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* Department of Production Animal Clinical Sciences, Norwegian School of Veterinary Science, Oslo, Norway
Department of Cattle Health Services, TINE Norwegian Dairies, Ås, Norway
Department of Basic Sciences and Aquatic Medicine, Norwegian School of Veterinary Science, Oslo, Norway
TINE Norwegian Dairies Mastitis Laboratory, Molde, Norway
1 Corresponding author: stine.gulliksen{at}veths.no
| ABSTRACT |
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Key Words: colostrum dairy cow calf somatic cell count
| INTRODUCTION |
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Colostrum quality varies distinctly among individual cows (Pritchett et al., 1991; Maunsell et al., 1999; Liberg, 2000) and among different breeds (Muller and Ellinger, 1981; Tyler et al., 1999b). Colostrum containing less than 20 g of IgG/L to more than 110 g/L has been reported from cows from one single herd (Pritchett et al., 1991). Liberg (2000) found a variation in colostral IgG levels of 4 to 174 g/L in a study of colostrum from 660 Swedish dairy cows. Twenty-five percent of the cows had colostrum containing <50 g of IgG/L. Shearer et al. (1992) found that only 6.7% of 2,045 colostrum samples tested had IgG concentrations of 50 g/L or more.
Muller and Ellinger (1981) concluded that parity is an important factor in relation to colostral Ig content, with first-calf heifers having a considerably lower colostral IgG content than cows in their third or later parities. Several researchers have found this tendency of increasing colostral Ig concentration with increasing parity of the dam (Devery-Pocius and Larson, 1983; Shearer et al., 1992; Moore et al., 2005). In addition to parity, Pritchett et al. (1991) found the weight of first-milking colostrum to be the most important discriminator between colostrum of low (<50 g/L) and high (
50 g/L) IgG1 concentrations. Other factors, such as season of calving, BCS from dry-off to calving (Shearer et al., 1992), IMI during the periparturient period (Oliver and Sordillo, 1988), abortions (Straub and Matthaeus, 1978), and the health status of the cow, (Dardillat et al., 1978) have also been found to influence colostrum quality.
Although colostral IgG concentration is considered one of the most critical factors for sufficient Ig ingestion in newborn calves (Morin et al., 1997), numerous studies have concentrated exclusively on environmental and management factors as reasons for low serum Ig concentrations in calves (Filteau et al., 2003; Simensen et al., 2005). Most research projects on the topic of colostrum quality have focused on Holstein cattle, and only a few studies have examined other dairy breeds (Muller and Ellinger, 1981; Shearer et al., 1992; Quigley et al., 1994). The objectives of the present study were to evaluate the colostrum quality in Norwegian Red Cattle based on IgG content, and to identify associations between possible risk factors and low levels of colostrum IgG content.
| MATERIALS AND METHODS |
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Study Population
The final study population consisted of colostrum samples from 1,250 cows from 119 herds. The herd size ranged from 15 to 134.8 cow years, with a mean of 34 (SD = 29.4). A total of 73 (61.4%) herds submitted 12 samples or more, 43 (36.1%) herds submitted between 5 and 12 samples, and 3 (2.5%) herds submitted only one sample each. A total of 1,219 (97.5%) cows were of the NRF breed and 31 (2.5%) were crossbred NRF and another breed. In total, 451 (36.1%) of the cows included were first-parity cows, 337 (27.0%) were second-parity cows, 213 (17.0%) were third-parity cows, and 249 (19.9%) were cows of fourth parity or more. The seasonal breakdown was as follows: 346 (27.7%) colostrum samples were from calvings during winter (December to February), 280 (22.4%) were collected during spring months (March to May), 180 (14.4%) were from summer calvings (June to August), and 444 (35.5%) were from calvings during autumn (September to November).
Laboratory Analysis
The colostrum samples were thawed at room temperature and none of the samples were frozen more than once. Analysis on the IgG content in the colostrum was performed using single radial immunodiffusion (Immunocheck, SRID Kit, VMRD Inc., Pullman, WA). All samples were analyzed within 24 h after arrival at the laboratory. Samples with IgG content exceeding the maximum limits of the SRID test, resulting in ring diameters outside the range of the standard reference curve, were retested after dilution according to the test recommendations.
