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A simulated insect diet as a water source for quail: effects on body mass and reproduction
Camp. Biochem. Physiol. Vol. I I IA, No. 2, pp. 299-302, 1995 Elsevier Saence Ltd Printed in Great Britain 0300-9629195 $9.50 + 0.00
Pergamon 0300-%29(94)00207-X
A simulated insect diet as a water source for quail: effects on body mass and reproduction William M. Giuliano ,* R. Scott Lutz,7 and Reynaldo Patifiol *Texas Cooperative Fish and Wildlife Research Unit, Department of Range and Wildlife Management, Texas Tech University, Lubbock, TX 79409, U.S.A.; TDepartment of Range and Wildlife Management, Texas Tech University, Lubbock, TX 79409, U.S.A.; and $National Biological Survey, Texas Cooperative Fish and Wildlife Research Unit. Texas Tech University, Lubbock, TX 79409, U.S.A. Compared with control birds receiving ad libitum free-water, the total water intake of male and female northern bobwhite declined when only mealworms were available as a source of water. Male northern bobwhite sustained tissue mass and reproductive function with mealworms as their only source of water. Female northern bobwhite could not sustain body, ovary, and oviduct mass, and rate of egg production with mealworms as their only source of water. We suggest that, without free-water, breeding females require a diet with a water:dry matter ratio of greater than 1: 1.29 ( > 44% water). Key words: Northern Diet.
bobwhite;
Quail;
Comp. Biochem. Physiol. 11 IA, 299-302,
Water;
Reproduction;
Body mass;
Mealworms;
Insects;
1995.
Introduction Insects are an important food of many avian species (Calvert et al., 1969; Hurst, 1972; Krapu and Swanson, 1975; Goldstein and Nagy, 1985; Guthery, 1986; Reinecke and Krapu, 1986). Growing and breeding birds require the high protein and energy content of insects to meet their nutritional needs. However, the importance of insects as a potential water source for birds living in arid regions or during droughts is unclear (Vorhies, 1928; Stoddard, 1931; Goldstein and Nagy, 1985). Hurst (1972) Guthery (1986) and Leif (1987) have discussed the importance of insects as a high protein and energy food to northern bobwhite (Colinus virginianus), and several authors (Vorhies, 1928; Stoddard, 193 1;
Goldstein and Nagy, 1985) have recognized insects as a water source for quail. Several researchers have suggested that quail do not need sources of free-water, because they fulfil their water requirements by consuming succulent vegetataion and insects (Vorhies, 1928; Stoddard. 1931; McNabb, 1969; Goldstein and Nagy, 1985; Guthery, 1986; Guthery and Koerth, 1992). Further, Guthery and Koerth (1992) concluded that, even during drought years, northern bobwhite can obtain enough water to meet their needs by consuming available plant forage. However, although northern bobwhite could sustain mass with succulent vegetation as their only water source in the laboratory, their reproductive activity declined (Guthery and Koerth, 1992). The objective of our study was to determine if mealworms could provide an adequate source of water for northern bobwhite. Specifically, we determined if northern bobwhite could sustain mass and reproductive function with mealworms as their sole water source.
fo: William M. Giuliano, Texas Cooperative Fish and Wildlife Research Unit, Dept. of Range and Wildlife Management, Texas Tech University, Lubbock, TX 79409, U.S.A. Tel. 806-742-2806. Received 25 June 1994; revised 18 October 1994; accepted 26 October 1994. Correspondence
299
300
W. M. Giuliano
Materials and Methods We used captive-reared adult northern bobwhite (Marks Gamebird Farm, Eden, TX) for our experiments because they respond similarly to their wild counterparts during water deprivation (Koerth and Guthery, 1991). Birds were housed individualy in 25 x 25 x 55 cm cages in an outdoor experimental facility that provided protection from wind and rain, while exposing them to ambient temperatures and photoperiod. Birds were legbanded and acclimated to cages and foods (gamebird feed or mealworms (Tenebrio spp.) as appropriate) for 2 weeks before experimentation. Experiments began 18 April and proceeded through 16 May 1992. We weighed and randomly assigned seven male and 14 female quail to each of a control and two treatment groups. Control birds were given water (referred to as free-water) and gamebird feed (90% dry, 20% protein; Gamebreeder, Purina, Inc.) ad libitum; birds in treatment I (Tl) were given free-water, feed, and mealworms ad Iibitum; and birds in treatment 2 (T2) were given feed and mealworms ad libitum. We used mealworms to simulate an insect diet because of their availability and lack of mobility. Food, free-water, and mealworm consumption were measured daily during the study, and throughout the experiment, we recorded timing and rate of egg production. Free-water consumption was corrected for evaporative loss. Evaporative loss was estimated daily by averaging the water lost from five unused quail watering devices at random points within the experimental facility. Birds were weighed every 2 weeks. We decapitated birds on 16 May, and removed and weighed gonads, gizzards, and gastrointestinal tracts. Water content of mealworms (n = 30) was determined by weighing, drying to equilibrium (3 days, 60°C) and then reweighing. Factorial (sex*treatment) ANOVA, followed by Tukey’s multiple comparisons
et al.
