Utilization of ileal digestible amino acids by pigs: Lysine

Abstract

Two experiments were conducted to determine the utilization of ileal digestible lysine by pigs. In the first, the apparent ileal digestibility of amino acids in cottonseed meal, meat-and-bone meal and soya-bean meal was determined in pigs fitted with 'T'-shaped cannulas. In the second experiment, three lysinedeficient diets were formulated to 0.36 g ileal digestible lysine/MJ digestible energy (DE), with lysine contributed from the three protein concentrates as the only source of lysine in sugar-based diets. An additional three diets were formulated with supplements of lysine to verify that lysine was limiting in the first three diets. The growth performance and retention of lysine by pigs given the six diets over the 20-45 kg growth phase were then determined. The apparent ileal digestibility of lysine in the three protein concentrates (proportion of total) was : cottonseed meal 0.74, meat-and-bone meal 0.78, soyabean meal 0.89. Growth rates (g/d) of the pigs given the three diets formulated to 0.36 g ileal digestible lysine/MJ DE were significantly different (P < 0001): cottonseed meal 377, meat-and-bone meal 492, soya-bean meal 541. The response of pigs to the addition of lysine confirmed that lysine was limiting in these diets. Crude protein (nitrogen x 6.25) deposited by the pigs was significantly higher (P < 0.001) for those given soya-bean meal (77 g/d), relative to meat-and-bone meal (66 g/d) and cottonseed meal (38 g/d). The proportion of ileal digestible lysine retained by pigs given the three protein concentrates was: cottonseed meal 0.36, meat-and-bone meal 0.60, soya-bean meal 0.75. The results indicate that values for the ileal digestibility of lysine in protein concentrates are unsuitable in dietary formulations as the assay does not reflect the proportion of lysine that can be utilized by the pig. It appears that, with heat-processed meals, a considerable proportion of the lysine is absorbed in a form(s) that is (are) inefficiently utilized. Interest has centred on the use of the ileal digestibility assay to estimate amino acid availability. This assay has the advantage that the digestibility of all amino acids can be assessed at the same time and only small numbers of pigs are required per assay. The assumption is made that, if an amino acid is not recovered at the terminal ileum, then it has been absorbed in a form that can be utilized by the pig. With weaner pigs, Leibholz (1985) reported that the retention of apparently absorbed lysine at the terminal ileum was 0.860.94 for five diets containing different protein sources, and suggested that the apparent digestibility of lysine could be used to predict lysine availability.However, in a previous study (Batterham et al. 1990a), there was close agreement between ileal digestibility and lysine availability in soya-bean meal (0.89, 0.90 respectively) but not for cottonseed meal (0.58-0.72 ileal digestibility, 0.274-30 lysine availability). Formulating diets containing cottonseed or soya-bean meals on an available lysine basis

Utilization of ileal digestible amino acids by growing pigs: methionine

“…A similar effect was reported with lysine (Batterham et al 1990~). Overall, the levels of methionine in the protein of the pigs given the methionine-deficient diets were lower than those reported in the literature for young or weaner pigs given a variety of diets (1.97-2.59 g/16 g N, Wilson & Leibholz, 1981 ; 1.62-1.87, Zhang et al 1986;1.80-194, Campbell et al 1988) and for grower pigs (1.67-2.07, Batterham et al 1990b).…”

Utilization of ileal digestible amino acids by growing pigs: tryptophan

“…A similar finding was found for lysine (Batterham et al 1990a), threonine (Beech et al 1991 and methionine (Batterham et al 1993). This confirms that during heat processing the changes to the protein molecule appear to be between different amino acids, rather than specific reactions between basic amino acids, such as lysine and carbonyl compounds of reducing sugars (Maillard reactions).…”

“…These results are unusual in that in previous experiments with the same batches of protein concentrates performance had always been greater in pigs given diets containing soya-bean meal relative to meat-and-bone meal, when the diets have been formulated to similar ileal digestible lysine (Batterham et al 1990a), threonine (Beech et al 1991) and methionine (Batterham et al 1993) contents. It seems unlikely that tryptophan would have a relatively lower availability than the previously mentioned amino acids in soya-bean meal and/or a relatively higher availability in meat-and-bone meal.…”

“…The ileal digestibility of amino acids in the three protein concentrates was determined previously with pigs fitted with T-shaped cannulas and the results reported by Batterham et al (1990a). In that work the ileal digestibility of tryptophan was determined using two different analytical procedures to determine tryptophan in the food and digesta.…”

“…However, values for the ileal digestibility of lysine, threonine and methionine have been shown to be unsuitable for formulating diets in certain heatprocessed protein concentrates, as a considerable portion of these amino acids appear to be absorbed in a form(s) that is (are) inefficiently utilized (Batterham et al 1990a(Batterham et al , 1993 Beech et al 1991). It appears that ileal digestibility values for these amino acids overestimate availability in heat-processed meals.…”