Duration of lactation, endocrine and metabolic state, and fertility of primiparous sows

The importance of optimal body condition to maximise reproductive health and perinatal outcomes in pigs

Overnutrition or undernutrition during all or part of the reproductive cycle predisposes sows to metabolic consequences and poor reproductive health which contributes to a decrease in sow longevity and an increase in perinatal mortality. This represents not only an economic problem for the pig industry but also results in poor animal welfare. To maximise profitability and increase sustainability in pig production, it is pivotal to provide researchers and practitioners with synthesised information about the repercussions of maternal obesity or malnutrition on reproductive health and perinatal outcomes, and to pinpoint currently available nutritional managements to keep sows' body condition in an optimal range. Thus, the present review summarises recent work on the consequences of maternal malnutrition and highlights new findings.

Second litter syndrome in Iberian pig breed: factors influencing the performance

Second litter syndrome (SLS) consists of a loss of prolificacy in the second parity (P2), when a sow presents the same or lower results for litter size than in the first parity (P1). This syndrome has been reported for modern prolific breeds but has not been studied for rustic breeds. The objectives of this study are to determine how and to what degree Iberian sows (a low productivity breed recently raised on intensive farms) are affected by SLS; to establish a target and reference levels; and to assess the factors influencing the performance. Analysed data correspond to 66 Spanish farms with a total of 126 140 Iberian sows. The average Iberian sow prolificacy in P1 was 8.91 total born (TB) and 8.47 born alive (BA) piglets, whereas in P2, it decreased by -0.05 TB and -0.01 BA piglets, suggesting some general incidence of SLS. At the sow level, 56.63% did not improve prolificacy in terms of BA piglets in P2, and 16.98% had a clear decrease in prolificacy, losing ≥3 BA piglets in P2. Within herds, a mean of 57.75% of sows showed SLS, with an evident decrease in the number of BA piglets in P2. The plausible target for the Iberian farm's prolificacy comes from the quartile of farms with the lowest percentage of SLS sows within the farms with the highest prolificacy between P1 and P2 (mean of 8.77 BA). So, in this subset of farms (N = 17), 47.3% of sows improved their prolificacy in P2 (i.e. did not show SLS). Hence, half the sows could be expected to show SLS even on farms with a good performance. Finally, this study brings out the main factors reducing P2 prolificacy through SLS in the Iberian breed: later age at first farrowing, long first lactation length, medium weaning to conception interval and large litter size in P1. In conclusion, improving the reproductive performance of Iberian farms requires reducing the percentage of sows with SLS, paying special attention to those risk factors. The knowledge derived from this study can provide references for comparing and establishing objectives of performance on Iberian sow farms which can be used for other robust breeds.

Equine chorionic gonadotropin pretreatment 15 days before fixed-time artificial insemination improves the reproductive performance of replacement gilts

Fixed-time artificial insemination (FTAI) technology uses exogenous reproductive hormones to regulate the sexual cycle and ovulation of sows without oestrus identification, which improves the sow breeding utilisation rate, reduces the number of non-productive days, and elevates the efficiency of pig farm management. In this study, we aimed to optimise FTAI procedures. Healthy 190-day-old and about 90 kg Large White × Landrace crossing breed replacement gilts (n = 166) which were of unknown reproductive status were randomly selected and divided into three groups: a control group (n = 62), an eCG-15D group in which the gilts were pretreated with equine chorionic gonadotropin (eCG) injection 15 days before starting FTAI (n = 50), and an eCG-20D group pretreated with eCG injection 20 days before starting FTAI (n = 54). All three groups were then subjected to the same conventional FTAI procedure. Pigs were orally administered Altrenogest (ALT, 20 mg per pig per day) for 18 days and then 42 h after ALT feeding was stopped, they were injected with 1 000 IU eCG followed by 100 μg GnRH 80 h later. The gilts were inseminated for the first time 24 h after gonadotropin-releasing hormone (GnRH) injection and then again 16 h later. After 42 h of ALT feeding, gilts in the eCG-15D group displayed a higher follicular diameter until artificial insemination (AI) than those from the other groups (P < 0.05). In addition, the ovulation times were the most synchronised in the eCG-15D group, with 100% of the gilts ovulating before the second AI on day 25 of FTAI. Furthermore, the gilts in the eCG-15D group achieved the highest pregnancy rate (92%), farrowing rate (90%), total pigs born (11.59), and pigs born alive (11.18). Together, the findings of this study demonstrate that reproductive performance can be optimised by pretreating gilts with eCG 15 days before conventional FTAI.

