IMPLICATIONS OF SEASONAL BIOENERGETIC CYCLES
OF WAPITI (CERVUS ELAPHUS)
Robert J. Hudson, Ray Nixdorf, Michael Kam and Zhigang Jiang
Renewable Resources, 751 GSB,
University of Alberta,
Edmonton T6G 2H1
ABSTRACT
This study explores seasonal energetic cycles of wapiti hinds with a view to
developing systems of optimal nutritional management. We examined the
maturation of seasonal cycles of intake, bioenergetics and growth from weaning
to reproductive maturity. Following up questions arising in previous studies,
this work was designed to test the hypothesis that seasonal cycles of appetite
and energy demand are asynchronous, causing precipitous weight loss in early
spring and efficient gain in autumn.
Wapiti showed seasonal cycles of feed intake, maintenance requirements, and liveweight gain. Voluntary intake in the 1st year of life
showed a strong seasonal cycle ranging from 60 g/W0.75 in the winter
to a peak of 140 g/W0.75 the next summer. Requirements for liveweight maintenance generally paralleled seasonal ad libitum intakes except that estimated requirements
lagged behind feed intakes in spring. Requirements for liveweight
maintenance of full fed animals declined to about 800 kJ/W0.75
in their 1st winter and rose to over 1500 kJ/W0.75 in summer.
Surprisingly, maintenance requirements of ad libitum
and restricted animals had to be calculated separately - requirements of
restricted animals were lower and not as seasonal.
The difference between intakes and maintenance requirements should be reflected
in average daily gains. Contrary to previous studies, gains and feed conversion
efficiencies in spring were high. Therefore, evidence for asynchronous cycles
was not found. Feed intake seemed to drive the seasonal energetic cycle.
Prolactin and thyrotrophin
changed in unison but did not reveal clear cycles of appetence or energy
demand. Contrary to other work on deer, these hormones were not closely linked
to bioenergetic cycles.
INTRODUCTION
The promise of game farming was to develop a sustainable system of animal
production which capitalized on the ecological and metabolic adaptations of
indigenous wild ruminants. This has not always been put into practice. Wapiti
on farms tend to be intensively managed and winter supplementation has been
used to smooth seasonal cycles of body condition without knowing whether this
is necessary or even desirable. Research supported by a previous grant from
Farming to the Future (#90-0688, Hudson et al. 1992) suggests that game farmers
should work with the seasonal cycle rather than against it. However,
that work pointed to an interesting complication; namely, that wapiti may
experience precipitous weight loss in spring even on good forage and gain
unexpectedly efficiently in autumn. This project was undertaken to
understand why.
Photoperiodic cycles of appetence, energy expenditure and subsequently weight
changes are well-developed in farmed game such as wapiti and
Both feed intake and energy expenditure (even fasting metabolic rates) are generally
high in summer and low in winter. However, fasting metabolic rates usually are
measured after a short fast and do not follow the 4-6 weeks of maintenance
feeding required by standard protocols. In reindeer, variation in previous feed
intake seems to fully account for variation in energy expenditure so appetite
is considered to be the primary cycle which metabolism simply follows (Nilssen et al. 1984). Recent studies on white-tailed deer (Pekins et al. 1991) suggest that energy expenditures simply
mirror appetite. Estimates of year-round maintenance requirements have been
based on pooled seasonal regressions (Suttie et al.
1987).
On the other hand, Simpson et al. (1978) detected a slight seasonal cycle in
maintenance requirements (as opposed to energy expenditures) of
Evidence that cycles of appetence and energy
expenditure in theory can be uncoupled come from endocrinological
studies reviewed by Ryg (1986). Exogenous
administration of prolactin increases feed intake
whereas thyroid hormones increases energy expenditure (Ryg
and Jacobsen 1982).
The goal of our studies was to determine the nature and bioenergetic
consequences of the phase relationship of photoperiodic cycles of appetence and
energy demands in farmed wapiti. Specifically, we addressed the following
research hypotheses:
·
Seasonal
cycles of appetite and energy demand are independent when the complicating
effect of feeding level is controlled,
·
The
phase relationship between these two endogenous cycles causes deterioration of
body condition during spring and efficient fattening in late summer and autumn,
·
Endogenous
cycles are modulated by the imperatives of compensatory growth and
reproduction.
