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.

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.

Three experiments were conducted to test the hypothesis that supplementing nursery pig diets with a mixture of carbohydrases (CS) will improve pig performance and nutrient digestibility. The CS used in these experiments contained 7 units/g of alpha-1,6-galactosidase, 22 units/g of beta-1,4-mannanase, beta-1,4 mannosidase, and trace amounts of other enzymes. In Exp. 1, 108 pigs weaned at d 21 of age were fed one of three diets containing 0 (control), 0.1, or 0.2% CS for 5 wk, based on a three-phase feeding program (1, 2, and 2 wk). Over the entire 35-d period, ADG was not affected (P > 0.05) by treatment, but supplementing 0.1% CS increased (P < 0.05) gain:feed by 9%. Experiment 2 used 10 gilts fitted with simple T-cannula in the terminal ileum at 3 wk of age. After cannulation, pigs were fed the same control Phase I and II diets, but the Phase III diet contained either 0 or 0.1% CS. Ileal samples were collected for the 3 d following the 5-d adjustment period during Phase III. Apparent ileal digestibility of GE, lysine, threonine, and tryptophan was greater (P < 0.05) in the CS diet. In Exp. 3, 90 pigs weaned at 21 d of age were fed the same control Phase I and II diets, but the Phase III diet contained either 0 or 0.1% CS. Phase III diets were fed for 3 wk. Average daily gain of the CS group was greater (P < 0.05) than the control group during wk 3. Gain:feed ratio was greater (P < 0.05) for the carbohydrase group during the entire Phase III period. Four pigs per treatment were killed at the end of Exp. 3 to measure villus height and to determine the concentration of raffinose and stachyose in different parts of the gastrointestinal tract. Average villus height was greater (P < 0.05) in pigs fed the CS diet. Carbohydrase supplementation decreased (P < 0.05) the concentration of stachyose in freeze-dried digesta from the proximal and distal small intestine. Raffinose concentration, on the other hand, was decreased (P < 0.05) by CS supplementation only in the distal small intestine. These lower concentrations suggest that CS improved the digestibility of carbohydrate in soybean meal. In conclusion, the addition of CS to Phase I and Phase II nursery diets containing low levels of soybean meal did not improve pig performance, but its addition to corn-soybean meal-based Phase III nursery diets improved gain:feed ratio and energy and AA digestibility.

The objectives of this study were to characterize the quantitative changes in various body tissues of high-lean type gilts during gestation and to determine the protein needs of pregnant gilts based on changes in tissue contents. Thirty-five gilts (158.2 +/- 8.3 kg) were housed in individual gestation crates with six unbred gilts randomly selected and slaughtered to provide data for d 0 of gestation. The remaining gilts were bred and assigned randomly to one of six slaughter groups: d 45, 60, 75, 90, 102, and 112. Gilts were fed 2 kg (as-fed basis) of gestation diet daily (3.1 Mcal/kg of ME and 0.56% lysine). Carcass soft tissue, bone, gastrointestinal tract, spleen, pancreas, kidney, liver, uterus, fetus, mammary gland, and the remaining viscera were separated and weighed. Carcass soft tissue, liver, remaining viscera, uterus, and gastrointestinal tract were ground, freeze-dried, and analyzed for composition. Body weights of the gilts increased quadratically (P < 0.001) during gestation. Weights of carcass soft tissue and uterus, including placenta, increased linearly (P < 0.001) during gestation. Weights of individual fetuses, fetal litters, individual mammary glands, and the entire mammary glands increased cubically (P < 0.001) during gestation. Crude protein in carcass soft tissue increased cubically (P < 0.01), whereas DM and ether extract (EE) in carcass soft tissue increased linearly (P < 0.01). The DM, CP, and EE in the entire mammary glands increased quadratically (P < 0.001) during gestation. The DM, CP, and EE in fetal litter increased cubically (P < 0.01) as gestation progressed. The accretion rates of the conceptus, fetal litter, individual fetus, individual mammary gland, and CP in fetal litter differed (P < 0.05) before and after d 70 of gestation. The CP daily gain from all maternal and fetal tissues was 40 and 103 g/d before and after d 70 of gestation, respectively, suggesting that pregnant gilts may require different quantities of dietary protein during gestation. Based on the maintenance requirement, maternal tissue gain, and conceptus gain, pregnant gilts require 6.8 and 15.3 g/d of true ileal-digestible lysine (or 147 and 330 g/d of true ileal-digestible protein) before and after d 70 of gestation, respectively, to support their true biological needs.

Widespread use of soyabean meal in pig diets brings forth issues dealing with soyabean antinutritional compounds, especially those that are heat-stable following processing into soyabean meals. Microbial enzyme supplements have been used in an attempt to eliminate these antinutritional compounds, which include phytate and flatulence-producing carbohydrates. The benefits of using phytase in pig diets are well-documented and been reviewed, whereas the information on supplemental enzymes targeting flatulence-producing compounds is rather limited. Eighteen papers and abstracts are reviewed here. Use of these enzymes successfully reduced flatulence-producing compounds in soyabean meals and improved nutrient digestibility as well as growth of pigs even though these effects were not consistent. The inconsistency may reside in the fact that the origin and type of enzymes used for each study were different. Use of enzyme supplements for flatulence-producing compounds in soyabean meal could be beneficial to the industry if the origin and type of enzymes could be better defined.