Cow-related risk factors for milk leakage.
ABSTRACT Milk leakage in dairy cows is a symptom of impaired teat sphincter function. Milk leakage is related to an increased risk of mastitis in heifers and cows, and causes hygiene problems. The aim of our study was to assess whether teat shape, condition of teat orifice, and peak milk flow rate are risk factors for milk leakage. We conducted a longitudinal observational study in 15 German dairy farms in which cows were maintained in loose housing. The farms were visited monthly at 2 consecutive milkings. During the evening milking, milk flow curves were measured with the LactoCorder. Milk leakage was recorded during the subsequent morning milking, when cows entered the milking parlor. Immediately after detachment of the milking cluster, teat shape, teat end shape, and condition of the teat orifice of cows were assessed between 9 and 100 d in milk (DIM) and during late lactation (>250 DIM). Data from 1600 cows were analyzed. Milk leakage was treated as the binary response variable in a logistic regression model with herd as a random effect. Primiparous cows with high peak milk flow and teat canal protrusion were at greater risk of milk leakage. High peak milk flow rate, short teats, teat canal protrusion, inverted teat ends, and early lactation increased the risk of milk leakage in multiparous cows. Random herd effects accounted for only 10% of the total variation, indicating that the impact of management or other herd-level factors on the occurrence of milk leakage is virtually negligible for practical purposes.
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ABSTRACT: Mastitis is one of the most important diseases in dairy cattle. Recently, the so-called minor pathogens, of which coagulase-negative staphylococci (CNS) are the most important group of bacteria, has received more attention. This thesis focuses on the role of CNS in udder health of dairy cows. The relevance of CNS is studied in a prevalence study of 49 Dutch dairy herds. Coagulase-negative staphylococci were the most frequently isolated group of bacteria (11% of quarters) and were found in all herds. Control programs such as the “five-point program” seem to be less effective to reduce the prevalence of CNS intramammary infection (IMI). The prevalence of CNS IMI was associated with environmental herd level variables such as source of drinking water not being tap water, housing of dry cows in one group instead of multiple groups, pasturing during the outdoor season, and proportion of stalls contaminated with milk. Identification of CNS at the species level in service laboratories is generally carried out using phenotypic tests. The accuracy of two phenotypic tests, API Staph ID 32 and Staph-Zym, was determined in comparison with identification based on DNA-sequencing. A total of 172 CNS isolates from bovine milk samples were classified into 17 species. The API Staph ID 32 correctly identified 41% and he Staph-Zym 31% of the CNS isolates. Both phenotypic tests were unsuitable for identification of CNS species from bovine milk samples. The effect of CNS on somatic cell count (SCC) of quarter, cow and bulk milk was studied. Quarters with a CNS IMI had a lower SCC than quarters with a major pathogen IMI but a higher SCC than culture-negative quarters. This was also found for composite SCC. Cow-level prevalence of CNS IMI was higher in dairy farms with a BMSCC <150,000 cells/ml than in dairy farms with a medium or high BMSCC, 30, 19 and 18%, respectively. Mastitis quarters infected with CNS sometimes need to be treated. Therefore, the susceptibility was analyzed of 170 CNS isolates. Forty percent of the CNS isolates was phenotypically pansusceptible. In additional to phenotypical resistance, also genotypic resistance was studied with emphasis on blaZ, mecA, ermC and lnuA genes. In 9% of the isolates no resistance genes were found, while blaZ was found in 80% of the CNS isolates and was the most frequently isolated gene in this study. A high percentage of heifers is infected with major pathogens or CNS at calving. 184 heifers on 13 Dutch dairy farms were treated with dry cow antibiotic treatment 8 to 10 weeks before the expected calving date. Another 185 heifers in these herds served as untreated controls. Coagulase-negative staphylococci were the most frequently isolated species in milk samples collected at calving in both groups. Treatment of heifers before calving resulted in a lower prevalence of major and minor pathogens after calving, a lower risk of clinical mastitis, a lower Dairy Herd Improvement test-day SCC and a higher test-day milk production.
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ABSTRACT: Mastitis is a widely occurring and costly disease in the dairy industry. Th e aim of this study was to isolate bacterial causes of subclinical mastitis and investigate the relationship between subclinical mastitis and teat condition in dairy herds located around Shiraz, Fars province, Iran. From 7 commercial dairy herds around Shiraz 354 lactating cows were selected randomly. Subclinical mastitis was evaluated by the California Mastitis Test (CMT), electrical conductivity (EC), and somatic cell count (SCC). Teat condition was evaluated by measuring teat width and length. In the 68 samples of bacterial cultures identifi ed, 14 diff erent bacterial species were found. Staphylococcus aureus and Streptococcus agalactiae were the most common isolates with 19 (27.94%) and 14 (20.59%), respectively. Th ere were no signifi cant diff erences between the width and length of the 4 teats in diff erent CMT reactions. Th ere was, however, signifi cant correlation between CMT reaction and teat width (r = 0.14 to 0.20). In addition, there was signifi cant correlation between SCC and teat injuries (r = 0.13). Th e diff erence between number of SCC in CMT positive and negative cows, as well as EC positive and negative cows, was signifi cant. It is concluded that some anatomical characteristics of the teat can aff ect the udder's susceptibility to mastitis. Th erefore, bull selection programs may be targeted to improve mastitis control in dairy cow farms.