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Feeding Dried Rabbit Faeces to Growing Rabbits
Br. vet .}. (1 978 ), 134, 393
FEEDING DRIED RABBIT FAECES TO GROWING RABBITS By]. O. L.
KING
University of Liverpool, Veterinary Field Station, Neston, Wirral
SUMMARY
A total of 310 rabbits were used in two six-week feeding experiments to assess the value of including dried rabbit faeces in the diet. In the first experiment the incl usion levels were 10 and 15%. The rabbits on the 10% diet increased in liveweight more rapidly and those on the 15% diet more slowly than the co ntrols, but the results were not significant. The food conversion ratios were higher on both faeces-conta ining diets while the killing-out percentages were significantly higher. In the second experiment the 10% inclusion level was used alone or in combination with zinc bacitracin. The only significant findings were that the faeces-p lusantibiotic diet red uced the weights of the stomach, small intestine and caecum when these were expressed as percentages of the body weights. Similar significant differences were found from a comparison of the faeces-p lus-antibiotic and the normal antibiotic diet, showing that the antibiotic had a more marked effect in the presence of faeces. INTROD UCT ION
T he marked increase in the price of the feeding stuffs normally used in rabbit diets has stimulated a n interest in the use of cheaper foods, and, in particular, the substitution of the more expensive protein constituents by other forms of feed. One such product is dried rabbit faeces; the use of this material was investigated. Additional studies were co nducted to determine whether the inclusion of an antibiotic in rations containing rabbit faeces influenced the utilization of this product, although King ( 1971) found that the feeding of oxytetracycline hydrochloride did not significantly affect the response to rabbit diets containing urea.
MATERIALS AND METHODS
Rabbits Two six-week experiments were conducted. Most of the rabbits were Californian x New Zealand Whites, but some were Dutch. In the first experiment 150 rabb its were divided into gro ups of three. Each trio was made up of rabbits of the same breed, age and sex from the same litter or from closely related parents ; each rabbit was then allocated to one of the three diets. In the second experiment 160
394
BRITISH VETE RINARY JOURNAL, 134, 4
rabbits were divided into groups of four, care being taken, as before, to select similar rabbits to form each quartet.
Housing Thc:t rabbits were placed in wire mesh cages when weaned at about four weeks of age and were fed a proprietary meal ration for one week so that they became accustomed to the management conditions before the experimental rations were started. Each cage held two or three rabbits, all on the same diet. Feeding The faeces used came from rabbits housed in cages with wire mesh floors and fed on pellets in unspillable troughs so that their faeces were not mixed with any food. The rabbits were healthy and, in particular, were free from salmonella infection , and were fed on diets which did not contain an antibiotic. Q.uantitites of faeces were p laced in bowls in an oven and kept at between 65 and 70°C for two days until dry. The material was then ground to a powder which could be mixed easily with other meals. The make-up and analyses of the rations fed are given in Table I. In the first experiment, each third of the rabbits were fed on ration N, For FF. In the second experiment each quarter received either ration N, F, N plus zinc bacitracin 100 g/ton (NA) or F plus zinc bacitracin 100 g/ton (FA ). This antibiotic was selected since King (I976) found that the live-weight gain of rabbits was significantly increased when fed at this level (King, 1976). The meals were fed ad libitum and free access to water was allowed.
