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Food metabolizability and water balance in intact and cecectomized great-horned owls
FOOD ~ETABOLIZABILITY AND WATER BALANCE IN INTACT AND CECECTOMIZED GREAT-HORNED OWLS G. E. DUKE, J. E. BIRD, K. A. DANIELS and R. W. BERTOY Department of Veterinary Biology, University of Minnesota, St Paul, MN 55108. U.S.A. (Receioed 6 May 1980) Abstract--l. In great-horned owls food metabolizabiIity, food intake and body weight were not significantly affected by cecectomy. 2. Following cecectomy. water ingestion increased,
2 weeks at which time 2 birds were eliminated from the
INTRODUCFIDN
Cecal function has been somewhat well studied in galliforms (e.g. Beattie & Shrimpton,
1958; Thornburn
&
Wilcox, 1965; Moss & Parkinson, 1972; Inman, 1973; Gasaway, 1976; Hanssen, 1979). As in mammals, bacterial degradation of dietary fiber is believed to be the
experiment because of failure to eat well and to adjust to the cages and frequent handling. At this time 4 owls were randomly selected for cecectomy and three for sham operations. Daily determinations of weight of food and water ingested, weight of excreta and pellet wastes, and body weights were begun. The experiment lasted for 119 days as rollows:
days - 10 to - I-pre-operative ;a;
(pre-op.) period
of surgery days I to 25 and 101 to lO9-post
primary cecal activity (Ziswiler & Farner, 1972; Duke, 1977; Stevens, 1977). Water absorption, including urinary water reabsorption, also appears to be a major function of avian ceca (Duke, 1977; McNab, 1973; Sturkie, 1976). We have not found reports of studies on cecal function in carnivorous birds despite the existence of ceca in several carnivorous orders (Ziswiler & Farner, 1972). The ceca of owls have been examined histologically (Naik & Dominic, 1969) and they are described as highly glandular. The presence of ceca may not be related to dietary habits in carnivores, since although owls and hawks generally eat similar diets, owls have ceca while hawks do not (Duke, 1978). It is thus difficult to hypothesize as to the likely function of ceca in owls. Our objectives were, therefore, to initiate investigations of cecal function in owls through a study of food metabolizability and water balance .in intact (sham operated) and ceeectomized great-horned owls Bubo virginianus). The studies were part of our continuing effort to gain new knowledge on gastrointestinal function in raptors to aid in their management and conservation. MATERIALS AND METHODS
Nine permanently crippled but otherwise healthy adult great-horned owls (B&o ui~gj~j~~us) were used. They were held in individual cages (46 x 46 x 61 cm) in environmentally controlled rooms in which temperature was maintained between 2l-23°C. relative humidity was kept between 40 and 50% and the photoperiod was automatically timed to provide 14 hr of light from 0700 to 2100 hr. The owls were allowed to acclimate to these conditions for 237
operative (post-op.) period. Data For days 1-7 indicated that recovery from surgery was not complete, consequently these data were not used. Also, daily handling appeared to cause increased nervousness in the owls resulting in declines in food intake and body weight so, body weights and weights of ingesta and waste were not determined for days lb20 to allow the owls to recover. These weights were determined during days 101-109 to see if measurements made during the first 25 days after cecectomy might change by 101-109 days post-op. One of the four cecectomized owls became ill, lost weight and died on day 85. Necropsy revealed an apparent atonicity at the ileoceococolic junction and an accumulation of ingesta orad to the junction. Standard surgical procedures were followed during the cecectomies. A laparotomy was performed and the viscera manipulated in the sham procedure. A preanesthetic of Ketamine-HCI (Ketaset, Bristol Veterinary Products, Syracuse, N.Y.) (lOmg/kg) and Xylazine (Rompun, Cutter Labs. Inc., Shawnee Kan.) (I mg/kg) was used to allow owls to be connected to a gas anesthesia machine. Methoxyflurane (Metofane. Pittman-Moore. Inc.. Wash. Crossinn. N.J.) was then used to maintain a surgical plane of anesthi: sia. The diet for the experiment was whole laboratory mice (Mm musculus) which were fresh or thawed from fresh frozen supplies. Meals of mice were weighed and presented to the owls at 1200 hr. Mice or parts of mice remaining at 1500 hr were collected and weighed. The room was checked once or twice during this period and food that had dropped through the mesh floor of the owl cages was returned to the owls. Excreta were collected in stainless steel trays under each owl cage. Immediately prior to feeding each day, the trays containing excreta were removed and replaced with clean trays. Pellets were also collected. Water pans for each owl and a “control” pan. used to evaluate evaporation. were also weighed and refilled as required at this time. Additionally the owls were weighed.
