Lance R. Gibson

Effects of triticale-based diets on finishing pig performance and pork quality in deep-bedded hoop barns

Effects of triticale diets on pig performance and pork quality were evaluated in summer and winter. Diets were: corn-soy, 40% triticale, or 80% triticale. Pigs (72kg) were fed 49d. Loins were evaluated for meat and fat quality and sensory evaluation. Average daily gain decreased as triticale inclusion increased (P<0.01). Feed intake was similar. Pigs fed corn-soy had the greatest and those fed 80% triticale had least gain:feed ratio (P<0.05). In summer, pigs fed corn-soy had largest and those fed 80% triticale diet had smallest loin muscle area (P<0.05) based on ultrasound scan. During summer, ultimate pH was higher (P⩽0.001) and, loin purge and shear force were lower (P<0.05). Diet did not affect sensory evaluation or fatty acid profile of loins. During summer, total MUFA were more and total PUFA were less (P⩽0.01). Triticale fed to pigs in hoop barns slightly decreased growth without compromising pork quality.

A Laboratory Exercise for Teaching Plant Interference and Relative Growth Rate Concepts

Interference between weeds and crops is a key topic in undergraduate weed science courses. A laboratory exercise was developed at Iowa State University to actively demonstrate how small-seeded weeds can compete with large-seeded crops despite the initial seedling size disadvantage. Spring wheat and wild mustard were grown in pots in monoculture and in competition with each other. One set of plants was harvested at 1 wk after planting and another at 6 wk after planting. Relative growth rates (RGR) were calculated for the 5-wk period using the classical approach of plant growth analysis. The results from four semesters were analyzed to determine whether the experiment was meeting its intended outcomes. It was successful in this regard. In each of the four semesters, wild mustard had a lower initial dry weight and a greater RGR than did wheat. Students were required to write a scientific paper using the experimental results after completing a series of active-learning exercises. Assessment by students suggested that the experiment, active-learning exercises, and writing assignment were valuable activities. Nomenclature: Spring wheat, Triticum aestivum L. ‘Sharp’; wild mustard, Brassica kaber (DC.) L. C. Wheeler #3 SINAR. Additional index words: Education, weed biology, weed ecology. Abbreviations: RGR, relative growth rate.

A laboratory exercise for teaching critical period for weed control concepts

Crop–weed interactions is an important topic for introductory weed science courses. The effect of the timing of weed emergence and the duration of weed competition on crop yield are two topics usually covered when discussing competition. Students generally gain a better knowledge of these concepts through observation in addition to discussion of the underlying concepts. An additive removal and plant-back experiment was used, in the undergraduate weed science laboratory at Iowa State University, to demonstrate critical period for weed control concepts for cultivated radish. In one series of treatments, weeds were sown at the time of radish planting and removed at 2, 3, and 4 wk after planting. In another series, weeds were sown at 1, 2, and 4 wk after radish planting and allowed to grow in the flats until completion of the experiment. Two controls, one weed free and one unweeded, were also included. The results from four semesters suggested that the critical period for weed control began immediately after planting and lasted 3 wk. The timing and duration of the critical period was consistent across the four semesters evaluated. This activity was successful in demonstrating the critical period for weed control in radish. Nomenclature: Radish, Raphanus sativus L. Additional index words: Competition, education, weed ecology, weed-free period.