TABLE I ~
THE MAKE -U P AND ANALYSES OFTHE RAT IO NS FED TO GROW I NG RABBITS
Quantity in ration (%)
Foodstuff Maize meal Soya bean meal Barley meal Grassmeal Dried rabbit faeces Vit/ minmix
N
F
FF
28 9 46 15
28 9 46
2
28 9 46 5 10 2
100
100
100
15 2
Chemical analyses (%) Nutrient Protein Fat Carbohydrate Fibre Ash
13· 76 2 · 74 59 ·05 6·24 326
13·63 2·35 55·30 6 ·51 3·95
13·5 7 2· 15 53·4 1 6 ·64 4 30
395
FEEDING DRIED RABBIT FAECES TO GROWING RABBITS
Individual figures for food consumption were not kept because th e rabbits were not housed separately, but the amounts of food consumed by the rabbits kept in each cage were recorded in the case of 38 rabbits on each of the three diets in experiment I and all the rabbits in experiment 2. The findings have been expressed as food co nversion ratios. Post-mortem examinations At the end of experiment 2 all the rabbits were killed by dislocating their necks and post-mortem examination commenced within 30 min of death . The small intes tine a nd caec um (without the appendix) were measured while lying on a wet, stainless-steel draining board to avoid any artificial stretching. The stomach, small intestine and caecum were then opened and their contents removed under a gentl e stream of water. They were allowed to drain for 15 min and weighed. The liver was placed on a piece of fi lter paper to remove any exuded blood and then weighed . These operations were performed by one person to eliminate differences in handling techniques. Direct comparisons of organ lengths and weights between treated and untreated pairs could not be made as the rabbits were usually of different body weights, and so, to circumvent the effects of body weights on organ weights , the individual organ weights have been expressed as percentages of body weight, and, in the case of the small intes tine and caecum, as the weights of I cm lengths. The killing-out percentage for each rabbit was calculated as the weight of the carcass after bleeding and the removal of the skin, head , fore-legs below the knee, hind legs below the hock, intestines, liver, heart and lu..ngs expressed as a percentage of th e liveweight immediately before killing. The rabbits were not starved before they were killed. Killing-out percentages were recorded for 40 rabbits on each diet in experiment I and all the rabbits in experiment 2. The significances of the findings were determined by the application of the t-test. RES ULTS
The rabbits on the diet containing 10% dried rabbit faeces (F) gained weight more rapidly than did those on the control diet, although the differences in the means were not significant (Table 10. The rabbits receiving the diet containing 15% dried faeces (FF) grew more slowly than the controls but, again, the differences in th e means were TABLEII THE EF FECTS OF F EE DI NG G ROWIN G RABBITS A DIET C O NTA I N IN G 10% ( F ) OR 15% ( FF ) DRIED R A BBIT FAECES COMPARED WITH A CONTROL DI ET ( N ) OVER A SIX · W EE K PERIOD
F
Mean live -weigh t gain (g) Food co nversion ratio: I Killing o ut %
N
F-N
J.e.
FF
N
FF-N
J. e.
9751 (50) 953 ·6 (50) +21 ·5 40 ·326 9118 (50 ) 9536 (50 ) -41 8 39 · 737 4 ·59 (38 ) 4 ·55 (38 ) + 0 ·04 0 · 18 5 4·77 (38 ) 4·55 (38 ) + 0 22 0 · 177 5 1·38 (40 ) 49 ·48 (40 ) + 1·90 '" 0·918 52 -48 (40 ) 49-48 (40 ) + 3·00 '"'' 0·958
• P
396
BRITISH VETERINARY JOURNAL, 134, 4
not significant. In the second experiment the rabbits on the diet containing 10% dried faeces (F) gained weight more rapidly than did those on the control diet (Table III). The rabbits receiving rati6 ns containing zinc bacitracin grew more rapidly than those not receiving antibiotic. When the two rations containing zinc bacitracin are compared the rabbits on the one containing the faeces grew mo re rapidly. None of the differences in live-weight gain were significant. TABLE III THE EF F ECTS O F FEEDING G ROWIN G RABBITS A CONT ROL DI ET I N ) C OMPARED WITH A DI ET CONTA I N I NG 10% DRI ED RA BBIT FAECES IF), N P LUS ZI NC B ACIT RA C I N INA ) OR F PL US ZI NC BACITRACI N IFA J( 100 g/ton )
F-N
Live-weight gain (g) Liver % wt. Stomach % wt. Small intestine % wt. Caecum %wt. Small intestine wt. of I cm(g) Caecum wt. of I em (g ) Food eonversionratio : I Killing o ut %
FA-NA
Difference
s.e.
+40·2 + 0·09 0·02 + 0·06 + 0 ·02
28471 0 · 134 0 ·028 0 ·080 0 ·047
0·012 + 0·001 + 0·02 + 1·03
0·007 0 ·040 0 · 105 0 ·801
FA-F
NA-N
Difference
s.e.