When the above procedures were completed and the owls had been given their daily ration of mice, excreta were taken to an adjacent laboratory and carefully scraped from each tray: the wet weight of excreta and pellets was determined. Since these were not fresh excreta (likewise for pellets), absolute water losses in wastes could not be ascertained. However, excreta were collected at the same time and in the same manner each da}. so relative water losses before and after surgery and in cecectomized vs sham-operated birds could be determined. Durmg the period 101-109 days post-op., humidity controls in the animal room were not operating properly. We were not aware of this problem until after completing the experiments and begmnmg calculation of moisture content in wastes and amount of evaporation occurring daily. By comparing evaporative losses from the “control” water pan during days 101-109 to losses m earlier periods we were able to adjust quantities of water Ingested during days 101 109 to values comparable to those during earlier periods. Since we had no “control” tray of cxcreta. mformation on the proportion of water in. and evaporation of water from. excreta during days I01 I09 could not be adjusted and was. therefore. not usable. Excreta and pellets were dried at 60 C for 24 hr and rewelghed to provide dry weights. The weight eaten also was converted to dry weight. Average dry matter in mice is of dry 37.X”,, (Duke et u/.. 1975). After determination weights of food and waste (excreta plus pellets), weight of water consumed. and dally individual body weights. a daily food metabolizability was determined as follows: metabolirability
coefficlcnt
= I ~
dry wt waste dry wt food
Percent body weight change per day was calculated. Mean values for food and water intake, food metabolizability, excreta moisture and daily body weight change were
determmed for the pre-op. period and lor day5 h I C.2 1 2:. and IOI--109 of the post-op. period. Mean value\ for each parameter (e.g.food Intake) were compared via a Student’5 f-test among and between the pre-op and post-op. periods RESLILTS AhD DISC‘LSSIOU
Food metabolizabiht) and body weight changes did not appear to be affected b) cecectomy (Tables i and 2). Food intake by cecectomized owls has me\plicably low during days 101 109 and. therefore. significantly lower than intake by these owls during daqs X-15 and 21L25; it uas also lo\\er than intake by intact owls during days IOL 109. This IOU mtakr resulted in significant weight loss during that period (Table 2) but. since this loss was recovered immediately after the experiment when owls were returned to their normal holding room. it is believed to be due IU the experimental conditions rathrr than to the cecectomy which occurred over IO0 days earlier. Food intake was lower immediately following surger! in both the cecectomized and the sham-operated owls. As a result intake increased in both cecectomized and sham-operated owls during days S25 after surgery. Thus, the surgery, not the absence of ceca. seems to account for this increase. Food intake, therefore. also did not appear to be intluenced by cecectom!. Although average daily water Intake seemed rathet variable in the intact owls. intake in the cecectomired birds did appear to increase following cecectomv and to remain higher in cecectomized owls than in intact ones (Table 1). If the ceco are involved in crater absorption, this change is readill explained. The greatest daily water intake within the group of cececto-
Table I. Mean food and water intake (g/kg/day). excrela moisture (Y,,). food metabolizability (“J. and body weight changes (“,,A BW:day) in intact (I) sham-operated and cecectomized (C) Great-horned owls Period* Condition of owl
Parameter Water
intake
C
I Food
intake
c
I Food
metabol.
