Gilt Progeny Research Articles

A comparative analysis of gastrointestinal tract barrier function and immune markers in gilt vs. sow progeny at birth and weaning.

Progeny born to primiparous sows (gilt progeny; GP) have lower birth, weaning and slaughter weights than sow progeny (SP). GP also have reduced gastrointestinal tract (GIT) development, as evidenced by lower organ weights. Therefore, the aim of this experiment was to quantify changes in GIT barrier function that occur in birth and weaning, representing two major challenges to the young piglet. The effects of parity (GP vs. SP) in GIT barrier integrity function were quantified at four timepoints: birth (~0h), 24h after birth (24h), 1-d preweaning (PrW), and 1-d postweaning (PoW) in commercially reared piglets. Due to inherent differences between newborn and weanling pigs, the results were analyzed in two cohorts, birth (0 vs. 24h, n = 31) and weaning (PrW vs. PoW, n = 40). Samples of the stomach, jejunum, ileum, and colon were excised after euthanasia and barrier integrity was quantified by measuring transepithelial resistance (TER), macromolecular permeability, the abundance of inflammatory proteins (IL-8, IL-1β, and TNF-α) and tight junction proteins (claudin-2 and -3). Papp was characterized using a dual tracer approach comprising 4 KDa fluorescein isothiocyanate (FD4) and 150kDa tetramethyl rhodamine isothiocyanate (T150)-labeled dextrans. Characteristic effects of the initiation of feeding and weaning were observed on the GIT with the initiation of feeding, such as increasing TER and reducing Papp at 24h, consistent with mucosal growth (P = 0.058) This was accompanied by increased cytokine abundance as evidenced by elevations in TNF-α and IL-1β. However, GP had increased IL-8 abundance (P = 0.011 and 0.063 for jejunum and ileum respectively) at birth than 24h overall. In the weaning cohort, jejunal and ileal permeability to FD4 was higher in GP (P = 0.05 and 0.022, respectively) while only higher ileal T150 was observed in GP (P = 0.032). Ileal claudin-2 abundance tended to be higher in SP overall (P = 0.063), but GP ileal claudin-2 expression was upregulated weaning while no change was observed in SP (P = 0.043). Finally, other than a higher jejunal TNF-α abundance observed in SP (P = 0.016), no other effect of parity was observed on inflammatory markers in the weaning cohort. The results from this study indicate that the GIT of GP have poorer adaptation to early life events, with the response to weaning, being more challenging which is likely to contribute to poorer postweaning growth.

2. Gilt progeny dams have higher litter sizes compared to sow progeny dams which may be influenced by differences in early reproductive development

2. Gilt progeny dams have higher litter sizes compared to sow progeny dams which may be influenced by differences in early reproductive development

1. Investigating gilt progeny birth weight variation, serum immunoglobulin concentration soon after birth and pre-weaning survival compared to sow progeny, and relationships with maternal grand-dam parity

1. Investigating gilt progeny birth weight variation, serum immunoglobulin concentration soon after birth and pre-weaning survival compared to sow progeny, and relationships with maternal grand-dam parity

Dam parity structure and body condition during lactation influence piglet growth and gilt sexual maturation through pre-finishing.

