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Primiparous sows (n = 50) were used to evaluate the impacts of increasing standardized ileal digestible (SID) Lys-to-net energy (NE) ratios on sow performance and nitrogen utilization during a 24-d lactation period. Sows were assigned to one of five diets with equally spaced and increasing SID Lys-to-NE ratios between 2.85 and 5.51 g SID Lys/ Mcal NE. Desired ratios were achieved by blending the two extreme diets in varying proportions using a feeding system with feed blending capabilities and were provided to sows immediately after farrowing until weaning (d 24 ± 0.3). Litters were standardized to 13 ± 1 piglets within 24 h after birth and were not provided creep feed. Nitrogen balances were conducted between d 4 and 7 (NB1), 12 and 15 (NB2), and 20 and 23 (NB3) of lactation, with total urine collection and fecal grab sampling. Contrast statements were used to assess linear and quadratic effects of increasing the SID Lysto- NE ratio. Linear (LBL) and quadratic broken-line and polynomial quadratic models were used to determine the optimum dietary Lys-to-NE ratios for maternal nitrogen retention. The Bayesian information criterion was used to assess best fit. Sow body weight (BW) and backfat depth losses over lactation decreased with increasing dietary SID Lys-to-NE ratio (linear; -19.0 to -5.9 ± 3.7 kg, P = 0.001 and -3.9 to -2.0 ± 0.7 mm, P = 0.003, respectively). No differences were observed for milk nitrogen output (69.3 ± 4.5, 74.2 ± 6.6, 85.6 ± 6.8 g/day for NB1, NB2, and NB3, respectively), overall piglet average daily gain (219 ± 10 g), and piglet BW at weaning (6.33 ± 0.24 kg). Sow average daily feed intake was not influenced by SID Lys-to-NE ratio (5.3 ± 0.2 kg/day) but sow nitrogen intake (linear; P < 0.001) and total nitrogen excretion (urine + feces; linear; P < 0.001) increased with dietary SID Lys-to-NE ratio in all NB periods. Nitrogen retention (linear; P < 0.001) and maternal nitrogen retention (nitrogen intake – nitrogen excretion – milk nitrogen output; P < 0.05) increased with dietary SID Lys-to-NE ratio in all NB periods (-22.8 to -2.7 ± 6.7, 3.6 to 36.3 ± 8.4, and 9.0 to 34.8 ± 6.8 g/d for maternal nitrogen retention in NB1, NB2, and NB3, respectively). The LBL model showed that maternal nitrogen retention was optimized beyond the SID Lys-to-NE ratio limits in NB1 but breakpoints were observed for maternal nitrogen retention at 4.74 and 4.85 g SID Lys/Mcal NE in NB2 and NB3, respectively. Therefore, optimizing the SID Lys-to-NE ratio during specific weeks of lactation could minimize maternal nitrogen losses of primiparous sows. [ABSTRACT FROM AUTHOR]

Eighty-eight gilts [initial body weight (BW) 49.8 ± 0.8 kg] were recruited to determine the effects of moderate energy and protein restriction during the development period on changes in BW and backfat depth (BF) and subsequent lactation performance. Gilts were randomly assigned to one of four feeding programs: 1) standard commercial diet fed ad libitum (CON), 2) standard commercial diet fed 10% or 3) 20% below ad libitum, or 4) a high–fiber diet fed ad libitum [2.5 times more fiber (neutral detergent fiber) than the commercial diet to dilute net energy and crude protein by approximately 20% and 13%, respectively; FIB ]. The gilts were housed individually and received the feeding programs between 90 and 190 (breeding) d of age and standard gestation and lactation diets thereafter. Litters were standardized to 12 ± 1 pigs within 48 h of farrowing; weaning occurred at 20.0 ± 0.4 d of age. Gilts that received the 20% restricted program had lower overall average daily feed intake (ADFI) during the development period (2.64 ± 0.04 kg; P < 0.05) versus all other feeding programs and gilts that received the 10% restricted program had lower ADFI than FIB and CON, which were not different (2.96 vs. 3.44 and 3.47 ± 0.04 kg for 10%, FIB and CON, respectively; P < 0.05). Plasma free fatty acid (FFA) concentrations on day 180 of