The artificial fibre bag technique was evaluated for assessing the proportions of dietary D. M. and N which disappear in the rumen. The most important factor determining the variability in disappearance from bags incubated together was the sample size in relation to bag size. For incubation of 5 g air dry feed, a bag size of 17 ✗ 9 cm was found to be adequate. There were also variations in substrate disappearance between animals and between days of incubation. It was estimated that three sheep and the measurement of substrate disappearance twice were necessary in order to obtain acceptable repeatability.The technique was found to be satisfactory as a simple and rapid guide for measuring nutrients disappearance in the rumen such as protein degradation and carbohydrate fermentation. It has been used in subsequent work to measure the effect of features of the rumen environment, such as pH and NH3 concentration, on rate of fermentation.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0021859600037321

A study of artificial fibre bag technique for determining the dig estibility of feeds in the rumen

An automated technique has been developed for estimating NH4+ in Kjeldahl digests of crops, using the salicylate-dichloroisocyanurate reaction in the presence of nitroprusside. The method gives reproducible results in close agreement with those from conventional distillation and titration, and there is a marked improvement in output.

Determination of ammonium in Kjeldahl digests of crops by an automated procedure

1. Four sheep were fed from automatic continuous feeders on whole barley fortified with graded levels of a urea solution. This approach was to a large extent successful in maintaining relatively steady states of rumen ammonia concentration. 2. Rates of barley fermentation in the rumen at various rumen NH3 concentrations were assessed by measuring the disappearance of barley dry matter from polyester bags suspended in the rumen of these sheep. 3. The minimal NH3 concentration for maximal rate of fermentation was estimated as 235 mg/l rumen fluid.

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Rates of rumen fermentation in relation to ammonia concentration

A series of four nitrogen-balance experiments was carried out with growing pigs to determine the optimum balance amongst the amino acids in the diet. The reduction in N retention when 20 % of a single amino acid was removed from the diet was used to calculate a dietary amino acid pattern in which each amino acid would he equally limiting. A mixture of amino acids simulating the amino acid pattern of casein was used with the same efficiency as casein. From two successive deletion experiments an optimum balance amongst the essential amino acids was derived. Expressed relative to lysine = 100 this had threonine 72, valine 75, methionine + cystine 63, isoleucine 60, leucine 110, phenylalanine + tryosine 120, tryptophan 18. No estimate was made for histidine. Essential amino acids in this pattern were mixed with non-essential amino acids in ratios of 36:64 up to 57:43. The highest efficiency of N retention was achieved with diets having a ratio of at least 45:55. This included (g/16 g N) lysine 6 5, threonine 4.7, valine 4 9, methionine + cystine 4.1, isoleucine 3 9, leucine 7.2, phenylalanine + tyrosine 7.8, tryptophan 12. The N of diets with this amino acid pattern was utilized significantly better than when the pattern proposed by the Agricultural Research Council (1981) was used. The flow of amino acids past the terminal ileum of pigs given the semi-synthetic diet with this amino acid pattern was no greater than that observed with protein-free diets. The proposed pattern thus describes the intrinsic requirements of the growing pig for absorbed amino acids.

/pdf/the-optimum-dietary-amino-acid-pattern-for-growing-pigs-1-36zlxpq7lc.pdf

The optimum dietary amino acid pattern for growing pigs. 1. Experiments by amino acid deletion.

Two experiments were carried out to determine endogenous excretion of purine derivatives in steers and lambs, and to investigate the relationship between microbial nucleic acid input and urinary excretion of purine nitrogen. The endogenous excretion of allantoin after conversion of hypoxanthine, xanthine and uric acid to allantoin, was calculated to be 72 and 26 mg/kg W 0·75 per day in steers and lambs, respectively, when the dietary protein contained no nucleic acid nitrogen. The excretion of purine derivatives increased linearly with increasing microbial nucleic acid input in lambs. The excretion of purine derivatives in excess of endogenous contribution was closely related to the theoretically expected values. The average recovery was calculated as 0·96 for one sheep and 1·0 for the other.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0021859600080916

The effect of protein infusion on urinary excretion of purine derivatives in ruminants nourished by intragastric nutrition

An account is given of the development of a system making maximum use of automated equipment in the routine determination of nitrogen in biological samples when the desired order of precision is better than 1 per cent. and the expected number of analyses is greater than 100 per day.An automatic digestion unit made by Technicon Instruments Company Ltd. tested for liquids did not achieve the accuracy desired. Results for biological fluids with this digestor tended to be low on occasion by up to 5 per cent. Recovery of nitrogen from solutions of the pure compounds creatine and arginine was as low as 70 per cent. and alterations in the digestion mixture and digestor heating conditions did not materially improve recovery. For this reason all samples were subsequently digested by a standard Kjeldahl method before automated determination of ammonia in the diluted digests.Studies were made of the indophenol-blue reaction used in the automated system for determining ammonia in aqueous solution. Conditions were most stable when the reaction coil was maintained at 22°± 1° C and dwell time in the coil was about 3 minutes. Effects of mineral content of test solutions, sampling rate and sampler cam irregularities on the reliability of results were investigated.Results for nitrogen determined in acid digests by the automated procedure and by a standard distillation method showed close agreement.The use of an I.B.M. 1130 computer allowed calculation of results to be carried out in half the time taken when using an electronic desk calculator.

