Serologic evaluation of cattle inoculated with Toxoplasma gondii: comparison of Sabin-Feldman dye test and other agglutination tests

Six cows and 6 calves were each inoculated with 100 or 100,000 Toxoplasma gondii oocysts. Serum samples were analyzed, using the Sabin-Feldman dye test (DT), indirect hemagglutination test, latex agglutination test, and the modified direct agglutination test (MAT). Antibody titers in cows were lower than in calves. In the cows, DT titers increased briefly during the first month after inoculation, after which the titers were negative; however, T gondii was isolated from the tissues of 4 cows. Indirect hemagglutination and latex agglutination titers were generally less than 1:256. The MAT titers increased to 1:1,024 during the first month after inoculation. In 5 of the 6 cows, the MAT titers persisted. The 6th cow had a preinoculation MAT titer of 1:2,000 for 3 to 6 months. Therefore, the DT was not useful in serologic surveys for T gondii in cattle; the MAT was the most sensitive test and may be useful in the diagnosis of T gondii infection in cattle.     

Leptospirosis in beef herds from western Canada: serum antibody titers and vaccination practices

One study described the frequency of pre-breeding vaccination for leptospirosis in 205 cow-calf herds from across western Canada and the prevalence of positive Leptospira antibody titers in unvaccinated, weaned calves from 61 of these herds. The percentages of herds vaccinated for leptospirosis were 13.7% in 2001 and 8.4% in 2002. Of 1539 calves examined, 13 (0.8%) had a positive antibody titer for a Leptospira serovar; the most common serovar detected was hardjo. A second study examined the prevalence of positive Leptospira antibody titers during the summer grazing season in 313 vaccinated and 478 unvaccinated cows from 40 cow-calf herds in southern Saskatchewan. Antibody titers for 7 Leptospira serovars were measured during the grazing season. Of the non-vaccinated cows, 9.6% were positive in the spring for serovar pomona, 6.7% for serovar grippotyphosa, and 6.1% for serovar icterohaemorrhagiae; the corresponding percentages for the fall were 5.5%, 3.0%, and 1.3%, respectively. Of 781 vaccinated and unvaccinated cows that were sampled twice, 11.3% of vaccinated cows and 2.3% of unvaccinated cows had increases in Leptospira antibody titers during the grazing season.     

Effect of oral inoculation of Escherichia coli on colostral antibody production in cattle.

Oral inoculation of approximately 1.2 x 10(9) viable Escherichia coli to pregnant cows resulted in increased blood serum and colostral whey titers to the "O" antigen. The antibody titers were more pronounced in colostral whey and were correlated with the inoculum strain of Escherichia coli. There was no correlation between antibody titers of the colostrum ingested and the resulting serum antibody titers of the calves. The incidence of diarrhea in calves did not correlate with the antibody titer in the colostrum. The occurrence of diarrhea was significantly greater in calves that did not ingest colostrum until they were 12 hours old, compared with calves that had free access to their dams and suckled within an hour of birth.     

Genetic x environment interactions on blood constituents of Angus, Brahman, and reciprocal-cross cows and calves grazing common bermudagrass or endophyte-infected tall fescue

Over a 2-yr period, effects of genotype and forage on blood metabolites, enzymes, and minerals were determined in Angus, Brahman, Angus x Brahman (sire x dam), and Brahman x Angus cows, and 129 calves from these cows sired by Hereford bulls. Cows and calves continuously grazed either common bermudagrass or endophyte-infected 'Kentucky-31' tall fescue pastures throughout the year. Blood samples were collected via jugular venipuncture in April, August, October (weaning), and November (after 30 d in a feedlot) of each year. Plasma urea N concentrations of cows and calves were affected by forage (P < 0.01) and breed (P < 0.05). Plasma cholesterol and FFA concentrations of cows were affected by forage (P < 0.01) and breed (P < 0.05). In calves, antibody titers to infectious bovine rhinotracheitis virus were not affected by forage but were affected by breed. Serum inorganic P concentrations of calves and cows were affected by forage (P < 0.05). Serum P concentrations and alkaline phosphatase activity of calves were affected by breed (P < 0.05). Calves grazing bermudagrass had higher (P < 0.05) serum concentrations of Fe and total iron binding capacity (TIBC). There was evidence of maternal heterosis for concentrations of free fatty acids, cholesterol, aspartate aminotransferase, Ca, Mg, alkaline phosphatase, ceruloplasmin, Fe, and TIBC. There was evidence of grandmaternal effects for plasma concentrations of urea N, cholesterol, Ca, P, Mg, and alkaline phosphatase. These results suggest that calves and cows grazing tall fescue are generally on a lower plane of nutrition than those grazing bermudagrass and that Brahman x Angus and Angus x Brahman crossbred cows and their calves seen to be more tolerant of the negative effects of tall fescue than the average of their purebred contemporaries.     

