Neutering is often associated with obesity in companion animals. However, the maintenance energy requirement (MER) for these animals has not been clearly defined. The present study investigated the MER for spayed cats whose body weights (BW) began to increase shortly after ovariohysterectomy. A total of twenty-two shorthair adult female cats were fed complete and balanced diets in amounts to maintain their BW and body condition score (BCS) before the present study. All cats were spayed and the diet was fed for 11 weeks using the same MER as previously. During these weeks, all cats gained weight. Beginning with week 12, a weight-loss regimen was initiated until each cat achieved a BCS of 5 out of 9. After each cat obtained a BCS of 5, an appropriate amount of diet was fed to maintain its BW for at least 4 weeks to determine a modified MER. Daily food consumption, weekly BW and BCS were monitored. Blood was collected before and after weight loss for plasma biochemistry profiles. BW and BCS increased by 16 % and one point (P,0·01), respectively, during the first 11 weeks after surgery, although food consumption was constant both pre-and post-surgery. The mean MER after obtaining a BCS of 5 was 313·6 (SEM 23·6) kJ/BW 0·67 , which is 25 % lower than the current National Research Council recommendation and lower than the cat's requirement before surgery (P, 0·05). In conclusion, spaying significantly increased BW when using MER values for intact cats. Thus, 313·6 £ ideal BW 0·67 kJ is proposed for the MER of spayed adult cats.

SUMMARY. Parathyroid hormone (PTH) concentrations were compared in serum and EDTA plasma from 36 patients attending a renal stone clinic. Serum PTH concentrations ranged from 0·9 to 10·9pmol/L, with a mean of 4·6 pmoljL. When serum and EDT A plasma results were compared, in samples frozen within 30min of collection, EDTA plasma results were found to be significantly higher than those in serum (P

Parathyroid hormone (PTH) concentrations were compared in serum and EDTA plasma from 36 patients attending a renal stone clinic. Serum PTH concentrations ranged from 0.9 to 10.9 pmol/L, with a mean of 4.6pmol/L. When serum and EDTA plasma results were compared, in samples frozen within 30 min of collection, EDTA plasma results were found to be significantly higher than those in serum (P < 0.0001; Wilcoxon test), with an average increase of 19.5% over the serum result. Results from EDTA-preserved blood left to stand at room temperature for 48 h were on average 14.8% lower than results from the corresponding EDTA plasma samples frozen within 30 min, with highly significant difference (P < 0.0001). Freshly frozen serum and 48h EDTA plasma PTH results were not significantly different. Parathyroid hormone in EDTA-preserved blood is not completely stable, and this could lead to misclassification of results for samples which are not frozen quickly.

An opportunity to investigate a low-arachidonic acid (AA) feline diet possibly related to elevated peroxide value (PV) during storage on plasma phospholipid (PL) and reproductive tissue fatty acid (FA) profiles presented itself in the present study. Cats (nine animals per group) had been fed one of three dry extruded, complete and balanced diets for 300 d before spaying. The diets contained adequate AA (0·3 g/kg), similar concentration of antioxidants and were stored at ambient temperature, but differed in FA composition. The diets were designated as follows: diet A (high linoleic acid), diet B (high g-linolenic acid) and diet C (adequate linoleic acid). Diet samples that were obtained the week before spaying revealed an elevated PV of diet A v. diets B and C (135 v. 5·80 and 2·12 meq/kg fat, respectively). Records revealed decreased food consumption of diet A cats beginning at 240 d but without weight loss; thus an opportunity presented to investigate diet PV effects. Total plasma protein and PL-AA concentrations in group A were significantly decreased at 140 and 300 d. Uterine and ovarian tissues collected at surgery revealed modest decrements of AA. Diet A was below minimum standards at 0·015 % (minimum 0·02 %), probably due to oxidation. The time at which diet A became unacceptable may have occurred between 60 and 140 d because plasma PL-AA was within our normal colony range (approximately 4 -7 % relative) after 56 d of feeding. High-linoleic acidcontaining diets may be more likely to be oxidised requiring additional antioxidants. The findings suggest that reduced plasma protein in combination with plasma AA concentrations may serve as biomarkers of diet peroxidation in cats before feed refusal, weight loss or tissue depletion.

Arachidonic acid (ARA) is essential in felines because conversion of dietary linoleic acid (LA) to ARA is rate-limited by low Δ6-desaturase. Dietary γ-linolenic acid (GLA) may serve as an ARA precursor by-passing this initial rate-limiting step. This possibility was investigated using twenty-six adult female domestic shorthair cats divided into three groups and fed on complete and balanced diets containing high GLA (GL), high LA (HL) or low LA (LL, control) diets, for 300 d prior to ovariohysterectomy. Plasma was obtained 1–2 d before surgery and uterine, ovarian and associated adipose tissues were reserved for lipid analysis. Fatty acid profiles of the plasma phospholipid (PL) fractions and adipose lipids were performed. In the GL group, plasma and uterine tissue PL were significantly enriched in GLA, di-homo GLA (DGLA) and ARA compared with control. However, ovarian and adipose tissue PL were only enriched in DGLA. Enrichment of uterine tissues with DGLA and ARA probably supplies the essential eicosanoid precursors for reproduction when GLA is fed consistently with an active Δ5-desaturase in uterus. By contrast, this enzyme appears less active in ovary because ARA was not higher compared with control. Earlier reports concluded that ARA was not necessary for fertilisation (an ovarian function), but required for successful pregnancy and reproduction (a uterine function). Adipose tissue DGLA may be a reservoir for ARA synthesis by other tissues upon mobilisation. Dietary GLA may meet feline ARA requirements in the absence of an animal-based preformed source of ARA.