Daily changes in food availability, but not long-term unpredictability, determine daily torpor-bout occurrences and frequency in stripe-faced dunnarts (Sminthopsis macroura)

2015 ◽  
Vol 63 (1) ◽  
pp. 12 ◽  
Author(s):  
Alexandra M. Leslie ◽  
Mathew Stewart ◽  
Elizabeth Price ◽  
Adam J. Munn
Keyword(s):  
Food Availability ◽  
Control Period ◽  
Daily Torpor ◽  
Torpor Bout ◽  
Effect Of Food ◽  
Rapid Adjustment ◽  
Sminthopsis Macroura ◽  
Ad Libitum ◽  
Ad Libitum Intake ◽  
Ad Libitum Feeding

Daily torpor, a short-term reduction in body temperature and metabolism, is an energy-saving strategy that has been interpreted as an adaptation to unpredictable resource availability. However, the effect of food-supply variability on torpor, separately from consistent food restriction, remains largely unexamined. In this study, we investigated the effect of unpredictable food availability on torpor in stripe-faced dunnarts (Sminthopsis macroura). After a control period of ad libitum feeding, dunnarts were offered 65% of their average daily ad libitum intake over 31 days, either as a constant restriction (i.e. as equal amount of food offered each day) or as an unpredictable schedule of feed offered, varied daily as 0%, 30%, 60%, 100% or 130% of ad libitum. Both feeding groups had increased torpor-bout occurrences (as a proportion of all dunnarts on a given day) and torpor-bout frequency (average number of bouts each day) when on a restricted diet compared with ad libitum feeding, but torpor frequency did not differ between the consistently restricted and unpredictably restricted groups. Most importantly, torpor occurrence and daily bout frequency by the unpredictably restricted group appeared to change in direct association with the amount of food offered on each day; torpor frequency was higher on days of low food availability. Our data do not support the interpretation that torpor is a response to unpredictable food availability per se, but rather that torpor allowed a rapid adjustment of energy expenditure to manage daily fluctuations in food availability.

Effect of food manipulation on the GnRH-LH-estradiol axis of young female rats

1988 ◽  
Vol 254 (4) ◽  
pp. R616-R621 ◽  
Author(s):  
F. H. Bronson
Keyword(s):  
Food Restriction ◽  
Dark Period ◽  
Pubertal Development ◽  
Young Female ◽  
Female Rats ◽  
The Third ◽  
Feedback Sensitivity ◽  
Effect Of Food ◽  
Ad Libitum ◽  
Ad Libitum Feeding

Female rats were prevented from growing and developing reproductively by restricting their food intake from the time they reached 80-85 g (27-29 days of age) until they were 2 mo old. A return to ad libitum feeding then typically yielded the pubertal ovulation during the third or fourth dark period. Ad libitum feeding for 48 h increased the frequency of luteinizing hormone (LH) pulsing in ovariectomized females. This treatment also depressed the level of circulating estradiol in ovariectomized females implanted with Silastic capsules. It had no effect on the rate at which estradiol was cleared from the blood in a 1-h test, however, nor did it affect the pool of assayable gonadotropin-releasing hormone (GnRH) in the hypothalamus, the pool of assayable LH in the pituitary, the response of the pituitary to GnRH, or the rate at which LH was cleared from the blood. In toto, the present results suggest that food restriction inhibits pubertal development by acting rather specifically on GnRH secretion via an ovarian steroid-independent pathway. The presumed supplemental role for enhanced negative-feedback sensitivity could not be evaluated because of the aberrant results with encapsulated estradiol.

The digestion of chopped and ground roughages by sheep. I. Movement of digesta through the stomach

1967 ◽  
Vol 18 (5) ◽  
pp. 789 ◽  
Author(s):  
RH Weston ◽  
JP Hogan
Keyword(s):  
Retention Time ◽  
Metabolizable Energy ◽  
Water Soluble ◽  
Ad Libitum ◽  
Ad Libitum Intake ◽  
Ad Libitum Feeding

