Improving adaptation to weaning: effect of intermittent suckling regimens on piglet feed intake, growth, and gut characteristics.

Daily separation of sows and piglets during lactation, intermittent suckling (IS), improves feed intake and postweaning adaptation in piglets. The aim of the current study was to determine how, in piglets that have been subjected to IS, age at weaning and the duration of the preceding IS period contribute to postweaning adaptation through effects on feed intake, growth, and gut characteristics. All piglets had ad libitum access to creep feed from d 7. Litters were subjected to conventional weaning (CW) or to 1 of 3 IS regimens. In CW, litters (n = 29) had continuous access to the sow until weaning (d 26, d 0 = farrowing). During IS, litters had access to the sow between 1600 and 0600 h. Litters in the IS treatments were subjected to IS 1) from d 19 onward and weaned at d 26 (IS19-7D, n = 33), 2) from d 19 onward and weaned at d 33 (IS19-14D, n = 28), or 3) from d 26 onward and weaned at d 33 (IS26-7D, n = 33). The IS19-7D regimen resulted in a relative growth check within the first 2 d after weaning similar to CW litters (72 +/- 13 and 90 +/- 7%, respectively), but in a greater piglet growth (P = 0.014) and feed intake (P = 0.001) between d 2 and 7 postweaning. Moreover, IS19-7D was not associated with a (further) reduction in villus height as observed at d 2 postweaning in CW litters. In IS piglets weaned after an extended lactation (d 33), a markedly smaller weaning-associated relative growth check was observed shortly postweaning (11 +/- 18 and 32 +/- 19% for IS19-14D and IS26-7D litters, respectively). In these litters, feed intake and growth within the first 2 d after weaning were slightly greater when piglets were subjected to IS for 2 wk (IS19-14D) rather than for 1 wk (IS26-7D; P = 0.032 and P = 0.037 for feed intake and growth, respectively). Irrespective of duration of IS, weaning at d 33 with IS was not associated with a reduction in villus height. Irrespective of treatment, plasma citrulline concentrations were reduced at d 2 and 8 postweaning compared with the values at weaning (P < or = 0.01). No correlation was observed between postweaning plasma citrulline concentrations and postweaning small intestinal villus height. This study indicates that 1 wk of IS before weaning at d 26 of lactation improves feed intake and growth between d 2 and 7 postweaning and does not result in a reduction of villus height as observed in CW piglets, although it did not prevent a profound growth check shortly after weaning. However, combining 1 wk of IS with an extended lactation improved postweaning adaptation markedly in terms of growth, feed intake, and gut characteristics. Increasing the duration of IS from 1 to 2 wk slightly improved growth and feed intake shortly after weaning, but the contribution to postweaning adaptation seemed to be relatively small compared with extending lactation.

Population dynamics of swine influenza virus in farrow-to-finish and specialised finishing herds in the Netherlands.

Influenza virus infections with subtypes H1N1, H3N2 and H1N2 are very common in domestic pigs in Europe. Data on possible differences of population dynamics in finishing pigs in farrow-to-finish herds and in specialised finishing herds are, however, scarce. The presence of sows and weaned piglets on the same premises may, however, affect the exposure of finishing pigs to influenza viruses. In a longitudinal study on 14 farrow-to-finish herds and 15 finishing herds, groups of pigs were followed by repeatedly testing the same animals for antibodies against all three influenza virus subtypes (H1N1, H3N2 and H1N2). At the end of the finishing period, the seroprevalences in farrow-to-finish and specialised finishing herds were 44.3% and 62.0%, respectively for H1N1, 6.6% and 19.3%, respectively for H3N2, and 57.2% and 25.6%, respectively for H1N2. For all three subtypes, the incidence of influenza virus infections was highest at the beginning of the finishing period in farrow-to-finish herds, while the incidence of influenza virus infections was highest at the end of the finishing period in finishing herds. Respiratory disease, probably related to the influenza infections, was observed in five of these herds only, but also occurred at the beginning of the finishing period in farrow-to-finish herds and at the end of the finishing period in finishing herds. The observed differences of population dynamics of influenza virus may affect choice and timing of intervention measures.

Citrulline and intestinal fatty acid-binding protein: longitudinal markers of postweaning small intestinal function in pigs?

