Expression profiling of IGFs and IGF receptors in piglets with intrauterine growth restriction

Posted in: Production by admin on July 26, 2011 | No Comments

Intrauterine growth restriction (IUGR), defined as impaired growth and development of the mammalian fetus or its organs during pregnancy because of inadequate food intake, disease, environmental stress, or the dysfunction of the placenta, endometrium, or uterus is a major problem in human medicine and animal production. In order to test the hypothesis that expression levels of insulin-like growth factor system is altered in piglets with IUGR, the present study was conducted to compare the expression levels of IGF-I, IGF-II, IGFR1, IGFR2 and IGFBP5 in m. longissimus, liver and kidney in 21-day-old IUGR piglets with normal birth weight (NBW) piglets. Our results showed that the expression level of insulin-like growth factor 1 was significantly lower in m. longissimus, liver and kidney of the IUGR piglets compared with the NBW piglets. However, there were no differences in the expression levels of IGF2, IGF1R, IGF2R and IGFBP5 in all tissues tested between NBW and IUGR piglets.In the previous studies, higher levels of liver or serum IGF-I, IGF-II, IGFBP2 and IGFBP3 were observed in spontaneously arising IUGR fetal piglets. This demonstrates that the expression level is different in insulin-like growth factor system genes between IUGR fetal pigs and piglets of 21 days. Our results suggested that it is possible to cure or prevent IUGR in piglets through injection of IGF1.

For more information the full article can be found at http://www.journals.elsevierhealth.com/periodicals/livsci

Group housing of sows in early pregnancy: A review of success and risk factors

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A recent telephone survey of 735 Dutch farmers with group housing of sows in early pregnancy suggested a wide variation in reproductive success, irrespective of husbandry system. The reason for these differences between farms is not known, but of great importance to the pig industry which is moving worldwide from individual to group housing systems, mainly for animal welfare reasons. Therefore, the aim of this review is to list the most likely success and risk factors for group housing of sows in early pregnancy, in relation to reproduction (such as pregnancy rate) and animal welfare (such as aggression and health). The review first considers a limited number of group housing comparisons and finds that the results of the few studies performed are not very conclusive, neither on fertility nor on leg problems, longevity and welfare of sows. As a consequence, it is hard to draw any significant practical conclusions, and the review proceeds to look at studies in which single factors were addressed. For the effects on fertility it is concluded that especially factors causing chronic stress (e.g. due to unfavourable social, management or climatic conditions) and a low feed intake may impact reproductive performance. The vulnerable period lies in weeks 2 and 3 of pregnancy. On leg problems and longevity an important factor seems to be the quality of the floor, regardless of other aspects of the housing system. The use of straw seems to be advantageous. Finally, on aggression it is argued that this will never be eliminated from systems in which sows are housed as a group. However, it can be properly managed and key factors in this are a gradual familiarisation of unfamiliar animals, sufficient space and pen structure during initial mixing, minimizing opportunities for dominant sows to steal food from subordinates, the provision of a good quality floor and the use of straw bedding. The review concludes with a series of practical recommendations to improve welfare and reproduction in group housed sows.

For more information the full article can be found at http://www.journals.elsevierhealth.com/periodicals/livsci

Obstetric and fetal outcomes in dystocic and eutocic sows to an injection of exogenous oxytocin during farrowing

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Sixty hybrid Yorkshire-Landrace penned sows, 30 with eutocic farrowing and 30 experiencing a dystocic parturition, were studied to evaluate the obstetric and neonatal outcomes to low doses of oxytocin administered at advanced stages of parturition. Animals in each group were randomly subdivided into 2 subgroups: 15 eutocic and 15 dystocic sows received oxytocin 0.083 IU/kg (equivalent to 1 IU/12 kg body weight), administered intramuscularly after the delivery of the 5th piglet; the other 15 eutocic and 15 dystocic sows received saline solution intramuscularly at the same time. Oxytocin decreased the number of intrapartum deaths by approximately 50% (P = 0.002). No piglet was born dead from the saline- and oxytocin-treated eutocic sows. The highest viability score was observed among piglets born to eutocic sows treated with oxytocin. In summary, this dose schedule would help to decrease the number of stillbirths in both eutocic and dystocic farrowing sows.

Management factors associated with farrowing rate in commercial sow herds in Ontario

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The objectives of this study were to determine associations between low farrowing rate and various management factors in sow herds. In 30 sow herds, a management survey, breeding observations, semen evaluation, and semen storage temperature monitoring were completed. Herds with an average farrowing rate of, 85% were classified as low farrowing rate herds while those with an average farrowing rate of $ 85% were classified as good farrowing rate herds. Low farrowing rate herds were more likely than good farrowing rate herds to move boars into gilt pens for estrus detection, breed a high proportion of sows by artificial insemination (AI) only, start heat detection 3 d post-weaning, wipe the vulva prior to breeding, and use “hands-free” AI devices.

Results from six generations of selection for intramuscular fat in Duroc swine using real-time ultrasound. I. Direct and correlated phenotypic responses to selection

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A study was conducted to evaluate the efficacy of selection for intramuscular fat (IMF) in a population of purebred Duroc swine using real-time ultrasound. Forty gilts were purchased from US breeders and randomly mated for 2 generations to boars available in regional boar studs, resulting in a base population of 56 litters. Littermate pairs of gilts from this population were randomly assigned to a select line (SL) or control line (CL) and mated to the same sire to establish genetic ties between lines. At an average BW of 114 kg, a minimum of 4 longitudinal ultrasound images were collected 7 cm off-midline across the 10th to 13th ribs of all pigs for the prediction of IMF (UIMF). At least 1 barrow or gilt was slaughtered from each litter, and carcass data were collected. A sample of the LM from the 10th to 11th rib interface was analyzed for carcass IMF (CIMF). Breeding values for IMF were estimated by fitting a 2-trait (UIMF and CIMF) animal model in MATVEC. In the SL, selection in each subsequent generation was based on EBV for IMF with the top 10 boars and top 75 gilts used to produce the next generation. One boar from each sire family and 50 to 60 gilts representing all sire families were randomly selected to maintain the CL. Through 6 generations of selection, an 88% improvement in IMF has been realized (4.53% in SL vs. 2.41% in CL). Results of this study revealed no significant correlated responses in measures of growth performance. However, 6 generations of selection for IMF have yielded correlated effects of decreased loin muscle area and increased backfat. Additionally, the SL obtained more desirable objective measures of tenderness and sensory evaluations of flavor and off-flavor. Meat quality characteristics of pH, water holding capacity, and percent cooking loss were not significantly affected by selection for IMF. Selection for IMF using real-time ultrasound is effective but may be associated with genetic ramifications for carcass composition traits. Intramuscular fat may be used in purebred Duroc swine breeding programs as an indicator trait for sensory traits that influence consumer acceptance; however, rapid improvement should not be expected when simultaneous improvement in other trait categories is also pursued. 

For more information the full article can be found at http://jas.fass.org/

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. 

For more information the full article can be found at http://jas.fass.org/

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. 

For more information the full article can be found at http://jas.fass.org/

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. 

For more information the full article can be found at http://jas.fass.org/

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. 

For more information the full article can be found at http://jas.fass.org/