Performance of lactating dairy cows fed corn as whole plant silage and grain produced from genetically modified corn containing event DAS-59122-7 compared to a nontransgenic, near-isogenic control.

The nutritional equivalency of grain plus whole plant silage from genetically modified corn plants containing the DAS-59122-7 (59122) event expressing the Cry34Ab1 and Cry35Ab1 proteins to grain and silage from a near-isogenic corn hybrid without this trait (control) was assessed using lactating dairy cows. Corn plants with event 59122 are resistant to western corn rootworm and tolerant to the herbicide active ingredient glufosinate-ammonium. Effects on feed intake, milk production, and milk composition were determined. The 59122 grain and the control grain were produced in 2005 from isolated plots in Richland, Iowa. Whole plant corn silage for the 59122 and control treatments were grown in isolated plots at the Kansas State University Dairy Center and ensiled in Ag-Bags. Thirty lactating Holstein cows blocked by lactation number, day of lactation, and previous energy-corrected milk production were used in a switchback design. All cows were fed diets that contained 22.7% grain plus 21.3% whole plant silage from either the 59122 or the control hybrid, in addition to 21% wet corn gluten feed, 12.3% protein mix, 8.0% whole cottonseed, and 14.7% alfalfa hay. Each period of the switchback trial included 2 wk for diet adjustment followed by 4 wk for data and sample collection. Milk samples (a.m. and p.m.) collected from 2 consecutive milkings of each collection wk were analyzed for fat, protein, lactose, solids-not-fat, milk urea nitrogen, and somatic cell count. Percentages of milk fat, protein, lactose, and solids-not-fat were not affected by dietary treatment. Yields of milk, 4% fat-corrected milk, energy-corrected milk, solids-corrected milk, and the concentrations and yields of milk fat, milk protein, milk solids, and milk lactose were not significantly different between treatments. Efficiencies of milk, fat-corrected milk, energy-corrected milk, and solids-corrected milk production also were not different when cows were fed crops from 59122 than when they were fed the control hybrid. Milk production efficiency averaged 1.48 and 1.50 kg/kg of dry matter intake for cows fed diets containing the control and 59122 corn, respectively. These data indicate that the nutritional value for milk production was not different between a diet containing grain plus whole plant corn silage produced from a 59122 corn hybrid versus a diet containing grain and corn silage from its near-isogenic control corn hybrid.

Effect of the form of dietary fat and the concentration of dietary neutral detergent fiber on ileal and total tract endogenous losses and apparent and true digestibility of fat by growing pigs.

An experiment was conducted to determine the effect of the form of dietary fat (extracted or intact fat) and of dietary NDF on ileal and total tract endogenous losses of fat (ELF), on apparent ileal (AID) and apparent total tract digestibility (ATTD) of fat, and on true ileal (TID) and true total tract digestibility (TTTD) of fat in growing pigs. A cornstarch-based basal diet that contained 1.27% fat was prepared and 3 diets were formulated by adding 2.0, 4.0, or 6.0% extracted fat (corn oil) to the basal diet at the expense of cornstarch. Three additional diets were formulated by adding 3.1, 6.2, or 9.3% Solka-Floc (International Fiber Corp., North Tonawanda, NY) to the diet containing 4.0% corn oil at the expense of cornstarch. The remaining 4 diets were prepared by adding whole corn germ meal to the diet at the expense of defatted corn germ meal to contain 3.0, 6.0, or 9.0% intact fat. Solka-Floc was also included in this diet at the expense of cornstarch in an attempt to keep NDF constant. Eleven barrows (initial average BW of 38.1 +/- 1.3 kg) were fitted with a T-cannula in the distal ileum, allotted to the 11 diets in an 11 x 11 Latin square design, and fed the diets at 3 times the energy requirement for maintenance. Increasing dietary extracted fat increased (linear and quadratic, P < 0.001) the AID and ATTD of fat. Increasing dietary intact fat also increased (linear and quadratic, P < 0.05) the AID and ATTD of fat. The average apparent digestibility of extracted fat (81.9%) was greater (P < 0.001) than that of intact fat (63.2%). Estimates of ELF were smaller (P < 0.05) for extracted fat than for intact fat at the end of the ileum and over the entire intestinal tract, but the TID (93.8%) and TTTD (94.2%) of extracted fat were greater (P < 0.05) than the TID (78.6%) and TTTD (84.1%) of intact fat. Increasing dietary extracted fat had no effects on the TID and TTTD of fat, but increasing dietary intact fat resulted in a quadratic reduction (P < 0.05) in the TTTD of fat. Increasing dietary NDF had a quadratic effect (P < 0.05) on the ATTD of fat but did not influence the AID, TID, and TTTD of fat. In conclusion, extracted fat induces a smaller amount of ELF and has a greater apparent and true digestibility than intact fat at the end of the ileum and over the entire intestinal tract. Purified NDF has little influence on apparent and true digestibility of fat.