Bovine chlamydial abortion: serodiagnosis by modified complement-fixation and indirect inclusion fluorescence tests and enzyme-linked immunosorbent assay

Sequential serum samples from 11 cows experimentally inoculated with different abortigenic strains of Chlamydia psittaci were tested by a modified complement-fixation (MoCF) test, an indirect inclusion fluorescence antibody (IIFA) test, and an enzyme-linked immunosorbent assay (ELISA). One of these cows was not pregnant, another gave birth at term to a healthy calf, and all the others prematurely delivered infected dead calves or weak live calves. The results achieved with these tests on sera of 3 of the cows were compared with those from the previously used standard complement-fixation (CF) test. Six of 11 cows had detectable preinoculation titers between 1:8 and 1:16 when tested by the MoCF test, yet preinoculation titers were not detected by CF. In contrast, 9 of 11 and 10 of 11 preinoculation samples had detectable chlamydia-specific antibodies when examined by the IIFA test and the ELISA, respectively. The preinoculation IIFA titers ranged from 1:8 to 1:64, and the ELISA optical density values varied from 0.150 to 0.450. All cows responded with significant increases in antibody levels detected by the MoCF test, the IIFA test, and ELISA after they were experimentally inoculated and after they aborted or delivered infected calves. Overall, the dynamics of the antibody responses were found to be similar with the 3 different serologic techniques. When cows aborted later than 36 days after they were inoculated, the antibody response was biphasic, whereby the more pronounced responses occurred after the abortion occurred. The nonpregnant cow and the cow that delivered a healthy calf at term had only one phase of increasing and decreasing titers directly after they were inoculated.     

Antibody responses in protein-energy restricted beef cows and their cold stressed progeny.

Antibody titers were measured in serum and colostral whey of pregnant beef cows immunized with tetanus toxoid and chicken red blood cells while being fed diets either restricted or nonrestricted in protein and/or metabolizable energy during the last 150 days of gestation. Serum antibody titers were also measured in the colostrum-fed, cold and noncold stressed progeny that were actively immunized with dinitrophenol conjugated to keyhole limpet hemocyanin. In general, there were no major or sustained differences in humoral immune responses to injection of tetanus toxoid or chicken red blood cells between cows fed diets that were adequate or restricted in protein or metabolizable energy. In the few cases where serum antibody titers to tetanus toxoid or chicken red blood cells differed (P less than 0.05) between adequately fed or restricted cows, the differences were no greater than twofold. Anti-chicken red blood cell titers were uniformly low (P less than 0.05) by a magnitude of two to threefold in colostral whey of cows restricted in protein and/or metabolizable energy when compared to titers in cows fed adequate amounts of protein and metabolizable energy. With one exception, neither maternal dietary restriction nor cold exposure had a major effect on the ability of the calves to absorb antitetanus toxoid and chicken red blood cell antibodies from colostrum. The humoral immune responses of all calves to injection of keyhole limpet hemocyanin and dinitrophenol were similar in magnitude.     

Protection against bovine rotaviruses in newborn calves by continuous feeding of immune colostrum

Three pregnant cows were inoculated intramuscularly with inactivated vaccine to bovine rotavirus (BRV) serotype 1 (BRV-1) and serotype 2 (BRV-2). Serum neutralizing antibody (NA) titers against both serotypes increased significantly after immunization. NA titers of colostrum obtained from immunized cows against BRV-1 and BRV-2 were 29286 and 38109, respectively, which were significantly higher than those from non-immunized control cows. Nine and 6 colostrum deprived calves were orally challenged with BRV-1 and BRV-2, respectively, and monitored for clinical manifestation and viral shedding. Five calves of them, 3 with BRV-1 and 2 with BRV-2, received 2 l of milk replacer supplemented with 10% immune colostrum 2 hr before challenge and twice daily for the first 5 days after challenge. Other 10 calves, 6 with BRV-1 and 4 with BRV-2, were fed only milk replacer as controls. All control calves developed severe diarrhea and shed a large amount of BRV in feces, beginning from 24 to 48 hr after challenge inoculation. On the contrary, all calves but one fed colostrum supplement remained clinically healthy after challenge, and BRV was not detected in their feces during feeding immune colostrum. The possibility that continuous feeding of immune colostrum is capable of preventing newborn calves from diarrhea associated with BRV and viral shedding was suggested.     