The objective of the current study was to investigate whether plasma citrulline or intestinal fatty acid-binding protein (I-FABP) concentrations might be used as longitudinal markers for small intestinal function in piglets after weaning. Plasma citrulline and I-FABP concentrations were measured longitudinally in weaned and unweaned piglets, and related to intestinal absorption values (i.e., plasma mannitol and 3-xylose concentrations in a sugar absorption test). Within each litter (n = 10), 2 piglets with a close-to-litter-average BW were selected. At 20.8 +/- 0.4 d of age, the selected piglets per litter were either weaned conventionally (CW) or remained with the sow (UNW). One day before, and 0.5, 2, 4, and 7 d after weaning of the CW piglets, the selected piglets of both groups were subjected to a sugar absorption test. After a 2-h fast, piglets were administered an oral dose of 2 mL/kg of sugar solution, containing 50 mg/kg of mannitol and 100 mg/kg of 3-xylose. One hour after administration, a blood sample was collected from a jugular vein for determination of plasma I-FABP, citrulline, mannitol, and 3-xylose concentrations. Plasma I-FABP concentration showed great variation within treatments, and no difference was observed in plasma I-FABP concentrations between the CW and UNW treatments (P = 0.63). The absorption of 3-xylose was not different between treatments (P = 0.83). Mannitol absorption, however, was less in the weaned CW piglets compared with the UNW piglets (P = 0.003), with the nadir on d 4 postweaning. Weaning also reduced plasma citrulline concentrations in the CW treatment compared with the UNW treatment (P < 0.001). On d 4 and 7 postweaning, plasma citrulline concentrations of CW piglets were less (P < 0.001 and P = 0.0013) than preweaning values. Furthermore, in the CW treatment, plasma citrulline concentrations correlated with plasma mannitol concentrations at d 4 postweaning (r = 0.89, P = 0.008) and overall (r = 0.76, P = 0.001). Based on these results, plasma citrulline concentration seems to be a possible marker for monitoring intestinal function in pigs after weaning.

Intermittent suckling during an extended lactation period: effects on piglet behavior.

The objectives of the current study were to determine how intermittent suckling (IS) affects nursing behavior, litter activity, and general behavioral patterns during lactation, and whether IS during an extended lactation period results in behavioral patterns associated with piglet distress. Intermittent suckling was applied either with 6-h separation intervals (IS6) or with 12-h separation intervals (IS12) and was compared with the conventional treatment (CT). In the CT (n = 17 litters), sows were continuously present until weaning (d 21, d 0 = farrowing). In both IS6 and IS12, sows were separated from their litter for 12 h/d, beginning at d 14 and lasting until weaning (d 43 +/- 1 d). In IS6, litters (n = 14) and sows were separated from 0800 to 1400 and from 2000 to 0200; in IS12 litters (n = 14) and sows were separated between 0800 and 2000. In IS litters, the activity pattern over the 24-h cycle was markedly changed by IS; litter activity was lower (P < 0.001) during sow absence and greater (P < 0.001) during sow presence compared with the unweaned CT litters. Moreover, both total nursing frequency (P < 0.001) and the percentage (P < 0.002) of successful nursings were reduced by IS. Although total nursing frequency was greater in IS6 compared with IS12 (on d 21 and 28), no differences in the frequency of successful nursings existed between IS6 and IS12 from d 14 onward. Eating behavior was increased shortly after the onset of IS (d 17) in both IS6 (P = 0.059) and IS12 (P < 0.001) compared with the unweaned CT litters. The IS12 litters showed more eating behavior compared with IS6 and their exploratory behavior increased in time (P < 0.001), whereas IS6 showed more nursing behavior. Aggressive or manipulative behavior of both IS treatments was similar compared with the unweaned CT, and remained relatively unaltered with time in IS12 and IS6. Weaning in the CT resulted in more manipulative (P < 0.001) and aggressive (P = 0.004) behavior compared with pre-weaning values. Intermittent suckling may contribute to adaptation to the postweaning state by stimulating eating behavior, without causing obvious behavioral distress.

Effect of herd characteristics, management practices, and season on different categories of the herd somatic cell count.

