Type of accommodation during gestation affects growth performance and reproductive characteristics of gilt offspring

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The objective was to determine effects of the type of gestation accommodation to which dams were exposed on growth performance and age at puberty in gilt offspring. Yorkshire × Landrace gilts (n = 81; 26.9kg of BW) were placed in pens of 3 gilts each. Each pen contained gilts farrowed exclusively by gilts exposed to 1 of 3 gestation accommodations: individual crates throughout gestation; group pens throughout gestation; or crates for 30 d postmating and then group pens for the remainder of gestation (n = 9 pens/group). Performance during the 5-wk nursery period was similar among groups. The grow-finish period ended at a BW of 108.9kg, and ADG (0.98kg) was not affected by treatment. However, pig BW was affected by accommodation type × time, with gilts farrowed by females housed in crates throughout gestation being heaviest during the last 4 wk. There was no effect of treatment on ADFI (2.61kg); however, G:F was enhanced in gilts farrowed by females housed in crates throughout or for the first 30 d of gestation and then groups compared with gilts from females kept in groups throughout gestation. Gilts from females gestated in crates throughout gestation tended to have less backfat than gilts from females gestated in groups. After grow-finish, gilts were checked for estrus once daily. Mean age at puberty did not differ among groups however, fewer gilts farrowed by females gestated in crates throughout gestation reached puberty by 165 d of age (13%) compared with the other 2 groups (44%). Although specific mechanisms need to be determined, we suggest that the type of gestation accommodation in which gilts are kept may affect production performance of gilt offspring, possibly by fetal programming.

Factors associated with sow stayability in 6 genotypes

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The purpose of this study was to determine the association of production factors with stayability to parity 4 (STAY4) under controlled experimental conditions. Data were from 2,293 female pigs, sampled from 6 genetic lines that were entered into the National Pork Producers Council Maternal Line National Genetic Evaluation Program. Genetic lines evaluated included Newsham (NH), National Swine Registry (NSR), American Diamond Swine Genetics (ADSG), Danbred (DAN), and 2 Dekalb-Monsanto lines (DK44 and GPK347). Stepwise logistic regression was utilized in the analysis of STAY4. All effects were nested within genetic line. Categorical effects in the model were arrival date to the wean-to-finish unit (entry date) and breed-gestation-farrowing facility (farm). Continuous effects in the model were gilt backfat, LM depth, ADG, age at puberty, age at first farrowing, and traits recorded before the last litter of the sow (prefarrow backfat, number born alive, number weaned, litter weaning weight, lactation feed intake, lactation backfat loss, and lactation length). Factors significant for STAY4 included farm, entry date, age at first farrowing, ADG, gilt backfat, and lactation before removal effects, as well as feed intake, number born alive, and lactation length. Age at first farrowing and lactation feed intake affected all genetic lines. Regression coefficients for STAY4 on age at first farrowing were −0.014, −0.022, −0.017, −0.016, −0.011, and −0.021, respectively, for NH, NSR, ADSG, DK44, GPK347, and DAN genetic lines. Regression coefficients for STAY4 on lactation feed intake were 0.043, 0.049, 0.051, 0.061, 0.120, and 0.097, respectively, for NH, NSR, ADSG, DK44, GPK347, and DAN females. Age at puberty, age at first farrowing, and lactation feed intake had the greatest effect on STAY4. 

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Estimates of variance components for genetic correlations among swine estrus traits

