Experiments were carried out to study the digestibility of a cassava (gari) diet and its effect on growth in young male dogs. Three groups of dogs were fed on diets with rice (control), cassava (gari), and rice+cyanide respectively as the carbohydrate source. Each diet contained 130 g crude protein (nitrogenx6.25)/kg, was supplemented with vitamins and minerals, and was fed for 14 weeks. Variables measured were body-weight gain, bone growth, plasma alkaline phosphatase (EC 3.1.3.1) activity, total serum 3,5,3'-triiodothyronine (T3) and some plasma free amino acids. The apparent digestibilities of dry matter, protein and fat were not significantly different in the three groups, but the digestibility of gari fibre was significantly lower than the digestibility of rice fibre when fed to dogs (P < 0.05). Proximate analysis of the faeces showed that the group of dogs fed on the gari diet had faeces which had a significantly higher moisture content than the faeces of the other groups (P < 0.05), and also a significantly higher fibre content (P < 0.05). There was no significant difference in body-weight gain and bone growth between the control and gari-fed groups of dogs, but these variables were significantly lower in the dogs fed on the rice+cyanide diet (P < 0.05). At the end of the 14-week experimental period total serum T3 and plasma alkaline phosphatase activity were not significantly different between the control group of dogs and the gari-fed group, but were significantly lower in the rice+cyanide group. Plasma free methionine, leucine, isoleucine and valine concentrations were higher in the rice+cyanide group of dogs than in the control group and the gari group, indicating that these amino acids were accumulating and not being utilized for protein synthesis and growth to the same extent in the rice+cyanide group of dogs as in the other groups. It was concluded that the digestibilities of cassava starch and rice starch were the same in the dog but that rice fibre was more digestible in the dog than cassava fibre. It was also concluded that growth proceeded normally when a balanced gari diet or a balanced rice diet containing 130 g crude protein/kg was fed to dogs, but growth was retarded when a balanced rice+cyanide diet containing 130 g crude protein/kg was fed to dogs because total serum T3 concentration became greatly depressed.

Growing dogs were divided into three groups and were fed on nutritionally-balanced diets. Control dogs were fed on a rice diet, the cassava (gari) group ate a diet in which gari provided the carbohydrate source, while the rice + cyanide group consumed the rice diet to which hydrocyanic acid (equivalent to that present in gari) was added. Each group consumed its diet for 14 weeks, during which plasma thiocyanate concentration and total serum triiodothyronine (T3) were monitored. At the end of the experiment the concentrations of the plasma free amino acids phenylalanine and tyrosine, the thyroid weights and histology were determined. While plasma thiocyanate remained undetectable in control dogs, animals consuming both gari and rice + cyanide generated significant amounts. In the control dogs and the gari group, total serum T3 increased 40 and 38.8 % respectively from the basal level by the end of the period (P < 0.02). In contrast there was a decrease in T3 by 36% in the dogs fed on rice+cyanide (P < 0.05). This group also showed significant thyroid enlargement and a histological picture consistent with parenchymatous goitre, whereas the gari group was essentially normal. The relatively low mean thyroid weight, the rise in total serum T3 level and the normal histological appearance of the gland indicate that dogs that consumed the gari diet were essentially normal with respect to their thyroid function, in spite of their high blood thiocyanate content. In contrast, dogs that consumed rice with cyanide suffered from hypothyroidism and goitre. It is suggested that the gari diet, despite generating thiocyanate endogenously, when taken in a nutritionally-balanced diet with high-quality animal protein, has no deleterious effects on thyroid function.

Growing dogs were divided into three groups and were fed on a control (rice) diet, a diet in which cassava (Manihot esculenta Crantz; gari) was used as the carbohydrate source, and the rice diet to which cyanide (equivalent to that present in gari) was added. Each group consumed its diet for 14 weeks, during which plasma thiocyanate concentration and plasma lipase (EC 3.1.1.3) activity were monitored. Plasma free amino acids were determined from pooled samples taken at the end of the experimental period, and the insulin status of the dogs was evaluated using the gluconeogenic index. The dogs were killed and the pancreas examined for histopathology. Dogs fed on both gari diet and the rice+cyanide diet generated significant amounts of thiocyanate when compared with the controls, with the rice+cyanide group having higher plasma thiocyanate than the gari group (P < 0.01). Plasma lipase activity rose significantly at the end of the experimental period in the dogs fed on gari (P < 0.05). Gluconeogenesis from protein was greatest in the dogs fed on gari, five times greater than that in the control dogs, while gluconeogenesis from protein in the dogs fed on rice+cyanide was approximately twice as high as that of the control dogs. Histopathological examination of the pancreas showed haemorrhage, necrosis, fibrosis and atrophy of the acinar tissue and fibrosis of the islets of Langerhans in the dogs fed on gari. The pancreas of the dogs fed on rice+cyanide showed similar lesions but haemorrhage was not prominent and fibrosis was more marked. The present study indicated that a hypoinsulinaemia developed which was more severe in the animals fed on gari than in the dogs fed on the rice+cyanide diet and that the condition was not related to the level of plasma thiocyanate or the histopathology observed.