Piglet birth weight and litter uniformity : importance of pre-mating nutritional and metabolic conditions

High piglet birth weights and litter uniformity are important for piglet survival and piglet performance. Within-litter variation in piglet birth weight is the consequence of within-litter variation in early embryo development, which in turn reflects variation in follicle and oocyte development. Insulin-stimulating diets before mating can influence litter development and uniformity, probably through beneficial effects of insulin on IGF-1 and follicle development. The first aim of this thesis, therefore, was to study effects of insulin-stimulating diets during the weaning-to-estrus interval (WEI) on plasma insulin and IGF-1 levels and follicle development, and consequences for embryo, fetal and placental development and uniformity at different stages of pregnancy in sows. Results of this thesis show that plasma insulin levels during WEI can be effectively enhanced by dietary sugars as dextrose and sucrose (high peaks directly after feeding) and starch (enhanced insulin levels at ~4h after feeding) in a dose-dependent manner. Follicle development and subsequent litter uniformity of embryos (at day 10 of pregnancy) or fetuses and placentas (at day 42 of pregnancy), however, were not affected by insulin-stimulating diets during WEI, nor related to plasma insulin and IGF-1 levels during WEI. Besides effects of pre-mating diets, plasma insulin and IGF-1 levels and follicle development are also influenced by the pre-mating metabolic state of the sow: in sows with severe body condition loss during lactation, plasma insulin and IGF-1 levels and follicle development at weaning are suppressed, and restoration of plasma insulin and IGF-1 levels and follicle development occurs in sows with a prolonged lactation or a prolonged weaning-to-pregnancy interval (WPI). The second aim of this thesis, therefore, was to study effects of these pre-mating conditions related to sow metabolic state on subsequent piglet birth weight and litter uniformity. In this thesis it is shown for the first time that pre-mating conditions related to sow metabolic state affect subsequent litter uniformity. Litter uniformity at birth was compromised by severe sow body condition loss during previous lactation and improved in sows with a prolonged WPI. Furthermore, it was shown that in (organic) sows with prolonged lactations (6 weeks) and large litters (17.4±0.3 piglets), insulin-stimulating diets before mating did not result in improved piglet birth weights or litter uniformity. This may be related to a restored follicle development at weaning in these sows. In these large organic litters, piglet birth weight and litter uniformity were strongly related to piglet survival during lactation. To conclude, results of this thesis confirm that litter uniformity at birth is already (partly) determined during the pre-mating period, likely related to (insufficient) restoration of follicle development. In contrast to previous studies, insulin-stimulating diets during WEI did not improve litter uniformity of embryos, fetuses or placentas and/or piglets in sows. The role of plasma IGF-1 levels and follicle development at weaning (both related to sow parity and sow body condition loss), and effects of insulin-stimulating diets during lactation, need further study. Finally, although effects of pre-mating nutritional and metabolic conditions on subsequent piglet birth weight and litter uniformity seem only marginal, these marginal effects can have substantial effects on pre-weaning piglet survival.</p

Effecten van eenvoudige koolhydraten en fermenteerbare koolhydraten op de binnentoom variatie bij varkens

2 proeven werden uitgevoerd. Het doel van de 1e was nader inzicht te krijgen in het mechanisme dat ten grondslag ligt aan de relatie tussen insuline-stimulerend voer (dextrose+lactose) tijdens het interval spenenovulatie, follikelontwikkeling in de laatste dagen voor inseminatie en (variatie in) ontwikkeling van embryo's tijdens de vroege dracht. Het doel van de 2e proef was om nader inzicht te krijgen in de directe effecten van de specifieke voercomponenten dextrose, lactose, sucrose en suikerbietenpulp (zowel apart als gecombineerd) op glucose, insuline en IGF-1 profielen in zeugen om zo diëten te vinden met de hoogste potentie om insuline en IGF-1 afgifte te stimuleren

Voer van invloed op biggensterfte

Marginale verschillen in voeding en metabolisme vóór inseminatie kunnen leiden tot grote verschillen in prenatale en postnatale biggensterfte. Dit was een van de conclusies tijdens het seminar van de leerstoelgroep Adaptatiefysiologie in Wageningen University

Nutritionally Induced Relationships Between Insulin Levels During the Weaning-to-Ovulation Interval and Reproductive Characteristics in Multiparous Sows: I. Luteinizing Hormone, Follicle Development, Oestrus and Ovulation

To get more insight in how insulin secretion patterns and corresponding insulin-like growth factor-1 (IGF-1) levels are related to luteinizing hormone (LH) secretion, follicle development and ovulation, 32 multiparous sows were fed either a dextrose plus lactose-containing diet at 4 h intervals (DL; each 150 g/day) or an isocaloric control diet at 12 h intervals (CTRL; containing soybean oil) during the weaning-to-ovulation interval (WOI). Insulin parameters (basal, peak levels and mean insulin) and IGF-1 levels during the WOI were similar for both treatments, but the insulin secretion pattern differed (related with feeding frequency and meal sizes). Oestrus and ovulation characteristics were not influenced by treatment. The LH surge was higher in CTRL compared with DL sows (3.73 vs 3.00 ng/ml; p = 0.03). Average diameter (6.5 vs 6.1 mm; p = 0.08) and uniformity (CV: 11 vs 15%, p = 0.02) of follicles =3 mm at day 4 after weaning was higher in CTRL compared with DL sows. Basal insulin levels were positively related with follicle diameter at ovulation (ß = 0.05 mm/(µU/ml); p = 0.04) and negatively related with LH surge level (ß = -0.07 (ng/ml)/(µU/ml); p = 0.01). Insulin area under the curve (AUC) (ß = 0.037 (ng/ml)/1000 µU; p = 0.02) and IGF-1 levels (ß = 0.002 (ng/ml)/(ng/ml); p <0.01) were positively related to basal LH level around the LH surge. From these data, we conclude that insulin and IGF-1 levels during the WOI are related to LH secretion and follicle development. Not only the absolute level of insulin seems important, but also the pattern within a day in which insulin is secreted seems to affect LH secretion and development of pre-ovulatory follicles