Estrategias en el manejo reproductivo de la cerda para la mejora de la fertilidad
- Autores: David Martín Hidalgo
- Directores de la Tesis: Juan Carlos Domínguez Fernández de Tejerina (dir. tes.), Beatriz Alegre Gutiérrez (dir. tes.), Rodrigo Manjarín Arredondo (dir. tes.)
- Lectura: En la Universidad de León ( España ) en 2014
- Idioma: español
- Número de páginas: 237
- Títulos paralelos:
- Reproductive management strategies for improving sow fertility
- Tribunal Calificador de la Tesis: José Félix Pérez Gutiérrez (presid.), Antonia Fernández Celadilla (secret.), FJCM van Eerdenburg (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: BULERIA
- Resumen
- español
El presente trabajo de Tesis Doctoral aborda cuatro ensayos experimentales cuyo principal objetivo ha sido la mejora del rendimiento reproductivo de la cerda mediante la identificación de las nulíparas con el mayor potencial fértil y la implantación de nuevas técnicas de manejo de la reproducción que mejoren la fertilidad en partos subsiguientes.
- English
Total number of weaned piglets per sow and year is the main factor determining the annual production of a sow commercial farm. Maximizing that parameter, with the aim of obtaining a high productivity, implies controlling over two important factors: on the one hand, the percentage of weekly breeding sows and, on the other hand, the reproductive performance of multiparous sows in the breeding herd. Capability to meet the weekly breeding target depends on both the number of weaned sows coming into heat per week and the existence of a continuous and predictable supply of service-ready gilts in estrus when required. Regarding the reproductive performance of the multiparous sow, in terms of litter size, this tends to experience a decrease from the 5th or 6th parity onwards. This situation implies the necessity of their replacement with service-ready cyclic gilts, which are required to show a certain degree of proven fertility before being included into the reproductive cycle, in order to guarantee the success of the replacement process.
Advancing the onset of puberty supposes a strategy that allows having a pool of cyclic gilts with a record of several estrous cycles prior to first breeding, showing a stable cyclic ovarian activity. Likewise, it also allows determining the degree of inherent fertility of the replacing gilt, identifying those which allow maintaining high reproductive standards on farm. Boar exposure is one of the most commonly used methods to initiate an early cyclic ovarian activity in the gilt, although sometimes it does not lead to satisfactory results, resulting in a delay in the onset of puberty or in a lack of cycling of the ovarian activity after its beginning. In such cases, treatment with exogenous gonadotrophins, as for example the administration of PG600® (400 IU eCG + 200 IU hCG), represents an effective tool for puberty induction in gilts, as well as for synchronizing the post-weaning estrus, allowing a 27 better control of the reproductive management on farm.
The overall objective of this Ph.D. dissertation is to improve sow reproductive performance by identifying gilts with the greatest fertile potential and implementing new reproductive management techniques that improve their fertility in subsequent farrowings.
The aim of the first study was to determine the association between the estrus response of prepubertal gilts to gonadotrophin injection or boar exposure and their subsequent farrowing rate and litter size. At 154 days of age, randomly selected prepubertal gilts received an intramuscular injection of 400 IU equine chorionic gonadotrophin plus 200 IU human chorionic gonadotrophin (PG600® ; n = 181). From the remaining pool of animals not treated with hormones, the first gilts showing signs of estrus were selected to act as Controls (n = 201). Boar exposure began at 155 days of age for both groups and gilts were bred at a weight of approximately 130 kg. Comparisons were made between PG600® - treated gilts exhibiting estrus or not within 7 days post injection (early and late-responders, respectively) and Control gilts exhibiting estrus or not within 30 days after beginning of boar exposure (select and non-select Control gilts, respectively). By 162 days of age, estrus was detected in 67.5% of PG600® -treated gilts compared to 5.7% of Control gilts (P < 0.0001). The proportion of animals observed in estrus at least 3 times before breeding was greater for select Control gilts compared to early and late-responder PG600® -treated gilts (P ≤ 0.001). There were no significant differences in farrowing rate and litter size between the four treatment groups. These data indicate that PG600® is an effective tool to induce an 28 earlier estrus in gilts, that subsequent farrowing rate and born alive litter size compares favorably to that of select gilts, and that gilts failing to respond promptly to hormonal stimulation do not exhibit compromised fertility.
