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Biomedical subjects

W G Stevenson

Publications and source records attributed to W G Stevenson.

148 records · Page 9Linked to original sources
PubMed1980

Energy and protein nutrition of early-weaned pigs. 1. Effect of energy intake and energy: protein on growth, efficiency and nitrogen utilization of pigs between 8-32 d.

1. The effect of energy and protein intake on the growth, food efficiency and nitrogen retention of artificially-reared pigs was studied over three 8 d periods between 8-32 d of age in an experiment employing a 5 x 3 x 2 factorial design. The factors were initial energy: N value (I; 250, 355, 460, 565 or 670 kJ/g N), rate of increase of I at 8 d intervals (0, 12.5 or 25%) and plane of nutrition (three times daily to appetite or 75% of this intake). 2. The range of energy: N values was obtained by formulating five diets based on dried skim milk, lactose and casein and feeding appropriate combinations of two diets. The diets, which were pelleted, contained 100 g maize oil/kg and the gross energy content was approximately 20 MJ/kg. 3. N digestibility was high at all three age intervals, reaching 0.99 on the diet containing the highest dietary crude protein (N x 6.25) level. Metabolic faecal N excretion was found to be I.I g/kg dry matter (DM) intake. 4. Growth rate, feed conversion ratio (kg food intake/kg wt gain; FCR), N retention (NR) and the proportion of digested N retained (NR: apparent digested N (ADN)) were significantly (P less than 0.001) affected by I values at all age intervals and the responses were quadratic. Response curves were calculated by the least squares method and optimum values of I determined for each of the criteria. A constant energy: N value of approximately 400 kJ/g N was indicated by growth, FCR and NR optima but the NR:ADN value fell from 0.77 for the 8-16 d period to 0.60 for the 24-32 d period at this I value. It is concluded that a suitable compromise would be an I value of 470 kJ/g N increasing by 10%/week. 5. There was a significant interaction between plane of nutrition and I values on FCR between 16-24 d (P less than 0.001) and 8-32 d (P less than 0.01) indicating that FCR was better at high protein levels and worse at low protein levels when the diets were fed on the lower plane of nutrition.

Aging↗
PubMed1980

Energy and protein nutrition of early-weaned pigs. 2. Effect of energy intake and energy: protein on energy utilisation and body composition of pigs slaughtered at 32 d.

1. The effect of energy and protein intake on the nitrogen and energy utilization and carcass composition of artificially-reared pigs was studied between 8 and 32 d of age in an experiment employing a 5 x 3 x 2 factorial design. The factors were initially energy:N value (1) (250, 355, 460, 565 or 670 kJ/g N), rate of increase of I (R) at 8 d intervals (0, 12.5 or 25%) and plane of nutrition (three times daily to appetite or 75% of this intake). 2. The range of energy:N values was obtained by formulating five diets based on dried skim milk, lactose and casein and feeding appropriate combinations of two diets. 3. The metabolizable energy (ME) intake, carcass dry matter (DM) content, carcass protein gain and carcass fat gain exhibited significant (P less than 0.001) quadratic responses to I. 4. The carcass fat content in the DM increased from 200 to 342 g/kg ( less than 0.001) and the carcass crude protein (N x 6.25) content decreased from 657 to 519 g/kg with increasing level of I (P less than 0.001). The fat and protein contents were 309 and 556 g/kg and 242 and 610 g/kg respectively on the high and low plane of nutrition (PN) and were significantly different (P less than 0.001). 5. There was a significant I x R interaction in relation to carcass protein gain with the maximum gain occurring at 460 kJ/g N when I was constant and at 355 kJ/g N when R was 25% per 8 d. 6. The proportion of apparent digested N intake retained (N retention (NR):apparent digested N (ADN)) was significantly (P less than 0.001) affected by all three factors and there were significant I x R (P less than 0.001), I x PN (P less than 0.01) and R x R x PN (P less than 0.01) interactions. The maximum value of NR:ADN was 0.80. 7. Carcass fat gain and carcass energy gain exhibited quadratic responses to I reaching maximum values at 460 kJ/g N. The energy content of the live-weight gain increased linearly (P less than 0.001) from 5.79 to 7.90 MJ/kg with increasing level of I. PN and R also produced significant (P less than 0.001) responses the means being respectively 7.52 and 6.39 MJ/kg on the high and low PN and 6.55, 6.94 and 7.38 kJ/kg with increasing value of R. 8. Multiple regression analysis of ME intake on live-weight (W), protein gain (PG) and fat gain (FG) yielded the equation: ME (MJ) = 0.644 W0.75 + 32.6 PG " 48.2 FG. This result is discussed in relation to published values for the energy requirements of the young pig.

Aging↗
PubMedDate not supplied

Effects of ventricular ectopy on sinus R-R intervals in patients with advanced heart failure.

OBJECTIVE: To determine the effect of ventricular ectopy on subsequent sinus R-R intervals. DESIGN: Comparative, repeated-measures design. SETTING: University medical center. SUBJECTS: Ten consecutive sinus R-R intervals and their standard deviations before and after ventricular ectopy from 24-hour ambulatory electrocardiogram recordings were obtained from 25 patients with heart failure (left ventricular ejection fraction 0.18 +/- 0.08; New York Heart Association Functional Class III-IV) and three healthy subjects. RESULTS: The effects of 7564 single ventricular ectopic beats, 272 ventricular couplets, and 49 episodes of ventricular tachycardia in the patients with heart failure and 1369 single ventricular ectopic beats in the three healthy subjects were evaluated. Repeated-measures ANOVA indicated no significant differences in sinus R-R intervals immediately before or after ventricular ectopy. Standard deviation of sinus R-R intervals before and after ventricular ectopy did not differ significantly. CONCLUSIONS: Ventricular ectopy does not significantly alter subsequent sinus R-R intervals and is unlikely to affect measurement of heart rate variability, particularly by techniques that use standard deviation methods.

Adult↗