Some freshly published research for you - from this month's edition of the Journal of Feline Medicine and Surgery.
Evaluation of two raw diets vs a commercial cooked diet on feline growth
Hamper, Bartges and Kirk. JFMS (2017) 19: 424-434
Link to abstract: https://www.ncbi.nlm.nih.gov/pubmed/26927818
My ramblings below:
Background to this study
This was performed at the University of Tennessee, USA. The authors had no involvement with any pet food company and no conflicts of interest; this was an independent study.
The aim of this study was to test two raw diets, to see if they were adequate for normal growth in young kittens by comparing them to a commercial canned food and by following AAFCO protocols for assessing diets (see below).
While it wasn't the main aim of the research, they also tested for any evidence of pathogens such as Salmonella, Campylobacter and Clostridium in the kittens, since this is a common concern with raw feeding.
How commercial diets are tested to ensure they are suitable for growing kittens (in the States)
AAFCO (the Association of American Feed Control Officials) is the regulating body in the USA that sets the guidelines and protocols by which any pet food manufacturer must design their products.
When it comes to testing a new diet's effect on growth, the following protocol must be followed:
How the study was performed
The kittens
A total of 24 kittens were used in this research. All were born and housed in the university lab, and had the same parents. Five litters were involved over a space of three years. They were all initially weaned onto a wet/dry mix of Hills Science Diet. At the end of the study, all the kittens were rehomed to private homes or transferred to a permanent research colony, where they were involved in non-invasive research for other projects.
The diets
Three diets were used:
1. The control diet - a cooked, canned diet (Evo Turkey & Chicken from Natura). This diet had previously passed AAFCO testing and had been deemed adequate for growth. It's actually not a bad-looking diet - grain free, with a high protein content (>40% DM basis).
http://www.evopet.com/products/1401
2. A commercial raw diet - Chicken & Clam Frozen Raw Diet from Wild Kitty Raw. This diet had also passed AAFCO testing. It is no longer in production so I can't link it.
3. A 'home-made' raw diet consisting of store-bought chicken breast, supplemented with a commercial supplement (TC Feline Plus Cat Food Premix from TC Feline). The supplement was used according to manufacturer's instructions. The diet contained no bone or offal - just breast meat.
http://tcfeline.com/tcfeline-canada/
How the kittens were fed
All five litters went through testing, but were split between the diets. In total, 8 kittens were fed the control diet, another 8 were fed the commercial raw and another 8 fed the 'home-made' raw.
They all started their respective diets at nine weeks of age and continued them for ten weeks, in line with the AAFCO protocol. They were all fed three times daily, and received nothing else during the test period apart from water.
What was tested, and what did they find?
Growth
The kittens were weighed, measured (height and length) and condition scored once weekly. At the end of the 10 weeks, there was NO difference in the rate of growth of all kittens, regardless of which diet they ate.
Blood tests were carried out at weeks 0, 5 and 10 of the test period.
Serum protein levels
All three diets passed the AAFCO test, in that serum protein levels were satisfactory in all the kittens after ten weeks. They did find that serum albumin levels were slightly lower in the kittens fed the raw diets, but considered this negligible. Conversely, the serum globulin levels were higher in the kittens fed the raw diets. The authors couldn't rule out this being the result of mild inflammation due to exposure to enteropathic bacteria.
Red blood cell parameters
All three diets passed the AAFCO test, in that none of the kittens were anaemic after ten weeks. However, there was a potentially interesting finding.
In the kittens fed the control diet, the PCV ('packed cell volume' - a measure of the number of red blood cells in the blood) and haemoglobin levels rose over the ten week period. This is considered a normal finding: as kittens grow, their haemopoeitic system matures and we normally find that the lower PCV and haemoglobin levels they were born with normalise to higher, adult levels.
However, in the kittens fed the raw diets, the PCV and haemoglobin - while never low - seemed to plateau by the end of the test period and stopped rising. The reasons for this were unclear, but could have been related to a iron or copper deficiency (the mineral content of the diets was not analysed due to financial restrictions) OR could be related to low-grade intestinal inflammation in the case of subclincial infection by enteropathic bacteria. Inflammatory processes result in the body sequestering iron away, so there is less available for haemoglobin production.
Taurine
Again, all three diets passed the AAFCO test, in that all the kittens' taurine levels were normal at the end of the ten weeks.
Interestingly, the kittens on the home-made raw diet had increasing taurine levels over the ten week period - but those on the commercial raw diet had decreasing levels. While their taurine levels were never low, it's unclear whether they would have become so had the testing continued beyond ten weeks or whether things would have stabilised. That's potentially a little concerning.
