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Monogastric Research Centre, Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand and * Department of Physiology, Institute of Medical Biology, Odense University, DK-5000 Odense C., Denmark
3To whom correspondence should be addressed.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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KEY WORDS: • cats • milk intake • tritiated water • water turnover
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Milk intake of suckling young has been measured indirectly by
comparison of growth rates of suckling and formula-fed young
(Buss and Voss 1971
), and by weighing the young several
times a day over an extended period before and after suckling
(Mundt et al. 1981
, Pettigrew et al. 1985
). A more direct approach for measuring milk intake can be
obtained by the water isotope dilution
(WID)5
technique. This method uses an isotope of hydrogen (such as
2H or 3H) as a tracer to
estimate body water turnover; together with accurate information on the
composition of milk and body weight gain of the young, this allows
estimation of milk intake (Coward et al. 1982
,
Fjeld et al. 1988
, Pettigrew et al. 1987
). A major advantage of the WID technique over the
weigh-suckle-weigh (WSW) technique is that there is only minimal
disruption of the normal maternal-offspring relationship.
Furthermore, the WSW technique has been shown to underestimate milk
consumption by up to 12% in pigs (Pettigrew et al. 1985
), 15% in human infants (Butte et al. 1983
), and 30% or more in dogs (Oftedal 1984
)
and mice (Baverstock and Elhay 1981
).
Recently, Dobenecker et al. (1998)
used the WSW method
to estimate milk yield of queens nursing different sized litters over
the first 9 wk of lactation. These authors estimated the degree of
underestimation of the kitten’s milk intake to be ~20–25%, based
on the difference in growth rates during the measurement period and
when suckling normally. Jayawickrama et al. (1998)
used
the WSW technique and reported milk intake of 20–32 and 54–71 g/d by
kittens suckling on queens fed diets containing 10 and 20% fat,
respectively. To our knowledge, direct measurements of milk intake in
kittens during the suckling period using the isotope dilution technique
are not available.
Given the known problems associated with the WSW method, we decided to use the isotope dilution technique to increase the accuracy of estimates of milk and nutrient intake in suckling kittens. Milk intake of kittens during the first 4 wk of life was studied using tritiated water (THO) as a marker. Furthermore, at the end of the main study, the accuracy of the WID technique in estimating milk intake was assessed by tube feeding six kittens over a period of 48 h.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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). Animals, housing and diets.
Five lactating domestic short-haired queens (Felis
catus) and their offspring were maintained in standard
metabolism cages (described in Hendriks et al. 1999
)
normally used for the rearing of kittens in a closed colony
(Heinz-Wattie’s Companion Animal Nutrition Research Unit, Massey
University, Palmerston North, New Zealand). All queens had been
vaccinated against feline rhinotracheitis, calicivirus and
panleukopenia using a modified live vaccine (Felocell CVR, Norden
Laboratories, München, Germany). Feline leukemia and feline
immunodeficiency virus have not been detected in the colony since its
establishment in 1976. One queen gave birth to three kittens and four
queens gave birth to four kittens. The range in body weights of the 19
kittens (10 males and 9 females), measured within 24 h after
birth, was 100–140 g (mean ± SEM, 120 ± 2 g). On postnatal day 3, the kittens in each litter were weighed
accurately and a sterile microchip (Life Chip, Animal ID Electronic
Systems, Kiama, NSW, Australia) was inserted subcutaneously for
individual identification before subsequent experimental procedures
such as weighing, injection of tritiated water and blood sampling. The
queens were given free access to a homogenized mixture of moist canned
cat foods and lactose-free milk throughout the study. Table 1
shows the analyzed composition of the mixture of canned cat foods and
the lactose-free milk. Fresh drinking water was available at all
times. The body weights of the queens and kittens were recorded at
regularly preset intervals throughout the study.