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Variance components and genetic correlations were estimated among estrus, puberty, growth, and composition traits in Landrace-Large White gilts (n = 1,225; Genetic Improvement Services) from 59 sires and 330 dams. Four groups of gilts entered the North Carolina Swine Evaluation Station in Clayton at an average age of 162 d and were checked daily for estrus. Once 70% of gilts had reached puberty, recording of estrus symptoms occurred every 12 h for 30 d, using fence-line boar contact. Subjective estrus traits were maximum strength of standing reflex with or without a boar present, total strength of standing reflex with or without a boar present, and strength of vulva reddening and swelling. Objective estrus traits consisted of vulva redness, vulva width, length of estrus in consecutive days based on 12-h observations, and age at puberty (AGEPUB). Growth and composition traits included puberty weight, days to 114 kg (DYS), 10th-rib backfat, and 10th-rib LM area at 114 kg (BF, LMA) and puberty. Variance components were estimated using AIREMLF90 with an animal model. All models included gilt development diet class and breed composition as fixed effects, entry age as a covariate (except DYS, BF, and LMA), a random common litter effect, and a random animal genetic effect. Heritability estimates for length of estrus, maximum strength of the standing reflex with a boar, total strength of the standing reflex with a boar, maximum strength of the standing reflex without a boar, total strength of the standing reflex without a boar, vulva redness, strength of vulva reddening and swelling, and vulva width were 0.21, 0.13, 0.26, 0.42, 0.42, 0.26, 0.45, and 0.58, respectively. Heritability estimates for AGEPUB, puberty weight, 10th-rib backfat at puberty, 10th-rib LM area at puberty, DYS, BF, and LMA were 0.29, 0.39, 0.41, 0.38, 0.24, 0.47, and 0.39, respectfully. Common litter effect estimates ranged from 0.01 to 0.09. The estimated genetic correlation between length of estrus and maximum strength of standing reflex with a boar was 0.99. Genetic correlations between AGEPUB and length of estrus, maximum strength of standing reflex with a boar, and vulva redness were −0.23, −0.32, and 0.20, respectively. Length of estrus had positive genetic associations with DYS and BF (0.30 and 0.29, respectively). It was concluded that past selection for lean BW gain may have weakened the strength of the standing reflex and that sufficient genetic variation exists to make selection for improved swine estrus traits effective. 

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The effect of gilt age at first estrus and breeding on third estrus on sow body weight changes and long-term reproductive performance

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The objective of this trial was to determine the effect of age at first estrus on BW changes and long-term reproductive performance of sows. At approximately 100 d of age, prepubertal C22 gilts (n = 431) were allocated to trial. At a pen average of 140 d of age, gilts began daily direct contact with mature boars to stimulate onset of puberty. Gilts (n = 317, 73%) were recorded as cyclic by 180 d of age (select) and were classified on the basis of age at puberty into 3 puberty groups: early puberty (EP; <153 d of age; n = 85); intermediate puberty (IP; 154 to 167 d of age; n = 140); or late puberty (LP; 168 to 180 d of age; n = 90). Gilts not exhibiting the standing reflex by 180 d of age were considered nonselect (NS; n = 91). Mean day to puberty and age at puberty attainment in each of the classifications were EP: 9.6d and 147.4d; IP: 19.3d and 159.9d; LP: 33.8 and 175.7d, respectively. Fewer NS gilts (73.0%) were bred than were EP (97.7%), IP (93.2%), or LP (93.0%) gilts. Total number of piglets born and born alive were not different between classifications and increased over successive parities in EP, IP, and NS gilts. For gilts initially served, there was no effect of puberty group classification on retention in the herd to farrow a third litter, but the rate of fallout per parity tended to be greatest for NS (17.2%) compared with EP (12.4%), IP (15.6%), and LP (14.2%) gilts. Taken together, these data suggest that the response to a standardized protocol of boar stimulation can identify 50 to 75% of gilts that will have greatest lifetime productivity in the breeding herd. In the known cyclic (select) gilts, BW increased over the productive life of the sow, and EP gilts were lighter than LP gilts at every measured event. Plasma IGF-1 only differed between puberty groups at d 100 of age (EP: 169.0; IP: 157.2; LP: 144.0ng/mL), suggesting a mechanism linking IGF-1 status and age at puberty in the present study. 