In this study, the contribution of management practices, herd characteristics, and seasonal variables to the herd somatic cell count (SCC) was quantified in herds with low (<150,000 cells/mL), medium (150,000-200,000 cells/mL), and high (>200,000 cells/mL) herd SCC (HSCC). Selection of the variables was performed using a linear mixed effect model; HSCC was calculated as the arithmetic mean of the individual cow's SCC. The data concerning management practices were derived from 3 questionnaires on mastitis prevention and management practices on 246 Dutch dairy farms. The monthly Dairy Herd Improvement test data of these 246 farms were used to calculate the herd characteristics and seasonal effects. None of the management practices were associated with HSCC in all 3 HSCC categories. Some variables only had a significant association with HSCC in one HSCC category, such as dry premilking treatment (-9,100 cells/mL in the low HSCC category) or feeding calves with high SCC milk (11,100 cells/ mL in the medium HSCC category). Others had an opposite effect on HSCC in different HSCC categories, such as average parity (-6,400 and 11,000 cells/mL in the low and medium HSCC category, respectively) and feeding calves with fresh milk (10,300 and -9,700 cells/ mL in the low and high HSCC category, respectively). We conclude that, given the individual Dairy Herd Improvement data and information on management practices of an individual farm, it is possible to provide quantitative insight into the contribution of these different variables to the HSCC of an individual farm. Being able to provide such insight is a prerequisite for interpretation, prediction, and control of HSCC on individual dairy farms.

Elimination of strains of Streptococcus suis serotype 2 from the tonsils of carrier sows by combined medication and vaccination.

The effect of vaccination with a killed whole-cell vaccine of extracellular factor-positive Streptococcus suis serotype 2 (S suis 2 EF(+)) combined with medication with amoxicillin on the presence of virulent S suis 2 EF(+) strains on the tonsils of sows and their offspring was evaluated. In two herds, 14 pregnant sows that carried these virulent strains, as detected by PCR in three consecutive tonsillar brush samples, were selected and randomly assigned to be treated or left untreated as controls. The treated sows were vaccinated at six and three weeks before the expected farrowing date and medicated from one week before expected farrowing until the end of the experiment. Two weeks before parturition, the sows were housed in individual isolation farrowing rooms, and the sow and its litter were sampled by using tonsil brushes and tonsil swabs, respectively. Approximately 27 days postpartum, the sows and their piglets were euthanased and their tonsils were collected and analysed by pcr. No S suis 2 EF(+) could be detected in the tonsils of the seven treated sows, but the tonsils of the seven untreated sows remained positive. Only one of the litters of the untreated sows became infected, five days after birth, and none of the litters of the treated sows became infected.

Effects of intermittent suckling and creep feed intake on pig performance from birth to slaughter.

An experiment was conducted to determine if the improved creep feed intake observed during intermittent suckling (IS) is important for postweaning performance. Therefore, creep feed intake of litters was assessed, and within litters, eaters and noneaters were distinguished using chromic oxide as an indigestible marker. Batches of sows were suckled intermittently (IS, 7 batches; n = 31) or continuously (control, 7 batches; n = 31). In the IS group, litters were separated from the sow for a period of 12 h/d (0930 to 2130), beginning 11 d before weaning. Litters were weaned at 4 wk of age. Litters had free access to creep feed from 1 wk of age onward. Five days after weaning, the piglets were moved as a litter to weanling pens. At 8 wk of age, 2 barrows and 2 gilts were randomly chosen from each litter and moved to a finishing facility. Feed intake was improved by IS during the last 11 d of lactation (IS, 284 +/- 27 vs. control, 83 +/- 28 g/piglet; P < 0.001) and after weaning during the first (IS, 201 +/- 24 vs. control, 157 +/- 25 g x piglet(-1) x d(-1); P < 0.05) and second (IS, 667 +/- 33 vs. control, 570 +/- 35 g x piglet(-1) x d(-1); P < 0.05) wk. Thereafter, no differences were found to slaughter. Weaning BW was lower in IS litters (IS, 7.1 +/- 0.01 vs. control, 8.1 +/- 0.01 kg/piglet; P < 0.05), but 7 d after weaning BW was similar (IS, 8.5 +/- 0.2 vs. control, 8.7 +/- 0.2 kg/piglet; P = 0.18), and no differences were found to slaughter. The percentage of eaters within a litter was not increased by IS during lactation (IS, 23 +/- 4.5% vs. control, 19 +/- 4.1%; P = 0.15). Weaning BW did not differ between eaters and noneaters (eater, 7.7 +/- 0.1 vs. noneater, 7.5 +/- 0.08 kg/piglet; P = 0.63). From 1 until 4 wk after weaning, piglets that were eaters during lactation had heavier BW than noneaters (eater, 20.3 +/- 0.3 kg vs. noneater, 18.2 +/- 0.2 kg; P < 0.05). The influence of eating creep feed during lactation on BW and ADG and the influence of suckling treatment never showed an interaction. We conclude that IS increases ADFI during lactation on a litter level and improves ADG in the first week and ADFI in the first and second weeks after weaning. No long-term effects on ADFI or ADG were observed throughout the finishing period. In the current experiment, in which creep feed intake was low, the percentage of eaters within a litter was not increased, suggesting that creep feed intake of piglets that were already eating was stimulated by IS. Further, piglets that were eaters during lactation had heavier BW up to 4 wk after weaning.

