Voluntary Food Intake Research Articles

Food consumption and growth in maturing Atlantic salmon (Salmo salar)

Circulating levels of the steroid hormones 11-ketotestosterone (11-KT) and 17β-estradiol (E2), voluntary food intake, and growth performance were measured in individual Atlantic salmon (Salmo salar) over the year preceding their maturation as grilse. 11-KT and E2 were measured by radioimmunoassay, and X-radiography was used to measure food consumption rates. Two phases of sexual maturation were identified: the early phase (October 1992 - April 1993) was characterized by slowly rising steroid hormone levels concomitant with relatively high rates of food consumption and growth, and in the late phase (May-October 1993), steroid hormone levels increased more rapidly and growth rates decreased in association with inappetence. Significant linear relationships were observed between food consumption and specific growth rates of fish throughout the study (ANCOVA, p < 0.05). Slopes and intercepts of regressions were similar for fish during early maturation, while a lower intercept and steeper slope (ANCOVA, p < 0.05) was observed during the later stages of maturation. In November, January, February, and April, fish in which steroid hormone levels were elevated were significantly heavier than those in which hormone levels were basal. There were no significant differences in specific growth rates (except in February), food consumption, or weight-specific food conversion ratio (except in August and October) associated with maturation status.

Control of food intake by fatty acid oxidation and ketogenesis.

Fatty acid oxidation seems to provide an important stimulus for metabolic control of food intake, because various inhibitors of fatty acid oxidation (mercaptoacetate, methyl palmoxirate, R-3-amino-4-trimethylaminobutyric acid) stimulated feeding in rats and/or mice, in particular when fed a fat-enriched diet, and long-term intravascular infusion of lipids reduced voluntary food intake in various species, including humans. The feeding response to decreased fatty acid oxidation was due to a shortening of the intermeal interval with meal size remaining unaffected. Thus, energy derived from fatty acid oxidation seems to contribute to control of the duration of postmeal satiety and meal onset. Since inhibition of glucose metabolism by 2-deoxy-D-glucose affects feeding pattern similarly, and spontaneous meals were shown to be preceded by a transient decline in blood glucose in rats and humans, a decrease in energy availability from glucose and fatty acid oxidation seems to be instrumental in eliciting eating. Since the feeding response of rats to inhibition of fatty acid oxidation was abolished by total abdominal vagotomy and pretreatment with capsaicin destroying non-myelinated afferents and attenuated by hepatic branch vagotomy, fatty acid oxidation in abdominal tissues, especially in the liver, apparently is signalled to the brain by vagal afferents to affect eating. Brain lesions and Fos immunohistochemistry were employed to identify pathways within the brain mediating eating in response to decreased fatty acid oxidation. According to these studies, the nucleus tractus solitarii (NTS) of the medulla oblongata represents the gate for central processing of vagally mediated afferent information related to fatty acid oxidation. The lateral parabrachial nucleus of the pons seems to be a major relay for pertinent ascending input from the NTS. In particular the central nucleus of the amygdala, a projection area of the parabrachial nucleus, appears to be crucial for eating in response to decreased fatty acid oxidation. As ketones are products of hepatic fatty acid oxidation that are released into the circulation and peripheral (and central) administration of 3-hydroxybutyrate reduced voluntary food intake in rats, ketones being utilized as fuels by the peripheral and central nervous system might contribute to control of eating by fatty acid oxidation, especially when high levels of circulating ketones occur. Whether a modulation of the hepatic membrane potential resulting from changes in the rate of fatty acid oxidation and/or ketogenesis represent a signal for control of eating transmitted to the brain by vagal afferents remains to be established. Recent in vivo studies investigating the effects of mercaptoacetate on the hepatic membrane potential and on afferent activity of the hepatic vagus branch are consistent with this notion. Further investigations are necessary to delineate the coding mechanisms by which fatty acid oxidation and/or ketogenesis modulate vagal afferent activity.

