Performing Department
Medicine & Epidemology
Non Technical Summary
The two most important factors affecting transfer of colostral immunity from the cow to the calf are colostral immunoglobulin G (IgG) concentration, and calf age at feeding. Feeding 4L of colostrum within 12 hours old reduces the likelihood of failure of passive immunity (FPI) in calves. A total of 150-200 g of colostral IgG should be delivered to the calf's gut to ensure adequate passive immunity (API). Despite these colostrum feeding recommendations, 19-21% of calves suffer from FPI, thereby exposing them to increased rates of morbidity, and mortality. Pooling colostrum is a common practice on Californian dairies. Pooling colostrum allows efficient pasteurization and makes colostrum immediately available to the newborn calf. However, pooling might decrease the colostral IgG concentration fed to the calf due to the dilution effect. This is because cows producing low IgG concentration colostrum are more likely to produce larger volumes of colostrum. Therefore, pooling might increase the likelihood of FPI in calves on farms where a higher number of cows with low colostral IgG concentration contribute to each colostrum pool. Pooling colostrum is inevitable on dairies, and recommendations to achieve API in calves following pooling are warranted. To date, no peer reviewed studies are available describing the minimum individual cow colostral IgG concentrations required for pooling. This study will determine the minimum individual cow colostral IgG concentration required for pooling, other variables that affect IgG concentrations in pooled colostrum, and the effect of pooling on FPI in calves in California.
Animal Health Component
100%
Research Effort Categories
Basic
30%
Applied
60%
Developmental
10%
Goals / Objectives
Hypothesis - A minimum individual cow colostral IgG concentration is required for pooling to achieve API in calves fed pooled colostrum.Objectives: 1. Determine a combination of factors including parity, individual cow colostral IgG, number of cows contributing to a pool, and first milking colostrum volume that contributes 150-200g IgG in pooled colostrum to achieve API in calves.2. Compare the accuracy of calculating mean pool IgG concentration based on individual cow colostral IgG concentrations with the true pool IgG concentration.3. Quantify the minimum individual cow colostral IgG concentrations required for pooling colostrum to achieve API in calves.4. Compare API rates, apparent efficiency of absorption (AEA), average daily gain (ADG), morbidity, and mortality among calves fed different colostrum pools.Our research will answer the following:Question 1: What is the effect of individual cow colostral IgG concentrations on pooled colostrum IgG concentration?Question 2: What is the effect of the individual cow's first milking colostral volume on IgG concentration of pooled colostrum?Question 3: What is the effect of the number of cows contributing colostrum to a pool on colostral IgG concentration?Questions 4: Which combinations of factors (parity, individual cow colostral IgG, number of cows contributing to a pool, first milking colostrum volume) achieve a total of 150-200g IgG in pooled colostrum, and achieve API in calves?
Project Methods
Project details:Design: A prospective study will be performed on a 2000-cow Jersey conventional dairy in Merced County, California. On the farm of study, 8-12 calves are born daily, and colostrum is collected from cows within 2 hours after parturition. Colostrum from 8-12 cows is pooled prior to heat treatment. The farm's mean individual colostral IgG concentration is 67 ± 3.3 g/L (range, 33 - 72 g/L) [17]. Given that calves on this farm are fed 4L of colostrum with an average concentration of 67g/L of IgG, then an average of 268g (67 × 4) of IgG, with a range of 132g (33 × 4) to 288g (72 × 4) is fed to the calf. Therefore, sample size was calculated to detect a difference of 2-18g of IgG among the colostrum pools, a standard deviation of 3.3, [17] power of 80%, and a type-1 error of 5%, using a statistical software [b]. A sample size of 24 colostrum pools was required. To account for a 10% dropout proportion from lost samples, the total sample size required was 27 colostrum pools.Procedures: Cow ID, parity, and volume of first milking colostrum will be recorded for each cow. Each colostrum pool will be made from 12 cows. The volume of each colostrum pool will be 200 L, sufficient to feed 50 calves (4L/calf). Therefore 27 groups of calves (50 calves in each group) will be enrolled. A colostrum sample will be collected from each cow at first milking. Identity of the cow, parity, total number of cows, and individual cow colostral volume contributions, and total volume of each batch of colostrum pool will be recorded. IgG concentrations in pre-heated individual and colostrum pool and post-heat treatment pooled samples will be measured by radial immunodiffusion (RID). Age at first colostrum feeding and colostrum pool source will be recorded. Serum samples will be collected from calves at 48 hours of age and analyzed for serum total solids by a refractometer [c] and RID to determine passive transfer status. Calves with serum IgG concentrations >2000 mg/dL will be classified as having API [18]. Morbidity, ADG, and mortality of calves until weaning will be recorded from the electronic farm records.Data analysis: A first multivariate regression model will be performed to predict pool colostral IgG as a function of parity, individual cow colostral IgG, number of cows contributing to a pool, and first milking colostrum volume. This model will determine variables that significantly predict the pool colostral IgG [Objective 1]. A second multivariate regression analysis will be performed with similar predictor variables, but the outcome target pool IgG mass will be 150-200g. This model will determine the minimum individual colostral IgG concentrations required for pooling, and combination of factors that achieve API in calves [Objective 1 and 2]. Serum IgG concentrations, AEA and ADG among calves (27 groups) receiving different pools of colostrum will be compared using MANOVA. Proportions of calves with API will be compared using a χ2 test. A logistic regression predicting the probability of API as a function of colostrum pool IgG concentration, birthweight, age at first feeding of colostrum will be determined [Objective 3]. Proportions of morbidity and mortality among the calves fed different pools of colostrum will be compared using a χ2 test. A Cox proportional hazard model to determine hazard for mortality among the calves will be constructed [Objective 3].