Postweaning growth check in pigs is markedly reduced by intermittent suckling and extended lactation.

The objective of this study was to determine whether intermittent suckling (IS) combined with an extended lactation can reduce postweaning growth check in pigs. Three weaning regimens [conventional weaning (CW), IS with 6-h separation intervals (IS6), and IS with 12-h separation intervals (IS12)] were compared. In CW (n = 17 litters), litters had continuous access to the sow until weaning (d 21, d 0 = farrowing). In IS6 and IS12, litters were separated from the sow for 12 h/d, beginning at d 14 and lasting until weaning (d 41 to 45). Litters were with the sow from 1400 to 2000 and from 0200 to 0800 (IS6, n = 14) or between 2000 and 0800 (IS12, n = 14). Litter size was standardized within 2 d after farrowing by crossfostering, resulting in an average litter size of 10.9 +/- 1.8 piglets. Piglets had ad libitum access to creep feed from d 7 onward. One week after the onset of IS (d 20), creep feed intake was increased in litters from both IS groups compared with CW litters (P < 0.05). Both IS groups consumed considerable amounts of creep feed before weaning (d 41 to 45). Total feed intake before weaning was greater (P = 0.004) in IS12 (3,808 +/- 469 g/piglet) than in IS6 (2,717 +/- 404 g/piglet). In comparison, CW litters consumed 18 +/- 9 g/piglet before weaning (d 21). Irrespective of weaning regimen, total feed intake of litters before weaning was highly correlated with post-weaning feed intake (P < 0.001). Furthermore, in all treatment groups, total preweaning feed intake was correlated with postweaning growth (P < 0.10). Irrespective of treatment, piglets suckling anterior teats grew faster than piglets suckling middle or posterior teats during the first 2 wk of lactation. Body weights at the end of the experiment (d 55) were similar among weaning regimens. Onset of IS induced a growth check in both IS groups (34% for IS12 and 22% for IS6). Only a mild growth check was observed after weaning of IS litters (14% for both IS groups). However, a serious growth check (98%) was observed after weaning of CW litters. Results of the current study indicate that IS stimulated feed intake during lactation, providing a more gradual transition to weaning. Because the IS6 regimen did not prevent the growth check after the onset of IS and is rather laborious, we suggest that IS12 might be preferable for a practical implementation of IS.

Trimethylated chitosan as polymeric absorption enhancer for improved peroral delivery of peptide drugs.

The absorption enhancing effects of chitosan and its derivatives have been intensively studied in recent years. It has been shown that these compounds are potent absorption enhancers. Chitosan is only soluble in acidic environments and is therefore incapable of enhancing absorption in the small intestine, the main absorption area in the gastrointestinal tract. Special emphasis has been placed on the absorption enhancing properties of N-trimethyl chitosan chloride (TMC), a partially quaternised derivative of chitosan, due to its solubility in neutral and basic environments. TMC is prepared by the reductive methylation of chitosan. The degree of quaternisation can be altered by increasing the number of reaction steps or by increasing the reaction time. Although the molecular weight of the polymer increases with addition of the methyl groups, a net decrease in the molecular weight is observed due to a decrease in the chain length of the polymer. TMC, like chitosan, possesses mucoadhesive properties. In vitro studies performed on Caco-2 cell monolayers showed a pronounced reduction in the transepithelial electrical resistance (TEER). TMC is also able to increase the permeation of hydrophilic compounds such as [14C]-mannitol and [14C] polyethylene glycol 4000 ([14C] PEG 4000, MW4000) across the cell monolayers. It was also shown that the degree of quaternisation of the polymer plays an important role on its absorption enhancing properties, especially in neutral environments where chitosan is ineffective as an absorption enhancer. The reduction in TEER is an indication of the opening of the tight junctions located between epithelial cells. Opening of the tight junctions will result in enhancement of absorption via the paracellular route. Confocal laser scanning microscopy confirmed transport of large hydrophilic compounds via the paracellular route as well as the mechanism of action of the polymer in which redistribution of the cytoskeletal F-actin is provoked, which leads to the opening of the tight junctions. Various in vivo studies in different animal models confirmed the ability of TMC to increase the absorption of the peptide drugs buserelin and octreotide after intraduodenal or -jejunal administration. However, TMC has always been administered as a solution in these studies. The impracticality of administering a solution, as well as the fact that most peptides are unstable in the presence of water, have led to the need for a solid oral dosage form with which TMC can be administered together with peptide drugs. Recent studies have focused on the development and in vivo evaluation of solid oral dosage forms.

