The hypothesis that consumption of whey protein (WP) prior to a meal suppresses short-term food intake and reduces post-meal glycemia by insulin-dependent and -independent mechanisms in healthy young adults was explored in three studies. Study one investigated the effect of solid vs. liquid forms of WP (50 g) and sucrose (75 g) on food intake at 1 h. Whey protein, whether in solid or liquid form, suppressed food intake more than sucrose. Study two examined the effect of WP (10-40 g) consumed 30 min prior to a meal on food intake, and pre- and post-meal blood concentrations of glucose and insulin. Whey protein reduced food intake and post-meal glycemia in a dose-dependent manner without increased blood insulin concentrations. In the third study, glycemic control after WP was compared with glucose, at doses of 10 and 20 g. Both pre-meal WP and glucose consumption reduced post-meal glycemia similarly. However, WP resulted in lower pre-meal blood glucose and delayed gastric emptying, lower pre-and post-meal and overall insulin secretion and concentrations and higher GLP-1 and PYY concentrations compared with glucose. Thus, the results of this research support the hypothesis that consumption of WP prior to a meal suppresses short-term food intake and reduces post-meal glycemia by insulin-dependent and -independent mechanisms in healthy young adults.

The hypothesis that consumption of whey protein (WP) prior to a meal suppresses short-term food intake and reduces post-meal glycemia by insulin-dependent and -independent mechanisms in healthy young adults was explored in three studies. Study one investigated the effect of solid vs. liquid forms of WP (50 g) and sucrose (75 g) on food intake at 1 h. Whey protein, whether in solid or liquid form, suppressed food intake more than sucrose. Study two examined the effect of WP (10-40 g) consumed 30 min prior to a meal on food intake, and pre- and post-meal blood concentrations of glucose and insulin. Whey protein reduced food intake and post-meal glycemia in a dose-dependent manner without increased blood insulin concentrations. In the third study, glycemic control after WP was compared with glucose, at doses of 10 and 20 g. Both pre-meal WP and glucose consumption reduced post-meal glycemia similarly. However, WP resulted in lower pre-meal blood glucose and delayed gastric emptying, lower pre-and post-meal and overall insulin secretion and concentrations and higher GLP-1 and PYY concentrations compared with glucose. Thus, the results of this research support the hypothesis that consumption of WP prior to a meal suppresses short-term food intake and reduces post-meal glycemia by insulin-dependent and -independent mechanisms in healthy young adults.

Thesis (M.A. (Human Movement Science))--North-West University, Potchefstroom Campus, 2009.

The aim of this experiment was to test whether LIPX-induced decreases in body fat affect appetitive (foraging effort and food hoarding) or consummatory (food intake) ingestive behaviors and whether the effects of LIPX on these behaviors is in turn affected by changes in energy expenditure produced by varying the amount of work required to obtain food. This was accomplished by housing male Siberian hamsters (Phodopus sungorus) in a foraging/hoarding apparatus where food pellets (75 mg) could be earned by completing various wheel running requirements. Requiring a foraging effort (10 revolutions/pellet) abolished the normal compensation of WAT mass by the non-excised WAT pads that typically follows IWATx or EWATx. After foraging, food hoarding was increased more than food intake when hamsters were required to forage for food (10 revolutions/pellet). The magnitude of the LIPX-induced lipid deficit (IWATx > EWATx) did not correspond to a proportional change in either appetitive or consummatory ingestive behaviors.

Emerging evidence suggests that sedentary behaviour is independently associated with cardiometabolic disease risk in school-aged children and youth. This thesis includes 4 related studies in the pursuit of 2 objectives: 1) To determine the cross-sectional association of sedentary time, interruptions in sedentary time, sedentary bout length, and total movement variability with markers of cardiometabolic disease risk among children and youth, and 2) To examine the impact of 1-day of prolonged sedentary behaviour, with and without interruptions or structured physical activity, on markers of cardiometabolic disease risk, hunger, food intake and spontaneous physical activity levels in children and youth. In Study 1, we found that interruptions in sedentary time and short bouts of sedentary time were beneficially associated with clustered cardiometabolic disease risk in boys and girls aged 8-11 years, independent of total sedentary time, moderate-and-vigorous physical activity (MVPA), and other confounders (all p<0.05), while the opposite was true for screen based sedentary behaviours. In Study 2, we found that movement variability (minute-to-minute changes in movement intensity) was negatively associated with clustered cardiometabolic disease risk and systolic blood pressure independent of MVPA, sedentary time and other covariates in a representative sample of American children and youth aged 12-17 years (all p<0.05). In Studies 3 and 4, we found that prolonged sitting, with or without interruptions and structured MVPA did not result in acute changes in markers of cardiometabolic disease risk, nor subsequent ad libitum food intake or physical activity levels in healthy children aged 10-14 years (all p ≥0.05). Taken together, the studies that make up this thesis suggest that optimal levels of cardiometabolic disease risk are most likely to be seen in children who limit their time engaging in screen-based sedentary behaviours, who frequently interrupt their sedentary time, and who have high levels of variability in their movement behaviours.

