Extended ceftiofur therapy for treatment of experimentally-induced Streptococcus uberis mastitis in lactating dairy cattle.

Streptococcus uberis is an important cause of mastitis in dairy cows throughout the world, particularly during the dry period, the period around calving, and during early lactation. Strategies for controlling Strep. uberis mastitis are poorly defined and are currently inadequate. Objectives of the present study were to evaluate efficacy of ceftiofur, a new broad-spectrum cephalosporin antibiotic, for treatment of experimentally induced Strep. uberis intramammary infections (IMI) in lactating dairy cows during early lactation and to determine whether extended therapy regimens enhanced efficacy of ceftiofur. Efficacy of extended ceftiofur intramammary therapy regimens was investigated in 37 mammary quarters of 23 dairy cows that developed clinical mastitis following experimental infection with Strep. uberis during early lactation. Cows that developed clinical mastitis during the challenge period were allocated randomly to 3 groups representing 3 different ceftiofur treatment regimens: 2-d (n = 7 mammary quarters), 5-d (n = 16 mammary quarters), and 8-d (n = 14 mammary quarters) treatment regimens. For all groups, 125 mg of ceftiofur hydrochloride was administered via intramammary infusion. A bacteriological cure was defined as an experimentally infected quarter that was treated and was bacteriologically negative for the presence of Strep. uberis at 7, 14, 21, and 28 d posttreatment. Percentage of Strep. uberis IMI eliminated was 43, 88, and 100% for the 2-, 5-, and 8-d ceftiofur treatment regimens, respectively. Both the 5- and 8-d ceftiofur extended therapy treatment regimens had significantly higher bacterial cure rates than the standard 2-d ceftiofur treatment regimen. The bacterial cure rate of the 8-d ceftiofur extended therapy group was marginally better (P = 0.052) than the 5-d ceftiofur extended therapy group. Results of this study indicate that ceftiofur therapy was effective for eliminating Strep. uberis experimental IMI, and 5- and 8-d extended ceftiofur therapy regimens were more effective than the standard 2-d treatment.

Influence of prepartum pirlimycin hydrochloride or penicillin-novobiocin therapy on mastitis in heifers during early lactation.

A study was conducted in 2 dairy research herds to determine whether prepartum therapy of heifer mammary glands with penicillin-novobiocin or pirlimycin hydrochloride was effective for reducing the percentage of heifers and mammary quarters infected with mastitis pathogens during early lactation. Almost 96% of Jersey heifers (67 of 70) and 71.3% of quarters (199 of 279) were infected 14 d before expected calving. Of the quarters infected at 14 d before expected parturition, 75% (54 of 72) were uninfected following treatment with penicillin-novobiocin; 87% (61 of 70) were uninfected following treatment with pirlimycin, and 56% (32 of 57) were uninfected in the untreated negative control group. The majority of intramammary infections in Jersey heifers were due to coagulase-negative staphylococci (61%), Streptococcus species, primarily Streptococcus uberis (19%), and Staphylococcus aureus (8%). Almost 73% of Holstein heifers (40 of 55) and 34.3% of mammary quarters (73 of 213) were infected 14 d before expected calving. Of the quarters infected at 14 d before expected parturition, 76% (19 of 25) were uninfected following treatment with penicillin-novobiocin; 59% (17 of 29) were uninfected following treatment with pirlimycin, and 26% (5 of 19) were uninfected in the untreated negative control group. The majority of intramammary infections in Holstein heifers were due to coagulase-negative staphylococci (44%) and Staph. aureus (30%). In both herds, the bacteriological cure rate was significantly higher in heifer mammary glands treated with penicillin-novobiocin or pirlimycin hydrochloride than in untreated controls. Prepartum therapy of heifer mammary glands with penicillin-novobiocin or pirlimycin hydrochloride significantly reduced the percentage of heifers and quarters infected with mastitis pathogens during early lactation.

Efficacy of extended ceftiofur intramammary therapy for treatment of subclinical mastitis in lactating dairy cows.