The aim of the second study was to determine the effect of lactation length and treatment with gonadotrophins at weaning on reproductive performance of primiparous sows. After 3 weeks of lactation, primiparous sows were either weaned (W3; n = 273) or received a 7-day-old foster litter for a further 14 days of suckling (W5; n = 199). At final weaning (3 week or 5 week lactation) sows were randomly assigned to receive an injection of 400 IU equine chorionic gonadotrophin plus 200 IU human chorionic gonadotrophin (PG600® ; W3+P; n = 108 and W5+P; n = 96) or no injection (W3; n = 165 and W5; n = 103). Sows were inseminated at first observed estrus after final weaning and 24 h later. The proportion of sows showing estrus by day 6 post-weaning was greater (P < 0.01) for W3+P (86%) compared to W3 (64%); however, there was not a difference (P = 0.13) for W5+P (79.4%) compared to W5 (69.1%). There was no effect of either lactation length or gonadotrophin treatment on farrowing rates or on the proportion of sows culled before breeding. Total born litter size was smaller (P = 0.05) for W3+P (11.7 ± 0.4) compared to W3 (12.6 ± 0.3). However, sows that lactated for 35 days had larger litters than sows that lactated for 21 days, regardless of gonadotrophin treatment (14.0 ± 0.5 and 14.5 ± 0.4 for W5+P and W5, respectively; P < 0.001). These data indicate that for primiparous sows, a longer lactation improves total born litter size at their next farrowing. Gonadotrophin treatment is useful in shortening the weaning to estrus interval but subsequent total born litter size may be negatively affected.29 The aim of the third study was to determine whether a prompt estrus response of prepubertal gilts to gonadotrophin treatment is associated with improved long term sow performance. At 154 days of age, prepubertal gilts received an intramuscular injection of 400 IU equine chorionic gonadotrophin plus 200 IU human chorionic gonadotrophin (PG600® ; n = 260). Control gilts (n = 272) did not receive PG600® . All gilts were boar exposed from 155 days of age for estrus detection and gilts were subsequently artificially inseminated at a weight of approximately 130 kg. Gilts receiving PG600® that exhibited estrus by 7 days post injection were classified as early responders (ER); remaining PG600® -treated gilts were classified as late responders (LR). Within the control population, gilts exhibiting estrus by 185 days of age were classified as select (CS); remaining controls were classified as non-select (NS). Treatment response impacted (P = 0.03) retention rate, with a lesser proportion of LR gilts reaching parity 4 compared to NS gilts (50% vs. 69.4%, respectively; P = 0.09), with ER and CS gilt retentions rates being intermediate. These data indicate that gilts failing to respond promptly to PG600® administered at 154 days of age are more likely to be culled after fewer parities.
The aim of the fourth study was to investigate whether changes in the electrical resistance of vaginal mucus (VER) of weaned sows, during the first 7 days post-weaning, are associated with time of ovulation (as determined by ovarian ultrasound between 91 and 146 h after weaning) and season. VER measures were determined at 20, 44, 68, 91, 96, 102, 115, 120, 126, 140, 146 and 164 h post weaning. VER decreased between 120 and 31 h 30 prior to ovulation, and then increased until 40-50 h post ovulation. Duration and timing of the nadir was affected by season (P < 0.01). Estrus was observed from day 4 post-weaning, following the lowest VER values. Ovulation occurred between late day 5 and late day 6 post-weaning, while VER values were still increasing. Ovulation was earlier in lower parity sows (P < 0.001). Compared to 0 h (ovulation time), VER was significantly lower between 50 and 5 h pre-ovulation in autumn, and between 40 and 21 h pre-ovulation in winter, but such differences were not seen in spring. Lowest VER value was not correlated with time of ovulation. We conclude that VER increases prior to ovulation and that this increase is influenced by season but cannot be used to accurately predict ovulation in weaned sows.
- español
