Materials and Methods

Cows—Initially, calves from 106 Holstein cows were enrolled in the study but calves from 104 cows met the inclusion criteria. Cows of varying parity with confirmed breeding dates were drawn from the University of Missouri Foremost Teaching and Research Dairy from 2004 to 2007 to provide the calves. The research study was approved by the University of Missouri Animal Care and Use Committee.

All calvings were observed and attended. After parturition, calves were immediately separated from their dam, weighed, and identified. Only heifer calves were enrolled in the study. All cows were milked within 1 hour after parturition by use of a portable milking machine, and the volume of first milking colostrum was recorded. An aliquot (20 mL) of the composite first milking colostrum from each cow was collected from the milking bucket for colostral IgG determination. Samples were stored at −20°C for 7 to 12 months until processed.

Calves—Holstein heifer calves (n = 104) were assigned groups by use of random assignment without replacement. Equal numbers of calves (n = 26/group) received fresh first milking colostrum (collected from their dam) at 1, 2, 3, or 4 hours of age. Calves were offered 3 L of colostrum for 15 minutes administered via nipple bottle. Uningested colostrum was measured with a graduated cylinder, and actual intake was recorded. A second 15-minute, 3-L bottle feeding of colostrum was offered at 12 hours of age. Thereafter, calves were fed 2 L of milk replacer every 12 hours. Blood was collected via jugular venipuncture at 48 hours of age to determine serum IgG concentration. Calves that failed to ingest colostrum at both the first and second feeding were tube fed 3 L of colostrum and excluded from the study.

Colostral and serum IgG determination—Colostral and 48-hour serum IgG determinations were performed by use of adaptations of a reported radial immunodiffusion technique.¹⁷ Radial immunodiffusion plates were prepared by dissolving 1% agarose^a in a sodium barbital buffer^a containing 0.1% sodium azide.^a Rabbit–anti-bovine IgG (1%)^a was added to the agarose solution. Eleven milliliters of the agarose solution was added to 10-cm Petri dishes. After the agarose solidified, 3-mm wells were cut in the agar. Serum samples were diluted 1:20 and colostrum samples diluted 1:120 by use of a barbital buffer, and 5 PL was inoculated in each well. The diameter of the zone of precipitation was recorded after 72 hours of incubation at 23°C (73.4°F). Sample IgG concentrations were determined by comparing the diameter of zones of precipitation with a standard curve generated by use of serial dilutions of a lyophilized bovine IgG standard.^a The regression equation generated in this manner (r² = 0.97) accurately predicts inoculum IgG concentration.

Statistical analysis—Sample size determination in each group in this study was based on calculations on a power of 0.80, a type I error of 0.05, and means and SDs of serum IgG concentrations among calves derived from previous studies on the same farm. Normality of data was checked by use of standard statistical software.^b Mean colostral IgG concentrations (g/L) and SEM for cows in their first, second, third, or greater lactation were calculated. Mean ± SEM for calf weight, first milking colostral volume produced by the dam, and 48-hour serum IgG concentration for calves also were calculated. The serum IgG concentration cutoff point of ≥ 1,340 mg/dL was chosen for defining adequacy of passive transfer at 48 hours on the basis of previous studies.^18,19 Colostral intake at first feeding across the 4 treatment groups (1, 2, 3, or 4 hours of age) was compared by use of 1-way ANOVA (P < 0.05 was considered significant).^c A multiple regression model was developed to predict colostral intake (liters) at 12 hours of age as a function of calf age at first feeding (hours) and colostral intake volume at first feeding (P < 0.1 was used for initial inclusion, whereas P < 0.05 was considered significant for final comparisons).^d A logistic regression model predicting the probability of a calf having FPT at 48 hours of age was developed as a function of calf weight, calf age at time of first colostrum feeding, volume of colostrum ingested at first feeding, volume of colostrum ingested at 12 hours, dam parity, colostral volume produced by the dam, and colostral IgG concentration (P < 0.1 was used for initial inclusion, whereas P < 0.05 was considered significant for final comparisons).^e The probability of a calf having FPT on the basis of the 48-hour serum IgG was calculated as follows:²⁰

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where ColIgG is colostral IgG concentration, V₁ is colostrum volume intake (L) at initial feeding (1, 2, 3, or 4 hours of age), V₁₂ is colostrum volume intake (L) at 12 hours of age, and exp is exponential function.

