Livestock Research for Rural Development 23 (7) 2011 Notes to Authors LRRD Newsletter

Citation of this paper

Gastrointestinal parasite egg counts of Bos taurus x Bos indicus cattle in a dual-purpose system in the Mexican tropics

M M Osorio-Arce and J C Segura-Correa*

Campus Tabasco, Colegio de Postgraduados, H. Cárdenas, Tabasco, México
* Facultad de medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Mérida, Yucatán, México


The objective of this study was to estimate the egg counts of gastrointestinal nematodes in a dual-purpose cattle system in the tropics of Mexico and to determine the effect of some environmental factors on them. One-thousand-one-hundred-seventy-eight parasite egg counts from 503 calves were obtained.

The overall mean number of parasite eggs per gram of feces (EPG) was 1131.3 eggs. A mixed linear model was used to test the effect of year of birth of the calf (1995,…2006), season of birth (dry, rainy and windy), stage of growth (1-120 days, 121-180, 181 to weaning) and sex (male, female) on parasite burden = log10 (EPG+10). Year had a significant (p<0.05) effect on EPG counts. The parasite load for the dry (2.16) and rainy (2.18) seasons were significantly (p<0.05) higher than those for the windy season (2.10). Younger calves (birth to 120 days) tended to have more EPG than the calves greater than 180 days of age. The least squares means for the three stages of growth were 2.16, 2.20 and 2.08. There was no difference between male and female calves. The results suggest that diets that cover the nutrients requirements of calves under dual-purpose cattle systems could be an alternative to parasite control through increasing their resistant.

Keywords: Gastrointestinal parasites, Mexico, tropics, dual purpose


Infections with gastrointestinal nematodes are among the important factors limiting cattle productivity in the tropics of Mexico. Subclinical nematode parasitic infections cause great economic losses and these go unnoticed in cattle in rangeland. In dual-purpose cattle systems in the tropics of Mexico the calf has an important role in milk production and as a final product (Preston et al 1995). It is also known that calf weight affect survivability of the calf (basically in the early days), dam milk production and later performance (Stronbergh and Averbeck 1999). Growth is strongly affected by the consumption of milk by the calf (Combellas and Tesorero 2003, Sandoval et al 2005), because it affects the availability of nutrients, the development of the digestive tract and the appropriate development of the immunity system against some diseases such as parasitosis (Arrayet et al 2002, Coverdale et al 2004). Schottstedt et al (2005) mentioned that the parasite burden is influenced by the milk intake of the calf. On the other hand, Osorio-Arce and Segura-Correa (2005) observed that the preweaning growth rate of the dual-purpose calves could be explained in two stages: The first was the lineal growth or non ruminant stage, when the digestive tract and immune system is being developed and calves are susceptible to parasitosis.  

In dual-purpose cattle systems where the grass is the base of feeding, and where forages show seasonal and annual variation is expected to affect the growth of the calf (De las Heras-Torres et al 2008) and the incidence of parasites (Vázquez et al 2001). Parasites could be present all year round, causing problems in all stages of calf growth and their productivity, decreasing feed intake (Frish and Vercoe 1986).

The objective of this study was to assess the egg counts of gastrointestinal nematodes in a dual-purpose cattle system in the tropics of Mexico and to determine the effect of some environmental factors on them.  

Materials and methods

The study was carried out in the experimental farm of the Tabasco Campus of the Colegio de Postgraduados in Cárdenas, Tabasco, México. The climate of the region is tropical humid with temperatures varying from 16-21ºC in winter and 26-45ºC in spring and summer. The annual rainfall is 2500 mm (65% in summer and fall); and relative humidity from 70-100%. Three seasons are identified in the region: Dry (March to May) with rainfall less than 100 mm per month and high temperatures all day; as well as a poor development of pasture. The rainy season (June to October) characterized by high rainfalls, high temperatures and high grass production. The windy season (November to February) with sporadic rain, cold winds and low temperatures (mainly at night) and a slow growth of grass caused by the short photoperiod of this part of the year.  