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Effect of excessive, hormonally induced intrauterine crowding in the gilt on fetal development on day 40 of pregnancy

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Selection for litter size may result in an increase in uterine crowding due to a faster increase in ovulation rate than in litter size. Increased ovulation rate does not result in a proportionally increased number of piglets born alive. In this study, the effect of ovulation rate on vitality characteristics of fetal-placental units at d 40 of pregnancy was investigated. For this, 43 Large White gilts were treated with hormones to induce superovulation. Average ovulation rate was 45.16; average number of vital fetuses at d 40 of pregnancy was 17.09 that weighed an average of 11.26g; their placenta weighed on average 31.88g; and they occupied 11.69cm of the uterus. Loss in oocytes (i.e., that did not result in a vital fetus at d 40) increased with increasing ovulation rate and occurred before and after implantation. With respect to the vital fetuses, increased ovulation rate resulted in decreased fetal and placental weight and decreased length of the area in the uterus that was occupied by the placenta. Strong correlations existed between placental and fetal weight, and placental weight and length. Fetal-placental characteristics were weakly correlated to distance to the implantation sites of neighboring fetuses, a measure of crowdedness with fetal weight to 0.16. Increased ovulation rates, but more specifically increased late mortality rates, have negative effects on the remaining vital fetuses with respect to the fetal and placental weight and length of the implantation site. The most extreme effect was on placental weight, in which a uterus with <10 cases of late mortality was on average 25% greater than placental weight in a uterus with >18 cases of late mortality. Furthermore, increased ovulation rates resulted in decreased within litter variation for fetal and placental weight. At increased ovulation rates, the number of live fetuses remained similar, but placental development is impaired and the growth of the fetus is retarded compared with reduced ovulation rate, with effects likely lasting into adult life. 

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The effect of ractopamine hydrochloride on gene expression in adipose tissues of finishing pigs

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The long-term effect of feeding the catecholamine analog ractopamine (RAC; ractopamine hydrochloride, Elanco Animal Health, Indianapolis, IN) on the expression of genes involved in energy and lipid metabolism in subcutaneous adipose tissue was studied. Large White pigs (84 kg) were fed corn- and soybean meal-based diets supplemented with 0, 20, or 60 mg/kg of RAC for 14, 28, or 42 d. Expression (mRNA abundance) in adipose tissue of sterol regulatory binding protein-1 (SREBP-1), PPARα, PPARγ2, fatty acid synthase (FAS), glucose transporter 4 (GLUT4), and stearoyl-CoA desaturase was determined by Northern blotting. Feed intakes did not differ, and RAC (20 and 60 mg/kg) improved BW gain at d 14, 28, and 42 and increased loin eye area (measured on d 42 only). Expression of SREBP-1 and PPARγ2 declined with RAC by d 28 and 42, whereas expression of PPARα was increased on d 14, 28, and 42. After 14 d, expression of FAS and GLUT4 was decreased with 60 mg/kg of RAC, whereas both RAC concentrations attenuated FAS expression on d 28 and 42. Overall, adipose tissue stearoyl-CoA desaturase expression was not affected by RAC but showed somewhat less expression on d 28 at 60 mg/kg of RAC. Although prolonged, chronic RAC feeding most likely down-regulates adipose tissue membrane β-adrenergic receptors, mRNA abundances of anabolic lipid metabolism transcription factors, glucose transporters, and enzymes (SREBP-1, PPARγ2, FAS, GLUT4) were still attenuated up to d 42. Conversely, a transcription factor related to oxidative metabolism expression (PPARα) was enhanced. We conclude that even after 42 d, RAC still decreased expression of lipogenic genes in adipose tissue by yet undefined cyclic adenosine monophosphate-directed mechanisms, but in contemporary lean pigs, this effect is likely of limited practical significance. 

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Developmental factors that influence sow longevity

