Objective—To determine whether bulk-tank standard
plate counts or plate loop counts and bulk-tank
somatic cell counts (SCC) were associated with
detection of violative antimicrobial residues in milk
from dairy cattle.
Procedure—Information for 1994 through 1997 was
obtained from a large milk marketing cooperative that
operated in multiple states throughout the northeastern
and midwestern United States (16,831 herd-years
of information from 6,546 farms) and from the Ohio
Department of Agriculture Grade-A Milk Certification
Program (12,042 herd-years of information from 4,022
farms). Data were analyzed by use of multivariate
Results—For both data sets, odds that a violative
antibiotic residue would be detected increased as
mean SCC for the herd-year increased. Standard plate
counts and plate loop counts were not associated
with odds that a violative antibiotic residue would be
Conclusions and Clinical Relevance—Results of
this study suggested that the odds that a violative
antibiotic residue would be found in bulk-tank milk
increased as mean SCC for the herd-year increased.
This suggests that management practices that would
be expected to influence SCC may also influence the
risk of antibiotic residue violations. (J Am Vet Med
Objective—To identify herd characteristics and management
practices associated with bulk-tank somatic
cell counts (BTSCC) in dairy herds in Ohio enrolled in
official Dairy Herd Improvement Association (DHIA)
Sample Population—186 dairies in Ohio.
Procedure—All herds in official DHIA programs in 9
counties were asked to participate. Extensive information
regarding herd characteristics and management
practices was obtained, using a standardized
questionnaire. Bulk-tank milk samples were requested
from all participating herds for bacterial culture.
Official DHIA test-day records for January 1997 were
obtained from all herds enrolled in official DHIA programs
in the 9 counties. Potential associations were
identified, using multivariable ANOVA.
Results—Participation was 186 of 479 (39%) herds.
Streptococcus agalactiae and Mycoplasma spp were
not isolated from bulk-tank milk samples.
Staphylococcus aureus was isolated from 64 of 172
(37%) of the herds. The BTSCC were inversely associated
with peak daily milk production, postmilking teat
disinfection, percentage of eligible cows in the herd
detected in estrus, and directly related to the extent to
which BTSCC was perceived as a herd problem during
the preceding 2 years. Type of housing for nonlactating
cows and product used for treatment of nonlactating
cows also were significantly associated with BTSCC.
Conclusions and Clinical Relevance—Consideration
of herd characteristics and implementation of management
practices associated with BTSCC could result in
increased milk yield and production of milk with lower
BTSCC. (Am J Vet Res 2000;61:1092–1098)
Objective—To provide an updated evaluation of the efficacy and safety of sometribove zinc suspension (rbST-Zn), a form of recombinant bovine somatotropin, in lactating dairy cows.
Sample—26 studies published in peer-reviewed journals or reviewed by a regulatory agency.
Procedures—To be included, a study had to involve the use of the rbST-Zn formulation available to US producers in accordance with the label instructions for treatment initiation (57 to 70 days postpartum), dose (500 mg, q 14 d), and route (SC).
Results—For cows treated with rbST-Zn, mean milk, 3.5% fat-corrected milk, fat, and protein yields were increased by 4.00, 4.04, 0.144, and 0.137 kg/d (8.8, 8.89, 0.32, and 0.30 lb/d), respectively; however, the concentration of milk components did not change. Pregnancy proportion for the first 2 breeding cycles was increased by 5.4%, and pregnancy proportion for the duration of the trial was reduced by 5.5% for rbST-Zn–treated cows, compared with proportions for untreated cows. Mean body condition score (1 to 5 scale) was reduced by 0.06 points during the period of rbST-Zn use for treated cows. Administration of rbST-Zn had no effect on milk somatic cell count, the number of days to pregnancy, or inseminations per pregnancy; rates of fetal loss, twins, cystic ovaries, clinical lameness, lameness lesions, or traumatic lesions of the integumentary system; and odds of clinical mastitis or culling.
Conclusions and Clinical Relevance—Results indicated that rbST-Zn administration to dairy cows effectively increases milk production with no adverse effects on cow health and well-being.