Energy demands during lactation greatly influence sow body condition and piglet performance. We hypothesized that primiparous sows or sows with reduced body condition would produce piglets with reduced growth and delayed sexual maturation. Eight weekly farrowing seasons were used to evaluate sow body condition (post-farrowing, PF and weaning, WN) and piglet growth from 157 dams. Body condition was measured at PF and WN using sow calipers (last rib and hip) and 10th rib ultrasound. Sows were categorized as thin, moderate, or fat by caliper (PF or WN). Individual pig weights were recorded on approximately 1, 10, WN, 45, 100, and 145 d of age. At 100 and 145 d of age, 10th-rib backfat and loin eye area were measured on 567 pigs and first estrus was monitored in 176 gilts reserved for breeding selection beginning at approximately 170 d of age. Sows had similar (P > 0.10) PF last rib caliper measurements but at WN, first parity sows had the smallest caliper measurements compared to other parities (P < 0.05). Parities 1, 2, and 3 sows had similar (P > 0.10) loin eye area at PF; however, at WN first parity sows had the smallest loin eye area (P < 0.05; 38.2±0.63cm2). Parity 1 sows had the greatest (P < 0.05) reduction of backfat and loin eye area over the lactation period (-2.9±0.31mm and -2.6±0.49cm2, respectively). At 1 d of age and WN, piglets from first parity sows weighed the least (P < 0.05) but were the heaviest (P < 0.05) at 100 and 145 d of age. Pigs from first parity litters had larger (P < 0.05) loin eye area at 100 and 145 d of age and greater backfat (P < 0.05) at 145 d of age. Fat sows at WN (last rib or hip) had the lightest (P < 0.05) piglets at 10 d of age and WN. However, at 45 d of age, piglets from fat sows (last rib or hip) were heavier (P < 0.05) than piglets from moderate and thin sows. Tenth rib backfat at 100 and 145 d of age tended (P < 0.10) to be less in pigs reared by thin sows (PF and WN hip). Tenth rib loin eye area was similar among pigs reared by fat, moderate, or thin sows. Gilts developed in litters from fourth parity sows had (P < 0.05) delayed age at puberty in contrast to gilts from first or third parity sows (200.9±4.96 d vs. 189.0±2.29 d and 187.5±2.84 d, respectively). Although progeny body weights were typically less from first parity dams through 45 d of age, these progeny were similar or heavier at 100 and 145 d of age in contrast to progeny from other parities. Furthermore, gilt progeny from first parity dams did not have delayed pubertal attainment.

4. Feeding a low inclusion of conjugated linoleic acid improves the performance of gilt progeny when only supplied 1 week before farrowing

4. Feeding a low inclusion of conjugated linoleic acid improves the performance of gilt progeny when only supplied 1 week before farrowing

Exposure to maternal feces in lactation influences piglet enteric microbiota, growth, and survival preweaning.

It is known that gilt progeny performance is reduced compared with sow progeny. Previous research suggests that the presence of maternal feces in early life improves the health and survival of offspring. Therefore, we aimed to determine whether contact with feces from multiparous (MP) sows would improve the growth and survival of piglets born and reared on primiparous (P1) sows and if so, whether these differences are associated with the gut microbiota. Four treatments were applied for 10 days: Donor (n = 29) piglets had limited access to maternal feces as, each morning, sow feces were removed and placed in the crate of a P1 sow (P1-FT; n = 30 piglets) and P1-Con (n = 29) and MP-Con (n = 33) piglets had access to their own mothers’ feces. All piglets were weighed on days 1, 3, 10, and 18. Fecal samples were collected from a subset of sows (n = 10/treatment) 3 days post farrow and from two female piglets/litter on days 10 and 18 (n = 20/treatment) and subject to 16S rRNA amplicon analysis. Escherichia, Clostridium, Campylobacter, and Treponema were more abundant in MP sows, while P1 sows had a higher abundance of Lactobacillus and Prevotella. At 10 days, P1 progeny fecal microbiota differed, and growth and survival were reduced when compared with MP progeny. No treatment effect was observed for P1-FT piglets (P > 0.05). Donor piglets had a different fecal microbiota and improved weight and survival then all other treatments (P < 0.05). Overall, the removal of sow feces from the farrowing crate improved piglet microbiota development, growth, and survival.

Increasing creep pellet size improves creep feed disappearance of gilt and sow progeny in lactation and enhances pig production after weaning

Objective: To determine if feeding a larger diameter pellet increases creep feed intake and growth rate of piglets during lactation, especially that of gilt progeny (GP) compared to sow progeny (SP), and stimulates feed intake after weaning. Materials and methods: Over two replicates, GP and SP (n = 2070) were allocated to two creep feed treatments, receiving either a 4 mm diameter × 4 mm length pellet or a 9 mm diameter × 12 mm length pellet, from 3 days of age until weaning. After weaning, pigs were split into male and female pens according to the type of pellet fed in lactation and fed a common diet. Feed disappearance was recorded before and after weaning (up until 10 weeks of age), along with piglet growth performance and all piglet mortalities and removals. Results: Total creep feed disappearance in lactation was higher (P &lt; .001) in litters offered the larger pellet, but litter weaning weight for GP was not improved (interaction, P &gt; .05). Gilt progeny were weaned lighter (P &lt; .001) than SP. After weaning, pigs offered the larger pellet during lactation showed a tendency to receive less medication (P = .07) than pigs offered the smaller pellet. Growth rate and feed intake after weaning were both stimulated (P = .02 and P = .09, respectively) in pigs offered the larger pellet during lactation irrespective of sex. Implications: Offering a larger pellet creep feed to piglets in lactation can improve postweaning performance and reduce the postweaning medication rate.

