Downloaded from British Journal of Nutrition (1989), 62, 17-89 77 https://www.cambridge.org/core The optimum dietary amino acid pattern for growing pigs 1. Experiments by amino acid deletion BY T. C. WANG AND M. F. FULLER Rowett Research Institute, Bucksburn, Aberdeen AB2 9SB . IP address: (Received 16 August 1988 ~ Accepted 20 January 1989) A series of four nitrogen-balance experiments was carried out with growing pigs to determine the 170.106.33.19 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 , on balance amongst the essential amino acids was derived. Expressed relative to lysine = 100 this had 26 Sep 2021 at 00:16:26 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 , subject to the Cambridge Core terms of use, available at 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. Amino acids: Protein quality: Pig. The quality of dietary protein is determined by its content of amino acids, and by their digestibility and availability. Quality can be considered as the degree to which the composition of the absorbed amino acid mixture accords with the balance required by the animal. An optimum (or ideal) amino acid pattern is needed as a standard profile or reference protein when evaluating the quality of other dietary proteins. Since the nitrogen of essential amino acids can also be used in the synthesis of non-essential amino acids, a protein with essential amino acids in surplus relative to the non-essential amino acids may still support https://www.cambridge.org/core/terms maximum N retention (NR). A more restricted definition of an ideal protein is one which includes the minimum quantity of each essential amino acid compatible with maximum utilization of the protein as a whole. The question of the dietary amino acid pattern required by growing pigs has been reviewed in the past few years (Cole, 1978; Fuller, 1978; Cole et al. 1980; Henry, 1980; Low, 1980; Agricultural Research Council, 1981 ; Fuller & Chamberlain, 1982; Wiesemuller, 1983; Yen et al. 1986). The experiments described here were designed to answer the question ‘what is the optimum dietary amino acid balance for growing pigs?’. The optimum dietary amino acid profile is considered to be that which, for a given N intake . (NI), results in the highest NR. https://doi.org/10.1079/BJN19890009 The method used is an extension of that published by Bender (1965) with rats. It is based on the concept that the removal of a non-limiting amino acid has no effect on NR. The changes in NR on removing a proportion of each amino acid in turn were used to calculate a dietary amino acid pattern in which all the amino acids were equally limiting. Downloaded from 78 T. C. WANG AND M. F. FULLER Table 1. Expt 1. Composition (glkg) of diets https://www.cambridge.org/core Diet ... (1) (2) (3) (4) (5) Low-casein High-casein Low-casein Low-casein (low-control) (high-control) + AA + EAA Protein-free Amino acid (AA) - ~ 28.59* 13.53t - mixture Casein 128.65 160.82 128.65 128.65 - Maize starch 280.00 265.00 265.06 274.12 300.00 Glucose 297.65 280.48 284.00 29000 300.00 . IP address: Sucrose 137.00 137.00 137.00 137.00 150~00 Cellulose 60.00 60.00 6000 6000 60.00 Vegetable oil 40.00 40.00 40.00 40.00 40.00 Mineral-vitamin 56.70 56.70 56.70 56.70 56.70 170.106.33.19 premix1 Nitrogen (g/kg) 17.60 22.00 20.98 19.21 0.2 1 DE (MJ/kg) 14.10 14.09 14.09 14.09 12.75 -~ , on . .. ~ . .. ~~.~_____~~ EAA, essential amino acids; AA, amino acids; DE, digestible energy. 26 Sep 2021 at 00:16:26 * Containing (g): aspartate 2.3 19, threonine 1.076, serine 1.469, glutamate 5.637, proline 3.174, glycine 0-492, alanine 0.754, valine 1,458, cystine 0,130, methionine 0.591, isoleucine 1.183, Ieucine 2.349, tyrosine 1-485, phenyialanine 1.351, lysine 2-527, histidine, 1.029, arginine 1.2 14, tryptophan 0358. t As for *, but omitting aspartate, serine, glutamate, proline, glycine, alanine and arginine. 