Calf health and growth in small-holder dairy farms in Tanzania

Jelly Senyagwa Chang'a, Olav Reksen*, Torleiv Løken* and Robinson Mdegela**

Livestock Research Centre, Ministry of Livestock Development,
P.O. BOX 561, Tanga, Tanzania.
jelhas2002@yahoo.co.uk
JellySenyangwa.Chang'a@stud.nvh.no
* Department of Production Animal Clinical Sciences, Norwegian School of Veterinary Science,
P.O. BOX 8146 Oslo, Norway.
** Department of Veterinary Medicine and Public Health, Faculty of Veterinary Medicine,
Sokoine University of Agriculture, P.O. BOX 3021 Morogoro, Tanzania.

Abstract

A longitudinal observational study on calf health and growth was conducted in smallholder dairy farms in Mvomero and Njombe districts, Tanzania to investigate whether calf growth in these regions was predominantly affected by clinical diseases or other factors. The clinical health and growth of 156 calves from 121 farms were monitored for one year. Routine clinical examinations and bodyweight measurements were conducted by the same veterinarian at each of four visits to the study farms. Blood and faecal samples collected at each visit were screened for haemoparasites and gastrointestinal parasites.

Calf mortality was 7.7 % and clinical signs of disease were observed in 5.7 %. Coccidial oocysts and nematode eggs were detected in 24.8 % and 14.8 % of 496 faecal samples, respectively, and haemoparasites in 16.9 % (n=498). Mortality, together with nematode and coccidial infections, were significantly associated with district and month of study. Bodyweight gain per week ranged from -2.2 – 7.2 kg (mean 2.1, SD 1.5) in female calves and -1.8- 8 kg (mean 2.3, SD 1.5) in male calves. An extended period of impaired bodyweight gain from birth to weaning was observed. Mean body condition score was 1.8. Although the overall prevalence of clinical disease was low, calf growth rate was impaired. Inadequate feeding was considered the major factor for this observation and therefore it is recommended that calves are provided with nutritionally appropriate feed in order to attain adequate growth performance.

Key words: Body weight gain, body condition score, diseases

Introduction

Sustainability of a dairy production system depends on good herd management. Calf rearing is essential as it represents future replacement stock. Calf diseases have been reported to be among the major constraints for dairy production and expansion (Gitau et al 1994; Ehui et al 1995). The economic impact of diseases could be direct (deaths), or indirect, through decreased productivity and increased treatment expenses. The major causes of death in dairy calves in Tanzania and other parts of Africa have been reported to be various diseases including gastroenteritis due to coccidiosis, salmonellosis, helminthiases and cryptosporidiosis, tickborne diseases (East Coast fever, babesiosis, anaplasmosis and heartwater disease), and trypanosomosis (Chibunda et al 1997; Keyyu et al 2005; Swai et al 2007; Kivaria and Noordhuizen 2009; Nonga and Kambarage 2009). 

Appropriate nutrition is fundamental for calf growth, and for the general profitability of calf rearing enterprises (Lanyasunya et al 2006). In Tanzania, where calf feeding regimes depend primarily on tropical grasses, it is difficult for calves to obtain a balanced nutrient supply, as most of the available natural forage has low digestibility due to relatively late harvesting during maturation, and low crude protein and mineral content (Mero and Uden 1998; Mtengeti et al 2008). In pre-weaned dairy calves, solid feed intake, especially of a high carbohydrate diet, stimulates rumen microbial proliferation and volatile fatty acid production. This enhances initiation of rumen development (Baldwin et al 2004; Kehoe et al 2007), which, in turn, facilitates growth (Lanyasunya et al 2006). 

Analysis of growth patterns is useful for determining the relative importance of factors that may affect production efficiency. Under normal circumstances, calf growth has been shown to be elevated during the first weeks of life, and then decline around weaning (Menchaca et al 1996; Bar-Peled et al 1997). Body condition score (BCS) is a subjective measure of nutrient reserve, and changes in calf BCS can be used as a practical indicator of nutritional status (Waltner et al 1993).  