Little research has focused on treatment of cows with subclinical mastitis during lactation. Ceftiofur is a new broad-spectrum, third-generation cephalosporin antibiotic for veterinary use that inhibits bacterial cell wall synthesis by interfering with enzymes essential for peptidoglycan synthesis. Ceftiofur should be effective against a wide range of contagious and environmental mastitis pathogens. Objectives of the present study were to evaluate the efficacy of ceftiofur for treatment of subclinical mastitis in lactating dairy cows, and to determine if extended therapy regimens enhanced efficacy of ceftiofur. Holstein and Jersey dairy cows (n = 88) from 3 dairy research herds were used. Cows were enrolled in the study based on milk somatic cell counts >400,000/mL and isolation of the same mastitis pathogen in 2 samples obtained 1 wk apart. Cows with one or more intramammary infections (IMI) were blocked by parity and DIM and allocated randomly to 1 of 3 different ceftiofur treatment regimens: 2-d (n = 49 IMI), 5-d (n = 41 IMI), and 8-d (n = 38 IMI) treatment regimens. For all groups, 125 mg of ceftiofur hydrochloride was administered via intramammary infusion. Eighteen cows with 38 IMI were included as an untreated negative control group. A bacteriological cure was defined as a treated infected mammary quarter that was bacteriologically negative for the presence of previously identified bacteria at 14 and 28 d after the last treatment. Efficacy of ceftiofur therapy against all subclinical IMI was 38.8, 53.7, and 65.8% for the 2-, 5-, and 8-d ceftiofur treatment regimens, respectively. Four of 38 (10.5%) IMI in control cows were cured spontaneously without treatment. All 3 ceftiofur treatment regimens were significantly better than the negative control, and the 8-d extended ceftiofur treatment regimen treatment group was significantly better than the standard 2-d treatment group. Pathogen groups had significantly different cure rates from one another. The cure rate for the 8-d extended ceftiofur treatment regimen was 70% for Corynebacterium bovis, 86% for coagulase-negative Staphylococcus species, 36% for Staph. aureus, 80% for Streptococcus dysgalactiae ssp. dysgalactiae, and 67% for Strep. uberis.

Efficacy of a new premilking teat disinfectant containing a phenolic combination for the prevention of mastitis.

A teat disinfectant containing a phenolic combination was evaluated in a natural exposure study in two dairy research herds. Premilking teat disinfection was compared with a negative control using a split-udder experimental design. In both herds, premilking and postmilking teat disinfections with the phenolic combination were significantly more effective in preventing new intramammary infection (IMI) than was postmilking teat disinfection only. Clinical mastitis and new IMI by Streptococcus uberis, Streptococcus dysgalactiae, Gram-negative pathogens, and coagulase-negative Staphylococcus species were significantly lower in quarters of cows with teats predipped and postdipped than in quarters with teats postdipped only. No chapping or teat skin irritation was observed. Premilking teat disinfection with the phenolic combination in association with good udder preparation and postmilking teat disinfection can further reduce the occurrence of new IMI by numerous mastitis pathogens during lactation.

The effect of artificial insemination once versus twice per day.

The objective of this study was to determine the effect of inseminating Jersey cows and heifers once per day or according to the a.m.-p.m. rule. A total of 337 artificial inseminations (AI) were completed by three technicians at the University of Tennessee Dairy Experiment Station at Lewisburg for 6 mo. Cows and heifers were inseminated at estrus using the a.m.-p.m. rule on even days of the month. On odd days of the month, AI were once daily between 0800 and 1200 h. Estrus detection was conducted two to three times daily. Pregnancy was confirmed by rectal palpation 60 to 80 d after AI. Herd DHIA averages were a 12.2-mo calving interval, 76 d to first AI, 83% observed estruses, and a 50% conception rate during the trial. Pregnancy data were analyzed with a model including treatment, AI, lactation number, parity, technician, and group. This study grouped cows and heifers according to when they were in estrus and inseminated (a.m.-a.m., a.m.-p.m., or p.m.-a.m.); means were 43.7, 57.9, and 59.0%, respectively. The a.m.-p.m. AI versus once per day AI yielded a pregnancy rate of 55.6% versus 51.3%. These results show no difference among Jersey cows or heifers that were inseminated artificially once daily in the a.m. However, those cows and heifers inseminated in the a.m. of first estrus detection had a lower pregnancy rate.

Supplemental niacin and heat-treated whole soybeans for Jersey cows during early lactation.

