General

Malnutrition is poor nutrition that has arisen as a consequence of insufficient or poorly balanced food, or because of faulty digestion or utilisation of food.¹ Owners and keepers of animals have a responsibility to investigate the causation of any suspected malnutrition problem in animals under their care. Not to do so is neglectful.

Recognition of severe malnutrition is relatively straightforward and veterinary involvement is usually restricted to those cases involving gross neglect (Figs 5.1 & 5.2). Body condition scoring methods are available for different species of domestic animals and are subdivided for different classes of farm animal, e.g. dairy cows and beef suckler cows and heifers. These guides can be invaluable to clinicians as the veterinarian must have a thorough understanding of the variation in body condition that is the ‘accepted norm’ at different times of the year in the various livestock husbandry systems. Similarly, birds of prey that are used for hunting may have ‘flying weights’ that are significantly less than the ideal weight for a resting bird.

Fig. 5.1 Bull mastiff. Neglected and starved to the point of death over a 5-month period.

(By kind permission of the Scottish Society for the Prevention of Cruelty to Animals.)

Fig. 5.2 More than 20 dead cattle were discovered during the initial visit to a farm following a complaint by a member of the public. The remaining animals were uniformly malnourished.

In live animals, body scoring provides a clear indication of the adequacy of recent nutrition. However, because these methods are designed to assess animals in the standing position, they are less applicable to cadavers. Additionally, alterations related to post-mortem degeneration may influence the body score. Nevertheless, before beginning dissection on whole fresh cadavers it is useful to palpate the body (in a similar manner to body scoring the live animal), in order to make a general assessment of body condition ranging from ‘excellent’ through ‘adequate’ to ‘emaciated’. Whenever possible, the weight of the animal should be compared with breed standards.

Malnutrition, infection and the immune system

The interaction between malnutrition, frequent infection and impaired immune function has been the subject of much interest over many years. In human medicine the cyclical nature of this interrelationship, where each element has an effect on the other two, has been accepted for nearly 40 years following publication of the monograph by Scrimshaw et al.² Keusch³ provided clarity, in 1990, regarding the manner in which these three factors can result in the downward spiral of bodily condition. These findings are equally valid for domestic animals.

In the past it was assumed that malnutrition was the primary cause that resulted in impaired immune function and subsequent frequent or persistent infections. There is persuasive experimental evidence that this sequence of events can occur.⁴ However, infection (in the form of parasites or microbial infections) may be the initiating cause of the downward spiral in animals being fed a marginal diet. During infections the patient may have a reduced food intake, compounded by increased energy consumption, catabolism of muscle proteins, loss of nitrogen stores, and depletion of glycogen and fat stores. The animal moves from a state of marginal diet into protein-energy malnutrition. Without an improvement in diet, cell-mediated immunity is impaired and infections persist or recur before the immune damage can be repaired. Thus, the body condition of the animal continues to decline. Interventions to prevent the decline are dependent on improving various aspects of the husbandry to lift the animal from its marginal diet and reduce the disease challenge.

Post-mortem findings in malnutrition

Muscle

Atrophy of muscle masses begins in monogastrics after 24 hours of starvation. In calves and lambs this change takes slightly longer, whilst its onset in adult ruminants is delayed for about 3 days. The back and thigh muscles are first affected but the process extends to all muscle groups (Fig. 5.3). Depletion of glycogen deposits in the muscle cells of emaciated animals interferes with the normal process of rigor mortis. Consequently these bodies do not ‘set’.

Fig. 5.3 Bull mastiff (see Fig 5.1). Profound loss of muscle. The deformity of the rib cage allowed tracing of the breeder and the dog’s owner.

Stomach and intestines

In the normal, healthy ruminant, the rumen accounts for approximately 25% of live weight. The rumen of a markedly underweight animal may exceed this figure because of the loss of bodily condition and the consumption of quantities of poor-quality feed. The ruminal contents of normal sheep tend to be relatively dry compared with those of cattle, and the observation of moderate quantities of fluid in the ovine rumen is an indication of starvation and not that the sheep had been drinking water. The presence of food in the rumen is frequently advanced as evidence that the animals were being fed adequately. This may not be the case, because many severely malnourished animals have quantities of fibrous material in the rumen. Consequently, retention and analysis of rumen contents may be helpful in determining the nutritional value of the food available to the animal.