Digestion studies were conducted with lucerne hay and wheaten hay prepared for feeding either by chopping or by grinding and pelleting. The sheep were offered food every 3 hr. The rates of flow of water and the rumen volumes were measured by reference to a water-soluble marker. The replacement of a diet of chopped roughage by an equal amount of ground roughage caused a decline in the rate of flow of water from the rumen. With wheaten hay this decreased flow was accompanied by a decline in rumen volume, the retention time of the marker in the rumen remaining constant; with lucerne hay the rumen volume remained constant and the retention time of the marker increased. When the quantity of ground roughage feed was increased, rates of flow from the rumen and abomasum were enhanced and marker retention time in the rumen decreased. Under conditions of ad libitum feeding, the sheep consumed 75% more chopped lucerne hay than chopped wheaten hay; grinding was accompanied by an increase of 50% in the consumption of each hay. When levels of feeding were approximately 90% of the ad libitum intake, it was found that: (i) the rate of flow from the rumen appeared to be independent of diet and method of preparation of the feed; (ii) the rate of flow from the abomasum was higher with the ground roughage; (iii) rumen volume with ground lucerne hay was higher than with chopped lucerne hay or ground wheaten hay; it was also higher with chopped wheaten hay as compared with ground wheaten hay. Sheep spent less time ruminating and eating when the roughages were ground. The amount of metabolizable energy available for production from 1000 g of ground lucerne hay was 950 kcal; it was calculated that this would have declined by 9% if the sheep ruminated for the same time on this ground hay as on the chopped hay.

Skin folds and Merino breeding. 9. Efficiency of conversion of food to wool

1976 ◽  
Vol 16 (80) ◽  
pp. 361 ◽  
Author(s):  
GE Robards ◽  
CH Davis ◽  
DG Saville
Keyword(s):  
Surface Area ◽  
The Other ◽  
Or Efficiency ◽  
Wool Production ◽  
Skin Fold ◽  
Significant Difference ◽  
Ad Libitum ◽  
Ad Libitum Intake ◽  
Ad Libitum Feeding ◽  
Reduced Surface

This paper reports a study of the efficiency of wool production, liveweight change and ad libitum intake of 60 hogget ewes from flocks selected for 15 years for skin wrinkle (Folds Plus), against skin wrinkle (Folds Minus) and randomly selected as a control (Random). Initially, under restricted feeding ewes from each genetic flock consumed 594, 750, 951 or 1097 g DM day-1 of a lucerne pellet ration. The mean efficiency of clean wool production of Folds Minus ewes (8.47 g CW/kg D.M.I.) was less (P < 0.05) than that of either Random (9.38) or Folds Plus (10.18) ewes, which did not differ significantly. During the following ad libitum feeding period, the Folds Minus ewes again produced less wool than either of the other groups and their wool production was less efficient even though they consumed significantly less feed than either Random or Folds Plus ewes. The significant difference in intake between Random and Folds Minus ewes remained when the n takes were corrected for liveweight (kg), metabolic body size (kg0.73) or surface area based on liveweight alone (kg0.67). However, when fold score (FS) was included in the surface area estimate as LW0.67 + FS0.2 the intake difference between flocks became very small. The experimental results and components analyses of the pre- and post-shearing data showed that selection for skin fold had not changed wool growth rate or efficiency of wool production, but had reduced staple length. On the other hand, the lower wool production of Folds Minus ewes was due to both reduced surface area and lower wool production per unit area.

Food and Growth of Fishes. II. Effects of Food and Temperature on the Relation Between Metabolism and Body Weight

1966 ◽  
Vol 23 (6) ◽  
pp. 869-908 ◽  
Author(s):  
J. E. Paloheimo ◽  
L. M. Dickie
Keyword(s):  
Body Weight ◽  
Oxygen Consumption ◽  
Body Size ◽  
Food Availability ◽  
Metabolic Parameters ◽  
Basic Relation ◽  
Metabolic Adaptation ◽  
Feeding Experiments ◽  
Ad Libitum ◽  
Ad Libitum Feeding