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The length of adult sow life is now recognized as both an economic and a welfare concern. However, there are no consistent definitions to measure sow longevity. This study assessed 6 different descriptions of longevity and determined their relationship with developmental performance factors. Longevity definitions included stayability (probability of a sow producing 40 pigs or probability of her reaching 4 parities), lifespan (number of parities a female has accumulated before culling), lifetime prolificacy (number of pigs born alive during the productive lifetime of a female), herd life (time from first farrowing to culling), and pigs produced per day of life. Data consisted of 14,262 records of Yorkshire females from both nucleus and multiplication herds across 21 farms from 4 seedstock systems. Within a subset of the data, information was available on the litter birth record of the female and her growth and composition data. Therefore, data were subdivided into 2 data sets, consisting of data A (data from the farrowing records of a female) and data B (data A and information from the litter birth record of a female and the growth and backfat data from a female). A Cox proportional hazards model was used to determine the relationship of developmental factors and first farrowing record with longevity. Those factors that were significantly associated with longevity, regardless of definition, were age at first farrowing, litter size at first farrowing and last farrowing, number of stillborn in the first litter, adjusted 21-d litter weight of the first litter, herd type, backfat, and growth. Within a contemporary group, fatter, slower growing gilts had a decreased risk of being culled. Additionally, sows that had more pigs born alive, fewer stillborn pigs, and heavier litters at 21 d of lactation in their first litter had a decreased risk of being culled. Furthermore, sows from nucleus herds experienced a greater risk of being culled. Many factors affected longevity, regardless of definition. Pork producers can implement management protocols that can extend the productive life of breeding females, resulting in improved profitability and animal welfare. 

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Growth performance and gastrointestinal microbial ecology responses of piglets receiving Saccharomyces cerevisiae fermentation products after an oral challenge with Escherichia coli (K88)

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The effects of Saccharomyces cerevisiae fermentation products (YFP) on growth performance and gastrointestinal (GIT) microbial ecology in 90 weanling pigs orally challenged with Escherichia coli K88+ (ETEC) were investigated. The YFP were an original YFP product (XPC) and a water-suspendable yeast fermentation prototype (WSYFP) from a commercial company. Treatments consisted of a negative control (NC, no in-feed or in-water additive), carbadox (AB, 55 mg of carbadox/kg of feed), XPC (in feed, 0.2%), and WSYFP (in water, 0.5, 1, or 2 g/pig per day), and each was allotted to 5 pens (3 pigs/pen). The diets met the 1998 NRC specifications. Pigs were acclimated to treatments for a 7-d period before an ETEC challenge. On d 8, blood was collected from pigs to determine the baseline packed cell volume (PCV) measurement, and pigs were orally challenged with ETEC. At various time points postchallenge, blood samples were taken, performance measures and fecal consistency scores were recorded, and gut digesta and tissue samples were taken to evaluate GIT morphology, microbial ecology, and metabolites. Preplanned contrasts were used for comparison. Pigs receiving YFP had greater ADFI than NC pigs on d 3 (424 vs. 378 g/d) and d 7 (506 vs. 458 g/d) postchallenge. This effect of YFP on ADFI was similar to that of AB on d 3, but pigs receiving AB ate more (576 vs. 506 g/d) at d 7 than pigs receiving YFP. Pigs exhibited reduced PCV upon ETEC challenge; however, pigs receiving additives sustained a greater PCV at 72 h compared with the NC group. Compared with the NC pigs, pigs receiving YFP showed a smaller number of ileal mucosa adherent ETEC and prevalence of the order Enterobacteriales in the ileal digesta, which corresponded to less (5.09 vs. 6.97 mg/ dL) colonic ammonia on d 7 post-challenge. Most of the indices for ileal digesta bacterial richness and diversity were greater for YFP pigs compared with NC pigs. However, results also indicated that the influence of YFP on the piglet intestinal microenvironment might differ when given in feed or water during ETEC challenge. In conclusion, pigs receiving YFP showed a better appetite in the presence of ETEC, which, together with the greater ileal digesta bacteria richness and diversity and decreased ETEC adhering to the mucosa and reduced colonic ammonia, indicates a healthier GIT environment. 