The observation of moderate quantities of wet, semi-solid digesta within the upper parts of the intestines of undernourished ruminants is sometimes presented as evidence of recent, adequate feeding. However, this could be misleading because the intestinal contents are the product of slow and progressive digestion of fibrous material in the rumen and eventual passage of this partially digested food to the remainder of the digestive tract some time after ingestion. As a result, starved ruminants commonly have quantities of wet or bulky intestinal contents.

Similarly, the copious sacculated large intestines of rabbits may contain considerable quantities of wet or fluid contents, even when the skin and the muscle mass of the body show signs of malnourishment and dehydration.

Dogs and cats do not store food in their stomachs for extended periods. In most cases, food passes to the intestines within hours of ingestion. Consequently, in contrast to ruminants, the stomach and small intestines of dogs and cats after several days of starvation may be virtually empty, or may contain only quantities of mucus. Gastric ulceration (Fig. 5.4), caused by reduced blood flow to the lining of the stomach, in malnourished dogs may lead to perforation of the stomach wall. Hungry animals may ingest a variety of indigestible materials (plastic bags, rubber, cloth, wood) and the stomach can become distended with this type of non-food material (Fig. 5.5). Dry or sticky faecal material may be present in the large intestine.

Fig. 5.4 Gastric erosion and ulceration in a severely malnourished and hypothermic greyhound/lurcher puppy.

Fig. 5.5 This severely malnourished 18-month-old Rotweiler dog died following perforation of a gastric ulcer. The stomach was filled with a mass of indigestible material including rubber and plastic.

A notable feature of dogs and cats that have starved to death is that the gastrointestinal tract is often considerably less malodorous than that of adequately nourished and hydrated specimens.

Natural disease and malnutrition

Post-mortem examination of very thin animals may uncover natural disease or physiological states that could account, at least partially, for the poor bodily condition, e.g. advanced neoplasia (Fig. 5.6), Johne’s disease, heavy parasitism, lactation. The duty of the veterinarian is to make an assessment of the contribution that these processes played in the reduction of body condition and to note whether appropriate veterinary treatment had been sought for the progressive loss of weight. These matters are not always clearcut (Case study 5.1).

Fig. 5.6 Emaciated adult cat showing advanced neoplasia in the roof of the mouth and protruding on the left side. No veterinary attention had been sought.

Case study 5.1: Malnourishment of bull terrier

Clinical history:

‘Peggy’ was an adult Staffordshire bull terrier type. She died in late January. It was reported that she had puppies ‘sometime before Christmas’, but these had been found homes before the New Year. She had been fed at around 18.00 hours and was discovered dead the following morning.

Post-mortem examination:

Peggy was very thin but her weight was 13.5 kg, which falls within the breed standard (11–15.4 kg) for British Staffordshire bull terrier bitches. She had no omental or subcutaneous fat, contained no intestinal parasites, and showed no evidence of systemic infections, degenerative disease or neoplasia. Her nipples were prominent but the mammary tissue was inactive. The cause of death was 180° torsion of the stomach. The stomach contained 1.8 kg of proprietary dog food.

The issues:

Peggy was considerably underweight for her size of frame and her loss of weight would have taken some time to develop. She was clearly undernourished but the dilemma for the forensic veterinary practitioner lies in deciding what part her previous gestation and lactation played in her loss of condition. Should the owners have noticed her declining weight and should she have received veterinary attention? Death was related to feeding an abnormally large meal to a thin, possibly very hungry, dog. Was this a manifestation of ongoing neglectful behaviour or, perhaps, an inappropriate action by an ill informed owner who was responding to adverse criticism on the dog’s body condition?

Equally important must be the recognition that not all diseases or infections result in poor condition. For example, post-mortem examination of malnourished farm animals will frequently show evidence of limited areas of pneumonia and small numbers of liver flukes or lungworms. Such findings should be recorded and included in the final report, but if it is considered that they lack relevance to the decline in body condition this should be clearly stated.