1. Infusions of histidine into the carotid arteries of cockerels receiving a histidine-limiting, imbalanced diet caused an increase in food intake, whereas similar infusions into the jugular veins did not.

2. Infusions of lysine into the carotid arteries or jugular veins of young cockerels receiving a balanced, low-protein diet caused decreases in food intake. There was evidence of a more marked effect of carotid infusion.

3. The mechanisms of food intake regulation by amino acids in mammals are applicable to birds and excesses of single amino acids do seem to affect food intake directly.

1. Squid meal (SqM), produced by grinding and drying the whole squid (Illex illecebrosus) common to the northeast Atlantic and Mediterranean, contained 645 g protein/kg and appeared limiting with respect to lysine, methionine and cystine.

2. Although a comparison of the essential amino acid profiles of SqM with other protein concentrates indicated that SqM was higher than fish meal andsoya-beanmeal but lower than casein or whole-egg protein, these tests could not accurately predict protein quality.

3. A new approach is reported for evaluating protein quality of SqM. It was based on the direct chromato-graphic determination of its collagen content, from the amounts of 5-hydroxylysine or 5-hydroxyproline present, and elastin, from the amounts of desmosine or iso-desmosine present. This method can alsobe routinely used to assess the connective tissue content and protein quality of animal protein supplements such as fish, meat-and-bone meals.

4. A nutritional evaluation of SqM as a source of protein for poultry was carried out using 320 male and 320 female Cobb chicks fed from I-d-old to 48 d, a control diet containing 50 g/kg fish meal or test diets containing 50 g, 100 g or 150 g SqM/kg.

5. Feeding of SqM at a rate of up to IOO g/kg diet resulted in optimum biological response and monetary returns.

1. Effects of feeding liquid milk-substitute to young calves either by nipple-pail or open-bucket on the rumen by-pass and on the rate of passage were studied.

2.Sixteen Holstein calves, aged 1 week initially, were used in three experiments in which calves were slaughtered after they were given liquids (milk-substitute and water) containing chromic oxide and SrCl2 6H2O as a tracer either by the nipple- or bucket-feeding method, and the distribution of tracers to the rumen, abomasum and the lower alimentary tracts was examined.

3.When the liquid milk-substitute containing tracers was given by the nipple- or bucket-feeding method to calves having been trained to the corresponding procedures for the preceding 1 week, most of the tracers was directed into the omasum and abomasum. There seemed no difference in the functioning of oesophageal groove closure between the two feeding procedures. Even when the liquid milk-substitute containing tracers was given by the nipple-or bucket-feeding method to calves which had been accustomed to different procedures for the preceding week, the majority of tracers were found in the abomasum immediately after administration, though a slightly greater proportion of the tracers entered the reticulo-rumen.

4.Continuing bucket feeding of liquid milk-substitute effected an efficient closure of the oesophageal groove at least up to 16 weeks of age. After calves were accustomed to consume liquid milk-substitute from the bucket from 1 to 4 weeks of age, drinking warm water from the bucket also caused efficient closure at least up to 16 weeks of age.

When tracers were administered with warm water, Cr2O3 and strontium, especially the latter, transferred much more rapidly to the lower gut than when they were administered with liquid milk-substitute, probably reflecting the curd formation of the milk-substitute in the abomasum. When liquid milk-substitute with tracers was fed by the bucket-feeding method, Sr transferred more rapidly to the lower gut than when the milk-substitute was fed by the nipple-feeding method, indicating that the feeding procedure of liquid milk-substitute has an apparent effect on the rate of passage.

1. RNA was administered to rats as part of a meal while standardizing food intake and minimizing the effects of psychological stress and diurnal metabolic rhythms. It was demonstrated that circulating levels of glucose and free fatty acids (FFA) in the animals, which were deprived of food for 48 h, were responsive to orally administered caffeine.

2. Inclusion of RNA in the diet slightly but consistently reduced the normal postprandial hyperglycaemia. Its effect on plasma FFA was variable although statistically significant in some experiments. The differences between RNA- and control-fed animals were not attributable to differences in the rate of passage of digesta along the gastrointestinal tract.

3. Evidence was obtained that the variability in the FFA response was related to a seasonally-dependent change in the state of the animals. The synchronizer (‘Zeitgeber’) responsible for this change was not identified and no satisfactory way of suppressing its effect was found.

4. The present findings, taken in conjunction with those of previous workers, suggest that there is a seasonal influence on the sympathetic nervous system manifesting itself as a variable susceptibility to arousal or excitation.

1. Two young Friesian steers fitted with rumen cannulas were each given three different isonitrogenous and isoenergetic diets for successive periods of 2–3 weeks. The diets consisted mainly of straw and tapioca, with the nitrogen supplied mainly as decorticated groundnut meal (DCGM; diet A), in approximately equal amounts of DCGM and urea (diet B), or entirely as urea (diet C).

