Livestock are a source of high-quality protein (meat, milk and eggs) and also contribute to the economic welfare of people by providing hides, skins, fertiliser, and power and traction for agricultural purposes, increasing the productivity of smallholdings (Torr et al. 2003). They are also a ‘living savings bank’, serving as a financial reserve for periods of economic distress and crop failure and as a primary source of cash income (International Livestock Research Institute 1999). However, indigenous livestock in Ethiopia have not been fully exploited due to their lower productivity, the main reasons for this including poor nutrition, disease and poor genetic make-up. Ingestion of indigestible foreign bodies is mainly associated with nutritional deficiencies, environmental pollution and poor feeding management, and causes various problems in the rumen and reticulum of ruminants (Jones, Hunt & King 1997). Harmful effects include reduced feed intake, failure to absorb volatile fatty acids, reduced rate of weight gain, internal injury and death following obstruction of the intestinal tract (Igbokwe, Rolo & Egwu 2003; Radostits et al. 2007). Nonmetallic indigestible foreign bodies in the reticulorumen cause recurrent rumen tympany in adult dairy cattle (Vanitha et al. 2010).

Ruminants reared in urban and sub-urban areas may be exposed to indigestible materials such as plastic, leather and metal. These may cause impaction, ultimately with interference of the flow of ingesta leading to rumen distension and the absence of defaecation (Abdullah, Usman & Mshelia 1984; Igbokwe et al. 2003; Remi-Adewunmi, Gyang & Osinowo 2004). In Jordan an estimated loss of $25 million in ruminant productivity and health associated with plastic impaction was reported (Hailat et al. 1996).

In Ethiopia the occurrence of foreign bodies in ruminants has been investigated and reported in the Amhara region (Sheferaw et al. 2014), at Jimma municipal abattoir in southwestern Ethiopia (Tesfaye, Yismaw & Demissie 2012b), in eastern Ethiopia (Tesfaye et al. 2012a), at Lunna export abattoir in East Shoa (Abebe & Nuru 2011), and at Addis Ababa municipal abattoir (Roman & Hiwot 2010). The objective of the present study was to estimate the prevalence and types of foreign bodies commonly encountered in cattle, sheep and goats slaughtered at Haramaya University and Haramaya municipal abattoirs in Oromia Regional State, an area of Ethiopia not previously investigated. Results were compared with those of other Ethiopian studies as well as similar studies done in Jordan (Hailat et al. 1996), Nigeria (Abdullah et al. 1984; Igbokwe et al. 2003; Remi-Adewunmi et al. 2004) and India (Vanitha et al. 2010).

This study showed an overall foreign body prevalence of 52.1% (422/810) in ruminants slaughtered at Haramaya municipal and Haramaya University abattoirs. This finding is far higher than the reports of Sheferaw et al. (2014), Tesfaye et al. (2012a, 2012b) and Roman and Hiwot (2010) in other regions of Ethiopia, where the prevalence was 41.8% (167/400), 23.9% (92/384), 9.2% (53/576) and 44.6% (311/697) respectively. These differences in the prevalence of foreign bodies between various areas may be attributed to differences in animal management systems and the extent of foreign body management both in the rural and/or urban areas and in the grazing areas. The higher prevalence of foreign bodies in the current study area is probably related to the unrestricted and increased use of plastic bags and their improper disposal. Ingestion of foreign bodies is associated with a shortage of forage (Hailat et al. 1996) as well as increased pollution of grazing lands with indigestible materials (Tesfaye et al. 2012a). If owners do not provide supplementary feed during feed shortages, their animals are likely to face a negative energy balance that will force them to ingest unusual materials including plastic, cloth, rope and even metallic objects (Hailat et al. 1996).

According to Remi-Adewunmi et al. (2004) the occurrence of foreign bodies in sheep and goats is higher within and at the outskirts of urban areas. In the present study area the animal owners let their animals move freely to forage on the highly polluted road verges. The agricultural land in the area is largely occupied by perennial crops like the narcotic ‘chat’, which leaves reduced grazing land available for livestock. These factors increased the chance of foreign material ingestion.

