Date of Award
Doctor of Philosophy
A five-year study, involving the placement of yearling steers on feed at bimonthly intervals under three different housing systems, was initiated in November of 1979. A total of 3,571 yearling steers initially weighing 700 lb. was used in the study. Parameters evaluated were feed consumption (I), average daily gain (ADG), feed efficiency (FE), and quality (QG) and yield (YG) grades. Cattle were assigned to either (1) an open lot with overhead shelter (S); (2) an open lot without overhead shelter (NS), or an open-front confinement building (C). Each treatment consisted of two lots of 20 steers each per interval per trial. All steers were implanted with a growth stimulant at the start of each trial. The ration provided 85% of the energy from corn grain and the remainder from corn silage and protein supplement. Steers were individually weighed at approximately 28-day intervals until removed from test for processing into beef. Each weigh period was considered to represent a different stage of feeding. Average lot final weight was approximately 1,100 lb. following a 140 to 180 day feeding period. The main effects of month and housing each had an effect on I, ADG, and FE (P < .0001). Month affected QG (P < .0035) but not YG. Housing did not affect YG or QG. The month x housing interaction had an affect on I (P < .0002), ADG (P < .0338), and FE (P < .0045) but did not affect YG and QG. The month effects on I and ADG indicated that cattle started on feed in May had the highest I (17.21 lb; P < .05) and ADG (3.02 lb; P < .05). The month effects on FE indicated that cattle were most efficient when placed on feed during the months of March, May, and July (5.82, 5.72, 5.66 lb; P < .05). The housing affects on I, ADG, and FE showed the S cattle had the highest I, ADG, and FE (17.18, 2.84, 6.15 lb; P < .05). The C group had the lowest I and ADG (15.37, 2.41 lb; P < .05), but their FE (6.49 lb.) did not significantly differ from that of NS cattle (6.42 lb.). Cattle in their beginning stage of feeding (periods 1 and 2) consumed the least amount of feed and had the overall highest ADG. Feed conversions between each stage of feeding did not differ significantly. Within all periods, cattle are more adversely affected by winter months than by months associated with higher temperatures.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Gary Michael Pusillo
Pusillo, Gary Michael, "The effects of placing cattle on feed at bimonthly intervals, housing, and stage of feeding upon feedlot performance and carcass grades " (1986). Retrospective Theses and Dissertations. 8029.