Comparative net digestive and absorptive efficiency was assessed with adult Beagles and domestic cats by apparent digestibility assays. Eight foods were used comprising two canned dog foods; canned cat foods; two samples of semipurified diet; and single samples of experimental dry cat food and fresh mince. Apparent digestibility percentages of crude protein, fat, nitrogen‐free extract (NFE) and gross energy were all significantly higher in dogs than cats. Mean values obtained for dogs were (per cent): crude protein 87; fat 92; NFE 70 and energy 89. Respective values for cats were 82, 76, 67 and 79. On average, dogs obtained 11 and 9 per cent more digestible energy and protein per unit food eaten than cats. Most digestibility characteristics of foods measured in cats were significantly correlated with those for dogs and regression equations are presented predicting digestibility in cats from dog data.

A series of trials was conducted to measure the extent of individual variation in feedblock intake for ewes on upland/hill farms. From 15 flocks on nine farms 4284 ewes were selected with a range of environmental conditions and levels of performance. Ewes were given either Rumevite, Norbloc or Wintawell feedblocks containing chromic oxide. Faecal grab samples were taken per rectum from individual ewes and analysed for their chromium content to obtain estimates of feedblock consumption.The results showed that provision of feedblocks does not ensure a uniform intake of supplementary nutrients by sheep in upland/hill situations. On average, 19% of the 2931 ewes sampled had not eaten the feedblock on offer. The proportion of ewes not consuming feedblock varied from flock to flock (0 to 67%). The coefficient of variation of faecal chromium concentrations varied between flocks (46 to 231%). The reasons for the large variation in intakes observed are discussed. Feedblock intake was significantly affected by the grazing area per ewe (P<0·01) and the age of ewes (P<0·05 to P< 0·001).

The apparent digestibility of 21 plant materials was evaluated in dog diets using adult beagles. In most cases the digestibility by difference method was used. Apparent crude protein (N x 6.25) digestibility coefficients for textured soya protein, extracted soya meal, full-fat soya flours and micronised whole soya beans ranged from 0.71 to 0.87. Digestible energy (DE) contents ranged from 14.3 to 20.8 MJ kg DM-1. Samples of wholeground wheat, barley meal and flaked maize were well digested by dogs, as were samples of refined flour, vital gluten, feeding-oat meal and wheat-germ meal; apparent energy digestibility coefficients ranged from 0.72 to 0.96. Wheatfeed and two distillers by-products had lower energy digestibility coefficients (0.39 to 0.59). Other materials with low apparent digestibility in dog diets (probably because of high fibre levels) were. walnut meal, almond meal, dried molassed sugar beet pulp and locust bean meal. Gross energy and dry matter digestibility coefficients of below 0.52 were obtained. Data are also presented on the digestibility of sampks of rapeseed meal, cassava and dried potato. When comparison was possible, DE values measured for dogs agreed closely with those for pigs for most materials.

The purpose of the work was to assess endogenous nitrogen output in dogs of widely contrasting mature body size and genotype. Fecal and urinary nitrogen excretion was measured during 14-day metabolic periods in 25 adult dogs of body-weight range 2.8-51.0 kg fed a protein-free, semipurified diet. Endogenous nitrogen excretion was assumed from day 8 after introduction of the protein-free diet and was measured during the final 7 days of each period. Mean (+/- SEM) endogenous urinary nitrogen (EUN), metabolic fecal nitrogen (MFN), and total endogenous nitrogen (TEN) outputs were 210 +/- 9, 63 +/- 3 and 273 +/- 9 mg/kg 0.75 per day. There were no significant effect of either sex or body weight on the magnitude of EUN, MFN or TEN outputs, however, EUN output was positively and significantly (P less than 0.02) correlated (r = 0.50) with percentage body-weight loss during the metabolic period. The mean values obtained for endogenous nitrogen output in adult dogs agreed closely with previous estimates in the literature for dogs exhibiting a narrower range (8.3-16.7 kg) of mature body weight.

The data from 106 digestibility trials with dogs were analysed with the objective of developing a predictive relationship between in vivo digestible energy (DE) content of foods and analytical components. The foods were commercial formulations arranged into three categories (wet, intermediate-moisture and dry) on the basis of water content and ingredient profile. Mean (n= 106) apparent crude protein, acid ether extract and nitrogen-free extract digestibility coefficients were 0.81, 0.85 and 0.79, respectively. The use of modified Atwater factors to predict food metabolisable energy (ME) gave values 104, 99 and 109% of in-vivo DE values for wet, intermediatemoisture and dry foods and thus over-estimated food energy value. Sixteen single function or multiple regression equations were generated predicting DE content of each dog food category from gross energy (GE), Atwater ME, proximate components and digestible nutrient content. The DE content of wet and intermediate-moisture foods was estimated with high precision using the single function of GE. Coefficients of determination (R2) for significant (P < 0.001) linear regression equations were 0.96 and 0.89, respectively. Other useful multiple regression equations were identified between in-vivo DE and combinations of total and digestible proximate components ( R 2 > 0.80). Less reliable relationships were obtained for the prediction of DE content of dry dog foods, probably because estimates of fibre content were not included; greatest precision (R2 = 0.60) was obtained for the linear regression between in-vivo determined DE and analysed GE content.