Influence of Growth
Conditions on Alfalfa Protein Degradability
D. Z. Skinner1,
I. E. O. Abdelgadir2, T. K.
Fish3, and R. C. Cochran2
USDA-ARS and Agronomy Dept.1,
Animal Sciences Dept.2, and
Plant Pathology
Dept3.
Kansas State Univ.
Manhattan, KS 66506
The shortcomings of alfalfa
(Medicago sativa L.) as a high quality
forage include extensive ruminal degradation
of the forage protein, sometimes with
concomitant loss through ammonia formation.
Previous research has shown that the
degradability of total alfalfa protein varies
among individual plants, and among harvests
of the same plants (Skinner et al., 1994).
In this report, the effect of environmental
conditions during the growth of alfalfa plants
was investigated as a source of significant
variation in protein degradability. Ten plants
of diverse origins were vegetatively propagated
and genetically identical ramets were
grown in rigidly-maintained environments
differing in temperature and humidity
[25C and 32% average relative humidity
(rh) vs. 15C and 61% rh] . Some hay quality
characteristics related to protein differed
among plants grown under the same conditions
(example in Table 1). Total protein from
plants grown at 25C was consistently more
resistant to degradation than the protein
from the same plants grown at 15C (Fig. 1).
Differences among degradable fractions between
the environments were not consistent across
genotypes (Fig. 1). These results suggest
that genotypic effects for quality characteristics
expressed under rigidly-maintained environments
exist, and that environmentally stable
genotypes may exist. Selection for reduced
degradability among environmentally stable
genotypes likely will result in populations
with reduced degradability expressed over
a broad range of growth conditions.
Table 1. Genotypic Effects on Quality Characteristics
of Alfalfa Hay Grown at 15C and 61 % rh.
|
| Plant
| |
| Item
| Varia-34
| Ladak-86
| σm |
| N, % of DM
| 2.09
| 2.39
| 0.12 |
| ADF, % of DM
| 26.70
| 26.90
| 0.23 |
| NDF, % of DM
| 34.50
| 35.90
| 1.43 |
| Ash, % of DM
| 8.75
| 8.80
| 0.33 |
| ADIN, % of total N
| 5.05
| 5.10
| 0.74 |
| NDIN, % of total N
| 10.25
| 7.45
| 0.46 |
| Pool A1, % of total N
| 32.67
| 38.20
| 4.32 |
| Pool B, % of total N
| 56.23
| 47.95
| 3.91 |
| Pool C, % of total N
| 11.10
| 13.85
| 0.44 |
| UIP2
| 23.30
| 21.34
| 0.96 |
1 Pool A=nonprotein nitrogen; pool c=48h
residual nitrogen from Streptomyces griseus
protease in vitro method; pool B=potentially
availabie nitrogen.
2 UIP= Undegradable intake protein.
germplasm sources.
Fig. 1. Degradation of protein from 10 plants
grown under different conditions. 
Reference:
- Skinner, D. Z., J. O. Fritz,
and L. L. Klocke. 1994. Protein degradability
in a diverse array of alfalfa Crop Sci. 34:1396- 1399.
1995 Central Alfalfa Improvement Conference Proceedings
Send a question or comment directly to the corresponding author:
Dr. D.Z. Skinner
|