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Luis Felipe P' Silva

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Elucidate physiological pathways hindering cattle productivity in Brazil ... Sexual maturation of Zebu heifers. Role of leptin on attainment of puberty ... – PowerPoint PPT presentation

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Title: Luis Felipe P' Silva


1
Prospection of Genes of Interest in Agriculture
  • Luis Felipe P. Silva

Laboratory of Functional Genomics College of
Veterinary Medicine and Animal Science Universidad
e de São Paulo Pirassununga
2
Mission
  • Elucidate physiological pathways hindering cattle
    productivity in Brazil
  • Areas of current research
  • Sexual maturation of Zebu heifers
  • Role of leptin on attainment of puberty
  • Nutritional quality of tropical forages
  • Maize silage
  • Guineagrass

3
Understanding nutritional quality of forages
  • Forages form the basis for cattle production in
    Brazil
  • 170 mi ha (76 of agricultural land)
  • 95 of beef are raised exclusively on pasture
  • Guineagrass and Brachiaria respond for more than
    85 of forage area

4
Understanding nutritional quality of forages
  • Digestibility of tropical forages is low and
    decreases rapidly with advanced maturity

Source Muir Jank (2004)
5
Understanding nutritional quality of forages
  • On average, tropical forages are 15 less
    digestible than temperate forages
  • C4 plants (Kranz anatomy - lignification)
  • Protective structures (lignification)
  • Long warm nights (lignification)
  • An increase in 10 of NDF digestibility would
    results in additional 1.6 million tons of carcass
    in Brazil (US 3.5 billions/year)

6
Forage breeding
  • Cattle production depends heavily on
    forage production
  • Forage quality is low and declines rapidly with
    maturity
  • 90 mi ha of cultivated forages (ABRASEM)
  • 100,000 t of seeds per year
  • US 100 mi per year

7
Forage breeding
  • How many cultivars were released in Brazil as a
    results of a forage breeding program?
  • None
  • Two from Colombia (CIAT)
  • Tropical forages are apomitic
  • Release of cultivars by
    selection of accessions
    rather than breeding

8
Metabolic engineering
9
Characterization of genes related to
lignification in guineagrass
  • Objectives
  • To sequence mRNA coding for the main enzymes in
    the lignin synthesis pathway
  • Study the effect of maturity on expression of
    these genes
  • Identify genes strongly correlated with the
    digestibility decline with advanced maturity

10
Material and Methods
  • Field study of 12 P. maximum accessions in Campo
    Grande, MS (20.25S, 54.40W).
  • Plots of 4 x 2.5 m with 6 lines.
  • After leveling cut on December 29th of 2005,
    plots were fertilized and harvested with 30, 60
    or 90 days of regrowth.

11
Material and Methods
  • At each date two lines were harvested
  • Total mass was weighted and sub-sampled for
    determining leafstem ratio and senescent
    material
  • Stem stalk leaf sheath
  • Leaf leaf blade
  • Dried at 55oC for 72h and grinded to pass a 1 mm
    screen

12
Material and Methods
  • FDN content and FDN digestibility as in Goering
    VanSoest (1970).
  • Only fermentative phase for 30 h of incubation

13
Material and Methods
  • Statistical Analysis
  • Randomized block design.
  • Model
  • Y ? ?i ?j ?k ?i?j ?k?j ?i?k
    eijk
  • Where ?icultivar ?jblock ?kage
  • ?j, ?i?j and ?k?j were random
  • MIXED procedure of SAS

14
Results
15
NDF digestibility of leaf- and stem-fractions
16
Effect of cultivar on NDF digestibility of the
leaf-fraction
There was no genetic difference in leaf-NDFD
17
Effect of cultivar on NDF digestibility of the
leaf-fraction
There was no genetic difference in the slope of
the decline of leaf-NDFD with age
18
Effect of cultivar on NDF digestibility of the
stem-fraction
There was large genetic difference in stem-NDFD
19
Effect of cultivar on NDF digestibility of the
stem-fraction
There was large genetic difference in the slope
of the decline of stem-NDFD with age
20
Effect of cultivar on the slope of NDFD decline
with maturity
21
Effect of cultivar on the slope of NDFD decline
with maturity
22
Identification of genes
23
PCR amplification was successful for all 7 genes
Lane 3 PAL, Lane 4 CAD, Lane 5 COMT, Lane 6
CCR, Lane 7 C4H, Lane 8 4CL.
24
Similarity was high among grasses
25
Conclusions
  • There was significant genetic diversity for
    stem-NDFD, and no variation for leaf-NDFD.
  • There was significant genetic diversity for the
    decline in NDFD with advancing maturity only for
    the stem fraction.

26
Implications
  • The slope of stem-NDFD or stem-NDFD with 90 days
    of regrowth could be used as a quality parameter
    for P. maximum selection or breeding programs, or
    for genetic manipulation programs.
  • The continuing of this project will try to
    identify the genes controlling the decline of
    NDFD with advanced maturity

27
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