Conclusions

Les bovins viandeux produisent un colostrum de haute qualité, quelle que soit la race ou la parité. Les pourcentages Brix sont bien corrélés avec les concentrations colostrales en IgG1 mesurées par IDR mais des différences significatives existent entre les races et les parités. Pour cette étude, les pourcentages Brix seuils de 25,5 % et 26,9 % ont été proposés, afin de correctement classer les colostrums respectivement au-dessus de 75 g/L et 100 g/L. L’évaluation réfractométrique de la qualité du colostrum représente donc un test rapide, fiable et facilement réalisable sur le terrain qui permet d’améliorer les pratiques de gestion du TIC dans les exploitations viandeuses.

Short Communication

10.1136/vr.101590 | Veterinary Record | 1 of 2

Short Communication

Investigation of

colostrum quality in

beef cattle by radial

immunodiffusion and

brix refractometry

S. Vandeputte, J. Detilleux, F. Rollin

IN cattle, ingestion of sufficient good quality colostrum during the first hours of life is essential for the future health and performance of the calf (Rauprich and others 2000). However, colostrum quality, reflected by its IgG content, can vary widely among individual cows (Gulliksen and others 2008). As the colostrum quality cannot be pre- dicted by its physico-chemical characteristics (Maunsell and others 1999), it is crucial to assess its IgG concentration before administra- tion to the calf. Currently, several methods exist to measure the IgG content of colostrum, both directly and indirectly, but few of them are transposable to farm conditions. The use of a brix refractometer (BR) has been described for the assessment of the colostrum quality in dairy cattle (Bielmann and others 2008, 2010, Chigerwe and others 2008, Morrill and others 2012, Quigley and others 2013). To date, no such studies have been performed in beef cows while colostrum vol- ume and quality differ widely between dairy and beef cows. It is rec- ognised that colostrum produced by beef breeds is frequently of higher quality than dairy breeds colostrum, even if its volume is lower (Guy and others 1994, Lorenz and others 2011). Therefore, the selection and distribution of higher colostrum quality are important to ensure the transfer of a sufficient mass of IgG to the beef calf.

The aim of this study was first to assess the use of a BR for indirectly determining the IgG1 colostral concentrations in beef cat-

tle compared with the radial immunodiffusion assessment (RID). Additionally, the influence of breed and parity on the colostrum IgG₁ concentration was investigated. The second objective was to determine brix threshold values for IgG1 concentrations of 50, 75 and 100 g/l.

A total of 396 colostrum samples (~20 ml) were collected from freshly calved cows, immediately after calving and prior to the calf suckling the dam. For this study, rural practitioners were invited to participate by responding to a brief questionnaire and by collecting and dispatching colostrum samples to the laboratory (IODOLAB, Marcy l’Etoile, France). Information collected for each colostrum sam- ple included cow breed, parity and farm location.

IgG1 concentrations were measured by RID using a commer-

cial kit (BOV IgG₁ Test, IDBiotech) and stored at −20°C until

refractometric assessment. Refractometric analyses were performed at room temperature using an automatic temperature compensation digital BR (HI 96801, Hanna instruments). Before use, the refractom- eter was calibrated with distilled water and the well was cleaned with distilled water before each new reading.

A multivariable regression model was used to investigate the influ- ence of breed and parity on IgG₁ concentrations where IgG₁ concen- tration was the outcome variable with breed and parity as explanatory variables. Farm identity was included as a random effect.

The relationship between brix percentages and colostrum IgG₁ concentration was investigated with a spearman rank correlation.

Colostral IgG₁ concentrations of 50, 75 and 100 g/l were consid- ered as points of reference for the determination of brix threshold per- centages. All data were subject to a receiver operating characteristic analysis to select the most appropriate brix threshold percentage as the cut-off for each IgG₁ concentration. Sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV), AUC and Youden index were calculated using the SAS software (SAS Institute Inc, Cary, USA).

Results were considered as significantly different for P≤0.05. Samples were collected from 92 suckler herds; the number of samples collected per herd ranged from 1 to 46. Samples were collected from Charolais (n=226), Belgian Blue (n=112), Blonde d’Aquitaine (n=36) and Limousin (n=22) breeds of cows. Mean and median colostrum IgG1 concentration were, respectively, 95.9±36.2

and 94.4 g/l. Mean colostral IgG₁ concentrations did not differ sig- nificantly between breeds or parity. Brix percentages were normally distributed and the mean percentage was 26.3±5.2 per cent (range 10.7–43.7 per cent). Breed and parity have no influence on the IgG1

concentration (Table 1). Brix and RID results were highly correlated (R=0.8). Based on the colostral IgG₁ concentrations of 50, 75 and 100 g/l, brix threshold percentages of 22.5, 25.5 and 26.9 per cent were respectively calculated. For each of these brix threshold per- centages, Se, Sp, PPV, NPV, AUC and Youden index are presented in Table 2.

