The objective of the present study was to investigate factors associated with the risk of female pigs (females) becoming low lifetime efficiency sows (LE sows) in commercial herds.The factors investigated were age of gilts at first mating (AFM), number of services in parity 0 and pigs born alive (PBA) in parity 1. Farrowing records were obtained for 34,728 gilts entered into 101 commercial herds from 2001 to 2003.LE sows were defined as sows having lower 25th percentile of annualized lifetime PBA.AFM was categorized into six 21-day interval groups: 151-209, 210-230, 231-251, 252-272, 273-293 or 294-365 days.The PBA in parity 1 consisted of three groups : 7, 8-11 or 12 pigs.The number of services in parity 0 was categorized into two groups: non-returned to service or reserviced.Mixed-effects models were performed for statistical analyses.As AFM increased from the 151-209 to the 294-365 days, the proportions of females becoming LE sows correspondingly increase from 18.7 to 37.3% (P＜0.05).The proportion of females becoming LE sows was 10.3% higher for reserviced gilts than for non-returned gilts (P ＜ 0.05).Sows with PBA 7 pigs in parity 1 had 19.4 and 28.5% higher proportions of females becoming LE sows than those with PBA 8-11 and 12 pigs in parity 1, respectively (P＜0.05).In conclusion, in order to reduce the proportion of females becoming LE sows we recommend mating matured gilts at a lower age, reducing the percentage of reserviced gilts and increasing PBA in parity 1.
Sow lifetime performance and by-parity performance were analyzed using a 3 by 3 factorial design, comprising 3 herd productivity groups and 3 sow efficiency groups. Data was obtained from 101 Japanese herds, totaling 173,526 parity records of 34,929 sows, for the years 2001 to 2006. Sows were categorized into 3 groups based on the lower and upper 25th percentiles of the annualized lifetime pigs born alive: low lifetime efficiency sows (LE sows), intermediate lifetime efficiency sows or high lifetime efficiency sows. Herds were grouped on the basis of the upper and lower 25th percentiles of pigs weaned per mated female per year, averaged over 6 years: high-, intermediate- or low-performing herds. Mixed-effects models were used for comparisons. LE sows in high-performing herds had 57.8 fewer lifetime nonproductive days and 0.5 earlier parity at removal than those in low-performing herds (P<0.05). The number of pigs born alive of LE sows continuously decreased from parity 1 to 5, whereas those of high lifetime efficiency sows gradually increased from parity 1 to 4 before decreasing up to parity ≥ 6 (P<0.05). In conclusion, the LE sows have a performance pattern of decreasing number of pigs born alive across parity. The present study also indicates that high-performing herds culled potential LE sows earlier than the other herds.
本研究は，高繁殖生産性農場（High農場）と普通繁殖生産性農場（Ordinary農場）間で，低生涯生産性を示す母豚（LE母豚）の淘汰産次と淘汰理由の頻度分布割合，産次ごとの繁殖成績を比較することにより，LE母豚の淘汰パターンを特徴付けることを目的とした。本研究では，101農場における2001—2003年に導入された30,914頭の母豚を分析に用いた。母豚は，年間化生涯生存産子数の下位25パーセントタイルを基に，LE母豚と普通生涯生産性母豚の2グループに分類された。また，農場は年間種付け雌豚あたり離乳子豚数の上位25パーセントタイルを用いて，High農場とOrdinary農場の2グループに分類した。農場グループ間での淘汰産次と淘汰理由の頻度分布割合（%）の比較に，カイ自乗検定を用いた。統計分析には混合効果モデルを用いた。High農場のLE母豚は，Ordinary農場のLE母豚よりも，"繁殖障害"により産次1（54.0 vs. 41.5%）と産次2（61.2 vs. 42.2%）で多く淘汰された。どの産次グループにおいても，"繁殖障害"で淘汰されたLE母豚の生存産子数に，農場グループ間で差はみられなかった。結論して，High農場はOrdinary農場よりも，産次1と2において積極的にLE母豚を "繁殖障害"で淘汰していた。
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