A STUDY OF ASSOCIATION BETWEEN ELISA RESPONSE TO INFECTIOUS DISEASE AGENTS AND CALVING INTERVAL IN CATTLE IN THE TROPICS OF MÉXICO

ESTUDO DA ASSOCIAÇÃO ENTRE RESPOSTAS AO ELISA FRENTE A INFECÇÕES E INTERVALOS ENTRE PARTOS EM BOVINOS

A STUDY OF ASSOCIATION BETWEEN ELISA RESPONSE TO INFECTIOUS DISEASE AGENTS AND CALVING INTERVAL IN CATTLE IN THE TROPICS OF MÉXICO.

ESTUDO DA ASSOCIAÇÃO ENTRE RESPOSTAS AO ELISA FRENTE A INFECÇÕES E INTERVALOS ENTRE PARTOS EM BOVINOS

José Alfonso Barajas-Rojas¹ Hans Riemann² Charles Franti³

SUMMARY

Forty eight cows of Holstein-Zebu crosses with at least one completed pregnancy were tested for antibodies to 20 disease agents. The testing was performed within one month (average two weeks) after calving when the IgG level constantly reaches its lowest value during the cows reproductive cycle. The results indicate that increasing levels of IgG against Leptospira interrogans serovar hardjo and Mycobacterium paratuberculosis may be associated with an increased calving interval. Increase in calving intervals could not be explained by age of cows or their genotypic characteristics.

Key words: infectious diseases, antibodies, calving intervals, México.

RESUMO

Quarenta e oito vacas cruzas Holandês-Zebu com pelo menos uma prenhez completa foram testadas para anticorpos contra 20 agentes infecciosos. O teste foi realizado dentro de um mês (média de 2 semanas) após o parto quando o nível de IgG alcança constantemente seu valor mais baixo durante o ciclo reprodutivo das vacas. Os resultados indicam que níveis crescentes de IgG contra Leptospira interrogans serovar hardjo e Mycobacterium paratuberculosis podem estar associados com um aumento no intervalo entre partos. Aumento nos intervalos entre partos não pôde ser explicado pela idade das vacas ou suas características genotípicas.

Palavras-chave: doenças infecciosas, anticorpos, intervalo entre partos, México.

INTRODUCTION

Little is known about subclinical infection as determined by antibody response and reproductive performance in cattle. ABBAS et al (1983) studied subclinical paratuberculosis in California dairy herds using ELISA and culturing. By matching cows within herds they demonstrated that subclinical paratuberculosis increased calving intervals on an average of 2 months. UHAA et al (1990) and AKHTAR et al (1990) doing cross sectional ELISA studies in large California dairy herds found suggestions of negative impact on reproduction performance associated with positive reaction to Mycoplasma bovis and Campylobacter fetus.

No studies seem to have done on impact of subclinical infections on reproductive performance of cattle in the tropics.

MATERIALS AND METHODS

The study was conducted with cattle at the Center for Research, Teaching and Extension in Tropical Livestock (Centro de Investigación, Enseñanza y Extension en Ganadería Tropical-ClEEGT) located in the North-central part of the state of Veracruz, México. The study area and the methods of ELISA have been described earlier (Barajas-Rojas et al, 1993a).

For the purpose of investigating association between antibody level (IgG) and reproductive performance ELISA was performed within a month (average two weeks) after calving and length of the subsequent calving interval was recorded. ELISA values obtained at different points of time may show considerable variations (BARAJAS-ROJAS et al, 1993a, 1993b, 1993c and 1993d) but the lowest values are consistently found shortly after calving and may provide the best basis for comparisons. The hypothesis is that the higher the ELISA value is shortly after calving the more likely it is that the cow has an active infection that may have a negative impact on conception when the cow is bred a few weeks later.

RESULTS

The overall results showing percent ELISA, calving intervals, genotype group and the age of cows are presented in table 1. The distribution of recorded calving intervals is shown in the histogram (Figure 1). Regression of calving interval on percent ELISA yielded no significant results which is not surprising since even the most promising plots (Leptospira interrogans serovar hardjo, Figure 2 and Mycobacterium paratuberculosis, Figure 3) do not indicate subpopulations with normal distribution and equal variances. The data were listed according to increasing calving interval as shown in table 1 and divided into four groups each with 12 cows. The groups are not mutually exclusive; group I represents calving intervals 11-14 months, group II 14 - 16 months, group III 16 - 18 months and group IV 18 - 33 months. This type of grouping was used because it was felt that calving intervals were not always recorded exactly to month.

