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J Craigon

Publications and source records attributed to J Craigon.

7 recordsLinked to original sources
PubMed1992

Evaluation of inert markers for the determination of ileal and faecal apparent digestibility values in the pig.

A series of experiments was designed to evaluate inert markers employed in studies of ileal and faecal apparent digestibilities of nitrogen and amino acids in pigs fitted with simple 'T' piece cannulas. Trial 1 assessed the palatability of diets containing (a) 5 g chromic oxide/kg, (b) 1 and (c) 5 g titanium dioxide/kg at two levels of feeding. The results indicated that there were slight problems in terms of period of feed consumption associated with diets (a) and (c), but that these effects were transitory and disappeared following acclimatization, although higher levels of feeding may compound the problem. Trial 2 estimated N balance, faecal apparent digestibility of amino acids as determined by both total collection and ratio of markers, ileal apparent digestibility of amino acids and recovery of markers using diets containing (a) 1 and (b) 5 g Cr2O3/kg, (c) 1 and (d) 5 g TiO2/kg. An additional assessment of acid-insoluble lignin present within the diet was also undertaken. Cr2O3 was associated with the lowest recovery, whilst calculations based on TiO2 gave lower standard errors. Trial 3 examined diurnal variation in digesta sampling and its effect on faecal apparent digestibility of N and amino acids. There were no evident effects. In general, it was concluded that the most appropriate marker to use in studies of this nature was TiO2 at a rate of 1 g/kg.

Amino Acids↗
PubMed1991

Prediction of the apparent metabolizable energy content of fats fed to broiler chickens.

Soybean oil and tallow acid oil were blended in the ratio 75:25, 50:50, and 25:75 to give 3 blends (A, B, and C) of increasing free fatty acid (FFA) content but decreasing ratio of unsaturated to saturated fatty acids (U:S). Tallow and soybean acid oil were blended in similar proportions to give three blends (D, E, and F) of increasing FFA content and increasing U:S ratio. The six fats were incorporated into a basal diet at rates of 40, 80, and 120 g/kg. Experimental diets were evaluated for apparent available fat (AAF) with broilers aged 1.5 and 7.5 wk of age. The AAF of fats was calculated from extrapolation of the regression of AAF of diets to rate of inclusion of fats. The AME of fats was determined as the product of AAF and gross energy. Increasing FFA content but reducing U:S ratio lowered the AME giving 31.1, 28.7, and 21.7 MJ/kg (1 MJ = .239 Mcal) and 33.2, 31.5, and 28.4 MJ/kg, respectively, for A, B, and C for young and old birds. Corresponding data for D, E, and F (increasing FFA content and U:S ratio) were 27.7, 28.0, and 29.4 MJ/kg and 31.8, 32.9, and 33.3 MJ/kg, respectively, for young and old birds. Data generated, together with results from previous reports, were subject to regression analysis. The AME of fats could be predicted from knowledge of U:S ratio and FFA content with equations accounting for .816 and .925 of the variation in AME values for young and old birds, respectively.

Analysis of Variance↗
PubMed1985

Time series analysis of plasma LH and FSH concentrations as a method of assessing episodic secretion.

Time series analysis was used to detect LH and FSH episodes in untreated seasonally anoestrous ewes and prepubertal heifers, and in these animals when treated with low doses of GnRH. For comparison, these profiles were also assessed for episodic secretion by subjective, visual appraisal methods and by cycle detection-an objective threshold method. In untreated animals, time series analysis detected recurring events in the LH and FSH profiles, the period lengths of which varied between individual animals. When GnRH was injected at 2-h intervals, cycles in LH secretion with period lengths of 120 min were recorded in all animals, of 60 min in all ewes and 11/12 heifers, and of 40.5 min in 22/24 ewes and 10/12 heifers. The cycles with period lengths of 60 and 40.5 min are probably artefacts of this method of analysis. No consistent cycles in FSH release were detected in GnRH-injected anoestrous ewes, but 120-min cycles were recorded in 8/12 GnRH-injected heifers. When GnRH was administered to seasonally anoestrous ewes by continuous infusion, recurring cycles in both LH and FSH secretion were evident. However, there was no consistency in their period lengths and the mean number and frequency of cycles were similar to pretreatment values. The number of episodes detected by visual appraisal was influenced by the choice of episode definition. Both methods identified LH, but not FSH, episodes in response to each injection in all GnRH-injected animals. Cycle detection, which does not identify individual episodes, recorded LH and FSH episode frequencies similar to those detected by the more stringent method of visual appraisal. Time series analysis detected an FSH response to GnRH injections in prepubertal heifers that was not identified by the other methods of analysis. However, because of the asymmetric nature of LH episodes, it also detected cycles in LH profiles that were probably spurious. Subjective decisions influenced the frequencies of LH and FSH episodes recorded by visual appraisal, and the variation in episode amplitude in these profiles made cycle detection inappropriate. Each of these methods can contribute to the interpretation of hormone profiles, but their constraints and limitations must be recognized.

Anestrus↗