Latest Advances in Sow Nutrition during Early Gestation

In the pig, the establishment and maintenance of luteal function in early gestation is crucial to endometrial function, embryo development, and survival. The level of feed intake has a positive effect on formation of luteal tissue and progesterone secretion by the ovaries in the pre-implantation period, which is important for endometrial remodeling and secretion. These effects are independent of luteinising hormone (LH) and probably driven by metabolic cues, such as insulin and insulin-like growth factor (IGF-1), and seem to support progesterone secretion and delivery to the endometrium, the latter which occurs directly, bypassing the systemic circulation. Even after implantation, a high feed intake seems to improve embryo survival and the maintenance of pregnancy. In this stage, luteal function is LH-dependent, although normal variations in energy intake may not result in pregnancy failure, but may contribute to nutrient supply to the embryos, since in this phase uterine capacity becomes limiting. Feed incidents, however, such as unintended fasting of animals or severe competition for feed, may result in embryo or even pregnancy loss, especially in periods of seasonal infertility. Specific nutrients such as arginine have a role in the vascularisation of the placenta and can improve the uterine capacity in the period after implantation.

Effect of suckling intensity of primiparous sows on production performance during current and subsequent parities1

This study was conducted to evaluate the effects of suckling intensity (litter size and lactation length) to primiparious sows on production performance during current and subsequent parities. Upon farrowing, 115 primiparous sows (farrowing weight: 222.7 ± 20.0 kg) were initially allotted to 4 treatments in a 2 × 2 factorial arrangement with 2 litter sizes: 10 and 13 piglets (LS10 vs. LS13), and 2 lactation lengths: 21 and 27 d (LL21 vs. LL27). Upon weaning, sows were rebred and those farrowed successfully (n = 66) kept 10 piglets and weaned at 21 d in the second parity. Sows were fed ad libitum during lactation in both parities. Feed intake, BW loss, backfat loss, litter size, and litter weight gain during lactation in both parities were determined. Litter weight gain in LS13 was greater (P < 0.05) than that in LS10 (54.4 vs. 47.7 kg) during the first lactation. Sows in LS13 had a greater (P < 0.05) BW loss than sows in LS10 (24.1 vs. 17.4 kg). Body weight loss was not different between LL27 and LL21. Sows in LS13 tended to have a greater (P = 0.075) removal rate than those in LS10 (47.5 vs. 32.2%). Sows in LL27 had a smaller (P < 0.05) removal rate than those in LL21 (28.0 vs. 51.7%). In the second parity, gestation BW gain in LL27 tended to be greater (P = 0.098) than that in LL21 when the previous litter size was 10 piglets (56.1 vs. 33.2 kg). Litter performance and feed intake of sows were not affected by previous litter size, lactation length, and their interaction. The farrowing weight, farrowing body protein and lipid, body weight loss was not different between LS13 and LS10, whereas backfat loss in LS13 was smaller (P < 0.05) than that in LS10 during the second lactation (0.9 vs. 2.4 mm). The predicted body lipid loss in LS13 was also smaller than that in LS10 (2.3 vs. 5.3 kg) during the second lactation. Sows in LL27 had a smaller (P < 0.05) BW loss and body lipid loss during the second lactation than sows in LL21 (4.0 vs. 9.0 kg; 2.3 vs. 4.8 kg). The concentration of milk fat in LL27 was smaller (P < 0.05) than that in LL21 (7.9 vs. 9.1%). In conclusion, increasing suckling intensity to primiparous sows increased litter weight gain but increasing litter size reduced piglet ADG. Sow performance in the second lactation was not negatively affected by increasing suckling intensity of the first lactation. Interestingly, sows with an increased suckling intensity in the first lactation had reduced loss of body reserves in the second lactation.

