Suckling behavior and weight change of piglets were studied during the first 2 wk after birth. Thirty-six litters comprised a balanced comparison of parity number (first or second), litter size (8, 10 or 12), and two farrowing crate designs, one of which had a low horizontal bar that tended to impede the piglets' access to the udder. Piglets showed the expected preference for the anterior teats although the preference was more apparent in the second parity than in the first. Teat fidelity was most pronounced at the two ends of the udder; piglets occupying the middle positions did more fighting during suckling and missed the milk ejection more often. Within litter variation in 14-day weight increased with increasing parity number of the dam. Initial weight explained 30-40% of within-litter variation in 14-day weight. Behavioral variables explained 2.6% of additional variation in first-parity litters, 18.1% in second-parity litters, and 22.9% in litters of older sows. Suckling position (anterior to posterior) and teat fidelity (consistency of suckling position) were the two behavioral factors most closely associated with 14-day weight. Mean litter 14-day weight showed the expected effect of litter size, but showed no differences attributable to parity number or farrowing crate design. However, within-litter variation in 14-day weight was greater (P < 0.025) in the type of crate that impeded access to the udder. This may have been due to the somewhat higher levels of fighting, and to higher within-litter variance in fighting scores, seen in these crates.
Fraser, D., & Thompson, B. K. (1986). Variation in piglet weights: relationship to suckling behavior, parity number and farrowing crate design. Canadian Journal of Animal Science, 66(1), 31-46.