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Transgenic Animals and Lactation
Application of transgenic technology to lactation
Introduce new proteins to give specific changes– Animal growth & health– Bacteria levels– Processing properties– Fat content/type– Amount of protein
UCD first to demonstrate the functional and physical properties of milk can be altered by
the transgenic approach
Expressed human lysozyme in mouse milk
– Made lysozyme at 0.4 mg/ml under the control of the bovine αs1-casein gene
Followed lactation curve
– Faster rennet clotting time and stronger curd
– Slowed growth of mastitis-causing and cold spoilage bacteria Maga et al. 1994 Transgenic Res 3:36-42
Maga et al. 1995 J Dairy Sci 78:2645-2652Maga et al. 1998 J Food Prot 61:52-56
What about a real animal?Non-bioreactor transgenic animals for lactation
Source Promoter Gene SpeciesU. Illinois
M. Wheeler 2002 bα-lac bα-lac Pig2005 bα-lac hIGF-I Pig
UC DavisE. Maga 2004 gβ-lg rSCD Goat
2006 bαs1 hLysozyme GoatUSDA
B. Wall 2005 oβ-lg Lysostaphin Cattle
New ZealandG. Laible 2003 bβ-CN bβ/κ-Casein Cattle
Hypothesis:Animal Growth & Health
Faster growth– Greater pre-weaning gain
Maintenance of growth during illness– Improved disease resistance, immune
factors
Transgenic pigs and lactation
More α-lactalbumin– To increase milk production
Transgenics make more lactose (and milk) and pigs grow faster
IGF-1– Intestinal development
Increased musocal weight and enzyme activity
Noble et al. 2002 J Anim Sci 80:1090-1096Monaco et al. 2005 Transgenic Res 14:761-773
Hypothesis:Fat Content/Type
Short chain, saturated fatty acidsIf enzyme added to modify existing fat:– Change ratio of “bad” fat to “good”
Milk more healthy for human consumptionNovel flavorsNovel products
Stearoyl-CoA desaturase in the mammary gland
The type of fat in milk is modified
– Transgenic goats make less SFA and more MUFA and PUFA
Total amount of fat remains the same
– Transgenic goats make more CLA
Disease resistance implications
Reh et al. 2004 J Dairy Sci 87:3510-3514
-10
-5
0
5
10
15
20
25
30
#34 #37 #53
SFA
MFAPUFA
Percentage change in milk fat composition
Hypothesis:Processing Properties/Amount of
Protein in Milk
If protein with positive charge is made in milk:– Increase protein interactions
Promote faster RCTIncrease gel strengthAffect micelle size
– Novel processing properties– Novel products
If more protein was made in mammary gland:– More food for animal and human consumption– Increase cheese yield/lactation– Modify processing properties– Benefits producers and processors
Transgenic β- and κ-casein cows
To influence milk processing and overall protein levels
– 11.2 mg/ml κ-casein– 15.8 mg/ml β-casein– Altered κ-casein:total
casein ratio– Color change– Amount of fat and
minerals also affected
Brophy et al. 2003 Nat. Biotechnol. 21:157-162
Hypothesis:Animal Growth & Health
Improved disease resistance– Mastitis– Scours
Transgenic dairy cattle and mastitis
Lysostaphintransgenic cows
– Bacterial-derived hydrolase
– Mastitis challenge:71% control glands infected14% transgenic glands infected
– Effective against S. aureus only!
Wall et al. 2005 Nat. Biotechnol. 23:445-451
Hypothesis:Bacteria Levels
Types of bacteria in milk– Cold-spoilage– Lactic acid– Mastitis-causing
If an antimicrobial is made in milk:– Decrease overall level of bacteria in milk
-Stop/slow cold spoilage of milk-Stop/slow outbreaks of human illness from milk
– Affect cheese making???– Slow/stop infection in udder
Mastitis protection
Human lysozyme transgenic goats
Potential benefits:
– Healthier udder
– Changes in processing properties
– Anti-microbial activity
Expressed in goat milk at levels of 270 µg/ml
– 68% of human milk
20 kDa14 kDa
HLZ
Maga et al. 2006 J Dairy Sci 89:518-524
Anti-microbial activity:Improved animal/udder health
Somatic Cell Count (cells/100ml)
458,000*284,000All
609,000409,0003rd
474,000208,0002nd
351,000291,001st
HerdTransgenicParity
P<0.05
Processing properties
Decreased rennet clotting time
Increased curd strength
Implications for cheese manufacturing, types of cheese that can be made
Curd Strength
0102030405060
0 5 10Applied Stress (Pa)
Cur
dSt
reng
th
Anti-microbial activity:Lysozyme goat milk slows the growth of
some bacteria
Transgenic milk was bacteriostatic
– E. coli– S. aureus– P. fragi– S. cohnii– Corynebacteria spp.
Transgenic milk has increased shelf life
Maga et al. 2006 Foodborne Pathog Dis 3:384-392
Transgenic vs Additive
Inhibition of E. coli growth
-0.2
0
0.2
0.4
0.6
0.8
1
Reduction in Bacterial Growth
Added LysozymeAdded LactoferrinTransgenic
Antimicrobial activity:Potential to improve human health
Upper Lower Transgenic-Fed 28-8 190 10 28-9 140 20 28-16 7,400 1,100 28-17 80 1,400 Control-Fed 28-10 3,900 5,600,000 28-12 6,600 17,700 28-13 61,000 3,980,000 28-14 590,000 320
Pig Intestinal coliforms (CFU/gram)
Maga et al. 2006 Transgenic Res 15:515-519
Future Work
Desaturase expression
Generation of lactoferrin transgenic goats– First lactation started last week!
Impact of lysozyme milk on:– Mastitis– Processing – Disease prevention– Gut development
Artemis the Goat