History

Dog Nutrient Requirement

Key Message

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

•    Showing that the energy requirement is affected by many factors including body size, breed, and activity level.
•    Demonstrating that energy requirement can be predicted more accurately if the dog’s daily activity level is taken into account using accelerometry.

Background

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

•    Basal metabolic rate
     o    The energy expended to maintain basic physiological functions (including heart beat, respiration and muscle function). It is usually measured as resting metabolic rate – that is, the energy expended to maintain the body whilst lying down and awake.

•    Thermogenesis
     o    The energy expended to ingest, digest, absorb and assimilate food
     o    The energy expended to cope with stress, including changes in environmental temperature

•    Activity
     o    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 dogs varies over a huge range – from about 1 kg to over 100 kg (Burger 1994). Because of this body weight should be expressed on an allometric basis, but the precise value for the exponent to calculate MW is still a matter of some debate (Burger 1994).

Why WALTHAM is Interested

A thorough understanding of energy requirements is essential in order to produce accurate feeding guidelines to help owners feed their dog appropriately and to prevent under-nutrition or obesity. Complete and balanced foods rely on delivering all essential nutrients within the calories the dog requires to maintain a healthy bodyweight.

Approach

Over time, WALTHAM has undertaken a great many feeding studies of dogs 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 dogs which are maintaining their body weight have an energy intake equivalent to energy requirement.

There are several widely accepted techniques for accurately measuring the energy expenditure of an animal. Whole body colorimetry measures energy as heat production (or indirectly calculates this) under carefully defined conditions. Doubly-labelled water measures metabolic rate in the free-living state. Both techniques require considerable experience and expertise, which WALTHAM has developed. Furthermore, the use of multiple techniques to assess energy requirements is a way to try to overcome the inherent variability in the data.

Discovery

The energy requirement of dogs is affected by many factors including body size, breed, and activity level

In a study of 22 dogs representing seven breeds (body weight range 5.8–48.8 kg) at WALTHAM, whole body calorimetry found a resting energy expenditure of 678 W0.64 kJ/day (Burger and Johnson 1991). These data were taken into account in formulating the NRC 2006 recommendations (NRC 2006).

A study in collaboration with the College of Veterinary Medicine, Hannover, found that the Newfoundland requires less energy than might be predicted, and great Danes require more, after analysing the body weight data from 78 dogs representing seven breeds (Figure 1) (Kienzle and Rainbird 1991). These data suggest that breed may be a confounding factor when considering energy requirements, perhaps due to coat type, body composition or temperament.

Relationship
Reproduced from Kienzle E, Rainbird A. Maintenance energy requirement of dogs: what is the correct value for the calculation of metabolic body weight in dogs? J Nutr.1991.121(11Supp):39S-40S

Figure 1: Relationship between body weight and energy intake for maintenance (Kienzle and Rainbird 1991)

Another of the confounding factors when considering energy requirements is the level of physical activity. A survey of border collies kept as working dogs or pets revealed widely varying energy requirements based on activity level (Table 1 Burger 1994).

Table 1: Survey of food intake in Border collies kept as working dogs or pets (Burger 1994). Data are mean ± SD
Energy requirements
Reproduced from Burger IH. Energy needs of companion animals: matching food intakes to requirements throughout the life cycle. J Nutr. 1994 Dec;124(12 Supp):2584S-2593S


This variation due to activity level may also underlie the effect of age, whereby younger dogs have a higher energy requirement than older dogs (Kienzle and Rainbird 1991). In contrast, gender has no effect on energy requirement (Kienzle and Rainbird 1991).

Discovery

Energy requirement can be predicted more accurately if the dog’s daily activity level is taken into account using accelerometry

A study at WALTHAM evaluated using triaxial accelerometry to measure daily activity as a predictor of individual maintenance energy requirement (MER) in dogs (Wrigglesworth et al. 2011). Triaxial accelerometers are used in humans and other species, and record acceleration in all three orthogonal planes. For this study, triaxial accelerometers were designed and manufactured at WALTHAM, and attached to each dog’s collar.

In the study, 10 healthy adult Labrador retrievers wore an accelerometer for two 2-week periods. Data on daily activity were successfully collected for 24 to 26 days. Along with body weight, these data were used as independent variables in a multiple linear regression model to predict the dependent variable of daily MER, and the predictive accuracy of the model compared with one that excluded activity. Observed MER was taken to be the dietary energy intake that maintained stable body weight.

The model that included both body weight and daily activity predicted observed MER with a mean absolute error of 63.5 kcal and an SE of estimation of 94.3 kcal (Wrigglesworth et al. 2011). In comparison, when activity was removed from the model, the predictive accuracy was reduced to a mean absolute error of 129.8 kcal and an SE of estimation of 165.4 kcal (Wrigglesworth et al. 2011).

