Masters Theses
Date of Award
8-1981
Degree Type
Thesis
Degree Name
Master of Science
Major
Animal Science
Major Professor
Will T. Butts
Committee Members
J.W. Holloway, E.R. Lidvall
Abstract
Data from 630 Angus, Hereford and Charolais-cross feeder calves were utilized to study the relationship between initial calf measurements, selected performance variables and feedlot performance.
Calves were fed either a silage plus limited concentrate diet (medium-energy) or a growing-finishing grain diet (high-energy) and were serially slaughtered at a predetermined date to give a range in carcass quality from standard to high choice.
The steers were photographed, weighed and sonorayed for subcutaneous fat thickness upon arrival at the farm. This, along with weight of the calves at time of purchase, made up the objective initial measurements. Initial subjective scores were obtained from the evaluation of the animals by a single grader before the initiation of the trial. During the trial, animals were weighed and sonorayed for subcutaneous fat at biweekly intervals. These measurements and variables calculated from them along with average daily feed consumption records were used for performance variables in the analyses.
Means for each diet indicated that cattle on the grain diet were heavier, fatter cattle that gained weight more rapidly and consumed more feed.
Residual correlation within year and within year-breed groups were used to determine simple relationships that existed among the variables used in this study. Initial weight was related to initial depth, weight, weight.75 (PFactor analyses were conducted within year-breed groups for both diets to test for redundancies among variables and to describe the sample of calves. Five factors were used to explain variation among calves with factor 1 being a shape or rate of maturing factor and explaining 49 and 43% of the correlation structure for the grain and silage diets, respectively. Factor 2 explained an additional 17 and 22% of the variation for cattle on the grain or silage diet, respectively and was considered a factor that explained differences in feed efficiency. Factors 3, 4 and 5, for cattle on the grain diet, explained an additional 25% of the correlation structure with factor 3 explaining fat and fat change variation, factor 4 explaining differences in consumption and factor 5 explaining variation caused by size differences. Factors 3, 4 and 5, for cattle on the silage diet, explained an additional 22% of the variance with factor 3 being a consumption factor, factor 4 explaining shape variation and factor 5 explaining variation in weight.
Canonical correlation analyses, for cattle on each diet, were calculated correlating objective and subjective initial measurements with selected performance variables. Two major relationships were described using canonical correlations. First, initially taller, thinner or initially larger framed, thinner cattle were related to heavier, thinner cattle that consumed more feed, gained more weight and converted feed to gain slightly more efficiently than the average. Secondly, initially heavier, deeper bodied feeder calves were heavier, fatter cattle that gained relatively little weight and converted feed to gain less efficiently than other types of cattle described.
Multiple regression analyses were utilized to develop prediction equations for selected performance variables for cattle on both diets. Prediction equations regressing initial measurements on performance traits were found to be an accurate method in predicting performance with R2 values ranging from .43 for consumption on the grain diet to .73 for relative gain on the silage diet. Regressing selected performance variables on other variables of feedlot performance calculated R2values ranging from .47 for consumption of feed on the grain diet to .93 for feed efficiency on the grain diet. Initial height and initial fat were found to be initial measurements of mature size and rates of maturing with each being significant in most of the models used in predicting performance of cattle on the grain and silage diets, respectively. Fat measured at biweekly intervals was also significant in every model used in the analyses. Fatter cattle deposited fat more rapidly, gained less weight, consumed less feed and were less efficient on the silage diet while being more efficient on the grain diet. Average daily gain and relative average daily gain were found to be highly related to feed efficiency (P< .001) with faster gaining cattle being more efficient. It was also concluded that later maturing, growthier cattle were more efficient in producing edible protein than were earlier maturing cattle when fed a high-energy diet.
Questions were also raised concerning the broad generalizations that the California Net Energy System (ONES) makes concerning energy requirements for feedlot cattle. Charolais-cross steers, which were considered the late-maturing group of steers gained more weight and consumed less feed being more efficient than earlier maturing Angus steers on the grain diet. These results indicate that protein deposition is more efficient than fat deposition and adjustments in the CNES should be made for the differences in rate of maturing and mature size.
Recommended Citation
Young, Joe, "The relationship among initial linear body measurements, characteristics of feedlot cattle and subsequent performance. " Master's Thesis, University of Tennessee, 1981.
https://trace.tennessee.edu/utk_gradthes/7654