Studies related to colostrum IgG-IgG₁ concentration in beef cat- tle are scarce and generally included a low number of animals. Our study included a high number of beef cows (n=396) and samples were collected from 92 holdings and not from only one group of animals used for a specific experiment, as it was the case for many studies. Our data could be considered as more representative of the general colostrum quality of beef dams compared with previous studies. Nevertheless, the lack of some important information (farm manage- ment, cow’s nutrition, vaccination and so on) that could influence the colostrum quality does not allow us to assert this hypothesis with certainty. Breed and parity are important factors influencing colostral IgG concentrations (Guy and others 1994, Kehoe and others 2011) but no significant effect was found in this study. These results agree with other results obtained with beef cattle (McGee and others 2006,

Morrill and others 2012). Our correlation coefficient between RID and brix values (0.80) is above the coefficients of 0.71–0.73, 0.75 and 0.64 estimated by, respectively, Bielmann and others (2010), Quigley and others (2013) and Chigerwe and others (2008) in dairy cattle. However, other factors, such as the use of a different immunoglobulin class (IgG₁ in our study v IgG in other studies), may have an influ- ence on the correlation. Brix percentages of 18 per cent (Bielmann and others 2008), 21 per cent (Quigley and others 2013) or 22 per cent (Chigerwe and others 2008; Bielmann and others 2010) were reported in the literature to classify colostrum under or above 50 g/l of IgG. Our 22.5 per cent brix percentage is somewhat higher but a different iso- type was used in the present study (IgG1). The determination of brix

threshold for IgG₁ concentrations of 75 and 100 g/l allow assessing more precisely the quality of colostrum containing more than 50 g/l. The BR is an easy to perform cowside test that allows that the calf receive an appropriate amount of IgG1 even after ingestion of a lower

volume.

S. Vandeputte, DMV, MSc, F. Rollin, DMV, MSc, PhD, ECBHM

Clinical Department of Production Animals, Faculty of Veterinary Medicine, Clinic for Ruminants, University of Liege, Boulevard de Colonster, 20, B42, Liege B-4000, Belgium

J. Detilleux, DMV, MSc, PhD

Department of Animal Productions, Faculty of Veterinary Medicine,

University of Liege, Boulevard de Colonster, 20, B43, Liege B-4000, Belgium

E-mail for correspondence: vandeputtesebastien@hotmail.com Provenance: Not commissioned; externally peer reviewed Accepted July 10, 2014

2 of 2 | Veterinary Record | 10.1136/vr.101590

Acknowledgements

The authors especially thank Pascal Lebreton (NBVC) and Catherine Garnier (Iodolab) for their authorisation to use part of their data, their collaboration and for analysing the samples. We also thank Stephen Kuza from Hanna Belgium for supplying the refractometer during the whole protocol. Finally, the authors want to thank the Agricultural Services of the Province de Liège, especially Dr Vet. Philippe Müller who helped us throughout this study.

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RAUPRICH, A. B., HAMMON, H. M. & BLUM, J. W. (2000) Influence of feeding different amounts of first colostrum on metabolic, endocrine, and health status and on growth performance in neonatal calves. Journal of Animal Science 78, 896–908 TABLE 1: Results of a multivariate regression model describing effects of breed and parity on the IgG₁ concentration in the colostrum of 396 beef cows

Class Cows, n Estimate se P value

Intercept – 396 −44.69 21.02 0.036 Breed BB 112 1.23 4.65 NS C 226 3.17 3.97 NS BA 36 5.70 5.92 NS L 22 0 – – Parity 1 182 −17.10 20.09 NS 2 92 −14.91 20.18 NS 3 50 −13.16 20.26 NS 4 31 −16.28 20.37 NS 5 11 −17.87 20.90 NS 6 9 −11.36 21.13 NS 7 4 −0.56 22.38 NS 8 9 −16.15 21.12 NS 9 1 0 – –

Random effect Farms 92 – – –

BA, Blonde d’Aquitaine; BB, Belgian Blue; C, Charolais; L, Limousin

TABLE 2: Diagnostic test characteristic for brix threshold percentages calculated for colostral IgG₁ concentrations of 50, 75 and 100 g/l Brix percentages (%) IgG1 concentration (g/l) Sensitivity (%) Asymptotic 95% CI Specificity (%) Asymptotic 95% CI NPV (%) PPV (%) AUC Youden index 22.5 50 94.4 87.0 to 100 86.1 82.5 to 89.5 99.4 40.5 0.947 0.805 25.5 75 84.4 77.6 to 90.7 73.9 68.8 to 78.8 92.5 55.5 0.877 0.583 26.9 100 81.9 76.8 to 87.0 80.6 74.7 to 86.4 77.8 84.3 0.889 0.625

3.2 Comparaison de 4 réfractomètres pour l’investigation du transfert de