Health Registrations
Members of the NDHRS are obligated to report information regularly on diseases and any preventive treatments for each individual animal to a central database managed by TINE Norwegian Dairies. All health registrations are recorded according to a 3-digit coding system used in the Norwegian Cattle Health Recording System, given by the Norwegian Cattle Health Services. In the current study, the following health recordings were extracted from this system: any occurrence of dystocia (calvings where assistance is necessary), mastitis, retained placenta, or milk fever, from 15 d prior to and 2 d post calving, as well as a prolonged gestation period (>296 d of gestation, followed by induced calving). Further details regarding the health recording system are given by Østerås et al. (2007). Data on routine milk analysis, including SCC, milk yield, and the amount of concentrates (in kg) given to each animal on the test day, were extracted from the NDHRS.
Statistical Analysis
Data recorded were stored in Microsoft SQL Server and Microsoft Excel (Microsoft Corporation, Redmond, WA) and transferred to SAS, version 9.1 (SAS Institute Inc., Cary, NC) for descriptive statistics and statistical analyses. All 1,250 samples were included for the descriptive statistics. The following cows were excluded from the statistical analysis on milk characteristics: cows with no registrations on concentrate feeding (n = 20) or milk yield after calving (n = 51), cows without registrations regarding the first SCC after calving (n = 65), or cows having registrations of the first SCC after calving from a sample collected before 7 d after calving (n = 45) or later than 66 d after calving (n = 53). The final data set for further statistical analyses consisted of 1,017 cows from 119 herds.
The normality of colostral IgG in grams per liter was checked visually by using a PROC UNIVARIATE plot. The normality of the untransformed result (g of IgG/L) and the log transformation of the result seemed equally acceptable, although the first was slightly right skewed and the other slightly left skewed. Two separate mixed models were fit by using PROC MIXED. In model 1, the untransformed result (g of IgG/L of colostrum) was used as the dependent variable and in model 2, the result as an ordinal variable was used, divided into 8 groups: <20, 21 to 30, 31 to 40, 41 to 50, 51 to 60, 61 to 70, and 71 to 80 g of IgG/L; all samples with an IgG content exceeding 80 g/L were included in the eighth group. In both models, herd as well as the sire of the dam were used as random effects. The initial full models included the following fixed effects: herd size, parity, month of calving, kilograms of concentrate fed on the test day, SCC after calving, geometric mean of the last 3 measures of SCC before calving, first recorded milk yield after calving, any occurrence of dystocia, mastitis, retained placenta, or milk fever from 15 d prior to and 2 d after calving, and prolonged gestation period, year of sampling, and number of samples per herd. A third multivariable model was fit with colostral IgG content <30 or
30 g/L (0, 1) as the dependent variable by using PROC GENMOD with a binomial distribution and logit link function with Wald statistics type 3 contrasts. In this model, hierarchical dummy variables were created from SCC, in cells per milliliter, after calving: SCC >10,000, >20,000, >50,000, >100,000, >200,000, and >400,000. All other fixed effects used in the first 2 models were also included in the third. Nonsignificant variables were removed one by one by using backward stepwise elimination, with inclusion criteria of P < 0.05. Possible interactions between significant fixed variables were tested. The model fit was evaluated by using –2 log likelihood (Dohoo et al., 2003).
| RESULTS |
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We found a cluster effect within herd of 13.7%. No cluster effect of the sire of the dam was detected. Colostrum IgG content was not influenced by year of sampling or number of samples per herd.