Menstrual Cycle and Voluntary Food Intake in Young Chinese Women

The effect of menstrual cycle phase on energy and macronutrients intakes was assessed in 20 university students (21·2±1·3 years) all of whom experienced ovulatory cycle as documented by a surge in urinary luteinizing hormone. Three-day food intake records, which consisted of one weekend day, were kept in both mid-follicular and mid-luteal phases. Mean daily energy intake was higher (p=0·02) in the luteal phase (6978±1847 kJ) than in the follicular phase (6095±1174 kJ). Intakes of carbohydrate and fat were also significantly elevated (by 15 and 21%, respectively) in the luteal phase. The menstrual phase effect on energy intake was attributed to the substantially higher intakes from Thursday through Sunday in the luteal phase. The proportion of energy from the three macronutrients was not affected by menstrual phase nor day of the week.

Seasonal changes of metabolism and appetite in Soay rams

Abstract Relationships between photoperiod and cycles of voluntary food intake (VFI) and maintenance energy requirements (MER) were determined in Soay rams, subjected to a 6-month photoperiodic regime. Food was offered ad libitum (no. = 5) or at a predicted maintenance level (no. = 5). All rams demonstrated 6-month cycles of VFI, growth and reproductive status. Metabolizable energy intake (MEI) was greatest in rams given food ad libitum (666 (s.e. 21.7) kJ/kg metabolic live weight (M0·75) and food-restricted (528 (s.e. 12.2) kJ/kg M0·75) rams during sexual quiescence. Conversely, MEI was minimal (ad libitum, 289 (s.e. 8.4) kJ/kg M0·75; restricted, 428 (s.e. 8.1) kJ/kg M0·75) during the rut. Distinct cycles of heat production (HP) accompanied changes in MEL Changes in HP were similar (P > 0·05) for both groups (ad libitum, 520 (s.e. 22.1) to 394 (s.e. 9.2) kJ/kg M0·75; restricted 503 (s.e. 14.0) to 407 (s.e. 17.5) kJ/kg M0·75) and therefore energy retention varied more (P < 0·015) when rams were given food ad libitum (ad libitum, 131 (s.e. 43-1) to -106 (s.e. 38.2) kJ/kg M0·75; restricted, 78·0 (s.e. 27.1) to -53.0 (s.e. 38.2) kJ/ kg M0·75). Apparent digestibility of dietary energy varied inversely with MEI (P < 0·01). MERs ranged from 524 (s.e. 35.0) kJ/kg M0·75 to 401 (s.e. 27.3) kJ/kg M0·75, a proportional fluctuation of ±0·13. Changes in metabolic rate preceded those in appetite, suggesting a causal relationship.

Evidence of differences in growth and food intake regulation in different genetic strains of channel catfish

Norris and USDA‐103 strains of channel catfish Ictalurus punctatus were compared for growth rate and food conversion ratio under satiation feeding and restricted feeding (1% body weight day−1) regimes. At the start of the experiment Norris fish weighed 2·8 g, USDA‐103 fish weighed 14·0 g. Therefore, a regression of the loge of specific growth rate against the loge of mean body size with an empirically derived fixed slope of ‐0·37 was used to compare growth rates. Under both feeding regimes the USDA‐103 strain had faster specific growth rates and more efficient food conversion. In subsequent studies, voluntary food intake of size matched fish (60 g average) from these two strains was compared using a radiographic method. Fish were acclimatized to tank conditions for 3 weeks prior to voluntary food intake measurement. Half of the groups were deprived of food for 2 days prior to food intake measurement, while the remaining groups were fed 1% body weight day−1. The USDA‐103 strain fish ate significantly more food and grew faster than the Norris strain fish. Previously fasted Norris fish subsequently ate more than their fed counterparts, whereas the fed USDA‐103 fish consumed more food than the fasted USDA‐103 group. When the USDA‐103 strain fish were deprived of food for 4, 2 or 0 days, all groups subsequently consumed between 4·5 and 5·0% of body weight in one meal. The USDA‐103 fish, unlike the Norris fish were not stimulated to consume more after short‐duration fasting. Taken together, these results suggest that there are genetic differences in growth, food conversion ratio and regulation of food intake between Norris and USDA‐103 strains.

