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Schoos A, Muro BBD, Carnevale RF, Chantziaras I, Biebaut E, Janssens GPJ, Maes D. Relationship between piglets' survivability and farrowing kinetics in hyper-prolific sows. Porcine Health Manag 2023; 9:37. [PMID: 37641115 PMCID: PMC10464185 DOI: 10.1186/s40813-023-00332-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 07/28/2023] [Indexed: 08/31/2023] Open
Abstract
BACKGROUND Prolonged farrowing and more piglets born with low birth weight are undesirable consequences of genetic selection for increased litter size. The objective of the present observational study was to evaluate the relationship between piglets' survivability and farrowing kinetics in hyperprolific sows. A total of 58 sows of different parities and 1190 piglets were included. The entire farrowing process was monitored and the following parameters were recorded: inter-piglet birth interval, birth order, total born, live born, dead born, and mummified piglets, obstetric intervention, weight at birth and 24h, colostrum yield and intake. RESULTS The sows included in this study had on average 20.6 ± 0.6 total piglets born, of which 16.4 ± 0.6 were live born, 3.3 ± 0.4 were stillborn and 0.9 ± 0.2 were mummified piglets. The average farrowing duration and average birth interval were 411.3 ± 31.6 and 20.6 ± 1.7 min, respectively. Farrowing duration was positively associated (p < 0.05) with parity, number of stillborn and mummified piglets. Piglet mortality 24h after birth was negatively affected (p < 0.01) by birth weight and positively affected (p < 0.01) by cumulative birth interval. The last tercile of piglets born (birth order ≥ 17) had the highest (p < 0.01) inter-piglet birth interval (IPBI) (43.4 ± 4.17 min) compared to piglets born in the first (birth order between 2 and 7) (26.5 ± 3.8 min) and second (birth order between 8 and 16) terciles (21.9 ± 3.8 min). Cumulative birth interval, birth weight, occurrence of stillborn piglets and manual intervention were positively associated (p < 0.05) with IPBI. Piglet birth weight was also positively associated (p < 0.01) to individual colostrum intake. Piglets ingesting more colostrum had lower (p < 0.01) mortality from 24h after birth until weaning. Sow's parity and cumulative birth interval were positively associated with the presence of stillborn piglets (p = 0.02 and p < 0.01, respectively). CONCLUSION Reducing farrowing duration may be crucial to decrease stillbirth rate and neonatal mortality in hyperprolific sows. Moreover, special care must be provided to the lighter piglets within a litter to increase their colostrum intake and minimize piglet's mortality throughout lactation.
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Affiliation(s)
- Alexandra Schoos
- Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Bruno Bracco Donatelli Muro
- Department of Nutrition and Animal Production, School of Veterinary Medicine and Animal Sciences, University of São Paulo (USP), Campus Pirassununga, São Paulo, SP, Brazil
| | - Rafaella Fernandes Carnevale
- Department of Nutrition and Animal Production, School of Veterinary Medicine and Animal Sciences, University of São Paulo (USP), Campus Pirassununga, São Paulo, SP, Brazil
| | - Ilias Chantziaras
- Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Evelien Biebaut
- Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Geert Paul Jules Janssens
- Department of Veterinary and Biosciences, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Dominiek Maes
- Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
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Huang J, Zuo Z, Zhao H, Wang C, Li S, Liu Z, Yang Y, Jiang S. Cluster analysis and potential influencing factors of boars with different fertility. Theriogenology 2023; 199:95-105. [PMID: 36709653 DOI: 10.1016/j.theriogenology.2022.12.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 12/23/2022] [Accepted: 12/27/2022] [Indexed: 01/15/2023]
Abstract
