Abstract Due to genetic selection for large litters in pig production, piglets are often supernumerary to the teats on the sow. Providing milk replacer as a second feed source is increasingly being used to rear large litters. This results in increased competition at the udder when all piglets remain at the sow. We hypothesise that larger litter size and being amongst the smaller piglets within-litter (irrespective of absolute weight) is associated with increased likelihood of drinking milk replacer as a supplement to suckling or to compensate for low suckling success. The study design was 2 × 2 factorial with two standardised litter sizes at day 1 (LSD1) of either 14 piglets (LS14) or 17 piglets (LS17) and two housing conditions in either crates (CRATE) or loose housing (LOOSE). If piglets died, they were not replaced. The piglets’ suckling and drinking behaviour along with their growth rate was recorded weekly. The results showed a clear preference for suckling the sow over milk replacer. None of the piglets changed entirely to drink milk replacer. LS17 compared to LS14 was associated with more piglets with low suckling success (P ≤ 0.05) and the risk of having low suckling success was higher for the smaller piglets within-litter (P ≤ 0.05). About half of the piglets with low suckling success were able to compensate and sustain growth by drinking milk replacer (P ≤ 0.05). The largest piglets within-litter were more likely to drink milk replacer as supplement to high suckling success compared to only suckling (P ≤ 0.05). When taking into account the absolute weight of the piglets in the start of the week, piglets drinking milk replacer in addition to suckling had a higher growth rate in the following week compared to piglets who did not supplement suckling with milk replacer (P ≤ 0.05). Thus, the present study could confirm that some of the piglets experiencing a competitive disadvantage at the udder could compensate with milk replacer. However, the milk replacer was mainly used by the larger piglets within-litter and as a supplement to increase growth of piglets who had access to a teat. Several factors may have affected the piglets’ ability to use the milk replacer: high effort to drink from the milk cup due to inadequate design, poorer nutrient quality of milk replacer than of sow milk, and/or suckling the sow satisfies other behavioural and physiological needs than solely nourishment.

中文翻译：

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在两种饲养条件下，大窝产仔数和仔猪体重差异对高产母猪窝使用代乳粉的影响

摘要 由于生猪生产中对大窝的遗传选择，仔猪往往多于母猪的乳头。提供代乳品作为第二饲料来源越来越多地用于饲养大窝。当所有仔猪都留在母猪时，这会导致乳房竞争加剧。我们假设较大的窝产仔数和在窝内较小的仔猪（无论绝对体重）与饮用代乳品作为哺乳补充或补偿低哺乳成功率的可能性增加有关。研究设计为 2 × 2 阶乘，在第 1 天 (LSD1) 有 14 头仔猪 (LS14) 或 17 头仔猪 (LS17) 的两个标准化窝产仔数，以及在板条箱 (CRATE) 或松散猪舍 (LOOSE) 中的两种饲养条件。如果仔猪死亡，则不会更换。每周记录仔猪的哺乳和饮水行为以及它们的生长速度。结果表明，母猪明显更喜欢用母乳代替代乳品。没有仔猪完全改变为喝代乳品。与 LS14 相比，LS17 与更多的低哺乳成功仔猪（P ≤ 0.05）相关，并且窝内较小的仔猪的低哺乳成功风险更高（P ≤ 0.05）。大约一半的低哺乳成功仔猪能够通过饮用代乳品来补偿和维持生长（P ≤ 0.05）。与仅哺乳相比，窝内最大的仔猪更有可能饮用代乳品作为高哺乳成功的补充（P ≤ 0.05）。在考虑周初仔猪的绝对体重时，与未补充母乳喂养的仔猪相比，补充母乳喂养的仔猪在接下来的一周内有更高的生长率（P≤0.05）。因此，本研究可以证实，一些在乳房上处于竞争劣势的仔猪可以用代乳品来弥补。然而，代乳品主要由窝内较大的仔猪使用，并作为一种补充剂来促进有乳头的仔猪的生长。有几个因素可能会影响仔猪使用代乳品的能力：由于设计不当，从奶杯中喝水费力，代乳品的营养质量比母猪乳差，和/或母猪哺乳满足其他行为和生理需要而不仅仅是营养。