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The queens and their offspring were considered healthy on the basis of
clinical examination and hematologic status before the start of the
study. In the morning of postnatal days 3, 10, 17 and 24, each kitten
was weighed and given an accurately weighed amount (~2 mL/kg body
weight) of sterile isotonic (9 g/L) saline containing 25 mCi (925
MBq)/L of THO (Life Sciences Technologies, Auckland, N.Z.) by
intraperitoneal injection. In each litter, one blank kitten served as a
control for the calculation of recirculation of THO, due to the uptake
of kittens’ urinary and fecal water by the queen (Baverstock and Green 1975
); that kitten, therefore, received only an
intraperitoneal injection of sterile isotonic saline. After injection,
the kittens were physically separated from the queen for 2 h to
allow full equilibration of the injected isotope and to prevent any
water exchange between the queen and the kittens. After the 2-h
equilibration period, a blood sample from the jugular vein was taken
from each kitten using a 1-mL syringe mounted with a 27-gauge needle;
the kittens and queen were then returned to the metabolism cage. A
further blood sample of each kitten was obtained 4 d after
injection. Handling of the kittens was kept to a minimum, and efforts
were made to reduce the disturbance of the mother-young
relationship.
Measurement of blood plasma THO.
Each blood sample (0.2–0.4 mL) of a kitten was immediately transferred into a 0.5-mL heparinized Eppendorf tube. The blood was then used to fill 3–5 standard (75-µL) hematocrit capillary tubes and centrifuged at 14,800 x g for 15 min using a Heraeus hemofuge (Heraeus Sepatech GmbH., Osterode, Germany). The hematocrit values were recorded; then the capillary tubes were cut, and the plasma was used to fill two 50-µL calibrated micropipettes (Vitrex, Hounisen, Risskov, Denmark). Each micropipette was transferred directly into a scintillation vial containing 8 mL of scintillation fluid [67 parts toluene and 33 parts triton X-100 containing 0.4% 2,3-diphenyloxazole (PPO)], and the radioactivity was counted using a Wallac 1414 liquid scintillation spectrometer (Wallac OY, Turku, Finland). Any remaining plasma samples of the kittens were pooled per period (3–7, 10–14, 17–21 and 24–28 d postpartum) for dry matter analysis. Standards were made up by dilution (1:1000) with distilled water of the THO solution used for injection, and corrections were made for the quenching effect of the plasma samples. The average counting efficiency of tritium was 42%.
Chemical analysis.
Dry matter (DM) of plasma samples was determined in duplicate by freeze
drying and subsequent oven drying at 105°C. Dry matter of the diets
and the milk replacer was determined in duplicate by desiccation at
105°C. Ash was determined by heating samples at 550°C for 16 h. Total nitrogen was determined using the Kjeldahl method with crude
protein calculated by multiplying total nitrogen by 6.25. Lipid was
determined by petroleum ether extraction of freeze-dried samples
(AOAC 1980
). Amino acids were determined as described by
Hendriks et al. (1996)
. All measurements were performed
in duplicate and the chemicals used were analytical grade.
Total body water and biological half-life of body water turnover.
The body water content of the kittens at various ages, which is
required in the calculation of water intake, was estimated using the
following regression line [values are: estimate (±SEM)]:
 | (1) |
The regression line was obtained by least-squares regression
of the water content of newly born to 6-wk-old kittens published by
Thomas (1911)
, Widdowson (1950)
and
Stratmann (1988)
. The biological half-life
(T1/2) of body water in the kittens was calculated
from rates of elimination from the body water pool of the injected THO
over the 4-d observation period. The tritium radioactivity in plasma
water at 2 and 96 h after injection of THO and the equations
published by Coward et al. (1982)
were used to calculate
water intake in THO-injected kittens. Recycling of THO between the
queen and her kittens during wk 1 was accounted for by subtraction of
the plasma water counts of the blank kitten at 96 h from the
corresponding individual values of the THO-injected kittens.
Recycling of THO during wk 2, 3 and 4 was calculated similarly, with
the recycling of THO determined from the difference between calculated
and measured plasma counts of the blank kitten at 96 h. The
calculated plasma THO radioactivity was determined using the plasma
counts at 2 h and the average fractional rate of water turnover of
the THO-injected kittens during the previous period.
Calculation of milk intake.