1 Supplying (per tonne) : retinol 1.5 g, cholecalciferol 25 mg, a-tocopherol acetate 5 g, phytylmenenaquinone 1 g, thiamin 2 g, riboflavin 3.4 g, nicotinic acid 19 g, pyridoxine 2.73 g, vitamin B,, 21 mg, choline chloride 1150 g, pantothenic acid 12 g, biotin 50 mg, folk acid 2 g, ascorbic acid 12 g, salt 3.5 kg, dicalcium phosphate , subject to the Cambridge Core terms of use, available at 40 kg, potassium bicarbonate 7 kg, iron 80 g, zinc 100 g, manganese 40 g, magnesium 420 g, copper 150 g, iodine 2 g, cobalt 0.5 g, selenium 0.15 g. MATERIALS AND METHODS There were four N balance trials for which, except where otherwise indicated, the experimental procedure was the same. In Expt 5 the digestibilities of amino acids in the experimental diet were estimated. Animals In Expts I, 2,3 and 4, the number of gilts used was eighteen, twenty-four, twenty and twenty respectively. Their starting weights were 25-30 kg and their finishing weights 45-50 kg. All were Large White x (Landrace x Large White) from the Rowett Institute herd. Housing and cages https://www.cambridge.org/core/terms At 7 d before the first urine collection the pigs were moved into metabolism cages to adjust to their new environment. The room temperature was controlled at 22-24'. Water was supplied ad lib. through nipple drinkers. Experimental diets Expt 1. Of the N in casein 20% was replaced by synthetic amino acids in the same proportions as in casein to confirm that the free amino acids used in this way gave a similar rate of NR to intact protein. The diets used in Expt 1 are shown in Table I. At the end of the measurement period all animals were fed on a protein-free diet for 11 d (4 d adjustment . and 7 d collection of urine and faeces) to measure the obligatory N losses. https://doi.org/10.1079/BJN19890009 Expt 2. Casein protein was used to provide the control amino acid pattern. The diets supplied 1.4 g N/kg body-weight (BW)"" per d in the high-control diet (treatment 1) and 1.05 g N/kg BW" 75 per d in the low-control diet (treatment 12). To provide diets in which Downloaded from IDEAL PROTEIN FOR GROWING PIGS 79 Table 2. Expt 2. Composition (glkg) of diets* https://www.cambridge.org/core Diet.. (1) (2) (3) (4) (5) (6) High- Methionine t control Threonine Valine cystine Isoleucine Leucine Amino acid mixture 0 26.61 26.68 26.42 26.52 26.21 Casein 110.91 83.18 83.18 83.18 83.18 83.18 Maize starch 297.39 298.51 29844 298.70 298.60 298.91 Glucose 300.00 300.00 300.00 300.00 30000 300.00 Sucrose 130.00 130.00 130.00 130.00 130.00 130.00 . IP address: Cellulose 65.00 65.00 65.00 65.00 65.00 65.00 Vegetable oil 40.00 40.00 40.00 40.00 40.00 40.00 Mineral-vitamin 56.70 56.70 56.70 56.70 56.70 56.70 premix? 170.106.33.19 Nitrogen (g/kg) 15.17 14.54 14.55 14.54 1454 14.52 DE (MJ/kg) 14.1 1 14.1 1 14.1 1 14.1 1 14.1 1 14. I 1 (9) (10) (1 1) (12) , on Non- 26 Sep 2021 at 00:16:26 Phenylalanine + essential Low- tyrosine Lysine Histidine Tryptophan amino acids control Amino acid mixture 41.52 27.53 27.38 26.59 11.74 0 Casein 66.55 83.18 83.18 83.18 83.18 83.18 Maize starch 300.23 297.59 297.74 298.53 3 13.38 325.12 Glucose 300.00 300.00 300.00 300.00 300.00 30000 130.00 Sucrose 130.00 130.00 I30.00 13000 130.00 , subject to the Cambridge Core terms of use, available at Cellulose 65.00 65.00 65.00 65.00 65.00 65.00 Vegetable oil 40.00 40.00 40.00 4000 40.00 40.00 Mineral-vitamin 56.70 56.70 56.70 56.70 56.70 56.70 premix? N (g/kg) 14.18 14.48 14.51 14.54 12.90 11.50 DE (MJ/kg) 14.11 14.1 1 14.1 1 14.1 1 14.13 14.14 DE, digestible energy.