Evaluation of Sugarcane-Derived Polyphenols on the Pre-Weaning and Post-Weaning Growth of Gilt Progeny.

Simple SummaryGilt progeny are characterised by their poor lifetime growth performance compared with sow progeny. Various feeding strategies that employ the use of additives may be used to improve their growth. Gilts are said to be in increased oxidative stress throughout lactation, which may contribute to the reduced growth performance seen in their progeny. Furthermore, weaning is associated with increased inflammation, which can reduce growth after weaning. In this study, both late gestation/lactation diets and weaner diets were supplemented with a sugarcane extract rich in polyphenols owing to their anti-oxidative and anti-inflammatory properties to collectively improve the growth of gilt progeny. However, no improvements of growth performance of gilt progeny in both the pre-weaning and post-weaning periods were observed in response to polyphenol supplementation and sow progeny continuously outperformed gilt progeny. Furthermore, when inflammation was measured using the inflammatory cytokine interleukin-1β, no differences were found between the control and polyphenol supplemented group. However, gilt progeny exhibited reduced circulating interleukin-1β overall. In summary, gilt progeny experience persistent underperformance that may be coupled in part to poorer immune development and polyphenol supplementation did not overcome the persistent underperformance.Gilt progeny (GP) exhibit poorer growth compared with sow progeny (SP), particularly in the pre-weaning and post-weaning period. Late gestation/lactation sow diets and weaner diets were supplemented with 0.5% Polygain (POL), a sugarcane extract rich in polyphenols, to collectively improve GP growth in these periods. Gilts (n = 60) and sows (n = 68, parities 2 and 3) were fed a control or POL diet. Weaned GP (n = 79) and SP (n = 92) born to these dams were also fed either a CON or POL diet. Gilts litters weighed less than sow litters at birth and 21 days (p < 0.001 for both) and were not improved by POL (p = 0.80 and 0.54, respectively). GP were lighter than SP at day 7 and day 14 post-weaning (p < 0.001 for both) and were not improved by the POL diet at these timepoints (p = 0.61 and 0.97, respectively). Plasma interleukin-1β (IL-1β) was increased at weaning despite POL supplementation (p = 0.022) and GP had reduced IL-1β overall (p = 0.021). Overall, POL was unable to improve growth in GP and the attenuated immune response seen in GP could be contributing to their poor growth performance.

193 Characterisation of poor gastrointestinal tract development in gilt progeny

Abstract Progeny of primiparous sows (gilts) have poor production performance compared to those of multiparous sows. This has been attributed to underlying biological events that occur early in life. We specifically focused on the development of the gastrointestinal tract (GIT) and its function in sow vs gilt progeny (SP vs GP) reared under commercial conditions. Piglet tissues were harvested at birth, at 24 h, and pre- and post-weaning (28 v 29 d) and used to quantify GIT integrity. All data were analysed using Genstat V18 for the effects of parity (sow vs gilt) in birth (0 vs 24 h) and weaning (pre- vs post) cohorts. GIT integrity was quantified from freshly excised tissue in Ussing chambers for transepithelial electrical resistance (TER) and macromolecule permeability (FD4; labelled 4kD dextran). Permeability was measured in stomach, colon, jejunum and ileum. Over the 24-h neonatal period, TER was significantly reduced in the stomach and colon (P = 0.048 and 0.003 respectively) with GP having lower stomach TER than SP (P = 0.015). TER increased in the jejunum and ileum over the 24-h neonatal period (P = 0.004 and 0.002 respectively). An interactive effect of parity and time on ileum FD4 was observed (P = 0.043) where FD4 in SP ileum decreased over the 24-h neonatal period and FD4 in GP ileum increased over the 24-h period (P = 0.043). Jejunum FD4 was significantly higher in GP than SP over the 24-h neonatal period (P = 0.048). An interactive effect of parity and time was observed in the colon over the weaning period where TER increased in SP but decreased in GP (P = 0.005). Stomach TER decreased over the weaning period in both GP and SP (P = 0.013). Jejunum and ileum TER decreased over the weaning period (P = 0.003 and 0.057 respectively). Ileum FD4 was higher in GP than SP over the weaning period (P = 0.037). These findings reflect a reduction in GIT development in GP compared with SP, and gut leakiness may be an underlying reason for poorer production performance and increased morbidity of GP.