The daily milk intake was calculated from the water intake data using
the equations published by King et al. (1993)
. Because
the changes in the composition of the major constituents in queen’s
milk appear to be rather small within the first 4 wk of lactation
(Adkins et al. 1997
, Dobenecker et al. 1998
), and because such changes cause only very small errors in
the calculated value for daily milk intake (Pettigrew et al. 1987
), the following composition of queen’s milk (compiled
from literature values) was used for calculations in this study: 79.4%
water, 8.2% crude protein, 5.5% fat and 5.5% lactose. The
digestibility of milk protein, fat and lactose was assumed to be close
to 100% (Kienzle and Kamphues 1991
). Full oxidation of
one gram of protein, fat and lactose in vivo was taken to yield 0.41,
1.07 and 0.60 mL of water, respectively (Brody 1945
).
Potential metabolic water deposited as protein and fat (King et al. 1993
) was calculated using the body dry matter gain
(DMgain) of each kitten over the measurement period and
values of 62 and 22 g/100 g dry matter for body protein and fat content
of the kittens, respectively (Stratmann 1988
). Body dry
matter gain over the measurement period was determined using the body
weight gain over each experimental period (4 d) and the average body
water content of kittens at the median of the observation period. The
latter value was calculated using the regression equation (Eq. 1)
given
above. The following presents the final equation whereby the daily milk
intake (MI) of the kittens was calculated from total water intake
(TWI):
 | (2) |
Statistical analysis.
The body weight data of the kittens were subjected to
repeated-measures ANOVA with litter and gender as variables and
days postpartum as the repeated measure (Cody and Smith 1987
). The milk intake data were subjected to ANOVA
(split-plot) using the General Linear Model with queen, gender, sex and
kitten as fixed variables and kitten within queen and sex as the error
term to account for the repeated measurements of milk intake
(Cody and Smith 1987
). The data on the biological
half-life of body water were subjected to a least-squares
linear regression analysis with body weight as the independent variate
and the biological half-life as the dependant variate. A
no-intercept multiple regression analysis was performed on the milk
intake data with milk intake (g/d) as the dependent variable and
metabolic body weight (kg0.75) and body weight gain (g/d)
as the independent variates. All statistical analyses were performed
using the SAS statistical package (SAS version 6.12, SAS Institute,
Cary, NC), and effects were considered significant at P
< 0.05. Values in the text are means ± SEM.
Validation of the THO method for measuring milk intake in growing kittens.
At the end of the 4-wk study, six kittens (one male, one female
from each of three litters) were given an intraperitoneal injection of
THO in isotonic saline as described above and separated from the queen
for 2 d in an insulated nest box. After a 2-h equilibration
period, the kittens were fed a freshly prepared milk replacer by
stomach tube (Baxter Feeding Tube no. K31, Baxter Healthcare,
Deerfield, IL) for 48 h to test the accuracy of the water isotope
dilution technique in determining milk intake in growing kittens. The
kittens were fed a known amount of warm (±40°C) milk replacer three
times a day at an energy level allowing minimal body weight gain to
minimize the risk of diarrhea due to overfeeding. The exact amount of
milk replacer was determined by accurately weighing the syringe +
stomach tube immediately before and after each feeding. Blood sampling
and THO analysis were as described above. Daily milk intake was
calculated using the composition of the milk replacer shown in Table 1
and compared with the amount given by stomach tube.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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). There was a significant (P < 0.001) effect of time
and no significant (P > 0.05) effect of litter and
gender on the body weight of the kittens as determined by
repeated-measures ANOVA. There was a significant (P
< 0.001) interaction between litter and time on the body weights
of the kittens. The queens lost weight throughout the study,
particularly during wk 3 and 4 postpartum. The average daily intake of
ME of the queens increased during the first 3 wk of the study from 392
kJ/kg body weight during wk 1 to 513 kJ/kg body weight during wk 3.
During wk 4, the daily ME intake of the queens decreased to 477 kJ/kg
body weight.
