Prediction of body weight gain of beef cattle from volatile fatty acids, visual pasture score, and chemical analyses of forage and the relationship of body weight gain to forage intake

Author

Delmer Irvin Davis

Date of Award

12-1969

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

C.S. Hobbs

Committee Members

K.M. Barth, L.H. Keller, J.K. Bletner

Abstract

The objectives of this study were: (a) to investigate several methods of pasture evaluation useful for prediction of the daily gain of beef calves, (b) to study plant factors which are related to body weight gain of grazing heifers, (c) to investigate the reasons for increased daily gain in pastures containing clover, and (d) to test the hypothesis that decreased forage dry matter intake is related to decreased animal performance.

Two grazing trials were conducted with the following four pasture species: (1) Tall fescue (Festuca arundacea). (2) Orchardgrass (Dactylis glomerata), (3) Ladino clover (Trifolium repens), and (4) Kobe lespedeza (Lespedeza striata). Experiment 1 was conducted with heifers grazed on tall fescue (FES), orchardgrass-Ladino clover (OC), and fescue-orchardgrass-clover (FOG) pastures. Changes in body weight and subcutaneous fat thickness were determined. Experiment 2 was conducted with steers grazed on fescue-lespedeza (FL) and orchardgrass-clover (OC) pastures. Changes in body weight were determined and forage dry matter intake was estimated. Forage intake was calculated from a total faces collection and in vitro dry matter digestibility.

Forage quality measures (visual and laboratory) which were related to body weight gain of cattle were used to develop regression equations for predicting daily gain. The results of this study were as follows:

1. The daily gain and change in fat thickness of heifers grazing OC or FOC pastures was higher than that of heifers grazing FES pastures.

2. Estimates of forage utilization by grazing heifers indicated that the order of preference was clover, orchardgrass, and tall fescue.

3. This study indicated that samples representative of the pasture clipped according to the method used by High were of little value when only chemical or VFA analysis were to be used as evaluation criteria. The same variables obtained from pure samples of the major species were highly associated with ADG.

4. Organic matter digestibility, soluble carbohydrates, and total VFA analysis of clover were the most useful single variables for prediction of ADG from analyses of forage samples.

5. Propionic acid (in vivo) and total VFA (in vivo) were highly correlated with ADG when rumen-liquor samples collected through the rumen fistula were analyzed, but the magnitude of coefficients of correlation was decreased when oral samples were taken from the same animals, possibly because of saliva contamination.

6. in vitro VFA analysis indicated that clover is of higher nutritive value than orchardgrass or tall fescue. It had a greater potential to form the energy-rich VFA's.

7. Clover or legume percentage was consistently indicated as an important factor for desirable gain for beef heifers on pasture. These data indicated that the reason for the advantage in gain due to clover is the higher content of digestible nutrients as indicated by its higher digestible organic matter content, soluble carbohydrates content, and its ability to form volatile fatty acids. These characteristics were consistently high in clover over the growing season, whereas grasses did not maintain these factors at an adequate level after the point of maturity. These factors alone were ample reasons to expect superior gain on clover-containing pastures under practical management regimes.

8. If intake is to be related to body weight gain, these data indicated that some adjustment in intake estimates must be made for body maintenance.

9. Total digestible nutrient (TDN) intake was greater for cattle grazing forage from OC pastures when equal amounts of dry matter from OC and FL pastures were ingested. Percentage TDN and intake of the forages were closely associated, indicating that intake is associated with quality of forage.

Recommended Citation

Davis, Delmer Irvin, "Prediction of body weight gain of beef cattle from volatile fatty acids, visual pasture score, and chemical analyses of forage and the relationship of body weight gain to forage intake. " PhD diss., University of Tennessee, 1969.
https://trace.tennessee.edu/utk_graddiss/8031