Three hundred twenty fetuses were obtained from 33 pregnant gilts (Camborough-22, Pig Improvement Co.) to determine rates of nutrient deposition in fetal tissues and to estimate nutrient requirements for fetal growth. Pregnant gilts were fed an equal amount of a gestation diet (2.0 kg/d; as-fed basis), and were slaughtered at d 0, 45, 60, 75, 90, 102, or 110 of gestation (n = 3 to 6 per day). Fetuses were dissected into carcass and individual tissues (including gastrointestinal tract, liver, lung, heart, kidney, spleen [> or = d 75]), and partial placental collection was made for chemical analysis. Fetal tissues were weighed and analyzed for DM, ash, CP, and crude fat. Regression equations were obtained to explain the weight and compositional changes of individual tissues during gestation. Weights of the fetus, carcass, gastrointestinal tract, liver, heart, lung, and kidney increased cubically (P < 0.001), whereas brain weight increased linearly (P < 0.001) as gestation progressed. Fetal protein and fat contents increased quadratically (P < 0.001) as gestation progressed (R2 = 0.906 and 0.904, respectively). Changes in fetal protein and fat contents fit a multiphasic regression that consisted of two linear equations (P < 0.001, R2 = 0.988 and P < 0.001, R2 = 0.983, respectively), indicating that protein and fat growth accelerated after d 69 of gestation. Fetal protein and fat accretions were 0.25 and 0.06 g/d (P < 0.001) before d 69 of gestation, and increased to 4.63 and 1.09 g/d (P < 0.001) after d 69 of gestation. Protein needs for tissue protein gains increased 19-fold after d 69 of gestation. Results of this study indicate that the growth of the fetus and fetal tissues occurs at different rates during gestation and support the practice of a two-phase feeding strategy (before and after approximately d 70 of gestation) for pregnant gilts.

Improving efficiency of protein utilization is important for pregnant sows under restricted feed allowance and for lactating sows with limited feed intake. Sows have limited ability to support the growth of fetuses and mammary glands during late gestation and to support mammary growth and milk production, especially during first lactation period. A series of studies was conducted to characterize requirements and ideal ratios of AA for 1) fetal growth, 2) mammary gland growth of gestating sows, 3) maternal tissue gain of gestating sows, 4) mammary gland growth of lactating sows, and 5) maternal tissue gain of lactating sows. A total of 97 pregnant sows and their fetuses and a total of 174 lactating sows and their nursing piglets were used for these studies to collect fetal tissues, mammary tissues, and maternal tissues for AA analysis. Requirements and ideal ratios of AA for sows changed dynamically depending on stages of pregnancy. Suggested daily requirements for true ileal digestible Lys were 5.57 and 8.78 g, and relative ideal ratios for Lys:Thr:Val:Leu (on basis of AA weight) were 100:79:65:88 and 100:71:66:95 for d 0 to 60 and d 60 to 114 of gestation, respectively. Requirements and ideal ratios of AA for lactating sows changed dynamically depending on potential amounts of protein mobilization from maternal tissues, which are related to voluntary feed intake and milk production. Suggested ideal ratios for Lys:Thr:Val:Leu were 100:59:77:115 and 100:69:78:123 if BW losses of sows during 21 d of lactation are 0 and 33 to 45 kg, respectively. To optimize efficiency of dietary protein utilization by sows, the dietary AA content and ratios can be adjusted by stages of pregnancy (i.e., phase feeding) and by expected feed intakes or parities of sows during lactation (i.e., parity-split feeding) considering the dynamic changes in the requirements and ideal ratios of AA.

Four experiments were conducted using 671 nursery pigs to evaluate fermented soybean meal (FSBM) as a new vegetable protein source for nursery pigs. In Exp. 1, a total of 192 pigs weaned at 19.2 +/- 0.3 d of age were fed 3 diets (8 pens per treatment) for 2 wk: a control diet (without FSBM) and 2 diets with 3 and 6% FSBM replacing soybean meal, followed by a common diet for the next 2 wk. In Exp. 2, a total of 160 pigs weaned at 21.6 +/- 0.2 d of age were fed 4 diets (5 pens per treatment) for 2 wk: a control diet (without FSBM but with 25% dried skim milk; DSM) and 3 diets with 3, 6, and 9% FSBM replacing DSM based on CP. Concentrations of CP, Lys, Met, Thr, and Trp were kept consistent among diets in Exp. 1 and 2. In Exp. 3, a total of 144 pigs weaned at 22.1 +/- 0.2 d of age were fed 3 diets (6 pens per treatment) for 2 wk: a control diet (without FSBM but with 40% DSM) and 2 diets with 5 and 10% FSBM replacing DSM based on CP. Concentrations of CP, Lys, Met, Thr, Trp, and lactose were kept consistent among diets. In Exp. 4, a total of 175 pigs weaned at 20.7 +/- 0.4 d of age were fed 5 diets (5 pens per treatment) for 3 wk: a basal diet [15.5% CP without plasma protein (PP) and FSBM], 2 diets (18.4% CP) with 3.7% PP or 4.9% FSBM, and 2 diets (21.2% CP) with 7.3% PP or 9.8% FSBM. Concentrations of Lys, Met, Thr, and Trp were kept consistent among diets with the same CP concentrations. Pigs had access to feed and water ad libitum and their BW and feed intake were measured weekly for all experiments. Use of up to 6% FSBM replacing soybean meal improved (P < 0.05) G:F and diarrhea scores of nursery pigs (Exp. 1). Use of up to 9% FSBM replacing DSM reduced (P < 0.05) ADG and G:F (Exp. 2). When lactose concentrations were equal, FSBM could replace up to 10% DSM without adverse effects on ADG and G:F (Exp. 3). Relative bioavailability of protein in FSBM to PP was 99.1% (Exp. 4). Collectively, FSBM can serve as an alternative protein source for nursery pigs at 3 to 7 wk of age, possibly replacing the use of DSM and PP but excluding the first week postweaning for PP when balancing for AA and lactose.