Factors affecting estrus and ovulation time in weaned sows with induced ovulation by GnRH administration in different seasons

Follicle development in post-weaning sows is influenced by various factors. To control ovulation time using hormone, factors that influence ovulation should be investigated. The present study was performed to evaluate the effect of GnRH (buserelin) administration in relation to season and sow parameters on ovulation time in weaned sows. Seventy-seven weaned sows were divided into the following groups: control (hot season, n=21; cool season, n=16) and treatment (hot season, n=22; cool season, n=18). Sows were kept in a close house equipped with an evaporative cooling system. Ovulation time was determined every 6 hr using transrectal ultrasonography. Administration of 10 µg buserelin at 72 hr after weaning affected estrus-to-ovulation interval (EOI) and weaning-to-ovulation interval (WOI) in sows (P<0.05). The percentage of sows that ovulated between 44–56 hr after injection was higher in the cool season than in hot season (P<0.05). Weaning-to-estrus interval (WEI) and injection-to-estrus interval (IEI) were affected by season (P<0.05). Body condition score (BCS) of sows influenced EOI (P<0.01). Sows with low backfat thickness, lactation length <20 days, or litter weight ≥67 kg, had delayed injection-to-ovulation interval (P<0.05). In conclusions, buserelin administration (10 µg, at 72 hr after weaning) advanced ovulation. Hot season prolonged ovulation time. Sows that were weaned with lactation length of at least 20 days, litter weight less than 67 kg, or BCS of at least 3, had better responses to buserelin injection. High backfat reserve after weaning is important for ovulation induction response by buserelin injection.

An association analysis of sow parity, live-weight and back-fat depth as indicators of sow productivity

Understanding how critical sow live-weight and back-fat depth during gestation are in ensuring optimum sow productivity is important. The objective of this study was to quantify the association between sow parity, live-weight and back-fat depth during gestation with subsequent sow reproductive performance. Records of 1058 sows and 13 827 piglets from 10 trials on two research farms between the years 2005 and 2015 were analysed. Sows ranged from parity 1 to 6 with the number of sows per parity distributed as follows: 232, 277, 180, 131, 132 and 106, respectively. Variables that were analysed included total born (TB), born alive (BA), piglet birth weight (BtWT), pre-weaning mortality (PWM), piglet wean weight (WnWT), number of piglets weaned (Wn), wean to service interval (WSI), piglets born alive in subsequent farrowing and sow lactation feed intake. Calculated variables included the within-litter CV in birth weight (LtV), pre-weaning growth rate per litter (PWG), total litter gain (TLG), lactation efficiency and litter size reared after cross-fostering. Data were analysed using linear mixed models accounting for covariance among records. Third and fourth parity sows had more (P0.05). Heavier sow live-weight throughout gestation was associated with an increase in PWM (P0.05). In conclusion, this study showed that sow parity, live-weight and back-fat depth can be used as indicators of reproductive performance. In addition, this study also provides validation for future development of a benchmarking tool to monitor and improve the productivity of modern sow herd.

Estimation of genetic parameters for traits associated with reproduction, lactation, and efficiency in sows

Increased milk production due to high litter size, coupled with low feed intake, results in excessive mobilization of sow body reserves during lactation, which can have detrimental effects on future reproductive performance. A possibility to prevent this is to improve sow lactation performance genetically, along with other traits of interest. The aim of this study was to estimate breed-specific genetic parameters (by parity, between parities, and across parities) for traits associated with lactation and reproduction in Yorkshire and Landrace sows. Performance data were available for 2,107 sows with 1 to 3 parities (3,424 farrowings total). Sow back fat, loin depth and BW at farrowing, sow feed intake (SFI), and body weight loss (BWL) during lactation showed moderate heritabilities (0.21 to 0.37) in both breeds, whereas back fat loss (BFL), loin depth loss (LDL), and litter weight gain (LWG) showed low heritabilities (0.12 to 0.18). Among the efficiency traits, sow lactation efficiency showed extremely low heritability (near zero) in Yorkshire sows but a slightly higher (0.05) estimate in Landrace sows, whereas sow residual feed intake (SRFI) and energy balance traits showed moderate heritabilities in both breeds. Genetic correlations indicated that SFI during lactation had strong negative genetic correlations with body resource mobilization traits (BWL, BFL, and LDL; -0.35 to -0.70), and tissue mobilization traits in turn had strong positive genetic correlations with LWG (+0.24 to +0.54; < 0.05). However, SFI did not have a significant genetic correlation with LWG. These genetic correlations suggest that SFI during lactation is predominantly used for reducing sow body tissue losses, rather than for milk production. Estimates of genetic correlations for the same trait measured in parities 1 and 2 ranged from 0.64 to 0.98, which suggests that first and later parities should be treated as genetically different for some traits. Genetic correlations estimated between traits in parities 1 and 2 indicated that BWF and BWL measured in parity 1 can be used as indicator traits for SFI and SRFI measured in parities 1 and 2. In conclusion, traits associated with lactation in sows have a sizable genetic component and show potential for genetic improvement.