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). At the end of the study, the hematocrit of the kittens was 0.19
± 0.01. The dry matter content of the kittens’ plasma, as
measured using the pooled samples, remained constant throughout the
4-wk study (6.8 ± 0.1%). Recirculation of THO as measured at
96 h after injection during wk 1–4 accounted for 5.9 ± 0.8,
12.0 ± 0.5, 7.7 ± 1.3 and 10.0 ± 1.3% of the daily
water intake, respectively. Figure 2
shows the linear regression line relating the biological half-life
of body water to the body weight (bwt) of the kittens during the 4-wk
experimental period. The following significant regression line was
obtained [values are: estimate (±SEM)]:
 | (3) |
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Milk intake of the kittens remained relatively constant throughout the
study (Fig. 3
) although there were significant (P < 0.05) effects of
litter, time and the interaction between litter and time on milk
intake. There was no effect of gender on milk intake. Daily milk intake
of the kittens (n = 14) during wk 1–4 were 47.3 ±
0.8, 47.4 ± 1.5, 48.7 ± 1.6 and 43.7 ± 2.0 g, respectively. Multiple
regression of the milk intake data on metabolic body weight (MBW) and
body weight gain (gain) yielded the following significant (P
< 0.001) equation [values are: estimates (±SEM)]:
 | (4) |
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Four of the six kittens used in the validation study (wk 5) gained weight (mean: 5.5 g/d), whereas two kittens lost body weight (mean: -1 g/d). Diarrhea was not observed during the 48-h period when the kittens were fed the milk replacer. The daily intake of milk replacer, estimated using the WID technique, ranged from 0.3% underestimation to 7.2% overestimation with an average overestimation of daily milk intake of 2.4 ± 1.2%.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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for a total of 100 kittens. In wk 4, the average weight
gain of the kittens was lower than the values reported by
Loveridge (1987)
, which could be attributed to the
failure of two kittens to gain body weight. At the end of the study,
however, the average body weight of the kittens was higher than the
average body weights (373 ± 5 g, n = 128) of
kittens of a similar age recorded in the colony. The failure of two
kittens to gain body weight in the final week of the study was due to a
low milk intake (75 and 70 g per kg MBW). There was no effect of
litter or gender on the body weight of the kittens in this study as
analyzed by repeated-measures ANOVA. Loveridge (1987)
also found no effect of gender on the body weight of
kittens until 6 wk of age; the male kittens were significantly heavier
after that time. The body weight of the queens in this study decreased
throughout lactation and at the end of wk 4, the average body weight of
the queens was reduced to 79% of the value recorded at the start of
lactation. The mean daily energy intake of the queens in this study was
similar to that reported by Loveridge (1986)
, except for
wk 4 when a decrease in the intake of ME was recorded. At the same
time, the queens experienced heavy weight loss, indicating that body
reserves were mobilized to provide energy and nutrients to maintain
milk production. In this situation, the reduced intake of ME by the
queens is likely to have caused a lower milk production, resulting in a
lower weight gain of the kittens in the last week of the study.
In the kittens the decreasing hematocrits observed throughout the study
(Fig. 1)
document the development of "suckling anemia," a
phenomenon that has been observed in rapidly growing suckling young of
other species (Garcia 1957
, Widdowson 1965
). By measuring iron levels in the body of suckling
kittens, McCance and Widdowson (1951)
showed that blood
iron levels decreased from birth to 3 wk of age. Garcia (1957)
showed that the rapid body growth of suckling rats leads
to a marked decrease in the hematocrit value and the hemoglobin
concentration of whole blood during early postnatal life. This occurred
in spite of a marked increase in total red cell volume and
whole-body hemoglobin, indicating a continual high rate of
erythropoiesis, exceeded by higher rates of body fluid accretion and
body mass gain (Garcia 1957
). The repeated blood
sampling in this study also affected the hematocrits, but the effect is
believed to be of minor importance because the amount of blood taken
(0.2–0.4 mL) represented only a small fraction of the kittens’ total
blood volume.
In applying the WID technique to studies of water turnover in the
mammalian body, a number of basic assumptions have to be fulfilled,
including water isotope equilibration, size of the body water pool,
sources and rates of water exchange and loss of isotopes. The
assumptions, prerequisites and the potential errors inherent in using
this technique for determinations of water fluxes in animals and humans
and its implications for reliable estimates of the milk intake in
various species have been reviewed (Coward et al. 1982
,
Fjeld et al. 1988
, Nagy and Costa 1980
).
