An evaluation of the impact of increased lactation length on the reproductive efficiency of sows in commercial herds

Selecting the optimal strategies when using nurse sows for supernumerous piglets

Hyper-prolific sows frequently do not have a sufficient number of functional teats for their piglets to nurse which has led to the use of nurse sows to manage these surplus piglets. This review discusses strategies for using nurse sows and factors that influence preweaning survival and weight gain of their litters, as well as those that affect their subsequent rebreeding performance. Rearing piglets using a nurse sow can be as successful as piglets reared with their biological mother and is thus a powerful management tool to decrease preweaning piglet mortality. Selecting a young sow as nurse sow is beneficial for piglet survival; however, piglets nursing first parity sows often have a lower daily weight gain than piglets nursing multiparous sows. A litter of uniform surplus piglets is preferably handled using the two-step nurse sow strategy. A consequence of nonuniform litters will most likely be an increased mortality and decreased weaning weight among the smallest piglets within a litter. The subsequent fertility of nurse sows is not compromised. There is an increased risk of lactational oestrus when using nurse sows leading to an increased weaning-to-oestrus interval; however, litter size in nurse sows is identical or even moderately higher in the subsequent parity compared with nonnurse sows.

Identifying Risk Factors for Low Piglet Birth Weight, High Within-Litter Variation and Occurrence of Intrauterine Growth-Restricted Piglets in Hyperprolific Sows

Simple Summary

Piglet mortality is an ongoing concern for pig production worldwide. Piglets that have a low piglet birth weight (PBW), suffer from intrauterine growth restriction (IUGR) or are born from litters with a high within-litter variation in PBW (CV_PBW) have an increased risk of dying before weaning. IUGR piglets, CV_PBW and a low PBW might be connected by the same risk factors, and in order to optimize fetal development in the litter, these risk factors should be identified. Free-access stall feeding, floor feeding and electronic sow feeding systems are commonly used feeding systems for gestating sows in Denmark. These systems differ in several points, including in sow competition at feeding. The nutritional status of the sow is important for fetal development, and so the feeding method during gestation is also expected to affect such development. Of the risk factors identified in this study, increasing litter size was considered the most critical. Only small differences were found between the feeding systems and these differed amongst groups. The results should inspire further investigation of those risk factors to clarify causes of the observed effects and what drives individual herd differences.

Abstract

This study aimed to identify risk factors affecting PBW, high CV_PBW and the occurrence of IUGR piglets in 12 commercial Danish herds with hyperprolific sows using free-access stalls, floor or electronic sow feeding systems in the gestation unit. The following factors were investigated: the duration of previous lactation, the length of the interval from weaning to insemination, the length of gestation, litter size, parity, sow backfat thickness in late gestation and the type of feeding system in the gestation unit. The study included newborn piglets from 452 litters with the following production indicator averages: 21.3 piglets/L, 1235 g PBW, 22.9% CV_PBW and 10.9% and 11.8% within-litter occurrence of severe and mild IUGR piglets, respectively. Increasing length of weaning-to-insemination interval decreased PBW by 25.8 g/day. For 2nd to 9th parity sows, each additional piglet in the litter increased CV_PBW by 0.38%, the occurrence of severe IUGR piglets by 0.68% and mild IUGR piglets by 0.50%. Sows of 5th parity and older had a 1.39% higher CV_PBW and 49.1 g lighter piglets compared with sows of 2nd to 4th parity. PBW was lower in one ESF herd, suggesting complex interactions that need to be further elucidated. The main critical risk factor observed was litter size.

Sire line of pigs affects weaning weight, growth performance, and carcass characteristics of offspring

