Calf birth weight and its association with calf and cow survivability, disease incidence, reproductive performance, and milk production.

The hypothesis was that calf birth weight (CBW) and a cow calf index [CCI; (calf weight/cow height at parturition) x 100] would be associated with calf and cow survivability, disease incidence, reproductive performance, and milk production. Data were collected in a prospective cohort study from one commercial dairy milking 2,800 Holsteins in upstate NY from March 2007 to August 2007. Animals were enrolled at parturition until 1,245 calvings were available for analysis. Data consisted of on-farm measurements of morbidity, mortality, and performance, and data were analyzed using a series of multivariable models including ANOVA and time-to-event analysis. A higher CBW and a higher CCI were associated with greater odds of lameness. Compared with the lowest quartile of CBW, the odds of the dam becoming subsequently lame increased as the CBW quartiles increased from 2 to 4; odds ratio = 1.5, 2.7, 3.6, respectively. Compared with the lowest quartile of CCI, the odds of the dam becoming subsequently lame increased as the CCI quartiles increased from 2 to 4; odds ratio = 4.6, 4.7, 4.8, respectively. Assistance during parturition was associated with higher CBW and with higher CCI. Calves born from assisted parturition had significantly higher CBW (CBW = 43.7 kg) and CCI (CCI = 31.4) compared with calves born from nonassisted parturition (CBW = 41.5 kg and CCI = 29.7). Neither CBW nor the CCI were associated with stillbirth incidence, calf mortality past 12 h of life, cow reproduction, or cow survival. We concluded that CBW, and especially the ratio of CBW to dam size, can be associated with some downstream effects, e.g., obstetrical assistance, lameness events, and milk production.

Effect of nitazoxanide on cryptosporidiosis in experimentally infected neonatal dairy calves.

Cryptosporidium is a zoonotic protozoan that is most often diagnosed in association with diarrhea in 1- to 3-wk-old dairy calves. There are neither consistently effective nor approved antimicrobial drugs for treatment in animals. The objective of this study was to test nitazoxanide (NTZ) as a treatment for cryptosporidiosis in experimentally infected dairy calves. A randomized, controlled, and blinded trial was performed using Holstein bull calves obtained from a large commercial dairy. All births were attended by study personnel and calves were fed 4 L of heat-treated colostrum within 1 h of birth. Calves were randomly assigned to treatment or placebo group and maintained for a 32-feeding (16 d) study period. Twenty-three calves were enrolled with 3 lost to follow up. Thirteen calves were assigned to the treatment group and 7 calves to the placebo group. All calves were inoculated with 1 x 10(6) viable Cryptosporidium parvum oocysts at feeding 3. Treatment was a commercially available NTZ product and the placebo was the carrier of the same product. Nitazoxanide was administered at 1.5 g twice per day for 5 d. Nitazoxanide or placebo treatment began after feeding 10 and when the fecal score was greater than 1 out of 3. Outcome measurements included twice-daily fecal and health scores and a once-daily oocyst count by an immunofluorescent antibody assay. Data were analyzed by nonparametric and time-to-event methods. Measures of passive transfer of antibodies, initial body weight, and onset of oocyst shedding were not different between treatment and control calves. Eighty-five percent of the NTZ-treated calves stopped shedding oocysts by the end of the observation period whereas only 15% of the placebo group stopped shedding. The median number of feedings with a fecal score equal to 3 was 2 in the NTZ group while it was 6 in the placebo group. Calves receiving NTZ were 0.13 times as likely to have severe and sustained diarrhea than control calves (95% confidence interval, 0.02-0.98). Treating calves with NTZ reduced the duration of oocyst shedding and improved fecal consistency.

Antibody responses following administration of a Cryptosporidium parvum rCP15/60 vaccine to pregnant cattle.

Cryptosporidium parvum is a zoonotic Apicomplexa-protozoan pathogen that causes gastroenteritis and diarrhea in mammals worldwide. Globally, C. parvum is ubiquitous on dairy operations and is the pathogen most commonly diagnosed in association with calf diarrhea. Here, we describe the antibody response in 20 pregnant cows to a recombinant C. parvum oocyst surface protein (rCP15/60) vaccine compared with 20 controls, and the antibody response in 19 calves fed the rCP15/60-immune colostrum from these vaccinated cows compared with 20 control calves. Cows vaccinated with rCP15/60 produced a significantly greater antibody response compared to controls (p<0.0001) and this response was strongly associated with the subsequent level of colostral antibody (r=0.82, p<0.0001). Calves fed rCP15/60-immune colostrum showed a dose-dependent absorption of antibody, also associated with colostral antibody levels (r=0.83, p<0.0001). Currently, drug therapy against cryptosporidiosis is limited making development of an effective vaccine attractive. This report describes the first stages in development of a C. parvum rCP15/60 vaccine designed to confer passive protection to calves against cryptosporidiosis.