Thesis (M.A. (Human Movement Science))--North-West University, Potchefstroom Campus, 2009.

The objective of this research was to determine the effect of stage of maturity at the time of harvest for barley and oat whole-crop forage on feed intake, ruminal fermentation and digestibility, and the impact forage allocation has on intake and ruminal fermentation. In the first 2 studies, whole-crop barley (Study 1; c.v. CDC Cowboy) and oat (Study 2; c.v. CDC Weaver) forage were harvested at the late milk (LM), hard dough (HD) and ripe (RP) stages and offered ad libitum to ruminally cannulated heifers. Diets were supplemented in an attempt to balance crude protein (CP) among treatments. Heifer performance, dry matter intake (DMI), ruminal fermentation parameters, ruminal digestibility, and total tract digestibility were evaluated. In Study 3, whole-crop oat (c.v. CDC Weaver) forage harvested at HD and RP was offered ad libitum to ruminally cannulated heifers in either daily (1-D) or 3 d (3-D) allocations. Dry matter intake and ruminal fermentation parameters were measured. In Study 1, harvest maturity of barley did not affect DMI (P = 0.70; average 5.4 kg/d) or average daily gain (ADG; P = 0.64). Total tract digestibility was decreased for barley harvested at HD (P = 0.003), but harvest maturity did not affect daily digestible energy (DE) intake (P = 0.52). Minimum ruminal pH for heifers fed the barley forage was lowest for LM (6.09), intermediate for RP (6.13), and greatest for HD (6.25; P = 0.016). Total short chain fatty acid (SCFA) concentrations were not affected by harvest maturity (P = 0.36). In Study 2, harvest maturity of whole-crop oat did not affect DMI (P = 0.26; average 8.1 kg/d) or ADG (P = 0.52). There were no effects of harvest maturity of oat forage on total tract digestibility (P = 0.78) or daily DE intake (P = 0.68). The minimum ruminal pH from heifers fed oat forage was lowest for HD (5.84; P = 0.012), intermediate for RP (5.94) and greatest for LM (5.99). There was no effect of harvest maturity of oat forage on total SCFA concentrations (P = 0.21). The quantity of forage allocation (Study 3) had no effect on total or forage DMI over a 3-d duration (P ≥ 0.47). Throughout the 3-d feeding period, 3-D allocated heifers had a reduction in the area pH was under 5.8 (214.4, 79.5 and 10.9 pH × min/d, for d 1, 2 and 3, respectively; P = 0.003). Total SCFA concentrations were not affected by forage allocation or harvest maturity (P ≥ 0.14), however there was an interaction of forage allocation and day in the feeding cycle (P = 0.046). Heifers allocated 1-D had no change iii in total SCFA concentration over the 3-d feeding period (averaged 122 mM), but 3-D allocation had elevated concentrations on d 1 (138 mM) intermediate on d 2 (135 mM) and decreased on d 3 (117 mM). These data suggest that harvesting barley and oat at the HD stage improves DM yield without negatively affecting cattle DMI and ADG. These data also suggest that providing 3-d allocations of forage does not affect DMI, but can increase daily fluctuations of ruminal pH and ruminal SCFA concentrations.

Previous research documented the fetus is sensitive to nutrition of the dam, but this has not been thoroughly investigated in horses. Objectives of the current studies were to determine effect of manipulation of maternal nutrition during the last third of pregnancy on mare performance, intake, hormones, foaling parameters, colostrum, and foal passive transfer of immunity and growth, and effects of supplemental arginine. Plane of nutrition influenced mare performance, and DMI was influenced by time with the first trial finding all mares consumed less in the 10th month of pregnancy compared to the 11th month, and the second trial finding all mares consumed less during the 11th month. Additionally, the second study determined arginine supplementation has no detrimental effects on DMI. Both studies indicated the dual marker system was sufficient at estimating DMI. Neither trial found an influence of treatment on foaling parameters or physical measurements obtained following parturition, and the second study determined arginine supplementation also did not affect foaling or measurements. The first study determined maternal nutrition did not affect foal growth or ADG. When colostrum quality was evaluated, the first study determined mares consuming only hay had increased specific gravity and Brix% indicating higher quality. This was confirmed by IgG analysis finding a tendency for increased IgG concentration. However, colostrum volume was not affected by nutrition, nor was total g IgG. The second study found contrasting results with greater specific gravity in mares on a high plane of nutrition, and a tendency for moderate plane of nutrition mares to have greater volume. Additionally, the second study determined that arginine supplementation does not influence colostrum volume or quality (measured by specific gravity or Brix %). In the first trial, maternal diets affected glucose and insulin AUC in mares, which altered insulin dynamics in the resulting foals. Foal insulin AUC and peak insulin concentration were greater in foals from mares supplemented with concentrate compared to foals from mares fed hay alone. These studies have provided a wealth of information to help elucidate the impact of maternal nutrition in late gestation on mares and their foals.