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Phenotypic and genetic correlations between gilt estrus, puberty, growth, composition, and structural conformation traits with first-litter reproductive measures

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The objective was to estimate correlations of gilt estrus, puberty, growth, composition, and structural conformation traits with first-litter reproductive measures. Four groups of gilts (n = 1,225; Genetic Improvement Services of NC) entered the NC Swine Evaluation Station averaging 162 d of age and were observed daily for symptoms of estrus. Once symptoms of first estrus were observed in 70% of gilts, recording of symptoms of estrus in all gilts occurred every 12 h for 30 d, utilizing fence-line boar contact. Subjective estrous traits were maximum and total strength of standing reflex, as observed with and without the presence of a boar, and strength of vulva reddening and swelling. Objective estrous traits consisted of vulva redness, vulva width, length of estrus, and age at puberty. Growth and composition traits included BW at puberty, days to 114 kg, and 10th rib backfat and LM area at 114 kg and at puberty. Subjective structural conformation traits were muscle mass, rib width, front leg side view, rear leg side view, front legs front view, rear legs rear view, and locomotion. First-litter sow traits included if gilt farrowed (Stay), age at first farrowing (AFF), total number of piglets born (TNB), and weaning to conception interval (WCI). Variance components were estimated using an animal model with AIREMLF90 for linear traits and THRGIBBS1F90 for categorical traits. Heritability estimates for Stay, AFF, and TNB were 0.14, 0.22, and 0.02, respectively. Genetic correlations between length of estrus, the standing reflex traits, and age at puberty with Stay were 0.34, 0.34 to 0.74, and −0.27, respectively, and with AFF were −0.11, −0.04 to −0.41, and 0.76, respectively. Days to 114 kg had genetic associations with Stay, AFF, and TNB of 0.52, −0.25, and −0.08, respectively. Backfat at 114 kg had genetic correlations with Stay, AFF, and TNB of −0.29, 0.14, and 0.47, respectively. Vulva redness and TNB were negatively correlated phenotypically and genetically. Associations between structural conformation traits with Stay, AFF, TNB, and WCI were generally low to moderate and favorable. Selection for longer length of estrus, stronger standing reflex, or younger age at puberty would increase the proportion of gilts that farrow and reduce age at first farrowing. 

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Muscle characteristics and meat quality traits are affected by divergent selection on residual feed intake in pigs

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Residual feed intake (RFI) is defined as the difference between the observed feed intake and that expected based on requirements for maintenance and production. A divergent selection was conducted during 4 generations in Large White male pigs to produce low and high RFI lines. The present study aims at determining the influence of this selection on biochemical and histological traits of skeletal muscle, and relating these changes to correlated effects on growth, carcass composition, and meat quality traits. At 8 d preslaughter, biopsies from the LM were taken in the fed state on 14 females from each RFI line fed ad libitum. Animals were slaughtered at 107.8 +/- 8.0 kg of BW without any previous fasting. Samples of LM, semimembranosus (SM), biceps femoris (BFM), and rhomboideus muscles were taken at both 30 min and 24 h postmortem. Myofiber typing was only assessed in LM. Low RFI pigs (“efficient”) had leaner carcasses with greater muscle content, less backfat thickness, and less intramuscular fat content in all 4 muscles. Their greater muscle content was associated with hypertrophy of all fast-twitch fibers. Glycogen content in all glycolytic muscles (i.e., LM, SM and BFM), was greater in low than high RFI pigs. The greater accumulation of glycogen in LM of low RFI pigs was specifically located in the fast-twitch glycolytic IIBW fibers, which correspond to fibers containing IIb, IIb + IIx, or IIx myosin heavy chains. The difference in muscle glycogen content between RFI line pigs was more significant in the living animals than at 30 min postmortem. This was associated with a decreased ultimate pH, and greater lightness of color and drip loss in LM of low than high RFI line pigs, suggesting that selection for reduced RFI may impair some meat quality traits, such as water-holding capacity. Pigs from the low RFI line exhibited a greater percentage of IIBW fibers in LM and tended to have less lipid β-oxidative capacity in LM, SM, and BFM. In contrast, no difference between lines was found for citrate synthase and lactate dehydrogenase activities, mitochondrial activity, and expression of genes coding for uncoupling proteins 2 and 3. Differences between RFI pigs in plasma leptin, cortisol, and thyroid hormone concentrations are presented and discussed. In conclusion, selection for low RFI influenced muscle properties in a way favoring muscle mass, but likely impairing meat quality. 

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