Polish Merino małe lambs, average initial weight 16 kg, in 3 groups of 10, werefed to 38-40 kg liveweight on diets with 18,7 MJ/kg DM gross energy and 17 (H), 14 (M) and 10 % (L) crude protein. Six małe lambs of about 40 kg body weight, with simple duodenal and ileal cannulae were fed in a Latin sąuare design on diets of similar composition but containing Cr 2 0 3 and pelleted. Average daily gain in groups H, M, and L was 188, 180 and 159 g; intake per kg gain was : of metabolizable energy 53.7; 52.2 and 50.4 MJ, of crude protein 824, 660 and 595 g, respectively. Ammonia N content in duodenal digesta was on diet L less than on diets H and M (P<0.05). Apparent digestibility of total N in the smali intestine was on diets H and M 68.1%, on diet L 65.4%, the difference being significant (P^0.05). Absorption of essential amino acids was greatest of Met and Lys and least of Thr, regardless of diet. Decreasing the content of crude protein in diets for Polish Merino małe lambs to 14%, at 18.7 MJ gross energy per kg DM, did not reduce the amount of amino acids absorbed in the smali intestine and improved protein utilization.

The contents of short-chain fatty acids (SCFA) in the caecal digesta of rats fed diets containing 4 or 10% cellulose (control diets) or 10% apple pulp (P), apple pulp (V), apple pectin, potato fibre or potato pulp were measured. The diets were fed for 27 days to 7 groups of 10 rats each. The animals were sacrificed and the caecum was removed, tissue and digesta weighed, and caecum analysed for SCFA. Caecal tissue and digesta weight, pool of acetic, and propionic acids were highest with pectin-and the lowest with cellulose diets, while potato fibre and apple pulp gave intermediate levels. The proportions of acetic acid were higher and butyric acid lower on pectin than on the other diets. It is concluded that fibre from plant by-products differs in ability to form short-chain fatty acids in the caecum of rats, which is reflected in the amount of fermentable material reaching the caecum.

Three non-lactating cows of about 470 kg BW were fed rations of meadow hay and concentrate (79:21) containing fish meal (ration F) or rapeseed oilmeal (ration R).Total rumen content was evacuated manually before feeding (0 h) and 4 and 8 h after feeding. The interval between two successive evacuations was 7 days. Rate of passage of solid particles from the rumen was measured using Cr mordanted hay, liquid fraction outflow using Co-EDTA as indicators. Particle size distribution in the digesta was determined by wet-sieving using screen mesh sizes 5.0; 1.0 and 0.25 mm.The total amounts of rumen digesta, dry matter and crude protein measured at different times after feeding did not depend on the source of protein in the ration. The potential digestibility of crude fibre, ADF, NDF and ADL was higher (P < 0.05) on the ration with fish meal, particularly 8 and 12 h after feeding. The proportion of the different sizes of particles in DM of total digesta was uniform over time after feeding. The proportion of particles smaller than 1 mm was only a little higher in the rumen of cows fed ration F (P < 0.05). Crude protein content was higher (P < 0.05) in particles larger than 5 mm and of lignin in particles smaller than 1 mm when feeding the fish meal-containing ration. The proportion of particles in the rumen DM smaller than 1 mm was 64% at 4 and 8 h and increased to about 70% at 12 h after feeding both rations.The critical particle size was found to be 0.52 mm, rumen outflow rate of the solid fraction was 6.6% and liquid fraction 15.5%/h ; these parameters were not affected by the protein source in the diet.

The chemical and amino acid composition of the empty bodies of 4 lambs slaughtered before fattening and of 12 lambs from 3 gropus (4 in each group) fattened for 113 day with a diet containing 17 (H), 14 (M) or 11%(L) crude protein were determined. The amount of nitrogen and individual amino acids apparently absorbed in the smali intestine during fattening was calculated on the basis of data on their passage to the duodenum and digestibility in the smali intestine. No differences were found in empty body composition depending on the protein content of the diet. The mean daily deposition of protein in the empty body was: 29.7,31.4 and 27.3 g in groups H, M and L, respectively. The utilization of protein for deposition into the empty body weihgt rose (P<0.01) from about 18 to 27% when the protein content was decreased from 17 to 11%. The utilization of metabolic energy available for growth (Ki) was best in group M and amounted to 0.41 in comparison with 0.38 and 0.33 in groups H and L, respectively. The lowering of the protein level in the diets improved the efficiency of utilization of amino acids absorbed in the smali intestine for their deposition in the empty body weight. Essential amino acids and semi-essential amino acids were best utilized by lambs from group M. From all of the amino acids, cystine and glycine were utilized best, with cystine being utilized better in groups H and M than in L. Reducing the protein content in group L to about 11 % resulted in decreasing the percentage of essential amino acids in protein deposited in the body, especially in comparison with the group fed diet M.It seems that the most effective utilization of protein takes place at a 14% crude protein content in the diet.

The aim of the study was to evaluate the infl uence of feeding different protein levels (11.4, 13.3 and 16.9%) in diets for goats on the fatty acid (FA) profi le in milk. The experimental design was 3 × 3 Latin square. Each 22-day experimental period consisted of 14 days adaptation to the diets and 8 days for milk sample collection. Separation of methylated FAs was achieved using GLC. Milk production was nearly the same when the low-and medium-protein diets were fed, while the highprotein diet resulted in a tendency to increase milk production. The concentrations of total saturated fatty acids (SFA) were similar in milk from goats fed the diets containing low-and medium-protein contents, while the diet containing the highest content of protein resulted in a slight increase in the concentration and daily production of SFA milk. The concentration and daily production of monounsaturated fatty acids, CLA isomers, other polyunsaturated fatty acids and the sum of FAs in milk increased as the dietary protein level rose. The highest dietary protein content resulted in an increase in the Δ9-desaturase index.