Abstract
Conventional weaning of piglets at the young age of 3 to 4 wk is associated with reduced nutrient intake, reduced growth, altered behavioral patterns, and a greater susceptibility to diarrhoea. It is known that an older age at weaning is associated with an improved adaptation to postweaning challenges, e.g. changes
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in housing and diet. However, extending lactation length is economically undesirable, since this will postpone the establishment of a next pregnancy of the sow. Inducing oestrus and ovulation in sows by Intermittent Suckling (IS; piglets are temporarily separated from their sow for several hours on each day from a certain age until weaning) might be a possible way to retain the reproductive activity of sows during an extended lactation period and to improve postweaning adaptation of piglets. The general aim of the current thesis was to determine whether IS during an extended lactation improves the adaptation of piglets to weaning. More specific, we investigated how IS regimens, differing in separation interval, timing and duration, affected 1) piglet pre- and postweaning growth and feed intake, 2) piglet behavior during the suckling period, 3) postweaning gut characteristics. Parameters currently used to investigate postweaning gut characteristics in piglets are end-point measurements, but 4) we aimed to monitor postweaning intestinal function of piglets longitudinally. With regard to separation interval, distributing the daily 12-h separation period over two 6-h separation intervals did not yield a profit with respect to piglet growth or feed intake. Onset of IS at an older age (3 wk instead of 2 wk) markedly improved feed intake stimulation, and shortened the period of postweaning growth reduction when piglets were already weaned after 1 wk of IS. Although 1 wk of IS before weaning (4 wk) improved postweaning feed intake and growth and prevented the postweaning villous atrophy compared to conventionally weaned piglets, it did not prevent a profound growth check shortly after weaning. However, combining 1 wk of IS with an extended lactation (weaning at 5 wk) improved postweaning adaptation markedly in terms of growth and feed intake. Increasing the duration of IS during this extended lactation from 1 to 2 wk further improved, although slightly, growth and feed intake shortly after weaning. Besides IS regimens, we investigated whether plasma citrulline and intestinal fatty acid binding protein (I-FABP) concentrations could be longitudinal markers for small intestinal function in piglets after weaning. Although plasma I-FABP concentrations were unaffected by weaning, the marked postweaning decline and correlation with intestinal absorption posed the plasma citrulline concentration as a possible marker. However, since in a later study no correlations were found with small intestinal morphology, its use needs to be evaluated in future research. In conclusion, IS is a promising management strategy to improve the adaptation of piglets to weaning, by preventing postweaning detrimental effects on piglet nutrient intake, growth, and small intestinal morphology. These effects are most profound when IS is combined with an extended lactation. In addition, IS was not associated with the development of behavioral patterns indicative for piglet distress.
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