28·753 + 19 ·8 0 · 107 + 0·1 I 0·07·· 0·027 0 · 15 · 0·069 0 · 12 ·· 0·043
+ 35· 7 + 0 · 11 002 0 ·03 0 ·01
27· 923 0 · 11 5 0 ·028 0 ·07 3 0·042
0 ·00 2 0 ·032 0 · 12 + \.4 5
-
Difference
s.e.
0 ·006 0·033 0·166 0·844
0 ·026 0·030 0·02 + 0· 35
0·007 0 ·038 o· 128 0 ·684
Difference
S.e.
29 ·28 4 + 15·3 0·127 0 ·03 0·07· 0 028 O· 24 0 ·0 77 0·15 * * 0 ·048
*.
-
0 ·016 0·063 0·16 + O· 7 7
• P < 0 ·05 . •• P
40 rabbits on each diet. s.e. standard error of the differences of the mean'
A study of the organ weight:> of the rabbits on the normal diet and the one containing 10% offaeces shows that the inclusion offaeces did not alter any of the weights significantly (Table III). A comparison of the normal ration with the antibiotic-fortified normal diet again did not demonstrate any significant changes, although , on average, the sections of the alimentary canal studied were all reduced in weight by the antibiotic. When the results of feeding the faeces diet are compared with those obtained by giving the faeces-plus-antibiotic ration the antibiotic significantly reduced the percentage weights of the stomach, small intestine and caecum. A study of the weights obtained by feeding the two antibiotic-fortified diets revealed similar changes as the faeces -plusantibiotic diet significantly reduced the weights of all sections of the alimentary canal studied, significantly in the case of the percentage weights of the stomach, small intestines and caeca. In all cases when the diets without an antibiotic were fed the food conversion ratio showed that the rabbits receiving the faeces- fortified diets utilized their food less efficiently. The antibiotic-fortified foods increased food utilization efficiency (Table III). However, the differences were all marginal and not significant. In the first experiment the killing-out percentages were significantly higher in the rabbits on the diets containing faeces at both the inclusion levels. The results given in
0 ·006 0 ·035 0·148 0·942
FEEDING DRIED RABBIT FAECES TO GROWING RABBITS
397
Table III show that in the second experiment the killing-out percentage was also higher in the diets containing faeces and in the antibiotic-fortified rations, but the differences were not significant. DISCUSSION
The results of these experiments show that dried rabbit faeces can be satisfactorily included in the rations fed to growing rabbits at a level of 10%. The rabbits readily ate the rations, always looked well and showed no signs of any digestive upsets. Although there were no apparent ill effects when the material was fed at an inclusion rate of 15%. the reduction in the rate oflive-weight gain indicates that this level is too high. The practical value of the finding that dried rabbit faeces can be fed to growing rabbits to the commercial rabbit industry is dependent on the expense incurred in recycl ing the rabbit faeces. Unfortunately it is not possible to estimate this cost from the work recorded in this paper because of the small quantities of rabbit faeces dried and ground weekly. On a large scale, assuming that the faeces are avai lable on the site so that transport costs could be eliminated and handling charges minimized, the cost would be limited to the expense incurred in drying and grinding. The total cost of these operations should be well below the price of alternative foods of a similar value. Various dryers and pulverisers, which have been developed for handling poultry faeces from large scale battery units economically, are now available and would be suitable. Additionally there would be a national saving, if dried animal and poultry faeces co uld be used successfully in animal feeding, by a reduction in imported animal foodstuffs. The observations on the two rations containing the antibiotic indi cate that this had a greater effect in reducing the weights of the stomach, small intestine and caecum, when these were expressed as percentages of body weight, in the presence of faeces . The non-significant increases in the percentage weights of the small intestine and caecum shown when the results for the rabbits given the faeces-containing ration witho ut an antibiotic were compared with the normal diet could have contributed slightly to this finding, but this argument would not apply in the case of the stomachs. ACKNOWLEDGEM ENTS
The author wishes to thank A/S Apothekernes Laboratorium for Specialpraeparater, Postboks 158, Skoyen, Oslo 2, Norway, for the gift of the zinc bacitracin, Dr C. D. Rosen for helpful advice and Miss S. A. Pleavin for undertaking the statistical examination of the results. REFERENCES
KING,]. O . L. (197 I). Br. vet.J. 127, 523. KI NG, ]. O . L. (19 76). Vet. Rec. 99,507 .
