History

Cat Nutrient Requirements

Energy Requirements - Key Message

WALTHAM has contributed to the understanding of the energy requirements of cats by:

  • Showing that the energy requirements of cats are lower than previously thought, and the relationship between energy requirement and body size is not linear.
  • Generating insight into the further reduction of energy requirements seen in neutered adult cats.
  • Demonstrating that the energy requirement of kittens is less than previously thought, and is further reduced by neutering.
  • Generating insight into energy storage in neutered kittens.

Background

The amount of dietary energy an animal needs to meet its energy requirement has to account for:

Basal metabolic rate

  • The energy expended to maintain basic physiological functions (including heart beat, respiration, and kidney function). It is usually measured as resting metabolic rate – that is, the energy expended to maintain the body whilst lying down and awake.
Thermogenesis
  • The energy expended to ingest, digest, absorb, and assimilate food.
  • The energy expended to cope with stress, including changes in environmental temperature.
Activity
  • The energy expended during movement and exercise.

Basal metabolic rate depends on factors including body weight, body composition, age, and hormonal status. Thermogenesis can vary widely and results in daily fluctuations in energy requirement.

Energy expenditure (or requirements) can be measured as heat production (using direct calorimetry). This is affected not only by body weight, but also by body surface area. Body weight that has been corrected mathematically to take account of surface area is known as metabolic body weight (MW), and this allows a comparison of the energy requirements of animals that differ in body size.

The body weight of healthy mature domestic cats varies from about 2.5 kg to 6.5 kg. For a long time it was assumed that, with such a narrow range of body weight, feeding cats of different sizes was straightforward and linear in nature.

Why WALTHAM is Interested

A thorough understanding of energy requirements is essential in order to produce accurate feeding guidelines to help owners feed their cat appropriately and prevent under-nutrition or obesity.

However, the energy requirements of the adult cat for maintenance are still largely uncharacterised and much debated. In 1986, the NRC recommended a linear allowance for relatively inactive cats that treated each kg body weight of small cats and large cats the same (NRC 1986). This was updated in 2006 to provide slightly less energy per kg bodyweight for overweight cats (NRC 2006). However, much variability was still evident in the available data.

Approach

Over time, WALTHAM has undertaken a great many feeding studies of cats and routinely collects body weight data. This provides a unique and sizeable dataset for analysing the effect of body size on the amount of food required to maintain body weight, based on the premise that cats which are maintaining their body weight have an energy intake equivalent to energy requirement.

Discovery (Energy Requirement)

The energy requirement of cats is lower than previously thought, and the relationship with body size is not linear

Two studies have demonstrated a logarithmic (rather than linear) relationship between energy requirement and body weight in the cat.

Using the body weight data from 62 digestibility trials at WALTHAM, a logarithmic relationship between energy requirement and body weight was found (Earle and Smith 1991). This research showed that larger cats have a lower energy requirement per unit of body weight than smaller cats (Figure 1. Earle and Smith 1991).

Digestible energy
Reproduced from Earle KE, Smith PM. Digestible energy requirements of adult cats at maintenance. J Nutr 1991.121(11Supp):S45-46

Figure 1: Mean ± SD digestible energy intake (kJ/kg body weight) of the adult cat at maintenance (Earle and Smith 1991)

Subsequently, in collaboration with scientists in New Zealand, a meta-analysis of the data from 42 publications was conducted (Bermingham et al. 2010). The effect of body weight on maintenance energy requirements is shown in Figure 2. Energy requirements were found to be lower than those described by the NRC 2006 recommendations (Bermingham et al. 2010). The allometric equation for maintenance requirements in all cats was calculated with a back-transformed equation of 77.6 kcal/kg BW -0.711 (Bermingham et al. 2010). These data are important because meta-analysis is a powerful statistical tool, and the data were sourced from published literature (that is, not solely from the cats housed at WALTHAM). This study therefore strengthens the body of data on the energy requirements of the cat.