Voluntary intake responses of ‘White’ and Meishan cross growing pigs to nutrient dilution

Selection for efficiency of lean growth has lead to a marked reduction in fat gain and voluntary food intake (VFI) of modern genotypes. There is concern that future improvements in lean growth rate may be limited by appetite. Moreover, the ability of lean genotypes to adjust their VFI in response to variations in nutrient density is not well known. Such genotypes may fail to compensate their intake in response to marginal reductions in nutrient density, which could affect growth performance. The aim was to evaluate the VFI and growth performance of ‘White’ and Meishan cross growing pigs in response to incremental reductions in dietary energy content.

Glycated cholecystokinin-8 has an enhanced satiating activity and is protected against enzymatic degradation.

Monoglycated cholecystokinin octapeptide (CCK-8) (glucitol-Asp1 adduct) modified at the NH2-terminus was prepared under hyperglycemic conditions, purified by high-performance liquid chromatography, and characterized by mass spectrometry (Mr 1228.4 Da) and peptide sequencing. CCK-8 (100 nmol/kg, i.p.) significantly (P < 0.001) reduced voluntary food intake of fasted mice for up to 30 min after its administration, compared with saline-administered controls. Glycated CCK-8 reduced food intake at 30-120 min (P < 0.01 to P < 0.001) and significantly reduced feeding compared with CCK-8 from 60 to 120 min (P < 0.01). In vitro plasma degradation studies indicated that glycated CCK-8 was resistant to the normal rapid enzymatic conversion to CCK fragments. This study demonstrated that CCK-8 is a potent short-term inhibitor of food intake, and that structural modification of this peptide by amino-terminal glycation leads to enhanced satiating activity, partially due to increased resistance to serum aminopeptidase degradation.

Independent effects of food intake and insulin status on insulin-like growth factor-I in young pigs

The independent effects of decreased food intake and diabetic hyperglycemia on serum GH, serum IGF-I and tissue IGF-I expression were examined in young streptozotocin-diabetic pigs. Each of three treatments (control, diabetic, and insulin-treated diabetic) were represented within three levels of regulated food intake (FI) provided as three meals per day equivalent to 100, 50, and 10% of the voluntary FI consumed by the untreated diabetics. Reduction of food intake was associated with decreased body weight gains, decreased serum IGF-I concentrations, and increased serum GH concentrations. Nutrient restriction also tended to decrease the relative abundance of IGF-I mRNA in liver and skeletal muscle. Diabetic pigs with hyperglycemia and hypoinsulinemia had higher serum concentrations of IGF-I than pair-fed controls, but exogenous insulin treatment of these diabetic pigs increased serum IGF-I even further and also tended to increase the relative abundance of IGF-I mRNA in liver and skeletal muscle. When the statistical effects of reduced FI were eliminated, neither the present form of diabetes nor exogenous insulin affected serum GH. In summary, diabetes-induced changes in IGF-I in these pigs depended primarily on the reduced level of food intake occurring in these hypoinsulinemic, hyperglycemic subjects.

Effects of restricted ration, time-restricted access and reward level on voluntary food intake, growth and growth heterogeneity of rainbow trout ( Oncorhynchus mykiss) fed on demand with self-feeders

Growth responses of rainbow trout fed on demand using self-feeders were tested over an 8 week period when triplicate groups were exposed to two feeding levels (unlimited and fixed ration), at two feeding frequencies (time-restricted and free access) and three reward levels (0.17 g, 0.30 g and 0.43 g per trigger actuation). Triplicate groups were also hand fed as control of maximum growth. Each fish was marked according to its weight-class, and each group of 26 fish comprised a predetermined number of fish per weight-class: two fish of 13–16 g, six fish of 16–19 g, 10 fish of 19–22 g, six fish of 22–25 g and two fish of 25–28 g. There was no significant effect of feeding regime on feed efficiency. Voluntary feed intake and specific growth rates were significantly decreased as fish were exposed to reduced reward levels, even though there was a negative relationship between reward level and daily demand. Time-restricted access to self-feeders led to a decrease in feed intake, and an increase in growth heterogeneity in comparison with free access to self-feeders. Voluntary feed intake and specific growth rates were always lower in self-fed groups than in groups fed to apparent satiation by hand. Individual growth heterogeneity was greater within tanks allowed time-restricted access to self-feeders and within tanks fed by hand to visual satiation than within those given continuous access to self feeders. It is suggested that rainbow trout fed on demand with self feeders may not ingest as much food as they would be able to, and may not be satiated, but do express their hunger in relation with the level of effort that has to be done to obtain food.

