台灣批次生產系統下藍瑞斯母豬離乳至配種間隔及其與產仔性狀之遺傳評估

Abstract

離乳至配種間隔（weaning-to-service interval, WSI）為影響母豬非生產天數及豬場繁殖效率的重要性狀之一。當WSI延長時，母豬離乳後至再次受孕前的空窗期增加，進而降低年產胎數並增加飼養成本。此外，在台灣高溫高濕的海島型氣候條件下， WSI可能更容易受到環境的影響。因此，為評估 WSI 作為台灣母豬繁殖性狀遺傳改良目標之可行性，本研究利用台灣氣候環境條件下所取得的現場數據以評估WSI之遺傳參數。 本研究資料取自台灣北部（豬場一）與中部（豬場二）兩個種豬場，蒐集2017年至2024年間之藍瑞斯配種、分娩及離乳記錄。豬場一採一週批次生產系統，包含641頭母豬與2,691筆原始記錄；豬場二採三週批次生產系統，包含960頭母豬與2,888筆原始記錄。其中，豬場二透過使用律期媒以達成發情同期化，因此三週批次生產系統下的WSI會受到律期媒的人為干擾，故本研究依其批次管理流程校正WSI天數。經資料篩選後，豬場一、豬場二及兩場合併資料分別包含556、925及1,460頭母豬，分別為1,806、2,614及4,060筆記錄。 由於WSI呈右偏分布，本研究比較未轉換WSI及三種轉換方式。結果顯示，T1（log10）轉換在豬場二及兩場合併資料具有較佳的殘差常態性，且遺傳率估計較穩定。單性狀分析結果顯示，胎次間隔在三個資料集中均達顯著水準，且兩場皆以1–2胎次間隔之WSI最高，表示初產母豬離乳後較容易出現配種延遲。豬場一之離乳年份、哺乳期長度及其二次項達顯著水準；豬場二之離乳季節、離乳窩仔數、哺乳期長度及離乳窩重達顯著水準。兩場合併資料中，胎次間隔、離乳季節、場別、哺乳期長度及其二次項均達顯著水準。 採用T1轉換後，豬場一、豬場二及兩場合併資料之WSI單性狀遺傳率分別為0.0335、0.1171及0.0916，屬於低遺傳率，顯示WSI可能主要受環境與管理因素影響，但仍具有一定遺傳變異可供評估。此外，雙性狀分析整體結果顯示，WSI與總產仔數（TNB）之遺傳相關介於 −0.1299至0.1975，呈現低度相關；WSI與活仔數（NBA）之遺傳相關則介於0.1546至0.5184，呈低至中度正相關。然而，各遺傳相關估計皆伴隨較大標準誤差。 綜上所述，本研究結合台灣季節變化、不同生產系統特性及母豬胎次表現等因素，建立藍瑞斯母豬 WSI 之遺傳評估架構，並獲得遺傳參數的估計結果，為未來相關研究與母豬繁殖性狀遺傳評估提供參考依據。

Weaning-to-service interval (WSI) is an important reproductive trait affecting sow non-productive days and reproductive efficiency in pig production. Prolonged WSI increases the interval between weaning and subsequent conception, thereby reducing the number of litters produced per sow per year and increasing production costs. Under the hot and humid climate of Taiwan, WSI may also be affected by environmental and management conditions. Therefore, this study aimed to estimate the genetic parameters of WSI using field data collected from Landrace sows in Taiwan and to evaluate its potential use in genetic evaluation of sow reproductive traits. The data were obtained from two breeding pig farms located in northern Taiwan (Farm 1) and central Taiwan (Farm 2), and included mating, farrowing, weaning, and pedigree records from 2017 to 2024. Farm 1 used a weekly batch production system and included 641 sows with 2,691 raw records, whereas Farm 2 used a three-week batch production system and included 960 sows with 2,888 raw records. Because Farm 2 used altrenogest for estrus synchronization, WSI records in this farm were adjusted according to its batch management procedure. After data filtering, the Farm 1, Farm 2, and combined datasets included 556, 925, and 1,460 sows, with 1,806, 2,614, and 4,060 records, respectively. Because WSI showed a right-skewed distribution, untransformed WSI and three transformed WSI variables were compared. The T1 transformation (log10) showed better residual normality in Farm 2 and the combined dataset and produced relatively stable heritability estimates; therefore, T1-transformed WSI was used in subsequent analyses. In the single-trait analysis, parity interval was significant in all three datasets, and the highest WSI was observed between parities 1 and 2 in both farms, indicating that primiparous sows were more likely to have delayed service after weaning. In Farm 1, weaning year, lactation length, and the quadratic term of lactation length were significant. In Farm 2, weaning season, litter size at weaning, lactation length, and litter weight at weaning were significant. In the combined dataset, parity interval, weaning season, farm, lactation length, and the quadratic term of lactation length were significant. After T1 transformation, the heritability estimates of WSI were 0.0335, 0.1171, and 0.0916 in Farm 1, Farm 2, and the combined dataset, respectively, indicating low heritability. These results suggest that WSI is largely influenced by environmental and management factors, although genetic variation remains present. In addition, the overall bivariate analysis showed that genetic correlations between WSI and total number born (TNB) ranged from −0.1299 to 0.1975, suggesting low genetic correlations between the two traits. Genetic correlations between WSI and number born alive (NBA) ranged from 0.1546 to 0.5184, indicating low to moderate positive correlations. However, all genetic correlation estimates were associated with relatively large standard errors. In conclusion, this study established a data filtering, transformation, and genetic evaluation framework for WSI in Landrace sows under different batch production systems in Taiwan. The results indicate that WSI is affected by parity, lactation-related traits, season, farm, and management conditions, and that its heritability is low. Further accumulation of records, improvement of pedigree completeness, and inclusion of additional management information may help improve the accuracy of genetic parameter estimation for WSI and its relationships with litter traits.