Common Defects Found in Animal Hides and Skins

Animal hides and skins are the primary raw material for the global leather industry, but not every hide that enters a tannery leaves as premium leather. A single defect – a poorly healed wound, a botched flaying cut, or inadequate salting – can reduce a hide’s grade dramatically or lead to outright rejection. Research on crust leather quality shows that the overall rejection rate for hides and skins at tanneries can be as high as 32.7%, representing significant economic loss. Understanding where these defects originate – and how to prevent them – is essential for anyone working along the leather value chain.

How defects are classified 🔗

Defects in hides and skins are broadly classified based on when they occur. A peer-reviewed study published in the Onderstepoort Journal of Veterinary Research categorises them into three stages: pre-slaughter (ante-mortem), slaughter, and post-slaughter (post-mortem). Each stage introduces a distinct type of damage with different implications for leather quality. Pre-slaughter defects tend to affect the grain surface of the skin while the animal is alive, while slaughter and post-slaughter defects are largely the result of human error and are, in principle, preventable.

Industry analysis from agricultural research confirms that hides and skins are downgraded due to a combination of poor animal husbandry, disease, ectoparasites, improper slaughtering and flaying techniques, and inadequate curing, collection, storage, and transport practices. Tackling defects, therefore, requires action at every stage – from the farm to the tannery floor.

Ante-mortem defects: damage before slaughter 🔗

Ante-mortem defects are those that develop while the animal is still alive. They are caused by disease, parasitic infestation, physical injury, or poor husbandry practices. According to research conducted at the Sheba Tannery and Leather Industry in Ethiopia, the major pre-slaughter defects found in hides include scratches (64.2%), cockle or “ekek” (32.8%), wounds or scars (12.6%), pox lesions (6.1%), branding marks (2.3%), and tick bites (1.5%). While many ante-mortem defects fade during the tanning, re-tanning, and finishing processes, others leave permanent marks that compromise the final product.

Scratches and abrasions 🔗

Scratches are consistently the most frequently reported pre-slaughter defect in hides globally. They result from contact with thorny vegetation, fencing, overcrowded pens, or rough handling during transport. Abrasions occur when skin is repeatedly rubbed against a surface, weakening the grain layer. Both reduce the usable surface area of the hide and compromise its structural integrity, making it unsuitable for high-end leather products. A review paper on hide and skin production notes that poor feeding conditions, adhering dung, prod marks, and cuts all reduce the potential quality and market value of finished leather.

Skin diseases 🔗

A significant share of ante-mortem defects – estimated at around 65% – are directly linked to skin diseases, particularly those caused by ectoparasites. The same Ethiopian tannery study identifies the following key disease-related defects:

Fungal infections (Ringworm/Dermatophytosis): Caused by fungi of the genus Dermatophytes, ringworm produces circular, hairless lesions on the skin surface. It is common across cattle, sheep, and goats and leaves behind circular scars that remain visible even after tanning.

Bacterial infections (Dermatophilosis): The bacterium Dermatophilus congolensis causes dermatophilosis – known in sheep as “lumpy wool.” According to the Merck Veterinary Manual, outbreaks of dermatophilosis carry significant economic consequences for the livestock and leather industries, with the disease causing crusty lesions primarily along the dorsal surface of the animal.

Viral diseases (Pox infections): Sheep pox, goat pox, and Lumpy Skin Disease (LSD) in cattle are serious viral conditions that directly damage skin quality. LSD, caused by the Neethling virus of the Poxviridae family, produces large, firm nodules up to 5 cm in diameter across the animal’s body. These lesions are often necrotic and ulcerative, leaving deep scars. Affected animals have permanently damaged skin, which significantly lowers the commercial value of the hide.

Ectoparasites (Mange and tick bites): Mite infestations causing mange, particularly demodectic and sarcoptic mange, produce severe skin irritation and lesions. Tick bites leave small pitted scars across the hide surface. In some regions, a condition called “cockle” or “ekek” – an allergic hypersensitivity reaction triggered by lice, keds, and mite infestation – is one of the leading causes of skin downgrading in small ruminants.