Time until first feeding of colostrum was recorded for 666 (53.0%) of the 1,250 colostrum samples. Among these, first colostrum was fed within 2 h after calving in 479 (71.9%) cases, whereas first colostrum was fed within 4 h after calving in as many as 616 (92.6%) cases.
| DISCUSSION |
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Statistical Analyses
The colostral IgG content had a slightly right-skewed distribution, so different models were fit to evaluate possible differences in explanatory variables depending on whether we chose to emphasize high or low IgG values. In model 1, using natural figures, associations with high IgG levels were emphasized. The effect of extreme IgG values was subdued by transforming the result into an ordinal variable in model 2. The third model was created to focus on factors that could result in the production of colostrum of very poor quality (<30 g of IgG/L).
Parity
The results of this study support the findings of increasing IgG content with increasing parity (Tyler et al., 1999b; Moore et al., 2005). This increase was most pronounced between cows of first or second parity and cows of at least four parities. Older cows, being exposed to antigens for a longer time during their life than younger cows, seemed to produce colostrum with higher antibody levels. Even though our results showed a trend of increasing colostrum quality with increasing parity, there is no reason why farmers should discard colostrum from first-parity cows without testing the IgG level. We found that cows in their second parity produced colostrum of poorer quality than both first-parity cows and older cows. This coincides with the results from Quigley et al. (1994) in which colostrum samples from 88 Jersey cows were analyzed. Pritchett et al. (1991) found that second-parity cows had a significantly lower IgG concentrations than older cows, but like Tyler et al. (1999b) and in the present study, they found no significant difference between first- and second-parity cows. An explanation for why colostrum differs between second-parity cows and cows in other parities was not identified.
Calving Season
In the current study, cows calving during the winter months had significantly lower IgG levels than cows calving in other seasons of the year. In contrast, Pritchett et al. (1991) found that the season of calving did not significantly influence colostral IgG concentration in 900 Holstein cows from a commercial dairy farm. Seasonal variation might be of more importance in Norway than in other countries. The marked variation in climate among the different seasons leads to differences in the occurrence of disease, feeding regimen, and indoor climate, which may influence IgG production. In the current study, cows calving during August, September, and October produced colostrum of higher quality compared with cows calving during other seasons. According to Norwegian law, cows should spend at least 8 wk on pasture each year. The pasture season in Norway is usually between late May and late September, the length depending on the latitude. This entails a change in feeding regimen, often from silage to fresh grass, which might be beneficial when it comes to colostrum quality in cows calving during late summer and autumn. The improvement in colostrum quality in autumn may partly explain the reduced calf mortality rates in Norway during this period of the year (S. M. Gulliksen, unpublished data), although Simensen et al. (2005) found that Norwegian dairy calves born from April through June had the highest serum IgG levels. Gay et al. (1983) discovered that the mean monthly serum IgG1 concentrations in calves were lowest in the winter and increased during the spring and summer, to reach a peak in September. The results of the current study indicate that dairy herds with the opportunity to adjust their calving pattern at the herd level should consider seasonal differences in colostrum quality in their decisions.
SCC
An SCC of >50,000 cells/mL was the only test-day result found to be significant for the production of colostrum with very low IgG values. Our results are in contrast to those of Maunsell et al. (1999), who found that SCC had no effect on colostral IgG content. On the other hand, we found no association between SCC measured before calving and colostral IgG content; that is, precalving milk characteristics could not predict colostrum quality in our study. Whist and Øste
s (2007) showed that the association between SCC and later clinical mastitis begins already at 40,000 to 50,000 cells/mL, and similar to the results of the current study, established an obvious benefit of low cell counts. Similarly, Kehoe et al. (2007) found that cows from farms with a herd average SCC of <200,000 in the month before samples were collected produced colostrum of higher nutrient quality. Lundborg et al. (2003) found an increase in the number of clinical cases of respiratory disease among calves from cows with SCC between 34,500 and 124,000 compared with calves from cows with lower SCC. According to our study, this could be a result of low serum Ig concentrations caused by feeding colostrum of inferior quality.