In an earlier paper we described the growth of fishes, ΔW/Δt, in relation to the experimentally measurable variables, body weight (W), food intake (R), and total metabolism (T). Here we review experimental evidence of the nature of the relation between T and W, and its dependence on R and temperature. Making use of the basic energy equation, pR = T + ΔW/Δt, where p is the term for correction from injested to utilizable energy, we calculate T as the difference between the energy equivalents of R and ΔW/Δt, for comparison with results of oxygen consumption studies. Application to a number of published experimental results suggests that with constant food availability, this index of total metabolism, T, derived from feeding experiments, shows the same rate of change with body weight, W, as has been found by oxygen consumption studies under standard conditions. That is, the two sources of data provide estimates of a common γ in the relation[Formula: see text]where α and γ are the fitted parameters for the curve.When fish are fed on a "maintenance" diet, the value of α calculated from the food-growth difference (the growth change is rarely nil in a given experimental observation period), appears to correspond with that characterizing the "routine" metabolic level in oxygen consumption studies. Higher α levels result from higher levels of food availability, and at ad libitum feeding α appears to approach the levels known in oxygen consumption studies as "active" metabolic levels. Temperature effects in the experiments were estimated from multiple regression analyses and showed an elevation of α with increasing temperature. The long-term effect of temperature on α was comparable with that predicted by the Krogh correction at ad libitum feeding, but was significantly lower when food was limited, as at "maintenance" feeding.From a survey of effects of different designs of feeding experiments on these metabolic parameters, it appeared that apparently aberrant values of the weight exponent γ may instead be mistaken interpretations of changes in the level of metabolism α. That is, within the limiting conditions of standard or active metabolism, changes in temperature during experiments or manipulations of the availability of food by the experimenter, sometimes unintentionally, elicit adaptative responses in the level of metabolism, α. These show up in the results as effects on γ when the changes in conditions are gradual, hence confounded with body-size changes during growth.The ability to make distinctions between effects of various factors on these two metabolic parameters appears to depend upon a distinction between experiments conducted with a view to learning what fish do under particular circumstances, and experiments designed to explore what fish are capable of doing. The former type reveal a remarkable conservatism in the basic relation between metabolism and body size, γ. Results from the latter reflect possibilities of metabolic adaptation to environmental circumstances. The apparent predictability of the response of the total metabolism to various conditions of food energy supply and dissipation suggests that the remainder of the energy system, represented by the growth, may be similarly predictable. If this is true outside the laboratory, measurements of the metabolic parameters, α and γ, already familiar in physiological and behavioural research, could be directly used as indices of the (relative) positions of various sizes and species of fish in natural production systems.

Ethane production rate in vivo is reduced with dietary restriction

1990 ◽  
Vol 68 (6) ◽  
pp. 2588-2590 ◽  
Author(s):  
M. P. Habib ◽  
F. Dickerson ◽  
A. D. Mooradian
Keyword(s):  
Production Rate ◽  
Dietary Restriction ◽  
Food Restriction ◽  
Age Related ◽  
Ethane Production ◽  
Effect Of Food ◽  
Ad Libitum ◽  
Ad Libitum Feeding ◽  
Food Consumed

Dietary restriction without malnutrition prolongs life and has a beneficial effect on age-related diseases and metabolic derangements. To test the effect of food restriction on ethane production rate, ethane exhalation was measured in rats with partial food restriction. Ethane production rate in room air in rats fed 60% of food consumed by ad libitum-fed animals for 2 wk was significantly reduced (3.50 +/- 0.25 vs. 5.21 +/- 0.34 pmol.min-1.100 g body wt-1, P less than 0.01). In 100% oxygen, ethane production in food-restricted rats was not different from that of ad libitum-fed rats (21.81 +/- 1.25 vs. 19.57 +/- 1.89 pmol.min-1.100 g-1). Fifteen hours of fasting compared with ad libitum feeding reduced ethane production modestly in room air (4.37 +/- 0.45 vs. 5.21 +/- 0.34 pmol.min-1.100 g-1) and more significantly in 100% oxygen (12.37 +/- 0.78 vs. 19.57 +/- 1.89 pmol.min-1.100 g-1). Thus, in 100% oxygen, 15 h of fasting, compared with ad libitum feeding, resulted in an approximately 40% decrease in ethane production rate. It is concluded that short-term food restriction significantly reduces ethane exhalation rate in rats when measured in room air.

Effects of restricted and ad libitum intake of diets containing wheat middlings on site and extent of digestion in steers

2002 ◽  
Vol 80 (3) ◽  
pp. 812-817 ◽  
Author(s):  
G. N. Hermesmeyer ◽  
L. L. Berger ◽  
N. R. Merchen ◽  
T. G. Nash
Keyword(s):  
Wheat Middlings ◽  
Ad Libitum ◽  
Ad Libitum Intake

Selection for components of efficient lean growth rate in pigs 2. Selection pressure applied and direct responses in a Landrace herd

1994 ◽  
Vol 59 (2) ◽  
pp. 263-269 ◽  
Author(s):  
N. D. Cameron ◽  
M. K. Curran
Keyword(s):  
Growth Rate ◽  
Genetic Correlations ◽  
Correlated Response ◽  
Selection Line ◽  
Control Line ◽  
Direct Response ◽  
Lean Growth ◽  
Ad Libitum ◽  
Selection For ◽  
Ad Libitum Feeding