·
Energy
demands are correlated with thyroid activity and appetite with prolactin.
METHODS
Animals and Experiments
The study involved eight nutritional balance trials organized into two
experiments.
Experiment I examined seasonal energetics of
12 young wapiti hinds (females) during their 1st 18 months of life. Young
females were chosen to obviate complications of pregnancy in older hinds and of
the rut in stags.
From the 1992 calf crop dropped in May/June, 12 calves were selected and weaned
on September 3/92. Habituation of prospective experimental animals began
immediately with regular handling in the research compound. Intensive training
in the metabolism crates prepared them for the first set of seasonal trials at
the autumn equinox.
Within each season, energy and nitrogen balances were determined on 6 animals
on ad libitum feeding and 6 fed to calculated
maintenance (550 kJ ME/kg0.75 for adult hinds based on Jiang
& Hudson (1994) and twice that for calves during their first fall and
winter) for 3 weeks before and during the trial. The 1st of 6 trials was
conducted in the first autumn at 3-4 months of age and continued at
approximately 3 month intervals to the fall of the 2nd year of life.
Individuals alternated feeding levels and order of sampling between trials to
keep body condition even throughout the year.
Between trials, all animals were kept on natural pasture and supplemented with
alfalfa dehy pellets (10 kJ ME/g) and good grass hay ad
libitum (on winter and early spring pasture). The
hay was removed 2 weeks before the trial and one group was restricted to
calculated seasonal maintenance and the other continued to receive pellets ad
libitum.
Experiment 2, conducted during the second year of the study, was intended to compare pregnant and non-pregnant hinds. Six
long yearlings from Experiment 1 and 6 adult hinds drawn from the Ministik herd
were used in balance trials conducted in late winter (March 94) and spring (May
94). Alfalfa-barley pellets (Table 1) rather than dehy
pellets were used. Grass hay was offered free-choice along with alfalfa-barley
pellets between trial periods. Unfortunately, unexpected pregnancies among the
yearlings eliminated the control group so the incremental costs of gestation
could not be determined.
New groups of animals (6 lactating and 6 non-lactating adult hinds) were
selected in late July. They were placed in individual feeding pens with creep
access for calves. Daily feed intakes and liveweight
gains over a 2 week period were obtained. Digestibilities
of the pelleted diet were assumed similar to the late
winter/spring trials and differences between lactating and non-lactating
animals were assumed negligible. Weather during this period was too hot to
determine diet metabolizability in metabolism crates.
Balance Trials
Balance trials were conducted according to a CCAC approved protocol developed
over several years at the Ministik Research Station. Because there are only 6
crates at the research station, seasonal trials were conducted in two rota, each with three animals at
each feeding level.
Each trial consisted of at least a 2 week adaptation period to the feeding
levels followed by a 1 week balance trial. Each animal spent 2 days in a
metabolic crate to determine feed intake and fecal and urine production. On the
3rd day, the animals were removed, and excreta were collected. Typically this
procedure required approximately 6 h, following which the animals returned to
the same chambers for another 2 days. This protocol was repeated twice
successively with groups of 6 animals.
During each rota, 24 h continuous measurements were
made of oxygen consumption and methane production of two animals from each
feeding level. The open circuit calorimetry system
followed the general design described by Kelly et al. (1994). Air drawn through
closed metabolism crates at 180 l/min was dried and subsampled
for determination of oxygen (Beckman paramagnetic analyzer) and methane (Servomex infrared methane analyzer). Volumes were corrected
to STDP from air temperature, relative humidity and atmospheric pressure. The
caloric equivalent of oxygen was assumed to be 20.5 kJ/l.
Occasional high fecal outputs gave negative digestion estimates so ratios of
lignin (Goering & van Soest
1970) in feed and feces were used to calculate seasonal digestibilities.
Although a variety of models could be used (France et al. 1989), regression of liveweight change (g/W0.75) on ME intake (kJ/kg0.75)
provided estimates of energy requirements for maintenance.