Today, early weaning is more frequently applied by the modern pig breeder to obtain more litters per year. In addition, more and more European pig breeders apply a batch management system, which allows weaning to occur at fixed time points but entails that the offspring are treated at the litter level and not as individuals. Both evolutions might result in weaning lightweight piglets, which can cause, e.g., growth retardation of the offspring. Hence, the objective of this research was to improve the weaning weight of piglets of the same age by breeding with a highly conformed sire line. Therefore, a total of 23 sows were inseminated, 10 sows with semen of a well-conformed sire line (sire line B) and 13 sows with semen of a less conformed boar (sire line A). In total, 299 offspring were observed to monitor behavior, growth performance, and carcass characteristics. Subsequently, linear mixed models were developed to analyze the growth performance and carcass characteristics wherein only variables classified as significant ( < 0.05) were introduced as fixed factors. Results indicate that no significantly increased weaning weight could be accomplished by breeding with semen of sire line B. This could be due to the significant ( < 0.05) shorter gestation length of sows inseminated with semen of sire line B. However, the offspring of sire line B was defined by better carcass classification characteristics. Furthermore, this study presents that the mean birth weight of each piglet was significantly lower if a bigger litter size was recorded. When considering behavior, it was observed that piglets that did not seclude themselves from the litter had a significantly greater daily weight gain from birth to weaning compared to piglets that showed signs of isolation from the litter. A significantly greater daily gain from birth to slaughter was established for piglets with a greater birth weight. Also, results indicate that barrows had a significantly greater daily growth from weaning to slaughter than gilts. To conclude, this research determines that breeding with highly conformed sire lines does not improve the weaning weight of the offspring and thus cannot serve as a solution for early weaning. However, more research is required by performing more experiments with a greater number of boars and sows to confirm this result. In general, this study allows researchers to continue to improve and standardize the weaning weight of piglets of the same age.

Reproductive performance of "nurse sows" in Danish piggeries

The use of nurse sows in Danish piggeries is common practice because of large litter sizes; however, the effect of being selected as a nurse sow on subsequent reproductive performance is unknown. Therefore, the aim of this study was to quantify a nurse sow's reproductive performance in the subsequent litter. Nurse sows were defined as sows weaning their own litter at least 18 days postpartum and thereafter nursing another litter (nurse litter) before service. Data (2012-2013) from 20 piggeries with more than 14.5 live born piglets per litter and a stable distribution of sows among parities over time were selected. Records from 79,864 litters were obtained and analyzed using mixed linear and logistic regression models. The average lactation lengths were 40.3 days for nurse sows and 27.8 days for non-nurse (normal) sows. Nurse sows weaned on average 12.4 piglets and subsequently 11.5 nurse piglets, whereas non-nurse weaned 11.7 piglets in their single weaning. There was no difference in re-service rate between nurse and non-nurse sows in the subsequent reproductive cycle. Subsequent litter size in the next reproductive cycle was higher for nurse sows than that for non-nurse sows (18.69 vs. 18.11 total born piglets; P < 0.001). Nurse sows were of a slightly lower parity than non-nurse sows (3.12 vs. 3.27, P < 0.001), and nurse sows had an increased weaning to estrus interval compared to non-nurse sows (4.23 vs. 4.19 days, P < 0.001). The results indicate that nurse sows were selected among sows nursing large litters and could therefore suggest that these sows represent the best percentile of sows in a given piggery. In conclusion, this survey indicated no negative effects of being selected as a nurse sow on the subsequent reproductive performance. On the contrary, nurse sows gave birth to more piglets compared to non-nurse sows in their subsequent litter.

Prolonged duration of farrowing is associated with subsequent decreased fertility in sows

In modern swine production failure of sows to become pregnant within the expected time after weaning results in major economic loss and culling of sows. The objective of this study was to determine the effects of duration of farrowing on subsequent repeat breeding rate. The study was performed in a commercial sow-pool piggery system in Finland comprising 148 sows (Yorkshire × Landrace). A multivariate analysis was undertaken on data for parity, weaning to estrus interval, boar, number of inseminations, season, sow back-fat thickness, gestation length, duration of farrowing, number of live-born piglets, number of stillborn piglets, lactation length, and number of piglets weaned. Furthermore, two farrowing systems (crate vs. pen) were investigated. A binary logistic regression was used to analyze the effect of these factors on the repeat breeding rate (pregnant vs. not pregnant at first insemination after weaning). The total duration of previous farrowing was longer in rebred sows (357 ± 207 minutes, average ± SD) than in pregnant sows (255 ± 126 minutes; P < 0.01). The other parameters were not statistically significant to the outcome of first insemination after weaning. In conclusion, we established that sows with long duration of farrowing have higher repeat breeding rate at the first insemination after weaning and could be used as an indicator for subsequent fertility.