(Acceptedfor publication 25 September 1977)
FEEDING DRIED RABBIT FAECES TO GROWING RABBITS By]. O. L.
KING
University of Liverpool, Veterinary Field Station, Neston, Wirral
SUMMARY
A total of 310 rabbits were used in two six-week feeding experiments to assess the value of including dried rabbit faeces in the diet. In the first experiment the incl usion levels were 10 and 15%. The rabbits on the 10% diet increased in liveweight more rapidly and those on the 15% diet more slowly than the co ntrols, but the results were not significant. The food conversion ratios were higher on both faeces-conta ining diets while the killing-out percentages were significantly higher. In the second experiment the 10% inclusion level was used alone or in combination with zinc bacitracin. The only significant findings were that the faeces-p lusantibiotic diet red uced the weights of the stomach, small intestine and caecum when these were expressed as percentages of the body weights. Similar significant differences were found from a comparison of the faeces-p lus-antibiotic and the normal antibiotic diet, showing that the antibiotic had a more marked effect in the presence of faeces. INTROD UCT ION
T he marked increase in the price of the feeding stuffs normally used in rabbit diets has stimulated a n interest in the use of cheaper foods, and, in particular, the substitution of the more expensive protein constituents by other forms of feed. One such product is dried rabbit faeces; the use of this material was investigated. Additional studies were co nducted to determine whether the inclusion of an antibiotic in rations containing rabbit faeces influenced the utilization of this product, although King ( 1971) found that the feeding of oxytetracycline hydrochloride did not significantly affect the response to rabbit diets containing urea.
MATERIALS AND METHODS
Rabbits Two six-week experiments were conducted. Most of the rabbits were Californian x New Zealand Whites, but some were Dutch. In the first experiment 150 rabb its were divided into gro ups of three. Each trio was made up of rabbits of the same breed, age and sex from the same litter or from closely related parents ; each rabbit was then allocated to one of the three diets. In the second experiment 160
394
BRITISH VETE RINARY JOURNAL, 134, 4
rabbits were divided into groups of four, care being taken, as before, to select similar rabbits to form each quartet.
Housing Thc:t rabbits were placed in wire mesh cages when weaned at about four weeks of age and were fed a proprietary meal ration for one week so that they became accustomed to the management conditions before the experimental rations were started. Each cage held two or three rabbits, all on the same diet. Feeding The faeces used came from rabbits housed in cages with wire mesh floors and fed on pellets in unspillable troughs so that their faeces were not mixed with any food. The rabbits were healthy and, in particular, were free from salmonella infection , and were fed on diets which did not contain an antibiotic. Q.uantitites of faeces were p laced in bowls in an oven and kept at between 65 and 70°C for two days until dry. The material was then ground to a powder which could be mixed easily with other meals. The make-up and analyses of the rations fed are given in Table I. In the first experiment, each third of the rabbits were fed on ration N, For FF. In the second experiment each quarter received either ration N, F, N plus zinc bacitracin 100 g/ton (NA) or F plus zinc bacitracin 100 g/ton (FA ). This antibiotic was selected since King (I976) found that the live-weight gain of rabbits was significantly increased when fed at this level (King, 1976). The meals were fed ad libitum and free access to water was allowed.