This study showed that triaxial accelerometers provide an independent variable of daily activity that markedly improves the predictive accuracy of the regression model, compared with using only body weight (Wrigglesworth et al. 2011). Improved accuracy in estimations of MER could be made if an accelerometer was used for each dog to record its daily activity.

References

Burger IH. Energy needs of companion animals: matching food intakes to requirements throughout the life cycle. J Nutr. 1994 Dec;124(12 Suppl):2584S-2593S.


Burger IH, Johnson JV. Dogs large and small: the allometry of energy requirements within a single species. J Nutr. 1991 Nov;121(11 Suppl):S18-21.


Kienzle E, Rainbird A. Maintenance energy requirement of dogs: what is the correct value for the calculation of metabolic body weight in dogs? J Nutr. 1991 Nov;121(11 Suppl):S39-40.


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


Wrigglesworth DJ, Mort ES, Upton SL, Miller AT. Accuracy of the use of triaxial accelerometry for measuring daily activity as a predictor of daily maintenance energy requirement in healthy adult Labrador Retrievers. Am J Vet Res. 2011 Sep;72(9):1151-5.

Protein - Key Message

WALTHAM has contributed to the knowledge of the protein requirements of the dog by:

•    Measuring endogenous nitrogen losses in adult dogs.
•    Assessing the sulphur amino acid requirements of growing puppies.

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 (for example for protein synthesis and the production of other nitrogen-containing compounds). 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.

Why WALTHAM is Interested

Understanding the amino acid and protein requirements of the dog is fundamental to providing optimum nutrition.

Approach

WALTHAM assessed the endogenous nitrogen losses of adult dogs, and determined the sulphur-containing amino acid requirements for growth.

Discovery (Adult)

The endogenous nitrogen loss of adult dogs reflects their minimal nitrogen requirement

In an early study at WALTHAM, the endogenous nitrogen losses (in the urine and faeces) of adult dogs were measured. Daily total endogenous nitrogen output was found to be 273 ± 9 mg/kg0.75 (Kendall et al. 1982). This measurement is a fundamental part of the knowledge of the protein requirement of any species.. It is the obligatory nitrogen loss from the body and hence reflects the minimal nitrogen requirement.

Discovery (Growth)

Adequate dietary sulphur amino acids result in normal growth of puppies

A study at WALTHAM determined the weight gain of puppies fed diets with various levels of methionine and cysteine (Blaza et al. 1982). The study found that the requirement for total sulphur-containing amino acids was 155 mg per 100 kcal metabolisable energy (Blaza et al. 1982). If the puppies were fed diets containing less than this, they gained body weight at a lower rate (Figure 2 Blaza et al. 1982). These data have been taken into account in formulating the NRC 2006 recommendations (NRC 2006).

Bodyweight
Reproduced from Blaza SE, Burger IH, Holme DW, Kendall PT. Sulfur-containing amino acid requirements of growing dogs. J Nutr. 1982 Nov;112(11):2033-42.

Figure 2: Body weight gain of six individual littermate beagles fed on three levels of methionine (Blaza et al. 1982)

References

Blaza SE, Burger IH, Holme DW, Kendall PT. Sulfur-containing amino acid requirements of growing dogs. J Nutr. 1982 Nov;112(11):2033-42.


Kendall PT, Blaza SE, Holme DW. Assessment of endogenous nitrogen output in adult dogs of contrasting size using a protein-free diet. J Nutr. 1982 Jul;112(7):1281-6.


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


Zinc - Key Message

WALTHAM has contributed to the knowledge of the zinc requirements of dogs by:

•    Showing the levels of dietary zinc that supports healthy growth of puppies.

Background

Zinc is an essential nutrient that must be provided in the diet. Its functions are multiple and include catalytic (zinc is a cofactor in many enzymes) and structural (zinc helps to stabilise some protein structures [zinc fingers]) roles.

Zinc deficiency in dogs has been reported. It is termed zinc-responsive dermatosis (Colombini 1999) and manifests as poor growth rate and skin lesions.

The NRC 1985 recommended requirement for zinc in puppies was thought to be very low – close to that reported to cause deficiency (Booles et al. 1991).

Why WALTHAM is Interested

Zinc is an essential nutrient for puppies, and it is important to understand how much they need in order to grow and develop normally.

Approach

WALTHAM fed two levels of zinc to puppies and monitored their growth and development.

Discovery

Adequate dietary zinc results in normal growth of puppies

In a study in collaboration with the University of Liverpool, Labrador retriever puppies were fed diets containing 50 or 200 mg zinc/kg diet (Booles et al. 1991). All the puppies grew normally (Figure 3) and had normal plasma zinc values (Booles et al. 1991). This study showed that 50 mg zinc/kg diet was sufficient to support the healthy growth of puppies, and these data were subsequently taken into account when formulating the NRC recommendation for zinc (NRC 2006).

