Abstract :
[en] Estimates of standardized ileal digestibility (SID) of amino acids (AA) and energy utilization in sows have traditionally been based on feed ingredient databases developed for growing pigs or extrapolated from models designed for growing pigs, as reflected in the National Research Council (NRC) (2012) feeding tables. However, evidence suggests that sows differ from growing pigs in terms of energy and nutrient digestibility due to differences in body size and metabolism. The current nutritional databases lack precise digestible energy (DE), metabolizable energy (ME), and AA digestibility data specific to sows, particularly regarding how these values vary across physiological stages (gestation, lactation, post-weaning period) and parities. Therefore, in this PhD, we selected three common feed ingredients in pig diets, corn, barley, and wheat bran, to further evaluate their nutrient value and compare differences across sows’ physiological stages.
In the first experiment (Chapter III), we focused on nutrient digestibility, as well as the DE and ME values of these ingredients, highlighting differences between gestation, lactation, and the post-weaning period in primiparous sows. A total of 20 primiparous sows were used across gestation, lactation, and the post-weaning period in a randomized complete block design with dietary treatments (control, corn, barley, and wheat bran), where each treatment had 5 replicates. The gestation trial started on d 50 of pregnancy and lasted for 12 days (d 50 to d 62), while lactation and post-weaning trials both commenced at d 1 of their respective physiological periods. For primiparous sows, the apparent total tract digestibility (ATTD) of neutral detergent fiber (NDF) and gross energy (GE) in barley was higher during lactation than during the post-weaning period. Across all ingredients, the ATTD of NDF during lactation was higher than during the post-weaning period. However, no differences were observed in the energy values and digestibility of corn and wheat bran across the different physiological stages. This suggests that lactation enhances fiber digestibility in primiparous sows, likely due to higher energy demands and gut adaptation.
In the second experiment (Chapter III), we focused on nutrient digestibility, as well as the DE and ME values of these ingredients, highlighting differences among gestation, lactation, and the post-weaning period, but now in multiparous sows. Additionally, we compared the differences in digestibility and energy values of these three ingredients between primiparous and multiparous sows. A total of 24 multiparous sows were used across gestation, lactation, and the post-weaning period in a complete randomized design with dietary treatments (control, corn, barley, and wheat bran), where each treatment had 6 replicates. The gestation trial started on d 50 of pregnancy and lasted for 12 days (d 50 to d 62), while lactation and post-weaning trials both commenced at d 1 of their respective physiological periods. The DE and the ATTD of GE in wheat bran was higher during lactation than during the gestating period. For the three ingredients, the ME during lactation was higher than during gestation, and crude protein (CP) during lactation was higher than during the post-weaning period. Parity also influenced the nutrient utilization in sows. In gestation, primiparous sows showed a higher ATTD of GE for corn and barley than multiparous sows. while for wheat bran, they had a higher ATTD of CP, compared to multiparous sows. In lactation, primiparous sows had a higher ATTD of NDF and GE in barley compared to multiparous sows, but no differences in the ATTD of nutrients were found between primiparous and multiparous sows for corn and wheat bran. Moreover, during the post-weaning period, primiparous sows had a higher ME in corn than multiparous sows. However, regardless of the physiological stages, multiparous sows exhibited a higher ATTD of ether extract (EE) in barley than primiparous sows. These parity differences indicate that younger and older sows do not utilize EE and fiber equally, supporting parity-specific feeding strategies.
In the third experiment (Chapter IV), we determined the SID of CP and AA of corn, barley, and wheat bran in primiparous sows. Four physiological stages of primiparous sows were examined: a gestation stage where sows were restricted-fed, a lactation stage where sows were fed ad libitum, and then two post-weaning stages, an ad libitum fed phase followed by a restricted-fed phase. A total of 8 primiparous sows fitted with T-cannulas in the distal ileum were assigned to an 8×3 Youden square design with four diets (corn, barley, wheat bran, and Nitrogen (N)-free diet) and three periods, resulting in a total of six replicates per treatment. The basal endogenous losses (BEL) of CP and AA were determined after feeding an N-free diet. Regarding the SID of barley in gestating sows, only the SID of His was higher than in lactating sows and restricted-fed post-weaning sows and the SID of Gly was higher than in lactating sows. For wheat bran, the SID of Glu, Ser, and Tyr in gestating sows was lower than in lactating sows. The SID of Val and Tyr in lactating sows was higher than in ad libitum access post-weaning sows. For corn, the SID of Lys, Ala, and Gly in gestating sows was higher than in lactating sows. The SID of Ile, Lys, Phe, Thr, and Ala in gestating sows was higher than in ad libitum post-weaning sows. Our findings indicate that similar SID values are found for barley in different physiological stages of primiparous sows under the same diet and feed regime, whether ad libitum or restricted. However, for wheat bran, which has a high fiber content, lactating sows exhibited higher SID values compared to gestating sows for several AA. For corn, which has a low fiber content, gestating sows exhibited higher SID values compared to lactating sows and ad libitum post-weaning sows. These SID results show that high-fiber ingredients (wheat bran) are better digested during lactation, while low-fiber corn is better digested during gestation.
In summary, these findings highlight the effects of physiological stage on nutrient digestibility, DE, ME, and AA utilization in sows. The results emphasize the need for sow-specific nutritional data instead of relying on extrapolated values from growing pigs, providing a basis for precision feeding strategies in sow nutrition.
