VN October 2020

Vetnuus |Oktober 2020 32 There are of course several reasons why our profession recommends neutering for cats not intended for breeding: • Reduce the number of unwanted kittens • Reduce the incidents of fight wounds and abscesses • Reduce the risk of transmission of certain infections such as FIV and FeLV • Reduce the risk of mammary tumours and uterine infections in the feline and testicular tumours in the male • Promote a calmer, more affectionate pet (no calling of queens and less incidents of spraying toms) While these are all valid reasons to be sterilising cats, there are certain considerations that need to be taken into account. Gonadal hormones (i.e. estradiol, progesterone and testosterone) not only control the production of reproductive cells, but are also recognised to have an effect on general metabolism and food intake. Other hormones, such as prolactin and leptin, are also thought to be involved. 1 With the interruption of gonadal hormone production and release which happens after neutering, levels of pituitary hormones increase. 1 Following neutering, prolactin (synthesised in the pituitary gland) is also shown to increase as does leptin (which is synthesised in the liver) and hyperleptinaemia has been found to induce obesity. 2 Within 48 hours after neutering, appetite increases significantly. Neutered cats are less able to regulate appetite and so eat more food. At the same time, energy requirements actually decrease. If a cat is fed ad lib, it will gain weight by 30% within just 4 months of being neutered. 3 This will predispose cats to weight gain and will therefore be a risk factor for developing obesity related diseases such as diabetes mellitus and osteoarthritis. When male cats are affected with calcium oxalate stones, there is a higher incidence in sterilised vs entire toms. Obesity is a predisposing factor to urinary stone development as overweight cats are less active and have a tendency to drink less and so urinate less. The urine therefore concentrates and stagnates in the bladder, creating an ideal environment for stones or crystal development. Tailored diets for the neutered cat are formulated for both gender and life stage, realising that these factors as well as reproductive status have an influence on maintenance energy requirements. Dietary considerations in the neutered cat include: • High protein levels in the diets to maintain lean muscle mass. Proteins provide less net energy than carbohydrates. • L-carnitine: a transporter of fatty acids into the mitochondria, to maintain optimal body condition • Reduced calorie content, moderate to low fat content as well as moderate starch content to reduce the incidence of weight gain Prevention is always better than cure, so keeping these cats at their ideal body weight post-sterilisation and preventing weight gain will reduce the incidence of most post-neutering complications. Sterilisation and cats Dr Debby Bain +26% +18% Daily food intake Male Female Neutered male Spayed female Source Flynn, Hardie, Amstrong 1996 Before After Source Rynn, Hardie, Armstrong 1996 S/O index: promotes the ability to be able to predict the risk of both struvite and calcium oxalate stone development, independent of the cat’s gender and age. It is not based on the measurement of urinary pH alone, but also takes into account the analyses of the urinary volume, and different ions involved in the development of uroliths (calcium, magnesium, sodium, potassium, ammonium, phosphate and pyrophosphate, oxalate, citrate, sulphate, urate and chloride). This enables formulation of a single food to avoid the risk of the formation of both struvite and calcium oxalate uroliths. It will not dissolve struvite stones and cats need to be fed on a diet with the S/O index exclusively for it to be affective. References: 1. Martin L, Siliart B. 2005. Hormonal consequences of neutering in cats; Waltham Focus , 15(3): 32-35 2. Kopelman PG. 2000. Physiopathology of prolactin secretion in obesity; International Journal of Obesity & Related Metabolic Disorders Disord, Suppl 2: S104-S108 3. Scarlett JM, Donoghue S. 1998. Associations between body condition and disease in cats. J Am Vet Med Assoc 212 (11): 1725-1731 4. German A. 2012. Weight control and obesity in companion animals; Veterinary Focus 22 (2):38-46