Calves in most smallholder dairy farms in Tanzania do not perform well, and most farmers have limited knowledge on proper calf feeding regimens (Chang’a et al 2010). As few studies on calf health and growth in smallholder farms in Tanzania have been published, the objective of this study was to evaluate the health status and growth of the young calves in smallholder dairy farms. By identifying those factors that have the most impact on calf health and growth, preventive measures could be implemented that have the most effective cost benefit for the farmers.  

Materials and methods

Study area

The study was conducted in 13 villages in the districts of Mvomero in Southeastern Tanzania, and Njombe in the Southern Highlands of Tanzania. Further details of the study sites have been published (Chang’a et al 2010).   

Animals

The study involved an open population. At the beginning/first visit, we started with 123 calves of day one to five months of age. New born calves were entered in the subsequent visits given total of 156 calves from 121 smallholder dairy farms, 72 from Mvomero and 84 from Njombe. The calves were crossbred Friesian or Ayrshire and Tanzanian Short Horn Zebu, and up to 57 weeks of age. Farms were visited by the study veterinarian every two months, with a total of four visits to each farm. All animals were ear tagged when first included in the study.

Calf examination 

At each visit, the body weights (BW) of the calves were estimated using a heart girth measuring tape. The variable BW gain was obtained as the difference in BW between two consecutive visits. BCS for each calf was derived according to the method described by Wildman et al (1982), which consists of a 1-5 scale, with 0.5 point increments. Date of birth, sex and the use of gastrointestinal parasites drugs as a control measures were recorded. The health status of the animals was assessed by routine clinical examination at each visit and all animals showing signs of impaired health were recorded, along with clinical symptoms. In cases of calf death, the most probable cause was identified either by the farmer or the study veterinarian.

Sample collection and examination

The material consisted of 1-4 samples from each of 156 individual calves, some calves were withdrawn from the study at some point due to death and trading given a total of 496 samples. Faecal samples were collected from the rectum of each calf using disposable gloves. These were stored in a cool box with ice packs during the 1-2 days transportation to the laboratory. Nematode egg and coccidial oocyst concentrations were estimated using a modified McMaster technique (Anonymous 1986). Briefly, 3 g of faeces were homogenized in 42 ml of flotation fluid (saturated sodium chloride). The faecal suspension was passed through a tea trainer to remove coarse material. After thorough mixing, two chambers of a Universal McMaster slide were filled and all eggs and oocysts under the grids (total volume 0.3 ml) counted at x40 magnification. The numbers of eggs and oocysts counted were multiplied by 50 to provide an estimate of the eggs/oocysts per gram (epg/opg) faeces. 

Cryptosporidium spp oocysts were detected using the modified Ziehl-Neelsen staining technique as described by Henriksen and Pohlenz (1981). The suspected positive samples in Z-N were retested using fluorescein-labeled (FITC) monoclonal antibody (A 100FR FL from Waterborne Inc., New Orleans, USA) for conformation.

Blood was collected from the jugular vein using heparinized tubes. Thin blood smears were made, air-dried, fixed with absolute methanol, stained with 10% Giemsa solution for 30 minutes, washed with tap water, air-dried and examined by microscopy at x100 magnification for haemoparasites.

Statistical analysis

The statistical software package, STATA 12 (Stata Corp LP, Texas) was used for the statistical analyses. Differences in the prevalence of diseases, parasitic infections, and calf mortality for each sex, season of birth, and district (Mvomero versus Njombe) were compared by chi-square tests.

To assess the relationships between BW and age in weeks, a second order polynomial function was used as the growth curve representation with the logarithmic transformed values of BW (kg) as the outcome variable. The relationships between the two outcomes; BW change and BCS, and the explanatory variable, calves’ age in days, were both represented by third order polynomial functions. Repeat measures within calves were accounted for by including calf ID as a random effects variable in all models. The explanatory variables of sex, season of birth and district were initially employed in all models, but omitted for no significance using the backwards elimination procedure. 