Dietary Inclusion of 1,3-Butanediol Increases Dam Circulating Ketones and Increases Progeny Birth Weight.

1,3-Butanediol (BD) is a ketogenic substance that can improve piglet growth and survival and potentially increase performance in gilt progeny when provided as a dietary supplement during late gestation. Gilts (n = 77; parity 1) and sows (n = 74; parities 2 and 3) were fed either a standard commercial gestation diet or a diet supplemented with 4% BD from day 90 of gestation until farrowing. Dams fed with diets supplemented with BD had higher plasma beta-hydroxybutyrate (p = 0.01) and lower non-esterified fatty acid concentrations (p < 0.001). The percentage of progeny that were light-for-age (<1.1 kg) at birth was decreased by BD (18.2 vs. 13.5%, p < 0.006), particularly in gilts (24.0 vs. 18.3%, p < 0.034). Individual birth weights and litter weights birth weights tended to be increased by the BD diet (p = 0.085 and 0.078; respectively) although these effects were not maintained to weaning. Pre-weaning mortality was greater in gilt than in sow progeny and was not altered by dietary BD. Feeding BD in late gestation can improve birth weight, but further work is needed to see if these effects are carried through subsequent stages of growth, particularly in gilt progeny.

Selection for feed efficiency in Duroc pigs with the addition of daily feed intake data in a 2-stage selection procedure

ABSTRACT The objective of this study was to evaluate the effect of including feed intake records of boars on the genetic gain for feed efficiency. Data were obtained from a Duroc nucleus herd within a Chinese company’s breeding system. The data obtained included ADG, feed conversion ratio (FG), ADFI, days to 115 kg, backfat depth, and loin muscle area. The ADG, FG, and ADFI data were obtained from 570 Duroc boars housed in pens with electronic feeders (FIRE, Feed Intake Recording Equipment, Osborne Industries, Osborne, KS). There were 4,984 Duroc boar and 4,809 gilt progeny. Two sets of estimated breeding values for ADG, FG, ADFI, days to 115 kg, backfat depth, and loin muscle area were estimated using a multivariate animal model, with and without data collected from the FIRE feeders. Terminal sire indices were calculated based on the production costs and market prices for the United States and China. A 2-stage selection procedure was applied with the heaviest sound boars (mean age = 130 ± 17 d) being tested in the FIRE feeder and then the top 100 being selected for breeding. The terminal sire index value gain estimated with ADFI data included was 9.3% greater than the estimates that did not include the ADFI data. The estimated genetic gain for FG with ADFI data was 17% greater than the same annual estimated genetic gain without ADFI data. Overall, there is a substantial genetic gain of FG when individual ADFI records of boars were included in the selection index.

Primiparous and Multiparous Sows Have Largely Similar Colostrum and Milk Composition Profiles Throughout Lactation.