Evaluation of corn grain with the genetically modified input trait DAS-59122-7 fed to growing-finishing pigs.

A growth performance experiment was conducted to assess the feeding value of a double-stacked transgenic corn grain for growing-finishing pigs. The genetically modified corn grain contained event DAS-59122-7, which expresses the Cry34/35Ab1 binary insecticidal protein for the control of corn rootworm. This modified transgenic grain is resistant to western corn rootworm and is also tolerant to herbicides containing the active ingredient glufosinate-ammonium. The modified grain (59122), a nontransgenic near-isoline grain (control corn), and a commercial corn (Pioneer brand hybrid 35P12) were grown in a 2005 production trial in individually isolated plots that were located 201 m apart. A total of 108 pigs were allotted to corn-soybean meal diets containing 1 of the 3 grains as the sole source of corn. There were 3 pigs per pen and 12 replicate pens per treatment. Pigs were fed grower diets from 37 to 60 kg, early finisher diets from 60 to 90 kg, and late finisher diets from 90 to 127 kg. Within each phase, data for ADG, ADFI, and G:F were calculated. At the conclusion of the experiment, pigs were slaughtered and data for carcass quality were collected. Differences between 59122 and the control corn were evaluated, with statistical significance at P<0.05. No differences in ADG, ADFI, or G:F between pigs fed the control corn and pigs fed the modified corn were observed during the grower, early finisher, or late finisher phases. For the entire experimental period, no difference between pigs fed the control and the 59122 corn were observed for final BW (128.9 vs. 127.1 kg), ADG (1.02 vs. 1.00 kg), ADFI (2.88 vs. 2.80 kg), or G:F (0.356 vs. 0.345 kg/kg). Likewise, no differences in dressing percentage (76.48 vs. 76.30%), LM area (49.8 vs. 50.4 cm(2)), 10th-rib back fat (2.20 vs. 2.12 cm), and carcass lean content (52.9 vs. 53.4%) were observed between pigs fed the control and the 59122 corn grain. It was concluded that the nutritional value of the modified transgenic corn grain containing event DAS-59122-7 was similar to that of the nontransgenic near-isoline control.

The influence of diets containing either conventional corn, conventional corn with choice white grease, high oil corn, or high oil high oleic corn on belly/bacon quality.

The objectives of this study were to evaluate diets possessing different fatty acid profiles (as influenced by corn type) with regard to fatty acid profile and firmness of pork bellies. Crossbred barrows (n=196) were fed one of four corn-based diets consisting of conventional corn (CONV), CONV with choice white grease (CWG), high oil corn (HOC), or high oleic, high oil corn (HOHOC). Following 98 days on test, two animals representing the average pen weight (118 kg) were selected for harvest (n=56). A 50-g fat sample was removed from each belly for fatty acid profile analysis. Lateral and vertical flex tests were performed to determine belly firmness. Bellies were pumped and cooked according to a commercial protocol. Total saturated fatty acids increased (P<0.001) and total unsaturated fatty acids decreased (P<0.05) when CWG was added to the CONV diet or when HOC or HOHOC were substituted for CONV corn. Pigs fed CONV corn had firmer bellies, while those fed HOC were softer. No differences were observed across treatment for percentage pump retention, smokehouse yield, or slicing yield (P>0.05). Based on the results of this study, corn type influences fatty acid profile, and belly firmness, but does not affect pump retention, or slicing yields.

Phosphorus bioavailability, growth performance, and nutrient balance in pigs fed high available phosphorus corn and phytase.