Fifty-six multiparous Jersey cows were used in a replicated trial to investigate the effect of supplemental niacin and heat-treated whole soybeans on milk production and composition. Dietary treatments included 0 or 6 g/d of supplemental niacin beginning 21 d prior to expected parturition and raw or heat-treated whole soybeans fed at 10% of the dietary DM beginning immediately after parturition. Data were collected for 18 wk following a 2-wk postpartum period during which cows were adjusted to experimental diets and allowed to recover from parturition. Based on index values for protein dispersibility, heat-treated soybeans were marginally heated in yr 1 (12.1) and underheated in yr 2 (17.9). Intake of DM from corn silage plus concentrate, alfalfa hay, or soybeans averaged 15.5, 1.5, and 1.7 kg/d, respectively, and was not different because of niacin supplementation or form of soybean. Percentage of milk fat was highest when raw soybeans plus niacin were fed and lowest for heat-treated soybeans plus niacin. No difference was observed in milk production, milk percentage, or milk protein, lactose, and SNF. No advantage was observed from less than optimally heated whole soybeans or supplemental niacin in diets for Jersey cows during early lactation.

Addition of soybean trypsin inhibitor to bovine colostrum: effects on serum immunoglobulin concentrations in Jersey calves.

Secretion of trypsin by the neonate may reduce absorption of Ig from colostrum and increase failure of transfer of passive immunity, particularly for calves fed after 12 h of age. Jersey calves (n = 48) were used in a 2 x 2 factorial arrangement of soybean trypsin inhibitor (0 or 1 g) added to 1 L of maternal colostrum at the first two feedings and time of initial feeding (.65 or 12 h of age). A second colostrum feeding was offered 12 h after the initial feeding. Maternal colostrum was analyzed for Ig by radial immunodiffusion and trypsin inhibitor by radial protease diffusion. Jugular blood was sampled at 0, 12, 24, and 48 h after initial feeding, and serum was analyzed for IgG and IgM. Addition of trypsin inhibitor increased serum Ig and total serum protein concentrations, regardless of age at first feeding. Concentrations of serum IgG and IgM were increased 16 and 30%, respectively, when trypsin inhibitor was fed. Age of first feeding did not affect concentrations of IgG or IgM in serum. Supplementation of colostrum with trypsin inhibitor improved transfer of passive immunity to neonatal Jersey calves.

Effects of housing and colostrum feeding on serum immunoglobulins, growth, and fecal scores of Jersey calves.

Ninety-six Jersey calves were used to evaluate the effects of housing and method of colostrum feeding on serum Ig concentrations, incidence and severity of scours, intake, and BW changes from birth to 35 d of age. Calves were separated from the dam and fed 2 L of colostrum in nipple-bottles or allowed to nurse the dam for 3 d. Calves were housed in individual hutches or wooden pens in a barn. Intake of colostrum by calves allowed to nurse the dam was not controlled. Serum IgG and IgM concentrations at 24 h of age were greater for calves that nursed the dam. Scours were less severe when calves were housed in hutches, but number of days scouring was unaffected by treatment. Calves fed colostrum in nipple-bottles and housed in the barn consumed more starter than did other calves from 3 to 5 wk of age. The BW were greater for calves allowed to nurse the dam and housed in hutches. Feed efficiency over the 35-d study was improved when calves nursed the dam. Optimal transfer of passive immunity and housing in hutches appeared to maximize health and growth in this study.

Effects of housing and colostrum feeding on the prevalence of selected infectious organisms in feces of Jersey calves.

Neonatal Jersey calves (n = 96) were used to evaluate effects of housing (individual hutches or wooden pens in a barn) and colostrum feeding (calves were separated from the dam and fed 2 L of colostrum in nipple-bottles or allowed to nurse the dam for 3 d) on the prevalence of selected organisms in feces. Prevalence of Cryptosporidium and Eimeria were reduced, and prevalence of rotavirus tended to be reduced, when calves were housed in hutches. Prevalence of coronavirus was unaffected by treatment. Weekly prevalence of Giardia was increased when calves were left to nurse the dam for 3 d. Mean prevalence of Cryptosporidia (wk 1 to 4), Eimeria (wk 4 to 5), Giardia, rotavirus, and coronavirus (wk 1 to 5) were 34.7, 20.6, 27.1, 15.8, and 4.9%, respectively. Escherichia coli (K99 positive) were observed in 3 of 174 samples cultured. Methods of housing and colostrum feeding affected acquisition of enteropathogens in this study.