Seronegative conversion in four Neospora caninum-infected cows, with a low rate of transplacental transmission

Four Neospora-seropositive pregnant cows (prebreeding indirect fluorescent antibody (IFA) titers between 1:400 and 1:1600) were confined and observed until parturition. All cows gave birth to normal calves. Selected tissues were tested for NC by histopathology, immunohistochemical (IHC) and polymerase chain reaction (PCR). Parasite isolation was attempted in vero cell cultures. At parturition, all cows were seronegative at 1:200 and two of four cows had a titer of 1:100 when further tested. Three of four calves were not infected, as determined by negative results of precolostral serology (1:25 cut-off), histopathology, IHC and PCR. One calf was congenitally infected, as shown by the presence of a thick-walled cyst labelled by IHC in its brain, positive PCR of brain and a precolostral IFA titer of 1:100. It was concluded that NC antibody titers may drop or convert to seronegative status in chronically infected cows by the time of parturition and this finding in four of four cows indicates that this could be a common occurrence. Similarly, the finding of an infected calf with a low antibody titer indicates that precolostral serology may not be a fool-proof means of identifying calves with congenital Neospora caninum infections. These findings call into question conclusions of other studies that have estimated rates of congenital transmission of this parasite based on serological tests at calving. This study is the first confirmed report of congenital NC infection in a calf in Thailand.     

Effects of colostral antibody on susceptibility of calves to Cryptosporidium parvum infection

Effects of colostral antibody on susceptibility of calves to Cryptosporidium parvum infection were examined. Six calves were fed pooled colostrum that contained C parvum antibody, 6 times daily (at 4-hour intervals) for 7 days and then milk replacer for 7 days. Colostrum was obtained from healthy cows or cows inoculated parenterally with C parvum oocysts before parturition. Antibody content was determined in serum and colostrum whey, using an ELISA for anticryptosporidia immunoglobulin. Six calves were fed colostrum from healthy cows 1 time, and then milk replacer 6 times daily for 14 days. On day 1, all calves were challenge exposed with C parvum, PO, and were monitored daily for diarrhea and oocyst shedding. Bovine colostrum containing specific antibody to C parvum, at ELISA titers up to 10,240, was not effective in protecting calves against challenge exposure to C parvum.     

Duration of immunity and efficacy of an oil emulsion Escherichia coli bacterin in cattle

An oil emulsion Escherichia coli bacterin administered in 1- and 2-dose vaccination regimens was evaluated in beef cattle. Serologic responses to the K99 pilus antigen were monitored, and suckling offspring from vaccinated and nonvaccinated cows were inoculated with virulent, K99-positive, enterotoxigenic Escherichia coli. The degree of protection and duration of immunity conferred were determined in 2 respective studies. In the first study (study A), titers of pregnant cattle were determined from time of vaccination through calving (a 6- to 20-week period). Titers of 24 cows vaccinated with a single 2-ml dose of bacterin were compared with those of 24 cows given a 2-dose regimen and with those of 23 nonvaccinated cattle (contemporary controls). Inoculum consisting of 1.2 X 10(12) viable enterotoxigenic E coli/dose administered to nursing calves from these dams yielded 0% mortality (0 deaths/20 calves) in calves from 1-dose vaccinates, 6% mortality (1 death/18 calves) in calves from 2-dose vaccinates, and 37% mortality (7 deaths/19 calves) in calves from nonvaccinated dams. Study B was an extended evaluation conducted in cattle that were kept in the study up to 87 weeks from initial vaccination until calving. Serologic titers to the K99 pilus antigen were compared in 1-dose, 2-dose, and nonvaccinated cattle in groups of 8, 6, and 6, respectively. Calves from these dams were inoculated with 8.1 X 10(11) viable enterotoxigenic E coli/dose, which resulted in 0% mortality (0 deaths/5 calves) in calves from 1-dose vaccinates, 0% mortality (0 deaths/5 calves) in calves from 2-dose vaccinates, and 80% mortality (5 deaths/6 calves) in calves from nonvaccinated dams.     