The Kruskal-WaIlis one way analysis of variance by ranks was then performed on the four groups; the results are shown in table 2. The possibilities existed that differences in calving intervals may be due not to infectious agents but to age differences or differences between the genotypic groups of cows. Figure 4 shows a plot of calving intervals against age of cows at previous calving; there is no significant association (R² = 0.0003). A t-test on calving intervals of genotype groups 1 (50% Holstein, 50% Zebu) and 2 (75% Holstein, 25% Zebu) showed no difference between the two groups (95% confidence interval for difference in mean calving interval was -0.60 to 1.48).

DISCUSSION

The data presented here suggest that subclinical disease as reflected in increased ELISA values immediately after calving may have a negative impact on reproductive performance. The results obtained for Leptospira interrogans serovar hardjo make biological sense although they fail to reach the statistical significance. The results for Mycobacterium paratuberculosis although less convincing are in agreement with earlier findings in a different environment ABBAS et al (1983). It must be added that no clinical cases of leptospirosis or paratuberculosis have been reported in the study herd.

The number of cows which could be included in this study is small (48) and this may be a reason that the findings of AKHTAR et al (1990) and UHAA et al (1990) could not be confirmed. These authors did cross-sectional studies of several hundred California dairy cows and still did not get completely convincing results.

More studies, building on the experience of past studies, should be done in order to get a better evaluation of the impact of subclinical diseases.

ACKNOWLEDGEMENTS

We appreciate the assistance in sample collection and data collection of Dr. Eusebio Garcia Neria and Dr. Rebeca Acosta and personnel of the Centro de Investigación Enseñanza y Extensión en Ganadería Tropical-ClEEGT of the Faculty of Veterinary Medicine. National Autonomous University of Mexico, Mexico city.

²Doctor in Veterinary Medicine, PhD, Professor Dept of Epidemiology and Preventive Medicine, University of California, Davis, CA 95616, USA.

³Statistician PhD. Professor Dept of Epidemiology and Preventive Medicine, University of Califórnia. Davis, CA 95616. USA.

Recebido para publicação em 21.10.92. Aprovado para publicação em 07.04.93.

• ABBAS, B., RIEMANN, H.P. and HIRD, D.W. Diagnosis of Johne's Disease (Paratuberculosis) in Northern California cattie and a note on its economic significance. California Veterinarian n. 8, p. 20-24, 1983.
• AKHTAR, S. RIEMANN, H.P., THURMOND, M. C. et ai. The association between serological evidence of exposure to Campylobacter fetus and productivity in dairy cattle. Preventive Veterinary Medicine, v. 10, n. 1-2, p. 1-14, 1990.
• BARAJAS-ROJAS, J.A, RIEMANN, H.P. and FRANTI, C.E. Application of enzyme linked immunosorbent assay (ELISA) for epidemiological studies of diseases of livestock in the tropics of México. Rev Sci Tech Off Int Epiz, v. 12, n. 3, 1993a. In Press.
• BARAJAS-ROJAS, J.A., RIEMANN, H.P. and FRANTI, C.E. Serological screening for infectious cattle diseases I. Influence of reproductive status. Ciência Rural, v. 23, n. 1, p. 69-72, 1993b.
• BARAJAS-ROJAS, J.A., RIEMANN, H.P. and FRANTI, C.E. Serological screening for infectious cattle diseases II. Association between prevalence and level of ELISA response. Ciência Rural, v. 23, n. 2, p. 193-196, 1993c.
• BARAJAS-ROJAS, J.A., RIEMANN, H.P. and FRANTI, C.E. Serological screening for infectious cattle diseases. III. Choice of sentinel animals. Ciência Rural, v. 23, n. 2, p. 197-201, 1993d.
• UHAA, I.J., RIEMANN, H.P., THURMOND, M.C. et al. A Cross-sectional study off Bluetongue virus and Mycoplasma bovis infections in dairy cattle 2. The association between a positive antibody response and reproduction performance. Veterinary Research Communications, v. 4, n. 6, p. 471-480, 1990.

¹

Doctor in Veterinary Medicine, MSc, PhD, Professor Titular, Dept of Virology and Immunology, Faculty of Veterinary Medicine, National Autonomous University of México, Mexico City 04510, Mexico.

Publication Dates

• Publication in this collection
  03 Sept 2014
• Date of issue
  Dec 1993

History

• Accepted
  07 Apr 1993
• Received
  21 Oct 1992