TABLE I ~
THE MAKE -U P AND ANALYSES OFTHE RAT IO NS FED TO GROW I NG RABBITS
Quantity in ration (%)
Foodstuff Maize meal Soya bean meal Barley meal Grassmeal Dried rabbit faeces Vit/ minmix
N
F
FF
28 9 46 15
28 9 46
2
28 9 46 5 10 2
100
100
100
15 2
Chemical analyses (%) Nutrient Protein Fat Carbohydrate Fibre Ash
13· 76 2 · 74 59 ·05 6·24 326
13·63 2·35 55·30 6 ·51 3·95
13·5 7 2· 15 53·4 1 6 ·64 4 30
395
FEEDING DRIED RABBIT FAECES TO GROWING RABBITS
Individual figures for food consumption were not kept because th e rabbits were not housed separately, but the amounts of food consumed by the rabbits kept in each cage were recorded in the case of 38 rabbits on each of the three diets in experiment I and all the rabbits in experiment 2. The findings have been expressed as food co nversion ratios. Post-mortem examinations At the end of experiment 2 all the rabbits were killed by dislocating their necks and post-mortem examination commenced within 30 min of death . The small intes tine a nd caec um (without the appendix) were measured while lying on a wet, stainless-steel draining board to avoid any artificial stretching. The stomach, small intestine and caecum were then opened and their contents removed under a gentl e stream of water. They were allowed to drain for 15 min and weighed. The liver was placed on a piece of fi lter paper to remove any exuded blood and then weighed . These operations were performed by one person to eliminate differences in handling techniques. Direct comparisons of organ lengths and weights between treated and untreated pairs could not be made as the rabbits were usually of different body weights, and so, to circumvent the effects of body weights on organ weights , the individual organ weights have been expressed as percentages of body weight, and, in the case of the small intes tine and caecum, as the weights of I cm lengths. The killing-out percentage for each rabbit was calculated as the weight of the carcass after bleeding and the removal of the skin, head , fore-legs below the knee, hind legs below the hock, intestines, liver, heart and lu..ngs expressed as a percentage of th e liveweight immediately before killing. The rabbits were not starved before they were killed. Killing-out percentages were recorded for 40 rabbits on each diet in experiment I and all the rabbits in experiment 2. The significances of the findings were determined by the application of the t-test. RES ULTS
The rabbits on the diet containing 10% dried rabbit faeces (F) gained weight more rapidly than did those on the control diet, although the differences in the means were not significant (Table 10. The rabbits receiving the diet containing 15% dried faeces (FF) grew more slowly than the controls but, again, the differences in th e means were TABLEII THE EF FECTS OF F EE DI NG G ROWIN G RABBITS A DIET C O NTA I N IN G 10% ( F ) OR 15% ( FF ) DRIED R A BBIT FAECES COMPARED WITH A CONTROL DI ET ( N ) OVER A SIX · W EE K PERIOD
F
Mean live -weigh t gain (g) Food co nversion ratio: I Killing o ut %
N
F-N
J.e.
FF
N
FF-N
J. e.
9751 (50) 953 ·6 (50) +21 ·5 40 ·326 9118 (50 ) 9536 (50 ) -41 8 39 · 737 4 ·59 (38 ) 4 ·55 (38 ) + 0 ·04 0 · 18 5 4·77 (38 ) 4·55 (38 ) + 0 22 0 · 177 5 1·38 (40 ) 49 ·48 (40 ) + 1·90 '" 0·918 52 -48 (40 ) 49-48 (40 ) + 3·00 '"'' 0·958
• P
396
BRITISH VETERINARY JOURNAL, 134, 4
not significant. In the second experiment the rabbits on the diet containing 10% dried faeces (F) gained weight more rapidly than did those on the control diet (Table III). The rabbits receiving rati6 ns containing zinc bacitracin grew more rapidly than those not receiving antibiotic. When the two rations containing zinc bacitracin are compared the rabbits on the one containing the faeces grew mo re rapidly. None of the differences in live-weight gain were significant. TABLE III THE EF F ECTS O F FEEDING G ROWIN G RABBITS A CONT ROL DI ET I N ) C OMPARED WITH A DI ET CONTA I N I NG 10% DRI ED RA BBIT FAECES IF), N P LUS ZI NC B ACIT RA C I N INA ) OR F PL US ZI NC BACITRACI N IFA J( 100 g/ton )
F-N
Live-weight gain (g) Liver % wt. Stomach % wt. Small intestine % wt. Caecum %wt. Small intestine wt. of I cm(g) Caecum wt. of I em (g ) Food eonversionratio : I Killing o ut %
FA-NA
Difference
s.e.
+40·2 + 0·09 0·02 + 0·06 + 0 ·02
28471 0 · 134 0 ·028 0 ·080 0 ·047
0·012 + 0·001 + 0·02 + 1·03
0·007 0 ·040 0 · 105 0 ·801
FA-F
NA-N
Difference
s.e.
28·753 + 19 ·8 0 · 107 + 0·1 I 0·07·· 0·027 0 · 15 · 0·069 0 · 12 ·· 0·043
+ 35· 7 + 0 · 11 002 0 ·03 0 ·01
27· 923 0 · 11 5 0 ·028 0 ·07 3 0·042
0 ·00 2 0 ·032 0 · 12 + \.4 5
-
Difference
s.e.
