Effects of placing cattle on feed at two-month intervals and housing on feedlot performance and carcass grades.

A 5-yr study was conducted involving the placement of yearling steers on feed at 2-mo intervals under three different housing systems. A total of 3,571 steers (180 pens) initially averaging 318 kg was used. Evaluations were made for DM intake, ADG, feed efficiency (FE), carcass quality (QG), and yield grades (YG). Cattle were assigned to either an open lot with overhead shelter (S), 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. Corn grain provided 85% of the energy; the remainder was supplied by corn silage and protein supplement. Cattle were fed 140 to 180 d to achieve an average slaughter weight of 500 kg. The main effects of year (Y), month (M), and housing (H) affected DM intake, ADG, FE, and final live weight (P less than .01). The interactions for Y x M, M x H and Y x M x H affected ADG (P less than .05). Month and H affected hot carcass weight (P less than .01). Year affected YG, and year and month affected QG (P less than .01). Month effects on DM intake and ADG indicated that cattle started in May had the highest intake and ADG (P less than .05) and that cattle started in November had the lowest (P less than .05) DMI and ADG. Month effects on FE indicated that cattle were most efficient when placed on feed during March, May, and July (5.82, 5.72, and 5.66 kg DM/kg gain; P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Factors affecting in-transit shrink and liver abscesses in fed steers.

Live weight loss (shrink) and liver conditions (abscesses) were determined on 3,570 crossbred steers of predominantly British breeding over a 5-yr period. Starting in November 1979, steers were placed on feed at bimonthly intervals and provided one of three housing treatments: no shelter, access to overhead shelter or confinement. All steers were implanted with Synovex during the first 3 yr and Compudose the last 2 yr and fed a diet consisting of high-moisture corn grain, which provided 85% of the energy, and corn silage, along with a protein, vitamin and mineral supplement. Cattle were processed into beef after a feeding period of approximately 160 d. Year affected shrink (P less than .001), and month on feed and housing type tended to alter shrink. Cattle marketed during summer and fall and those outside without overhead shelter tended to shrink more. Year, month on feed and housing type affected liver condition (P less than .01). Cattle started on feed in November and January and cattle housed in confinement or outside without overhead shelter had higher incidences of liver abscesses and slower average daily gains (P less than .01). Daily gains for steers with normal and abnormal livers were not different (P greater than .19) for any month started on feed or housing treatment. These results indicate that under the conditions of this study a 2 or 3% weight loss should be expected during the marketing of finished steers and a 16% incidence of liver abscesses should be anticipated, with some modification of the latter due to time of year and housing. The presence of liver abscesses at the time of processing steers into beef did not reduce feedlot performance.

Adipose tissue growth and cellularity: changes in bovine adipocyte size and number.

Forty crossbred steers of similar birth date and fed the same growing-finishing diet were used to study adipocyte changes in six fat depots during growth from 11 to 19 mo of age. Steers were slaughtered at 2-mo intervals. Adipose tissue samples were obtained from kidney, mesenteric and brisket fat and subcutaneous, intermuscular and intramuscular fat from the 10th to 12th rib section. The osmium tetroxide fixation technique was used for determination of cell size and number. Except for three brisket fat samples, distributions of adipocyte diameters from six different fat depots were monophasic during the age range considered in this study. At 17 mo of age, the mean adipocyte diameter, in decreasing order, was: kidney fat greater than mesenteric greater than subcutaneous greater than intermuscular greater than intramuscular greater than brisket fat. Fat deposition during growth to 19 mo of age occurred mainly by hypertrophy of adipocytes. An apparent cell hyperplasia occurred in the intramuscular fat depot from 11 to 15 mo and in the brisket fat depot after 15 mo of age. Based on cellularity characteristics, evidence exists to classify intramuscular and brisket fat depots as late-developing ones. Cell number/gram of intramuscular adipose tissue was a better predictor of marbling score than was fat cell diameter.

Injection of iron in newborn beef calves: erythrocyte variables and weight gains with newborn-dam correlations.

Iron injection in beef calves during the 1st week after birth increased their PCV, hemoglobin (Hb) concentrations, mean corpuscular volumes (MCV), and mean corpuscular Hb (MCH). These increases persisted between weeks 2 and 12. The RBC count during the 1st week after birth had a positive correlation with the PCV and Hb concentrations and a negative correlation with the MCV and MCH. There was a positive correlation between the serum iron concentration of the dams and their MCV and mean corpuscular Hb concentration. There was also a positive correlation between the MCV and MCH of the dam and their calf's MCH. Seemingly, iron injection did not affect weight gain during the first 18 weeks of life.

Influence of different ratios of corn and corn silage, housing systems and seasons on the performance of feedlot steers.

Observations on the effects of season, housing and diet were made on 916 steers in three winter and two summer trials. Diets consisted of corn grain and corn silage, in balanced rations, fed ad libitum with energy ratios of 25:75 (Diet 1), 55:45 (Diet 2) and 85:15 (Diet 3). There were three types of housing systems: outside lots without access to overhead shelter (NS), outside lots with access to overhead shelter (OS) and an open-front confinement building (C). Average ambient temperatures and precipitation for winter and summer trials were -1.0 and 15.3 C and 4.67 and 10.81 cm/mo, respectively. Steers gained more (P less than .05) in summer than in winter. Within housing system, OS and NS steers gained faster and consumed more dry matter (DM) and energy (P less than .05) than C steers; C-fed steers were less (P less than .05) efficient (kg feed DM/kg gain) than OS steers. Steers fed Diet 1 had lower (P less than .05) average daily gain (ADG) than those fed Diets 2 and 3. Steers on Diet 3 consumed less DM (P less than .05) than those on Diets 1 and 2. Estimated metabolizable energy intake (MEI) was significantly less for cattle fed Diet 1 than those fed Diets 2 or 3. Diet 3 was more (P less than .05) efficient than Diet 1. Season x diet (P less than .10) and season x housing (P less than .10) interactions were found for daily DM intake and MEI. This resulted in greater cattle growth rate responses to higher grain diets in summer than in winter and more pronounced adverse effects of confinement rearing in summer than in winter. No evidence was found of other two-way or three-way interactions for any of the performance characteristics studied. These results indicate that in addition to important singular effects of season, housing and diet, important interactions of these factors also exist.

Experimentally induced foot rot in feedlot cattle fed rations containing organic iodine (ethylenediamine dihydriodide) and urea.

Foot rot was experimentally induced in feedlot cattle with a mixed inoculum of Fusobacterium necrophorum (Sphaerophorus necrophus) and Bacteroides melaninogenicus. Both bacteria were isolated from the lesions. Isolates of F necrophorum from 2 of the lesions were serologically compared, using a passive hemagglutination test with the strain used to induce the lesions. These isolates were serologically similar but not identical, indicating antigenic change had occurred during animal passage. The addition of ethylenediamine dihydriodide or urea to the rations did not affect the frequency of experimentally induced foot rot.