Piglet uniformity and mortality in large organic litters: Effects of parity and pre-mating diet composition

In large organic litters, relationships between piglet birth weight, piglet uniformity and pre-weaning piglet mortality were studied. Furthermore, effects of parity and insulin-stimulating diets during the pre-mating period on piglet birth weight, uniformity, and mortality were investigated. Organically kept sows (n = 137 sow cycles) were fed a control diet during lactation and weaning-to-insemination interval (CON), or an insulin-stimulating diet (sucrose plus lactose, both 150 g/d) during only the weaning-to-insemination interval (WII) or during the last two weeks of a 41 ± 4 d lactation and the weaning-to-insemination interval (LAC + WII). Piglets (live born and stillborn) were weighed individually within 24 h after birth. Cross-fostering was allowed within treatments within the first 3 d after birth. Litter size was higher for parities 3 and 4 sows compared with older sows, whereas parity 2 sows had an intermediate litter size (the number of total born piglets was 17.0, 18.8 and 16.3 for sows of parities 2, 3 + 4 and ≥ 5, respectively; P < 0.01). Mean birth weight (1.26 ± 0.02 kg) was not influenced by parity, but birth weight CV and percentage of piglets < 800 g increased with increasing parity class, after corrections for number of total born piglets (for parities 2, 3 + 4 and ≥ 5, respectively, CV of birth weights were 21.3, 23.2 and 24.8%, P = 0.05; and % piglets < 800 g were 6.2, 8.7 and 13.6%, P = 0.02). Pre-weaning piglet mortality also increased with parity class (20.9, 24.2, and 33.3% for parities 2, 3 + 4 and ≥ 5, respectively; P = 0.01). Litter characteristics at birth and pre-weaning piglet mortality were not affected by the insulin-stimulating diets before mating. Piglet mortality from d0 to 3 was strongly related with the number of total born piglets (β = 1.47%/piglet; P < 0.001), mean birth weight of the piglets (β = − 30.99%/kg; P < 0.001), CV of birth weights (β = 1.08%/%; P < 0.001) and % piglets < 800 g (β = 0.58%/%; P < 0.01). It is concluded that piglet birth weight and birth weight uniformity affect pre-weaning piglet mortality in organic sows with large litters. Piglet uniformity and piglet mortality were also affected by parity, but not by pre-mating insulin-stimulating diets.