Availability of lysine in protein concentrates as determined by the slope-ratio assay with growing pigs and rats and by chemical techniques

Abstract

I . A slope-ratio assay was developed with growing pigs to determine the availability of lysine in five protein concentrates. The basal diet contained 5.2 g lysine/kg and six levels of lysine, in 500 mg/kg increments, were used to determine the pig's response to standard lysine. The protein concentrates were incorporated into the basal diet to provide five levels of total lysine, again in 500 mg/kg increments, at the expense of wheat starch. A daily feeding scale based on live weight was used to ensure similar nutrient intakes. Pigs were fed at three-hourly intervals to ensure the utilization of free amino acids in the diets. Four pigs were allotted to each dose level and response was assessed over the 20-45 kg growth phase.2. Potency estimates for available lysine in the five protein concentrates varied, depending on whether live-weight gain or carcass gain was used as the criterion of response. Carcass gain was considered more appropriate as it was not influenced by variation in gut fill. Availability of lysine in the five proteins, using carcass gain/d were (proportion of total) cottonseed meal 0'39, fish meal 0.89, meat-and-bone meal 0.50, skim-milk powder 0.88 and soya-bean meal 0.87.3. Rat slope-ratio assay results for available lysine in the five protein concentrates were in general agreement with those from the pigs. In contrast, thedifferences in available lysinewere not detected by thechemical Previous work (Batterham et al. 1978) showed that for growing pigs, the content of available lysine in locally produced cottonseed meal, two meat meals and sunflower meal was approximately 60% less than that in rapeseed meal, skim-milk powder and soya-bean meal. Similar differences were detected with a slope-ratio assay with rats but not with the chemical Silcock available-lysine assay as developed by Roach et al. (1967). In view of these differences, it seemed appropriate to attempt to quantify the available lysine content of the major protein concentrates for pigs and to evaluate the efficiency of some of the different techniques for estimating available lysine. This paper reports the results of a slope-ratio assay that was developed with growing pigs to determine the availability of lysine in five protein concentrates. Lysine availability in these proteins was also estimated by a slope-ratio assay with rats, the Silcock available-lysine technique and by ihe direct fluorodinitrobenzene (FDNB)-available-lysine assay (Carpenter, 1960).Pig slope-ratio assay Diets. For the pig assay, five protein concentrates were assayed in the one experiment. This involved the use of thirty-two diets; the basal diet (blanks), six diets to determine the pig's response to standard lysine and twenty-five for the five protein concentrates (five/ protein concentrate). The basal diet contained (g/kg) : wheat 730, wheat gluten 50, L-lysine monohydrochloride (anhydrous) I .03, DL-methionine 0.30, L-threonine 0.70, mineral and vitamin premix 5, bone flour 30, and starch 182.97 (Table I). The wheat was a high-protein

Availability and Utilization of Amino Acids for Growing Pigs

“…A growth assay has been developed and used for assessing the availability of lysine in major protein concentrates for growing pigs (Batterham et al 1979(Batterham et al , 1984. The features of this assay are as follows.…”

Variability of amino acid digestibility in pigs: inherent factors in feedstuffs and considerations in methodology

“…Defined as such, availability is an abstract concept, which can not be really measured but only estimated. The growth assay (slope-ratio assay) is the most direct approach to assess the biological availability of amino acids in feedstuffs (e.g., Batterham et al, 1979). Availability values of amino acids, primarily of lysine, have been estimated with the growth assay for various protein supplements in growing pigs (Knabe, 1991;Batterham, 1992).…”

Offal meal as a protein supplement to cereal-based diets for growing pigs

“…It is generally recognised that the availability of amino acids in meat and bone meals is low compared with other traditional protein supplements (Batterham et al 1979;Tanksley & Knabe 1980) and the same may be so with offal meals which are also subjected to heat during processing. It should be noted that the OFM did not replace the meat and bone fraction in the present series of diets with the result that at the 12% level of OFM some 50% of the total crude protein came from a combination of the 2 meatworks protein supplements.…”