Differential effects of feeding fermentable carbohydrate to growing pigs on performance, gut size and slaughter characteristics

AbstractThirty-five gilts grown between 18 and 55 kg live weight were used to examine the effects of feeding fermentable carbohydrate on voluntary food intake, performance, carcass characteristics, and large intestinal growth. Five diets were used. The first diet contained steam-flaked sorghum and a supplement based on animal protein sources and 40 g/kg soya-bean meal (diet SAP). Using this diet as a base, three other diets contained either (i) guar gum, a source of soluble non-starch polysaccharide (NSP) (diet SAP + S-NSP), (ii) Novelose™, a source of resistant starch (RS) (diet SAP + RS), and (Hi) a combination of both S-NSP and RS (diet SAP + S-NSP + RS). The final diet (diet WBL) was based on wheat, barley and Australian sweet lupins. Diets (i), (ii) and (Hi) were formulated such that the concentrations of soluble NSP, oligosaccharide and RS were similar to those contained in diet WBL. There was no relationship (F &gt; 0·05) between voluntary food intake and indices of hind-gut fermentation, although pigs given diets SAP + S-NSP and SAP + S-NSP + RS took longer to reach the slaughter weight of 55 kg (F &lt; 0·001) and converted food less efficiently than pigs given other diets (F &lt; 0·001). An increased intake of S-NSP (R2 = 0·842, P &lt; 0·05) and S-NSP + RS (R2 = 0·805, F &lt; 0·05) was positively correlated to an increased (empty) weight of the large intestine. A significant negative relationship (R2 = 0·78, F &lt; 0·05) existed between the daily intake of S-NSP + RS and dressing proportion, such that each gram increase caused a 0·25 g/kg decrease in the dressing proportion of pigs. No such relationships existed between the daily intake of soluble NSP, insoluble NSP, or RS (P &gt; 0·05) with dressing proportion. These data suggest that the sources of fermentable carbohydrate used in this study, i.e. soluble NSP and RS, may not significantly depress voluntary food intake but can affect performance and have a significant effect on large intestinal growth and dressing proportion.

Zucker obese rats are insensitive to the CRH-increasing effect of oleoyl-estrone

Adult female Zucker lean and obese rats were treated for 14 days with 3.5 nm/kg oleoyl-estrone (OE) in liposomes (Merlin-2) through continuous i.v. injection with osmotic minipumps. Rat wt. and food intake were measured daily. On days 0, 3, 6, 10, and 14, groups of rats were killed and their hypothalamic nuclei [lateral preoptic (LPO), median preoptic (MPO), paraventricular (PVN), ventromedial (VMH), and arcuate (ARC)] were dissected, homogenized, and used for the measurement of corticosterone-releasing hormone (CRH) by radioimmunoassay. The OE treatment decreased food intake by 67.4% in lean and 62.6% in obese rats (means for 14 days). Body wt. decreased steadily in lean and obese rats, the gap between controls and treated rats becoming 11.5% of initial body wt. in the lean and 12.4% in the obese. The levels of CRH in the ARC nucleus were at least 10-fold higher than in the other nuclei. No changes in CRH were observed in any of the nuclei of obese rats, with levels up to day 6 similar to those of lean rats. In the lean rats, the LPO and ARC nuclei showed peaks on day 10, while the MPO showed no changes and the PVN and VMH nuclei showed a progressive increase, to a maximum at the end of the study (day 14). This contrasted with the peak of plasma adrenocorticotropic hormone (ACTH) and corticosterone (day 6 in lean and day 14 in obese rats). There was a definite lack of correlation between the plasma levels of these two hormones and the levels of CRH in the hypothalamic nuclei, and between the latter and the decreases in appetite in the rats. The loss of appetite induced by OE is not necessarily mediated by CRH, because the obese rats show an intense decrease in voluntary food intake but their hypothalamic nuclei CRH levels do not change at all. Hypothalamic nuclei CRH does not, necessarily, mediate the rise in glucocorticoids induced by OE treatment, because this is observed in lean and obese rats, lean rats increases being mismatched with those of hypothalamic CRH. The OE induced changes in hypothalamic CRH require a fully functional leptinergic pathway, because it is not observed in Zucker fa/fa rats lacking a working leptin receptor. This–indirectly–shows that leptin is needed for its synthesis or modulation.

