Characteristic relation between dietary metabolizable energy content and digestible energy content in laboratory cats

Estimating energy losses with urine in the cat

Urinary energy losses in cats have to be determined in energy balance trials as well as for the calculation of the metabolizable energy (ME) content of cat food. The aim of the present study was: first, to assess whether the energy content of cat urine quantified by bomb calorimetry differs from that quantified using GE (kJ) urine = 33 kJ × g C urine + 9 kJ × g N urine and investigate whether this difference could be attributed to influences of diets. Second, to assess whether the subtraction of 3.1 kJ/g of protein intake used for estimation of metabolizable energy content of cat foods is confirmed as usable. Data from 27 energy and protein balance trials from different studies with complete sampling of urine and faeces (29 cats in part A and 35 cats in part B) were used. Gross energy, carbon and nitrogen were determined in food, faeces and urine. Gross energy values in urine tended to be higher when determined with the formula of Hoffman and Klein compared to bomb calorimetry. The average relative difference of gross energy values between the methods was 18.8%. The mean energy loss in kJ/g of protein intake resulted in 3.7 kJ/g protein intake, which was not statistically significantly different (p = 0.12) from the tested value of 3.1 kJ/g of protein intake. In conclusion, the formula of Hoffman and Klein is not appropriate for the estimation of energy in cat urine. In balance studies, it is advisable to quantify the urinary energy content by bomb calorimetry. In the second part of the study, the protein correction factor to determine ME of 3.1 kJ/g protein intake for urinary energy losses of Kienzle et al. could be confirmed.

Nutritional sustainability of pet foods

Sustainable practices meet the needs of the present without compromising the ability of future generations to meet their needs. Applying these concepts to food and feed production, nutritional sustainability is the ability of a food system to provide sufficient energy and essential nutrients required to maintain good health in a population without compromising the ability of future generations to meet their nutritional needs. Ecological, social, and economic aspects must be balanced to support the sustainability of the overall food system. The nutritional sustainability of a food system can be influenced by several factors, including the ingredient selection, nutrient composition, digestibility, and consumption rates of a diet. Carbon and water footprints vary greatly among plant- and animal-based ingredients, production strategy, and geographical location. Because the pet food industry is based largely on by-products and is tightly interlinked with livestock production and the human food system, however, it is quite unique with regard to sustainability. Often based on consumer demand rather than nutritional requirements, many commercial pet foods are formulated to provide nutrients in excess of current minimum recommendations, use ingredients that compete directly with the human food system, or are overconsumed by pets, resulting in food wastage and obesity. Pet food professionals have the opportunity to address these challenges and influence the sustainability of pet ownership through product design, manufacturing processes, public education, and policy change. A coordinated effort across the industry that includes ingredient buyers, formulators, and nutritionists may result in a more sustainable pet food system.

Determining metabolizable energy content in commercial pet foods

This study was conducted to assess the suitability of several equations for the estimation of metabolizable energy (ME) of pet foods. Sixteen canned and 31 dry cat foods and 24 dry dog foods representing the range of energy densities found in commercial adult, growth or all life stage products were evaluated in four separate experiments. In vivo ME was compared with estimates of ME generated by several previously published equations. The results indicated that the equation recommended by Association of American Feed Control Officials provided reasonable estimates of in vivo ME for both canned cat foods and dry dog foods, but proved unsuitable for dry cat foods. Better estimates were generated in each case using other published equations. Of the equations tested, the most accurate equations for estimating ME (kJ/g) without feeding trials were: for canned cat foods: [(16.32 x protein) + (32.22 x fat) + (12.55 x NFE)]; for dry cat foods: [((GE x 1.209) - 1.911) x 4.184] or [((0.075 x g fat) + 2.766) x 4.184] for dry dog foods: [GE=(24 x g protein) + (38 x g fat) + (17 x g NFE), then percentage energy digestibility=91.2 - (1.43 x percentage crude fibre in dry matter), then ME=(GE x percentage energy digestibility) - (4.34 x g protein)]. With the exception of high-fibre weight-management diets, the simple equation [((GE x 1.209)-1.911) x 4.184] also reliably predicted ME in dry dog foods.

Food intake and blood glucose in normal and diabetic cats fed ad libitum

Ten diabetic cats were studied at intervals for up to 12 months with twice-daily insulin injections. Ten clinically healthy cats were also studied. Diets fed were based on the individual cat's performance, using mainly commercial dry or canned cat foods and fresh meat. In most cases more than one food was offered. Food was given fresh twice daily, and the cats allowed to eat ad libitum. The food intake and blood glucose were measured every 2 h in diabetic cats after insulin injection and in diabetic and normal cats without insulin injections. Food was quantified by the energy consumed (kJ ME), crude protein (g), crude fat (g), and carbohydrate (g). The blood glucose in 10 diabetic cats was measured for 2 h following a 20-min meal. Both diabetic cats and normal cats showed similar patterns of eating, with a higher food intake in the 2 h after fresh food was placed. Both groups of cats ate multiple small meals spread through the day and night. There was little or no correlation between the blood glucose and the amount of food consumed over the previous 2-h period, in insulin- or non-insulin-treated diabetic cats, or in normal cats. An overnight fast did not significantly alter morning blood glucose in diabetic cats. No demonstrable appetite stimulation occurred following an occurrence of low blood glucose; however, recorded incidences were few. No post-prandial hyperglycaemia was seen in the 10 diabetic cats during a 2-h period following the ingestion of typical cat foods.