Intermittent suckling: effects on piglet and sow performance before and after weaning.

An experiment was conducted to study effects of intermittent suckling on creep feed intake and weight gain of litters. Loss of weight and backfat during lactation, as well as reproductive performance, were also measured. Batches of multiparous sows (Parity 1 to 12, 4.1 on average) were either suckled intermittently (IS, eight batches; n = 50) or continuously (control, eight batches; n = 62). Litters were weaned at 27 +/- 2 d of age, on average. Litter size (11.1 +/- 0.2 piglets, on average) was standardized within a batch within 3 d of birth. All litters had free access to creep feed and water from 1 wk of age onward. In the IS group, litters were separated from the sow for a period of 12 h/d (0930 to 2130), starting 11 d before weaning. Rectal ultrasonography was applied at d 3 after weaning to check the ovaries for follicle development or presence of corpora lutea. Creep feed intake by the litters during lactation was higher in IS litters than in control litters (686 +/- 57 vs. 314 +/- 42 g/piglet, P < 0.01). The distribution of creep feed intake shifted from a skewed one, with a majority of litters consuming less than 250 g/piglet in control litters, to a normal distribution, with an average creep feed intake of 500 to 750 g/piglet in IS litters. During the 7 d after weaning, creep feed intake in IS litters was also higher (281 +/- 15 vs. 204 +/- 9 g-piglet(-1) x d(-1), P < 0.01). The ADG of piglets during lactation was negatively affected by IS, resulting in lower weight at weaning (7,229 +/- 140 vs. 7,893 +/- 145 g/piglet, P < 0.05). During the 7 d after weaning, however, ADG was higher in IS litters (255 +/- 10 vs. 177 +/- 8 g-piglet-1 x d(-1), P < 0.01), and 7 d after weaning, the weights of the litters were similar (9,011 +/- 167 vs. 9,132 +/- 164 g/ piglet, P = 0.81). The IS litters that consumed little or no feed during lactation had an ADG after lactation that was higher than in control litters, with comparable creep feed intake during lactation: 204 vs. 136 g/d. Body weight loss by the sows during lactation was lower in IS sows (-10 +/- 2 vs. -16 +/- 1 kg, P < 0.05). A higher percentage of IS sows ovulated during lactation (22 vs. 3%, P < 0.01), and weaning-to-ovulation interval (excluding sows with lactational ovulation) was shorter in IS sows (4.7 +/- 0.2 vs. 5.3 +/- 0.2 d, P < 0.05). We conclude that IS increased creep feed intake during lactation, and that IS increased ADG after weaning, despite lower weaning weights. Ovulation during lactation was induced in 22% of the IS sows.

A review of porcine reproductive and respiratory syndrome virus in Dutch breeding herds: population dynamics and clinical relevance.

Understanding the spread of porcine reproductive and respiratory syndrome virus (PRRSV) in pig populations is essential to the development of effective PRRS prevention and control strategies. Moreover, knowledge of the field dynamics of PRRSV in pigs will provide insights into the clinical relevance of PRRS, and will enable the targeting of interventions. This review of PRRSV includes discussion on the occurrence of outbreaks, the persistence of infection and the fade-out of infection in Dutch breeding herds. The dynamic character of PRRSV infections in endemically infected herds and the relevance of the disease under Dutch field conditions are also highlighted. Furthermore, several strategies aimed at controlling the spread of PRRSV are discussed.

Design and analysis of an Actinobacillus pleuropneumoniae transmission experiment.