A total of 503 ¾ Holstein ¼ Zebu calves (263 males and 240 females) belonging to the open nucleus crossbreeding system of the Tabasco Campus of the Colegio de Postgraduados (Osorio-Arce 2001) were sample from 1995 to 2006. Calves were under restricted feeding after milking (twice a day) and grazed in Star grass (Cynodon plechtostachius) paddocks. They have access to 1 kg/calf/day of an energy-protein supplement. Calves deparasitation was not practiced during the study. They were weighed approximately every 4 weeks from birth to weaning. Monthly fecal samples were collected per rectum for each animal. The McMaster technique was used to prepare the feces for quantification of worm eggs. Eggs per gram of feces (EPG) were counted in three stages of the calf growth: Stage I, from birth to 120 days; stage II, from 121 to 180 days; and stage III from 181 to weaning (around 244 days of age). 

Statistical analysis

Egg count data were transformed using log10 (EPG+10) to confer normality. The effects of year, season, sex, stage of development, and their simple interactions, as well as weight per age (weight/age in days) as a covariate on the transformed egg counts was determined using PROC MIXED for animal repeated measures (SAS 1990). 

Results and discussion

The overall egg per gram of feces transformed mean count was 2.18, which is equivalent to 1131 EPG. This is higher than the 500 EPG, the recommended minimum level for the treatment of nematodes in cattle. Year of birth of the calf had a significant (p<0.05) effect on egg burden; suggesting that management, feeding system or both is very important in the control of parasites (Eady et al 2003). Also as mentioned by Frisch (1981) a reduction in EPG is expected as a correlated response to selection for fast growth, as well as management improvement. Therefore year variation in EPG counts could be due to genetic and environmental factors. As observed in Figure 1, EPG counts were highest in 1996 and 1999, which may be due to changes in environmental conditions and management decisions in those years. Also the percentage of calves without worm eggs tended to increase in later years (Table 1).

Figure 1. Gastrointestinal parasite egg counts for calves in a dual-purpose cattle system in tropical Mexico.

Table 1. Number (percentage) of calves within categories of egg counts per gram of feces in a dual-purpose cattle system in the Mexican tropics.



Parasite egg counts per gram of feces

















    6(  5.8)


  9(  8.8)









  3(  4.0)





  3(  8.8)

  3(  8.8)

  2(  6.0)





  9(  8.9)








15(  9.6)

10(  6.7)





  3(  1.8)

  3(  1.8)

  4(  2.6)





  8(  8.5)

  0(  0.0)

  2(  0.2)





  7(  9.3)


  3(  4.1)






  4(  6.2)

  3(  4.9)







  2(  3.1)





  2(  5.7)


  0(  0.0)

Table 2. Overall least square means by stage of growth for the log10 of the number of eggs per gram of feces plus10, of calves in a dual-purpose cattle system in the Mexican tropics.

Stage of growth



Standard error

Birth to 120 days




121 to 180 days




181 to weaning




a,bMeans with different literals are different at P<0.05)

 The dry and rainy season had similar egg burden means (2.16+0.05 and 2.18+0.05, respectively) but higher than the value for the windy season (2.10+0.05, P<0.05). Therefore, farmers must be wary of clinical cases gastrointestinal infections in those seasons. Seasonal differences may be, in part, due to forage production and availability, and milk intake by the calf as mentioned by De Dios (2001) and Vázquez et al (2001).  Moreno et al (1984) and Morales et al (2001) mention that the most affected calves are the youngest ones, and as they grow they are more resistant to gastrointestinal parasites. However, in this study, the mean egg burden was lower for the > 6 months of age calves (Table 2). A better provision of nutrients for a growing calf could be a good alternative to increase parasite resistant and control parasitosis in dual purpose young cattle under tropical conditions. There were no differences between male and female calves in parasite egg counts (P>0.05). This disagree with the results of Frisch (1981) who found that female cattle were more resistant to parasites and had faster growth than males in the first growth stage, but grew slower in the second pre-weaning growth stage.



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Received 8 January 2011; Accepted 2 May 2011; Published 1 July 2011

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