The influence of molar occlusal surface area on the voluntary intake, digestion, chewing behaviour and diet selection of red deer (Cervus elaphus)

AbstractThe loss of tooth effectiveness due to molar wear has been proposed as an important cause of mortality in ungulate populations. Voluntary intakes, digestibility, mean retention times, chewing behaviour (during eating and rumination), and diet selection (physical selection: short vs long particles in hay; and botanical selection: leaf vs stem) were compared in two groups of female red deer (Cervus elaphus) which differed in molar occlusal surface area, in order to test the hypothesis that behavioural and physiological mechanisms can be used to maintain assimilation efficiency in the presence of low functional tooth effectiveness. The group with lower values for first lower molar occlusal surface area (OSA) corrected for body weight had lower voluntary food intakes (P= 0.0126). The low OSA group had a greater number of chews per g DM of food ingested (P= 0.0167), a greater time spent chewing (P= 0.0476) but a lower number of chews per min than did those with a high OSA (P= 0.0484). The total number of chews per day was similar for both groups (P= 0.2011). The number of ruminating chews per day was less for the low OSA group (P= 0.0377). The group with low OSA values had a larger average particle size in their faeces (P= 0.0346). No differences were detected between groups in the physical or botanical composition of the diet selected (P= 0.3030, P= 0.3056, respectively) or in total digestibility and mean retention times (P= 0.1357, P= 0.3464, respectively). As a consequence of the lower voluntary intake the low OSA group had a lower digestible dry matter intake (P= 0.0170). This study supports the view that intake modification and the time invested in chewing during eating are the main mechanisms used to compensate for reduced chewing effectiveness associated with changes in tooth morphology, although the compensation is not total.

The effect of nutrition during early life on voluntary food intake by lambs between weaning and 2 years of age

AbstractTwo experiments were carried out with Scottish Blackface lambs to investigate the effects of restricted nutrition during pregnancy and lactation on voluntary food intakes (VFI) between weaning and 2 years of age. Ewes were given diets providing 0·7 (LP) or 10 (HP) of their estimated metabolizable energy requirements during the last 6 weeks of pregnancy and subsequently grazed swards with mean sward surface heights of approximately 3 cm (LL) or 6 cm (HL) during lactation. All lambs were weaned at 17 weeks of age. In experiment 1, four treatment combinations (LP-LL, LP-HL, HP-LL and HP-HL) were applied and female lambs were studied. In experiment 2, two treatment combinations (LP-LL and HP-HL) were applied and male lambs were studied. In both experiments the lambs received a common level of nutrition between weaning and 2 years of age.In both experiments, mean live weights were proportionately 0·2 higher for HP-HL than for LP-LL lambs at weaning (P &lt; 0·001) and in experiment 2 mean live weights and body condition scores were still higher in HP-HL than in LP-LL lambs at 2 years of age (P &lt; 0·05). Abomasum weights were higher in HP than in LP lambs at birth and higher in HP-HL than in LP-LL lambs at weaning in experiment 1 and the weights of the rumen and dimensions of the rumen villi were greater in HP-HL than in LP-LL lambs at weaning in both experiments (P &lt; 0·05). The treatments had no effect on lipid content or mean adipocyte diameter in the main fat depots at birth or weaning. There were no treatment effects on VFI in either experiment. It was concluded that restricted nutrition during late pregnancy and early lactation does not affect VFI between weaning and 2 years of age in sheep, even though there are differences in live weight and the development of the gastrointestinal tract at weaning and there may be long-term effects on live weight and body condition, particularly in male animals.