Results

Forty, 28, and 36 calves were from cows in their first, second, and third or later lactation, respectively. Mean ± SEM of colostral IgG concentrations was 66 ± 3.4, 63 ± 5.2, 60.7 ± 6.5, and 72 ± 5.6 g/L for all cows, cows in their first lactation, cows in their second lactation, and cows in their third or later lactation, respectively. Colostral IgG concentration did not differ significantly among cows in their first and second lactation. Cows in their third lactation had significantly higher colostral IgG concentrations, compared with cows in their first or second lactation. Mean ± SEM of colostral intake by calves at initial feeding (1, 2, 3, or 4 hours) and 12 hours was 2.3 ± 0.1 L and 2.2 ± 0.1 L, respectively. Two calves did not ingest colostrum at both the first colostrum feeding and 12 hours of age and were excluded from the study. Mean ± SEM for calf birth weight and serum IgG concentration at 48 hours of age was 38.9 ± 0.6 kg (85.6 ± 1.3 lb) and 1,777.3 ± 57.8 mg/dL, respectively. Proportion of colostrum samples with IgG concentration ≤ 25, ≤ 50, ≤ 75, and ≤ 100 g/L were 0.07, 0.40, 0.67, and 0.85, respectively. Mean ± SEM for colostral volume produced by all cows was 9.5 ± 0.6 L. Twenty (19.2%) calves had FPT (serum IgG concentration < 1,340 mg/dL). Eighteen (17.2%) calves ingested 3 L of colostrum at first feeding and 3 L at 12 hours of age. First-feeding voluntary colostral intake was not significantly different among calves fed at 1, 2, 3, or 4 hours of age. Calf age at first feeding (1, 2, 3, or 4 hours), colostral volume ingested at first feeding, and their interactions were not significant predictors of colostral intake at 12 hours of age.

Results of the logistic regression model predicting the probability of a calf having FPT were determined (Table 1). Colostral IgG concentration, first colostral volume intake, colostral volume intake at 12 hours of age, and interaction between colostral IgG concentration and colostral volume intake at first feeding or at 12 hours were significant (P < 0.1) predictors of 48-hour serum IgG concentration. Parity of the dam, calf age at first feeding, calf birth weight, and colostral volume produced by the dam were not significant (P ≥ 0.1) predictors of FPT on the basis of the 48-hour serum IgG concentrations. Interactions between calf age at first feeding and volume of colostrum ingested at first feeding were not significant (P ≥ 0.1) predictors of FPT. Summary of the predicted probability of FTP for selected combinations of independent variables was tabulated (Table 2). A summarized flow chart illustrating recommended colostrum administration practices by nipple bottle was created (Figure 1).

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Flow chart summarizing recommended standard operating procedures for the feeding of colostrum to calves via nipple bottle based on colostral intake at first feeding (1, 2, 3, or 4 hours of age) and intake at 12 hours of age. *The FPT rates in calves that are fed by nipple bottle and oroesophageal tubing cannot be calculated. h = Hours.

Citation: Journal of the American Veterinary Medical Association 234, 6; 10.2460/javma.234.6.785

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Discussion

Cows in their third or greater lactation had higher colostral IgG concentrations than cows in their first or second lactation, consistent with a previous study.¹³ However, 1 study found no significant difference in colostral IgG concentration among cows in their first, second, or third lactation.²¹ This finding suggests that producers need to assess colostrum on the basis of IgG concentration rather than the relationship between the lactation of the cow and colostral IgG concentration. Feeding calves for a period of 15 minutes at each feeding was considered representative of the maximum effort a producer would spend trying to feed a newborn calf. The time may vary depending on available labor on a given farm and the perceived value of a calf. Twelve hours of age was considered optimal for the second feeding because cessation of intestinal permeability to colostral immunoglobulins occurs at a high rate after 12 hours of age.¹⁶ Several studies^4,6,18,22,23 detected different serum IgG concentrations as cutoff points for defining adequacy of passive transfer. A serum IgG concentration of ≥ 1,340 mg/dL was chosen to indicate optimum passive transfer in the present study on the basis of results of previous large field studies.^18,19 Although the 48-hour serum IgG concentration endpoint chosen in the present study was for optimal colostrum administration practice, the prevalence of FPT in this study (19.2%) was less than optimal. Nearly 20% of the calves receiving colostrum in the described manner will be at increased risk for morbidity, death, and decreased productivity.^2,3,5,6 An FPT prevalence < 10% is a rational and achievable goal.