Results

Disease prevalence and mortality

Of 156 calves, only 9 (5.7%) were diagnosed as being clinically diseased at one or more of four visits. Gastrointestinal disorders were found to be most frequent (2.7%). Other disorders include pneumonia (0.6%), photosensitization (0.6%), eye infection (0.6%), anaemia (0.6%), and recumbency of unknown cause (0.6%). Haemoparasites were detected in 84 (16.9%) of the 498 blood samples. Theileria spp (15.9%) were the most prevalent haemoparasite, followed by Babesia spp (0.8%), and Trypanosoma spp (0.2%). None of these infections were related to month (P=0.13) or district (P=0.95), but there was borderline association (P=0.08) with age. Younger calves were more likely to be infected. No association was detected between haemoparasitic infection and clinical disease (P=1.0). Out of 84 samples detected with haemoparasites, only two had clinical disease.  

The concentrations of helminth eggs and oocysts in the faecal samples was generally low with most positive samples having less than 500 oocysts (61%) or eggs (86%) per gram. Of the positive samples, only 11 (9%) had over 2000 oocysts per gram, and only 2 (3%) had over 2000 helminth eggs per gram. Coccidial oocysts were detected in 24.8% of the 496 faecal samples analysed. The infection was related to district (P=0.005), borderline to months (P=0.06), but appeared not to be affected by calf age (P=1.0). More coccidian positive samples were found in Mvomero than Njombe and most positive samples were collected between August-October. No association between coccidial infection and clinical disease in the calves could be identified (P=1.0). Out of 123 samples detected with coccidial oocysts, only one had clinical disease. Gastrointestinal nematode eggs were detected in 14.8% of the 496 faecal samples analysed. Infection with gastrointestinal nematodes was related to months (P=0.04) and districts (P=0.003), but was not associated with age (P=0.99). More nematode positive samples were found in Mvomero than Njombe, and most positive samples were collected between August-October. Out of 74 samples detected with nematode eggs, only one had clinical disease (P=1.0). Mixed intestinal infection with both coccidia and nematodes was observed in 6.8% of the samples. Most farmers treated their animals against gastrointestinal parasites every third month. Thirteen (2.6%) samples were suspected as Cryptosporidium positives in Z-N staining; however, on confirmatory test none was found to be positive.

A total of 12 (7.7%) calves died during the study period, 8 (67%) from Mvomero and 4 (33 %) from Njombe (Table 1). The causes of death, as perceived by the farmers, included one case of each of the following: East Coast fever, anaplasmosis, diarrhoea, paralysis, sudden death, accident, and dog bite. Furthermore, two calves died from pneumonia and three of unknown causes. Death was related to district (P=0.045) and borderline related with months (P=0.06) (Table 1).  

 Body weight

The measures for weekly BW gain in heifer calves ranged from -2.2 to 7.2 kg (mean 2.1, SD 1.5), and from -1.8 to 8.1 kg (mean 2.3 kg, SD 1.6) in male calves (Table 2). The third order polynomial model which shows the relationship between BW gain and age is displayed in Table 2 and Figure 1. Median age at weaning was 16 weeks (mean 16.0 weeks, SD 3.7). 

Figure 1.  Weekly body weight gain by age in male (--■--) and female (--▲--) calves (n = 156) on 121 smallholder dairy farms, Tanzania. A third order polynomial function was observed. Adjustment for repeated measures within calves was used in STATA 12

 Body condition score

 The relationship between BCS and age was found to be significant (P<0.005) (Table 3, Figure 2). Body condition score decreased from 1.85 at birth to 1.75 at 25 weeks of age, and then rose with further animal maturation.  

Figure 2. Body condition score by age in male (--■--) and female (--▲--) calves (n=156) on 121 smallholder dairy farms in Tanzania. A third order polynomial function was observed. Adjustment for repeated measures within calves was used in STATA 12

Discussion

The findings in this study do not support the supposition that diseases are a primary cause for growth retardation in crossbred calves at these study sites in Tanzania, as only a small proportion of calves were diagnosed with clinical signs of disease during the four herd visits. Although both haemoparasites and intestinal parasites were diagnosed relatively frequently, their occurrence was not apparently related to clinical disease. However both egg counts and coccidial oocyst counts were relatively low and it is possible that non-pathogenic coccidia predominated. The low gastrointestinal parasites counts could be attributed to frequently use of parasite prophylactic drugs. Additionally, cryptosporidiosis was found not to be a problem in these herds. Thus, the sub-optimal growth rates appear to be due to a non-infectious, chronic problem.  