Figure 1
Reproduced from Booles D, Burger IH, Whyte AL, Anderson RS, Carlos GM, Robinson IP. Effects of two levels of zinc intake on growth and trace element status in Labrador puppies. J Nutr.1991;121(11 Supp):79S-80S

Figure 3: Mean body weights of Labrador puppies receiving either 50 (? n=8) or 200 (? n=10) mg Zn/kg diet (Booles et al. 1991)

This study also found that the zinc metalloprotein, metallothionein, reflected zinc status in the dog, as had been found in other species (Booles et al. 1991).

Another study in collaboration with the University of Liverpool measured the zinc, copper, iron, and calcium concentrations of bitch milk to understand how much of these minerals puppies were receiving prior to weaning (Anderson et al. 1991).

References

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


Anderson RS, Carlos GM, Robinson IP, Booles D, Burger IH, Whyte AL. Zinc, copper, iron and calcium concentrations in bitch milk. J Nutr. 1991;121(11 Suppl):S81-2.


Booles D, Burger IH, Whyte AL, Anderson RS, Carlos GM, Robinson IP. Effects of two levels of zinc intake on growth and trace element status in Labrador puppies. J Nutr. 1991;121(11 Suppl):S79-80.


Colombini S. Canine zinc-responsive dermatosis. Vet Clin North Am Small Anim Pract. 1999;29(6):1373-83.


Vitamin A - Key Message

WALTHAM has contributed to the knowledge of the vitamin A requirements of dogs by:

•    Establishing the safe upper level for dietary vitamin A in growing puppies.

Background

Vitamin A is an essential fat soluble vitamin. It must be provided in the diet, but as in other species, excessive vitamin A intake in dogs is undesirable. Excessive vitamin A results in severe adverse effects including abnormal bone development, pain, and reduced growth (Cho et al. 1975). It is therefore important to understand the safe upper limit of dietary intake.

The safe upper limit for inclusion of vitamin A in complete diets for growing dogs is uncertain. There are few published data available, and since the metabolism and excretion of vitamin A in the dog differs from that of other species (see Morris et al. 2012), this makes cross-species extrapolation problematical.

A lack of published data has resulted in a lack of consensus on the safe upper limit for vitamin A in complete diets for growing dogs, with recommendations ranging from 5.24–104.80 ?mol retinol (5000–100,000 IU vitamin A)/1000 kcal (4184 kJ) metabolisable energy (Morris et al. 2012).

Why WALTHAM is Interested

Vitamin A is an essential nutrient for puppies, and it is important to understand how much they need in order to grow and develop normally. As a fat soluble vitamin, it is essential that dietary levels are sufficient but not excessive.

Approach

WALTHAM fed different amounts of vitamin A to puppies and monitored their health in order to establish a safe upper level.

Discovery

There are no adverse effects when puppies are fed a diet containing 104.80 ?mol retinol (100,000 IU vitamin A)/1000 kcal (4184 kJ) metabolisable energy

This study compared the effect of feeding four concentrations of vitamin A to puppies from weaning until 1 year of age (Morris et al. 2012). The hypothesis was that feeding dietary retinol concentrations up to 104.80 ?mol retinol/1000 kcal (that is, the highest currently recommended maximum) to puppies would not affect biomarkers associated with health. The study was a collaboration between WALTHAM and scientists from the Freie Universität Berlin and the University of Potsdam, Germany.

The 49 puppies (Labrador retriever and miniature schnauzer) were randomly assigned to one of four groups following weaning at 8 weeks of age and fed a complete diet supplemented with retinyl acetate to achieve an intake of 5.24, 13.10, 78.60 or 104.80 ?mol retinol/1000 kcal metabolisable energy (vitamin A equivalent 5000, 12,500, 75,000 and 100,000 IU/4184 kJ).

Markers of vitamin A metabolism and safety (including clinical examination, haematology and biochemistry, and dual-energy X-ray absorptiometry) were monitored repeatedly up to 52 weeks of age. 
No dose-effects were seen (with the exception of total serum retinyl esters), and there was no effect of dose on adverse events (number, type, and duration) (Morris et al. 2012). Poor faeces quality was the most commonly reported adverse event, occurring in 20 dogs, all resolving within 3 days. Two Labradors exhibited lameness without apparent cause (one in the 5.24 ?mol group and one in the 78.60 ?mol group); both cases resolved in less than 7 days following treatment.

This study supports the adoption of 104.80 ?mol retinol (100,000 IU vitamin A)/4184 kJ (1000 kcal) as a suitable safe upper level for puppy growth diets (Morris et al. 2012).

References

Cho DY, Frey RA, Guffy MM, Leipold HW. Hypervitaminosis A in the dog. Am J Vet Res. 1975 Nov;36(11):1597-1603.


Morris PJ, Salt C, Raila J, Brenten T, Kohn B, Schweigert FJ, Zentek J. Safety evaluation of vitamin A in growing dogs. Br J Nutr. 2012 Feb 28:1-10. [Epub ahead of print]


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