The objectives of this experiment were 1) to determine the NE of soybean oil (SBO) and choice white grease (CWG) fed to growing and finishing pigs, 2) to evaluate the effects of inclusion rate of SBO on the NE by growing and finishing pigs, and 3) to determine if there is a difference in the NE of SBO and CWG between growing and finishing pigs. Forty-eight growing (initial BW: 22.13 ± 1.78 kg) and 48 finishing (initial BW: 84.17 ± 5.80 kg) barrows were used, and they were housed and fed individually. Within each stage of growth, pigs were allotted to 8 outcome groups of 6 barrows based on BW. Within each outcome group, pigs were randomly allotted to 1 of 6 groups. Two groups at each stage of growth served as an initial slaughter group. Pigs in the remaining groups were assigned to 4 dietary treatments and slaughtered at the conclusion of the experiment. The basal diet contained corn, soybean meal, and no supplemental lipids. Three additional diets were formulated by mixing 95% of the basal diet and 5% SBO, 90% of the basal diet and 10% SBO, or 90% of the basal diet and 10% CWG. Average daily gain and G:F for finishing pigs and apparent total tract digestibility of energy for growing and finishing pigs increased (linear, P < 0.05) with lipid content, but was not affected by lipid source. The lipid gain:protein gain ratio and the energy retention also increased (linear, P ≤ 0.05) with lipid content in growing and finishing pigs. There were no interactive effects between lipid content and stage of growth or between lipid source and stage of growth on the NE of diets and the NE of dietary lipids. The NE of diets increased (linear, P < 0.01) with increasing SBO (2,056, 2,206, and 2,318 kcal/kg for diets containing 0, 5, or 10% SBO). The NE of the diet containing 10% CWG (2,440 kcal/kg) was greater (P < 0.05) than the NE of the diet containing 10% SBO. The NE of diets was greater (P < 0.05) for finishing pigs than for growing pigs regardless of lipid content or source. The NE of SBO included at 5% (5,073 kcal/kg) was not different from the NE of SBO included at 10% (4,679 kcal/kg), but the NE of CWG (5,900 kcal/kg) was greater (P < 0.05) than the NE of SBO. The stage of growth had no impact on the NE of SBO or CWG. In conclusion, the NE of lipids is not affected by the content of dietary lipids, but the NE of CWG is greater than the NE of SBO.

The purpose of this study was to quantify mammary gland (MG) growth during pregnancy in gilts and to determine the effect of anatomical location on gland growth. Size, composition, and histomorphology of MG were determined during gestation in 29 primigravid gilts. Gilts were allotted randomly to 6 slaughter groups: d 45 (n = 6), 60 (n = 4), 75 (n = 5), 90 (n = 4), 102 (n = 5), and 112 (n = 5) of gestation. Mammary glands were obtained at slaughter, and skin and extraneous fat pad were removed to obtain parenchymal MG tissue. Mammary glands were further separated into individual MG, and their locations were recorded. Individual MG were weighed and bisected in an approximate midsagittal section to measure cross-sectional area. Mammary glands were ground individually and pooled according to anatomical region: the first and second pairs of MG = anterior MG; the third, fourth, and fifth pairs of MG = middle MG; the sixth, seventh, and eighth pairs of MG = posterior MG. Contents of DM, CP, ether extract, and crude ash were measured. Wet weight, DM, CP, and ash content of total and individual MG increased (P < 0.01) between d 45 and 112 of gestation. Cross-sectional area of individual MG increased (P < 0.01) as gestation progressed. Percentage of CP and ash increased (P < 0.01), whereas percentage of ether extract decreased (P < 0.01) as gestation progressed. This inverse relationship between percentages of CP and ether extract (r = -0.999; P < 0.0001) was consistent with the histological shift from primarily an adipose tissue in early gestation to one containing extensive lobuloalveolar tissue in late gestation. Wet weight of middle MG was greater (P < 0.05) than that of posterior MG at d 102 and 112 of gestation, and amount of CP in middle MG was greater (P < 0.05) than that in anterior and posterior MG at d 102 and 112 of gestation, indicating that middle MG grow faster than other MG during late gestation. Rates of wet weight gain and protein accretion were accelerated (P < 0.01) after d 74 and 75 of gestation, respectively, indicating the importance of MG growth during the last trimester of gestation. The increase in rate of protein accretion after d 75 indicates a greater protein requirement for MG growth during later gestation.