Analysis of the three diets found that the taurine contents of the control and commercial raw diets were about the same. Unsurprisingly, the taurine content of the home-made raw diet was about three times higher; this probably accounts for the rising taurine levels in the kittens fed this diet.
Faecal testing
This got a little complicated, but I'll try to explain their processes and findings as best I can. Faecal cultures for Salmonella, Campylobacter and Clostridium were performed.
Faeces were analysed from all kittens at weeks 0 and 10 (plus week 5 for the kittens on the home-made raw diet). To save on costs, these samples were all pooled together and sent off for pooled culture - they were NOT organised into groups according to diet.
If the results of the group culture were negative, no further action was taken.
If the results of the group culture were positive, only then did they test the kittens individually to see where the source of the bacteria was. This only happened twice throughout the entire study, both involving Salmonella. In these cases, they also cultured the diets to see if there were any bacteria in the diet.
On the first occasion, all the individual cultures came back negative and the diets were all negative as well, so the source was never identified. Given that these organisms are often shed intermittently in the faeces, I guess it's possible that whichever kitten(s) was/were shedding were only doing intermittently and the second round of cultures simply missed something the pooled sample picked up.
On the second occasion, the Salmonella was traced back to one kitten eating the home-made raw diet. This kitten had no symptoms whatsoever. The diet itself was again found to be negative for Salmonella.
Faecal cultures were also performed on any kittens who had diarrhoea lasting for two or more days. This happened eight times throughout the study.
Interestingly, 75% of the kittens with diarrhoea in this study were eating the control diet - diarrhoea was actually less common in the kittens on raw diets. However, we need to be very careful interpreting all of this, as there are many complicating factors.
For example, of the six control kittens with diarrhoea, three had negative faecal results and the other three tested positive for C. perfringens, which can be a normal bacterial resident of the feline intestine. It's possible that their diarrhoea was not caused by bacterial infection but perhaps other factors: viruses, parasites or dietary intolerance (no information on the biosecurity or worming regime of the kittens was provided, although one would assume they would be free of viruses and parasites in a laboratory setting).
On the other side of the coin, faecal cultures can yield false negatives (as discussed above). It's not possible to 100% rule out infectious causes of diarrhoea in the kittens who yielded negative cultures.
Another concern I had with this study is that the kittens were house separately, but allowed 'group play' daily. It wasn't clear to me from the words 'group play' whether they were allowed to play only with kittens eating the same diet as themselves, or the entire litter. If the kittens were indeed mixing with each other regardless of diet, then it complicates the identification of any source of bacteria because they could have been spread through grooming etc - not just the food. They should have clarified this, really.
Both kittens with diarrhoea who were fed the home-made raw diet had positive findings on their faecal analysis: one case of C. perfringens, and one of C. difficile. In addition, the one kitten identified as carrying Salmonella was also fed the home-made raw. Again, the significance of these results is unclear as positive results don't always correlate with infection and other cases could have been missed due to false negatives - but it isn't a good advertisement for the home-made raw diet they used.
I will point out here, since it's relevant, that the home-made raw diet was made in batches every two weeks and frozen immediately. Meals were defrosted 24 hours prior to being given and refrigerated in the interim. Bowls and utensils were cleaned thoroughly. So it seems that hygiene measures were satisfactory.
Overall I agree with the authors that further research is needed into this faecal pathogen thing. 24 kittens is a very small number from which to draw firm conclusions - although it would be remiss not to mention that multiple studies have previously shown the presence of enteropathic bacteria in the faeces of dogs and cats fed raw diets.
SUMMARY
Overall, the raw diets performed well in terms of facilitating growth in these kittens, and didn't seem to result in any more diarrhoea than kittens on the control diet. Findings on bloodwork *could* be consistent with low-grade intestinal inflammation related to bacterial infection, but it's only supposition. The taurine content of all three diets was satisfactory, but there was a bit of a worrying decrease in the kittens eating the commercial raw over the ten week period. Analysis over a longer period would be needed to see if that continued or stabilised.
Evaluation of two raw diets vs a commercial cooked diet on feline growth
Hamper, Bartges and Kirk. JFMS (2017) 19: 424-434
Link to abstract: https://www.ncbi.nlm.nih.gov/pubmed/26927818
My ramblings below:
Background to this study
This was performed at the University of Tennessee, USA. The authors had no involvement with any pet food company and no conflicts of interest; this was an independent study.
