The enhancement of genetic selection, nutrition, management and health has improved sow productivity, including producing larger litters. However, larger litters have increased the total farrowing duration and, consequently, the need for farrowing assistance (Canario et al., 2006). Increased farrowing duration has been associated with the increased incidence of stillborn piglets.
In fact, it is estimated 82% of piglets defined as stillborn die during farrowing due to intrapartum asphyxiation as the main cause (Rangstrup-Christensen et al., 2018). A common sow barn protocol is to provide farrowing assistance (i.e. sleeving) whenever 20 minutes has elapsed since the previous piglet was born. The goal of farrowing assistance is to reduce incidence of stillbirths; however, there is limited consideration for parity, litter size or sow energy status.
At the SDSU Swine Education and Research Facility, four batch farrowing groups were monitored 24 hours a day from gestation Day 114 of the earliest expected litter to the last piglet born in each farrowing group. Influence of sow parity, litter size, feeding time prior to farrowing and birth order on birthing interval and farrowing duration were assessed.
Birth interval of all piglets, and hence farrowing duration, was recorded in 80 litters. The time of day of each piglet birth was documented and the total farrowing duration was determined as the time elapsed between birth of the first and last piglet. Sleeving, according to the protocol (i.e. obstetrical sleeve and lubricant taking care not to touch crate surfaces with gloved hand prior to sleeving), was used when 60 minutes had elapsed since the previous piglet.
When farrowing was deemed to be complete (i.e. no presence of newly born piglets for 120-plus minutes, no presence of piglets in the birth canal following sleeving, multiple signs of placental expulsion and evidence of uterine collapse upon sleeving), oxytocin was provided to aid in milk let down.
Pre-farrow feed is allocated in six feedings every three hours beginning at 0500 hour daily with the use of an electronic feeding system (Gestal 3G; Jyga Technologies, Greeley, Kan.). Time of last feed drop into the feeders was used to characterize the feed intake pattern of sows before farrowing.
Sows with litters of more than 14 piglets had shorter birthing interval than sows with litters of less than 14 piglets (P <.0001) resulting in a 9-minute shorter total farrowing interval with larger litter sizes (Table 1). The longer farrowing duration with smaller litters may be related to a higher proportion of gilts (typically smaller litter sizes) but may also be related to the degree of fetal cortisol and placental oestrogen which are important for initiation and maintenance of contractions (as noted by van Dijk et al., 2005).
Order of birth affected birth interval (P=0.014), where piglets of order 1 to 4 had the longest birth interval (approximately 30 minutes) and orders 9 to 12 shortest birth interval (approximately 20 minutes). A similar curvilinear pattern of birthing interval was reported by van Dijk et al. (2005) regardless of sow breed. It was suggested the pattern of maternal serum concentrations of oxytocin and vasopressin may explain this curvilinear relationship (van Dijk et al., 2005). Sow feed intake prior to farrowing and parity did not affect total farrowing duration or birthing interval; however, farrowing duration of Parity 2 and Parity 3 sows was 30 to 50 minutes shorter than young and older females. The pre-farrow daily feed allocation schedule may have influenced sow energy status prior to farrowing. Feyera et al. (2018) recommended at least three daily meals in late-gestation to limit the number of sows in low-energy status at the onset of farrowing to reduce the odds of stillborns and need for farrowing assistance.
In practice, despite sleeving protocols calling for farrowing assistance when the birth interval has reached 20 minutes in many commercial farms, when a single technician is monitoring 40 to 60 females in varying stages of farrowing, the likelihood of meeting a 20-minute sleeving protocol may already be small.
Furthermore, there is no universal definition of "prolonged farrowing" or how long is "too long". Even within the literature, farrowing duration is quite variable. For example, Oliviero et al. (2010) reported that the average total farrowing duration was 272 ±152 minutes. Based on observational data, it is not unusual to have upwards of 60 minutes between the first and second piglets born within a litter.
In conclusion, sow barn farrowing assistance protocols may need to be revised considering sow parity and the expected litter size. Moreover, this and the work of others would suggest that farrowing assistance may be best focused on low- and/or high-parity animals to improve the time efficiency of barn staff while still ensuring maximal number of piglets born alive.
Canario, L, Roy, N., Gruand, J., and Bidanel, J. 2006. Genetic variation of farrowing kinetics traits and their relationships with litter size and perinatal mortality in French Large White sows. J. Anim. Sci. 84:1053–1058. doi:10.2527/2006.845153x
Feyera, T., Pedersen, F., Krogh, U., Foldager, L., and Theil, P.K. 2018. Impact of sow energy status during farrowing on farrowing kinetics, frequency of stillborn piglets, and farrowing assistance. J. Anim. Sci. 96:2320-2331 doi: 10.1093/jas/sky141.
Oliviero C., Heinonen M., Valros A., and Peltoniemi O. Environmental and sow-related factors affecting the duration of farrowing. Anim Reprod Sci. 2010;119(1-2):85-91. doi:10.1016/j.anireprosci.2009.12.009
Rangstrup-Christensen, L., Schild, S.-L.A., Pedersen, L.J., and Sørensen, J.T. 2018. Causes of preweaning mortality in organic outdoor sow herds. Res. Vet. Sci., 118 (2018), pp. 171-180.
Van Dijk, A.J., van Rens, B.T.T.M., van der Lende, T., and Taverne, M.A.M. 2005. Factors affecting duration of the expulsive stage of parturition and piglet birth intervals in sows with uncomplicated, spontaneous farrowings. Theriogenology 64: 1573-1590.
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