Effect of body weight
Reproduced from Bermingham EN, Thomas DG, Morris PJ, Hawthorne AJ. Energy requirements of adult cats. Br J Ntr 2010. 103(8):1083-1093 http://journals.cambridge.org/abstract_S000711450999290X

Figure 2: Effect of body weight (BW) on the maintenance energy requirements of domestic  cats (O;  —), compared with the predicted requirements from the present study (– – –) and those predicted by the National  Research Council (••••••) (Bermingham et al. 2010).

Insight Generation (Neutered Cats)

The energy requirement of cats decreases after neutering

Neutered cats are thought to be at particular risk of obesity. Data generated in a study at WALTHAM showed that the energy requirement of adult female cats decreases after neutering. The 11 female cats (aged 2.6–6.2 years, mean 3.9 ± 1.5 years) were fed to maintain a constant body weight, and their energy intake decreased from a mean of 55.5 kcal/kg/day immediately post-neutering to 45 kcal/kg/day 12 months later (Harper et al. 2001).

Discovery (Neutered Kittens)

The energy requirement of kittens is less than previously thought, and is further reduced by neutering

Neutered cats are thought to be at particular risk of obesity. WALTHAM undertook this post hoc analysis of data from a previous study to understand the effects of neutering on food intake, body weight, and changes in body composition in growing kittens.

In the study, the twelve pairs of 11-week-old female littermates were randomly assigned to either a neutered group (neutered at 19 weeks old) or an entire group (kept sexually entire) and offered free access to a dry diet until the age of 1 year (Alexander et al. 2011).

Food intake of the neutered kittens increased after neutering (P<0.00001 Figure 3). Differences in food intake (per kg body weight) between the groups peaked 10 weeks after neutering, when the mean intake of neutered kittens was 17% more than that of entire kittens (P=0.00014). Food intake then decreased, so that after 18 weeks post-neutering there was no significant difference between the groups.

Body weight of the neutered kittens increased after neutering (P<0.00001 Figure 4). Bodyweight of the neutered kittens was 24% greater than entire kittens at 52 weeks (P<0.0001) and their body condition score was 16.6% higher (P=0.0028).

Food intake neutered
Reproduced from Alexander LG, Salt C, Thomas G, Butterwick R. Effects of neutering on food intake, body weight and body composition in growing female kittens. Br J Nutr. 2011 Oct;106 Suppl 1:S19-23. http://journals.cambridge.org/abstract_S0007114511001851
Food intake neutered 2
Reproduced from Alexander LG, Salt C, Thomas G, Butterwick R. Effects of neutering on food intake, body weight and body composition in growing female kittens. Br J Nutr. 2011 Oct;106 Suppl 1:S19-23. http://journals.cambridge.org/abstract_S0007114511001851

Figure 3: Food intake and body weight of entire (open symbol) and neutered (shaded symbol) kittens, mean ± SD (Alexander et al. 2011). The time of neutering is shown by the vertical dotted line 

Whilst maintaining an ideal body condition score the entire kittens consumed 93% of their theoretical intake at 26 weeks of age, and 79% at 52 weeks of age. This suggests that the recommendations for energy requirement in kittens are inappropriate.

Neutered kittens consumed similar amounts of energy to the entire kittens from 18 weeks post-neutering, while their body weight, body condition score and percentage fat continued to increase. This suggests that neutered kittens have a reduced metabolisable energy requirement compared with entire kittens.

This study suggests that the current recommendation for the energy requirement of kittens appears to be too high. In particular, neutered kittens should not be fed ad libitum, rather they should be fed to maintain an ideal body condition score (Alexander et al. 2011).

Insight Generation (Neutered Kittens)

Neutered kittens store more energy and have lower energy requirements than entire kittens

Neutering of female kittens at 19 weeks of age resulted in higher energy intake (Alexander et al. 2011), but the weight gain and especially fat percentage seemed out of proportion with the differences in energy intake. This suggested reduced energy requirement for maintenance and/or tissue accretion after early neutering.