C I
Excreta
moist.
c I
Body wt change
C I
Pre-op. 16.9 (13.1)** 24.0 (22.4) 16.6 (7.21) 16.7 (5.90) 58.2 (6.70) 59.5 (6.60) 59.8 (X.75) 52.7 (10.4) -0.20 (0.96) - 0.09 (0.95)
* Pre-op. = preoperative period; Post-op (day of surgery) to day I09 post-surgery. ** Numbers in parentheses are SD. t Data not available; see text.
day x -15 27.2 (16.4) 7.39 (10.9) 20. t (7.80) ‘1.3 (6.78) 61.2 (7.61) 59.8 (4.32) 70.0 (6.44) 63.X (6.X6) +0.32 (1.92) + 0.27 (0.98) = postoperative
Post-op day 21-25 I X.6 (12.4) 12.5 (10.7) 20.0 (4.33) 2 I .9 (5.83) 61.1 (4.01) 61.X (3.43) 67.4 (12.5) 62. I (7.53) - 0.09 (0.80) -0.20 (1.13)
day 101-109 17.2 (I 1.4) 8.6s (10.0) 13.4 (6.35) 19.0 (5.53) 60.2 (5 Xl 60.9 (5.X21 NAt NAt NAt NAt -0.38 (0.32) + 0. I 5 (0.14)
period including
day 0
239
Food metabolizability and water balance in great-horned owls
Table 2. Results of statistical comparisons (r-tests), of mean values for food and water intake (g/kg/day), excreta moisture (%), food metabolizability (%), and body weight schanges (%A BW/day) between cecectomized (C), and intact (I) sham-operated Great-horned owls for periods before and after cecectomy
Comparisons (1) Pre-op-C Pre-op-I (2) Post-op-C, 8-15 days Post-op-I, 8-15 days (3) Post-op-C, 21-25 days Post-op-I, 21-25 days (4) Post-op-C, 101-109 days Post-op-I, 101-109 days (5) Pre-op-C Post-op-C. 8-15 days (6) Pre-op-C Post-op-C, 21-25 days (7) Pre-op-C (8) (9) (10) (11) (12)
Post-op_C, 101-109 days Post-op-C, 8-15 days Post-op-C, 2 t-25 days Post-o& 8-l 5 days Post-op-C, 10f-109 days Post-op-C. 21-25 days Post-op-C. 101-109 days Pre-op-I Post-op-I, 8- 15days Pre-op-I Post-op-I, 21-25 days
(13) Pre-op-I Post-op-I, (14) Post-op-I, Post-op-I, (15) Post-op-I,
101-109 days 8-l 5 days 21-25 days 8-15 days POSt-OQ-I. 101-109 days (16) Post-op-I, 2 1-25 days POSt-OQ-I, 101-109 days
Food intake
Food metab. Body wt changes
Water intake
Excreta moist.
0.01*
0.01
-
-
0.01
0.01
-
-
-
-
-
0.05
NA**
-
0.05
0.01
-
-
0.01
-. -
0.01
0.01
-
-
-
NA
-
-
-
-
-
NA
-
-
0.01
-
NA
-
-
0.05
0.01
0.01
-
-
0.05
-
0.01
-
-
NA
-
-
-
-
-
NA
-
-
NA
-
0.05
-
-
-
* Values presented indicate level of significance of the statistical comparison. ** Data not available; see text.
mized owls was during days 8-15 post-op. (Table 1); thereafter water intake declined to near pre-op. levels. This may indicate that compensation for the initial loss of water absorption capability following removal of the ceca had occurred by about day 21. This compensation could have occurred either at the renal tubular level or within the colon and cloaca. Measurements of mean excreta moisture do not clearly confirm the above indication of a decrease in water absorption capability following cecectomy. While excreta moisture was higher in cecectomized owls than in intact ones, this was true for both the pre-op. and post-op. periods (Table 1). Also, while excreta moisture was higher post-op. than pre-op., this was true for both the cecectomized and shamoperated owls. Although water balance may have been altered after cecectomy. a significant decrease in food metabolizability or increase in food intake following loss of the ceca was not detected. Therefore, evidence of a significant cecal digestive function was not obtained by this study. Additionally, since no significant change in body weight was observed postoperatively and the owls still remain healthy (about 190 days post-op. thus far) ceca apparently do not account for any absolutely vital bodily function in strigiforms.
