Feeding sows during the transition period—is a gestation diet, a simple transition diet, or a lactation diet the best choice?

Three experiments were carried out to study whether a gestation diet, a simple transition diet, or a lactation diet is the best choice in late gestation and when sows preferably should be transferred to a high crude protein (CP) lactation diet. In experiment 1, 35 sows were fed either a gestation diet (12.1% CP), a lactation diet (15.9% CP), or a 50/50 mix (simple transition diet; 14.0% CP) from 6 d before parturition until parturition, to study the impact on farrowing and colostrum performance. In experiment 2, 90 sows were studied from 6 d before parturition until weaning at day 24 and they were fed one of five strategies: a gestation diet until day 3 or day 10 of lactation (strategy 1 and 2) and then lactation diet; a simple transition diet until day 3 or day 10 (strategy 3 and 4) and then lactation diet; or a lactation diet throughout the study (strategy 5). In experiment 3, 124 sows were fed strategy 1 or 5. Sows were weighed and back fat (BF) scanned when entering the farrowing unit and at day 2, 10, 17, and 24. Piglets were weighed at birth and after 24 h, and colostrum production was studied (experiment 1). Litter weight at day 2, 10, 17, and 24 was recorded, milk and blood samples were collected weekly and sow fat and protein mobilization, and balances of energy, N, and Lys were calculated from day 3 to 10 of lactation (experiment 2). Total- and live born piglets, and frequencies of stillbirth and piglet diarrhea were recorded (experiment 3). Feeding sows a gestation diet, a simple transition diet, or a lactation diet showed no evidence of effects on colostrum production or farrowing process (experiments 1 and 3) or lactation performance (experiments 2 and 3). Compared to previous studies, sows had a poor milk yield. Plasma urea was elevated (P < 0.001) indicating CP oversupply prior to parturition in sows fed the lactation diet as compared with the two other diets. According to calculated balances, all dietary strategies supplied insufficient amounts of N and Lys from day 3 to 10, indicating that the best choice is to feed sows with a high CP lactation diet from parturition and onwards. Primiparous sows had a higher plasma insulin concentration (P < 0.01), lower colostrum yield (P < 0.01), and higher frequency of piglet diarrhea (P < 0.001) than multiparous sows. In conclusion, in our conditions (high CP in gestation diet; poor milk yield; restricted feeding in early lactation), sow performance was not compromised by the dietary strategies, but results indicate that primiparous and multiparous sows should be fed differently.