Branding and physical injuries 🔗

Hot iron branding, routinely used to identify livestock, causes permanent, full-thickness damage to the skin. Studies on goat skins have identified over 60 distinct brand shapes in a single batch – each one a permanent zone of unusable leather. Horn rakes, barbed wire injuries, and wounds from fighting between animals also contribute to scarring. While healed wounds become less visible during tanning, deep scars can persist and weaken the structural properties of the finished leather.

Slaughter defects: errors at the time of killing 🔗

Slaughter defects occur during the slaughtering and flaying process itself. They are almost entirely the result of poor technique or inadequate training and are therefore largely avoidable. The Sheba Tannery study identifies the major slaughter defects as flay cuts (scores), holes, poor pattern, and vein marks.

Flay cuts and holes 🔗

Flay cuts – also called scores – are the most economically damaging of the slaughter defects. They occur when the knife pierces or scores the inner (flesh) side of the hide while it is being removed from the carcass. Careless or hurried flaying by unskilled workers results in cuts that weaken the hide’s fiber structure. When the cut fully perforates the skin, it creates a hole – an irreparable defect that reduces the usable surface area of the hide significantly. Research published in the Journal of Applied and Industrial Sciences confirms that holes caused by flay cuts are among the most persistent post-slaughter defects, directly reducing key physical properties of finished leather including tensile strength, break load, and elongation.

Vein marks and poor pattern 🔗

Vein marks appear when blood is not completely drained from the animal at slaughter. Blood trapped in the dermal blood vessels becomes visible on the grain surface of the leather as a network of dark lines – an unsightly defect that lowers the aesthetic and commercial grade of the hide. Poor pattern refers to an asymmetric or misshapen hide caused by bad initial opening cuts or uneven tension during drying after flaying. It reduces the cutting yield from the hide and results in unnecessary wastage during leather production.

Post-mortem defects: damage after slaughter 🔗

Post-mortem defects arise after the hide has been removed from the carcass and during subsequent handling, curing, storage, and transport. The Onderstepoort Journal study identifies the key post-slaughter defects as putrefaction, hide beetle damage, machine damage, and grain crack. These defects result primarily from inadequate preservation practices and are heavily influenced by the conditions under which raw hides are stored and transported.

Putrefaction and hair slip 🔗

Once a hide is removed from a carcass, it begins to decompose rapidly if not preserved promptly. Curing with salt is the standard method of preservation – it arrests bacterial growth by reducing the moisture content of the hide through osmotic pressure. When curing is delayed, inadequate, or poorly executed, bacteria break down the collagen and cause putrefaction. One of the earliest visible signs is hair slip – the loosening of hair from the follicles, indicating that bacterial degradation has already begun at the grain surface. Putrefied hides may become unsuitable for tanning altogether, representing a total loss of raw material.

Salt burns 🔗

Salt is essential for preservation, but incorrect application causes its own damage. If salt is applied unevenly, or if the hide is left in contact with concentrated salt for too long without adequate moisture balance, salt burns occur. The affected areas become stiff, discoloured, and brittle. The grain surface loses its natural suppleness and the hide becomes prone to cracking during tanning and finishing. According to standard tannery practice, wet-salting requires the hides to be heavily and evenly salted before being pressed in packs for up to 30 days – a balance between adequate preservation and avoiding over-exposure.

Over-drying and under-drying 🔗

Air-drying is a common low-cost preservation method in tropical and rural areas. However, drying speed and uniformity are critical. Over-drying causes hides to become hard, brittle, and inflexible – they crack during the soaking and liming stages of tanning. Under-drying leaves residual moisture that encourages mold growth and bacterial decomposition, producing foul odours and surface grain damage. Both conditions significantly compromise the physical characteristics of the crust leather produced.

Hide beetle damage and machine damage 🔗

Stored hides are vulnerable to attack by hide beetles (Dermestes spp.), which bore through the dried skin and leave irregular, perforated damage patterns across the surface. This type of infestation is particularly common in poorly maintained storage facilities. Machine damage, on the other hand, occurs during mechanical processing in the tannery – for example, from improper tension or excessive pressure in fleshing and splitting machines – and manifests as grain tears, scratches, or thickness irregularities.

