Effect of Environment on the Expression
of Breed and Heterosis Effects for
Production Traits
Bryant J. R. et al, 2007
Institute of Veterinary, Animal and Biomedical Sciences, Massey University
American Dairy Science Association
Presented by
EMAD M. A. SAMARA
Introduction
• The Performance of dairy breeds in different environments
has been evaluated in a number of recent studies which shown
that
– Not all breeds perform equally in each environment.
– Crosses among breeds can result in significant improvements in
production and survival traits over the average of the parental breeds
• Heterosis effect
– Environment influence the expression of Heterosis
• Complicating the estimation of crossbred performance
• Genetic variation in environmental sensitivity of dairy cattle
sires also have been reported
– Measured by phenotypic responses of their progeny to different
environments (nutritional, climatic ..etc)
– Results in an increase in phenotypic differences
• Scaling Effect
Introduction
• Sires Reranking
• Depend largely on Scaling Effect
• Large variations in environment
• Progeny of some sires are not expected to perform to their optimum in
different environment
• Environmental factors that cause reranking
– Nutritional (or production) Environment
» Classified on the basis of herd averages or standard deviations for total
or peak yields of milk, fat, or protein
» Absence of information on levels and types of feeds offered
– Climatic Environment
» Temperature Humidity Index (THI)
» Heat Load Index (HLI)
– Herd Size
» Actual group size of the herd.
» Number of first-lactation animals
Objective
• The objectives of my papers was ..
– Quantify if environment within New Zealand influenced the expression
of breed and heterosis effects.
– Determine if sires can be used with confidence throughout New
Zealand in any environment
– Determine if variations in Environmental factors (Nutritional, climate,
and herd size) cause sires reranking.
– Discuss ..
– Sire X Environment interactions
– Genotype X Environment interactions
– Heterosis X Environment interaction
Study Design
• Study Design
– 13 yr (1989-2002) of Progeny Test Records of 184,288
First-lactation (2-yr-old) records of milk, fat, and protein
yield from Straight and Cross breed animals.
– A univariate multibreed sire model was applied within
character state environments
– Production Traits used
• Milk Yield/Heterosis
• Fat Yield/Heterosis
• Protein Yield/Heterosis
Study Design
• Study Design
– Character States Environments
• Herd-average total lactation yield of fat plus protein (MS)
– Feed consumption levels
– 227, 263, 305, and 376 kg
• Heat load index (HLI),
– Degree of heat stress
– 61.4, 64.7, 67.2, and 69.6
• Herd Size
– Competition stress
– 154, 263, and 414
• Altitude
– 50, 178, and 367 m above sea level
• These environmental factors were chosen to study the genotype x
environment interaction
Study Design
• Observed Breed Deviations from a New Zealand Friesian (NZF) for
– Overseas Holstein-Friesian (OHF)
– New Zealand Jersey (NZJ )
– Others.
• Observed Heterosis for diff. Crosses
• OHF x NZJ
• OHF x NZF
• NZF x NZJ
• Estimating Expected Performance of
• Straight breeds (OHF, NZJ, and NZF).
• Cross breeds (OHF x NZJ, OHF x NZF, and NZF x NZJ)
Observed Breed Deviations from a
New Zealand Friesian (NZF)
• In all environments of all breeds
– The highest milk and protein yields
• OHF cattle
– The highest fat yields
• NZF cattle
– The lowest milk, fat and protein yields
• NZJ cattle.
• Scaling Effect
– Genotype x Environment interaction
– Between OHF and NZJ breeds
• For milk, fat, and protein yield in relation to MS yield
– Differences in yield between these breeds
• Numbers at low\intermediate\high environment
– Difference in milk, fat, and protein yields and feed intake between Jersey and
Friesian cattle was observed in some studies to be greater on a concentrate
than on a roughage diet.
Figure 1. Observed breed deviations from a New Zealand Friesian NZF base for overseas Holstein-Friesian OHF (O),
New Zealand Jersey NZJ (□), and other (∆) for (a) milk yield, (b) fat yield, and (c) protein yield in relation to production
level of fat plus protein (MS yield), heat load index (HLI), herd size, and altitude.
Observed Heterosis for diff. crosses
• Heterosis levels for milk and protein yield
– Calculated as a percentage relative to the phenotypic average of the parental
breeds
– Highest for OHF x NZJ cross, followed by NZF x NZJ and OHF x NZF
• Heterosis levels at low\intermediate\high environment for MS and HLI
environments
– For OHF x NZJ Cross
– For OHF x NZF Cross
» Suppressed in low MS yield (insufficient Nutrient supply ) and in high HLI
environments (Elevated metabolic rate)
» Not significantly different from zero.
– For NZF x NZJ Cross
• Heterosis levels for fat yield
– OHF x NZF Cross were suppressed in low MS yield and in high HLI and high
altitudes environments
• The largest heterosis estimates were obtained for OHF x NZJ cross cattle
(from 5.0 to 9.5%) in all yields.
Figure 2. Observed heterosis for crosses between overseas Holstein-Friesian and New Zealand Jersey OHF x NZJ (O), New Zealand Friesian
and New Zealand Jersey NZF x NZJ ( x), and overseas Holstein-Friesian and New Zealand Friesian OHF x NZF (◊) for (a) milk yield, (b) fat
yield, and (c) protein yield in relation to production level of fat plus protein (MS yield), heat load index (HLI), herd size, and altitude.
Estimating Expected Performance
• Expected performance in all environments of major breeds
and first breed crosses
– Milk and Protein yields
• Highest in OHF origin
– Comparing with straight or crossbred animals.
• Minimal differences in milk and protein yield performance between
OHF, OHF x NZF and OHF x NZJ
– Expression of heterosis effects in the cross.
– Fat yields
• Crosses (OHF x NZJ, OHF x NZF, or NZF x NZJ) generally
higher than straight breeds (OHF, NZJ, and NZF).
Figure 3. Estimated performance of overseas Holstein-Friesian (OHF;• ), New Zealand Friesian (NZF; ◆), New Zealand
Jersey (NZJ; ■), OHF x NZF (+), OHF x NZJ (x), and NZF x NZJ (-) for (a) milk yield, (b) fat yield, and (c) protein yield in
relation to production level of fat plus protein (MS yield), heat load index (HLI), herd size, and altitude.
Conclusion
• In conclusion,
– In observed scaling effect between OHF and NZJ cattle in relation to
MS yield environment,
• Suggest that if OHF are managed and selected in an intensive feeding
system, are better suited to a high and low MS yield environment than
NZJ, which were traditionally selected for performance on a pasture-based
diet.
– Significant gains in performance over the averages of parental breeds
can be utilized by crossing OHF and NZF with NZJ cattle,
• With environment can affect the heterosis effect.
• accounted for greater feed costs of larger animals (OHF and NZF)
compared with smaller animals (NZJ)
Conclusion
• In conclusion,
– Expression of heterosis is dependent on the environment in which
breed crosses are managed and is generally greater in a stressful
environment than in a supportive environment.
• Heterosis x environment interactions
– Vary
– Definite conclusions on environment-dependent expression cannot be
made.
– The largest heterosis estimates were obtained for crosses between
OHF x NZJ cattle (5.0 to 9.5%),
• Crosses between these 2 breeds result in individuals that have a high
proportion of heterozygous loci with complementary attributes leading to
significant increases in performance over the average of the parental
breeds
• Positive heterosis, OHF x NZJ  distinct breeds
– Significant genetic differences between these breeds.
“ Shoot for the moon
Even if you miss it,
you will land among the stars….! “
Les Brown