2. At the end of each period on a given diet, part of the dietary urea of a morning feed was replaced by a solution of [15N]urea which was infused into the rumen. Samples of rumen contents were removed just before giving the 15N dose and at 1, 3, 5, 7 and 24 h afterwards, concentrations of ammonia and its 15N enrichment were determined and samples of mixed bacteria were prepared. Amino acids, ammonia derived mainly from amide groups, and hexosamines were prepared by ion-exchange chromatography of acid-hydrolysates of the bacteria and analysed for 15N.

3. Approximate estimates of net bacterial N synthesis were made from turnover data for rumen fluid and 15N enrichments in rumen fractions. From the determined efficiency of incorporation of urea-N into bacteria recovered at the duodenum, it was calculated that on diets A, B and C respectively 82%, 37% and 0% of the bacterial N was derived from dietary protein or other non-urea sources.

4. [15N]urea was converted rapidly to ammonia and the 15N then incorporated into bacterial amide-N; it appeared at a slower rate in total bacterial non-amide-N. Rates of incorporation into non-amide-N were highest for glutamic acid, aspartic acid and alanine, and generally lowest for proline (pro), histidine (his), phenylalanine (phe), arginine (arg), methionine (met) and galactosamine. A similar ranking was also generally observed for relative 15N abundances (15N atoms %excess in N component ÷ 15N atoms % excess in total bacterial N) achieved after several hours. Relative 15N abundances in his, arg and pro increased with decreasing protein (DCGM) in the diet but those in the other protein amino acids, including the poorly labelled met phe (and its derivative tyrosine) did not.

5. It was concluded that different extents of labelling of the amino acids (at least those present mainly in protein) indicated that different amounts of preformed units (amino acids or peptides) were used. When an adequate supply of such units was available (particularly on diet A) pro, arg, his, met and phe were derived in this way to a greater extent than the other amino acids, but whereas synthesis of pro, arg and his increased on the low-protein diet C, that of met and phe did not. Thus met and phe may be limiting for bacterial growth on diets low in protein and high in non-protein-N.

6. Differences in the extent of labelling of other bacterial N components may be due to different turnover rates.

1. Studies have been performed on the body composition, the fat distribution, the fat cell size, and the ‘observable’ fat cell number of a new obese mutant, the Adipose (Ad) mouse. The serum glucose and insulin concentrations have also been investigated. All studies were undertaken with animals aged 6 months.

2. The obese animals weighed over 50% more than the lean, but there was no difference in the body or tail lengths.

3. The obese animals had an increase in the weight of the liver, but the increase was only proporational to the increase in the total body-weight.

4. The carcasses of the obese mice contained more water as well as more fat than those of the lean. In the males the fat content was 3.9 times greater, while in the females it was increased by 5.5 times.

5. The nitrogen content of the defatted dry carcass was the same in both lean and obese animals but the total body protein was higher in the obese.

6. Fat was dissected from four major depots, gonadal, abdominal, hind subcutaneous and interscapular subcutaneous (including brown adipose tissue), and each was substantially larger in the obese animals. This indicated that the additional fat of the AAd mouse was not localized to any particular site.

7. In Ad males there was no over-all increase in the observed number of adipocytes, all the extra fat being accommodated by an increase in fat cell size (3.8 times). However, in Ad females there was a 3.3-fold increase in the number of observable fat cells as well as a 2.2-fold increase in fat cell size.

8. Non-fasted obese animals were not hyperglycaemic, but there was a 5.3-fold increase in the concentration of serum insulin. Hyperinsulinemia in the presence of normoglycaemia suggested that the obese animals were insulin resistant.

1. Total body energy retention (ER) and metabolizable energy intake (MEI) values from experiments with 231 lambs (Suffolk ♂× (Border Leicester ♂× Cheviot ♀) ♀) housed indoors and given thirteen forage diets were used to estimate the metabolizable energy (ME) required for maintenance.

2. ER was measured using the comparative slaughter technique, and the lambs were fed at several planes of nutrition above maintenance between 2 and 5 months of age.

3. The daily ER and MEI results were scaled to live weight (kg0.75) and linear regression lines fitted to the values for individual diets. Extrapolation of the fitted lines to zero ER gave estimates of maintenance requirement ranging from 141 to 466 kJ ME/kg0.75 per d and values for the efficiency of utilization of ME for growth and fattening (kf) of 0.25–0.53 (mean 0.39).

4. An alternative analysis constrained the estimated maintenance requirement to be the same for all diets. An iterative search procedure indicated minimal residual variation at 339 kJ/kg0.75 per d. This common value of ME for maintenance gave kf values ranging from 0.30 to 0.54 (mean 0.39).

5. The implications of the technique were considered togethe with some discussion of the variability of the estimate. Allowing the minimum RSD to vary by 10% gave a maintenance requirement of between 231 and 408 kJ/kg0.75 per d.