Delayed gastric emptying in the obese: an assessment using the non-invasive (13)C-octanoic acid breath test.

AIM: Much of the controversy surrounding the correlation between obesity and gastric emptying lies in the inconsistency of methodology and analysis. This study was designed to overcome some of the discrepancies encountered in previous studies and to test the hypothesis that obese individuals have altered gastric emptying compared to lean individuals. METHODS: Gastric emptying was measured using the (13)C-octanoic acid breath test in 16 lean and 16 obese women pair-matched for age. Following an overnight fast, subjects were given a standard 2 MJ egg meal labelled with 100 microl of [1-(13)C]-octanoic acid. Breath samples were collected at regular intervals over a 6-h period. (13)C-isotopic enrichment in the breath was analysed using isotope ratio mass spectrometry and the data fitted to the established gastric emptying model. The lag times (t(lag)), half excretion times (t(1/2)), latency phase (t(lat)) and ascension times (t(asc)) were calculated. RESULTS: The mean t(1/2)-values (+/-standard error of the mean) were 3.67 +/- 0.14 h and 4.23 +/- 0.18 h for lean and obese respectively, indicating significantly delayed gastric emptying in the obese (p = 0.019). The obese group also showed a significantly slower lag time (t(lag), p = 0.005) and latency phase (t(lat), p = 0.005), but no significant difference was found in the ascension time (t(asc), p = 0.154). Within groups, no correlation was found between half excretion times and body weight or half excretion times and body mass index. CONCLUSIONS: The present study demonstrated a prolonged lag phase and delayed gastric emptying in obese women when compared to lean women. This delay may be as a consequence of high-fat diets, a sedentary lifestyle and increased gastric distension associated with obesity, or a contributing factor in the pathogenesis of obesity resulting from the inactivation of gastrointestinal satiety signals and in an increase in food intake.

Effect of whole herd anthelmintic treatment on milk production of dairy cows.

Fifteen of 29 commercial dairy herds were given a series of anthelmintic treatments. The remaining herds were untreated to provide a measure of seasonal variation. In the treated herds all milking cows were treated once in the summer and the autumn and three times at monthly intervals in late winter and early spring. Any other animals grazing the same area were similarly treated. No herds had been treated with anthelmintics in the preceding year and mean herd lactations for that year were used as covariate corrections. This experimental design had the potential to detect differences in production of the order of 5 X 7 per cent (P = 0.05). Although levels of subclinical parasitism were low, anthelmintic treatment increased milk fat production by 10.8 kg (8.3 per cent) in heifers. Average response in mature cows was much smaller (3.1 per cent) and not significant. Apparent milk fat responses in individual herds were variable with no relationship to level of production in the previous year.

Effect of anthelmintic treatment immediately after calving on milk production.

The effects of anthelmintic treatment on the milk production of cows subjected to contrasting nutritional conditions before and after calving were determined. Half of the cows in each of 2 management treatments were treated with 3.75 grams of fenbendazole on the second day after calving and twice more at weekly intervals. Treated and control cows were grazed together for the entire lactation. Treated cows produced 8% more (P less than 0.05) milk over the 20 weeks lactation than the untreated cows. One third of the total lactation response to anthelmintic treatment occurred during weeks 5 to 10 of lactation. The observed responses occurred despite equal larval challenge to treated and control cows and therefore the responses obtained are discussed in the context of a reduction in the worm burden.

The importance of prolactin and the milking stimulus in the artificial induction of lactation in cows.

Lactations were successfully induced in 15 out of 18 non-pregnant cows treated with oestradiol-17beta (0.1 mg/kg body weight) and progesterone (0.25 mg/kg body weight) on days 1-7 (where day 1 is the first day of treatment). A further 23 out of 26 cows were successfully treated with oestradiol-17beta and progesterone standardized at 40 and 100 mg/day respectively. No significant differences in milk yields were obtained by the additional treatments of twice daily milking from day 10, sustained elevation or suppression of plasma prolactin during the induction phase by reserpine and bromo-cryptine respectively, or by continuing oestradiol-17beta injections alone on days 8-11. Levels of plasma prolactin less than 20 ng/ml were adequate for the preparation of the mammary gland for lactation to occur. The induced lactation of 24 monozygotic twin cows ranged from 20 to 87% of their respective siblings which had normal parturient lactations. All 11 cows treated with the standard oestrogen-progesterone treatment plus reserpine had successfully induced lactations. In the absence of oestrogen and progesterone treatment, a short period of resperpine treatment followed by dexamethasone trimethylacetate failed to induce lactation in five cows. Ninety per cent of induced cows (n = 39) and 91% of parturient cows (n = 22) conceived and subsequently calved following natural mating.