In this study, a 2-h period for THO equilibration was used because this
seems to be a commonly accepted equilibration time for water isotopes
in small mammals weighing <10–20 kg (Fjeld et al. 1988
, Macfarlane et al. 1969
, Oftedal 1984
, Pettigrew et al. 1985
, Pluske et al. 1998
). At the end of the study, an equilibration time curve
was obtained from the use of six kittens injected with THO, and it was
shown that full equilibration of THO in kitten’s body water was
attained in <1 h (Hendriks, unpublished observations). In this study,
the recirculation of THO due to the uptake of urine and feces by the
queen was measured in unlabeled kittens during wk 1; these values,
therefore, can be expected to be accurate. To allow repeated
measurements on the same litter and take into account recirculation of
THO, a previously THO-injected kitten was used as a "blank"
during wk 2 to 4. In these cases, the calculations of recirculated THO
were corrected for residual THO radioactivity in plasma water from the
previous measurement period, and the calculated values for wk 2–4,
therefore, are theoretically slight overestimates. THO recirculation
values found for wk 1–4 were 5.9 ± 0.8, 12.0 ± 0.5, 7.7
± 1.3 and 10.0 ± 1.3%, respectively.
The biological half-life of body water in the kittens increased
from 2 d in wk 1 to 4 d in wk 4 (Fig. 2)
; the latter value is
similar to that observed in 3-wk-old suckling puppies (4.2–4.6 d)
(Oftedal 1984
). In suckling mink kits, weighing 20–140
g, the biological half-life increased from <1 d to ~2 d
(Wamberg and Tauson 1998
), whereas in 1- to 3-wk-old
blue fox cubs (Alopex lagopus), the T1/2
value of body water ranges from 1.7 to 2.2 d (Wamberg,
unpublished). In suckling rat pups, T1/2 is ~1.5 d
(Coward et al. 1982
); in human infants weighing 7.8 kg,
Fjeld et al. (1988)
reported a mean value of
T1/2 of 2.7 d. These values underscore the rapid
turnover rate of body water in suckling young animals.
The isotope dilution technique has been used extensively to measure
milk intake in a number of mammalian species, including humans
(Butte et al. 1983
), baboons (Buss and Voss 1971
), sheep (Macfarlane et al. 1969
), rats
(Coward et al. 1982
), dogs (Oftedal 1984
), pigs (Pluske et al. 1998
) and mink
(Wamberg and Tauson 1998
). In this study, we have
applied the WID technique for the first time to study milk intake in
suckling kittens and determine the accuracy of this technique to
measure milk intake in kittens. The measurement of milk intake by the
WID technique in the tube-fed kittens showed a high degree of
accuracy. The mean difference between the predicted and actual milk
intake of the six measurements was 2.4%. This value is similar to the
recovery values reported in infants of 2.0% (Fjeld et al. 1988
), calves 2.5% (Holleman et al. 1975
),
lambs 3.3% (Macfarlane et al. 1969
), and pigs 2.9%
(Pettigrew et al. 1987
). These results indicate that the
results presented on the milk intake of kittens in this study were
accurate.
The average daily milk intake of the kittens remained surprisingly
constant throughout the first 4 wk postpartum (Fig. 3)
. However, there
was a significant effect of time on milk intake and a significant
interaction between milk intake and litter, indicating that milk
production patterns of the five queens were different over time. The
body weight gain of the kittens also showed a significant effect of
time; the kittens were found to grow at a different rate as indicated
by the significant interaction of time and litter. Jayawickrama et al. (1998)
found a significant difference between the milk
intake of kittens for wk 1 and 4 and statistically similar milk intakes
among other weeks. Dobenecker et al. (1998)
also used
the WSW technique to measure milk intake of kittens during three
periods (wk 1, 2–4, 5–9) and found a higher milk yield of queens
during the wk 2–4 period compared with wk 1 and a lower milk yield
during the wk 5–9 period. The results in this study are in contrast to
the increasing milk intake with increasing age observed in the suckling
young of baboons (Buss and Voss 1971
), rats
(Coward et al. 1982
), dogs (Oftedal 1984
)
and mink (Wamberg and Tauson 1998
). In pigs,
Pluske et al. (1998)
found a significant decrease in
milk intake with increasing age. Many factors may influence milk
production throughout lactation in mammals, including factors such as
stage of lactation, the number of suckling animals, suckling intensity,
temperature, season, dietary protein and energy intake
(Dobenecker et al. 1998
, Jayawickrama et al. 1998
, King et al. 1993
, Pluske et al. 1998
).