Using factorial analysis, the metabolisable energy (ME) requirement for tissue accretion and maintenance was calculated in the same kittens from 11–52 weeks of age (Alexander et al. 2011). This analysis was a collaboration with Ludwig-Maximilians-Universität, Munich, Germany.

Dual energy x-ray absorptiometry (DXA) data were transformed to provide values for body protein and fat, then the energy content in the body was calculated from these data using 9.4 kcal/g fat and 5.7 kcal/g protein. The composition and energy content of the gained tissue was calculated using the difference in the amount of nutrient in the body at each consecutive DXA measurement and dividing it by the difference in body weight and time. The daily energy accretion in tissue was presumed to be the net requirement for tissue accretion. The utilisation efficiency of ME was taken from the data on fattening pigs (0.56 for protein; 0.74 for fat). The resulting values for each individual kitten were subtracted from the energy intake of the individual kitten in the study and the remaining values were assumed to represent the maintenance requirement.

Maintenance requirements and requirements for tissue accretion differed significantly between the neutered and entire kittens between 31 and 52 weeks of age. The mean daily ME requirement for tissue accretion and maintenance for neutered kittens was 180 ± 36 and 59 ± 18 kcal/day compared with 115 ± 41 and 99 ± 30 kcal/day for entire kittens (Alexander et al. 2011).

These neutered female colony cats stored more energy and had lower maintenance energy requirements than entire female colony cats and lower energy requirements than seen in the published literature (Alexander et al. 2011). Early neutering may decrease maintenance energy requirements even further than neutering of adults.

References

Alexander LG, Salt C, Thomas G, Butterwick R. Effects of neutering on food intake, body weight and body composition in growing female kittens. Br J Nutr. 2011 Oct;106 Suppl 1:S19-23.


Alexander L, Salt C, Thomas G, Kienzle E, Butterwick R. Factorial analysis of energy requirements in entire and neutered growing female colony cats. Proceedings of the 15th Congress European Society of Veterinary and Comparative Nutrition. Zaragoza, Spain, September 14-16 2011. Page 41


Bermingham EN, Thomas DG, Morris PJ, Hawthorne AJ. Energy requirements of adult cats. Br J Nutr. 2010 Apr;103(8):1083-93.


Earle KE, Smith PM. Digestible energy requirements of adult cats at maintenance. J Nutr. 1991 Nov;121(11 Suppl):S45-6.


Harper EJ, Stack DM, Watson TD, Moxham G. Effects of feeding regimens on bodyweight, composition and condition score in cats following ovariohysterectomy. J Small Anim Pract. 2001 Sep;42(9):433-8.


National Research Council. Nutrient Requirements of Dogs and Cats, 2006. National Academy Press, Washington.


National Research Council. Nutrient Requirements of Cats, revised 1986. National Academy Press, Washington.



Protein - Key Message

WALTHAM has contributed to the understanding of protein metabolism and dietary protein requirement of the adult cat by:

  • Showing that adult cats need about 10% protein energy in their diet to maintain nitrogen balance.
  • Demonstrating that the protein metabolism of the cat adapts when fed above minimal requirements demonstrating a degree of metabolic flexibility.​

Background

Protein consists of amino acids that are classified as essential (because they can’t be synthesised by the body) or non-essential (because the body can synthesise them).
Dietary protein must provide sufficient amino acids to satisfy the body’s metabolic requirement. Aspects of this can be measured as:

  • Protein turnover (synthesis, breakdown, inter-conversions).
  • Synthesis of other nitrogen-containing compounds and urea.
  • Protein oxidation.
  • Gluconeogenesis (the synthesis of glucose from non-carbohydrate carbon sources including amino acids).
Dietary protein requirements are also dependent on energy intake, life-stage (growth increases the requirement), lifestyle (physical activity increases the requirement), and other factors such as disease.
Compared with other species, the cat has a higher dietary protein requirement (NRC 2006). This has been attributed to a lack of metabolic flexibility, with less efficient adaption of feline hepatic nitrogen catabolic enzymes to dietary protein intake (Rogers et al. 1977).