The fertility of boars is intimately tied to the pig farm's economic benefits. This study aimed to rapidly categorize boars of different fertility and investigate the factors influencing the categorization using the production data in a large pig farm in northern China, including 11,163 semen collection records of Yorkshire boars (215), 11,163 breeding records and 8770 records of farrowing performance of Yorkshire sows (4505), as well as 4720 records of selection indices (sire line index and dam line index) for boars and sows (215 and 4505) between 2017 and 2020. The boar population was classified by two-step cluster analysis, followed by factor analysis to minimize the dimensionality of data variables and eliminate multicollinearity, and then using ordinal logistic regression model to investigate the risk variables impacting boar fertility categorization. Results showed that the two-step clustering divided the 215 boars into three subgroups: high-fertility (n = 61, 28.4%), medium-fertility (n = 127, 59.1%) and low-fertility (n = 27, 12.6%). The high-fertility boars were shown to be substantially greater than the medium-fertility or low-fertility boars (p < 0.05) in average total litter size, number of born alive, and number of healthy piglets of mated sows. Compared with low-fertility boars, the high-fertility boars were also significantly higher (p < 0.05) in the pregnancy rate and farrowing rate of mated sows. However, the three boar subgroups showed no difference (p > 0.05) in semen quality information (average sperm motility, average sperm density, and average sperm volume). Collinearity diagnosis indicated severe multicollinearity among the 20 data variables, which were reduced to 8 factor variables (factors 1-8) by factor analysis, and further collinearity diagnosis exhibited no multicollinearity among the 8 factor variables. Ordered logistic regression analysis revealed a significant and positive correlation (p < 0.05) of boar fertility with factor 2 (average total litter size, number of born alive, number of healthy piglets), factor 4 (average number of weak piglets and average weak piglet rate), factor 6 (sire line index of boars and dam line index of boars), factor 8 (pregnancy rate and farrowing rate), highlighting factor 2 as the most important factor influencing the classification of boar fertility. Our results indicate that the two-step cluster analysis can be used as a simple and effective method to screen boars with different fertility and that farm producers should pay attention to the recording of the reproductive performance of the mated sows due to its role as the risk factor for classification of boar fertility.
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Affiliation(s)
- Jian Huang
- Key Laboratory of Pig Genetics and Breeding of Ministry of Agriculture and Key Laboratory of Agricultural & Animal Genetics, Breeding and Reproduction of Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Zixi Zuo
- Key Laboratory of Pig Genetics and Breeding of Ministry of Agriculture and Key Laboratory of Agricultural & Animal Genetics, Breeding and Reproduction of Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Hucheng Zhao
- Key Laboratory of Pig Genetics and Breeding of Ministry of Agriculture and Key Laboratory of Agricultural & Animal Genetics, Breeding and Reproduction of Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Chao Wang
- Key Laboratory of Pig Genetics and Breeding of Ministry of Agriculture and Key Laboratory of Agricultural & Animal Genetics, Breeding and Reproduction of Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Shuangshuang Li
- Key Laboratory of Pig Genetics and Breeding of Ministry of Agriculture and Key Laboratory of Agricultural & Animal Genetics, Breeding and Reproduction of Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Zezhang Liu
- Key Laboratory of Pig Genetics and Breeding of Ministry of Agriculture and Key Laboratory of Agricultural & Animal Genetics, Breeding and Reproduction of Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Yuxuan Yang
- Key Laboratory of Pig Genetics and Breeding of Ministry of Agriculture and Key Laboratory of Agricultural & Animal Genetics, Breeding and Reproduction of Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Siwen Jiang
- Key Laboratory of Pig Genetics and Breeding of Ministry of Agriculture and Key Laboratory of Agricultural & Animal Genetics, Breeding and Reproduction of Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China.