The aim of this study was to test two raw diets, to see if they were adequate for normal growth in young kittens by comparing them to a commercial canned food and by following AAFCO protocols for assessing diets (see below).
While it wasn't the main aim of the research, they also tested for any evidence of pathogens such as Salmonella, Campylobacter and Clostridium in the kittens, since this is a common concern with raw feeding.
How commercial diets are tested to ensure they are suitable for growing kittens (in the States)
AAFCO (the Association of American Feed Control Officials) is the regulating body in the USA that sets the guidelines and protocols by which any pet food manufacturer must design their products.
When it comes to testing a new diet's effect on growth, the following protocol must be followed:
- The diet must be tested on at least eight kittens, from nine weeks of age (doesn't seem that many, right?)
- It must be compared to a control diet that has previously been estbalished to be adequate for growth.
- The testing period must be at least ten weeks, during which the kittens must be fed the test diet only with no other foods or supplements.
- The kittens must gain the same amount of weight as the kittens on the control diet for the food to pass the test.
- The kittens must not be anaemic, have low blood protein levels or low serum taurine levels by the end of the ten weeks.
How the study was performed
The kittens
A total of 24 kittens were used in this research. All were born and housed in the university lab, and had the same parents. Five litters were involved over a space of three years. They were all initially weaned onto a wet/dry mix of Hills Science Diet. At the end of the study, all the kittens were rehomed to private homes or transferred to a permanent research colony, where they were involved in non-invasive research for other projects.
The diets
Three diets were used:
1. The control diet - a cooked, canned diet (Evo Turkey & Chicken from Natura). This diet had previously passed AAFCO testing and had been deemed adequate for growth. It's actually not a bad-looking diet - grain free, with a high protein content (>40% DM basis).
http://www.evopet.com/products/1401
2. A commercial raw diet - Chicken & Clam Frozen Raw Diet from Wild Kitty Raw. This diet had also passed AAFCO testing. It is no longer in production so I can't link it.
3. A 'home-made' raw diet consisting of store-bought chicken breast, supplemented with a commercial supplement (TC Feline Plus Cat Food Premix from TC Feline). The supplement was used according to manufacturer's instructions. The diet contained no bone or offal - just breast meat.
http://tcfeline.com/tcfeline-canada/
How the kittens were fed
All five litters went through testing, but were split between the diets. In total, 8 kittens were fed the control diet, another 8 were fed the commercial raw and another 8 fed the 'home-made' raw.
They all started their respective diets at nine weeks of age and continued them for ten weeks, in line with the AAFCO protocol. They were all fed three times daily, and received nothing else during the test period apart from water.
What was tested, and what did they find?
Growth
The kittens were weighed, measured (height and length) and condition scored once weekly. At the end of the 10 weeks, there was NO difference in the rate of growth of all kittens, regardless of which diet they ate.
Blood tests were carried out at weeks 0, 5 and 10 of the test period.
Serum protein levels
All three diets passed the AAFCO test, in that serum protein levels were satisfactory in all the kittens after ten weeks. They did find that serum albumin levels were slightly lower in the kittens fed the raw diets, but considered this negligible. Conversely, the serum globulin levels were higher in the kittens fed the raw diets. The authors couldn't rule out this being the result of mild inflammation due to exposure to enteropathic bacteria.
Red blood cell parameters
All three diets passed the AAFCO test, in that none of the kittens were anaemic after ten weeks. However, there was a potentially interesting finding.
In the kittens fed the control diet, the PCV ('packed cell volume' - a measure of the number of red blood cells in the blood) and haemoglobin levels rose over the ten week period. This is considered a normal finding: as kittens grow, their haemopoeitic system matures and we normally find that the lower PCV and haemoglobin levels they were born with normalise to higher, adult levels.
However, in the kittens fed the raw diets, the PCV and haemoglobin - while never low - seemed to plateau by the end of the test period and stopped rising. The reasons for this were unclear, but could have been related to a iron or copper deficiency (the mineral content of the diets was not analysed due to financial restrictions) OR could be related to low-grade intestinal inflammation in the case of subclincial infection by enteropathic bacteria. Inflammatory processes result in the body sequestering iron away, so there is less available for haemoglobin production.
Taurine
Again, all three diets passed the AAFCO test, in that all the kittens' taurine levels were normal at the end of the ten weeks.