Why WALTHAM is Interested

Understanding the protein requirements and protein metabolism of the cat, an obligate carnivore, is fundamental to providing the right nutrition.

Approach

WALTHAM investigated the protein requirements of adult cats for maintenance using the nitrogen balance technique. The metabolic flexibility of the cat was examined by measuring aspects of its protein metabolism, in an effort to understand why the cat needs so much protein.

Discovery (Protein Requirement)

Adult cats need about 10% of their dietary energy to be provided by protein

The nitrogen balance technique measures nitrogen intake and nitrogen excretion. When these are equal, the animal is considered to be consuming sufficient protein to meet its needs for maintenance. Nitrogen balance is negative during fasting or protein malnutrition, and is positive in growing animals.

A study at WALTHAM showed that when all essential amino acids were present at more than adequate concentrations, about 12.5% protein in the diet was required to maintain nitrogen balance in adult cats (Burger et al. 1984). This is equivalent to about 10% dietary energy as protein (Burger 1993). This study is pivotal to the literature on the crude protein requirement of the cat, and forms the basis of the NRC recommendation (NRC 2006).

WALTHAM also undertook some preliminary investigations on the amino acid requirements of the adult cat (Burger and Smith 1990).

Discovery (Protein Metabolism)

The protein metabolism of the cat adapts to moderate-to-high levels of dietary protein as in other species

Whole-body techniques often used in other species, including humans were applied to cats. These techniques included protein turnover (using a tracer), macronutrient oxidation (using indirect calorimetry), and urea kinetics (using a tracer). The nutritionally-complete diets were designed to provide moderate (20–35% of energy) and higher (52–70% of energy) levels of protein.

In collaboration with Prof Joe Millward (University of Surrey) and Dr Gerald Lobley (Rowett Research Institute, Aberdeen), feline protein turnover was found to adapt to dietary protein intake when fed above minimal requirements (Russell et al. 2003). This was the first time whole body protein turnover had been measured in the cat.

Feline amino acid oxidation was also correlated with protein intake (Russell et al. 2002). This study was in collaboration with Peter Murgatroyd (University of Cambridge), and was the first time calorimetry had been used to measure protein oxidation in the cat.
A study of feline urea kinetics in collaboration with Prof Joe Millward (University of Surrey) and Dr Gerald Lobley (Rowett Research Institute, Aberdeen) found that urea production was related to dietary protein level (Russell et al. 2000). However, there was a low level and lack of nutritional sensitivity of urea entry and hydrolysis into the gut, and subsequent retention of urea nitrogen for anabolism (Russell et al. 2000). This was the first time urea kinetics had been measured in the cat.

This research shows that, as with other species, these aspects of feline protein metabolism adapt to dietary protein intake when fed above minimal requirements demonstrating a degree of metabolic flexibility.

References

Burger IH. A basic guide to nutrient requirements. In: The Waltham book of companion animal nutrition. Editor: IH Burger. Pergamon Press, Oxford. 1993, pages 5-24.


Burger IH, Smith PM. Amino acid requirements of adult cats. In: Nutrition, malnutrition and dietetics of the dog and cat. Editors: H Meyer, E Kienzle, ATB Edney. British Veterinary Association, London. 1990, pages 49-51.


Burger IH, Blaza SE, Kendall PT, Smith PM. The protein requirement of adult cats for maintenance. Feline Pract 1984;14(2):8-14.


National Research Council. Nutrient Requirements of Dogs and Cats, 2006. National Academy Press, Washington.


Rogers QR, Morris JG, Freedland RA. Lack of hepatic enzymatic adaptation to low and high levels of dietary protein in the adult cat. Enzyme. 1977;22(5):348-56.