Cluster Effects
Numerous studies have restricted the population from which they obtain colostrum samples to one single herd (Pritchett et al., 1991; Shearer et al., 1992); thus, a cluster effect within herds has not been addressed in these studies. According to our results, a cluster effect of 13.7% implies that management factors that vary among farms (i.e., feeding, environment, housing, etc.) are of importance when it comes to variation in colostrum quality. We found the amount of concentrate fed to be negatively correlated with IgG concentration. The amount of concentrate fed was also highly correlated with milk yield after calving; therefore, the 2 factors could not be included in the statistical models simultaneously. However, testing the model fit with either one of the 2 variables showed that including the amount of concentrate fed gave a slightly better model. The negative correlation between colostrum quality and these 2 variables could be an indication of a negative consequence of intensive feeding or a dilution effect on colostrum IgG, because intensive feeding will result in a higher daily milk yield. We identified no noteworthy cluster effect of sire of the dam, indicating a possibility of no heritability for colostrum quality, in spite of high heritability on milk yield (Dechow and Norman, 2007).
Representativity
All farms participating in the study had a herd size exceeding 15 cow years, resulting in a mean herd size considerably larger than the average herd size of 17 cow years in Norway today. Cattle production in Norway has undergone many changes the last 10 to 20 yr and is currently changing rapidly. The authorities demand that all cattle be housed in free stalls by 2024 and the number of cooperatives is increasing, hence the herds are getting larger. Participation in the project was voluntary. This might have led to herdsmen more interested in calf health, who are running well-managed farms, being overrepresented in the study. On the other hand, farms already having calf health problems might have been more motivated to participate for that same reason.
The colostrum samples in this study were sampled from one random, but healthy, quarter from each cow. This was done under the assumption of minimal differences among the 4 quarters and to ease the work load of the farmers. The likelihood of differences in IgG content among the 4 quarters in the same udder has been studied, but the studies are few and often small, and the results differ. In a study of 113 Holstein cows, Maunsell et al. (1999) found no difference in IgG content in colostrum from different quarters.
The participating farmers were instructed to sample colostrum from the cows first milking as soon as possible after calving. For practical reasons, colostrum from cows calving at night might have been collected several hours after calving. This may have lowered the IgG level in these samples. In the current study, the first colostrum fed was reported to be carried out within 4 h in 92.6% of the cases where this registration was done. In all likelihood, the colostrum samples were collected before or at the time of first colostrum feeding. There was no difference in the distribution of colostrum IgG content between samples for which the time until feeding was reported and those for which this registration was missing. Therefore, we assume that the vast majority of the samples in this study were collected within 4 h after calving. Moore et al. (2005) found that colostrum sampled 6 h after calving or later had a significantly lower IgG content than colostrum collected 2 h after calving. Pritchett et al. (1991) and Straub and Matthaeus (1978) found that as long as the cows were milked within 8 or 9 h after calving, respectively, the interval between calving and first milking had no significant influence on the colostral IgG1 concentration. The possibility of prior nursing by calves after calvings on pasture or in free stalls without the farmer noticing may have resulted in the sample being colostrum from a later milking, thereby reducing the colostral IgG content in the sample.
Practical Consequences
A common phenomenon in the majority of the research done on colostrum quality, including the present one, is the wide range of variation in colostral IgG content from different cows within a restricted area. These individual variances make it difficult to draw conclusions concerning different risk factors and thereby providing sufficient advising when it comes to management and colostrum quality.
Until now, most research has concentrated on aspects of colostral management other than colostrum quality, such as time of feeding, volume fed, and feeding method. Because most dairy calves are fed a fixed volume of colostrum after birth, colostral IgG concentration is an important determinant of adequate passive transfer in calves. Because the majority of the Norwegian dairy cow population seems to produce colostrum of inferior quality compared with international recommendations, this study indicates a need for improved colostrum quality control and subsequent adjustment of the colostrum feeding regimen to ensure a protective immunological status of newborn calves.
| ACKNOWLEDGEMENTS |
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Received for publication June 15, 2007. Accepted for publication October 2, 2007.
| REFERENCES |
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s. 2007. Associations between somatic cell counts at calving or prior to drying-off and clinical mastitis in the remaining or subsequent lactation. J. Dairy Res. 74:66–73.[CrossRef][Medline]This article has been cited by other articles:
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