Masters Theses

Date of Award

12-1972

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

D.O. Richardson

Committee Members

J.T. Miles, M.J. Montgomery

Abstract

Feed intake and production data on 226 first lactation Jerseys fed either an all forage or a forage plus grain ration were analyzed to determine the variation in gross efficiency during portions of the lactation, and to evaluate the association among several measures of economic efficiency.

Gross feed efficiency (FCM/TENE) was highest for cows on the all forage ration, but showed a steady decline throughout the lactation for cows on both rations. Maximum gross efficiency was attained during the first lactation period (1-70 days), and the most rapid decline in gross efficiency occurred from the first to the second period (71-140 days) of the lactation. The all forage group maintained the highest gross efficiency throughout the lactation, which was apparently due to the catabolism of body fat. The all forage group lost twice as much weight during the first lactation period and were consistently below the forage plus grain group throughout the lactation.

Multiple regression analyses were performed to determine the influence of various factors on gross efficiency. Year-seasons had a significant influence throughout the lactation on the all forage group. However, weight change exerted the most single influence on gross efficiency and showed linear effects in the all forage group during the first and total lactation periods. The effects of weight change were less pronounced on the forage plus grain group and were curvilinear in some instances. Days open had little effect on gross efficiency and varied from one lactation period to another. R2 values indicated that much of the variation in efficiency occurred in the first and second lactation periods for the forage plus grain group and the all forage group, respectively.

The measures of economic efficiency studied were income over feed cost, feed cost per cow, and feed cost per 100 lbs. of 4% fat-corrected milk. Mean income over feed cost was $113 per cow greater for high milk price than for low milk price in the forage plus grain group and $95 per cow greater in the all forage group. High grain price was less disadvantageous to income over feed cost than high forage price in the forage plus grain group.

Within price group correlations among the different measures of efficiency were similar indicating that the different methods of utilizing feed intake data give about the same results in comparing different cows.

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