(Wilkinson, 1990) was performed to determine differences in feed, total dry matter, mealworm, free-water, and total water consumption (i.e. water from feed and mealworms, and freewater), tissue mass, and egg production and mass among treatments and sexes. We used a log-linear model to test differences in the number of hens laying among treatments (Wilkinson, 1990).
Results Three female quail in T2 did not consume any mealworms, and died during the first week of the experiment. We excluded these birds from our analyses. No other quail died during the study. Free-water consumption was lower in Tl males (P = 0.047) than in control birds, but not in females (P = 0.358; Table 1). Treatment did not affect the feed intake of males (P = 0.435) or females (P = 0.407; Table 1). Mealworms consisted of 66.3 + 1.4% water (mean + SE). Males (P = 0.001) and females (P < 0.001) consumed more mealworms in T2 than in Tl (Table 1). Total water intake was lower in both male (P < 0.001) and female (P < 0.001) quail in T2 compared with control birds (Table 1). In contrast, total dry matter consumed by T2 birds was higher for both males (P = 0.002) and females (P = 0.046; Table 1). Male body mass, 4 weeks after the onset of treatment, was not affected (P = 0.761) by treatment. However, females in T2 had a lower body mass (P = 0.009) than control birds and TI birds (Table 2). Gizzard mass differed among treatments in females (P = 0.042), but not males (P = 0.313). Gastrointestinal tract mass was similar among treatments in females (P = 0.816) and males (P = 0.595) as were left (P = 0.680) and right (P = 0.958) testis and egg (P = 0.216) mass. Ovary (P =O.OlO) and oviduct (P =0.017)
Table I. Feed, mealworm, free water, total water, and total dry matter consumption of northern bobwhite given gamebird feed and water (control); gamebird feed, mealworms, and water (treatment 1); or gamebird feed and mealworms (treatment 2) Control Variable
Sex
Feed (g/bird/day)
M F M F M F M F M F
Mealworm
(g/bird/day)
Free water (ml/bird/day) Total
water (ml/bird/day)
Total dry matter *Means
within
(g/bird/day) a row followed
B
Treatment SE
19.93A* 22.62A
1.10 1.11
33.63 41.33A 35.08A 44.03 I6.19A 20.36A
1.32 1.84 1.51 1.99 0.99 1.00
by the same letter are similar
4 16.69A I7.65A 15.96 19.17 27.20 38.1 IA 39.45A 53.09 20.40A 22.43AB (P > 0.05)
I
Treatment
2
SE
x
SE
3.63 3.49 2.39 0.98 2.58 3.10 1.19 2.81 3.43 2.17
22.06A 21.29A 33.32 30.64
3.35 3.26 3.49 2.30
24.30 22.44 31.08 29.49B
2.09
1.59 2.31 3.12
Insects
as a water
source
for quail
Table 2. Tissue mass, 4 weeks after the onset of treatment, and reproductive performance of northern bobwhite given gamebird feed and water (control); gamebird feed, mealworms, and water (treatment 1); or gamebird feed and mealworms (treatment 2) Treatment
Control Variable
Gizzard
M F M F M F
(g)
Gastrointestinal
tract (g)
Egg mass (g) Rate of egg production within
199.43A* 234.OOA 4.6lA 5.36AB 3.66A 4.70A
1.26A I .02A
Left testis (g) Right testis (g) Ovary (g) Oviduct (g)
*Means
SE
v
Sex
Body mass (g)
(eggs/hen/day)
a row followed
6.18A 13.32A 8.79A 0.44A
by the same letter are similar
mass, and rate of egg production (P = 0.051) were lower in T2 birds compared with control birds (Table 2). The number of hens laying (P = 0.273) and the date that egg laying was initiated (P = 0.192) did not differ among treatments.