The prediction of the voluntary food intake of pigs on poor quality foods

AbstractAn experiment was carried out to investigate the proposal that the voluntary food intake of pigs, when given foods based on bulky materials, can be accurately predicted from the water-holding capacity (WHC, g water per g dry food) values of the foods. A basal food (B), with 12·9 MJ digestible energy and 249 g crude protein per kg dry matter, was diluted to two extents by either sugar-beet pulp (S), grass meal (G) or soya hulls (H). The contents of the bulky materials in the total diets were either 320 g/kg (foods BS, BG and BH) or 800 g/kg (foods S, G and H). Each of these six foods was givenad libitumto six pigs in period I, which lasted for 21 days, with a further four given B. In period II, which lasted for 14 days and followed period I immediately, the pigs were also given their food ad libitum. Only the 36 pigs from the six ‘bulky“treatments (i.e. on treatments other than B) continued in a change-over design. Two pigs from each of the six ‘bulky’ treatments were allocated to the three foods of the same level of dilution (e.g. the six pigs from BS were changed to BS, BG and BH). Of the ‘bulk’ characteristics measured (crude fibre, acid-detergent fibre, neutral-detergent fibre, apparent digestibility of the organic matter, density and WHC) only WHC accounted sufficiently for the effects of the foods on the voluntary food intake of the pigs. The two methods of centrifugation and filtration that were used for the WHC determination were very highly correlated (r = 0·978), with food B having the lowest value, 3·86 g water per g dry food, and food S having the highest value, 8·48 g water per g dry food, when measured by centrifugation. In both periods the rate of intake was calculated as g/kg live weight per day, scaled intake (SFI). Live-weight gain and food conversion efficiency both decreased significantly (P&lt; 0·001) as B was diluted with S, G and H. For the six ‘bulky’ feeding treatments SFI in the last 14 days of period I was proportional to the reciprocal of the WHC of the foods: SFI (g/kg per day) = 235 (s.e. 6·3). No effects of previous feeding treatment on site were observed in period II as a whole; however, intake initially increased when the food had lower WHC than the one previously offered and decreased when it had higher WHC. It was concluded that: (a) the WHC of a food is a sufficient descriptor of its ‘bulk’ and that it accounts for the effects on the voluntary food intake of pigs; (b) the detailed methods used for measuring WHC need to be standardized; (c) pigs can adapt more rapidly to bulky foods when they have had prior experience of such foods; (d) the length of time needed to observe an intake, which will be characteristic of the bulky food on offer, depends on the prior experience of the pig.

Carbohydrate composition effects on food intake and energy compensation in rats

To determine the effect of both quantity and composition of carbohydrate on voluntary food intake and energy compensation in rats, carbohydrate preloads (corn starch, sucrose, glucose, fructose, glucose + fructose) were given intragastrically (i.g.) at various doses (0.5 – 3.0 g/ 5 ml) and voluntary food intake over the next 14 h was measured. Quantity of all treatments affected voluntary food intake in the first, and over the fourteen hour feeding period, in a linear, dose-dependent manner (p<0.05), except for fructose. Fructose, at all doses, lowered voluntary food intake more than other sugars (p<0.05). With the exception of the fructose treatment, rats compensated for the energy content of the carbohydrate preloads over the 14 h feeding period. These findings suggest that rats make precise adjustments over the day for the energy contained in readily digestible carbohydrate preloads, with the exception of fructose.