Further work will be required to elucidate whatever accessory function they may perform. REFERENCES BEATIIEJ. & SHRIMPTON D. I-I. (1958) Surgical and chemical techniques for in uioo studies of the metabolism of the
intestinal microflora of domestic fowls. Q. J. exp. Pfiysiol. 43, 399407. DUKEG. E. (1977) Avian digestion. In Dares’ ~~ysj~~~g~of D~~es~~cAnimals (Edited by SWENSON M. J.), Ch. 25, pp. 313-320. Cornell University Press, Ithaca, NY. DUKE G. E. (1978) Raptor physiology. In Zoo and Wild Animal Medicine (Edited by FOWLERM. E.), Chap. 14,
pp. 225-23 I. Saunders, Philadelphia. DUKEG. E., JEGERSA. A., LOFFG. & EVANSON 0. A. (1975) Gastric digestion in some raptors. Comp. Biochem. Physiol. SOA, 649-656. GASAWAYW. C. (1976) Cellulose digestion and metabolism by captive rock ptarmigun. Comp. Biochem. Physiol. 54. 179-l 82. HANSSENI. (1979) A comparison of the microbiological conditions in the small intestine and ceca of wild and captive willow grouse (Lagopus lagopus Iagopus). Acta. vet. stand. 20, 365-371. D. L. (1973) Cellulose digestion in Ruffed grouse. Chukar partridge, and Bobwhite quail. J. wi~d~.Mgmt. 37, 114-121.
INMAN
210
G. E. Durtr er trl.
McNns J. M. (1973) The av,an caeca: A rev,ew. World pwlr. .%I. J. 29. 3 I-263. Moss R. & PARKINSON J. A. (1972) The dlgestlon of heather (C~~lluw ru/qarr.s) by Red grouse Luyopu.~ /uyopu.s SCOrims) Br. .I. ,Yurr. 27. X5-298. NAIK D. R. & DOMINIC C. J. (1969) Intestinal crca of owls. Proc. 55fli I,ldia/l Ser. Coqgr. 196X. Part 111. p. 572. ST~.VIh;s C. E. (1977) Comparative physiology of the digestlvc system. In D~thu.\‘P/~?sfolo(/i, 01 Dovrrct~c iluifwi/.s (Edited by SWLNSOK M. J.). Chap. IX. pp. 216 732. Cornell Unlversitv Press. Ithaca. NY
Srt RKI~ P. D. (1976) .~I.ILIIIPhv.\,&q~ 3rd edn. SprmgcrVerlae. NY. THORNBLRN C. C. & WILL~OX J. S. (1965) The coca 01 the domestic fowl and dlgestlon of the crude fiber cornpie\. I Digestibility trials wth normal and carccctomlrcd birds. Br. pcult. Ser. 6. 23 ? I. ZISU ILER J. & FiZRNt R D. S (19721 Dlgcst~on and the dige\tiw system In .4rxr~ B~~~/crc/\~ (Edited by FAKWR D S. & Knc; J. R.), Vol II. (‘hap 6. pp 343-430 4cadern~c PreTs. Neti York.
