1. GEM and the UW Silage Breeding Project
J.G. Coors
D. Majee
D.T. Eilert
P.J. Flannery
Department of Agronomy
University of Wisconsin
with acknowledgements to:
J.G. Lauer
UW Department of Agronomy
R.D. Shaver
UW Department of Dairy Science

2. Outline Silage quality – what is it? UW silage breeding system
GEM contributions – silage germplasm
GEM contributions – starch degradability
Summary

3. Dry Matter Protein Carbohydrate Sugar and Starch Bugs Fiber Bugs
Degradable
protein
Sugars &
starch
Cell wall
Bound
Unavailable
starch
Sugar and Starch
Bugs
Bound
with Lignin
Undegradable
protein
Fiber Bugs
Digestible
energy & protein
Absorbed
Metabolizable
energy & protein
Maintenance
Growth
Pregnancy
Lactation

5. Milk2000

6. Processed Unprocessed
Adapted from Schwab and Shaver, unpublished. Based on data of Bal et al., 2000;
Dhiman et al., 2000; Rojas-Bourrillon et al., 1987

7. GEM Contributions – Silage Germplasm
Phase I
Silage evaluation of elite GEM topcrosses (~15-25) that were identified in prior years by other GEM cooperators as having high grain yield and suitable maturity for Wisconsin (<120RM).
Phase 2
For those topcrosses with high forage yield and good nutritional quality in Phase 1 trials, the respective GEM breeding population is included in the UW inbred development nursery for further inbreeding and selection
Phase 3
Inbred development – testcrosses at S2 to S6 generations using two to four inbred testers

8. 2004 UW GEM Program Phase I Phase 2 Phase 3
17 breeding populations or early generation GEM inbred families crossed to LH185, LH198, LH200, LH244, or LH287 were evaluated for silage potential (GEMNEW).
Phase 2
Gem inbreeding nursery included ~400 inbred families from 10 breeding populations. Most inbred families (~170) were derived from CUBA164 background.
Phase 3
160 advanced generation inbreds from six populations were crossed to two testers each for evaluation in 2005.
Evaluated ~50 S3+ families topcrosses to two testers (GEM198, GEM244).
27 promising S4+ families evaluated in topcrossed to two to four testers each (GEMADV).

9. Forage yield for GEMNEW trial in 2004
Entries marked with “*” will be analyzed for nutritional quality

10. 2004 UW GEM Program Phase I Phase 2 Phase 3
17 breeding populations or early generation GEM inbred families crossed to LH185, LH198, LH200, LH244, or LH287 were evaluated for silage potential (GEMNEW).
Phase 2
Gem inbreeding nursery included ~400 inbred families from 10 breeding populations. Most inbred families (~170) were derived from CUBA164 background.
Phase 3
160 advanced generation inbreds from six populations were crossed to two testers each for evaluation in 2005.
Evaluated ~50 S3+ families topcrosses to two testers (GEM198, GEM244).
27 promising S4+ families evaluated in topcrossed to two to four testers each (GEMADV).

11. 2004 UW GEM Program Phase I Phase 2 Phase 3
17 breeding populations or early generation GEM inbred families crossed to LH185, LH198, LH200, LH244, or LH287 were evaluated for silage potential (GEMNEW).
Phase 2
Gem inbreeding nursery included ~400 inbred families from 10 breeding populations. Most inbred families (~170) were derived from CUBA164 background.
Phase 3
160 advanced generation inbreds from six populations were crossed to two testers each for evaluation in 2005.
Evaluated ~50 S3+ families topcrosses to two testers (GEM198, GEM244).
27 promising S4+ families evaluated in topcrosses to two or four testers each (GEMADV).