AbstractResponses to divergent selection for lean growth rate with ad-libitum feeding (LGA), for lean food conversion (LFC) and for daily food intake (DFI) in Landrace pigs were studied. Selection was practised for four generations with a generation interval ofl year. A total of 2642 pigs were performance tested in the high, low and control lines, with an average of 37 boars and 39 gilts performance tested per selection line in each generation. The average within-line inbreeding coefficient at generation four was equal to 0·04. There was one control line for the DFI and LFC selection groups and another control line for the LGA selection group. Animals were performance tested in individual pens with mean starting and finishing weights of 30 kg and 85 kg respectively with ad-libitum feeding. The selection criteria had phenotypic s.d. of 32, 29 and 274 units, for LGA, LFC and DFI, respectively, and results are presented in phenotypic s.d.Cumulative selection differentials (CSD) were 5·1, 4·5 and 5·5 phenotypic s.d. for LGA, LFC and DFI, respectively. Direct responses to selection were 1·4,1·1 and 0·9 (s.e. 0·20) for LGA, LFC and DFI. In each of the three selection groups, the CSD and direct responses to selection were symmetric about the control lines. The correlated response in LFC (1·1, s.e. 0·19) with selection on LGA was equal to the direct response in LFC. In contrast, the direct response in LGA was greater than the correlated response (0·7, s.e. 0·18) with selection on LFC. There was a negative correlated response in DFI (-0·6, s.e. 0·18) with selection on LFC, but the response with selection on LGA was not significant (0·2, s.e. 0·16).Heritabilities for LGA, LFC and DFI ivere 0·25, 0·25 and 0·18 (s.e. 0·03), when estimated by residual maximum likelihood, with common environmental effects of 0·12 (s.e. 0·02). Genetic correlations for LFC with LGA and DFI were respectively positive (0·87, s.e. 0·02) and negative (-0·36, s.e. 0·09), while the genetic correlation between DFI and LGA was not statistically different from zero, 0·13 (s.e. 0·10). Selection on components of efficient lean growth has identified LGA as an effective selection objective for improving both LGA and LFC, without a reduction in DFI.

Factors limiting the intake of feed by sheep. I. The significance of palatability, the capacity of the alimentary tract to handle digesta, and the supply of glucogenic substrate.

1966 ◽  
Vol 17 (6) ◽  
pp. 939 ◽  
Author(s):  
RH Weston
Keyword(s):  
Acetic Acid ◽  
Propionic Acid ◽  
Polyvinyl Chloride ◽  
Dry Matter ◽  
Alimentary Tract ◽  
Control Period ◽  
Feed Consumption ◽  
Ad Libitum

Voluntary feed consumption (VFC) decreased when a quantity of the diet being consumed by the sheep was introduced into the rumen. On diets of lucerne hay, lucerne hay plus maize, wheaten hay, and wheaten straw, the decreases in VFC ranged from 90 to 110% of the quantity introduced intraruminally when this quantity varied from 20 to 60% of the VFC during control periods. When sheep consumed wheaten straw ad libitum, and a quantity of coarsely ground wheaten straw equal to 140% of the VFC during a control period was given intraruminally, VFC ceased and digesta accumulated in the rumen. VFC decreased when indigestible materials were introduced into the rumen. The voluntary consumption of lucerne hay decreased by 15% when sawdust was introduced into the rumen at a rate equivalent by weight to 17% of the VFC during a control period ; decreases of 7 and 9% were found when finely ground polyvinyl chloride was introduced at rates equivalent by weight to 25 and 50% respectively of VFC during control periods. The voluntary consumption of wheaten hay decreased by 16 and 19% when sawdust was introduced into the rumen at rates equivalent by weight to 25 and 18% respectively of VFC during control periods. Intraruminal infusions of acetic acid, propionic acid, or a mixture of acetic, propionic, and butyric acids providing 290–510 kcal of energy daily were accompanied by decreases in the voluntary consumption of lucerne hay and wheaten hay; the decreases ranged from 0.29 to 0.86 g dry matter per kcal of energy infused; similar decreases were obtained when propionic acid was infused into the abomasum of sheep given lucerne hay. The intake of lucerne hay was 9% higher when given alone than when supplemented with 6% propionic acid. The results are discussed in relation to factors limiting the intake of lucerne hay and wheaten hay.

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