Relationship between litter size at birth and within‐litter birth weight characteristics in laboratory mice as pilot animal for pig

Abstract

We investigated the relationship between litter size at birth and within-litter birth weight (BW) characteristics of laboratory mice as a pilot mammal for pig. We obtained records of number born alive (NBA) and total and mean litter BW (LWB, MWB), and maximum and minimum values of within-litter BW (MaxIWB, MinIWB), range and standard deviation (Range, SDIWB), skewness (Skew), and kurtosis (Kurt) of within-litter BW for 656 litters at first parity. Pearson's correlations of NBA were highly positive with LWB (0.92), weakly negative with MWB (-0.31), MaxIWB (-0.19), and MinIBW (-0.33), and those of MWB were negligible with Range, SDIWB, Skew, and Kurt (-0.10 to 0.06). Estimated heritabilities, treated as dam traits, were 0.32 for NBA, 0.39 for LWB, 0.24 for MWB, 0.28 for MaxIWB, 0.05 for MinIWB, 0.16 for Range, 0.17 for SDIWB, and 0.00 for Skew and Kurt. Estimated genetic correlation between NBA and LWB was high (0.95). Therefore, LWB could be promising for efficiently improving NBA. The estimated genetic correlation of NBA was negligible with MWB (0.00), positive with MaxIWB (0.10), Range (0.48), and SDIWB (0.36), and negative with MinIWB (-0.36), suggesting that selection for increased NBA brings larger SDIWB and lighter MinIWB.

Genetic Contributions of Genes on Sex Chromosomes and Mitochondrial DNA in a Pedigreed Population

“…To demonstrate the performance, we applied the rules for determining GCA I,A , GCX I,A , GCY I,A , and GCM I,A to the pedigree data from Fernando and Grossman [56] (Table 1). We also applied the same rules to mouse pedigree data from Ogawa and Satoh [57] (Table S1) in order to obtain GCA I,A , GCX I,A , GCY I,A , and GCM I,A of each of the G1 mice (50 males and 50 females) to each of the G8 mice (151 males and 152 females) (Table 2), and then we calculated the average genetic contributions, GCA I,popB , GCX I,popB , GCY I,popB , and GCM I,popB , of each G1 mouse to the population of 303 G8 mice.…”

“…Table 1 shows the toy sample obtained from Fernando and Grossman [56]. Table S1 is the pedigree data of a mouse population [57], an experiment was carried out over 2 years from 2018 to 2020, under the Regulations for Animal Experiments and Related Activities at Tohoku University (http://www.clar.med.tohoku.ac.jp/en.html) (lastly accessed on 1 October 2021). All mice were reared and handled according to the protocols approved by the Institutional Animal Care and Use Committee of Tohoku University [57].…”

“…All mice were reared and handled according to the protocols approved by the Institutional Animal Care and Use Committee of Tohoku University [57]. For breeding scheme, see Figure 1 in Ogawa and Satoh [57]. The mouse population was a total of non-overlapping 8 generations from G1 to G8 (Table 2).…”

“…Parent information on 100 G1 mice (50 male and 50 female mice) was unknown, and the 92 G1 mice (46 male and 46 female mice) had their offspring in G2. Nishida et al [54] proposed a goodness-of-fit test using the following values as chi-square statistics, to test whether the genetic contributions with respect to autosomal genes to a virtual offspring obtained from target population B are equal: A previous study [57] conducted this test for the contribution of the 92 G1 mice (M = F = 46) to the parents of each generation and confirmed that p-value was always >0.05.…”

“…Here, we developed a method for calculating the genetic contribution with respect to genes on the sex chromosomes and mitochondrial DNA, as an extension of the method for calculating that with respect to autosomal genes. We assessed the performance using the toy example obtained from Fernando and Grossman [56] and the pedigree data of laboratory mice of Ogawa and Satoh [57]. To verify the results of genetic contributions calculated using the mouse pedigree data, we performed a gene-dropping simulation [58] and compared the results from the simulation with the calculated genetic contributions.…”