Farrowing duration is rather long in sows most likely due to selection for large litters, and we hypothesized that prolonged farrowings would compromise sow energy status during farrowing and in turn the farrowing process. Two studies were performed as follows: 1) to evaluate whether sow energy status during farrowing compromise the farrowing kinetics (FK, i.e., farrowing duration and birth intervals) and 2) to study the underlying mechanisms potentially affecting stillbirth rate and farrowing assistance. In study-1, parameters affecting FK were characterized based on data from a total of 166 farrowings from 7 feeding trials focused on sow colostrum production. The data were screened for associations with FK using the CORR procedure of SAS. Traits that were correlated with the FK at P < 0.05 were included in a multivariate regression model. Time since last meal until the onset of farrowing greatly affected the farrowing duration (r = 0.76; n = 166; P < 0.001) and a broken-line model was fitted to describe that relationship. According to the model, farrowing duration was constant (3.8 ± 1.5 h) if the farrowing started before the breakpoint (3.13 ± 0.34 h after the last meal), whereas farrowing duration increased to 9.3 h if the farrowing started 8 h after the last meal. Subsequently, sows were divided into 3 categories based on that trait (≤3, 3 to 6, and >6 h) to evaluate the impact on birth intervals, farrowing assistance, and stillbirth rate. Birth intervals (P < 0.001), odds for farrowing assistance (P < 0.001), and odds for stillbirth (P = 0.02) were low, intermediate, and high when time since last meal was ≤3, 3 to 6, and >6 h, respectively. In study-2, blood samples were collected once or twice each week in late gestation and each hour during farrowing to measure arterial concentrations and uterine extractions of plasma metabolites. Time since last meal was strongly negatively correlated with arterial glucose 1 h after the onset of farrowing (r= -0.96; n = 9; P < 0.001). Glucose appeared to be the key energy metabolite for oxidative metabolism of gravid uterus. In conclusion, the present study strongly suggests that a substantial proportion of sows suffer from low-energy status at the onset farrowing and that this negatively affects the farrowing process. Transferring this knowledge into practice, the results suggest that sows should be fed at least 3 daily meals in late gestation.

The objective of the current study was to quantify loss of energy in feces, urine, heat, and milk, to evaluate feed efficiency and to evaluate optimal ratio of dietary CP to energy for lactating sows fed increasing dietary CP. A total of 72 sows were included in the experiment from day 2 after parturition until weaning at day 28. Sows were allocated to 6 dietary treatments formulated to be isocaloric (9.8 MJ NE/kg) and increasing standardized ileal digestible (SID) CP (11.8, 12.8, 13.4, 14.0, 14.7, and 15.6% SID CP). Sows were weighed and back fat scanned within 2 d after farrowing, at days 18 ± 3 and 28 ± 3. Litters were standardized to 14 piglets within 2 d after farrowing and weighed at day 1 or 2 and at days 11, 18, and 28 (within ± 3 d). Feed intake (feed supply minus residue) was registered, and milk, urine, and fecal samples were collected at days 4, 11, and 18 (within ± 3 d). Sow milk yield was estimated from litter gain and litter size, and sow heat production was calculated factorially. On days 4 and 18 (±3 d), sows were enriched with D 2 O (deuterated water) to estimate body protein and fat pool size. Overall, sow BW loss, back fat loss, fat and protein mobilization, litter size, and piglet performance were not affected by diets, except for sows fed treatment 5, which had lower ADFI and lower milk production, and a tendency to lower piglet ADG compared with the remaining treatment groups (P < 0.01, P = 0.03, P =0.08, respectively). Relative to GE intake, the energy excreted in urine increased from 3.3% to 5.3% (P < 0.001), whereas energy lost as heat increased numerically from 54.5% to 59.0% with increasing dietary CP. The feed efficiency as evaluated by NE corrected for body mobilization peaked when sows were fed at their requirement (treatment 2; 12.8% SID CP; P = 0.01), whereas the feed efficiency was 1% lower for treatment 1, whereas it was 3% to 6% lower for treatments 3 through 6. In conclusion, energy loss in urine and likely also energy lost as heat increase if the dietary protein to energy ratio is unbalanced, and evaluating feed efficiency of lactating sows by correcting for body mobilization seems to be a promising approach to improve sow feeding in the future.

