Nineteen Dutch pig farms with a total population of more than 7,000 sows were visited and the managers completed a questionnaire. Crucial factors that influence piglet birthweight were defined, based on the differences in management factors between farms. The most important conclusion of this study is that besides feeding in the gestation phase, feeding the sow during the lactation and insemination phases also has a major influence on birthweight.

Therefore, how a sow is fed throughout her entire productive life plays a key role in the birthweight of her piglets.

Lactation and Insemination

Feed intake during the lactation phase is important for a high birthweight of the next litter, as it gives the sow the nutrients she needs to prepare her body for the subsequent reproduction. Energy intake (crude fat + starch and sugar) seems to be important for a good recovery of the sow. However, whether the higher birthweight of the piglets was caused by higher feed intake or higher energy intake is not entirely clear from the study.

Feed intake during the insemination period also affects the birthweight. The TOPIGS researcher found that one kilo of extra feed intake per day during the insemination period results on average in a 45-gram higher birthweight of the piglets. Boosting the feed intake during this period therefore seems to be a worthwhile option. Interestingly, sows fed with lactation diets during the insemination period had piglets that were on average 51g heavier than those from sows fed with gestation diets during insemination period. This indicates that the nutritional composition (energy and digestible protein levels) of the feed leads to differences in birthweight.

Other factors found to influence piglet birthweight were feed intake during gestation, the type of housing, use of prostaglandins, quarantine periods for gilts, and the hygiene level. However, not all of these findings were statistically significant. For further information, see the section 'Factors That Influence Piglet Birthweight' below.

442 grams extra

Beside the effects found for intake, the research showed some other results as well.

Overall, it can be concluded that sows on a farm farrow heavier piglets when:

• gilts are introduced via a quarantine procedure
• sows are housed in groups
• there is no use of prostaglandins at farrowing
• sows are fed with lactation diets from weaning to insemination
• hygiene on the farm is very good.

In theory, if all of these factors are combined this will result in a piglet birthweight 442 grams higher compared to a farm that:

• does not apply quarantine
• does not use group housing
• uses prostaglandins at farrowing
• feeds sows gestation feed in the insemination period
• has an average farm hygiene

Factors That Influence Piglet Birthweight

• Litter size: every one piglet extra per litter decreases piglet birthweight by 30 to 50 grams
• Cycles per year: every 0.1 litter extra per year decreases piglet birthweight by 56 grams
• Feed intake during the insemination phase: 1 kilo extra feed intake per day increases piglet birthweight by 45 grams
• Gestation phase feed intake: 1 kilo extra feed intake during gestation increases piglet birthweight by 1.2 grams
• Higher levels of intake of digestible lysine during the gestation phase tends to increase piglet birthweight
• Higher levels of crude fat intake by the sow during the lactation phase increases piglet birthweight
• Trends that give increased birthweight
  • Quarantine gilts (+39 grams)
  • Group housing (+61 grams)
• Trends that give decreased birthweight
• Use of prostaglandins (-41 grams)