|
|
| Line 1: |
Line 1: |
| <!--
| | #REDIRECT [[Birth Weight old]] |
| To use this, add &preload=Template:Trait to the URL after
| |
| clicking on the Create button or redlink and reload the page
| |
| -->
| |
| | |
| <!--
| |
| Place brief trait definition/description here
| |
| -->
| |
| Calf birth weight is a good [[Indicator Traits | indicator trait]] for calving difficulty. If calving difficulty is a problem in the herd, and [[Calving Difficulty | calving ease EPDs]] are not available, selection of breeding animals for lighter birth weight may be an effective strategy to improve [[Calving Difficulty | direct calving ease]]. However, single trait selection for lighter birth weight or shorter gestation intervals may reduce calf viability<ref>[NEED REFERENCE HERE]</ref> and growth rate from birth to weaning.
| |
| ===Phenotype===
| |
| <!-- Describe ways the phenotype is collected
| |
| E.g., for birth weight discuss digital scale, mechanical scale, hoof tape, etc.
| |
| -->
| |
| Obtaining an accurate measure of birth weight (in pounds of calf) using a high-quality digital scale is important for producing meaningful [[Calving Difficulty | calving difficulty EPDs]]. However, it is not always feasible to obtain birth weights this way. Digital scales for measuring calf birth weights can cost thousands of dollars. Even with good mechanical scales, trying to catch a calf when the mother is being protective, and lifting that calf is a challenge for many producers and their ranch hands. There are reports of producers estimating the calf weights using visual inspection and this can be seen in many breed association birth weight datasets. Experience has shown these data are low accuracy, at best, and should not be submitted to breed associations and used in selection decisions.
| |
| | |
| ===Adjusted Value===
| |
| <!--
| |
| Discuss how values are adjusted. E.g., 205 day ww, sex X aod adjustments, ratios, etc
| |
| If the trait is not adjusted (e.g. Stayability) then say so
| |
| -->
| |
| Both sex of calf and [[Age of Dam | age of dam]] influence birth weight of the calf. BIF recommends the use of additive rather than multiplicative age of damage adjustment factors because research indicates that they are more appropriate<ref>[NEED CITATION].
| |
| | |
| Birth weight adjustments for the [[Age of Dam | age of dam]] can differ from one breed to another. Some breed associations have developed adjustments using their own data. All breed associations are encouraged to develop their own age of damage adjustment factors for birth weight.
| |
| | |
| <center>
| |
| Adj. Birth Wt. = Birth Wt. + Age of dam Adj.
| |
| </center>
| |
| | |
| Significant amounts of unfavorable [[Heterosis | heterosis]] have been observed in birth weight and should be accounted for if adjusting birth weights.
| |
| ===Contempory Group===
| |
| <!-- Discuss how contemporary groups are formed -->
| |
| Contemporary grouping for Birth Weight
| |
| # Breeder-Herd Code
| |
| # Year
| |
| # Season (January-June, July-December)
| |
| # Sex (Bull, Heifer)
| |
| # Birth Management Code
| |
| # Service Type (Embryo Transfer Calves)
| |
| ===Genetic Evaluation===
| |
| <!--
| |
| Discuss the genetic model for EPD production.
| |
| E.g., direct, maternal, permanent environment due to dam.
| |
| -->
| |
| Birth weight EPDs are generally produced using a multi-trait animal model that includes [[Weaning Weight | weaning weight]] and [[Yearling Weight | yearling weight]] (usually fit as [[Yearling Weight | is often fit as post-weaning gain]]).
| |
| | |
| While a maternal effect has been consistently observed on birth weight, it is always small with low heritability. Most analyses ignore the maternal effect and produce only additive direct genetic effect EPDs for birth weight.
| |
| | |
| | |
| ===Usage===
| |
| <!--
| |
| Discuss in what circumstances the trait is an ERT or an indicator trait and how the trait should be used and not used.
| |
| -->
| |
| | |
| In all situations, birth weight should be considered as only an [[Indicator Traits | indicator trait]]. In no situation is it an [[Economically Relevant Traits | economically relevant trait]]. When ERT EPDs are available, actual birth weights or birth weight EPDs should never be considered in a selection decision.
| |
