Short communication: Use of a digital refractometer in assessing immunoglobulin G concentrations in colostrum and the first 5 transition milkings in an Irish dairy herd

peer-reviewedTransition milk is a source of immunoglobulin G (IgG) and could potentially be used to provide calves with passive immunity, when the IgG concentration is ≥50 g/L. Assessment of IgG concentrations in transition milk would be required before feeding and could be conducted using cow-side tests such as refractometers. Currently, limited information is available on the ability of refractometers to assess transition milk quality. We hypothesized that digital refractometry could be used to provide an accurate cow-side assessment of IgG concentrations in colostrum and transition milk, and IgG concentration in colostrum and one or more transition milking in an Irish herd is >50 g/L. The objectives of this study were to determine the IgG concentrations in colostrum and first, second, third, fourth, and fifth transition milk, and determine the utility of a digital refractometer in assessing quality of colostrum and transition milk produced by cows in a pasture-based dairy production system. A convenient sample of 75 dairy cows were enrolled. Colostrum and transition milk IgG concentrations were determined by radial immunodiffusion and refractometry. Sensitivity and specificity of the refractometer were determined and cut-off points that maximized sensitivity and specificity were determined using receiver operating characteristic curves. Median (range) IgG concentrations in colostrum and first, second, third, fourth, and fifth milking were 99.6, 43.5, 12.5, 5.3, 1.9, and 1.8 g/L, respectively. The sensitivity (0.8–1) of digital refractometry in identifying samples with low IgG concentrations in colostrum, first, second, and third transition milk was acceptable. In contrast, digital refractometry was not useful for assessing IgG concentrations in the fourth and fifth milking due to low IgG concentrations

Short communication: Effect of feeding pooled and nonpooled high-quality colostrum on passive transfer of immunity, morbidity, and mortality in dairy calves

peer-reviewedPooling colostrum is commonly practiced on Irish dairy farms. Pooling can result in dilution when colostrums with high and low IgG concentrations are mixed, thereby predisposing calves to failure of passive immunity. The objectives of this study were to compare IgG concentrations in colostrum from individual cows with colostrum pooled from several cows, and assess serum IgG concentrations, morbidity, and mortality among calves fed colostrum from their own dam, from a different cow, or pooled from several cows. We hypothesized that pooling colostrum reduces IgG concentration due to dilution compared with colostrum from individual cows, and that calves fed pooled colostrum achieve lower serum IgG concentrations than calves fed colostrum from individual cows. Calves were randomly assigned to 1 of 3 groups: (1) fed colostrum from their own dam (n = 20); (2) fed colostrum from a different dam (n = 20); or (3) fed pooled colostrum (n = 18). A sample of colostrum fed to each calf was collected. Serum samples were collected from calves at birth (0 h) and at 24 h after colostrum feeding. Colostrum and serum IgG concentrations were measured by radial immunodiffusion. Calves were weighed at birth and at weaning, and the health status of each calf was assessed twice daily. Health assessment was based on general demeanor, rectal temperature, fecal consistency, respiratory rate, and the presence of cough, nasal, or ocular discharge. Colostrum and serum IgG concentrations, and weaning weights were compared using ANOVA. Associations between group and morbidity or mortality rates were compared using χ2 or Fisher’s exact tests. Median and 95% confidence intervals (95% CI) of IgG concentrations of colostrum were 99.4 (81.8–111.5), 95.2 (84.1–107.2), and 100.7 (90.5–104.4) g/L for own dam, different dam, and pooled groups, respectively. We did not find any differences in colostrum IgG concentrations among the colostrum sources. Median (95% CI) serum IgG concentrations at 24 h were 52.0 (45.6–65.9), 55.7 (51.2–65.9), and 53.1 (46.2–63.7) g/L for calves that received colostrum from own dam, different dam, and pooled, respectively. All calves achieved adequate passive immunity. Serum IgG concentrations at 24 h, weaning weights, and proportions of morbidity and mortality were not different among the 3 groups. Our results suggest that on dairy farms where median colostrum IgG concentrations are high and colostrum management is optimal, pooling has a minimal effect on passive immunity and subsequent calf health

Promoting higher levels of immunity from colostrum among calves on organic dairy farms

Colostrum feeding provides immunoglobulins, in a process called transfer of passive immunity, which is critical for dairy calf health and welfare. However, failure of transfer of passive immunity (FTPI) occurs in about 12% of calves nationwide. This study compares the prevalence of FTPI between calves raised on organic and conventional dairy farms, describes the colostral management practices on organic dairy farms in California, and recommends improvements. We compared serum immunoglobulin G (IgG) concentrations between calves raised on organic and conventional dairies and found that the odds of FTPI in calves raised in organic dairies were 2.5 times greater than in calves raised in conventional dairies. Focusing on varied practices in organic dairies, FTPI was 2.9 times more likely in calves fed less than 4 liters of colostrum within the first 24 hours, compared to calves fed more than that amount. We also found that organic dairy producers did not routinely monitor colostral IgG concentrations and passive immunity status. We recommend that organic dairy farmers adopt these practices to decrease the prevalence of FTPI in calves