Maternal age modulates the effects of early-pregnancy L-proline supplementation on the birth-weight of piglets

Previous results obtained in gilts maintained under experimental conditions suggest that amino acid supplementation during pregnancy may be a promising strategy for diminishing the incidence of embryo losses and low birth-weight newborn. The current study evaluated the effects of a short-term supplementation with L-proline, around implantational stages, on litter size and birth-weight of piglets in sows of different parities maintained under commercial farm conditions. There were no significant effects in mature sows with three or more parities, but the supplementation improved the reproductive efficiency of the high-prolific first-parity sows and of all the sows at second-parity. There were numerically higher litter size (of around two more live piglets; n.s.) and higher birth-weights (P<0.05) in the supplemented animals. The results of this study indicate that the effects of L-proline supplementation on litter size and birth-weight are strongly modulated by the maternal characteristics; specifically by parity and prolificacy and that supplementation may be cost-efficient for the management of females with compromised energy balance; specifically, sows at second farrowing and highly-prolific primiparous gilts.

Lactational oestrus and reproductive performance following a delayed limited nursing schedule in primiparous sows

With conventional lactation management, sows only conceive after weaning. However, intermittent suckling (IS) enables follicle growth and ovulation during lactation by reducing the suckling-induced inhibition of gonadotrophins. The current study evaluated IS regimes initiated at Day 21 or Day 28 post farrowing compared to conventional weaning on Day 28, in primiparous sows. Sows (Large White and Large White x Landrace) were randomly allocated to Control (C28; n = 44), IS21 (n = 29) and IS28 (n = 34) treatments at Day 20. Sows in IS21 and IS28 were subjected to intermittent suckling from Day 21 or Day 28 post farrowing. During IS, sows were separated from their piglets for 8 h daily, then weaned 7 d later at Day 28 and Day 35 respectively, whereas piglets in the C28 treatment had continuous access to sows until weaning at Day 28. Percentage of IS sows that showed oestrus during lactation was 59% (16/27) in IS21 and 72% (21/29) in IS28 (P > 0.05). Cumulatively over the lactation and 7 d post-weaning period, 93% of IS21, 85% of IS28 and 93% (31/33) of C28 sows showed oestrus (P > 0.05). Pregnancy rate at Day 30 post mating, for sows that were mated during lactation was 93% (15/16) in IS21 and 95% (20/21) in IS28, whereas C28 sows had a 96% (30/31) pregnancy rate (P > 0.05). No difference was found in the time of oestrus relative to weaning (C28) or onset of IS (IS21 and IS28) (P > 0.05). The IS sows that did not ovulate before weaning all showed oestrus within 7 days from weaning, and the weaning to oestrus interval was similar to control sows (P > 0.05). However, for all IS sows (across IS treatments) that showed lactational ovulation, LH secretion pattern at onset of IS was different (P < 0.05) from the sows that did not ovulate in lactation. Plasma progesterone concentration tended to be lower in the IS21 treatment (P < 0.10) compared to the C28 sows at 4 d after ovulation. The subsequent litter size was not affected by treatments although numerically lower for IS21 (P > 0.05). The present study showed that in modern primiparous sows, lactational oestrus can be induced and pregnancy can be maintained at a similar rate and producing comparable subsequent litter sizes to conventionally weaned sows when IS commenced at four weeks post farrowing. However, when IS commences at three weeks post farrowing, this may affect the percentage of sows showing oestrus in lactation and may potentially influence subsequent litter size.

Genetic correlations between first parity and accumulated second to last parity reproduction traits as selection aids to improve sow lifetime productivity

Objective

The objective of this research was to estimate genetic correlations between number of piglets born alive in the first parity (NBA1), litter birth weight in the first parity (LTBW1), number of piglets weaned in the first parity (NPW1), litter weaning weight in the first parity (LTWW1), number of piglets born alive from second to last parity (NBA2+), litter birth weight from second to last parity (LTBW2+), number of piglets weaned from second to last parity (NPW2+) and litter weaning weight from second to last parity (LTWW2+), and to identify the percentages of animals (the top 10%, 25%, and 50%) for first parity and sums of second and later parity traits.

Methods

The 9,830 records consisted of 2,124 Landrace (L), 724 Yorkshire (Y), 2,650 LY, and 4,332 YL that had their first farrowing between July 1989 and December 2013. The 8-trait animal model included the fixed effects of first farrowing year-season, additive genetic group, heterosis of the sow and the litter, age at first farrowing, and days to weaning (NPW1, LTWW1, NPW2+, and LTWW2+). Random effects were animal and residual.