This paper describes a methodology to quantify the transmission of Actinobacillus (A.) pleuropneumoniae from subclinically infected carrier pigs to susceptible contact pigs, and to test the effect of possible interventions on the transmission. The methodology includes the design of a transmission experiment, and a method with which A. pleuropneumoniae transmission can be quantified and with which the effect of an intervention on the transmission can be tested. The experimental design consists of two parts. First, subclinically infected carrier pigs are created by contact exposure of specific-pathogen-free pigs to endobronchially inoculated pigs. Second, transmission is observed from the group of carrier pigs to a second group of susceptible contact pigs after replacing the inoculated pigs by new contact pigs. The presented analytical method is a generalised linear model (GLM) with which the effect of an intervention on the susceptibility and infectivity can be tested separately, if the transmission is observed in heterogeneous populations. The concept of the experimental transmission model is illustrated by describing an A. pleuropneumoniae transmission experiment in which the effect of vaccination on the susceptibility is quantified. Although it could not be demonstrated that vaccination has an effect on the susceptibility of pigs, it was demonstrated that nasal excretion of A. pleuropneumoniae is related to the infectivity of pigs.

Effect of maternally derived antibodies on the clinical signs and immune response in pigs after primary and secondary infection with an influenza H1N1 virus.

The aim of this study was to determine the role of maternally derived antibodies (MDA) against an influenza H1N1 virus in the clinical protection of piglets and especially their effect on the development of the active immunity after an infection with a homologous influenza H1N1 virus. Twenty piglets with MDA and 10 piglets without MDA were housed together and inoculated twice with influenza H1N1 virus, at 7 and 15 weeks of age. Nine piglets without MDA were added to these groups at 12 weeks of age to be inoculated at 15 weeks of age only. Clinical signs, body temperature, growth performance, virus excretion, antibody responses, and influenza-specific T-cell response were monitored. It was shown that MDA protect piglets against the clinical consequences of a primary influenza infection, but that this protection is not complete. A short but significant rise in body temperature was observed and growth seemed to be inhibited due to the infection. Piglets with MDA shed virus for a longer period after an infection than piglets without MDA. Piglets with and without MDA were protected against the clinical consequences of a secondary infection. However, both after primary and secondary infection significant differences in immune responses were observed that indicated that pigs with MDA developed a weaker immunity than pigs without MDA. Furthermore, overall growth performances from weaning to slaughter show a trend in favour of pigs without maternal antibodies, compared to pigs with maternal antibodies, mainly caused by a significant better performance in the second half of the finishing period. The results of this study provide us insight in the role of MDA in clinical protection and their influence on active immunity after an influenza virus infection of pigs. Furthermore, it leads us to the discussion about the profitability of massive sow herd vaccinations in an attempt to increase MDA levels in piglets, taking into account the overall performance of these piglets and the possible effects on antigenic drift.

Effect of follicle-stimulating hormone on nuclear and cytoplasmic maturation of sow oocytes in vitro.

A series of experiments were conducted to evaluate the effects of FSH supplementation during IVM on porcine oocyte nuclear maturation, and subsequent fertilization, cleavage and embryo development. Cumulus-oocyte complexes (COCs) were cultured 40 h without FSH (control), 40 h with FSH (FSH 0-40 h), or 20 h with FSH followed by a 20-h culture period without FSH (FSH 0-20 h). Nuclear stage of oocytes was assessed at intervals from 12 to 40 h of IVM. Furthermore, oocytes were in vitro fertilized, fixed and stained to determine normally fertilized and polyspermic oocytes. Additionally, COCs were matured with FSH, fertilized and zygotes cultured in NCSU-23. The percentage of cleaved embryos and blastocysts were determined and the number of nuclei was counted. The presence of FSH during the first 20 h of IVM retarded germinal vesicle breakdown. After 40 h of culture 84, 67 and 58% MII oocytes were observed in the FSH 0-20 h, FSH 0-40 h and control groups, respectively. After IVF, penetration rates were similar at 27, 26 and 29%, while the proportion of polyspermic oocytes was 7, 19 and 11% of penetrated oocytes for control, FSH 0-40 and FSH 0-20 h groups, respectively. Cleavage and blastocyst rates differed among treatments (21, 29 and 38%, and 7, 15 and 20% for control, FSH 0-40 and FSH 0-20 h groups, respectively). No differences in blastocyst cell number were found among groups. Blastocyst rates, based on number of cleaved embryos, were 51 and 52% for the FSH 0-40 and FSH 0-20 h groups, which differed significantly from the control group (31%). The results indicate that FSH has a stimulatory effect on nuclear and cytoplasmic maturation of sow oocytes. Addition of FSH for the first 20 h of culture was most beneficial, based on cleavage and blastocyst development rates.