An attempt was made to further understand seasonal appetence and apparent
digestibility by determining the kinetics of digestion. Chromium-mordanted ground alfalfa was administered and fecal samples
were collected at regular intervals over a 4 day period (Fig. 1). Chromium was
measured by atomic absorption spectrophotometry
(Fenton & Fenton 1979). Marker concentrations were fit by nonlinear
regression using a two-compartment time-dependent model (Grovum
& Phillips 1973, Spalinger & Robbins 1992):
Y(t)=A(e-k1(t-TT)-e(-k2(t-TT))
where,
Y(t) is the fecal marker concentration at time t in hours, k1 is the rate of ruminal emptying and k2 is the rate of emptying of the
hindgut, TT is the transit time. A is a fitted parameter representing the
theoretical maximum initial marker concentration. The summary measure, turnover
time, was calculated as TT+1/k1+1/k2.
Blood samples (10ml) were taken on the afternoon of the last day of each trial
for determination of prolactin and thyroid
stimulating hormone (sTSH). Hormone analyses were
conducted by Kasper and Associates Medical Laboratories, a local clinical
laboratory. Procedures were based on radioimmunoassays
using heterologous (human) standards with unknown
cross reactivity. However, this should only affect comparisons with studies
which have prepared specific cervid reagents.
Comparisons among seasons in this study should be valid.
RESULTS AND DISCUSSION
Growth
Wapiti calves used in Experiment 1 weaned at 100 kg and continued to grow
(although more slowly) throughout the winter. However, confinement for seasonal
trials made them fall behind the performance expected of calves in their first
year of life (Fig. 2a,b). They entered their yearling
breeding season at 200 kg rather the target of over 220 kg expected by
industry. Although a 10% shortfall in weight is not great, it may have
sustained the appetite and growth impulse later into the year. By their second
birthday, animals weighed just under 250 kg. Mature
hinds used in Experiment 2 weighed over 300 kg.
Despite attempts to keep the restricted group at maintenance, average daily
gains were positive in most trials and were not always significantly lower than
those of animals fedad
libitum. (Fig. 3).
Following relatively high growth rates after weaning, growth slowed in winter
and again in their second autumn. Growth rates in late winter 1994 (March) were
complicated by pregnancy; the apparent difference between "feeding
levels" was due to the immanence of calving. In late spring (May) weeks
before the first calves were dropped, growth rates declined. Weight loss of
lactating hinds was much more profound than that of dry (yeld)
hinds.
Dry Matter Intake and Digestibility
As expected, wapiti fed ad libitum during
winter simply fed at maintenance levels (40-65 kJ/W0.75) and therefore differed
little from restricted animals (Fig. 4). Intakes doubled in spring and summer.
Intakes were low in late pregnancy and increased to about 100 g/W0.75 in
lactating animals which exceeded intakes of yeld
hinds by about 20%.
Digestibilities determined from lignin as an internal
marker declined from winter to summer and were similar in ad libitum and restricted groups (Fig. 5). These
bracketed values of 0.53 for dehy pellets in
previous spring trials (Hudson et al. 1993).
Interpretation of high digestibilities (about 75%) in
the winter 1994 trial must consider that alfalfa dehy
pellet was replaced by the Ministik alfalfa-barley pellet. This diet has been
used in many previous studies and typically is associated with digestibilities of 68-74% (Hudson et al. 1993, Jiang & Hudson 1992, 1994).
Differences between animals on restricted and ad libitum
feeding as well as pooled regression of digestibility on feeding level were not
significant. Generally, deer do not show dramatic changes in digestion or
passage rates despite strong seasonal differences in voluntary intake (Domingue et al. 1991, Sibbald and
Milne 1993).
Turnover times of digesta ranged from 25 to 60 h. The
main determinant appeared to be dry matter intakes (Fig. 6). No statistical
relationship was found between digestibility and turnover time.
Feed Conversion Efficiency
Feed conversion efficiencies expressed as daily gain (kg)/dry matter intake
(kg) changed seasonally with the growth impetus (Fig. 7). Normally, lowest feed
conversion efficiencies are expected in animals fed at or near maintenance with
highest efficiencies in animals fed at higher planes. In wapiti, this seems not
to be the case. There also was an unusual seasonal crossover.
Seasonal Requirements for Metabolizable Energy
Metabolizable energy requirements for maintenance and
gain were calculated by regression of ME intake (kJ/W0.75.d) against daily gain
(g/W0.75.d). The intercept (zero weight change) represents the maintenance
requirement (kJ/W0.75.d). The slope estimates the costs of depositing or
mobilizing body tissues in units of kJ/g. The original plan was to use ad libitum and restricted feeding to create a wide enough
range for firm estimates. However, it became clear that separate regressions
were required for the two groups (Fig. 8).
