The Effect of Caffeine Ingestion during Evening Exercise on Subsequent Sleep Quality in Females.

In a randomised, double-blind, placebo-controlled crossover design, 10 females taking monophasic oral contraceptives completed 90 min intermittent treadmill-running 45 min after ingestion of 6 mg∙kg(-1) body mass anhydrous caffeine or artificial sweetener (placebo). Water (3 mL∙kg(-1)) was provided every 15 min during exercise. Venous blood samples were taken before, during and after exercise, as well as after sleep (~15 h post-ingestion), and levels of caffeine, paraxanthine, theobromine and theophylline were measured using high-performance liquid chromatography. Sleep quality was assessed using the Leeds Sleep Evaluation Questionnaire. Plasma caffeine concentration peaked 100 min after ingestion. Caffeine clearance was 0.95±0.14 mL·min(-1)·kg(-1) while the elimination half-life of caffeine was 17.63±8.06 h. Paraxanthine and theophylline levels were significantly elevated at 15 h with no significant change in theobromine. Sleep latency and subsequent quality of sleep was impaired following caffeine supplementation (P<0.05); there were no differences between trials for how participants were feeling upon awakening. This is the first controlled study to examine caffeine supplementation on sleep quality in female athletes taking a low-dose monophasic oral contraceptive steroid following an intermittent-exercise running protocol. The data shows that female athletes using monophasic oral contraceptive steroids will have impaired sleep quality following evening caffeine ingestion.

The potential for enhancement of immunity in cats by dietary supplementation.

This study was conducted to examine the potential benefits of dietary supplementation on the feline immune system. Forty three cats (8 or 9 per group) were fed a low protein control diet (22.7% DM basis), the same diet supplemented with yeast-derived nucleotides, salmon oil or l-arginine or a commercial moist high protein diet (53.0% DM basis) for a period of five weeks. The low protein diets were formulated using a commercial moist diet base with added fat and starch and fed ad libitum, along with water. Specific immune assays showed that supplementation with arginine caused a significant enhancement of lymphocyte proliferative responses to the T-cell mitogen PHA after 35 days (P=0.018), while supplementation with either nucleotides or salmon oil resulted in significant enhancement after both 14 (P=0.0048, P<0.0001 respectively) and 35 days (both P<0.0001). Dietary supplementation with arginine, nucleotides or salmon oil each led to significant increases in blood leucocyte phagocytic activity after both 14 (P=0.0003, P=0.0077, P<0.0001 respectively) and 35 days (P<0.0001). This indicates that a number of dietary ingredients have the ability to modulate the immune system of healthy cats possibly resulting in a greater ability to fight infection and disease.

Age, breed, sex distribution and nutrition of a population of working farm dogs in New Zealand: results of a cross-sectional study of members of the New Zealand Sheep Dog Trial Association.

AIM: To establish baseline information about age, breed, sex distribution and feeding practices for a population of working farm dogs owned by members of the New Zealand Sheep Dog Trial Association (NZSDTA) throughout New Zealand. METHODS: Questionnaires were sent to members of the NZSDTA in August 2007, requesting information on the size and terrain of the farms where they worked, as well as the breed, weight, age and sex of each working dog they owned, feeding regime employed, diet fed, work levels, and general health of their dogs. RESULTS: The survey was completed by 542/676 (81%) of the eligible sample population, and provided information on 2,861 dogs, excluding those <1 year old. All of the dog owners surveyed worked on sheep and beef-cattle farms. The median farm size was 440 [Inter-quartile range (IQR) 132-1,200] ha and varied with region. The majority of farms were situated on either hill country (184/542; 34%) or a mixture of hilly and flat terrain (260/542; 48%), and had a median of six (IQR 5-8) working dogs per farm. The median age of dogs was 3.0 (IQR 2.0-6.0) years. Heading dogs were the most common type of working dog (1,510/2,861; 52.8%), followed by Huntaways (1,161/2,861; 40.6%). The gender distribution of all dogs was biased towards males (57%), but this decreased with age. There was a positive association between the number of dogs on a farm and perceived level of tiredness of dogs (p<0.001), but there were no differences in levels of tiredness between farms of different terrain. Most owners (526/542; 97%) fed their dogs once a day. The most common diet fed was a combination of dry food and homekill, which was fed by 328/542 (61%) owners during peak and 313/542 (58%) during off-peak periods of work. CONCLUSIONS AND CLINICAL RELEVANCE: This study has established baseline information on the age, breed, gender and nutrition of a large population of working farm dogs in New Zealand. Current feeding practices employed by owners include offering a substantial amount of homekill to their animals. Homekill may be deficient or marginal in vitamins and minerals, therefore opportunities could exist to improve the diets and therefore the longevity and performance of these dogs.