Estimating the incidence of influenza-virus infections in Dutch weaned piglets using blood samples from a cross-sectional study.

A cross-sectional study was carried out on 32 Dutch breeding herds to estimate the incidence of influenza-virus infections in piglets before the start of the finishing period, at the age of approximately 10 weeks. Longitudinal studies on two herds (8 and 10 litters, respectively) were done to obtain an average decay function for maternal antibodies.Each participating farm in the cross-sectional study was visited twice within 5 months; each time, blood samples were taken randomly from one compartment (a separate room with separate air flow) of 4-5-week-old piglets and one compartment of 8-9-week-old piglets. These blood samples (a total of 2598; 16-23 per compartment, depending on its size) were tested in a haemagglutination inhibition test for antibodies against influenza-virus subtypes H1 and H3. Samples from 8-9-week-old piglets from the first sampling period (n=660) were also tested in an IgM ELISA. For each individual herd and each influenza-virus subtype separately, the decay function derived from the longitudinal studies was used to calculate an expected seroprevalence in 8-9-week-old piglets, which was then compared to the observed seroprevalence. Depending on subtype and sampling period, between 10 and 15 of the 32 herds were suspected of virus circulation during the weaning period because the observed seroprevalence was significantly higher than the expected seroprevalence (P<0.05). In the first sampling period the IgM ELISA confirmed six of these outbreaks. However, due to the small window of detection of the IgM ELISA (compared to the length of the weaning period), it will always underestimate the number of infections. Infections in the first half of the weaning period will no longer be detectable because IgM antibodies have already disappeared. In individual pigs, an incidence of 16-17% was estimated for each subtype over a 4-week period between the age of 4-5 and 8-9 weeks. For each influenza subtype, 80% of the piglets will enter the finishing facilities without antibodies or with decaying maternal antibodies. These piglets may be susceptible to an infection with influenza virus.

Assessment of respiratory herd health in weaner pigs by measuring cellular composition of bronchoalveolar lavage fluid.

Cell differentiation of bronchoalveolar lavage fluid (BALF) was compared among 11 herds having a history of recurrent respiratory disease in weaner pigs and nine herds lacking such a history. In every herd, 20 pigs aged 8-10 weeks were lavaged. The two groups differed significantly on median percentage of macrophages, neutrophils and lymphocytes, but not on white blood cell count of the BALF. Logistic regression showed the percentage of samples per herd exceeding the reference value for neutrophils of 0-8% to be the most promising parameter to assess the health status in weaner pigs.

Intestinal absorption of human insulin in pigs using delivery systems based on superporous hydrogel polymers.

In this in vivo study, novel delivery systems based on superporous hydrogel (SPH) and SPH composite (SPHC) polymers were used to improve the intestinal absorption of insulin in healthy pigs. Six female pigs of approximately 35 kg body weight were used. A cannula was inserted into the jugular vein for blood sampling and a silicone fistula in the duodenum for administration of gelatin capsules containing the delivery systems or insulin solutions. The delivery systems consisted of two components, (1) conveyor system made of SPH and SPHC; (2) core containing insulin. The core was inserted either into the conveyor system (core inside, c.i.) or attached to the surface of conveyor system (core outside, c.o.). The following intestinal formulations were investigated: c.i., c.o. and intraduodenal (i.d.) administration of insulin solutions. Subcutaneous (s.c.) injection of insulin was also investigated for reasons of comparison. Blood samples were taken and analyzed for insulin and glucose concentrations. Relative bioavalibility values of 1.3+/-0.4 and 1.9+/-0.7% were achieved for c.o. and c.i. administrations, respectively. The bioavalibility for i.d. administration of insulin solution was 0.5+/-0.2%. These results indicate that the absorption of insulin was slightly increased using SPH/SPHC-based delivery systems. Furthermore, a large variability was observed, probably due to physiological and metabolic changes during the experiments. Blood glucose levels were slightly decreased after the c.o. and c.i administrations, whereas these levels did not decrease after i.d. administration of insulin solutions. In conclusion, SPH/SPHC-based delivery systems are able to enhance the intestinal absorption of insulin and are, therefore, considered as promising systems for peroral peptide drug delivery. However, insulin delivery from these delivery systems under in vivo have to be improved.

