Abstract :
[en] Transfer of colostral immunity (TCI) can be defined as the process through which maternal
immunoglobulins are transfered to the calf through colostrum. The importance given to the
acquisition of an adequate TCI for the calf health and productivity has long been recognised.
TCI can be assessed by the measurement of the calf serum IgG (direct method) or by
measuring other parameters correlated with serum IgG concentration (indirect method). The
success of TCI depends on several factors, the most important being colostrum quality and
quantity and feeding delay. Practically, colostrum quality remains the most difficult factor to
deal with. Indeed, quality is very hard to estimate because it is influenced by several factors
such as breed, parity and individual. As for the TCI, colostrum quality can be assessed by
direct and indirect methods. The study first aimed at evaluating the quality of colostrum
produced by four beef cattle breeds and to compare the results with measurements realised
with a Brix refractometer. Beef cows produced a high quality colostrum without any
significant negative impact of breed or parity. An IgG1 concentration lower than 50g/L was
measured in less than 10 % of colostrum samples. Refractometric measurements and
colostrum IgG1 concentrations were strongly correlated even if correlation coefficients
obtained for breed and parity were significantly different. Brix percentage identified for beef
cattle for the IgG1 50 g/L value was slightly higher compared to those described for dairy
cattle in other studies. In order to correctly classify a beef cow colostrum as a good quality
product, concentrations of 75 g/L and 100 g/L were preferred to the 50 g/L concentration used
for dairy cows; indeed, beef cows produce less of a more concentrated colostrum. The use of
25.5 % and 26.9 % Brix percentages allows to correctly classify high quality colostrum based
on IgG1 concentrations of 75 g/L and 100 g/L, respectively. The second aim of the study was
to compare the accuracy of four refractometers (Atago, Atago ATC, Wolf ATC and digital
ATC refractometers) for measuring serum total protein (STP) concentration and to assess the
efficacy of TCI using the 16g/L serum IgG concentration threshold. In addition, the
assessment of TCI by means of the gamma-glutamyl transferase (GGT) activity and
gammaglobulins concentration was also performed. Refractometric measurements of STP
were highly correlated with those obtained with the biuret method frequently used as the
laboratory method. The four refractometers presented a similar accuracy for STP assessment
despite a significantly higher bias for the Wolf ATC refractometer. When considering the 16
g/L serum IgG threshold, STP concentrations of 56, 58, 54 and 56 g/L were measured for the
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Atago, Atago ATC, Wolf ATC and digital ATC refractometers, respectively. For reasons of
simplicity and convenience, the concentration of 56g/L could be used for the four
refractometers without losing much accuracy. The GGT activity only reflected colostrum
uptake by the calf whereas gammaglobulins concentrations were highly correlated with IgG.
The last objective of the study was to evaluate, under farm conditions, the efficacy of a bovine
concentrated lactoserum (Locatim®) to prevent neonatal diarrhoea. The administration of
Locatim® did not significantly affect the incidence, duration or severity of diarrhoea. Serum
IgG concentrations of control animals did not differ significantly from treated groups. Only
the concentrations of IgG specific to E. coli CS31A strain were significantly higher in treated
animals compared to the control group. The absence of significant effect of Locatim® can be
explained by the high prevalence of Cryptosporidium parvum in studied farms and the
adequate immunity transfer observed in most calves.
In conclusion, beef cows produced a high quality colostrum regardless of breed or parity.
Under field conditions, the use of Brix and clinical refractometers allows a quick, easy and
reliable evaluation of colostrum quality and TCI. Refractometers have proved to be effective
tools which can be easily used for implementing TCI management program. The use of a
concentrated bovine lactoserum such as Locatim® is not justified when adequate TCI is
observed or when neonatal diarrhoea is caused by pathogens against which lactoserum is not
effective. The use of such lactoserum is therefore justified when specific antibodies contained
in Locatim® can be effective in farm conditions.
The study opened numerous perspectives both from practical and theoretical points of view. A
large scale field assessment of colostrum quality and TCI in Belgian Blue cattle but also in
other beef breeds would allow estimating the current situation and identifying the main factors
which may influence colostrum quality and TCI. The joint assessment of colostrum quality
and TCI is currently possible with a single type of refractometer but the development of other
applications would increase the interest for using such tool in practice. The development of
more efficient colostrum replacers and supplements would pave the way to an interesting
alternative in case a high quality colostrum is lacking in a farm.