12. Forage yield for GEM198 and GEM244 trials in 2004

13. Forage yield for GEMADV trial in 2004

15. WQS/GQS S5 families S6 lines S1 families (~500) Season 1 (winter)
Season 2 (summer)
Evaluate & 
Recombine
S3 families (~150)
Testcross
(1 tester)
S2 testcrosses (~150)
Season 3 (winter)
Evaluate & select
S2 families (20 selects)
Season 4 (summer)
Season 5 (winter)
S4 families
(~20-40 selects)
S4 testcrosses (~75-100)
Season 6 (summer)
Season 7 (winter)
Increase
S4 selected families
(2-3 testers)
Inbred release
Sample hybrids for distribution
WQS/GQS 

16. Components of GEM Quality Synthetic (GQS)
2003 trial, LH279 topcrosses

17. GEM Contributions – Starch Degradability
Starch and the kernel contribute about 55% and 75% of the energy value of corn silage, respectively (Shaver and Schwab, 2001). Corn grain vitreousness was found to increase with advancing maturity and ruminal starch degradation decreases linearly as vitreousness increase (Correa et al., 2001). The proportion of vitreous and floury endosperm that surrounds starch granules was found to determine endosperm texture (Michalet-Doreau and Doreau, 1999). Kernel composition, structure and density is known to affect hardness characteristics (Martin et al, 1987). Whilst kernel density is in turn affected by the relative amounts of the major nutrient components (e.g. starch and its proportion of amylose to amylopectin; and protein) and their packing. Hence, there is need to evaluate kernel endosperm characteristics that can be easily used to screen corn germplasm in large breeding programs for livestock feeding.

18. Rumen Degradability of Starch

19. Starch Degradability Oh43 o2 CHO5015:N12-387-1-B
Starch and the kernel contribute about 55% and 75% of the energy value of corn silage, respectively (Shaver and Schwab, 2001). Corn grain vitreousness was found to increase with advancing maturity and ruminal starch degradation decreases linearly as vitreousness increase (Correa et al., 2001). The proportion of vitreous and floury endosperm that surrounds starch granules was found to determine endosperm texture (Michalet-Doreau and Doreau, 1999). Kernel composition, structure and density is known to affect hardness characteristics (Martin et al, 1987). Whilst kernel density is in turn affected by the relative amounts of the major nutrient components (e.g. starch and its proportion of amylose to amylopectin; and protein) and their packing. Hence, there is need to evaluate kernel endosperm characteristics that can be easily used to screen corn germplasm in large breeding programs for livestock feeding.
CHO5015:N B
Oh43 o2

20. [Correa et al., 2002]

21. Starch Degradability Studies
Objectives
Determine whether there is genetic variation for starch
degradability
Determine the extent to which kernel vitreousness is related
to starch degradability

22. Starch Study Entries: 32 inbred lines and 1 population (2002)
19 hybrids (2003)
Harvest dates:
½ milkline (ML, ~35% DM)
Black layer (~15 d post ½ ML)
Experiment design (field):
RCB with 3 replicates
Madison , 2003
1 self-pollinated row – 3.04 x 0.76 m
10 plants per row

23. Procedure – Two-Stage Starch Digestion
(Pioneer Hi-Bred International, Inc.)
STAGE in-situ ruminal incubation
Two steers with ruminal cannula – 2 wk adaptation to 70% (DMB) corn silage diet
In-situ procedure:
Corn kernels ground with Wiley Mill (6mm screen)
1.5g ground material placed in 5 x 5 cm dacron bag
Eight replicate bags incubated for each sample
Placed in rumen for 0 and 14 h,
Removed, rinsed and dried at 62oC for 24 h
STAGE post-ruminal in-vitro incubation
14-h ruminal residue subjected to 8 h incubation
intestinal enzymatic cocktail (pepsin + pancreatic enzymes)
Final Action
Eight replicates for DM disappearance
Eight replicated bags composited for a single starch analysis

24. ½ milk-line stage

25. Black layer stage

26. Black layer stage
W64A X Oh43 o2
W64A X Oh43 fl2
W64A X Oh43 su2

27. Black layer stage – hybrids

29. Summary
GEM has contributed greatly to the UW silage breeding program by
providing:
1) Superior and unique germplasm
2) Better understanding of nutritional properties of silage