Pharmacokinetics of sulfadimethoxine and sulfamethoxazole in combination with trimethoprim after oral single- and multiple-dose administration to healthy pigs.

The pharmacokinetics were studied of sulfadimethoxine (SDM) or sulfamethoxazole (SMX) in combination with trimethoprim (TMP) administered as a single oral dose (25 mg + 5 mg per kg body weight) to two groups of 6 healthy pigs. The elimination half-lives of SMX and TMP were quite similar (2-3 h); SDM had a relatively long half-life of 13 h. Both sulfonamides (S) were exclusively metabolized to N4-acetyl derivatives but to different extents. The main metabolic pathway for TMP was O-demethylation and subsequent conjugation. In addition, the plasma concentrations of these drugs and their main metabolites after medication with different in-feed concentrations were determined. The drug (S:TMP) concentrations in the feed were 250:50, 500:100, and 1000:200 mg per kg. Steady-state concentrations were achieved within 48 h of feed medication, twice daily (SDM+TMP) or three times a day (SMX+TMP). Protein binding of SDM and its metabolite was high (>93%), whereas SMX, TMP and their metabolites showed moderate binding (48-75%). Feed medication with 500 ppm sulfonamide combined with 100 ppm TMP provided minimum steady-state plasma concentrations (C(ss,min)) higher than the concentration required for inhibition of the growth of 90% of Actinobacillus pleuropneumoniae strains (n = 20).

Intestinal absorption of octreotide using trimethyl chitosan chloride: studies in pigs.

PURPOSE: To investigate the enhancing effect of trimethyl chitosan chloride (TMC) on the enteral absorption of octreotide and to delineate the required doses of both TMC and peptide in vivo in juvenile pigs. METHODS: Six female pigs (body weight, 25 kg) were operated to induce a stoma at the beginning of their jejunum and to insert an in-dwelling fistula for intrajejunal (IJ) administration of the formulations. A silicone cannula was inserted at the jugular vein for blood sampling. One week after surgery the pigs received IJ octreotide solution administrations with or without TMC at pH 7.4 or chitosan HCl at pH 5.5. For determining bioavailability (F) values, the pigs also received an octreotide solution intravenously (IV). Blood samples were taken from the cannulated jugular vein and subsequently analyzed by radioimmunoassay. RESULTS: Intrajejunal administration of 10 mg octreotide without any polymer (control solution) resulted in F values of 1.7 +/- 1.1% (mean +/- SE). Chitosan HCl 1.5% (w/v) at pH 5.5 led to a 3-fold increase in F compared to the control (non-polymer containing) formulations. Co-administration of octreotide with 5 and 10% (w/v) TMC at pH 7.4 resulted in 7.7- and 14.5-fold increase of octreotide absorption, respectively (F of 13.9 +/- 1.3% and 24.8 +/- 1.8%). IJ administration of 5 mg octreotide solutions resulted in low F values of 0.5 +/- 0.6%, whereas co-administration with 5% (w/v) TMC increased the intestinal octreotide bioavailability to 8.2 +/- 1.5%. CONCLUSIONS: Cationic polymers of the chitosan type are able to enhance the intestinal absorption of the peptide drug octreotide in pigs. In this respect, TMC at neutral pH values of 7.4 appears to be more potent than chitosan HCl at a weak acidic pH of 5.5.

A quantitative assessment of the effectiveness of PRRSV vaccination in pigs under experimental conditions.

This paper presents a quantitative approach to evaluate effectiveness of vaccination under experimental conditions. We used two consecutive experimental designs to investigate whether PRRSV transmission among vaccinated pigs was reduced compared to control pigs and to estimate the reproduction parameter R. Based upon data analysis and power calculations the series of small-scale vaccination-challenge experiments ended with multiple one-to-one experiments. This new experimental design has considerable power to detect the effect of vaccination on transmission if R is close to but still above one in vaccinated pigs. The last experiment showed that transmission was not significantly reduced and the R for vaccinated pigs was estimated to be larger than 4.9. This is remarkable because duration and level of viremia were significantly reduced by vaccination.