Discussion and Conclusions Northern bobwhite given mealworms in addition to feed and free-water reduced their free-water intake without adverse affects on tissue mass and reproductive function. However, providing mealworms as the only source of water had effects that differed between the sexes. Male body, gizzard, gastrointestinal, and testes mass were unaffected by water source (i.e. treatment). All males had testes weighing more than 300 mg. indicating that they probably had normal numbers of functional sperm (Cain and Lien, 1985). Therefore, mealworms seemed to fulfil the water requirements of reproductive males. Female northern bobwhite receiving mealworms as their only source of water lost body, ovary, and oviduct mass, and had a lower rate of egg production than birds receiving freewater. Thus, mealworms alone, without freewater, could not fulfil the needs of reproductive female quail. All quail receiving no free-water (T2) increased their use of mealworms and their total dry matter consumption above birds in other treatments. It is possible that these birds were trying to compensate for their lack of free-water by increasing consumption of water from mealworms. However, total water intake of T2 birds remained below levels of control birds, possibly because mealworm consumption in T2 birds was limited by the rate of digestion of mealworm dry matter (Levey and Karasov, 1989;
4.10 5.28 0.17 0.22 0.24 0.28 0.12 0.13 0.39 0.54 0.16 0.07
4 205.57A 237.50A 4.72A 6.06A 3.94A 4.88A I .43A I .07A 6.74A 12.16A 8.74A 0.44A
I SE 5.35 6.58 0.31 0.24 0.24 0.22 0.12 0.13 0.61 I .05 0.18 0.06
Treatment 4 204.43A 209.09 4.18A 5.20B 3.64A 4.62A I .28A I .04A 2.62 4.94 8.08A 0.1 I
2 SE 8.38 7.50 0.27 0.23 0.22 0.37 0.19 0.13 0.57 I.29 0.14 0.04
(P > 0.05).
Karasov, 1990). Therefore, we suggest that mealworms have a suboptimum ratio of water to dry matter, and cannot fulfil all the water requirements of breeding female quail. The ratios of water: dry matter consumed were similar between the sexes within each treatment (P > 0.05). Control, Tl. and T2 birds had water:dry matter ratios in their diets of I :0.46 (68% water). 1 :0.47 (68% water), and 1 : 1.29 (44% water) ml H,O/g dry matter. respectively. We suggest that female quail require a water: dry matter consumption ratio greater than T2 birds (>44% water). Female T2 birds consumed 29.49 g/bird/day of total dry matter. Had these birds eaten only mealworms and no feed, they could have ingested 57.24g/bird/day of water, which would have been greater than the total water intake of control birds. However, T2 quail chose to consume some feed in addition to mealworms, apparently trading water for other nutritional needs. Consumption of succulent vegetation such as lettuce (95.5% water; Guthery and Koerth, 1992) and/or insects (average insect: 7&75*X1 water; Bell, 1990) with a higher water content could provide quail with enough moisture to meet their needs. However, Guthery and Koerth (1992) reported declines in female northern bobwhite reproductive activity even when the total water intake of birds receiving only lettuce was greater than the total water intake of birds receiving free-water. We suggest that Koerth and Guthery’s (1992) observation of reduced reproductive activity could have been the result of inadequate nutrition (lettuce) and not water. The different diets among treatments in our study provided different amounts of metabolic water (McNabb, 1969; Dawson, 1974). Insect diets are typically higher in protein and fat and produce more metabolic water than the
302
W. M. Giuliano
carbohydrates of plants. Thus, our estimates of total utilizable water for birds in the treatment groups were probably underestimated, relative to control birds. A diverse diet of succulent vegetation and insects found in wild birds may satisfy nutritional requirements and provide the correct water:dry matter ratio for breeding quail. This may explain how wild birds can meet their water and nutritional requirements in the absence of free-water (McNabb, 1969; Guthery, 1986; Guthery and Koerth, 1992). Acknowledgements-Our study was supported by the San Antonio Livestock Show, the Noxious Brush and Weed Control Program, and the Texas Cooperative Fish and Wildlife Research Unit, Department of Range and Wildlife Management, Texas Tech University. We thank C. Benevides and N. Mancha for assistance with data collection, and D. Wester for statistical advice. This study was approved by the Texas Tech University Animal Care and Use Committee (ACUC #92250). We thank C. Davis, S. Demarais, and E. Laca for reviewing earlier drafts of the manuscript. This is Technical Report #T-9-681 of the College of Agricultural Sciences and Natural Resources, Texas Tech University, Lubbock. The Texas Cooperative Fish and Wildlife Research Unit is jointly supported by the National Biological Survey, Texas Tech University, Texas Parks and Wildlife, and The Wildlife Management Institute.