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Involvement of Oxytocin and Progesterone Receptor Expression in the Etiology of Canine Uterine Inertia. Int J Mol Sci 2022; 23:ijms232113601. [DOI: 10.3390/ijms232113601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 10/29/2022] [Accepted: 11/01/2022] [Indexed: 11/09/2022] Open
Abstract
An altered oxytocin and progesterone receptor (OXTR and PGR, respectively) expression was postulated in canine uterine inertia (UI), which is the lack of functional myometrial contractions. OXTR and PGR expressions were compared in uterine tissue obtained during C-section due to primary UI (PUI; n = 12) and obstructive dystocia (OD, n = 8). In PUI, the influence of litter size was studied (small/normal/large litter: PUI-S/N/L: n = 5/4/3). Staining intensity in immunohistochemistry was scored for the longitudinal and circular myometrial layer and summarized per dog (IP-Myoscore). Mean P4 did not differ significantly between PUI (n = 9) and OD (n = 7). OXTR and PGR expressions (ratios) were significantly higher in PUI (OXTR: p = 0.0019; PGR: p = 0.0339), also for OXTR in PUI-N versus OD (p = 0.0034). A trend for a higher PGR IP-Myoscore was identified (PUI-N vs. OD, p = 0.0626) as well as an influence of litter size (lowest PGR-Myoscore in PUI-L, p = 0.0391). In conclusion, PUI was not related to higher P4, but potentially increased PGR availability compared to OD. It remains to be clarified whether OXTR is upregulated in PUI due to a counterregulatory mechanism to overcome myometrial quiescence or downregulated in OD due to physiological slow OXTR desensitization associated with an advanced duration of labor. Identified OXTR differences between myometrial layers indicate the need for further research.
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Hoai Nam N, Sukon P. Risk factors for intrapartum stillbirth in piglets born from cloprostenol-induced farrowing sows. JOURNAL OF APPLIED ANIMAL RESEARCH 2022. [DOI: 10.1080/09712119.2022.2089152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- Nguyen Hoai Nam
- Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
| | - Peerapol Sukon
- Faculty of Veterinary Medicine, Khon Kaen University, Khon Kaen, Thailand
- Research Group for Animal Health Technology, Khon Kaen University, Khon Kaen, Thailand
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Nam N, Sukon P. Incidence of dystocia at piglet level in cloprostenol-induced farrowings and associated risk factors. Arch Anim Breed 2022; 65:97-103. [PMID: 35282397 PMCID: PMC8908415 DOI: 10.5194/aab-65-97-2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 02/02/2022] [Indexed: 11/29/2022] Open
Abstract
Few studies have investigated risk factors for dystocia in swine, although this birthing abnormality can compromise welfare of both sows and piglets
by increasing stillbirth rate and decreasing sow productivity. This study aimed to determine risk factors associated with dystocia at piglet level
in cloprostenol-induced farrowings. A dystocia event was recorded when a birth interval exceeded 45 min or when manual extraction was applied. Data
were collected from 898 piglets born from 77 Landrace × Yorkshire crossbred sows, which were induced for farrowing on day 114 of
gestation. Generalized linear mixed models (GLMMs) were used to evaluate the association between dystocia and parity, gestation length, litter size,
relative birth order (RBO (%) = 100 ⋅ birth order/litter size), birth weight, crown rump length, body mass index, ponderal index,
piglet's sex, use of oxytocin, and stillbirth. Sows nested in farrowing batches were fitted as random factors in GLMMs. Incidence of dystocia at
piglet and farrowing levels was 11.0 % and 75.3 %, respectively. The final multivariate model explained 20.1 % variation of
dystocia. RBO had a quadratic effect on dystocia in which incidence of dystocia decreased from RBO ≤ 40 % to RBO = 60 %–70 %,
and then increased to the end of parturition. Piglets with birth weight > 1700 g and stillborn piglets had higher odds of dystocia in
comparison with piglets with a birth weight of 900–1700 g (OR = 2.63; 95 % CI = 1.66–4.18) and live-born piglets
(OR = 2.62; 95 % CI = 1.12–6.15), respectively. This study indicates that dystocia is very common in cloprostenol-induced farrowings
and suggests that the last one-third of parturitions is the most important stage to be supervised, and selection for homogenous litters and moderate
high birth weight may reduce the rate of dystocia.