Milk intake and the growth of the suckling offspring are highly
correlated because milk is the sole source of nutrients for the young
animal. The milk ingested by the kittens in this study would have been
used first for the maintenance of body mass; any intake of milk in
excess of maintenance would have been used for growth of body tissue.
The average body weight of the kittens in this study increased with
age, whereas the growth rate decreased with age (Fig. 2)
, indicating
that the amount of milk available for body gain decreased throughout
the 4-wk lactation period. The multiple regression equation obtained in
this study (Eq. 4)
shows that 77.9 g of milk were required per
unit metabolic body weight per day for maintenance and 1.7 g were
required per gram of body growth. Assuming that milk energy contains
4.6 kJ ME/g, this equates to suckling kittens requiring 356
kJ/(kg0.75·d) for maintenance. This value is
close to the basal metabolic rate of kittens [288
kJ/(kg0.75·d)] as measured by oxygen uptake of
1- to 6-wk-old kittens (Hill 1959
). Similar values [300
and 334 kJ/(kg0.75·d)] for maintenance have
been found in suckling dogs (Crighton and Pownall 1974
,
Mundt et al. 1981
). This value, however, is considerably
lower than values normally found for pigs of 458
kJ/(kg0.75·d) (Lawrence and Fowler 1997
) and adult cats (NRC 1986
) and dogs
(NRC 1985
) of 438 and 552
kJ/(kg0.75·d), respectively. Kittens and dog
puppies are born with a dense hair coat and exhibit very low physical
activity because they sleep most of the day. They huddle together and
are kept warm by the queen or bitch most of the time. All of these
factors will reduce the energy requirement for maintenance to a level
closer to the basal metabolic rate of the animal. The efficiency of ME
deposition can be calculated using the data in this study. Per gram of
body growth, 1.7 g of milk or 7.8 kJ ME is required per day.
Assuming that the body weight gain consisted of 76.6% water, 14.4%
protein and 5.8% fat (Stratmann 1988
), the energy
stored per unit of growth was 5.5 kJ/d. The efficiency
(kg-value) with which metabolizable
energy was converted to net energy in the kittens in this study was
0.71. This is similar to other animals such as pigs, in which
kg-values of 0.65 and 0.69 have been
reported (Lawrence and Fowler 1997
, Van der Hel and Verstegen 1987
). It has been noted by several authors that
in doubling its body weight in <8 d, the cat is one of the fastest
growing mammals (Bernhart 1961
, Thomas 1911
, Widdowson 1965
). This study indicates that
the high growth rate of cats may be due mainly to the lower energy
requirement for maintenance, ~360 kJ/(kg0.75
· d), whereas the ME requirement per unit of body growth is similar
to that of other mammals.
The average daily milk production of the queens in this study (as a
percentage of the queens’ body weight) ranged from 5.1 ± 0.3%
during wk 1 to 6.1 ± 0.4 and 6.1 ± 0.4% during wk 3 and 4,
respectively. Dobenecker et al. (1998)
measured milk
production of queens using the WSW technique and reported corrected
estimates of milk production of queens nursing litters of 3–4 kittens
during wk 1 of 4.0% and during wk 2–4 of 5.7%. However, the
expression of the daily milk yield as a percentage of body mass may be
misleading because queens may lose a considerable amount of body mass
during lactation. Estimates made by Dobenecker et al. (1998)
for wk 1 of lactation are lower than the estimates
obtained in this study, and their data show a distinct relationship in
the milk yield and lactation stage, which is likely to be caused by the
WSW technique used to measure milk intake. The differences between
these two techniques in estimating milk intake have been attributed to
stress resulting from repeated interference and frequent handling of
the young, to lack of suckling stimulus, small errors in frequent
weighings, loss of excreta and to the effects of water recycling
(Baverstock and Elhay 1981
, Coward et al. 1982
, Oftedal, 1984
, Pettigrew et al. 1987
). Similarly, in recent studies of the milk intake of
suckling kittens using the WSW technique, Dobenecker et al. (1998)
and Jayawickrama et al. (1998)
found
lower growth rates of the kittens during the measurement period than
those of the same kittens in periods in which they were not separated
from the queens. These lower growth rates are likely to have resulted
from stress of the queens and kittens, lower milk intake of the
kittens, lower milk output by the queen, water recirculation or a
combination of these factors.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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2 Supported by the Danish Agricultural and Veterinary Research Council, grant no. 9502267.