Effect of Rumen Fill on Voluntary Food Intake and Pattern of Eating in Holstein Steers

Akingbade, A.A. and Hoveli, F.D.D. 1998. Effect of rumen fill on voluntary food intake and pattern of eating in Holstein steers. J. Appl. Anim. Res., 13: 145–152. The influence of rumen capacity on voluntary food intake and eating pattern were determined using three Holstein steers (683 kg, 744 kg and 850 kg) fitted with large rumen cannulae. They were fed ad libitum on hay (degradation characteristics a = 35.2, b = 0.0397) in a 3x3 change-over Latin square design comprising seven periods of five days each. Periods 1, 3, 5 and 7 were controls while 2, 4 and 6 were treatments during which rumen was totally emptied once daily, and (i) 15% (add), (ii) 25% (remove) or (Hi) 100% (return of the digesta to the rumen). Fresh food was served at 08.30h daily and rumen digesta manipulated at 11.30h Mean hay daily dry matter intake (DMI) during control periods was 9.3kg/d. Addition of 15% digesta significantly decreased (P<0.01) DMI while 25% digesta removal had no (P>0.05) influence. That these observations were not due to digesta manipulation was demonstrated by digesta return treatment, when all emptied digesta was replaced with no significant effect on both intake and eating pattern of the Holstein steers.

The effects of concentrate energy source on silage intake and animal performance with lactating dairy cows offered a range of grass silages

AbstractA partially balanced change-over design experiment was made to examine the effects of concentrate energy source on the voluntary food intake and animal performance of 50 lactating dairy cows offered a diverse range of grass silages. The silages were also offered as the sole diet to 10 dairy cows in a partially balanced change-over design experiment. A total of five silages were prepared. Silages A, B and D and silages C and E were harvested from primary regrowths and secondary regrowths respectively of predominantly perennial ryegrass swards. Herbage was ensiled either pre-wilted or unwilted and either untreated or treated with a bacterial inoculant or formic acid based additives. For silages A, B, C, D and E, dry matter (DM) concentrations were 473, 334, 170, 170 and 256 (s.e. 4·0) g/kg, pH values 4·42, 4·01, 4·88, 4·46 and 3·91 (s.e. 0·059), ammonia-nitrogen (N) concentrations 86, 88, 289, 182 and 135 (s.e. 10·6) glkg total N and in vitro DM apparent digestibilities 0·76, 0·76, 0·75, 0·73 and 0·75 (s.e. 0·009) respectively. When offered as the sole diet DM intakes were 14·1,14·7,10·5,10·1 and 11·5 (s.e. 0·50) kg/day. Five concentrates were formulated to contain similar concentrations of crude protein, effective rumen degradable protein (ERDP), metabolizable energy (ME) and fermentable ME (FME) but using different carbohydrate sources to achieve a wide range of starch concentrations. For the low and high starch concentrates, starch concentrations were 50 and 384 g/kg DM, and acid-detergent fibre concentrations were 128 and 75 g/kg DM respectively. The silages were offeredad libitumsupplemented with 10 kg concentrate per head per day. For silages A, B, C, D and E silage DM intakes were 10·6, 10·5, 8·5, 8·6 and 9·0 (s.e. 0·37) kg/day and milk yields 23·9, 28·1, 26·2, 26·1 and 25·0 (s.e. 0·76) kg/day respectively. Concentrate energy source did not influence (P &gt; 0·05) silage DM intake, diet apparent digestibility or the yields of milk or fat plus protein. For concentrates containing 50, 131, 209, 310 and 384 g starch per kg DM, milk protein concentrations were 32·0, 32·2, 32·5, 33·0 and 33·6 (s.e. 0·13) glkg, milk fat concentrations were 44·5, 43·9, 43·8, 43·3 and 43·1 (s.e. 0·35) glkg and urinary allantoin concentrations 15·2,15·4, 17·0, 1.7·6 and 18·0 mmolll respectively. Increasing starch intake resulted in positive and negative linear relationships for milk protein (P&lt; 0·01, R2 = 0·96) and fat (P&lt; 0·01, R2 = 0·96) concentrations respectively. There were no significant concentrate energy source × silage type interactions on silage intake or yields of milk or fat plus protein (P &gt; 0·05). However there was a concentrate energy source × silage type interaction on milk fat yield (P &gt; 0·05). It is concluded that, with silages of varying fermentation and intake characteristics but similar apparent digestibility, there were no concentrate energy source × silage type interactions on food intake, milk composition or milk yield. Also concentrate energy source had no effect on silage DM intake or milk yield. However increasing starch intake linearly increased milk protein concentration, probably due to increased microbial protein synthesis and decreased milk fat concentration.