Russell K, Lobley GE, Millward DJ. Whole-body protein turnover of a carnivore, Felis silvestris catus. Br J Nutr. 2003 Jan;89(1):29-37.


Russell K, Murgatroyd PR, Batt RM. Net protein oxidation is adapted to dietary protein intake in domestic cats (Felis silvestris catus). J Nutr. 2002 Mar;132(3):456-60.


Russell K, Lobley GE, Rawlings J, Millward DJ, Harper EJ. Urea kinetics of a carnivore, Felis silvestris catus. Br J Nutr. 2000 Nov;84(5):597-604.


Taurine - Key Message

WALTHAM has contributed to the understanding of the taurine requirement of the cat by:

  • Determining how much taurine is needed in canned and dry prepared pet foods.
  • Demonstrating that kittens get taurine from the queen via the placenta.

Background

Taurine (2-aminoethanesulfonic acid) is an end-product of sulphur amino acid metabolism that is widely distributed in animal tissues. Taurine is an essential nutrient for cats that must be present in the diet (Burger 1993). This is because the cat cannot synthesise sufficient taurine from dietary sulphur-containing amino acids, compounded by dependence on taurine for the formation of bile salts (being unable to conjugate bile acids to glycine) (Legrand-Defretin 1994).

Taurine deficiency causes retinal degeneration (Hayes et al. 1975) as well as poor reproductive performance in breeding females, poor growth in kittens, and dilated cardiomyopathy in adult cats (Sturman et al. 1986; Pion et al. 1987; Pion et al. 1989).

Why WALTHAM is Interested

As an essential nutrient, taurine must be provided in prepared petfood at an adequate level, which requires an understanding of how much the cat needs.

Initial studies into the taurine requirements of cats used semi-purified diets (Burger and Barnett 1982). Purified diets use simple ingredients in a highly available form (such as individual amino acids, soya protein, casein, dextrose) to enable the formulation of a diet with a defined nutrient profile – this is common practice when investigating the nutrient requirements of any species.

However, it became clear that prepared petfood needed separate consideration. Early data suggested that canned food needed to contain more taurine than dried diets to maintain normal plasma taurine concentrations (Pion et al. 1989).

Approach

WALTHAM investigated the taurine requirement of the cat by feeding diets containing various levels of taurine and measuring taurine status (plasma taurine concentration). The metabolism of taurine was also investigated, looking at taurine transport across the placenta.

Discovery (Taurine Requirement)

Canned cat food must contain more taurine than dry cat food

The first study, in collaboration with the Animal Health Trust Small Animals Centre, Newmarket, investigated the adult cat’s minimum requirement for taurine using a semi-purified diet (Burger and Barnett 1982).

Subsequently, WALTHAM investigated the taurine requirement of adult cats being fed canned or dry diets (Earle and Smith 1991). The results showed that to maintain normal plasma taurine levels, a canned diet must supply at least 39 mg taurine/kg body weight/day and a dry diet at least 19 mg/kg body weight/day (Figure 4) (Earle and Smith 1991). This was the first study to demonstrate the dietary taurine intake required from canned and dry diets. It is an important part of the literature on the taurine requirement of the cat, and contributes to the NRC recommendation for nutrient requirements in cats (NRC 2006).

Dietary taurine content
Reproduced from Earle KE, Smith PM. The effect of dietary taurine content on the plasma taurine concentration of the cat. Br J Nutr. 1991.66(2):227-235. http://journals.cambridge.org/abstract_S0007114591000843

Figure 4: Taurine level required in diets of different formats to maintain the plasma taurine status of adult cats (Earle and Smith 1991)

Following on from these studies in adult cats, the taurine requirement of kittens was investigated. This study found that the bioavailability of taurine from canned food was higher for kittens than for adult cats, although they exhibited much greater variability in response (Earle and Smith 1994).