Food intake is regulated by both appetite and orosensory reward systems. Appetite systems stimulate or reduce hunger, while orosensory reward motivates consumption of high fat sweet foods, resulting in food enjoyment. The majority of advanced cancer patients suffer from malnutrition and wasting, which may be caused by a loss of appetite due to physiological changes or a hindered orosensory reward system due to taste and smell (chemosensory) changes or both. Orosensory reward systems were hypothesized to be impaired in advanced cancer. To understand the influence of chemosensory alterations on food intake and enjoyment, the nature (intensity) of chemosensory alterations in cancer patients and their relationship with ingestive behaviour and quality of life (QOL) were investigated (study 1). Advanced cancer patients (n=192) more frequently self-reported tastes and odours to be heightened rather than diminished (p=0.035). Patients with perceived chemosensory alterations had poorer QOL (p=0.0176) and lower caloric intake (p=0.0018) compared to patients with no alterations. Cannabinoids (e.g. -9-tetrahydrocannabinol, -9-THC) increase food intake by stimulating both appetite and orosensory reward systems as well as potentially enhancing chemosensory function. To palliate chemosensory alterations and poor appetite, advanced cancer patients (n=21, study 2) with these symptoms were randomized to receive either -9-THC (2.5mg) or placebo oral capsules twice daily for 18 days. Compared to patients receiving placebo, -9-THC-treated patients reported that food tasted better (p=0.04), they had improved chemosensory perception (p=0.026), increased preference and intake of high protein foods (p=0.008), and improved appetite (p=0.05), quality of sleep (p= 0.025), and relaxation (p= 0.045). Like cancer patients, tumour-bearing rats appeared to experience a loss of orosensory reward, showing tumour-associated anorexia when fed a rewarding diet to the same degree as on a usual diet (study 3). -9-THC significantly increased caloric intake compared to vehicle for both tumour-bearing (p=0.0146) and healthy rats (p=0.0004), suggesting endocannabinoid-mediated appetite systems are functioning in this tumour model. The findings of this thesis suggest orosensory reward systems to be impaired in advanced cancer, decreasing the liking and motivation to eat. -9-THC treatment may help to palliate perceived chemosensory alterations and loss of appetite and food enjoyment in advanced cancer. / Food Science and Technology

The objectives of this study were to characterize residual feed intake (RFI) in growing bulls and heifers and in mid-gestation females to examine relationships with performance, body composition, feeding behavior, digestibility (DMD) and heart rate (HR) and evaluate the impact of RFI on bull fertility and cow forage utilization. Additionally, use of the n-alkane method to predict individual animal variations in intake was investigated. To accomplish these objectives, multiple RFI studies were conducted. In all studies RFI was computed as the difference between actual and expected DMI from linear regression of DMI on mid-test metabolic BW and ADG. To evaluate phenotypic relationships between feed efficiency, scrotal circumference (SC) and semen-quality an experiment was conducted with yearling bulls (N=204). Residual feed intake was not correlated with BW and ADG, but was positively associated with 12th-rib back fat (BF) such that the more efficient bulls were leaner. Bulls with low RFI had similar SC and progressive motility of sperm compared to high-RFI bulls. However percent normal sperm were weakly associated with RFI in a negative manner. To examine phenotypic relationships between heifer postweaning RFI, and performance, efficiency, HR, and DMD of mid-gestation cows, RFI was measured in growing Bonsmara heifers (N=175). Forty-eight heifers with divergent RFI were retained for breeding. Subsequently, intake, performance and feeding behavior was measured on mid-gestation females. Pregnant females classified as having low postweaning RFI continued to consume 22% less feed, spent 25% less time eating, and had 7% lower HR while maintaining similar BW, ADG and body composition compared to high RFI females. A moderate association between RFI in growing heifers and subsequent efficiency of forage utilization in pregnant cows was found. Growing heifers identified as efficient had greater DMD, however DMD in mature cows was similar between RFI groups. The n-alkane method of predicting intake detected differences in intake between divergent RFI groups in mid-gestation females. Results from this study indicate that inclusion of RFI as a component of a multi-trait selection program will improve feed efficiency of growing animals and mid-gestation females with minimal impacts on growth, body composition, and fertility traits.