Metabolizable energy requirements for maintenance
were significantly different between ad libitum
and restricted groups in summer and fall but not in winter and spring when dry
matter intakes converged (Fig. 9). Although maintenance requirements are
defined as the feeding level at weight stasis, maintenance estimates paralleled
mean feed intakes. Thus, metabolic adaptation responds rapidly to the
nutritional environment. This corroborates a recent publication pointing to the
possibility that supplementing concentrates in winter increases the apparent
maintenance requirements of wapiti (Kozak et al.
1994).
At least in the ad libitum group, there was a
strongly developed seasonal cycle in energy demands even in the first 18 months
of life. Requirements during their first winter were considerably higher than
later in life even if pregnant (maintenance requirements in late pregnancy
should not, of course, be based on weight change because of growth of the conceptus and changes in body water). Summer maintenance
requirements of adult hinds were lower than those of yearlings and lactation
increases requirements of penned hinds by about 25%.
Studies at Ministik and elsewhere usually give comparable winter estimates in
the order of 450-550 kJ/W0.75.d (Fennessy et al.
1981, Suttie et al. 1987, Cool 1992, Jiang & Hudson 1994). Summer and fall values increased
to 720 and 876 kJ/W0.75.d, similar to an estimate of 728 kJ/W0.75.d provided by
Jiang & Hudson (1994). The additional energy
costs of free-existence increase this by about 200 kJ/W0.75.d (Jiang & Hudson 1992, Wairimu
et al. 1992).
Estimates of the energy costs of gain were not significantly different among
seasons. Compared with other studies (Jiang &
Hudson 1992, 1994, Wairimu et al. 1992, Cool 1992),
values generally were very low (in some cases negative!). More typical values are
in the range 16-37 kJ/g. Because lean tissue and associated water have an
energy content of only 5 kJ/g, the energy costs of gain need to at least double
to account for deposition efficiency. There is some evidence that efficiency of
gain varies by season with high values in summer (Jiang
& Hudson 1994). However, Milne et al. (1987) determined rather low
efficiencies of gain in calves during their first winter.
Endocrine Regulation
Seasonal cycles among cervids are, of course, under endocrinological control with melatonin the key mediator
(Lincoln 1985). This study focused on two hormones associated primarily with
appetite (prolactin) and energy expenditures (thyrotropin or thyroid stimulating hormone, sTSH).
There is ample evidence for this summary distinction. Administration of
exogenous prolactin increases feed intake and thyroid
hormones increase energy expenditures (Ryg 1986, Ryg & Jacobsen 1982). Conversely, suppression of prolactin secretion by bromocriptine
diminishes food intake and liveweight gain in
Although such specific functions can be associated with these hormones, we
found no evidence of a seasonal phase relationship. Seasonal patterns of prolactin (Fig. 9) and sTSH (Fig.
10) in young animals were similar. This parallel response is not entirely
unexpected because prolactin and thyrotropin
are both readily released by thyroid releasing hormone (Fraser & McNeilly 1982).
Highest annual values of both hormones in these young animals came later than
in most adult northern cervids (Lincoln 1985, Loudon
et al. 1989) where the peak focuses quite precisely on the longest day of the
year (21 June in the northern hemisphere), the mirror image of melatonin which
is secreted during hours of darkness. The exception is Pere
David's deer which has a prolactin peak in early May
in association with its early calving. Our findings are at odds with results of
Sibbald et al. (1993). We have no explanation for the
precipitous drop just before calving.
Although it may be convenient to think of prolactin
being associated with appetite and thyroid hormones with expenditures, endocrinological interrelationships are complex (Curlewis 1992). Prolactin also
has powerful liporegulatory effects (Meier 1977) and
may explain the propensity of deer to lean tissue growth in summer and
fattening in autumn (Verme 1988). Also, other
endocrine factors such as insulin-like growth factor-I (IGF1) seem important in
antler growth and the resurgence of spring growth (Suttie
et al. 1991).