The prevalence of foreign bodies observed in cattle (43.4%) was in approximate agreement with the report of Sheferaw et al. (2014), who reported 41.8% in cattle from the Amhara region of Ethiopia. The prevalence of foreign bodies was significantly (χ² = 17.53, p < 0.05) higher in sheep (59.3%) and goats (56.7%) than in cattle (43.4%), but there was no significant difference between sheep and goats. This finding was inconsistent with those of Sheferaw et al. (2014), who reported 41.8% (167/400) in cattle, 20.6% (66/320) in sheep and 11.9% (38/320) in goats. The absence of significant differences in the prevalence of foreign bodies in sheep and goats is in agreement with the report of Abebe and Nuru (2011), who reported 7.55% (29/384) in sheep and 4.68% (18/384) in goats.

Plastic was the most commonly encountered (79.2%) foreign material in all study animals, followed by cloth (15.3%) and rope (12.3%). This finding is in general agreement with various reports from different areas of Ethiopia (Abebe & Nuru 2011; Roman & Hiwot 2010; Sheferaw et al. 2014; Tesfaye et al. 2012b), Nigeria (Igbokwe et al. 2003; Remi-Adewunmi et al. 2004) and Jordan (Hailat et al. 1996). This indicates the widespread use of plastic bags in these areas and environmental pollution due to their improper disposal.

In all of the ruminants more foreign bodies occurred in the rumen alone (87.9%) than in the reticulum alone (5.0%). Significantly higher proportions of foreign bodies were observed in the rumen of cattle (χ² = 332, p< 0.05), sheep (χ² = 193, p< 0.05) and goats (χ² = 285.0, p= 0.000) than in the reticulum. This finding was in general agreement with the findings of Abebe and Nuru (2011), Roman and Hiwot (2010) and Tesfaye et al. (2012b), and may be attributed to the larger rumen volume, the cumulative size/s and material composition of the foreign bodies, and the types of materials, with metals and sharp objects tending to localise preferentially in reticulum (Radostits et al. 2007).

Overall the prevalence of foreign bodies in study animals with poor body condition of 71.4% (10/14) was significantly higher (χ² = 38.57, p < 0.05) than in those with medium (56.4% or 377/668) and good body condition (27.3% or 35/128). This finding is in agreement with the reports of Abebe and Nuru (2011) and Hailat et al. (1996). However, the total number of study animals in poor condition was small at 1.7% (14/810). The majority of animals with foreign bodies were in the medium-condition group (82.4% or 668/810 of the animals examined, with 56.4% [377/668] having foreign bodies), whilst 15.8% (128/810) of animals were in good body condition and 27.3% (35/128) of these were also positive.

Accumulations of indigestible foreign bodies in the rumen interfere with the flow of ingesta (Igbokwe et al. 2003) and with absorption of feed. These effects most likely contributed significantly to animals being in poor body condition, and may have played a significant role in preventing a percentage of those in medium body condition who had foreign bodies from attaining good body condition, and thus causing their owners to incur significant financial losses.

The prevalence of foreign bodies observed in the rumen and reticulum of Ethiopian cattle, sheep and goats presenting at the Haramaya University and Haramaya municipal abattoirs was high at 52.1%. The study showed that improper disposal of and pollution of the environment with indigestible materials like plastic, cloth, metal, rope and stone could pose serious health risks for free-grazing ruminants. Amongst the foreign bodies observed, plastic bags constituted the majority. Based on the results obtained, the use of biodegradable paper bags could be encouraged whilst the community is educated in the principals of re-use, recycling and responsible waste disposal that will not put the environment and animals at risk.

Livestock professionals and environmental activists are the key actors in educating the community on the risk of improper disposal of plastic and other indigestible materials in an ecosystem where free communal grazing of animals is practised. Policy makers are also expected to formulate a legally binding regulatory framework towards reducing environmental pollution and also on the extent to which the free-grazing system is practised.