Culling reasons in organic and conventional dairy herds and genotype by environment interaction for longevity

T. Ahlman. , B. Berglund., .L. Rydhmer. , E. Strandberg - ScienceDirect

Type: Research Paper
Knowledge level: Advanced

Farm Table says:

Organic agriculture is based on 4 ethical principles: health, ecology, fairness, and care. Different preferences may influence the need for alternative selection indexes for organic production, with different weightings of traits, or a separate breeding program. However, no genotype by environment interaction of importance was found between the production systems.

The aim of this study is to compare dynamics in culling reasons between organic and conventional production and to analyze genotype by environment interactions for longevity.

Average Values for Longevity Traits:

• Length of productive life- 6 years

• Survival through first, second, and third lactations

• Fertility-determined survival

• Udder health-determined survival.

 The risk of being culled due to poor udder health – greater for organically managed cows.

 The differences in culling due to poor udder health between production systems may be due to differences in performance of cows in the different environments, or to differences in culling criteria because of ethical considerations.

Reasons for Culling:

• In organic herds most cows were culled due to poor udder health (occurred at a lower age in organic production)

• In conventional herds were most commonly called due to low fertility.

• The farmers’ use of the code “unspecified cause” has not been directly connected to any specific reason for culling. The use of this code is therefore not likely to affect the results.

Culling Criteria:

• The standards prescribe the limited use of antibiotics and withdrawal periods that are usually twice as long after medical treatment, compared with conventional production, which affects farm economy.

• differences in ethical considerations between organic and conventional farmers may be involved because animal health and integrity are thought to have a higher value in organic production compared with conventional systems.

Swedish Holstein:

• Poor udder health is expected in this breed, but no breed by environment interactions of importance have been found in organic and conventional production in Sweden.

• The differences found indicate that organic farmers have a lower tolerance for poor udder health, compared with conventional farmers.

Swedish Red:

• commonly considered to be more robust than the Swedish Holstein.

• the breeds are expected to react in the same way to changes in the environment. The different expectations of farmers may, therefore, be unfounded but still influence their decision making.

Genetic Correlations:

Genetic correlations for longevity traits expressed in organic and conventional dairy production systems in Sweden are close to unity, except for fertility determined survival in the Swedish Red breed which is significantly different from unity. The reason for this low correlation is not clear. Genotype by environment interactions does not exist for fertility traits in this indicating that the same genes are important for fertility in both production systems.

Heritabilities:

• No distinct pattern was found regarding production system or breed for the heritabilities estimated for longevity traits in this study.

• However, the heritabilities for survival increased with lactation number.

• The magnitude of heritabilities estimated for longevity traits in organic production indicates that breeding for longevity also within the organic system would be possible.

Future Scenarios for Organic Breeding:

• Debate exists regarding which reproduction techniques should be allowed in organic production and the use of conventionally bred bulls (may become restricted.

• Research about traits important in the organic dairy production and the relative importance of different traits will show whether separate breeding goals need to be developed for organic production.

• Growing organic populations and development of less costly breeding programs than the ones used in conventional production today will increase the possibilities for an organic breeding strategy in the future.

• The use of genomic selection should also be considered for organic production, because it may increase the genetic gain in functional traits and can be used for increasing genetic diversity by identifying outcross bulls.

• On the other hand, genomic selection is expensive and requires a large reference population, which may limit the use of the technique if the breeding should be performed entirely within the organic production.

2011 - Sweden - T. Ahlman. , B. Berglund., .L. Rydhmer. , E. Strandberg - ScienceDirect
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