CONCLUSIONS AND IMPLICATIONS
This project addresses significant questions about seasonal energetic cycles
which will become the basis of efficient new programs of nutritional management
of wapiti and perhaps other ruminant livestock. As well as controlling costs,
such programs may have implications for reproductive synchrony and life-long productivity
of breeding animals.
X Wapiti hinds have well-developed seasonal cycles of voluntary intake and
energy demands (maintenance requirements). These are superimposed on a general
decline in these bioenergetic parameters as animals
mature.
X The phase relationship between these 2 seasonal cycles is complex. The hypothesis that asynchrony between cycles of appetite and
energy demand would lead to precipitous weight loss in spring and efficient
gain in the fall was not supported.
X Compensatory gain and demands of gestation and lactation modulate seasonal
cycles. Young animals which are below target weights may maintain appetite and
growth despite declining daylength.
Xï Feeding level has a
strong effect on apparent maintenance requirements for liveweight
maintenance (intercept of regression of energy intake on weight change).
Requirements for animals fed near maintenance for several weeks were
considerably lower and could not be pooled with those animals fed ad libitum .
Xï This divergence challenges conventional approaches
to defining maintenance requirements and points to the inefficiency of feeding
concentrate diets ad libitum during winter.
Xï Although current high prices for breeding stock
and products give little incentive to control production costs, game farmers
will have to consider inputs as the industry grows and prices settle. Wapiti
farmers should pay closer attention to optimal feeding levels to achieve
production targets rather than feeding for maximum performance.
ACKNOWLEDGMENTS
Animal care and management was supervised and assisted by Chris Olsen, Unit
Manager of the
We are grateful for the generous assistance of Brian Kerrigan for designing the
calorimetry system, installing new equipment and
maintaining the old. Advice regarding operation/maintenance and the myriad of
calculations was always appreciated. Paul Gregory entertained our numerous
requests to borrow equipment and calibrate the calorimeter.
Pat Marceau provided able technical assistance in the
nutrition laboratory. Dylan Stewart and Dr. Kenneth Nagy of the Laboratory for
Structural Biology and Molecular Medicine,
As always, we are grateful to the Agricultural Research Council of Alberta for
financial support that has allowed our program to develop over the years and
the current project to proceed. NSERC shared operating costs and provided an
equipment grant to upgrade the calorimetry system.
This report was submitted on the last day of the existence of the Department of
Animal Science at the
LITERATURE CITED
Blaxter, K.L. 1962. The Energy
Metabolism of Ruminants.
Blaxter, K.L. & Boyne, A.W. 1982. Fasting and
maintenance metabolism of sheep. J. Agr. Sci. (Camb.) 99: 611-620.
Cool, N. 1992. Physiological indices of winter condition of wapiti and moose. MSc Thesis.
Curlewis, J.D. 1992. Seasonal prolactin
secretion and its role in seasonal reproduction: a review. Repro.
Fert.
Dev. 4: 1-23.
Curlewis,
J. D., Loudon, A. S., Milne, J. A. & McNeilly, A.
S. 1988. Effects of chronic long-acting bromocriptine
treatment on liveweight, voluntary food intake, coat
growth and breeding season in non-pregnant
Domingue,
B.M.F., Dellow, D.W.,
Fennessy,
P. F., Moore, G. H., & Corson,
Fenton, T.W. & Fenton, M. 1979. An
improved procedure for the determination of chromic oxide in feed and feces.
France, J. Dhanoa, M.S., Cammell,
S.B. et al. 1989. On the use of response functions in energy
balance analysis. J. Theor. Biol. 140: 83-99.
Fraser, H.M and McNeilly, A.S. 1982. Effect of chronic immunoneutralization of
thyrotropin-releasing hormone on the hypothalmic-pituitary-thyroid axis, prolactin
and reproductive function in the ewe. Endocrinology 111: 1964-1973.
Grovum,
W.L. & Phillips, G.D. 1973. Rate of passage of digesta in sheep. 5. Theoretical considerations
based on a physical model and computer simulation. Brit. J. Nutr.
30: 377-390.
Goering, H.K. & van Soest,
P.J. 1970. Forage fibre analyses (apparatus,
reagents, procedures and some applications). United States Department of
Agriculture,
Hudson, R. J., & Adamczewski,
J. Z. 1990. Effect of supplementing summer ranges on
lactation and growth of wapiti (Cervus elaphus).