Discovery (Taurine Transport)

Studies of taurine transport across the placenta show that kittens obtain taurine from the queen

In other species, the placenta provides the foetus with essential nutrients. The mechanism by which the queen supplied taurine to the kittens in utero was not known.

This work was conducted in collaboration with scientists at the University of Manchester (Champion et al. 2004; Champion et al. 2005). Taurine uptake was characterised in placental fragments obtained from queens during normal parturition. For the first time, it was shown that the cat placenta possesses amino acid transport systems that are functionally similar to the system β and system A transporters of the human placenta (Champion et al. 2004).

References

Burger IH. A basic guide to nutrient requirements. In: The Waltham book of companion animal nutrition. Editor: IH Burger. Pergamon Press, Oxford. 1993, pages 5-24.


Burger IH, Barnett KC. The taurine requirement of the adult cat. J Small Anim Pract. 1982;23(9):533-537.


Champion EE, Mann SJ, Glazier JD, Jones CJ, Rawlings JM, Sibley CP, Greenwood SL. System beta and system A amino acid transporters in the feline endotheliochorial placenta. Am J Physiol Regul Integr Comp Physiol. 2004 Dec;287(6):R1369-79.


Earle KE, Smith PM. The taurine requirement of the kitten fed canned foods. J Nutr. 1994 Dec;124(12 Suppl):2552S-2554S.


Earle KE, Smith PM. The effect of dietary taurine content on the plasma taurine concentration of the cat. Br J Nutr. 1991 Sep;66(2):227-35.


Hayes KC, Carey RE, Schmidt SY. Retinal degeneration associated with taurine deficiency in the cat. Science. 1975 May 30;188(4191):949-51.


Legrand-Defretin V. Differences between cats and dogs: a nutritional view. Proc Nutr Soc. 1994 Mar;53(1):15-24.


Pion PD, Kittleson MD, Rogers QR. Cardiomyopathy in the cat and its relation to taurine deficiency. In: Current Veterinary Therapy, Volume 10. Editor: RW Kirk. WB Saunders, Philadelphia. 1989, pages 251-262.


Pion PD, Kittleson MD, Rogers QR, Morris JG. Myocardial failure in cats associated with low plasma taurine: a reversible cardiomyopathy. Science. 1987 Aug 14;237(4816):764-8.


Sturman JA, Gargano AD, Messing JM, Imaki H. Feline maternal taurine deficiency: effect on mother and offspring. J Nutr. 1986 Apr;116(4):655-67.


Iron - Key Message

WALTHAM has helped to establish the iron requirement of cats by:

  • Generating insight into the dietary iron content that supports normal growth of kittens.

Background

Iron is an essential nutrient that must be provided in the diet. It has multiple functions, being a constituent of haemoglobin and myoglobin as well as many enzymes (Burger 1993).

Iron deficiency typically manifests as anaemia (McCrown and Specht 2011), with abnormally low haemoglobin and haematocrit values reported in kittens (Chausow and Czarnecki-Maulden 1987).

The amount of dietary iron needed to ensure normal iron metabolism in kittens was established using semi-purified diets (Chausow and Czarnecki-Maulden 1987). However, these diets were of high bioavailability (casein and dextrose) and were also phytate- and fibre-free (Chausow and Czarnecki-Maulden 1987); two constituents known to reduce iron bioavailability in other species (Lopez and Martos 2004).

Why WALTHAM is Interested

The iron requirement of kittens was established using semi-purified diets (with high bioavailability). However, when fed commercially available prepared petfoods the iron requirements of kittens were not known.

Approach

The health, growth, and development of kittens were monitored when fed standard commercial diets to confirm that the iron content was adequate.