2 weeks at which time 2 birds were eliminated from the
INTRODUCFIDN
Cecal function has been somewhat well studied in galliforms (e.g. Beattie & Shrimpton,
1958; Thornburn
&
Wilcox, 1965; Moss & Parkinson, 1972; Inman, 1973; Gasaway, 1976; Hanssen, 1979). As in mammals, bacterial degradation of dietary fiber is believed to be the
experiment because of failure to eat well and to adjust to the cages and frequent handling. At this time 4 owls were randomly selected for cecectomy and three for sham operations. Daily determinations of weight of food and water ingested, weight of excreta and pellet wastes, and body weights were begun. The experiment lasted for 119 days as rollows:
days - 10 to - I-pre-operative ;a;
(pre-op.) period
of surgery days I to 25 and 101 to lO9-post
primary cecal activity (Ziswiler & Farner, 1972; Duke, 1977; Stevens, 1977). Water absorption, including urinary water reabsorption, also appears to be a major function of avian ceca (Duke, 1977; McNab, 1973; Sturkie, 1976). We have not found reports of studies on cecal function in carnivorous birds despite the existence of ceca in several carnivorous orders (Ziswiler & Farner, 1972). The ceca of owls have been examined histologically (Naik & Dominic, 1969) and they are described as highly glandular. The presence of ceca may not be related to dietary habits in carnivores, since although owls and hawks generally eat similar diets, owls have ceca while hawks do not (Duke, 1978). It is thus difficult to hypothesize as to the likely function of ceca in owls. Our objectives were, therefore, to initiate investigations of cecal function in owls through a study of food metabolizability and water balance .in intact (sham operated) and ceeectomized great-horned owls Bubo virginianus). The studies were part of our continuing effort to gain new knowledge on gastrointestinal function in raptors to aid in their management and conservation. MATERIALS AND METHODS
Nine permanently crippled but otherwise healthy adult great-horned owls (B&o ui~gj~j~~us) were used. They were held in individual cages (46 x 46 x 61 cm) in environmentally controlled rooms in which temperature was maintained between 2l-23°C. relative humidity was kept between 40 and 50% and the photoperiod was automatically timed to provide 14 hr of light from 0700 to 2100 hr. The owls were allowed to acclimate to these conditions for 237
operative (post-op.) period. Data For days 1-7 indicated that recovery from surgery was not complete, consequently these data were not used. Also, daily handling appeared to cause increased nervousness in the owls resulting in declines in food intake and body weight so, body weights and weights of ingesta and waste were not determined for days lb20 to allow the owls to recover. These weights were determined during days 101-109 to see if measurements made during the first 25 days after cecectomy might change by 101-109 days post-op. One of the four cecectomized owls became ill, lost weight and died on day 85. Necropsy revealed an apparent atonicity at the ileoceococolic junction and an accumulation of ingesta orad to the junction. Standard surgical procedures were followed during the cecectomies. A laparotomy was performed and the viscera manipulated in the sham procedure. A preanesthetic of Ketamine-HCI (Ketaset, Bristol Veterinary Products, Syracuse, N.Y.) (lOmg/kg) and Xylazine (Rompun, Cutter Labs. Inc., Shawnee Kan.) (I mg/kg) was used to allow owls to be connected to a gas anesthesia machine. Methoxyflurane (Metofane. Pittman-Moore. Inc.. Wash. Crossinn. N.J.) was then used to maintain a surgical plane of anesthi: sia. The diet for the experiment was whole laboratory mice (Mm musculus) which were fresh or thawed from fresh frozen supplies. Meals of mice were weighed and presented to the owls at 1200 hr. Mice or parts of mice remaining at 1500 hr were collected and weighed. The room was checked once or twice during this period and food that had dropped through the mesh floor of the owl cages was returned to the owls. Excreta were collected in stainless steel trays under each owl cage. Immediately prior to feeding each day, the trays containing excreta were removed and replaced with clean trays. Pellets were also collected. Water pans for each owl and a “control” pan. used to evaluate evaporation. were also weighed and refilled as required at this time. Additionally the owls were weighed.