Simple summaryProgeny born to primiparous sows (gilt progeny) are born lighter, grow slower, and have higher rates of mortality than piglets born to multiparous sows. An understanding of why this might be the case is necessary to implement management strategies that improve the health and welfare of first-litter piglets and increase their production efficiency. Differences in the composition of colostrum and milk between primiparous and multiparous sows might be a contributing factor. Results from this study suggest that primiparous and multiparous sows (parities 3 and 4) have similar levels of immunoglobulin G and energetic components (net energy, fat, protein, and lactose) in colostrum and milk throughout the course of lactation. However, lower lactose levels from day 14 onwards in milk from primiparous sows compared to milk from multiparous sows may indicate that there is a reduction of lactose uptake into the mammary gland in primiparous sows during late lactation, which may reduce milk volume. Lower growth rates and higher rates of mortality in gilt progeny are therefore likely to be as a result of lower colostrum and milk production in primiparous sows and (or) an inability of their piglets to digest these nutritional components effectively.It is important to understand the biological factors influencing the poorer lifetime performance of gilt progeny in comparison to sow progeny and determine whether this may be partially due to differences in lactation performance between primiparous and multiparous sows. It was hypothesized that primiparous sows would have lower levels of immunoglobulin G (IgG) in colostrum and milk compared to multiparous sows, and lower levels of other energetic components. Differences in colostrum and milk composition between ten primiparous and ten multiparous sows (parities 3 and 4) from a commercial herd were examined throughout lactation (day 0, 1, 2, 3, 7, 14, and 21). Overall, there were no (p ≥ 0.05) parity differences in total IgG, fat, protein, lactose, and net energy (NE) concentrations. Primiparous sows had higher lactose levels at day 2 (parity by timepoint interaction; p = 0.036) and lower NE at day 3 (p = 0.091), and multiparous sows had higher lactose levels at days 14 and 21. Results suggest that shortcomings of gilt progeny are unlikely due to insufficient nutrient levels in colostrum and milk, and more likely to reduced colostrum and milk intake and their capacity to digest and absorb each component.

Reduced growth performance in gilt progeny is not improved by segregation from sow progeny in the grower–finisher phase

Gilt progeny (GP) are born and weaned lighter than sow progeny (SP) and tend to have higher rates of mortality and morbidity. This study quantified the lifetime growth performance differences between GP and SP and, additionally, evaluated whether segregating GP and SP in the grower–finisher period compared to mixing them within common pens reduced this variation. It was hypothesised that GP would be lighter than SP at every stage and segregation would improve growth performance of both GP and SP. All piglets born to 61 gilts (parity 1) and 47 sows (parities 2 to 7; mean 3.5 ± 0.2) were allocated to four treatments at 10 weeks of age: (i) GP housed together (GG), (ii) GP mixed (M) with SP (GM), (iii) SP housed together (SS) and (iv) SP mixed with GP (SM). The GM and SM pigs were housed together in common pens after movement into the grower–finisher facility. Individual live weight of all progeny was recorded at birth, weaning (WWT), 10 weeks of age (10WT) and sale (SWT). Individual hot carcass weight (HCW), fat depth at the head of the last rib (P2) and dressing percentage were measured at slaughter. Gilt progeny were lighter at birth (P = 0.038), weaning (P < 0.001) and through to sale (P = 0.001) than SP. Nursery and grower–finisher performance differences in GP were highly attributable to their lower WWT compared to SP (P < 0.001 when fitted as a covariate). Segregation of GP and SP increased grower–finisher average daily gain (ADG) in SP but decreased ADG and SWT in GP (P < 0.10). Segregated SP had increased average daily feed intake but only in males (P = 0.007); HCW (P < 0.001) and P2 fat depth (P = 0.055) were higher in mixed female GP, but there was no difference (P > 0.10) in female SP, or in males. In conclusion, GP were lighter at every stage than SP and differences after weaning were highly related to the lighter WWT of GP. Under the conditions of this study, overall segregation of GP and SP showed no consistent advantages in growth performance for both groups and differed significantly between males and females.

Poorer lifetime growth performance of gilt progeny compared with sow progeny is largely due to weight differences at birth and reduced growth in the preweaning period, and is not improved by progeny segregation after weaning.