How defects affect leather quality and economics 🔗

The consequences of hide and skin defects extend far beyond visual imperfections. Studies measuring the physical properties of defect-affected leather show measurable reductions in tensile strength, tear resistance, and elongation at break – the mechanical properties that determine how long and how well a leather product will last in use. Defective hides require additional processing steps such as heavy finishing or corrected-grain treatment to mask surface flaws, which drives up production costs. Research at the Sheba Tannery found that flaying defects alone caused 22-24% of hides and sheepskins to be rejected outright, with the majority of goatskins downgraded to lower quality categories. Putrefaction, though less common, carried the highest rejection potential – particularly in cattle hides.

From an economic standpoint, the impact is considerable. Industry data on skin quality decline shows that the share of Grade I-III pickled sheep and goat skins supplied to the world market dropped from 60-70% in the 1970s to just 10-20% by the late 1990s, a dramatic decline driven by increasing disease burden and man-made defects. Every step in the processing chain – from chemicals to labour – represents sunk cost when applied to a hide that ultimately cannot be converted into usable leather.

Prevention and management 🔗

Addressing hide and skin defects requires a coordinated approach spanning animal health management, slaughter practices, and post-harvest handling.

Animal health and husbandry: Controlling ectoparasites through regular dipping, vaccination against viral diseases like LSD and sheep pox, maintaining clean housing conditions, and avoiding practices like hot iron branding all reduce the burden of ante-mortem defects. Research on hide and skin production recommends awareness creation among farmers and strengthening extension services as foundational steps.

Skilled flaying and slaughter technique: Training abattoir workers in proper slaughtering methods – including complete bleeding, careful incision placement, and systematic hide removal using appropriate tools – is among the most cost-effective interventions available. Flay cuts and vein marks are entirely preventable with skilled technique.

Prompt and correct curing: Hides should be salted as quickly as possible after removal – ideally within two hours in warm climates. Salt must be applied uniformly and in sufficient quantity. Research on hide preservation methods continues to explore lower-salt alternatives and supplementary biocides that can extend safe storage times without compromising grain quality.

Proper storage and transport: Cured hides should be stored in cool, well-ventilated areas protected from insect infestation and moisture. During transport, hides must be handled to avoid unnecessary folding, compression, or exposure to heat that could restart bacterial activity or cause grain cracking.

What do you think? Given that the majority of pre-slaughter defects are linked to disease and poor animal husbandry, do you think investment in livestock health programs would have a greater long-term impact on leather quality than improvements at the tannery level? And with post-mortem defects being largely preventable through better handling, what structural changes do you think are most needed in how hides are collected and preserved in rural or smallholder settings?

References

1. https://www.researchgate.net/publication/346987980_Effects_of_skin_and_hide_defects_on_quality_grades_and_physical_characteristics_of_crust_leather
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC6238661/
3. http://www.luresext.edu/?q=content%2Fcurrent-problems-leather-industry
4. https://www.researchgate.net/publication/281552310_Pre-slaughter_slaughter_and_post-slaughter_defects_of_skins_and_hides_at_the_Sheba_Tannery_and_Leather_Industry_Tigray_region_northern_Ethiopia
5. https://austinpublishinggroup.com/agriculture-crop-sciences/fulltext/aacs-v10-id1180.php
6. https://www.merckvetmanual.com/integumentary-system/dermatophilosis/dermatophilosis-in-animals
7. https://en.wikipedia.org/wiki/Lumpy_skin_disease
8. https://www.researchgate.net/publication/334684807_Effect_of_some_Skin_Defects_on_Physical_Properties_of_the_Leather
9. https://bestleather.org/leather-tanning/
10. https://en.wikipedia.org/wiki/Tanning_(leather)
11. https://www.researchgate.net/publication/348137838_REVIEW_ON_TANNING_OF_HIDES_AND_SKINS-_LOW_SALT_OPTIONS_IN_HIDE_PRESERVATION