When the above procedures were completed and the owls had been given their daily ration of mice, excreta were taken to an adjacent laboratory and carefully scraped from each tray: the wet weight of excreta and pellets was determined. Since these were not fresh excreta (likewise for pellets), absolute water losses in wastes could not be ascertained. However, excreta were collected at the same time and in the same manner each da}. so relative water losses before and after surgery and in cecectomized vs sham-operated birds could be determined. Durmg the period 101-109 days post-op., humidity controls in the animal room were not operating properly. We were not aware of this problem until after completing the experiments and begmnmg calculation of moisture content in wastes and amount of evaporation occurring daily. By comparing evaporative losses from the “control” water pan during days 101-109 to losses m earlier periods we were able to adjust quantities of water Ingested during days 101 109 to values comparable to those during earlier periods. Since we had no “control” tray of cxcreta. mformation on the proportion of water in. and evaporation of water from. excreta during days I01 I09 could not be adjusted and was. therefore. not usable. Excreta and pellets were dried at 60 C for 24 hr and rewelghed to provide dry weights. The weight eaten also was converted to dry weight. Average dry matter in mice is of dry 37.X”,, (Duke et u/.. 1975). After determination weights of food and waste (excreta plus pellets), weight of water consumed. and dally individual body weights. a daily food metabolizability was determined as follows: metabolirability
coefficlcnt
= I ~
dry wt waste dry wt food
Percent body weight change per day was calculated. Mean values for food and water intake, food metabolizability, excreta moisture and daily body weight change were
determmed for the pre-op. period and lor day5 h I C.2 1 2:. and IOI--109 of the post-op. period. Mean value\ for each parameter (e.g.food Intake) were compared via a Student’5 f-test among and between the pre-op and post-op. periods RESLILTS AhD DISC‘LSSIOU
Food metabolizabiht) and body weight changes did not appear to be affected b) cecectomy (Tables i and 2). Food intake by cecectomized owls has me\plicably low during days 101 109 and. therefore. significantly lower than intake by these owls during daqs X-15 and 21L25; it uas also lo\\er than intake by intact owls during days IOL 109. This IOU mtakr resulted in significant weight loss during that period (Table 2) but. since this loss was recovered immediately after the experiment when owls were returned to their normal holding room. it is believed to be due IU the experimental conditions rathrr than to the cecectomy which occurred over IO0 days earlier. Food intake was lower immediately following surger! in both the cecectomized and the sham-operated owls. As a result intake increased in both cecectomized and sham-operated owls during days S25 after surgery. Thus, the surgery, not the absence of ceca. seems to account for this increase. Food intake, therefore. also did not appear to be intluenced by cecectom!. Although average daily water Intake seemed rathet variable in the intact owls. intake in the cecectomired birds did appear to increase following cecectomv and to remain higher in cecectomized owls than in intact ones (Table 1). If the ceco are involved in crater absorption, this change is readill explained. The greatest daily water intake within the group of cececto-
Table I. Mean food and water intake (g/kg/day). excrela moisture (Y,,). food metabolizability (“J. and body weight changes (“,,A BW:day) in intact (I) sham-operated and cecectomized (C) Great-horned owls Period* Condition of owl
Parameter Water
intake
C
I Food
intake
c
I Food
metabol.
C I
Excreta
moist.
c I
Body wt change
C I
Pre-op. 16.9 (13.1)** 24.0 (22.4) 16.6 (7.21) 16.7 (5.90) 58.2 (6.70) 59.5 (6.60) 59.8 (X.75) 52.7 (10.4) -0.20 (0.96) - 0.09 (0.95)
* Pre-op. = preoperative period; Post-op (day of surgery) to day I09 post-surgery. ** Numbers in parentheses are SD. t Data not available; see text.