Gilt progeny (GP) are born and weaned lighter than sow progeny (SP) and have higher rates of mortality. This study aimed to quantify the performance and survival differences between GP and SP throughout the entire production cycle from birth to sale. Furthermore, the study looked at the effects of segregating GP and SP compared with commingling during rearing within common pens. It was hypothesized that GP would be lighter than SP at every age and have lower rates of survival accompanied by higher rates of medication, and that segregating GP and SP would improve the growth and survival of both groups. All progeny born to 109 gilts (parity 1) and 94 sows (parities 2 to 8) were allocated to 4 postweaning treatments at birth: GP separately penned, GP mixed with SP in a common pen (GM), SP separately penned, and SP mixed with GP in a common pen (SM), with littermates split among treatments. The GM and SM pigs were penned together after weaning. Individual live weight of all progeny was recorded at birth (birth weight [BWT]), weaning (28 d; weaning weight [WWT]), 10 wk of age (10-wk weight [10WT]), and sale (22-23 wk; sale weight [SWT]). Individual HCW, backfat depth, loin depth, and dressing percentage were measured at slaughter. All postweaning mortalities and medications were recorded. The GP had a lighter BWT ( = 0.032), WWT ( < 0.001), 10WT ( < 0.001), and SWT ( < 0.001) than SP as well as a lower HCW ( < 0.001) and dressing percentage ( = 0.012). Postweaning performance differences were mostly attributable to the lighter WWT of GP compared with that of SP when WWT was fitted as a covariate. The GP had a higher mortality in the immediate postweaning period (weaning to 10 wk of age; = 0.028) and from weaning to sale ( = 0.012) than SP, which was also attributable to lower WWT. The GP exhibited a higher incidence of mortality ( = 0.011) due to respiratory tract infection in the grower-finisher period, despite similar medication rates ( = 0.83). Segregation of GP and SP between pens presented no benefit in terms of growth and survival of both groups while requiring added labor and production considerations and, therefore, is not recommended. This study confirms that GP are lighter than SP, on average, at every stage of life from birth to slaughter and that their performance before weaning is an important determinant for whole-of-life performance.

Investigating the reproductive performance of gilt progeny entering the breeding herd

Objective: To quantify the performance of gilt progeny in the F1 breeding herd at a large swine farm in New South Wales, Australia (Rivalea Australia Pty Ltd). `Materials and methods: Performance data on all gilts selected for entrance to the commercial breeding herd from January 2014 until December 2015 were included in this study. Comparisons were made between gilt and sow progeny in terms of the proportion of animals to reach first breeding, performance to parity 4, and longevity to parity 3. Results: Gilt progeny were lighter than sow progeny at each live weight measurement (P &lt; .001), and had a higher P2 backfat level at selection than sow progeny (P = .02) at the same live weight. Gilt progeny selected into the breeding herd reached first breeding before 220 days of age less often than sow progeny (P &lt; .001) and were 1 day older at first breeding (P = .003). Sow progeny had a lower farrowing rate from this breeding (P &lt; .001). After the first breeding, there were few differences in performance indices between groups for the first four parities. There were no statistically significant differences between the groups in terms of longevity indices. Implications: Fewer gilt progeny may be selected to enter the breeding herd; however, after farrowing their first litter, selected gilt progeny perform just as well as sow progeny. While it is recommended to continue to include gilt progeny in the replacement-gilt selection process, further research in this field is recommended.

Pre-weaning growth of gilt and sow progeny is not improved by feeding conjugated linoleic acid and medium chain fatty acids during gestation

Pre-weaning growth of gilt and sow progeny is not improved by feeding conjugated linoleic acid and medium chain fatty acids during gestation

Dietary fatty acids affect the growth, body composition and performance of post-weaning gilt progeny