Calf age, up to 4 hours, did not have a significant effect on ability to ingest colostrum from a nipple bottle or serum IgG concentration at 48 hours of age. Thus, within the first 4 hours, delaying feeding of calves to ensure adequate vigor is not warranted. Results of this study indicated that calves can ingest up to 3 L of colostrum at first feeding through a nipple bottle, consistent with a previous study.²⁴ Another study²⁵ found that calves can ingest up to 4 L through a nipple bottle. Furthermore, results of the present study indicated that calves will often ingest up to 3 L of colostrum at 12 hours of age regardless of colostral volume of intake at first feeding. Potentially, calves can ingest colostral volumes exceeding 3 L at each feeding, if it is offered. It is important to note that probability of FPT is low when calves ingest low volumes of colostrum that has high IgG content at 12 hours of age. However, the proportion of colostrum specimens with high IgG concentrations (> 50 g/L) is low. The probability of FPT in calves that ingested high volumes of colostrum at first feedings and at 12 hours was substantially lower than that of calves that ingested low volumes, even at low colostral IgG concentration. Consequently, allowing calves to ingest as much as they would within 1 to 4 hours of age and then at 12 hours of age will substantially reduce the probability of failure of FPT. It should be noted that the results of this study are based on calves from a single farm and are applicable only to calves that are bottle fed colostrum twice within 12 hours.

The presented recommendations (Figure 1) are premised on the goal of maintaining FPT rates < 10% and colostral IgG concentrations in the range of 40 to 50 g/L. It should be noted that in the present study, 40% of cows had colostral IgG concentrations < 50 g/L.

Calves should be offered the maximum volume of colostrum that they will voluntarily ingest within 4 hours of birth, and calves that ingest ≥ 3 L at the first feeding will need to ingest 1 L of colostrum at 12 hours to have optimum colostral intake. Calves that fail to ingest at least 1 L at 12 hours should be tube fed with 2 L of colostrum. Calves that ingest > 2 L but < 3 L of colostrum at 1, 2, 3, or 4 hours of age will require a minimum intake of an additional 2 L of colostrum by 12 hours of age. Those calves that do not ingest at least 2 L at 12 hours should be tube fed with 2 L of colostrum at that time. Calves that ingest < 2 L at their first feeding should be targeted for immediate oroesophageal tube feeding, and a total volume of 3 L should be administered in the first feeding. Calves in this category probably will need to ingest ≥ 1 L of colostrum at the second feeding to have optimum colostral intake. If they ingest < 1 L, they should be tube fed 2 L of colostrum. On the basis of results of our previous study²¹ in tube-fed Holstein bull calves, if we assume a colostral IgG concentration of 50 g/L, we anticipate that calves fed 3 L once will have an FPT rate of only 17%, even if no other colostrum is provided at 12 hours of age. On the basis of the results of that study,²¹ we do not expect feeding colostrum volumes exceeding 3 L once by oroesophageal tubing to decrease the rate of FPT in calves. It should be noted the FPT rates in calves that are fed colostrum by combinations of nipple bottle and oroesophageal tubing have not been critically investigated.

Bottle feeding of colostrum is potentially labor intensive on large dairy farms because of more time required to train a newborn calf to feed from a nipple bottle, compared with oroesphageal tubing. However, a considerable percentage of dairy producers prefer to feed colostrum to calves through a bucket or nipple bottle.¹⁵ A possible reason for preference of bottle feeding colostrum over tube feeding includes the technical skills and experience required to feed calves by use of a tube. Although results of previous studies^4,7 suggested that tube feeding of colostrum reduced FPT rates, compared with bottle feeding or nursing,⁴ bottle feeding improved colostral immunoglobulin absorption because of closure of the esophageal groove.⁷ Presently, no studies have match paired calves to receive equal amounts of colostrum by tube and bottle feeding for comparison. Such studies would critically compare the 2 methods to assess absorption efficiency of colostral immunoglobulins, and results would likely form the basis for future recommendations to dairy farmers regarding optimal colostrum administration practices.