Jiang, Z. &
Jiang, Z.
& Hudson, R.J. 1994. Seasonal energy requirements
of wapiti (Cervus elaphus)
for maintenance and growth.
Kelly, J.M., Kerrigan, B.K., Milligan, L.P. & McBride,
B.W. 1994. Development of a mobile, open-circuit
indirect calorimetry system.
Kozak, H.
M., Hudson, R. J., & Renecker, L. A. 1994.
Supplemental winter feeding. Rangelands, 16, 153-156.
Lincoln, G. A. 1985. Seasonal breeding in deer. pp
165-179. In P. F. Fennessy & K.
R. Drew (Eds.), Biology of Deer Production. Royal Soc. NZ,
Loudon, A. S. I., J.A. Milne, J.D. Curlewis
& McNeilly, A.S. 1989. A comparison of the
seasonal hormone changes and patterns of growth, voluntary food intake, and
reproduction in juvenile and adult red deer (Cervus
elaphus) and Pere
David's deer (Elaphurus davidianus)
hinds. J. Endocrinol. 122: 733-746.
McLean, J.A. & Tobin, G. 1987. Animal
and Human Calorimetry. Ca,mbridge Univ. Press,
Meier, A.H. 1977. Prolactin, the liporegulatory hormone. Adv.
Exp. Med. Biol. 80: 153-171.
Midwood,
A.J., Haggarty, P., McGaw,
B.A. & Robinson, J.J. 1989. Methane production in ruminants: its
effect on the double-labelled water method. Am. J. Physiol. 26: R1488-R1495.
Milne, J.A., Sibbald, A.M., McCormack, H.A. &
Loudon, A.S.I. .1987. The influences of nutrition and
management on the growth of
Milne, J. A., Loudon, A. S. I., Sibbald, A. M., Curlewis, J. D., & McNeilly,
A.S. 1990. Effects of melatonin and a dopamine agonist and
antagonist on seasonal changes in voluntary intake, reproductive activity and
plasma concentrations of prolactin and triiodothyronine in
Nilssen,
K. J., Sundsfjord, J.A. & Blix,
A.S. 1984. Regulation of metabolic rate in
Pekins,
P.J., W.M. Mautz & Kanter,
J. 1992. Reevaluation of the basal metabolic cycle in
white-tailed deer. pp. 418-422. In: R. D. Brown (ed).
The Biology of Deer.
Ryg, M. & Jacobsen, E. 1982. Effect of
thyroid hormone and prolactin on food intake and
weight change in young male reindeer (Rangifer tarandus tarandus).
Ryg, M. 1986. Physiological control
of growth, reproduction and lactation in deer. Rangifer
Spec. Issue 1: 261-266.
Shi, Z.D. & Barrell, G.K. 1991.
Effects of thyroidectomy on seasonal patterns of liveweight, testicular function, antler development and
molting in
Sibbald,
A.M., Fenn, P.D., Kerr, W.G., & Loudon, A.S.I.
1993. The influence of birth date on the development
of seasonal cycles in
Sibbald,
A.M. & Milne, J.A. 1993. Physical characteristics
of the alimentary tract in relation to seasonal changes in voluntary food
intake by the
Simpson, A. M., A.J.F. Webster, J.S.
Spalinger,
D.E. & Robbins, C.T. 1992. The dynamics of particle flow in the
rumen of mule deer (Odocoileus hemionus
hemionus) and elk (Cervus
elaphus nelsoni). Physiol. Zool. 65: 379-402.
Suttie, J. M., Fennessy, P.
F., VeenVliet, B. A., Littlejohn, R. P., Fisher, M.
W., Corson, I. D., & Labes, R. E. 1987. Energy nutrition of young
Suttie,
J.M. White, R.G., Breier, B.H. & Gluckman, P.D. 1991. Photoperiod-associated changes
in insulin-like growth factor-I in reindeer. Endocrinology 129: 679-682.
Verme, L.J. 1988. Lipogenesis
in buck fawn white-tailed deer: Photoperiod effects.