day x -15 27.2 (16.4) 7.39 (10.9) 20. t (7.80) ‘1.3 (6.78) 61.2 (7.61) 59.8 (4.32) 70.0 (6.44) 63.X (6.X6) +0.32 (1.92) + 0.27 (0.98) = postoperative
Post-op day 21-25 I X.6 (12.4) 12.5 (10.7) 20.0 (4.33) 2 I .9 (5.83) 61.1 (4.01) 61.X (3.43) 67.4 (12.5) 62. I (7.53) - 0.09 (0.80) -0.20 (1.13)
day 101-109 17.2 (I 1.4) 8.6s (10.0) 13.4 (6.35) 19.0 (5.53) 60.2 (5 Xl 60.9 (5.X21 NAt NAt NAt NAt -0.38 (0.32) + 0. I 5 (0.14)
period including
day 0
239
Food metabolizability and water balance in great-horned owls
Table 2. Results of statistical comparisons (r-tests), of mean values for food and water intake (g/kg/day), excreta moisture (%), food metabolizability (%), and body weight schanges (%A BW/day) between cecectomized (C), and intact (I) sham-operated Great-horned owls for periods before and after cecectomy
Comparisons (1) Pre-op-C Pre-op-I (2) Post-op-C, 8-15 days Post-op-I, 8-15 days (3) Post-op-C, 21-25 days Post-op-I, 21-25 days (4) Post-op-C, 101-109 days Post-op-I, 101-109 days (5) Pre-op-C Post-op-C. 8-15 days (6) Pre-op-C Post-op-C, 21-25 days (7) Pre-op-C (8) (9) (10) (11) (12)
Post-op_C, 101-109 days Post-op-C, 8-15 days Post-op-C, 2 t-25 days Post-o& 8-l 5 days Post-op-C, 10f-109 days Post-op-C. 21-25 days Post-op-C. 101-109 days Pre-op-I Post-op-I, 8- 15days Pre-op-I Post-op-I, 21-25 days
(13) Pre-op-I Post-op-I, (14) Post-op-I, Post-op-I, (15) Post-op-I,
101-109 days 8-l 5 days 21-25 days 8-15 days POSt-OQ-I. 101-109 days (16) Post-op-I, 2 1-25 days POSt-OQ-I, 101-109 days
Food intake
Food metab. Body wt changes
Water intake
Excreta moist.
0.01*
0.01
-
-
0.01
0.01
-
-
-
-
-
0.05
NA**
-
0.05
0.01
-
-
0.01
-. -
0.01
0.01
-
-
-
NA
-
-
-
-
-
NA
-
-
0.01
-
NA
-
-
0.05
0.01
0.01
-
-
0.05
-
0.01
-
-
NA
-
-
-
-
-
NA
-
-
NA
-
0.05
-
-
-
* Values presented indicate level of significance of the statistical comparison. ** Data not available; see text.
mized owls was during days 8-15 post-op. (Table 1); thereafter water intake declined to near pre-op. levels. This may indicate that compensation for the initial loss of water absorption capability following removal of the ceca had occurred by about day 21. This compensation could have occurred either at the renal tubular level or within the colon and cloaca. Measurements of mean excreta moisture do not clearly confirm the above indication of a decrease in water absorption capability following cecectomy. While excreta moisture was higher in cecectomized owls than in intact ones, this was true for both the pre-op. and post-op. periods (Table 1). Also, while excreta moisture was higher post-op. than pre-op., this was true for both the cecectomized and shamoperated owls. Although water balance may have been altered after cecectomy. a significant decrease in food metabolizability or increase in food intake following loss of the ceca was not detected. Therefore, evidence of a significant cecal digestive function was not obtained by this study. Additionally, since no significant change in body weight was observed postoperatively and the owls still remain healthy (about 190 days post-op. thus far) ceca apparently do not account for any absolutely vital bodily function in strigiforms.
Further work will be required to elucidate whatever accessory function they may perform. REFERENCES BEATIIEJ. & SHRIMPTON D. I-I. (1958) Surgical and chemical techniques for in uioo studies of the metabolism of the
intestinal microflora of domestic fowls. Q. J. exp. Pfiysiol. 43, 399407. DUKEG. E. (1977) Avian digestion. In Dares’ ~~ysj~~~g~of D~~es~~cAnimals (Edited by SWENSON M. J.), Ch. 25, pp. 313-320. Cornell University Press, Ithaca, NY. DUKE G. E. (1978) Raptor physiology. In Zoo and Wild Animal Medicine (Edited by FOWLERM. E.), Chap. 14,
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