4 Sabbatical visitor at the Heinz Wattie’s
Companion Animal Nutrition Research Unit, Institute of Food, Nutrition
and Human Health, Massey University, Palmerston North, New Zealand.
5 Abbreviations used: bwt, body weight; DM, dry
matter; MBW, metabolic body weight; ME, metabolizable energy; MI, milk
intake; MWI, milk water intake; PPO, 2,5-diphenyloxazole;
T1/2, biological half-life; THO, tritiated water; TWI,
total water intake; WID, water isotope dilution; WSW,
weigh-suckle-weigh.
Manuscript received May 21, 1999. Initial review completed July 3, 1999. Revision accepted August 17, 1999.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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1. Adkins Y., Zicker S. C., Lepine A., Lönnerdal B. Changes in nutrient and protein composition of cat milk during lactation. Am. J. Vet. Res. 1997;58:370-375[Medline]
2. Anonymous Code of Ethical Conduct for the Use of Live Animals for Teaching and Research rev. ed. 1992 Massey University Palmerston North, New Zealand.
3. Association of Official Analytical Chemists Official Methods of Analysis 12th ed. 1980 AOAC Washington, DC.
4. Baverstock P. R., Elhay S. Water balance of small lactating rodents III. Estimates of milk production and water recycling in lactating Mus musculus under various water regimes. J. Math. Biol. 1981;13:1-22[Medline]
5.
Baverstock P. R., Green B. Water recycling in lactation. Science (Washington, DC) 1975;187:657-658
6. Bernhart F. Correlation between growth-rate of the suckling of various species and the percentage of total calories from protein in the milk. Nature (Lond.) 1961;191:358-360
7. Brody S. Bioenergetics & Growth 1945:35-36 Hafner Publishing Company New York, NY.
8. Buss D. H., Voss W. R. Evaluation of four methods for estimating the milk yield of baboons. J. Nutr. 1971;101:901-910
9.
Butte N. F., Garza C., Smith E. O., Nichols B. L. Evaluation of the deuterium dilution technique against the test-weighing procedure for the determination of breast milk intake. Am. J. Clin. Nutr. 1983;37:996-1003
10. Cody R. P., Smith J. K. Repeated measure design. Applied Statistics and the SAS Programming Language 2nd ed. 1987:133-177 Elsevier Science Publishing Amsterdam, The Netherlands.
11. Coward W. A., Cole T. J., Gerber H., Roberts S. B., Fleet I. Water turnover and the measurement of milk intake. Pflüg. Arch. 1982;393:344-347
12. Crighton G. W., Pownall R. The homeothermic status of the neonatal dog. Nature (Lond.) 1974;251:142-144[Medline]
13. Dobenecker B., Zottmann B., Kienzle E., Wolf P., Zentek J. Milk yield and milk composition of lactating queens. J. Anim. Physiol. Anim. Nutr. 1998;80:173-178
14.
Fjeld C. R., Brown K. H., Schoeller D. A. Validation of the deuterium oxide method for measuring average daily milk intake in infants. Am. J. Clin. Nutr. 1988;48:671-679
15.
Garcia J. F. Changes in blood, plasma and red cell volume in the male rat, as a function of age. Am. J. Physiol. 1957;190:19-24
16. Hendriks W. H., Moughan P. J., Tarttelin M. F. Gut endogenous nitrogen and amino acid excretions in adult domestic cats fed a protein-free diet or an enzymatically hydrolyzed casein-based diet. J. Nutr. 1996;126:955-962
17. Hendriks, W. H., Wamberg, S. & Tarttelin, M. F. (1999) A metabolism cage for quantitative urine collection and accurate measurement of water balance in adult cats (Felis catus). J. Anim. Physiol. Anim. Nutr. (in press).