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Affiliation(s)
- Nguyen Hoai Nam
- Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
| | - Peerapol Sukon
- Faculty of Veterinary Medicine, Khon Kaen University, Khon Kaen, Thailand
- Research Group for Animal Health Technology, Khon Kaen University, Khon Kaen, Thailand
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Nam NH, Sukon P. Risk factors associated with dystocia in swine. Vet World 2021; 14:1835-1839. [PMID: 34475706 PMCID: PMC8404131 DOI: 10.14202/vetworld.2021.1835-1839] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 06/09/2021] [Indexed: 12/02/2022] Open
Abstract
Background and Aim: Dystocia in swine can increase the stillbirth rate; however, its importance in pig-breeding systems has been underestimated. Until now, few studies have investigated dystocia and associated risk factors. Therefore, in this study, we aimed to evaluate the effects of various risk factors on dystocia in swine. Materials and Methods: Out of 5,557 piglets, we included 4,997 piglets in risk analysis study. The dependent variable was dystocia, which was recorded when a birth interval exceeded 45 min or when obstetric assistance was applied. The independent variables were parity, gestation length, litter size, birth order, gender, presence of a dead piglet, birthweight, crown rump length, body mass index, ponderal index, and oxytocin use. We used generalized linear mixed models to examine the associations between potential risk factors and dystocia at the piglet level. Results: A total of 6% of the piglets were born with a dystocia event, and 47.2% of the farrowing experienced at least one event. Dead piglets and piglets with a crown rump length of >31 cm were associated with an increased dystocia rate. This rate decreased from birth order 2 to 7, stabilized to 11, and then increased till the end of the fetal expulsion process. Conclusion: Dystocia is common in swine. Therefore, this condition should be carefully addressed by veterinarians and farrowing house personnel so that its adverse effect on welfare and productivity of sows and survivability of piglets can be reduced. Further studies investigating dystocia status and risk factors in different swine farrowing systems should be undertaken to provide more knowledge about this neglected condition.
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Affiliation(s)
- Nguyen Hoai Nam
- Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Trauqui, Gialam, Hanoi, Vietnam
| | - Peerapol Sukon
- Faculty of Veterinary Medicine, Khon Kaen University, 123 Moo 16 Mittraphap Road, Nai-Muang, Muang District, Khon Kaen 40002, Thailand.,Research Group for Animal Health Technology, Khon Kaen University, 123 Moo 16 Mittraphap Road, Nai-Muang, Muang District, Khon Kaen 40002, Thailand
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Peltoniemi O, Oliviero C, Yun J, Grahofer A, Björkman S. Management practices to optimize the parturition process in the hyperprolific sow. J Anim Sci 2020; 98:S96-S106. [PMID: 32810239 DOI: 10.1093/jas/skaa140] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 04/24/2020] [Indexed: 12/19/2022] Open
Affiliation(s)
- Olli Peltoniemi
- Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Saarentaus, Finland
| | - Claudio Oliviero
- Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Saarentaus, Finland
| | - Jinhyeon Yun
- Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Saarentaus, Finland
| | - Alexander Grahofer
- Animal Physiology, Institute of Agricultural Sciences, ETH Zurich, Switzerland
| | - Stefan Björkman
- Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Saarentaus, Finland
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Oliviero C, Junnikkala S, Peltoniemi O. The challenge of large litters on the immune system of the sow and the piglets. Reprod Domest Anim 2020; 54 Suppl 3:12-21. [PMID: 31512316 DOI: 10.1111/rda.13463] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Accepted: 05/01/2019] [Indexed: 01/06/2023]
Abstract
The use of hyperprolific sow lines has increased litter size considerably in the last three decades. Nowadays, in some countries litters can reach up to 18-20 piglets being a major challenge for the sow's physiology during pregnancy, parturition and lactation. The increased number of piglets born per litter prolongs sensibly the duration of farrowing, decreases the piglets' average weight at birth and their vitality, increases the competition for colostrum intake and can affect negatively piglets' survival. This review aims to describe how large litters can affect the immune system of the sow and the piglets and proposes measures to improve this condition.
