Evaluation of plasma immunoglobulin G and BW thresholds for predicting preweaning mortality in commercially raised dairy goat kids

Assessing the impact of colostrum feeding delay on serum immunoglobulin G and total protein in dairy goat kids

This experiment was motivated by the need to understand the impacts of delaying the first colostrum feeding on the prevalence of failed transfer of passive immunity (FTPI). A cohort of 216 kids was stratified into groups based on the colostrum feeding delay postbirth: 0-4 h, 4-8 h, 8-12 h, and 12-16 h. All kids received a single colostrum meal of 300 mL, and blood samples were collected approximately 36 h after feeding. Serum immunoglobulin G (SIgG) was measured using ELISA, and serum total protein (STP) was assessed using the Bradford method and refractometry (STPb and STPr). Statistical methods like Pearson correlations, Bland-Altman plots, and Lin's concordance coefficient were employed to assess associations and agreements between SIgG, STPb and STPr. Receiver operator characteristic analysis was employed to determine optimal STPb and STPr thresholds for predicting FTPI (SIgG < 12 g/L). Subsequently, areas under the curve, sensitivity, and specificity were examined to assess the accuracy of these thresholds. Our results showed that for each hour's delay from birth to colostrum intake (up to 16 h), IgG apparent efficiency of absorption (AEA) decreases at an approximate rate of 2.0% per hour, and SIgG decreases at an approximate rate of 1.0 g/L per hour. However, this decline is not constant over time but intensifies progressively with increased feeding delay. Specifically, reductions in IgG AEA were 1.3, 2.9, and 5.9% per hour, and decreases in SIgG were 0.2, 0.3, and 0.7 g per hour for SIgG across the time intervals of 0-4 to 4-8 h, 4-8 to 8-12 h, and 8-12 to 12-16 h, respectively. Additionally, there was an increase in SIgG of 1.2 g/dL but a decrease in IgG AEA of 1.9% for each gram per kg of BW increase in IgG intake. The correlations between SIgG and STPr and STPb were 0.62, and 0.36, respectively. Optimal STPr and STPb thresholds predicting FTPI were determined to be 4.6 and 6.2 g/dL. The prevalence of FTPI, according to SIgG, STPr, and STPb thresholds were 63, 62, and 45%. Overall, STPr showed higher values for key performance metrics (i.e., sensitivity, likelihood ratio of positive tests, overall accuracy, and Youden's index), indicating better prediction ability than STPb. Our findings corroborate the critical importance of swift colostrum administration, ideally occurring no later than 12 h postbirth. Moreover, our research validates the effectiveness of Brix refractometry as a practical, on-farm method for assessing FTPI in goat kids.

Postponing first colostrum collection: impact on immunoglobulin G in goat colostrum

This experiment was motivated by the need to understand the impacts of delaying the first colostrum collection on immunoglobulin G (IgG) concentrations in goat colostrum, addressing a gap in caprine-specific research, despite its significance in dairy farming. Concurrently, we examined the relationship between colostral IgG, total protein (TP) and Brix values. Two colostrum samples were collected from 56 Saanen goats, one from each udder half. The first sample was collected from the right teat immediately postbirth, and the second sample was collected from the left teat at one of the predetermined postpartum intervals: 0, 4-6, 8-10, or 12-14 h postpartum, each time interval comprising 14 goats. Colostral IgG was determined by ELISA, Brix was determined by digital refractometry, and TP was determined by the Bradford protein method. Sperman's correlations and Lin's concordance correlation coefficient were used to determine the direction and strength of the association and to assess agreement (prediction accuracy) between methods, respectively. Receiver operator characteristic analysis was used to determine Brix and TP thresholds for predicting good-quality colostrum using several cut-offs (20, 30, 40, and 50 g/L IgG). Mean (± SD) for colostral IgG, Brix, and TP were 54 ± 22.6 g/L, 22 ± 5.0%, and 12 ± 2.8 g/dL, respectively. The statistical analysis did not provide evidence of a significant impact of time of first collection (up to 14 h postpartum), on IgG, Brix, and TP. Brix and IgG values exhibited both a high degree of correlation (r = 0.89-90) and concordance (ρc = 0.89-90), indicating a strong and reliable relationship between the two measurements. The prevalence of samples ≥ 20, 30, 40, and 50 g of IgG/L were 96, 88, 71, and 54%, respectively. Optimal Brix and TP thresholds predicting IgG ≥ 20, 30, 40, and 50 g/L IgG were 13.8, 17.5, 20.1, and 22.5%, and 6.8, 9.3, 10.8, and 11.1 g/dL, respectively. Increasing the IgG threshold resulted in lower sensitivity but higher specificity for estimating colostral IgG using Brix or TP values. The present findings indicate that delaying the first colostrum collection up to 14 h postpartum did not result in conclusive changes in colostral IgG concentration, Brix values, or total protein levels. Our results also confirm the reliability of Brix refractometry as an on-farm tool for estimating IgG concentrations in goat colostrum. These results are particularly relevant to intensive dairy systems, offering insights to enhance colostrum management and task prioritisation, especially during the bustling kidding periods.

Successful transfer of passive immunity: the natural alternative to antibiotics for boosting the survival of intensively reared dairy goat kids

In dairy operations, antibiotics have traditionally been used to treat, prevent, and control diseases. However, given the mounting global crisis of antimicrobial resistance (AMR), farmers are urged to re-assess and reduce their reliance on antibiotics. Thus, this randomized, double-blinded cohort study aimed to estimate the prevalence of failed and successful transfer of passive immunity (FTPI and STPI) in dairy goat kids reared under commercial conditions, and the effects of antibiotic metaphylaxis on the pre-weaning (≤42 d old) mortality in FTPI and STPI kids. Plasma concentration of immunoglobulin G at 1d old (pIgG-24 h) was measured in 747 male Saanen kids for the determination of FTPI and STPI (pIgG-24 h < 12 and ≥12 g/L, respectively). Kids were then randomly divided into two groups: those receiving a single penicillin injection at 1 d old (PEN), and those receiving no treatment (CTR). The mean (±SD) pIgG-24 h and initial BW (IBW) were 17 ± 9.8 g/L and 4.1 ± 0.64 kg. The prevalence of FTPI was 29% (220/747 kids). Gastrointestinal complications were the primary cause of death (41%), followed by septicemia (22%) and arthritis (17%). A single penicillin injection reduced preweaning mortality by 55% (10 vs 22%, PEN vs CTR). However, results suggest that such a decline was mainly driven by the improved survival rates among FTPI kids, which increased by 19% (from 62% in CTR-FTPI to 82% in PEN-FTPI), as opposed to an 8% increase among STPI kids (from 85% in CTR-STPI to 93% in PEN-STPI). Additionally, the odds of mortality ≤ 42 d old were threefold higher in the CTR-FTPI group when compared to both the CTR-STPI and PEN-FTPI groups, suggesting a potential parity between STPI and PEN for mortality rate reduction. Taken together, the results indicate that although metaphylactic antibiotics can halve preweaning mortality, similar improvements are likely to be achieved via increased STPI rates. Furthermore, by targeting metaphylactic interventions to high-risk groups (i.e., those displaying signs of inadequate colostrum intake and/or low birth BW), farmers could reduce treatment costs and mitigate AMR risks. While these findings carry considerable weight for commercial dairy goat practices, their applicability to other systems (i.e., extensive, semi-intensive, mohair, meat systems) warrants further investigation.