References Bell G. P. (1990) Birds and Mammals on an insect diet: a primer on diet composition analysis in relation to ecoloaiial energetic% Studies Avian B&l. 13, 416-422. Cain R. J. and Lien R. J. (1985) A model for drought inhibition of bobwhite quail (Cd/&us virginianus) reproductive systems. Comp. Biochem. Physiol. 82, 925-930. Calvert C. C., Martin R. D. and Morgan N. 0. (1969)
et al.
House By pupae as food for poultry. J. Econ. Entomol. 62. 938-939. Dawson W. R. (1974) Physiological and behavioral adiustments of birds to heat and aribity. Proc. 16th Inl. Or>i/h. Congr. (Edited bv Froth H. J. and Calabv J. H.1. pp. 455467. Australian Acad. Sci. Canberra Ciiy. A.C.T: Goldstein D. L. and Nagy K. A. (1985) Resource utilization by desert quail: time and energy, food and water. Ecology 66, 378-387. Guthery F. S. (1986) BeeJ Brush and Bobwhiles: Quail Management in Cattle Counrrv. Ceasar Klebere Wildlife Research Inst, Texas A&I Univ., Kingsville. TX. 182 pp. Guthery F. S. and Koerth N. E. (19921 Substandard water . intake and inhibition of bobwhite reproduction during drought. J. Wildl. Manage. 56, 76&768. Hurst G. A. (1972) Insects and bobwhite auail brood habitat management. Natn. Quail Symp. 1, 65-81. Karasov W. H. (1990) Dieestion in birds: chemical and physiological dkter&na& and ecological implications. Stud. Avian Biol. 13, 391415. Koerth N. E. and Guthery F. S. (1991) Water restriction effects on northern bobwhite reproduction. J. Wildl. Manage. 55, 132-I 37. Krapu G. L. and Swanson G. A. (1975) Some nutritional aspects of reproduction in prairie nesting pintails. J. Wild/. Manage. 39, 156-162. Leif P. (1987) Bobwhite and scaled quail responses to burning of redberry juniper-dominated rangelands. M.S. Thesis, Texas Tech Univ., Lubbock. 84 pp. Levey D. J. and Karasov W. H. (1989) Digestive responses of temperate birds switched to fruit or insect diets. Ask 106, 675-686. McNabb F. M. A. (1969) A comparative study of water balance in three species of quail. Camp. Biochem. Physiol. 28, 1045-1058. Reinecke K. T. and Krapu G. L. (1986) Feeding ecology of sandhill cranes during spring migration in Nebraska. J. Wildl. Manage. 50, 71-79. Stoddard H. L. (1931) The Bobwhite Quail: Its Habits. Preservation and Increase. Charles Scribner’s Sons, New York. 559 pp. Vorhies C. T. (1928) Do southwestern quail require water? Am. Nat. 62, 44-52. Wilkinson L. (1990) SYSTAT: The System for Statistics. Evanston, IL. 677 pp.