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Affiliation(s)
- Claudio Oliviero
- Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - Sami Junnikkala
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - Olli Peltoniemi
- Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
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Association between the incidence of stillbirths and expulsion interval, piglet birth weight, litter size and carbetocin administration in hyper-prolific sows. Livest Sci 2019. [DOI: 10.1016/j.livsci.2019.07.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Peltoniemi O, Björkman S, Oliviero C. Parturition effects on reproductive health in the gilt and sow. Reprod Domest Anim 2017; 51 Suppl 2:36-47. [PMID: 27762056 DOI: 10.1111/rda.12798] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In this review, we address significant characteristics of parturition in the pig and their connection to post-partum reproductive health and fertility. We discuss the normal physiology and behaviour around parturition and the effect of the second phase (expulsion of foetuses) on the third phase of parturition (expulsion of foetal membranes). In addition, we intend to cover retained placenta, and the connection to post-partum uterine health and fertility in the contemporary prolific sow. We also explore factors that support successful parturition or can cause potential problems. Successful parturition in the pig includes the possibility to express adequate maternal behaviour, rapid expulsion of the piglets, complete expulsion of the placenta, neonatal activity and colostrum intake. Abnormal incidents during any phase of parturition can cause subsequent problems. Duration of the expulsion phase of foetuses can be used as a simple measure of whether parturition is considered successful. Prolonged parturition can impair health of the sow and piglet and fertility after weaning. New insights, such as adding more fibre to sow diets during pregnancy, and especially during the period prior to farrowing, may prevent constipation, increase water intake of the sow around parturition and increase milk intake and performance of piglets. Maternal characteristics, including maternal behaviour, ease of parturition, colostrum production and piglet quality parameters, may be utilized to improve success rate of reproductive management during farrowing and early lactation. Additionally, we share some of the recent developments in methods, including ultrasonography in evaluation of post-partum uterine health. In conclusion, successful farrowing is of the greatest importance for reproductive health of the sow and survival of the piglets. We suggest connections exist among prolonged farrowing and yield of colostrum, retained placenta, development of PDS, and impaired involution of the uterus and reduced subsequent fertility.
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Affiliation(s)
- Oat Peltoniemi
- Department Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
| | - S Björkman
- Department Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - C Oliviero
- Department Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
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Assessment of ovarian activity in captive goral (Naemorhedus griseus) using noninvasive fecal steroid monitoring. Theriogenology 2014; 82:997-1006. [DOI: 10.1016/j.theriogenology.2014.07.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 07/10/2014] [Indexed: 11/23/2022]
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Vanderhaeghe C, Dewulf J, de Kruif A, Maes D. Non-infectious factors associated with stillbirth in pigs: a review. Anim Reprod Sci 2013; 139:76-88. [PMID: 23602009 DOI: 10.1016/j.anireprosci.2013.03.007] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 03/15/2013] [Accepted: 03/20/2013] [Indexed: 10/27/2022]
Abstract
The main objective of this review is to provide current information regarding non-infectious risk factors associated with stillborn piglets. These factors can be roughly categorized as genetic, maternal, piglet and environmental factors, but also interactions exist between several factors. An understanding of this multifactorial problem should help practitioners and farmers implementing a more effective farrowing management to obtain a high reproductive efficiency. From the papers studied in this review, it can be concluded that litter size, parity, sow's body condition and farrowing supervision/birth assistance seems to be the most relevant risk factors associated with stillborn piglets.
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Affiliation(s)
- C Vanderhaeghe
- ID-Nutrition bvba, Cannaertstraat 12, 8500 Kortrijk, Belgium.
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Evans ACO, Walsh SW. The physiology of multifactorial problems limiting the establishment of pregnancy in dairy cattle. Reprod Fertil Dev 2012; 24:233-7. [DOI: 10.1071/rd11912] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The failure of cows to successfully establish pregnancy after insemination is an important limiting factor for the efficiency of dairy production systems. The physiological reasons for this are many and pertain to the post partum and early pregnancy periods. Cows that suffer severe negative energy balance after parturition are prone to diseases (including uterine infection) that are, in part, explained by reduced function of the immune system, having negative consequences for subsequent fertility. In high-producing dairy cows, the duration and intensity of oestrus is low as a consequence of low circulating oestradiol concentrations, and after insemination, high embryo mortality is the single biggest factor reducing calving rates. Embryo mortality occurs as consequences of poor oocyte quality (probably caused by the adverse metabolic environment) and by poor maternal uterine environment (probably caused by carry-over effects of uterine infection and low circulating progesterone concentrations). Immediate improvements in the fertility of lactating cows on many farms can be achieved by applying existing knowledge, but longer-term sustained improvement will require additional knowledge in many areas including the physiology of the tissues that contribute to reproduction.
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