The influence of suckling interval on milk production of sows.

The objective of this study was to determine whether sow milk yield per gland could be increased by reducing the interval between suckles (suckling interval). Eighteen sows were allocated at their first farrowing to three treatments comprising litter sizes of 6 or 12 piglets or a cross-suckling treatment that was imposed to increase suckling frequency. The cross-suckled treatment comprised two groups of six piglets each. Each suckling group was allowed to suckle the sow during 30-min intervals each day between d 6 and d 28 of lactation. The suckling interval was shorter (P < .05) for cross-suckled sows than for sows suckling single litters of 6 or 12 piglets during early lactation (d 10 to 14) and late lactation (d 24 to 28). Average piglet growth rate between birth and 28 d of age was greatest (P < .05) for piglets in the single litters of six and lowest for piglets in the cross-suckled treatments. Single litters of 12 piglets had the highest (P < .05) litter growth rates, followed by the cross-suckled litters and then the single litters of six piglets. The concentration of lactose and fat in milk from sows remained relatively stable, although milk from the cross-suckled sows contained more protein in early lactation (P < .05). Milk yield of sows was not significantly increased (P > .05) by the cross-suckle treatment, although during early lactation, milk yield tended to be greater from sows in the cross-suckle treatment than from sows suckling single litters of six (8,920 g/d vs 7,819 g/d, P < .1). The concentration of DNA and total RNA and the RNA:DNA ratio in mammary glands was unaffected by treatment (P > .05). Sows with single litters of 12 piglets had the greatest total DNA in their udders (P < .05). However, individual gland weights were heavier (P < .05) in cross-suckled sows than in sows with single litters of 6 or 12 piglets. Increased suckling frequency seemed to play a role in increased mammary gland weight and milk production during lactation.