Three experiments were conducted to evaluate P bioavailability, growth performance, and nutrient balance in pigs fed high available P (HAP) corn with or without phytase. The bioavailability of P in normal and HAP corn relative to monosodiumphosphate (MSP) for pigs was assessed in Exp. 1. In a randomized complete block design, 96 pigs (average initial BW 9.75 kg) were fed eight diets for 28 d. The reference and test diets were formulated by adding P as MSP, HAP, or normal corn at 0, 0.75, or 1.5 g/kg to a corn-starch-soybean meal basal diet (2.5 g/kg P) at the expense of cornstarch. Plasma inorganic P concentration responded linearly (P < 0.05) to supplemental P intake. Estimates of P bioavailability from HAP andnormal corn when plasma P was regressed on supplemental P intake were 46 and 33%, respectively. In Exp. 2 and 3, pigs were fed corn-soybean meal-based diets containing HAP corn or normal corn and 0 or 600 units of phytase per kilogram in a 2 x 2 factorial arrangement (two corn sources and two levels of phytase). In Exp. 2, 48 crossbred pigs (barrow:gilt, 1:1) averaging 9.25 kg were used to evaluate growth performance. There were no detectable interactions between corn source and phytase for any of the performance criteria measured. Pigs receiving normal corn had the lowest (P < 0.05) BW and rate of gain. Feed efficiency was lower (P < 0.05) in pigs fed normal compared with those fed the HAP corn phytase-supplemented diet. In Exp. 3, 24 crossbred barrows averaging 14.0 kg were used to evaluate nutrient digestibility. There were no detectable interactions between corn and phytase for any of the N and Ca balance criteria. Nitrogen and Ca retention were improved in pigs receiving HAP corn with phytase (P < 0.05). Retention and digestibility of P was lowest (P < 0.01) for pigs on normal corn diet without phytase. The percentage of P digested and retained was improved and fecal P excretion lowered (P < 0.05) by feeding HAP corn. The results of this study indicate that the bioavailability and balance of P in HAP corn is superior to that of normal corn. The addition of 600 phytase units (Natuphos 600, BASF) to HAP corn-based diets further improved P digestibility and reduced P excretion in pigs.

Growing-finishing performance and carcass characteristics of pigs fed normal and genetically modified low-phytate corn.

A genetically modified corn hybrid homozygous for the lpa1 allele, containing low phytate (LP), and its nearly isogenic equivalent hybrid (normal) were compared in two experiments with growing-finishing swine. In Exp. 1, 210 barrows (27 kg) were allotted to one of six dietary treatments with two corn hybrids (LP and normal) and three P feeding regimens. There were five replicate pens (seven pigs/pen) per treatment. Treatments consisted of diets that were supplemented with P throughout the growing-finishing period (.2% P and .15% supplemental P during growing and finishing phases, respectively) or only during the growing phase (.2% supplemental P) or that were not supplemented with P throughout the growing-finishing period. Performance at the end of the growing phase was based on a 2 x 2 factorial arrangement of treatments with two corn hybrids and two levels of added P (0 and .2%). This resulted in 10 replicates for the treatments supplemented with .2% P. The finishing phase (73 to 112 kg) was a 2 x 3 factorial arrangement of treatments with the two types of corn and three regimens of added P during the finishing period. Breaking load (BL) and ash of the fourth metacarpal were evaluated from one pig/pen at the end of the growing phase and from all pigs after slaughter. Pigs fed the LP corn diet without added P had greater body weight gain, feed efficiency, BL, and ash content of the fourth metacarpal than pigs fed the normal corn diet without added P. Performance was similar between pigs fed the LP diet without added P and pigs fed LP and normal corn with added P. In Exp. 2, 1,092 gilts (34 kg body weight) were allotted by weight in a commercial facility to one of three treatments: 1) normal corn/soybean meal diet containing .29% and .22% available P during the growing and finishing phases, respectively; 2) LP corn/soybean meal diet with the same available P level as Treatment 1; and 3) same as Treatment 2 for 8 wk, then no inorganic P supplementation during the finishing phase. All pigs were slaughtered at approximately 122 kg. There were no significant differences in growing-finishing performance or BL among treatments. However, pigs fed diets containing LP corn possessed carcasses with less backfat and a higher percentage of lean (P < .01). These results confirm that the P in LP corn is available to the pig and suggest that pigs fed diets containing this genetically modified corn will have more desirable carcasses.