Pergamon 0300-%29(94)00207-X
A simulated insect diet as a water source for quail: effects on body mass and reproduction William M. Giuliano ,* R. Scott Lutz,7 and Reynaldo Patifiol *Texas Cooperative Fish and Wildlife Research Unit, Department of Range and Wildlife Management, Texas Tech University, Lubbock, TX 79409, U.S.A.; TDepartment of Range and Wildlife Management, Texas Tech University, Lubbock, TX 79409, U.S.A.; and $National Biological Survey, Texas Cooperative Fish and Wildlife Research Unit. Texas Tech University, Lubbock, TX 79409, U.S.A. Compared with control birds receiving ad libitum free-water, the total water intake of male and female northern bobwhite declined when only mealworms were available as a source of water. Male northern bobwhite sustained tissue mass and reproductive function with mealworms as their only source of water. Female northern bobwhite could not sustain body, ovary, and oviduct mass, and rate of egg production with mealworms as their only source of water. We suggest that, without free-water, breeding females require a diet with a water:dry matter ratio of greater than 1: 1.29 ( > 44% water). Key words: Northern Diet.
bobwhite;
Quail;
Comp. Biochem. Physiol. 11 IA, 299-302,
Water;
Reproduction;
Body mass;
Mealworms;
Insects;
1995.
Introduction Insects are an important food of many avian species (Calvert et al., 1969; Hurst, 1972; Krapu and Swanson, 1975; Goldstein and Nagy, 1985; Guthery, 1986; Reinecke and Krapu, 1986). Growing and breeding birds require the high protein and energy content of insects to meet their nutritional needs. However, the importance of insects as a potential water source for birds living in arid regions or during droughts is unclear (Vorhies, 1928; Stoddard, 1931; Goldstein and Nagy, 1985). Hurst (1972) Guthery (1986) and Leif (1987) have discussed the importance of insects as a high protein and energy food to northern bobwhite (Colinus virginianus), and several authors (Vorhies, 1928; Stoddard, 193 1;
Goldstein and Nagy, 1985) have recognized insects as a water source for quail. Several researchers have suggested that quail do not need sources of free-water, because they fulfil their water requirements by consuming succulent vegetataion and insects (Vorhies, 1928; Stoddard. 1931; McNabb, 1969; Goldstein and Nagy, 1985; Guthery, 1986; Guthery and Koerth, 1992). Further, Guthery and Koerth (1992) concluded that, even during drought years, northern bobwhite can obtain enough water to meet their needs by consuming available plant forage. However, although northern bobwhite could sustain mass with succulent vegetation as their only water source in the laboratory, their reproductive activity declined (Guthery and Koerth, 1992). The objective of our study was to determine if mealworms could provide an adequate source of water for northern bobwhite. Specifically, we determined if northern bobwhite could sustain mass and reproductive function with mealworms as their sole water source.
fo: William M. Giuliano, Texas Cooperative Fish and Wildlife Research Unit, Dept. of Range and Wildlife Management, Texas Tech University, Lubbock, TX 79409, U.S.A. Tel. 806-742-2806. Received 25 June 1994; revised 18 October 1994; accepted 26 October 1994. Correspondence
299
300
W. M. Giuliano
Materials and Methods We used captive-reared adult northern bobwhite (Marks Gamebird Farm, Eden, TX) for our experiments because they respond similarly to their wild counterparts during water deprivation (Koerth and Guthery, 1991). Birds were housed individualy in 25 x 25 x 55 cm cages in an outdoor experimental facility that provided protection from wind and rain, while exposing them to ambient temperatures and photoperiod. Birds were legbanded and acclimated to cages and foods (gamebird feed or mealworms (Tenebrio spp.) as appropriate) for 2 weeks before experimentation. Experiments began 18 April and proceeded through 16 May 1992. We weighed and randomly assigned seven male and 14 female quail to each of a control and two treatment groups. Control birds were given water (referred to as free-water) and gamebird feed (90% dry, 20% protein; Gamebreeder, Purina, Inc.) ad libitum; birds in treatment I (Tl) were given free-water, feed, and mealworms ad Iibitum; and birds in treatment 2 (T2) were given feed and mealworms ad libitum. We used mealworms to simulate an insect diet because of their availability and lack of mobility. Food, free-water, and mealworm consumption were measured daily during the study, and throughout the experiment, we recorded timing and rate of egg production. Free-water consumption was corrected for evaporative loss. Evaporative loss was estimated daily by averaging the water lost from five unused quail watering devices at random points within the experimental facility. Birds were weighed every 2 weeks. We decapitated birds on 16 May, and removed and weighed gonads, gizzards, and gastrointestinal tracts. Water content of mealworms (n = 30) was determined by weighing, drying to equilibrium (3 days, 60°C) and then reweighing. Factorial (sex*treatment) ANOVA, followed by Tukey’s multiple comparisons
et al.