Interestingly, the kittens on the home-made raw diet had increasing taurine levels over the ten week period - but those on the commercial raw diet had decreasing levels. While their taurine levels were never low, it's unclear whether they would have become so had the testing continued beyond ten weeks or whether things would have stabilised. That's potentially a little concerning.
Analysis of the three diets found that the taurine contents of the control and commercial raw diets were about the same. Unsurprisingly, the taurine content of the home-made raw diet was about three times higher; this probably accounts for the rising taurine levels in the kittens fed this diet.
Faecal testing
This got a little complicated, but I'll try to explain their processes and findings as best I can. Faecal cultures for Salmonella, Campylobacter and Clostridium were performed.
Faeces were analysed from all kittens at weeks 0 and 10 (plus week 5 for the kittens on the home-made raw diet). To save on costs, these samples were all pooled together and sent off for pooled culture - they were NOT organised into groups according to diet.
If the results of the group culture were negative, no further action was taken.
If the results of the group culture were positive, only then did they test the kittens individually to see where the source of the bacteria was. This only happened twice throughout the entire study, both involving Salmonella. In these cases, they also cultured the diets to see if there were any bacteria in the diet.
On the first occasion, all the individual cultures came back negative and the diets were all negative as well, so the source was never identified. Given that these organisms are often shed intermittently in the faeces, I guess it's possible that whichever kitten(s) was/were shedding were only doing intermittently and the second round of cultures simply missed something the pooled sample picked up.
On the second occasion, the Salmonella was traced back to one kitten eating the home-made raw diet. This kitten had no symptoms whatsoever. The diet itself was again found to be negative for Salmonella.
Faecal cultures were also performed on any kittens who had diarrhoea lasting for two or more days. This happened eight times throughout the study.
- In 4 kittens, the diarrhoea was tentatively linked to Clostridium perfringens. Three of these kittens were eating the control diet; one was on the home-made raw.
- In 3 kittens, there was no growth of anything on culture. These three were all on the control diet.
- In one kitten, Clostridium difficile toxin was identified in the faeces. This kitten was on the home-made raw.
Interestingly, 75% of the kittens with diarrhoea in this study were eating the control diet - diarrhoea was actually less common in the kittens on raw diets. However, we need to be very careful interpreting all of this, as there are many complicating factors.
For example, of the six control kittens with diarrhoea, three had negative faecal results and the other three tested positive for C. perfringens, which can be a normal bacterial resident of the feline intestine. It's possible that their diarrhoea was not caused by bacterial infection but perhaps other factors: viruses, parasites or dietary intolerance (no information on the biosecurity or worming regime of the kittens was provided, although one would assume they would be free of viruses and parasites in a laboratory setting).
On the other side of the coin, faecal cultures can yield false negatives (as discussed above). It's not possible to 100% rule out infectious causes of diarrhoea in the kittens who yielded negative cultures.
Another concern I had with this study is that the kittens were house separately, but allowed 'group play' daily. It wasn't clear to me from the words 'group play' whether they were allowed to play only with kittens eating the same diet as themselves, or the entire litter. If the kittens were indeed mixing with each other regardless of diet, then it complicates the identification of any source of bacteria because they could have been spread through grooming etc - not just the food. They should have clarified this, really.
Both kittens with diarrhoea who were fed the home-made raw diet had positive findings on their faecal analysis: one case of C. perfringens, and one of C. difficile. In addition, the one kitten identified as carrying Salmonella was also fed the home-made raw. Again, the significance of these results is unclear as positive results don't always correlate with infection and other cases could have been missed due to false negatives - but it isn't a good advertisement for the home-made raw diet they used.
I will point out here, since it's relevant, that the home-made raw diet was made in batches every two weeks and frozen immediately. Meals were defrosted 24 hours prior to being given and refrigerated in the interim. Bowls and utensils were cleaned thoroughly. So it seems that hygiene measures were satisfactory.
Overall I agree with the authors that further research is needed into this faecal pathogen thing. 24 kittens is a very small number from which to draw firm conclusions - although it would be remiss not to mention that multiple studies have previously shown the presence of enteropathic bacteria in the faeces of dogs and cats fed raw diets.
SUMMARY
Overall, the raw diets performed well in terms of facilitating growth in these kittens, and didn't seem to result in any more diarrhoea than kittens on the control diet. Findings on bloodwork *could* be consistent with low-grade intestinal inflammation related to bacterial infection, but it's only supposition. The taurine content of all three diets was satisfactory, but there was a bit of a worrying decrease in the kittens eating the commercial raw over the ten week period. Analysis over a longer period would be needed to see if that continued or stabilised.