Insight Generation (Iron)

Kittens consuming commercial diets with normal iron content grow and develop normally

In a study at WALTHAM, two groups of 8-week-old kittens were fed for 10 weeks on nutritionally complete canned diets containing either 7.66 mg or 7.75 mg Fe/400 kcal (Harper et al. 2000). Both diets supported normal growth and development, and at the end of the study all haematological and clinical parameters were confirmed to be within the normal ranges (Harper et al. 2000). This study showed that the amount of iron present in these typical commercial diets was sufficient to support the growing kitten. These data were taken into account when formulating the NRC recommendation for iron (NRC 2006).

References

Burger IH. A basic guide to nutrient requirements. In: The Waltham book of companion animal nutrition. Editor: IH Burger. Pergamon Press, Oxford. 1993, pages 5-24.


Chausow DG, Czarnecki-Maulden GL. Estimation of the dietary iron requirement for the weanling puppy and kitten. J Nutr. 1987;117(5):928-32.


Harper EH, Skinner N, Charlton C, Smith B. Iron requirements for growth and development in kittens. FASEB J. 2000;14:A227 [Abstract 164.8].


López MA, Martos FC. Iron availability: An updated review. Int J Food Sci Nutr. 2004;55(8):597-606.


McCown JL, Specht AJ. Iron homeostasis and disorders in dogs and cats: a review. J Am Anim Hosp Assoc. 2011;47(3):151-60.


National Research Council. Nutrient Requirements of Dogs and Cats, 2006. National Academy Press, Washington.


Calcium - Key Message

WALTHAM helped establish the calcium requirement of cats by:

  • Demonstrating that when receiving adequate dietary vitamin D, the calcium requirement of kittens is less than was thought.

Background

Calcium is an essential nutrient that must be provided in the diet. It is required for normal growth and development of the skeleton, and is mostly stored in bone. A small amount of extracellular calcium mediates functions including vasodilation, muscular contraction, and nerve transmission. The calcium concentration of plasma is kept under very tight homeostatic control, in part controlled by vitamin D which increases calcium absorption from the gut.

Secondary hyperparathyroidism has been reported in cats (Krook et al. 1963; Tomsa et al. 1999), most often due to calcium deficiency caused by an all-meat diet.

For a long time the calcium requirement of kittens was set at 8–10 g/kg diet, based on very early calcium balance studies (see Morris et al. 1999a).

Why WALTHAM is Interested

Because of their metabolic relationship, the adequacy of dietary calcium content can be affected by vitamin D status. Having established the vitamin D requirement of kittens (Morris et al. 1999b), the calcium requirement needed reassessing using diets containing an adequate level of vitamin D.

Approach

The health, growth, and development of kittens were monitored when fed diets containing varying levels of calcium and a level of vitamin D confirmed to be adequate.

Discovery (Calcium)

When receiving adequate vitamin D, the calcium requirement of growing kittens is less than was thought

This work was conducted in collaboration with Dr James G Morris, of the University of California, Davis.

Kittens were fed a range of test diets from 9–18 weeks of age and their calcium status monitored by blood samples and dual-energy X-ray absorptiometry (Morris et al. 1999a). The five diets had a calcium:phosphorus ratio of 1:1.25 and 3.125 μg of cholecalciferol/kg, with calcium levels ranging from 3.8–8.1 g calcium/kg diet and a metabolisable energy content of about 20 kJ/g. Growth rate, energy intake, and plasma total calcium was normal on all these diets, with no clinical signs of calcium deficiency (Morris et al. 1999a). However, kittens on the lowest calcium diet had a lower bone mineral content than the others, showing that this level of calcium (3.8 g/kg diet) was suboptimal (Morris et al. 1999a). Other studies with 6 g calcium/kg diet showed that although a calcium:phosphorus ratio of 1:1.55 was adequate, an inverse ratio of 1:2.61 affected calcium and phosphorus metabolism (Morris et al. 1999a).

This study concluded that the calcium requirement of kittens was no more than 6 g/kg diet – much less than previously thought to be required (Morris et al. 1999a) – and these data were subsequently taken into account when formulating the NRC recommendation for calcium (NRC 2006).