The use of automation in determining nitrogen by the Kjeldahl method, with final calculations by computer

1
Measurements were made of the iodine value (IV) of fat from seven sites on pigs which had been kept at 5, 13 or 23 oC during their growth from 20 to 90 kg. At each temperature the pigs were given one of three levels of daily food intake.

2
The IV of the outer back fat exceeded that of the inner by 7.7 units at the shoulder, 6.8 units at the midback and 2.4 units at the rump.

3
Increasing daily food intake significantly depressed the IV of fat only at the shoulder sites.

4
The IV of fat at all sites fell with increasing temperature by an amount ranging from 0.22 units per 1 oC at the midback to 0.55 units per 1 oC in the inner shoulder fat. The IV of perinephric fat fell by 0.39 units per 1 oC increase in temperature; that this fat was thus affected suggests that the effect of environmental temperature on fat composition is not conditioned by its effect on local tissue temperature.

5
It was calculated that these effects arose largely by changes in the proportions of fatty acids synthesized de novo; the exogenous fat consumed could have made only a small contribution.

Effect of environmental temperature on the degree of unsaturation of depot fats of pigs given different amounts of food.

Young pigs weighing between 25 and 50 lb. live-weight were fed diets consisting of cereals and groundnut meal alone, or with additions of L-lysine monohydrochloride, or DL-methionine, or both. Nitrogen retention was measured over 5-day-periods, and a highly significant increase was obtained with the L-lysine supplement at all levels of crude protein. Groundnut + lysine diets were as good as white fish meal diets, providing similar total lysine levels when the protein level was 12 or 15%, but were inferior at 18 and 21% crude protein. No significant response was obtained to DL-methionine except at 18% crude protein, when it depressed nitrogen retention. The greatest nitrogen retentions were obtained either at 18% or 21% of dietary crude protein.

The nitrogen metabolism of the young pig. I.—supplemental value of certain amino–acids when added to groundnut meal rations

In three experiments each involving 16 groups of 12 birds, diets having normal to low ratios of crude protein to metabolisable energy were fed, for the first 12 weeks of life, to cockerels of a Rhode Island Red X Light Sussex cross and a modern commercial fast-growing hybrid. Dietary ratios of crude protein to metabolisable energy were lowered by adding either maize starch or animal fat to a diet which was based on cereals and was, by calculation, adequate in all known nutrients. The efficiency with which metabolisable energy was converted to tissue energy was assessed by a carcass analysis technique which also allowed a study of the effect of diet on body composition.



In both strains of bird, diets in which the ratios of crude protein to metabolisable energy had been lowered considerably below that corresponding to the 20% protein and 2.9 Mcal. metabolisable energy per kg. recommended by the (U.S.A.) National Research Council, gave rise to a greater metabolisable energy intake and greater loss of this energy, mainly as heat, per unit of live body weight. Deposition of body fat was also greater than in birds fed normal diets. The relative importance of heat loss to the environment and deposition of body fat, for disposal of excess energy ingested through overeating to compensate for inadequate concentrations of amino-acids in the diet, may be influenced by breed and the proportion of fat in the diet. No significant differences were found among diets in the percentage utilisation of dietary metabolisable energy for tissue energy production and it may be that the differences found between strains arise solely from differences in dietary energy intake. Whatever the diet, the modern fast-growing type of bird consumed more feed and therefore energy and made about 30% greater live-weight gain with about 40% greater tissue energy gain over 12 weeks than the Rhode Island Red X Light Sussex type.

Effects of animal fat and of low ratios of protein to metabolisable energy on the utilisation of dietary energy by medium- and fast-growing strains of poultry

An account is given of the development of a logging system for acquiring data on punched tape from two amino-acid analysers running at different speeds. The outputs of the analysers were sampled in such a way that a visual record of the progress of each separation was retained. A method of programming the computer to edit and process the data is outlined. Results obtained from the computer showed good agreement, both within analytical systems and between systems. Manual calculations from recorder charts, made by use of the time-consuming manual method, agreed well with the computer results from punched tape and cards. Problems encountered during the period of development are discussed.

A. W. Boyne

Papers

The use of automation in determining nitrogen by the Kjeldahl method, with final calculations by computer

Effect of environmental temperature on the degree of unsaturation of depot fats of pigs given different amounts of food.

The nitrogen metabolism of the young pig. I.—supplemental value of certain amino–acids when added to groundnut meal rations

Effects of animal fat and of low ratios of protein to metabolisable energy on the utilisation of dietary energy by medium- and fast-growing strains of poultry

The simultaneous collection of data from two automated amino-acid analysers and processing of the data by computer