Phosphorus bioavailability and digestibility of normal and genetically modified low-phytate corn for pigs.

We conducted two studies to determine the bioavailability and apparent digestibility of P in a low-phytate corn hybrid (.28% total P, .10% phytate P) genetically modified to be homozygous for the 1pa1-1 allele and a nearly isogenic corn hybrid (normal) (.25% total P, .20% phytate P). Additionally, we conducted an in vitro assay involving a peptic and pancreatin digestion to estimate P availability. The first study used 50 individually penned pigs (initial body weight 9 kg) and 10 treatments in a randomized complete block design. A cornstarch-soybean meal basal diet (.6% Ca, .2% P) was used. Treatments consisted of the basal diet and the basal diet plus .05, .10, or .15% P from monosodium phosphate (MSP), low-phytate corn, or normal corn. After a 35-d feeding period, pigs were killed to collect the fourth metacarpal for measurements of ash and breaking load. Breaking load was regressed on added P intake, and the bioavailability of P was determined by the slope ratio method. The bioavailabilities of P (relative to MSP) for low-phytate and normal corn were 62 and 9%, respectively. These were similar to the determined in vitro values of 57 and 11% for low-phytate and normal corn, respectively. In the second study, 20 pigs (initial BW 20 kg) were used in a randomized complete block design with a 2 x 2 factorial arrangement of treatments. Two corn lines (low-phytate and normal) and two levels of supplemental P (0 and .2%) from dicalcium phosphate were used. Diets with no added P were formulated to contain .9% lysine, .6% Ca, and .34% P. Apparent nutrient digestibilities were calculated from total collection of urine and feces for 5 d. There were no differences among treatments for energy and nitrogen digestibility. Pigs fed low-phytate corn with no added P had increased digestibility and retention of P and reduced total P excretion (P < .05). We conclude that low-phytate corn contains at least five times as much available P as normal corn. The use oflow-phytate corn greatly reduced the amount of P excreted by the pig and increased the N:P ratio in the manure.

Effect of level of chronic immune system activation on the lactational performance of sows.

The effect of the level of chronic immune system (IS) activation on sow lactational performance was determined in 11 pairs of littermate, primiparous sows. Sows with a low level of IS activation were created by rearing the animals via early weaning, isolated rearing schemes. During lactation, two levels of IS activation were achieved in each littermate sow pair by subcutaneous administration of either 0 (saline) or 5 microg/kg of sow BW of Escherichia coli lipopolysaccharide (LPS) in a mineral oil adjuvant emulsion on d 2 and 10 of lactation. Litters were standardized to 13 pigs by 8 h postpartum. Sows were offered daily 6.0 kg of a corn-soy diet formulated to contain a minimum of 250% of the dietary nutrient concentrations estimated to be needed by lactating sows. Based on antibody titers to LPS and serum concentrations of alpha-1 acid glycoprotein (AGP), high IS sows mounted an immune response to the LPS during lactation, and low IS sows maintained a low level of IS activation. Over an 18-d lactation, a high level of chronic activation of the sows' immune systems depressed daily sow feed intakes by .56 kg, litter weight gains by .32 kg, and daily milk by 1.4 kg, milk energy by 1.7 Mcal, and milk protein yields by 71 g, but did not alter sow body weight loss. The reductions in yields of milk and milk nutrients likely were because of proinflammatory cytokine-induced inhibition of the lactogenic hormones resulting from high chronic IS activation. Based on these data, the level of chronic IS activation alters the lactational performance of sows.

Effect of lean growth genotype and dietary amino acid regimen on the lactational performance of sows.