The effects of the proportions of dietary macronutrients on the digestibility, post-prandial endocrine responses and large intestinal fermentation of carbohydrate in working dogs.

AIM: To compare the effects of feeding diets varying in the proportions of macronutrients on the digestibility, post-prandial endocrine responses and large intestinal fermentation of carbohydrate in working dogs. METHODS: The apparent digestibility of two test diets, one comprising low-carbohydrate, high-protein dry biscuits (Diet 1), and one comprising high-carbohydrate, low-protein dry biscuits (Diet 2), fed to 12 adult Harrier Hounds (n=5 female), was determined using the indigestible-marker and total-collection methods. Serial breath samples were collected from each dog before and after feeding, and analysed for concentrations of hydrogen. Concentrations of glucose and insulin in plasma were established from serial blood samples obtained after feeding. RESULTS: The apparent dry matter, protein, fat and energy digestibility of Diet 1 were higher, but the carbohydrate digestibility was lower (p<0.05), than those of Diet 2. The apparent digestibility values determined using the total-collection method were lower (p<0.05) for carbohydrates, and tended to be lower for dry matter and energy (p<0.10) than those determined using the indigestible-marker method, but the values for protein and fat digestibility were similar using the two methods of determination. The maximum concentration (Cmax) of hydrogen detected in the breath of the dogs occurred earlier for Diet 1 than Diet 2 (p<0.01). However, the Cmax and area under the curve (AUC) for breath hydrogen were higher in the dogs fed Diet 2 than Diet 1 (p<0.01). The Cmax for glucose and insulin in plasma occurred earlier in dogs fed Diet 2 compared with those fed Diet 1 (p<0.05). However, the Cmax for glucose, and AUC for glucose and for insulin were not different between the two diets. The Cmax for insulin was greater for Diet 2 compared with Diet 1 (p<0.05). CONCLUSIONS: The low-carbohydrate, high-protein diet (Diet 1) appeared to offer certain advantages to working dogs, including higher apparent nutrient digestibility, slower release of glucose into the bloodstream, and reduced large intestinal fermentation of carbohydrate. CLINICAL RELEVANCE: A low-carbohydrate, high-protein diet may be beneficial for specific groups of dogs, including working dogs subjected to prolonged bouts of exercise requiring a sustained energy source, or those with diabetes mellitus requiring better glycaemic control.

Testosterone increases urinary free felinine, N-acetylfelinine and methylbutanolglutathione excretion in cats (Felis catus).

Two days after castration, urinary free felinine plus N-acetylfelinine decreased 24% in male cats, but, by day 5, the concentration had not decreased to that routinely found in males that have been castrated for several months. In a second experiment, three groups of castrated adult male cats received different subcutaneous injections: control (carrier), testosterone, testosterone plus estradiol. A fourth group of intact adult female cats received a testosterone injection. Urine was collected and analysed for free felinine, N-acetylfelinine and 3-methylbutanolglutathione. Baseline blood testosterone and estradiol concentrations were low during the pre-period, but increased sharply after hormone injections. The concentration of all three urinary metabolites increased as a result of testosterone injections with estradiol not modulating the effect. The effect of testosterone was not gender dependent. The concentration of free felinine, N-acetylfelinine and 3-methylbutanolglutathione in the urine remained low in the placebo control group throughout the study. The relative molar contribution of free felinine to the total amount of felinine containing compounds increased due to testosterone treatment, while the contribution of 3-methylbutanolglutathione and N-acetylfelinine decreased. Testosterone increases free felinine, N-acetylfelinine and 3-methylbutanolglutathione excretion in castrated adult male and intact female cats, whereas estradiol does not modulate this effect.

Mammalian isovalthine metabolism.

Isovalthine is a branched-chain sulphur amino acid, which has been found in the urine of normal cats. The concentrations of isovalthine in the urine of healthy adult cats are approximately 24-66 micromol/l and are not affected by the gender of the cat. Isovalthinuria can be induced in other species (rats, rabbits, guinea-pigs, humans, dogs) following the administration of certain inducing agents such as some hypocholesterolaemic agents, bile acids, hormones or cholesterol precursors. The method of induction of isovalthinuria was studied extensively during the 1960s, and efforts were made to understand its biosynthesis. However, although the origin of the sulphur atom in isovalthine was shown to be from cysteine or methionine, the origin of the carbon skeleton remains unknown. Interest in isovalthine metabolism was generated in part because it was reportedly found in the urine of patients with hypercholesterolaemia. The validity of this finding however, was brought into question following reports that administration of the drug Bromural (alpha-bromoisovalerylurea), to humans results in the generation of compounds which break down to yield isovalthine following acid hydrolysis. This article presents a review and discussion of the experimental data on isovalthine metabolism.