Amelioration of the protein metabolic response in spermidine-supplemented trauma rats

Polyamines are biologically active, small, positively charged ubiquitous compounds that play an important role in initiating adaptive changes in cell proliferation, cell growth, and synthesis of proteins and nucleic acids. The potential for exogenous dietary polyamine to significantly contribute to whole-body growth and health has not been explored. This study evaluates the efficacy of feeding a liquid diet supplemented with 0.05% spermidine in injured rats. Rats traumatized by bilateral femur fracture (n = 12) and pair-fed uninjured controls (n = 12) were starved for 2 days and then refed for 4 days with a liquid diet containing 0.05% spermidine or an isonitrogenous control diet. Daily urine and body weight data were collected. At the end of refeeding, the rats were killed, and blood, cerebrospinal fluid (CSF), muscle, and brain tissue were collected. Spermidine supplementation (0.05%) was found to be tolerated well by the rats and (1) did not affect voluntary food intake by traumatized rats, (2) did not alter the growth rate, (3) increased protein utilization efficiency, and (4) decreased leucine, isoleucine, and valine levels in plasma and muscle. The profound effect of trauma on plasma amino acid metabolism seen in rats fed the basal diet was absent in spermidine-supplemented rats. Depletion of plasma glutamine (GLN) levels due to trauma was significantly less in rats with spermidine supplementation (11% v 33%), indicating a beneficial effect to counteract trauma responses. The results suggest that spermidine supplementation improves protein utilization efficiency and ameliorates trauma effects on amino acid levels.

Photoperiodic entrainment of seasonal changes in appetite and growth in pony colts

During winter, voluntary food intake (VFI) and growth decreased in light horse weanlings given ad libitum access to a forage/concentrate diet (Cymbaluk et al, 1989). These changes were attributed to decreased ambient temperatures. However, photoperiodically entrained seasonal changes in VFI and growth are documented in other Northern ungulates (Moen, 1978) and may comprise an adaptation to changes in forage availability. Throughout their evolution, horses experienced similar environmental pressures and may demonstrate similar photoperiodic adaptations. This study characterised changes in VFI and growth in pony colts maintained under an artificial photoperiodic regime.Seven, 2 year-old pony colts of Welsh Mountain type (182.4 ± 5.4 kg), were obtained from pasture (53°N). Animals were individually housed in loose-boxes, within a light-proof building. Measured quantities of a complete pelleted diet (gross energy = 16.7 MJ.kgDM-1), calculated to exceed appetite by at least 1 kg, were offered daily.

Photoperiodic entrainment of seasonal changes in appetite and growth in pony colts

During winter, voluntary food intake (VFI) and growth decreased in light horse weanlings given ad libitum access to a forage/concentrate diet (Cymbaluk et al, 1989). These changes were attributed to decreased ambient temperatures. However, photoperiodically entrained seasonal changes in VFI and growth are documented in other Northern ungulates (Moen, 1978) and may comprise an adaptation to changes in forage availability. Throughout their evolution, horses experienced similar environmental pressures and may demonstrate similar photoperiodic adaptations. This study characterised changes in VFI and growth in pony colts maintained under an artificial photoperiodic regime.Seven, 2 year-old pony colts of Welsh Mountain type (182.4 ± 5.4 kg), were obtained from pasture (53°N). Animals were individually housed in loose-boxes, within a light-proof building. Measured quantities of a complete pelleted diet (gross energy = 16.7 MJ.kgDM-1), calculated to exceed appetite by at least 1 kg, were offered daily.