18. Hill J. R. The oxygen consumption of new-born and adult mammals. Its dependence on the oxygen tension in the inspired air and on the environmental temperature. J. Physiol. (Lond.) 1959;149:346-373
19.
Holleman D. F., White R. G., Luick J. R. New isotope methods estimating milk intake and yield. J. Dairy Sci. 1975;58:1814-1820
20. Jayawickrama L., Jacobsen K., Lepinel A. J., Rogers Q. R., Lönnerdal B. Factors affecting milk intake of kittens. FASEB J 1998;12:A836(abs.)
21. Kienzle E., Kamphues J. Gesundheitsstörungen bei Katzenwelpen nach Einsatz ungeeigneter Milchaustauscher. Kleintierpraxis 1991;36:264-268
22. King R. H., Toner M. S., Dove H., Atwood C. S., Brown W. G. The response of first-litter sows to dietary protein level during lactation. J. Anim. Sci. 1993;71:2457-2463[Abstract]
23. Lawrence T.L.J., Fowler V. R. Growth of Farm Animals 1997 CAB International Oxford, UK.
24. Loveridge G. G. Bodyweight changes and energy intake of cats during gestation and lactation. Anim. Technol. 1986;37:7-15
25. Loveridge G. G. Some factors affecting kitten growth. Anim. Technol. 1987;38:9-18
26. Macfarlane W. V., Howard B., Siebert B. D. Tritiated water in the measurement of milk intake and tissue growth of ruminants in the field. Nature (Lond.) 1969;221:578-579[Medline]
27. McCance R. A., Widdowson E. M. The metabolism of iron during suckling. J. Physiol. (Lond.) 1951;112:450-458[Medline]
28. Mundt H. C., Thomée A., Meyer H. Zur Energie und Eiweissversorgung von Saugwelpen über die Muttermilch. Kleintierpraxis 1981;26:353-360
29.
Nagy K. A., Costa D. P. Water flux in animals: analysis of potential errors in the tritiated water method. Am. J. Physiol. 1980;238:R454-R465
30. National Research Council Nutrient Requirements of Dogs rev. ed. 1985 National Academy Press Washington, DC.
31. National Research Council Nutrient Requirements of Cats 1986 National Academy Press Washington, DC.
32. Oftedal O. T. Lactation in the dog: milk composition and intake by puppies. J. Nutr. 1984;114:803-812
33. Pettigrew J. E., Cornelius S. G., Sower A. F. A refinement and evaluation of the irsotope dilution method for estimating milk intake by piglets. Livest. Prod. Sci. 1987;16:163-174
34. Pettigrew J. E., Sower A. F., Cornelius S. G., Moser R. L. A comparison of isotope dilution and weigh-suckle-weigh methods for estimating milk intake by pigs. Can. J. Anim. Sci. 1985;65:989-992
35.
Pluske J. R., Williams I. H., Zak L. J., Clowes E. J., Cegielsji A. C., Aherne F. X. Feeding lactating primiparous sows to establish three divergent metabolic states: III Milk production and pig growth. J. Anim. Sci. 1998;76:1165-1171
36. Stratmann B. Untersuchungen zur Körperzusammensetzung von Katzen. Doctoral thesis 1988 Tierärztl. Hochsch. Hannover, Germany.
37. Thomas K. Über die Zusammensetzung von Hund und Katze während der ersten Verdoppelungsperioden des Geburtsgewichtes. Arch. Anat. Physiol. 1911;:9-38
38. Van der Hel W., Verstegen M.W.A. Metabolic rate of piglets between sucklings. Verstegen M. W. A. Henken A. M. eds. Energy Metabolism in Farm Animals, Effects of Housing, Stress and Disease 1987:63-69 Martinus Nijhoff Publishers Dordrecht, The Netherlands
39. Wamberg S., Tauson A.-H. Daily milk intake and body water turnover in suckling mink (Mustela vison) kits. Comp. Biochem. Physiol. 1998;119A:931-939
40. Widdowson E. M. Chemical composition of newly born mammals. Nature (Lond.) 1950;166:626-628
41. Widdowson E. M. Food, growth and development in the suckling period. Graham-Jones O. eds. Canine and Feline Nutritional Requirements 1965:9-17 Pergamon Press Oxford, England
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