Use of low-test-weight corn in swine diets and the lysine/protein relationship in corn

weight resulted in a slight reduction in the true metabolizable energy content of corn.! Since corn's primary contribution to swine diets is energy, we generally think that low-test-weight corn is of lower feeding value than normal-test-weight corn. However, the 1992 corn crop did not exhibit nutrient content typical of lowtest-weight corn. Field observations failed to demonstrate a consistent relationship between test weight and the crude protein or lysine content of corn. This inconsistent relationship and the recent prevalence of low-test-weight corn has led several research groups to question the previously held notion that low-test-weight corn was of lower feeding value for pigs compared with normaltest-weight corn. This paper will examine the effect of low-testweight corn on pig performance and the relationship between lysine and crude protein in corn. Summary: Poorgrowingconditionsthroughoutthe cornbelt in recent years have produced a high proportion of low-testweight (bulk density) corn. Nutritionists expect low-testweight corn to be higher in protein and lower in energy compared with corn of normal test weight (72 kg per hI;56 Ib per bu). Recently, several research groups have evaluated the effect of low-test-weight corn on performance of growingfinishing pigs. Researchers at South Dakota State University reported an inverse relationshiP between the test weight of corn and digestibility of protein and dry matter with no effect on digestibility of acid detergent fiber (ADF)and neutral detergent fiber (NDF).In a companion study, daily weight gain was not different between pigs fed low (59 kg per hI;46 Ib per bu) compared with normal test weight corn. Four additional studies have reported no detrimental effects on growth performance of pigs when corn with test weight as low as 40 Ib per bu was fed. No studies have investigated the effects of low-test-weight corn on performance of breeding swine. Assuming that mycotoxins and such factors as molds and overheating are not compromising corn quality, low-test-weight corn seems to be comparable in feeding value to normal-test-weight corn for pigs.