 0.40 Dif_STAC 257 -1.12 0.13 -1.23 0.15 0.52 TBC_PRE 269 4.70 0.13 4.90 0.14 0.18 TBC_POST 269 3.72 0.10 3.75 0.12 0.79 Dif_TBC 269 -0.92 0.11 -1.12 0.13 0.15 1Colony-forming units/mL log10; COLC: Coliforms count; GNNCOLC: Gram-negative non-coliform count; STEC: Streptococcus spp. count; STAC: Staphylococcus spp. count; TBC: Total bacterial count; Dif: Difference between PRE and POST. The mean SCC was 5.21±0.14 for CONV and 5.36±0.14 for DD, with no significant difference between treatments. The incidence of new, cured, chronic, and no subclinical mastitis, and clinical mastitis did not differ between treatments. Precipitation was low during the experimental period, with only three collection days exceeding 10 mm. The lower rainfall likely contributed to cleaner teats (MORTON et al., 2014), which may have minimized differences between treatments in bacterial count, SCC, and mastitis occurrence. Our results differed from those of NIERO et al. (2024), who observed a greater reduction TCS with DD, but their study had a higher TCS PRE (mean 3.35±0.64).

Conclusão (obrigatório)

We conclude that under conditions leading to lightly soiled teats, double pre-milking teat disinfection does not significantly reduce TCS, bacterial count, SCC, or clinical mastitis incidence compared to conventional treatment.

Referências bibliográficas (opcional)

CÓRDOVA, H. A. et al. Influência da profundidade do úbere na limpeza dos tetos e na saúde da glândula mamária em ordenha robótica. Arquivo Brasileiro de Medicina Veterinária e Zootecnia, v. 70, n. 5, p. 1443–1452, 2018.
MORTON, J. M. et al. Premilking teat disinfection: Is it worthwhile in pasture-grazed dairy herds? Journal of Dairy Science, v. 97, n. 12, p. 7525–7537, 2014.
NIERO, T. R. et al. Effect of double-premilking teat disinfection protocols on bacterial counts on teat skin of cows and milker gloves in a free-stall-housed dairy herd. Journal of Dairy Research, p. 8–11, 2024.