(Wilkinson, 1990) was performed to determine differences in feed, total dry matter, mealworm, free-water, and total water consumption (i.e. water from feed and mealworms, and freewater), tissue mass, and egg production and mass among treatments and sexes. We used a log-linear model to test differences in the number of hens laying among treatments (Wilkinson, 1990).
Results Three female quail in T2 did not consume any mealworms, and died during the first week of the experiment. We excluded these birds from our analyses. No other quail died during the study. Free-water consumption was lower in Tl males (P = 0.047) than in control birds, but not in females (P = 0.358; Table 1). Treatment did not affect the feed intake of males (P = 0.435) or females (P = 0.407; Table 1). Mealworms consisted of 66.3 + 1.4% water (mean + SE). Males (P = 0.001) and females (P < 0.001) consumed more mealworms in T2 than in Tl (Table 1). Total water intake was lower in both male (P < 0.001) and female (P < 0.001) quail in T2 compared with control birds (Table 1). In contrast, total dry matter consumed by T2 birds was higher for both males (P = 0.002) and females (P = 0.046; Table 1). Male body mass, 4 weeks after the onset of treatment, was not affected (P = 0.761) by treatment. However, females in T2 had a lower body mass (P = 0.009) than control birds and TI birds (Table 2). Gizzard mass differed among treatments in females (P = 0.042), but not males (P = 0.313). Gastrointestinal tract mass was similar among treatments in females (P = 0.816) and males (P = 0.595) as were left (P = 0.680) and right (P = 0.958) testis and egg (P = 0.216) mass. Ovary (P =O.OlO) and oviduct (P =0.017)
Table I. Feed, mealworm, free water, total water, and total dry matter consumption of northern bobwhite given gamebird feed and water (control); gamebird feed, mealworms, and water (treatment 1); or gamebird feed and mealworms (treatment 2) Control Variable
Sex
Feed (g/bird/day)
M F M F M F M F M F
Mealworm
(g/bird/day)
Free water (ml/bird/day) Total
water (ml/bird/day)
Total dry matter *Means
within
(g/bird/day) a row followed
B
Treatment SE
19.93A* 22.62A
1.10 1.11
33.63 41.33A 35.08A 44.03 I6.19A 20.36A
1.32 1.84 1.51 1.99 0.99 1.00
by the same letter are similar
4 16.69A I7.65A 15.96 19.17 27.20 38.1 IA 39.45A 53.09 20.40A 22.43AB (P > 0.05)
I
Treatment
2
SE
x
SE
3.63 3.49 2.39 0.98 2.58 3.10 1.19 2.81 3.43 2.17
22.06A 21.29A 33.32 30.64
3.35 3.26 3.49 2.30
24.30 22.44 31.08 29.49B
2.09
1.59 2.31 3.12
Insects
as a water
source
for quail
Table 2. Tissue mass, 4 weeks after the onset of treatment, and reproductive performance of northern bobwhite given gamebird feed and water (control); gamebird feed, mealworms, and water (treatment 1); or gamebird feed and mealworms (treatment 2) Treatment
Control Variable
Gizzard
M F M F M F
(g)
Gastrointestinal
tract (g)
Egg mass (g) Rate of egg production within
199.43A* 234.OOA 4.6lA 5.36AB 3.66A 4.70A
1.26A I .02A
Left testis (g) Right testis (g) Ovary (g) Oviduct (g)
*Means
SE
v
Sex
Body mass (g)
(eggs/hen/day)
a row followed
6.18A 13.32A 8.79A 0.44A
by the same letter are similar
mass, and rate of egg production (P = 0.051) were lower in T2 birds compared with control birds (Table 2). The number of hens laying (P = 0.273) and the date that egg laying was initiated (P = 0.192) did not differ among treatments.