Gilt progeny are born lighter, have lower weaning weights and require more medication throughout their life time than do sow progeny. Therefore, strategies to improve their post-weaning performance are of importance to pork producers. Dietary fatty acids have been shown to be potent modulators of physiological processes. Studies in other species have reported that dietary fatty acids affect in utero development, cognitive behaviour, immune system function, carcass composition as well as feed efficiency of offspring. However, little information is available that details their use in gilt progeny and when fed throughout their lifetime. In the present study, two experiments were conducted to investigate the effects of feeding three different types of fat to gilts and their progeny on the growth, body composition and performance post-weaning. Diets were enriched with either saturated fatty acids (SFA; tallow), or n-3 (fish-oil extracts) or n-6 (safflower oil) polyunsaturated fatty acids (PUFA) and were fed to gilts through gestation and to their progeny post-weaning. In Experiment 2, half of the female progeny from n-3 and n-6 PUFA litters were fed SFA post-weaning. For both studies, there was no significant difference in weaning bodyweights. However, in Experiment 1, pigs fed n-6 PUFA diets post-weaning were significantly lighter 7 days post-weaning than were pigs fed SFA- and n-3 PUFA-enriched diets. Despite feed intake of n-6 PUFA-fed pigs becoming comparable to that of the other groups during the finisher period, bodyweight for this group remained significantly lower than that of the other groups at the conclusion of the experiment. No effect of dietary fatty acid type on the carcass composition of finisher pigs, as determined by computed tomography, was found. The results of Experiment 2 showed that feeding pigs n-6 PUFA diets post-weaning through to slaughter significantly compromised their growth, being in agreement with those from Experiment 1. Feed consumption for this group was significantly less during the post-weaning and the finisher periods. However, pigs from n-6 PUFA litters that were fed SFA diets post-weaning showed no compromise in growth and performance and were comparable to pigs from the other treatment groups. During the grower and finisher periods, pigs fed n-6 PUFA diets had a significantly higher rate of mortality that was as much as 13 times that of pigs fed SFA diets. Pigs from n-6 PUFA litters that were fed SFA diets post-weaning were not affected in this manner. The results of the current study showed that feeding diets enriched with n-6 PUFA to pigs significantly compromised their growth and performance and that this fatty acid type may also have negative health effects with prolonged consumption. The data suggested that the type of fatty acid used in pig diets may be an important consideration for nutritionists when formulating diets to optimise post-weaning growth and performance.

Piglet performance and immunity is determined by the parity of both the birth dam and the rearing dam

Gilt progeny have lower weaning weights and higher post-weaning medication and mortality rates, indicating greater disease susceptibility, than do sow progeny. The present study aimed to identify explanatory innate or adaptive immunity differences between gilt and sow progeny and potential pre- or post-natal influences. Sixty-four dams were vaccinated twice pre-farrowing with tetanus toxoid (TT). Serum (pre-vaccination) and colostrum and/or milk samples were collected to determine concentrations of TT-specific immunoglobulin G (IgG), by using an enzyme-linked immunosorbent assay (ELISA). Piglets were removed from their birth dam before suckling and fostered (not to their birth dam) to form 16 gilt and 16 sow litters, with five gilt-born and five sow-born piglets per litter. Piglets were vaccinated at weaning (4 weeks old) with either TT or saline (control). Sera and whole blood were collected from three gilt-born and three sow-born piglets per litter at 2, 4 and 7 weeks of age. Innate immunity was assessed indirectly on whole blood using an interferon gamma (IFN-γ) immune cell stimulation assay and a phagocytic assay. Piglets were weighed at birth, 4, 10, 17 and 22 weeks of age. There was no difference (P &gt; 0.05) in the concentration of TT-specific IgG in colostrum and milk from gilts and older-parity sows, suggesting a similar ability to transfer IgG antibodies to a novel antigen. Birth dam parity did not affect piglets’ TT-specific IgG concentrations pre-weaning (P &gt; 0.05) suggesting similar ability to absorb passively acquired IgG. Sow-reared piglets, however, had lower (P &lt; 0.05) concentrations of TT-specific IgG than did gilt-reared piglets, possibly due to haemodilution in the faster-growing sow progeny. Gilt-born progeny had a reduced IgG response post-weaning to TT vaccination relative to sow-born progeny (P &lt; 0.05), indicating adaptive immunity differences. Birth dam parity did not affect (P &gt; 0.05) innate immunity (number/responsiveness of cells). Rearing dam parity influenced phagocytic activity pre- and post-weaning (gilt-reared &gt; sow-reared; P &lt; 0.05), possibly due to increased pathogen challenge. Birthweight was affected by birth dam parity (sow-born &gt; gilt-born; P &lt; 0.05) while rearing dam parity determined weaning weight (sow-reared &gt; gilt-reared; P &lt; 0.05), with no difference evident at 22 weeks. The results of the present study suggest that gilt-born progeny may be more susceptible to disease post-weaning than sow-born progeny due to their lower birthweight and reduced humoral immune responsiveness. The rearing dam may also affect disease susceptibility in progeny due to slower pre-weaning growth, lower weaning weights and increased pathogen challenge, both pre- and post-weaning.