We hypothesize that inadequate feeding regimes, rather than diseases, probably had a greater impact on calf growth. In this study, a long period of declining weekly BW gain after birth to weaning was observed, which differs from the normal profile of BW gain as described by Menchana et al (1996). This indicates problems related to nutrition, specifically during the period of conversion from milk feeding to rumination. Lyimo et al (2004) reported that most farmers in Tanzania introduce forage as late as at the 4^th week after birth, and provided little supplement to their calves after weaning. Inadequate supplementation with solid feed to calves that are growing rapidly during the pre-weaning period, results in delayed ruminal development and growth (Khan et al 2007), and probably contributes to a decline in body weight gain, as observed during this study. During the weaning period, animals may display low or negative daily gain, and the current study identifies this period as being particularly critical for achieving optimum growth. If solid feed intake can be encouraged during the milk feeding period, then it has been suggested that the decrease in growth rate before and around weaning will be less severe (Forbes 1986). A similar pattern of decline of daily BW gain from birth to weaning has previously been reported by Das et al (1999) in Tanzania, supporting our suggestion that natural pasture in this area of the tropics does not provide adequate nutrients for optimum growth of calves.

High growth rate during the post weaning period was expected, due to compensatory gain, a phenomenon demonstrated by Choi et al (1997) in 6-month old Holstein heifers subjected to a step-growth pattern. Greater nutrient demands, because of higher BW and increased size of digestive organs, trigger hyperphagicity in calves after weaning (Bøe and Havrevoll 1993). A point of maximum BW gain, as observed around the age of 40 weeks, has also previously been described for the tropical Brahman breed (Menchaca et al 1996), but the point of inflection was considerably earlier than in the present investigation. This was possibly due to a difference in the quality of feed available to the calves.

In the tropics, reliance on low quality pasture grass alone does not result in good rumen development in calves (Mbwile 1990), and this may have resulted in the retarded calf growth observed in the current study. In Mvomero, most natural grasses and crop residues have low crude protein and mineral content, and are of poor digestibility (Mtengeti et al 2008) and thus do not reach the requirements needed for optimum growth in the calves. Additionally, in this study area, as in most rural areas in Tanzania, it is unusual to use concentrates for feeding calves (Lyimo et al 2004) due to reasons of economy and erratic supply, and this lack would also result in poor growth rates of the calves. Increases in calf BW gain following improvements in nutritional regimen have been demonstrated by several authors (Baldwin et al 2004; Lanyasunya et al 2006), and it is well established that for optimum calf growth, good quality roughage should be provided prior to weaning.

An increase in mortality rate and the occurrence of intestinal parasites occurred between August and October. This is the peak of the dry season in this area, when the availability of animal feed, in terms of both quality and quantity, is low (Mussa 1998). Inadequate feeding during this period, along with high ambient temperature, may result in a reduction in nutritional status and decreased resistance to disease (Radostits et al 1994).

The higher mortality and parasite burden in Mvomero than Njombe were probably due to differences in experience in rearing dairy cows (Urio et al 2006). Inhabitants of Mvomero are traditionally crop growers with relatively little experience in rearing dairy cows, while farmers in Njombe have a long tradition of keeping dairy cows.

Conclusion

Growth rates of calves on smallholder dairy farms in Tanzania were low. This seemed to be related to inadequate nutrition rather than diseases. Additional management options should be explored in this system with particular focus on improving feed quality, especially in pre-weaning and weaning periods, as these seem to be problematic stages. Treatment for helminths and coccidial infections might be most strategically administered after the end of the rainy season as this period showed the highest infestation rate. 

Acknowledgements

The financial support given by the Norwegian Government through the PANTIL project at Sokoine University of Agriculture is gratefully acknowledged. We also acknowledge the cooperation from dairy farmers participating in the study and field officers in Mvomero and Njombe districts.

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Received 29 May 2011; Accepted 9 June 2011; Published 1 July 2011

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