Detection of bovine antibodies to the outer membrane of ruminal Bacteroides succinogenes by enzyme-linked immunosorbent assay (ELISA)

The enzyme-linked immunosorbent assay (ELISA) was used to detect bovine serum antibodies directed to the outer membrane antigen of a ruminal bacteria, Bacteroides succinogenes. The outer membrane antigen of B. succinogenes was highly reactive against homologous antiserum, compared with rabbit sera raised against B. ruminicola subsp. ruminicola, B. ruminicola subsp. brevis and Selenomonas ruminantium. The titers of sera from colostrum-deprived calves were negligible level, while those of sera from colostrum-fed calves were relatively high. The mean titer of sera from 10 day-old calves was significantly (p less than 0.01) higher than that of 40 day-old calves, and was significantly (p less than 0.01) lower than that of adult cattle. The mean titer of sera from dairy cows which fed high-roughage diet was higher than that of feedlot cattle which fed high-concentrate diet. These results suggest that the antibodies against the outer membrane antigen of B. succinogenes transfer to calves via the colostrum, and that the titers of cows are affected by the way of feed management.     

Passive immunity to Pasteurella haemolytica A1 in dairy calves: effects of preparturient vaccination of the dams.

Dairy cows from five herds were assigned to receive a commercial Pasteurella haemolytica vaccine or no vaccine at all, administered at six and three weeks before parturition. Vaccination was associated with increased leukotoxin neutralizing serum antibody titers in the dams (p < 0.001), and with increased titers in colostrum (p < 0.001). Vaccination of dams also had a significant association with increased passive leukotoxin neutralizing antibody titers in their calves (p < 0.001). Vaccination was also associated with increased indirect agglutinating antibody titers in serum of the dams (p < 0.001). In the analysis of agglutinating antibody titers in colostral whey the interaction "vaccination*herd" was found to be significant (p < 0.001), indicating that the effects of vaccination on colostral titers were not consistent from herd to herd. The analysis was repeated, stratifying by herd. Vaccination was associated with increased agglutinating antibody titers in colostrum (p < 0.05) in three herds of the five in the study. In two of these three herds there were significant increases in passive neonatal titers associated with vaccination. In the remaining herd the mean IgG1 level in the calves was consistent with failure of passive transfer of immunoglobulins (IgG1 < 8.0 g/L). These results suggest that preparturient vaccination of dairy cows can induce modest increases in passive antibody titers to antigens of Pasteurella haemolytica in their calves, but the antigen of interest and the population being studied can affect the outcome.     

A seroepidemiological study of the importance in cow-calf pairs of respiratory and enteric viruses in beef operations from northwestern Quebec.

Serum antibody analyses for bovine herpesvirus type 1 (BHV-1), bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), bovine coronavirus (BCV), and bovine rotavirus (BRV) were performed on 527 randomly selected cows, before calving, and on 407 three-week-old calves. In cows and calves, BCV and BRV were the most seroprevalent viruses (80% to 100% according to virus and vaccination status). Bovine respiratory syncytial virus was the least seroprevalent in the cows, independent of the vaccination status. In nonvaccinated cows the seroprevalence to BRSV was 36.7%, and 53.5% in cows vaccinated less than two weeks prior to collecting blood, and 67.6% in cows vaccinated two weeks or more prior to blood collection. In their calves, BHV-1 was the least seroprevalent, independent of the vaccination status. The serological status and antibody titers in calves were generally associated with those of the dam. The occurrence of respiratory diseases in the calves was associated with cow and calf serological profiles (BHV-1, BRSV and BCV in the nonvaccinated group, BHV-1, BVDV and BCV in the vaccinated group). The occurrence of diarrhea was not associated with cow and calf serological profiles but was negatively associated with high level calf serum IgG in the nonvaccinated group (odds ratio = 0.73). Bovine coronavirus and BRV were shed by 1.4% and 4.9% of calves in the nonvaccinated group, and by 0% and 9.9% of calves in the vaccinated group, respectively. Bovine rotavirus shedding was associated with fecal diarrheic consistency at the moment of fecal sampling but not with previous occurrence of diarrhea.     

