Commercial spray-dried porcine plasma does not transmit porcine circovirus type 2 in weaned pigs challenged with porcine reproductive and respiratory syndrome virus

The objective of this study was to evaluate if spray dried porcine plasma (SDPP) containing porcine circovirus type 2 (PCV2) genome supplemented in feed could transmit PCV2 to pigs challenged with porcine reproductive and respiratory syndrome virus (PRRSV). Twenty-three PRRSV-free pigs, non-viraemic for PCV2, were housed in bio-safety level 3 facilities and assigned to four groups in a 2×2 factorial design consisting of PRRSV challenge and a negative control. The diet contained 0 or 8kg SDPP per 100kg of feed. PRRSV challenge groups were inoculated intranasally with 2mL of a suspension containing 10(6) TCID(50)/mL PRRSV. The SDPP used in the study contained 7.56×10(5) PCV2 genome copies per gram. Dietary treatments were fed from 4days prior to PRRSV inoculation until 28days post-inoculation (PI). All challenged pigs developed PRRSV viraemia by day 3PI and PRRSV antibodies were detected in sera by day 14PI, with no difference between diet treatments. Neither PRRSV viraemia nor seroconversion was observed in non-challenged pigs. PCV2 was not detected in the serum of any pigs throughout the experimental period. SDPP containing the PCV2 genome supplemented in feed did not result in PCV2 transmission to either healthy or PRRSV-infected pigs under these experimental conditions.     

Impact of energy intake and pregnancy status on rate and efficiency of gain and backfat changes of sows postweaning

A collaborative study was conducted to evaluate factors related to determining optimal feeding and management programs for increasing net returns from marketing cull sows. A total of 269 multiparous sows averaging 192 kg of body weight were weaned, moved to individual gestation crates, and assigned to one of eight treatment combinations in a 2 x 2 x 2 factorial arrangement for a 42-d postweaning feeding experiment. Factors included limited (L) (1.8 kg/sow/d) or ad libitum (AL) access to feed during wk 1 postweaning, a corn-soybean meal (corn) or barley-sunflower meal (barley) diet, and pregnant or nonpregnant status. All sows were provided ad libitum access to feed from wk 2 to 6 postweaning. Gain and feed intake (FI) data were collected weekly for each sow and used to calculate gain:feed (G/F). Ultrasonic backfat (BF) data were collected on d 0, 21, and 42 postweaning. Sows on the AL treatment had greater FI (P < 0.05) but similar gain (P = 0.80) for the 42-d postweaning period compared to sows on the L treatment. Most of this response was due to lower sow body weight loss during wk 1 postweaning (P < 0.01) when sows were provided AL (-7.2 kg) vs L (-13.2 kg) access to feed. Sows fed the corn diet had higher gain (P < 0.01), improved G/F (P < 0.01), and increased BF (P < 0.01) over the 42-d feeding period than sows fed barley. The corn diet resulted in less sow BW loss (P < 0.01) during wk 1 (-8.8 kg) than the barley diet (-11.6 kg). Pregnant sows had higher gain, FI, G/ F, and BF (P < 0.01) than nonpregnant sows over the 42-d feeding period. Most of this advantage occurred during wk 4 postweaning when FI and gain of nonpregnant sows was lower (P < 0.01) than for pregnant sows. An economic analysis indicated that, when cull sow prices are relatively high and feed prices are moderate to low, maintaining and managing cull sows for an additional 6 wk postweaning may be economically advantageous compared to 0 or 3 wk. Pregnant sows fed the corn diet produced the greatest economic return. These results suggest that mating sows as they return to estrus postweaning and providing ad libitum access to a corn-soybean meal diet improves growth performance and feed efficiency, and may thereby provide increased returns when marketing cull sows.     