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The objectives of the study were 1) to quantify dietary N utilized for milk N and N loss in urine and feces, in sows fed increasing dietary CP with a constant amount of Lys, Met, Thr, and Trp to meet their standardized ileal digestible (SID) requirement and 2) to determine the optimal dietary CP concentration based on dietary N utilization for milk production. Seventy-two sows were fed 1 of 6 dietary treatments, formulated to increase the SID CP as followed: 11.8, 12.8, 13.4, 14.0, 14.7, and 15.6% and formulated to be isocaloric (9.8 MJ NE/kg). Diets were fed from day 2 after parturition until weaning at day 28 (± 3 d). Litters were equalized to 14 piglets and weighed within 48 h following parturition. Sows were weighed and back fat scanned, at day 18 (± 3 d) and day 28 (weaning; ± 3 d). Litter weight was recorded at day 11, 18 (± 3 d), and 28 (± 3 d). Nitrogen balances were conducted on approximately day 4, 11, and 18 (± 3 d). Daily milk yield was estimated from recorded litter gain and litter size. To calculate sows mobilization of fat and protein, body pools of fat and protein were estimated by D2O (deuterated water) enrichment on day 4 and 18 (± 3 d). No linear, quadratic, or cubic effects of increasing dietary CP was observed for sows total feed intake, sow BW, body pools of protein and fat, protein and fat mobilization, total milk yield, and piglet performance. The protein content in milk increased linearly with increasing dietary CP in week 1 (P < 0.05), week 2 (P < 0.05), and week 3 (P < 0.001). Urine production did not differ among treatments and N output in urine increased linearly with increasing dietary CP concentration in week 1 (P = 0.05), week 2 (P < 0.001), and week 3 (P < 0.001). Urine N excretion relative to N intake increased linearly with increasing dietary CP (P < 0.001). Milk N utilization relative to N intake decreased linearly from 77.8% to 63.1% from treatment 1 through 6 (P < 0.001). Corrected milk N utilization decreased from 68.6% to 64.2% from treatment 1 through 6 (P < 0.05). In conclusion, a low dietary CP concentration for lactating sows with supplemented crystalline AA improved the efficiency of dietary N utilization and reduced the N output in urine without affecting lactation performance.

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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 &lt; 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 &lt; 0.01), lower colostrum yield (P &lt; 0.01), and higher frequency of piglet diarrhea (P &lt; 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.

The objective of the current study was to investigate the effect of supplementing a mono-component xylanase to a coarsely ground lactation diet (feed fraction particle size above 2 mm was more than 17%) based on wheat, barley, and soybean meal on nutrient digestibility and performance of lactating sows. A total of 30 cross-bred (Danish Landrace × Yorkshire) multiparous sows (parity 2 to 5) were used. Sows were fed a standard gestation diet from mating until day 108 of gestation, and then stratified for BW (295.4 ± 26.1 kg average BW) and parity to receive one of two dietary treatments (n = 15 per treatment), a lactation diet without (control diet) or with supplemented enzyme (enzyme diet). The enzyme applied was a mono-component xylanase dosed at 200 enzyme unit (FXU) per kg of feed, which corresponds to 200 g per ton of feed. The diets were fed until weaning at day 28 of lactation. On day 2 of lactation, litter size of each sow was adjusted to 14 piglets within treatment. Reproductive performance of the sows, growth of the piglets, yield and composition of sow milk, plasma metabolites and apparent total tract digestibility (ATTD) of nutrients were measured. Supplementation of xylanase had no effect (P > 0.05) on total born and live born piglets or stillbirth rate (%) at parturition. Initial parameters on day 2 of lactation including sow BW and back fat thickness, litter size, piglet weight, and litter weight were similar (P > 0.05) between treatments. Piglet weight gain, litter weight gain, litter size, and daily milk yield did not differ (P > 0.05) between treatments. The ADFI was increased by 4.5% (P < 0.01), and BW loss during the whole lactation was reduced from -13.6 to -5.2 kg (P = 0.04) with xylanase addition when compared to control sows. The ATTD of GE (83.9 vs. 82.9, P < 0.01), DM (84.2 vs. 83.4, P < 0.01), N (83.4 vs. 81.7, P = 0.02), OM (86.5 vs. 85.7, P < 0.01) and total nonstarch polysaccharides (NSP; 59.4 vs. 56.7, P = 0.02) were all increased by xylanase supplementation. Milk composition and plasma metabolites were not affected (P > 0.05), except that plasma triglycerides content was increased by xylanase addition (0.23 vs. 0.20 mM, P = 0.04). In conclusion, supplementing a mono-component xylanase to a coarsely ground lactating diet based on wheat, barley, and soybean meal improved sow feed intake and nutrient digestibility, thereby reducing sow BW loss throughout lactation, whereas milk yield and piglet performance were not affected.

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