Inheritance and interaction of immune traits in beef calves

Three sets of blood samples were obtained from beef calves of two experimental populations and assayed for various immunological measurements. The first set of samples was taken between 24 and 48 h after birth and quantified for IgG1 concentration. A second set was taken immediately prior to vaccination for infectious bovine rhinotracheitis virus (IBRV; at an average age of 164 d) and a third set taken 60 d post-vaccination. These later samples were quantified for antibodies specific to IBRV. Level of complement C3 was also quantified in the samples taken immediately prior to vaccination. Three hundred sixty-seven calves were from four Hereford lines; three lines were previously selected for growth traits and the fourth was a randomly selected control line. There were no consistent differences in immune traits among these lines. The second group of 165 animals were Angus, Hereford and Red Poll calves. While Angus calves had a higher mean IgG1 concentration at 24 to 48 h of age than Hereford or Red Poll calves, no differences among breeds were found for the other immune traits measured. Calves from older dams (greater than 3 yr old) tended to have higher mean IgG1 concentrations, pre-vaccination IBRV antibody titers and complement C3 levels than calves from 2- and 3-yr-old cows. However, these calves had lower 60-d post-vaccination IBRV titers than calves from the younger cows (P less than .05). As pre-vaccination IBRV antibody titer increased, post-vaccination IBRV antibody titer decreased (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of a trainer cow on health, behavior, and performance of newly weaned beef calves

Experiments were conducted to investigate the effects of the presence of a trainer cow on behavior, performance, health, and feeding patterns of newly weaned beef calves. In Exp. 1,252 weaned calves (270+/-18 kg) were allocated to 22 pens (11 to 15 calves per pen). A trainer cow was randomly assigned to each of 11 pens. Calves were weighed prior to feeding on d 0, 3, 7, 14, 21, and 28. Rectal temperatures were taken on each of these days (except d 28) and blood samples were collected on d 0, 3, and 7 and subsequently analyzed for serum haptoglobin and leukotoxin antibody titers. Instantaneous scan observations of calf behavior were made at 10-min intervals between 0730 and 1730 on d 1, 2, 4, 5, and 6. A similar protocol was used in Exp. 2, in which 297 calves (258+/-17 kg) were allocated to 24 pens. Blood analyses included haptoglobin, white blood cell counts (WBC), and neutrophil:lymphocyte (NL) ratios. In Exp. 3, the above protocol was followed and patterns of feed bunk attendance of individual calves were also monitored using radio frequency identification by passive transponder ear tags. Trainer cows did not influence (P > .10) calf rectal temperatures, requirements for antibiotic therapy, WBC, NL ratios, or leukotoxin antibody titers. Pooled across treatments, NL ratios were lower (P < .01) on d 0 (.31) than on d 3 (.36) or d 7 (.39). Although differences in weight gain were detected in some periods within the three experiments, there were no differences (P > .10) overall (d 0 to 28). Trainer cows did not affect (P > .05) frequency or duration of bunk visits by the calves. Averaged across treatments, frequency and duration of bunk visits increased (P < .001) from 9.6 visits/d and 56.7 min/d between d 0 and 3 to 12.3 visits/d and 108.9 min/d between d 15 and 21. The number of calves observed eating during scan sampling observations also increased from 16.4% on d 1 to 25% on d 4 (P < .10) and 29% on d 5 and 6 (P < .05). More (P < .05) calves were observed lying on d 1 (41.7%) and d 2 (45.3%) than on d 4 (37.5%), d 5 (34.8%), or d 6 (36.2%). With a trainer cow present, fewer (36.7% vs 41.5%; P < .001) calves were observed lying and more (11.7% vs 10.2%; P = .08) were observed walking than when no cow was present. Trainer cows did not improve calf health, time spent at the feed bunk, or performance of newly weaned calves.     

Captive breeding of the white rhinoceros, Ceratotherium simum, and the Cape buffalo, Syncerus caffer

Breeding records of 40 white rhinoceros and 155 Cape buffalo were analysed. Three rhinoceros cows bred in captivity, themselves conceived for the first time at 84, 87 and 95 months of age, respectively. Rhinoceros cows breed throughout the year. There is no evidence of a relationship between calving interval and month of birth. Calving intervals were normally distributed about the mean of 34 months and there were no significant differences between bulls, cows or sex of calf. There was no difference in the sex ratio of calves born to young cows nor older cows. The male:female ratio of the calves was 1:1. Younger cows did not have shorter birth intervals. Although captive Cape buffaloes breed throughout the year, there is a preponderance of births in midsummer. There was some evidence that larger cows produce heavier calves and that season of birth may influence birth weight. Male calves weighed 41.20 +/- 0.68 kg vs 39.00 +/- 0.73 kg (range 24-60 kg) for female calves but this difference was not significant. Calving intervals were normally distributed about the mean of 395 days and the male:female ratio of the calves was 1:1.2.     