age were lower for gilts that received the 10% and 20% restricted programs compared to gilts that received the FIB and CON programs, which were not different (97 and 86 vs. 220 and 149 ± 29 µEq/L, respectively; P < 0.05). Plasma concentrations of glucose, urea, prolactin, and IGF-1 were not different among feeding programs on day 180 of age. At breeding, gilts that received the FIB and 10% programs had lower BW and BF versus CON (145.7 and 144.8 vs. 155.2 ± 0.9 kg and 14.4 and 14.8 vs. 16.5 ± 0.2 mm for BW and BF, respectively; P < 0.05) but greater BW than gilts that received the 20% restricted program (137.9 kg; P < 0.05). The BW and BF of gilts did not differ at the end of gestation or at weaning. The ADFI of sows during lactation and offspring birth weight and growth rate during lactation and the 5-wk nursery period were not influenced by gilt development feeding program. Therefore, a high-fiber feeding program could be used in group-housing gilt-development scenarios, where feed is offered ad libitum, to control BW and BF prior to breeding without influencing milk production in the subsequent lactation period. [ABSTRACT FROM AUTHOR]

Fifty of each primiparous and multiparous sows were used to evaluate a blending feeding program using gestation and lactation diets during the transition period on sow back fat depth (BF), blood metabolites, and litter growth performance. Sows were randomly assigned to one of two feeding programs in a 2×2 factorial design (n = 25) from 104 ± 1 days of gestation: 1) a unique daily blend of standard gestation [0.58% standardized ileal digestible (SID) lysine and 2419kcal/kg NE] and lactation diets (0.95% SID lysine and 2507kcal/kg NE) until day 5 after farrowing to meet estimated daily SID lysine and net energy requirements (NRC, 2012; TRAN) or 2) approximately 2 kg per day of a standard lactation diet until farrowing (CON). Upon farrowing, sows on the CON feeding program received step-up access to the lactation diet according to a feeding curve. Five days after farrowing, both groups received ad libitum access to the lactation diet until weaning (20.0 ± 0.3 days). Sow body weight (BW) and BFwere measured on day 104 and 110 of gestation (BW only), after farrowing, and at weaning. Fasted blood samples were collected from sows at farrowing and weaning. Litters were standardized to 13 ± 1 piglets and were not provided creep feed. During gestation, TRAN sows consumed more feed than CON sows, which was especially evident for multiparous sows (2.95 vs. 2.13 ± 0.08kg/d for TRAN vs. CON; interaction and main effect; P < 0.05). During lactation, average daily feed intake was not influenced by feeding program but was greater for multi versus primiparous sows (5.98 vs. 4.20 ± 0.30kg; P < 0.001). At all time points, BW was greater for multi versus primiparous sows, regardless of feeding program (P < 0.05). During the gestation period, TRAN sows tended to have greater average daily gain (1.43 vs. 1.00±0.39kg/d; P=0.061) and had less back fat loss (-0.18 vs. -0.92 ± 0.37mm; P < 0.05) versus CON sows, regardless of parity. Only after farrowing, TRAN sows had greater BW and BF than CON sows, regardless of parity (221.5 vs. 215.5 ± 4.1kg and 17.0 vs. 16.3 ± 0.4mm; P < 0.05), but at weaning there were no feeding program-related differences in BW or BF. No feeding program-related differences were observed for litter characteristics, but litter birth weight and piglet BW at weaning were greater for multi versus primiparous sows (P< 0.01). Only after farrowing, serum BHBA (11.9 vs. 19.4 ± 7.8mmol/L) and NEFA (0.34 vs. 0.56 ± 0.10mmol/L) concentrations were less and serum glucose concentrations (4.4 vs. 3.9 ± 0.2mmol/L) were greater for TRAN versus CON sows (P < 0.05), regardless of parity. Therefore, a simple transition feeding program using standard gestation and lactation diets reduced energy mobilization by multi and primiparous sows in late gestation, with no impact on subsequent lactation performance. [ABSTRACT FROM AUTHOR]