Providing supplemental milk to piglets preweaning improves the growth but not survival of gilt progeny compared with sow progeny1

Gilt progeny have lighter weaning weights and greater postweaning medication and mortality rates compared with the progeny of older parity sows. Because weaning weight has been positively correlated with postweaning survival, this study aimed to determine whether the provision of supplemental milk preweaning could improve weaning weight and subsequent weights as well as postweaning survival of gilt progeny. The study was replicated in summer and winter as the effects of supplemental milk were expected to vary with season. The progeny of 80 gilts (parity 0) and 80 sows (parity 2 to 5) were allocated to both treatments: with or without supplemental milk in these 2 seasons with 5 sheds/season. Litter size was standardized (10 to 11 piglets) and each piglet was weighed at birth, d 21, weaning (4 wk), and 10 wk of age. Medications and mortalities were recorded both preweaning and postweaning. Pigs were housed within treatment groups postweaning, and ADFI and G:F were measured. Gilt progeny were 200 g lighter at birth in both replicates (P < 0.001) and were 500 g lighter at weaning in the winter replicate (P < 0.05) compared with sow progeny. The provision of supplemental milk improved weaning weight for both gilt and sow progeny by 800 g in summer (P < 0.05) and by 350 g in winter (P < 0.05). This improvement in weaning weight had no effect on the incidence of death or disease in milk-supplemented progeny of either gilts or sows (P > 0.05). Supplemental milk disappearance (the daily difference between the volume of milk provided and the residue left in the drinker) was greater in summer than winter (by 130 mL/piglet d(-1); P < 0.05) as were the associated weaning weight benefits. The weaning weights of supplemented gilt progeny reached or exceeded that of nonsupplemented sow progeny. Gilt progeny had greater postweaning mortality (2.6%) and medication rates (6.2%) than sow progeny (1 and 2.2%, respectively; both P < 0.05) in both seasons, but medication rates were greater in winter (7.2%) for both treatment groups than in summer (1.9%; P < 0.05). Gilt progeny also had less postweaning ADFI than sow progeny in winter (528 and 636 g, respectively; P < 0.05) with no dam parity effect on G:F (both P > 0.05). The hypothesis that supplemental milk provision did increase gilt progeny weaning weight was supported (especially in summer) but the supplementation had no effect on postweaning weights and survival. Efforts to improve gilt progeny postweaning growth and survival need to be aimed at improving health and immunity, not just weaning weight.

Maternal low-dose porcine somatotropin treatment in late gestation increases progeny weight at birth and weaning in sows, but not in gilts1

Birth weight positively predicts postnatal growth and performance in pigs and can be increased by sustained maternal porcine ST (pST) treatment from d 25 to 100 of pregnancy (term ∼115 d). The objective of this study was to test whether a shorter period of maternal pST treatment in late pregnancy (d 75 to 100) could also increase birth and weaning weights of progeny under commercial conditions. Gilts (parity 0) and sows (parities 2 and 3) were not injected (controls) or injected daily with pST (gilts: 2.5 mg•d(-1), sows: 4.0 mg•d(-1), both ∼13 to 14 μg•kg(-1)•d(-1)) from d 75 to 100 of pregnancy. Litter size and BW were recorded at birth and weaning, and dams were followed through the subsequent mating and pregnancy. Maternal pST injections from d 75 to 100 increased litter average progeny weight at birth (+96 g, P = 0.034) and weaning (+430 g, P = 0.038) in sows, but had no effect on progeny weight in gilts (each P > 0.5). Maternal pST treatment did not affect numbers of live-born piglets and increased numbers of stillborn piglets in sows only (+0.4 pigs/litter, P = 0.034). Maternal pST treatment did not affect subsequent reproduction of dams. Together with our previous data, these results suggest that sustained increases in maternal pST are required to increase fetal and postnatal growth in gilt progeny, but that increasing maternal pST in late pregnancy may only be an effective strategy to increase fetal and possibly postnatal growth in sow progeny.