The biological stress of early weaned piglets

Pigs experience biological stress such as physiological, environmental, and social challenges when weaned from the sow. The process of weaning is one of the most stressful events in the pig’s life that can contribute to intestinal and immune system dysfunctions that result in reduced pig health, growth, and feed intake, particularly during the first week after weaning. Technological improvements in housing, nutrition, health, and management have been used to minimize some of the adverse effects of weaning stress, but a greater understanding of the biological impact of stress is needed to improve strategies to overcome weaning stress. The focus of this review paper is to briefly describe how the biological stress associated with weaning impacts intestinal morphology, structure, physiology, and intestinal immune responses that can impact subsequent production efficiencies such as growth, intake, morbidity, and mortality.     

The effect of dietary potassium and chloride on cation-anion balance in swine

The apparent retention and excretion of cations and anions were evaluated in 20 growing pigs to study the mechanisms by which an interaction between dietary K and Cl levels affected growth. All pigs maintained a positive retention of K+ and Cl- regardless of the dietary levels. The K x Cl interaction observed in growth studies previously but not in this study could not be explained by a simple interaction of one ion on the retention of the other. When pooled across dietary Cl levels, an increase in dietary K levels from .10 to .60% resulted in a calculated increase in daily K+ intake of 4.86 meq/kg of BW. Sixty percent (2.99 meq) of the increased K+ intake was excreted in the urine and counterbalanced by a decrease in urine NH4+ (3.06 meq). This decrease in NH4+ excretion could account for essentially all of the increase in N retention (3.51 mmol) observed when dietary K levels were increased from .10 to .60%. Thirty-three percent of the increased K+ intake (1.62 meq) was retained, but the counter ion could not be determined. Retention of Cl- was not changed as dietary K levels were changed. When dietary Cl levels were increased from .03 to .57%, 69% (4.06 meq) of the calculated difference in Cl- intake (5.90 meq) was excreted in the urine, which must have been counterbalanced by a decrease in undetermined organic anions (1.77 meq) and HPO4 = (1.50 meq) excretion, with a tendency for an increased NH4+ (.82 meq) excretion. The counter ions required to balance the increased Cl- retention (1.82 meq) as dietary Cl levels were increased from .03 to .57% could not be identified. Shifts in the retention and urinary excretion of Ca++, Na+, HCO3-, and SO4= did not seem to be quantitatively important in identifying the mechanisms by which dietary K and Cl levels alter growth. Based on these results, we conclude that alterations in growth caused by changes in dietary K and possibly Cl levels are mediated via mechanisms involving renal NH4+ metabolism.     

Comparison of dietary selenium fed to grower-finisher pigs from various regions of the United States on resulting tissue Se and loin mineral concentrations

A study was conducted to evaluate the mineral content of pork tissue with particular emphasis on Se between various states (regions) having different diet (grain) indigenous Se concentrations. The study involved 19 states in the north, central, and southern regions of the United States, with committee members of NCR-42 and S-1012 (formerly S-288). A total of 62 pigs were used, with collaborators sending 100-g samples each of loin, heart, and liver, and a 3- to 4-g sample of hair (collected along the topline) from two to five market-weight pigs to a common laboratory for analysis. Diets at each station were formulated with locally purchased soybean meal and grain that was either grown or normally fed to pigs within their state. Tissues were analyzed for Se, but only the loin was analyzed for the macro- and micromineral elements. Correlation of dietary minerals to the tissue element was determined. The results demonstrated differences in tissue Se among states (P < 0.01), with high correlations of dietary Se to loin (r = 0.84; P < 0.01), heart (r = 0.84; P < 0.01), liver (r = 0.83; P < 0.01), and hair Se (r = 0.90; P < 0.01) concentrations. The correlation of hair Se to the Se concentration of loin, heart, and liver tissues was high (r > 0.90; P < 0.01). States in the west-central region of the United States and west of the Mississippi river had higher dietary Se and tissue Se concentrations than states in the eastern section of the Corn Belt, east of the Mississippi river, and along the East Coast. Generally, states did not differ greatly in their loin macro- and micromineral concentrations. The simple correlation of dietary minerals to their corresponding loin mineral concentration was generally non-significant, but most macrominerals had decreasing mineral concentrations when the dietary mineral level was higher. These results indicate that regional differences in tissue Se were influenced more by the indigenous Se content of the diet (grain) fed to the pigs than from sodium selenite.