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Internal Multiplication Versus Purchasing Replacement Females: Relative Genetic Cost of Production
by J.W. Mabry & T.J. Baas, Iowa State University
It is a biological certainty that in a swine herd females will go out of service on a regular basis due to many potential factors (age, soundness, death, disease, etc). There are two general approaches to replacing these females: purchase them from a genetic supplier or produce them within your own genetic system. While this is generally seen as a “capital management substitution”, there are costs associated with each method of replacement female procurement. The objective of this article is to compare the relative genetic cost of production incurred with these alternative forms of replacement female procurement.
In estimating the genetic cost of production for a specific genetic system there are several assumptions that must be made. The starting point is the reproductive productivity (pigs weaned/sow/year) from a parent female with 100% maternal heterosis in the farm facilities. In a genetic system where all replacement females are purchased, the entire sow herd should be capable of 100% maternal heterosis. With internal multiplication the producer is substituting a female with less than 100% maternal heterosis in place of some or all of the parent sows. Also, with internal multiplication a certain percentage of the sows are mated to maternal boars and the resultant pigs do not have maximum growth, leanness or feed conversion. These indirect costs of internal gilt multiplication must be accounted for to make accurate comparisons. Other assumptions that must be made include the number of GGP, GP and Parent females and males in the herd, cost of purchasing these animals and salvage value of culled sows and boars. If artificial insemination (AI) is used then assumptions for cost of semen per dose, number of doses per mating, litters/sow/year and farrowing rate must be made. If a parent female with 100% heterosis is replaced with a female that does not have maximum heterosis, then the reduction in reproduction (1) must be accounted for. Also, if maternal animals are produced that do not have the same growth, leanness and feed conversion as terminal cross animals, then these costs must be accounted for. Economic parameters such as interest rate, pig value, cost per day to market, feed cost, market weight, post-weaning mortality, annual replacement rates, selection fees or royalties and other incidental costs must also be included.
The Gencost® software (2) was used in estimating genetic cost of production for this article. The herd simulated for this research was a 2500 sow herd where the parent females had the potential for 24 pigs weaned/sow/year with annual replacement rates of 60% for all females and 50% for all males. Economic values of $8 (USD) per pig, $0.17 cost/day to market, $155 cost/ton feed, 265 lb (120 kg) market weight, 5% post weaning mortality and 8% capital costs were utilized. For the genetic system where all replacement females were purchased, a purchase price of $200 (USD) and salvage value of $120 were used. For the genetic system where gilts were produced internally a three breed roto-terminal cross was simulated with the top 300 sows being mated to maternal boars to produce replacement females at a production cost of $112. With a three breed roto-terminal cross program each female in the herd will have only 87% maternal heterosis (1). This was accounted for by reducing their reproductive performance by 1.5 pigs weaned/sow/year. The pigs in the maternal litters were assumed to have 0.1 poorer feed conversion, reach market in 2 more days and have $1.50 less carcass value since the offspring were not out of terminal boars. For the genetic system where purebred GGP females were utilized, a further reduction in the pigs weaned per sow per year must be made to account for the pure female having no maternal heterosis (-4 P/S/Y).
The following table summarizes the comparative genetic costs of production.
From the inputs and assumed parameters of this research, the practice of internal multiplication of replacement females offers the potential for cost savings with the purebred based GGP being the least cost alternative. It must be noted that internal multiplication involves additional investment in time and management by the producer that is not accounted for in this example. For example, the genetically superior females to be used for maternal mating must be accurately identified if the producer is to make similar genetic progress that can be obtained when replacement females are purchased. However, this is now available with BLUP genetic evaluation programs (3) linked with reproductive management programs such as PigChamp®. Additional management costs involved include maintaining identity of replacement females through the grow finish phase of the farm. This also assumes the availability of three maternal breeds. If only two maternal breeds are used there is an additional loss of heterosis by each sow in the herd which will increase the costs of internal multiplication.
1. Ahlschwede, WT. 1987. PIH-39.
2. Mabry, JW and M S Culbertson. 1997. United States, Copyright Office: TXU 781-587.
3. Mabry, JW, et al. 1994. UGA-CES Annual Research Report pp 6-8.