References

Krook L, Barrett RB, Usui K, Wolke RE. Nutritional secondary hyperparathyroidism in the cat. Cornell Vet. 1963;53:224-40.


Morris JG, Earle KE. Growing kittens require less dietary calcium than current allowances. J Nutr. 1999a;129(9):1698-704.


Morris JG, Earle KE, Anderson PA. Plasma 25-hydroxyvitamin D in growing kittens is related to dietary intake of cholecalciferol. J Nutr. 1999b;129(4):909-12.


National Research Council. Nutrient Requirements of Dogs and Cats, 2006. National Academy Press, Washington.


Tomsa K, Glaus T, Hauser B, Flückiger M, Arnold P, Wess G, Reusch C. Nutritional secondary hyperparathyroidism in six cats. J Small Anim Pract. 1999;40(11):533-9.


Vitamin D - Key Message

WALTHAM helped establish the vitamin D requirement of cats by:

  • Demonstrating the dietary vitamin D content that meets the needs for growth of kittens.

Background

The main function of vitamin D is to increase calcium and phosphorus absorption from the gut, and mobilise calcium from bone.

Most animals can synthesise vitamin D in the skin. However, vitamin D synthesis by growing kittens exposed to ultraviolet light is ineffective (Morris 1999). This means they need a dietary source of vitamin D, which is ordinarily provided in the wild by prey items (Morris 1999).

Vitamin D deficiency classically causes rickets, and has been previously reported in cats (Gershoff et al. 1957).
The vitamin D requirement of kittens was established in very early studies (Gershoff et al. 1957). However, these data are questionable due to the high mortality rate (Morris et al. 1999).

Why WALTHAM is Interested

Vitamin D is an essential nutrient for kittens, and it is important to understand how much they need in order to provide food that supports growth and healthy development.

Approach

The amount of dietary vitamin D (as cholecalciferol) necessary to maintain adequate plasma levels of 25-hydroxyvitamin D (25-OHD) was investigated.

Discovery (Vitamin D)

The vitamin D requirement of growing kittens is less than was thought

This work was conducted in collaboration with Dr James G Morris, of the University of California, Davis.

Kittens aged 9 weeks were fed diets (20 kJ/g metabolisable energy) containing 12 g calcium and 8 g phosphorus, and 0–25 μg of cholecalciferol/kg diet (Morris et al. 1999). There were no adverse clinical effects nor radiographic abnormalities observed at 22 or 34 weeks of age (Morris et al. 1999). Plasma concentrations of 25-OHD were highly correlated with dietary cholecalciferol (Morris et al. 1999). At 22 weeks of age, the kittens fed 6.25 μg cholecalciferol/kg diet had plasma 25-OHD concentrations greater than 50 nmol/L – the level which is considered replete for humans – and this was identified as the vitamin D requirement for kittens (Morris et al. 1999).

This study showed that the vitamin D requirement of kittens was much less than previously thought (Morris et al. 1999), and these data were subsequently taken into account when formulating the NRC recommendation (NRC 2006).

References

Gershoff SN, Legg MA, O'Connor FJ, Hegsted DM. The effect of vitamin D-deficient diets containing various Ca:P ratios on cats. J Nutr. 1957;63(1):79-93.


Morris JG. Ineffective vitamin D synthesis in cats is reversed by an inhibitor of 7-dehydrocholestrol-delta7-reductase. J Nutr. 1999;129(4):903-8.


Morris JG, Earle KE, Anderson PA. Plasma 25-hydroxyvitamin D in growing kittens is related to dietary intake of cholecalciferol. J Nutr. 1999;129(4):909-12.


National Research Council. Nutrient Requirements of Dogs and Cats, 2006. National Academy Press, Washington.


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Site owner...

Mars Incorporated

100 International Drive
Mount Olive NJ 07828
US


Phone Number: 1.9736913500
Email Address: contact@uk.mars.com
Registration number: 6649984
VAT Number: GB 209 3486 57
Site owner

Site owner

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