J. Mammal. 69: 67-70.
Walker, V. A. 1991. Photoperiod influences on the seasonal energy metabolism of
ewes. PhD thesis,
Wairimu,
TABLE 1. FEED ANALYSIS AND TRIAL DATES
| Trial |
Pellets (batch) |
Trial date (Rotas 1,2) |
NDF % |
ADF % |
Lignin % |
Ash % |
Protein % |
Energy (kJ/g) |
| Fall 92 |
Dehy alfalfa (1) 14 Oct 92 |
41 |
26 |
7.3 |
0.3 |
18.20 |
18.1 |
|
| Winter
93 |
Dehy alfalfa (1) 13 Jan 93 |
44 |
27 |
7.4 |
0.3 |
18.96 |
18.1 |
|
| Spring
93 |
Dehy alfalfa (1) 3
Apr 93 |
43 |
24 |
7.8 |
0.4 |
18.53 |
18.1 |
|
| Summer
93 |
Dehy alfalfa (1) 23 Jul 93 |
44 |
28 |
8.3 |
1.0 |
19.29 |
18.1 |
|
| 1
Aug 93 |
50 |
37 |
8.8 |
0.3 |
18.92 |
17.9 |
||
| Fall 93 |
Dehy alfalfa (2) 9 Oct 93 |
38 |
23 |
5.8 |
0.6 |
18.92 |
17.9 |
|
FIGURES
Fig. 1. Chromium excretion curves. 5
Fig. 2 a. Growth curves of experimental wapiti hinds from weaning to 2 years of
age. Richards equation for growth (shown) accounted
for about 89% of variation. b. Weights of animals at the beginning of seasonal
trials in Experiment 1 (Fall 92-Fall 93) and
Experiment 2 (Win 94-Spr 94). 8
Fig. 3. Average daily gains (kg/d) of animals on ad libitum
and restricted levels of feeding during a two-week period before seasonal
balance trials. 9
Fig. 4. Dry matter intakes (g/W0.75) of wapiti fed ad libitum or restricted to estimated maintenance levels. 10
Fig. 5. Digestibility coefficients of alfalfa dehy
pellets (Fall 92 - Fall 93) and alfalfa-barley pellets
(Win 94). 10
Fig. 6. Total tract turnover times (h) of digesta.
11
Fig. 7. Feed conversion efficiencies (gain (kg)/dry matter intake (kg)).
11
Fig. 8.` Regression of energy intake on average daily gain showing separate
relationships between wapiti on restricted and ad libitum
feeding 12
Fig. 9. Energy requirements for maintenance (kJ/W0.75.d).
13
Fig. 10 Plasma prolactin (ug/l)
of four animals in selected trials. 15
Fig. 11. Plasma thyrotropin
(sTSH) of four animals in selected trials. 15
Fig. 12. Estimation of maintenance requirements of
lactating and dry hinds. 16
Fig 1
Fig. 1. Chromium excretion curve.
Fig 2a,b
Fig. 2 a. Growth curves of experimental wapiti hinds from weaning to 2
years of age. Richards equation for growth (shown)
accounted for about 89% of variation. b. Weights of animals at the
beginning of seasonal trials in Experiment 1 (Fall
92-Fall 93) and Experiment 2 (Win 94-Spr 94).
Fig 3
Fig. 3. Average daily gains (kg/d) of animals on ad libitum and restricted levels of feeding during a
two-week period before seasonal balance trials.
Fig 4
Fig. 4. Dry matter intakes (g/W0.75) of wapiti fed ad libitum or restricted to estimated maintenance levels.
Fig 5
Fig. 5. Digestibility coefficients of alfalfa dehy
pellets (Fall 92 - Fall 93) and alfalfa-barley pellets
(Win 94).
Fig 6
Fig. 6. Total tract turnover times (h) of digesta.
Fig 7
Fig. 7. Feed conversion efficiencies (gain (kg)/dry matter intake (kg)).
Fig 8
Fig. 8. Regression of energy intake and average daily
gain showing separate relationships between wapiti on restricted and ad libitum feeding.
Fig 9
Fig. 9. Energy requirements for liveweight
maintenance (kJ/W0.75.d).
Fig 10
Fig. 10. Plasma prolactin (ug/L) of four animals in selected trials.
Fig 11
Fig. 11. Plasma thyrotropin
(sTSH, mU/L) of four
animals in selected trials.
Fig 12
Fig. 12. Estimation of maintenance requirements of
lactating and dry hinds.