Reproductive performance of apparently healthy cattle persistently infected with bovine viral diarrhea virus.

A Holstein-Friesian bull and three Holstein-Friesian cows were seronegative for bovine viral diarrhea (BVD) virus but were persistently infected with the virus. Virus was isolated from buffy coat cells and nasal and lacrimal secretions during their lifetime, and they remained free of clinical signs of BVD. The three cows were pregnant when purchased, and they gave birth to full-term calves. One calf lived only a few hours, one calf became ill and died within a few days, and one calf became ill and was euthanatized within a few weeks. One cow was then bred and became pregnant but aborted a 7-month fetus. A second cow was bred approximately 5 months after parturition but did not conceive. The third cow was necropsied 6 weeks after calving, because of loss of weight. Although the bull's semen contained BVD virus when seropositive cows were bred, normal calves were born. When seronegative heifers were bred, they became seropositive to BVD virus within two weeks, with higher titers in six weeks. On heifer conceived after one service but aborted a 6-month fetus. Three others continued to have estrous cycles until their titers rose to 1:128, then they conceived and gave birth to normal calves. Another heifer conceived on the first service, had a titer of 1:128 two weeks after breeding, and gave birth to a normal calf.     

Epidemiologic factors and isotype-specific antibody responses in serum and mucosal secretions of dairy calves with bovine coronavirus respiratory tract and enteric tract infections.

Blood, feces, and nasal swabs specimens were collected 12 to 24 hours after birth and then 3 times/week (blood only once per week) from one group of 10 calves until they were 10 weeks old and from a second group of 10 calves until they were 10 to 20 weeks old. Colostrum was collected from all calves' dams and tears from 5 randomly selected calves in the first group. All fecal and nasal specimens were assayed for bovine coronavirus (BCV) antigens by ELISA. Nasal epithelial cells were examined for BCV antigens by direct immunofluorescence. Isotype antibody titers to BCV in all samples from 5 calves in group 1 were evaluated by ELISA. Zinc sulfate turbidity (ZST) values were determined on the first serum samples taken from all calves in group 1. To determine whether any correlation existed between ZST values, isotype antibody titers to BCV (12 to 24 hours after birth), number of respiratory sick days, number of enteric sick days, or days to first shedding of virus, a Spearman rank order correlation coefficient was done. Bovine coronavirus respiratory tract and enteric tract infections were common on this farm. Most initial infections developed when calves were 1 to 3 weeks old; however, there were also multiple incidences of shedding of viral antigens or seroconversions at later times during the study. Persistence of infection or reinfection of the upper respiratory tract with BCV was common. Colostral antibody titers to BCV (IgG1) were in all cows at moderate amounts; however, calf serum antibody titers and ZST values (12 to 24 hours after birth) were highly variable.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma 1,25-dihydroxyvitamin D, insulin-like growth factor-1, calcium, magnesium and phosphorus concentrations in pregnant beef cows and calves from a herd with a known history of congenital joint laxity and dwarfism.

An investigation was undertaken to ascertain the possibility of a relationship between calcium, inorganic phosphorus, magnesium, 1,25-dihydroxyvitamin D [1,25(OH)2D], and insulin-like growth factor-1 (IGF-1) concentrations in blood plasma and occurrence of congenital joint laxity and dwarfism (CJLD) in young cattle. Pregnant cows were fed hay (30 cows) or grass silage (122 cows) during winter months (October 15 to calving in March). Blood samples were taken from cows on seven occasions during the experiment and 48 hours after calving, and from calves at birth, and at seven, 14 and 56 days old. Five per cent of calves born (six of 122) to cows fed grass silage and none born to cows fed hay were affected by CJLD. The diet and health status of calves were not significantly (P greater than 0.05) associated with the plasma concentration of 1,25(OH)2D. The plasma calcium concentration declined with age of the calves (P less than 0.05) but was not affected by the occurrence of CJLD. Plasma phosphorus and magnesium concentrations in calves born to cows fed silage were higher (P less than 0.05) than in those born to cows fed hay. At birth and seven days old, plasma phosphorus concentrations were higher (P less than 0.05) in CJLD-affected calves than in healthy calves but the plasma concentration of IGF-1 was not different (P greater than 0.05). It was concluded that the high plasma phosphorus concentrations in CJLD-affected calves and their dams could be related to the aetiology of the CJLD condition in calves.