The effect of dietary amino acid regimen and genetic capacity for lean tissue growth on the lactational performance of sows was determined in primiparous sows with a high (350 to 390 g/d) or low (240 to 280 g/d) genetic capacity for lean tissue growth from 18 to 110 kg of body weight. During lactation, sows were offered daily 6.5 kg of one of four fortified corn-soybean meal diets containing .58, .77, .96, and 1.15% lysine (L). Litters were standardized to 14 pigs within 8 h after birth. On d 2 of lactation, the high lean growth (LG) sows possessed more proteinaceous tissues and protein and less fat tissue and lipid. During lactation (d 2 to 28 postpartum), high LG sows consumed more feed, mobilized more body protein, and lost less body lipid. Milk, milk energy, and milk lysine yields (pooled across dietary regimens) were similar between genotypes. As daily dietary lysine intakes increased from 27 to 62 g and total digestible lysine supplies (from diet and mobilized tissues) increased from 39 to 68 g, daily yields of milk, milk energy, and milk lysine increased, but the magnitude of the response differed (P < .05) between genotypes, evidently because of differences in the ability of the high and low LG sows to mobilize energy from body tissue. Based on these data, the lactational capacities of high and low LG sows nursing 12 to 14 pigs are similar when similar supplies of lysine and energy are available from dietary intake and mobilized body tissue stores. When supplies of ME do not limit milk synthesis, daily digestible lysine intakes of at least 54 g (> or = 66 g from a corn-soy diet) are needed by these sows nursing litters of 12 to 14 pigs to support milk synthesis and minimize maternal protein losses. This is equivalent to a total digestible lysine need of 4.3 to 4.6 g/kg of milk produced. When ME provided by the diet is less than that needed to fuel maximum milk synthesis, however, the dietary amino acid needs of genetically lean sows may be reduced because of their inability to mobilize sufficient body fat stores.

Effect of porcine parvovirus serostatus on the reproductive performance of mated gilts in an infected herd.

Gifts from 2 commercial swine operations (farm A and farm B) that were bred each week were tested for porcine parvovirus antibody. On farm A, 21.9% (weekly, 2% to 35%) of the 657 gilts tested over a 16-week period were seronegative within 1 week of mating. On farm B, 17.7% (weekly, o to 40%) of the 164 gilts tested over a 10 week period were seronegative within 1 week of mating. Eighty-one gilts from farm A which were seronegative at time of mating were retested at the end of the gestation. Of the 81 gilts, 4 1 had developed antibody titers. The litter size decreased by 1.3 live pigs/litter. The percentage of small litters (less than or equal to 6 born alive) in the group that seroconverted was 36.6% compared with 10% in the gilts that remained seronegative throughout gestation.

Role of the rat in the transmission of porcine parvovirus.

Rats experimentally inoculated with porcine parvovirus (PPV) shed virus in excreta from 3 to 21 days. Rats inoculated subcutaneously with PPV responded serologically with hemagglutination-inhibition titers (512-1,024). The PPV antigen was readily detected in lung and spleen 2 and 3 days after rats were inoculated and in liver and intestine, 4 days. The rats remained clinically healthy. Rats given PPV orally or in drinking water either with PPV-infected cell culture fluid or swine fetal homogenate failed to respond serologically to PPV, the exception being 2 of 4 rats exposed to swine fetal homogenate over a 5-day span. Pigs exposed to PPV-contaminated rat excreta, either by direct oral dosing or by contaminating the feed, failed to seroconvert. Pigs given (IM) PPV which had been isolated on cell culture from rat excreta did seroconvert. Results of these experiments indicated that rats became infected with PPV, but did so after systemic challenge exposure or prolonged oral exposure to highly infective swine fetal homogenate. Insufficient virus was shed by rats to cause susceptible pigs to seroconvert upon oral feeding--thus indicating that a minimal dose is necessary to ensure oral challenge. In a preliminary experiment, seronegative pigs given different doses of PPV orally showed a gradient level of serologic response and different rates of shedding.

Survey of porcine parvovirus infection in swine fetuses and their dams at a Minnesota abattoir.

Reproductive tracts were recovered from 209 sow and 32 gilt carcasses at slaughter; animals had been pregnant not less than 27 days. Of 241 litters examined, 28 (11.6%) contained one or more porcine parvovirus (PPV)-infected fetuses, as determined by immunofluorescent microscopy. The frequencies in sow and gilt litters were 12.0% and 9.4%, respectively. The PPV antigen was detected in 219 of 334 (65.6%) dead or mummified fetuses and in 12 of 2,172 (0.5%) live fetuses examined. The 18 litters which contained only dead or mummified fetuses were infected with PPV. As the percentage of litter mummification increased, the likelihood of finding PPV increased. The PPV antibody was detected in ovarian follicular fluids of 94.3% of the sows and 78.1% of the gilts. These findings indicate that PPV is highly associated with fetal mummification and that some pregnant gilts and sows are susceptible to infection.