Ingestion of foreign bodies in cattle is a pathological condition of economic importance which leads to severe economic losses as a result of high morbidity and mortality rates (Radostits et al. 2007; Ramin et al. 2008). Because of their indiscriminate feeding habits, cattle are known to ingest and, at times, choke because of ingestion of different types of indigestible materials referred to as foreign bodies (Baumont 1996). The ingestion of indigestible materials has been associated with feed scarcity (Igbokwe, Kolo & Egwu 2003).

Depending on the nature of the ingested foreign bodies and the diagnostic facilities, the detection of foreign bodies in ruminants’ stomachs is routinely accomplished by exploratory surgery and, occasionally, by ultrasonography (Radostits et al. 2007; Ramin et al. 2008; Semieka 2010). However, a number of cases are diagnosed by radiology and at necropsy (Mozaffari, Olomi & Vosough 2009; Nugusu et al. 2013; Ramaswamy & Sharma 2011). Because cattle do not use their lips for prehension, they are more likely to ingest foreign bodies than small ruminants as they are more likely to eat chopped feed in which foreign bodies may be incorporated (Westwood 2011). Studies have shown that the non-penetrating foreign bodies commonly recovered in bovine stomachs are plastic bags, sack thread, ropes, leather, rubber, bed linen, pieces of lead pipe, straw baskets, hair and plant fibres (bezoars) (Anwar et al. 2013). The major penetrating foreign bodies include metallic pieces of wire, needles, nails and stones (Kahn & Line 2010; Nugusu et al. 2013; Ramaswamy & Sharma 2011). Most of these foreign bodies were found mainly in the fore-stomachs and they are responsible for most pathological conditions affecting this area (Tehrani et al. 2012). The presence of foreign bodies in the fore-stomachs of ruminants has gained attention in recent years and is a subject of attention worldwide, as it results in reduced production and, in some cases, death of animals (Igbokwe et al. 2003; Ramprabhu, Dhanapalan & Parathaban 2003; Remi-Adewunmi, Gyang & Osinowo 2004). In developed countries, industrialisation and agriculture mechanisation have further increased the occurrence of foreign bodies in ruminants, whilst in developing countries the high rate of occurrence is associated with poor farming management (Misk, Ahmed & Semieka 2004; Semieka 2010).

Notwithstanding the availability of information on foreign bodies in different animal species from elsewhere (Abdullahi, Usman & Mshelia 1984; Igbokwe et al. 2003; Remi-Adewunmi et al. 2004), such information has never been published in Rwanda. As recently as 2005, the Government of Rwanda, through the Rwanda Environmental Management Authorities (REMA), has banned the use of plastic bags for packaging in retail shops (Republic of Rwanda 2005). No studies have been carried out on prevalence of foreign bodies in cattle or the effects of the plastic ban on the environment and, consequently, on animal production and food security in Rwanda.

The objectives of this study were: to determine the occurrence of the foreign bodies in cattle; to describe the nature and patterns of occurrence of the various foreign bodies found in the stomachs of the cattle; to localise the foreign bodies in the various chambers of the stomach; to correlate the incidence of the foreign bodies with the body condition of animals; and to correlate the frequency of foreign bodies with animal factors such as age, breed and gender.

Ethical approval (by official confirmation notice) for this study protocol was obtained from the Institutional Review Board of the School of Animal Sciences and Veterinary Medicine, College of Agriculture and Veterinary Sciences, University of Rwanda. The stomach examination procedures were performed by a qualified veterinarian assisted by meat inspectors through routine ante- and post-mortem inspection aimed at ensuring personnel safety. Slaughterhouse owners were informed about the study purpose and procedures and provided written consent prior to study procedures being carried out on their animals.

All the data used in this paper were collected by well-trained investigators. Examinations were done in accordance with animal welfare as well as occupational health and safety guidelines as defined by Rwanda Veterinary Services. All the foreign bodies were identified with certainty, indicating that all the results presented in this manuscript are trustworthy.

This study revealed an overall occurrence of 17.4% of foreign bodies, which consisted mainly of plastics, in the stomachs of cattle slaughtered at Ngoma slaughterhouse in the Eastern province. These results are similar to those of Ramaswamy and Sharma (2011), in a study based on exploratory ruminotomy carried out in Ethiopia.

Because cattle have a poor selective grazing adaptation (Westwood 2011), a prevalence rate of 17.4% in this study is not extraordinary and a lower prevalence of 6.1% reported by Fromsa and Mohammed (2011) in small ruminants in Ethiopia is not difficult to understand. Nearly similar prevalence rates of 8.9% and 11% were reported in sheep and goats by Hailat et al. (1997) and Hailat et al. (1998) from Jordan. However, higher prevalence rates reported previously in small ruminants have been explained by the fact that in desert countries, farmers live closely with their animals. As a result, the animals frequently eat household waste and graze very close to the homestead and are thus exposed to a higher risk of ingesting indigestible materials (Ghurashi et al. 2009; Hayder, Bakhiet & Mohammed 2006; Igbokwe et al. 2003; Tiruneh & Yesuwork 2010).

The differences in prevalence rates observed in female (20.0%) and male (15.7%) cattle have also been reported by Tiruneh and Yesuwork (2010), who concluded that the higher prevalence rates of foreign bodies in female cattle were a result of the effect of drought on the production stages of the females that occurred in the year of their study. They alluded to the fact that pica, which caused the animals to pick up strange objects as food, is normally more frequent in pregnant than in non-pregnant animals. In our study, the higher prevalence in female cattle may be explained by the fact that females generally have a longer lifespan than males, as livestock farmers normally do not sell females because they reproduce and increase the herd size. In addition, beef cows in Rwanda are also milked and therefore spend more time around the homestead – this generates higher exposure to domestic foreign bodies. The difference in prevalence rate in the present study was not statistically significant.