0 ·006 0·033 0·166 0·844
0 ·026 0·030 0·02 + 0· 35
0·007 0 ·038 o· 128 0 ·684
Difference
S.e.
29 ·28 4 + 15·3 0·127 0 ·03 0·07· 0 028 O· 24 0 ·0 77 0·15 * * 0 ·048
*.
-
0 ·016 0·063 0·16 + O· 7 7
• P < 0 ·05 . •• P
40 rabbits on each diet. s.e. standard error of the differences of the mean'
A study of the organ weight:> of the rabbits on the normal diet and the one containing 10% offaeces shows that the inclusion offaeces did not alter any of the weights significantly (Table III). A comparison of the normal ration with the antibiotic-fortified normal diet again did not demonstrate any significant changes, although , on average, the sections of the alimentary canal studied were all reduced in weight by the antibiotic. When the results of feeding the faeces diet are compared with those obtained by giving the faeces-plus-antibiotic ration the antibiotic significantly reduced the percentage weights of the stomach, small intestine and caecum. A study of the weights obtained by feeding the two antibiotic-fortified diets revealed similar changes as the faeces -plusantibiotic diet significantly reduced the weights of all sections of the alimentary canal studied, significantly in the case of the percentage weights of the stomach, small intestines and caeca. In all cases when the diets without an antibiotic were fed the food conversion ratio showed that the rabbits receiving the faeces- fortified diets utilized their food less efficiently. The antibiotic-fortified foods increased food utilization efficiency (Table III). However, the differences were all marginal and not significant. In the first experiment the killing-out percentages were significantly higher in the rabbits on the diets containing faeces at both the inclusion levels. The results given in
0 ·006 0 ·035 0·148 0·942
FEEDING DRIED RABBIT FAECES TO GROWING RABBITS
397
Table III show that in the second experiment the killing-out percentage was also higher in the diets containing faeces and in the antibiotic-fortified rations, but the differences were not significant. DISCUSSION
The results of these experiments show that dried rabbit faeces can be satisfactorily included in the rations fed to growing rabbits at a level of 10%. The rabbits readily ate the rations, always looked well and showed no signs of any digestive upsets. Although there were no apparent ill effects when the material was fed at an inclusion rate of 15%. the reduction in the rate oflive-weight gain indicates that this level is too high. The practical value of the finding that dried rabbit faeces can be fed to growing rabbits to the commercial rabbit industry is dependent on the expense incurred in recycl ing the rabbit faeces. Unfortunately it is not possible to estimate this cost from the work recorded in this paper because of the small quantities of rabbit faeces dried and ground weekly. On a large scale, assuming that the faeces are avai lable on the site so that transport costs could be eliminated and handling charges minimized, the cost would be limited to the expense incurred in drying and grinding. The total cost of these operations should be well below the price of alternative foods of a similar value. Various dryers and pulverisers, which have been developed for handling poultry faeces from large scale battery units economically, are now available and would be suitable. Additionally there would be a national saving, if dried animal and poultry faeces co uld be used successfully in animal feeding, by a reduction in imported animal foodstuffs. The observations on the two rations containing the antibiotic indi cate that this had a greater effect in reducing the weights of the stomach, small intestine and caecum, when these were expressed as percentages of body weight, in the presence of faeces . The non-significant increases in the percentage weights of the small intestine and caecum shown when the results for the rabbits given the faeces-containing ration witho ut an antibiotic were compared with the normal diet could have contributed slightly to this finding, but this argument would not apply in the case of the stomachs. ACKNOWLEDGEM ENTS
The author wishes to thank A/S Apothekernes Laboratorium for Specialpraeparater, Postboks 158, Skoyen, Oslo 2, Norway, for the gift of the zinc bacitracin, Dr C. D. Rosen for helpful advice and Miss S. A. Pleavin for undertaking the statistical examination of the results. REFERENCES
KING,]. O . L. (197 I). Br. vet.J. 127, 523. KI NG, ]. O . L. (19 76). Vet. Rec. 99,507 .
(Acceptedfor publication 25 September 1977)