Discussion and Conclusions Northern bobwhite given mealworms in addition to feed and free-water reduced their free-water intake without adverse affects on tissue mass and reproductive function. However, providing mealworms as the only source of water had effects that differed between the sexes. Male body, gizzard, gastrointestinal, and testes mass were unaffected by water source (i.e. treatment). All males had testes weighing more than 300 mg. indicating that they probably had normal numbers of functional sperm (Cain and Lien, 1985). Therefore, mealworms seemed to fulfil the water requirements of reproductive males. Female northern bobwhite receiving mealworms as their only source of water lost body, ovary, and oviduct mass, and had a lower rate of egg production than birds receiving freewater. Thus, mealworms alone, without freewater, could not fulfil the needs of reproductive female quail. All quail receiving no free-water (T2) increased their use of mealworms and their total dry matter consumption above birds in other treatments. It is possible that these birds were trying to compensate for their lack of free-water by increasing consumption of water from mealworms. However, total water intake of T2 birds remained below levels of control birds, possibly because mealworm consumption in T2 birds was limited by the rate of digestion of mealworm dry matter (Levey and Karasov, 1989;
4.10 5.28 0.17 0.22 0.24 0.28 0.12 0.13 0.39 0.54 0.16 0.07
4 205.57A 237.50A 4.72A 6.06A 3.94A 4.88A I .43A I .07A 6.74A 12.16A 8.74A 0.44A
I SE 5.35 6.58 0.31 0.24 0.24 0.22 0.12 0.13 0.61 I .05 0.18 0.06
Treatment 4 204.43A 209.09 4.18A 5.20B 3.64A 4.62A I .28A I .04A 2.62 4.94 8.08A 0.1 I
2 SE 8.38 7.50 0.27 0.23 0.22 0.37 0.19 0.13 0.57 I.29 0.14 0.04
(P > 0.05).
Karasov, 1990). Therefore, we suggest that mealworms have a suboptimum ratio of water to dry matter, and cannot fulfil all the water requirements of breeding female quail. The ratios of water: dry matter consumed were similar between the sexes within each treatment (P > 0.05). Control, Tl. and T2 birds had water:dry matter ratios in their diets of I :0.46 (68% water). 1 :0.47 (68% water), and 1 : 1.29 (44% water) ml H,O/g dry matter. respectively. We suggest that female quail require a water: dry matter consumption ratio greater than T2 birds (>44% water). Female T2 birds consumed 29.49 g/bird/day of total dry matter. Had these birds eaten only mealworms and no feed, they could have ingested 57.24g/bird/day of water, which would have been greater than the total water intake of control birds. However, T2 quail chose to consume some feed in addition to mealworms, apparently trading water for other nutritional needs. Consumption of succulent vegetation such as lettuce (95.5% water; Guthery and Koerth, 1992) and/or insects (average insect: 7&75*X1 water; Bell, 1990) with a higher water content could provide quail with enough moisture to meet their needs. However, Guthery and Koerth (1992) reported declines in female northern bobwhite reproductive activity even when the total water intake of birds receiving only lettuce was greater than the total water intake of birds receiving free-water. We suggest that Koerth and Guthery’s (1992) observation of reduced reproductive activity could have been the result of inadequate nutrition (lettuce) and not water. The different diets among treatments in our study provided different amounts of metabolic water (McNabb, 1969; Dawson, 1974). Insect diets are typically higher in protein and fat and produce more metabolic water than the
302
W. M. Giuliano
carbohydrates of plants. Thus, our estimates of total utilizable water for birds in the treatment groups were probably underestimated, relative to control birds. A diverse diet of succulent vegetation and insects found in wild birds may satisfy nutritional requirements and provide the correct water:dry matter ratio for breeding quail. This may explain how wild birds can meet their water and nutritional requirements in the absence of free-water (McNabb, 1969; Guthery, 1986; Guthery and Koerth, 1992). Acknowledgements-Our study was supported by the San Antonio Livestock Show, the Noxious Brush and Weed Control Program, and the Texas Cooperative Fish and Wildlife Research Unit, Department of Range and Wildlife Management, Texas Tech University. We thank C. Benevides and N. Mancha for assistance with data collection, and D. Wester for statistical advice. This study was approved by the Texas Tech University Animal Care and Use Committee (ACUC #92250). We thank C. Davis, S. Demarais, and E. Laca for reviewing earlier drafts of the manuscript. This is Technical Report #T-9-681 of the College of Agricultural Sciences and Natural Resources, Texas Tech University, Lubbock. The Texas Cooperative Fish and Wildlife Research Unit is jointly supported by the National Biological Survey, Texas Tech University, Texas Parks and Wildlife, and The Wildlife Management Institute.
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