In this study, older animals and animals with poor body condition were found to be most affected with indigestible foreign bodies. This scenario has also been reported previously (Fromsa & Mohammed 2011; Hailat et al. 1997; Hailat et al. 1998; Tesfaye & Chanie 2012; Tiruneh & Yesuwork 2010; Vanitha et al. 2010). It is impossible in the current study to conclude whether the foreign bodies caused the loss of weight in animals or that animals in poor body condition were likely to have pica and hence pick up strange objects as a result. The finding of more foreign bodies in older animals may be a result of the gradual accumulation of indigestible materials ingested over a prolonged period of time. It is equally possible that animals are in poor body condition as a result of ingestion of indigestible plastics that interfere with food digestion and absorption.

The more frequent occurrence of rumen and reticulum impaction in emaciated and thin animals might be attributed to the interference of the foreign body with the absorption of volatile fatty acids, causing reduced weight gain. The results of this study are in agreement with those of Tesfaye and Chanie (2012) in Jimma, South-west Ethiopia and Fromsa and Mohammed (2011) in East Shoa, Ethiopia.

Semieka (2010) in Egypt used radiography and found out that needles and nails were frequent. Fromsa and Mohammed (2011) recovered plastic, leather, wire and hairballs in buffaloes and cattle. Hailat et al. (1997) also recovered such indigestible foreign bodies as plastic bags, pins, nails, hairballs, ropes and leather. In this study plastic, hairballs, ropes, stones, needles, keys, nails, plastic bags and wire were recovered from the stomachs of cattle. This is not surprising, as these objects are in common usage in Rwanda. However, in the present study, cassette ribbons, which have not been reported previously in literature, were also observed.

The recovery of plastics as the most prevalent foreign body is as worrying as it is puzzling. Recently, the Government of Rwanda – through the REMA – banned the use of plastic bags in retail shops (Republic of Rwanda 2005). Rwanda is a country with a high population density, where man and animals are forced to share the limited space; animals graze where man carries out his activities of daily living. A scene of livestock grazing along roads and alleys full of plastics is not uncommon along major roads such as the Ngoma–Kigali or Kigali–Nyagatare roads in Rwanda. In fact it is not uncommon to witness a goat, sheep or cow actually chewing a plastic sheet. According to the Holland and Kezar (1995), foreign bodies may usually be found in the zones of strong human concentration (cities) in the cattle-breeding areas, around schools, dwellings, along the roads and in the market, where one finds the sachets, food bags, the pieces of fabric and scrap materials. They further state that the circumstances of ingestion of the foreign bodies can result from carelessness, when people dispose of indigestible materials on animal pasture or in the vicinity of the animals. Occasionally, when the animal body is deprived of certain nutrients, animals have a tendency to eat anything within their reach (pica).

Because of the issues discussed, the high incidence of plastics in the fore-stomach is hardly surprising. The fact that this scenario comes on the heels of the government-gazetted plastic paper bag ban may mean that the ban is not showing any positive results. However, the non-biodegradability of plastics may mean that the same plastics that were already present in the older animals are still there. Although it cannot be concluded that the present study has shed any light on the impact of the plastics ban by government, it is important to note that no such information has ever been published in Rwanda. It therefore warrants a wider follow-up assessment study of the effects of the plastic paper ban on the environment in Rwanda. If such follow-up studies could be carried out, then these results can serve as baseline information for comparison with their results.

The recovery of most foreign bodies in the rumen is also not surprising, as it has been reported previously in small ruminants (Fromsa & Mohammed 2011; Hailat et al. 1997; Igbokwe et al. 2003; Remi-Adewunmi et al. 2004; Tiruneh & Yesuwork 2010) and in buffaloes (Khan, Habib & Siddiqui 1999). This may be because almost all ingested feed goes to the rumen and most indigestible materials do not progress to other stomach chambers.

Furthermore, the sheep and goats slaughtered at Addis Ababa Abattoir cohabit with the traders for days and weeks before getting sold and may be exposed to grazing on garbage contaminated with plastic bags. Remi-Adewunmi et al. (2004) had reported a much higher prevalence rate (97%) in sheep and goats brought from urban areas of Nigeria for slaughter. Hayder et al. (2006) had also retrospectively studied the occurrence of foreign bodies in goats from Khartoum state and reported a prevalence of 52.9% in 2000 and 33.3% in 2001.

The findings of this study indicated that littering the environment with plastic bags and other indigestible materials could pose health problems for free-ranging cattle unless people reduce disposal of plastics on pastures and begin to practise routine picking up and disposal of plastics from animal pastures. This study showed that there is association between age and prevalence of foreign bodies. More foreign bodies were found in the rumen (82%) than in the other compartments. This study revealed an overall prevalence of 17.4% of foreign bodies in the stomach.

One can conclude that there is a high prevalence of foreign bodies in cattle from the largely rural districts of Ngoma. One can only extrapolate that cattle in larger urban centres, such as Kigali and Musanze, where there are higher population densities, could have a much higher occurrence of foreign bodies. It has been highlighted by previous researchers that the presence of large numbers of foreign bodies in animals interferes with digestion and affects animal productivity. It is therefore reasonable to conclude that food security in Ngoma and, perhaps, in Rwanda, is threatened by plastic pollution. Whether the problem of foreign bodies in cattle in Rwanda is increasing or decreasing, only time and follow-up studies will tell.