Results

Heritability estimates ranged from 0.08±0.02 (NBA1 and NPW1) to 0.29±0.02 (NPW2+). Genetic correlations between reproduction traits in the first parity and from second to last parity ranged from 0.17±0.08 (LTBW1 and LTBW2+) to 0.67±0.06 (LTWW1 and LTWW2+). Phenotypic correlations between reproduction traits in the first parity and from second to last parity were close to zero. Rank correlations between LTWW1 and LTWW2+ estimated breeding value tended to be higher than for other pairs of traits across all replacement percentages.

Conclusion

These rank correlations indicated that selecting boars and sows using genetic predictions for first parity reproduction traits would help improve reproduction traits in the second and later parities as well as lifetime productivity in this swine population.

Effect of body development from first insemination to first weaning on performance and culling until the third farrowing of Landrace x Large White swine females

The aim of this study was to verify the association of sow body weight development until the 1st weaning with reproductive performance, piglet production and culling rate until the 3rd farrowing in 196 primiparous sows using logistic regression models. Each 10kg increase in weight gain in the 1stpregnancy (OR= 0.63), weight at 1st farrowing (OR= 0.70), weight at the 1st weaning (OR= 0.73) or weight gain from the 1startificial insemination (AI) to the 1st weaning (OR= 0.67) decreased the percentage of primiparous sows with long weaning-to-oestrus interval - WOI (>5 days). An increasing lactation length and an increase in the number of weaned piglets were responsible for respectively decreasing (OR= 0.77-0.80, per day of lactation) and increasing (OR= 1.52-1.59, per piglet weaned) the percentage of sows with long WOI. Sows with <159.5kg at weaning had higher odds of non-farrowing (NFR) compared to sows with >170kg (OR= 4.73). Sows with <17.5kg of gain from the 1st AI to the 1st weaning had higher odds (OR= 4.88) of NFR than sows gaining >30kg. Each additional lactation day decreased the NFR (OR= 0.74). Females weighing <139kg at the 1st AI had higher percentages of small numbers of total born in the second parity (STB2, OR= 2.00) and over three parities (OR= 3.28) compared to those weighing ≥139kg. Sows with weight gain <25kg at the 1st pregnancy had higher odds of STB2 (OR= 3.01) compared to sows gaining >35kg. Each 10kg of increase in weight at the 1st weaning or in weight gain from the 1stAI to the 1stweaning decreased the total culling rate (OR= 0.71 and 0.73, respectively) and culling for reproductive reasons (OR= 0.57 and 0.61, respectively). The culling rate until the 3rdfarrowing was also increased in sows with a smaller first litter size. The results show that not only reaching a minimum weight at the 1st AI but also having an adequate body weight gain until the 1st weaning is important for the reproductive performance, productivity and retention of Landrace x Large White Danbred sows in the herd.

Substituição parcial do milho por sorgo granífero na alimentação de matrizes suínas primíparas durante a lactação

Avaliou-se o efeito da substituição parcial do milho por sorgo granífero na dieta de matrizes suínas híbridas durante as fases de lactação e pós-desmame. Foram utilizadas 25 fêmeas, distribuídas em três tratamentos, com porcentagens crescentes de sorgo granífero - 0%, 25% e 50% - em substituição ao milho. Os animais foram avaliados durante as fases de lactação e pós-desmame, tendo sido mensurados o peso vivo (PV) e a espessura de toucinho (ET) ao parto, ao oitavo, 16º e 25º dias de lactação - desmame. Nesses momentos, foram realizadas colheitas de amostras de leite para análise bioquímica. As leitegadas foram pesadas no mesmo intervalo de tempo. No estro pós-desmame (RE), determinou-se o intervalo estro-cobertura (dias), PV e ET. Quanto às fêmeas, não ocorreram efeitos sobre o PV e a ET. Quanto ao número e ao peso dos leitões, as fêmeas do grupo controle apresentaram maior número de leitões nascidos vivos. O GPD dos leitões foi maior nas leitegadas dos tratamentos com 50% de sorgo. Não houve diferença para as análises do leite. No RE, não ocorreram efeitos. Dessa forma, conclui-se que o sorgo granífero pode substituir o milho em até 50% na dieta de fêmeas suínas durante lactação, sem comprometer os parâmetros produtivos e reprodutivos.

Effects of lactation length and boar contact in early lactation on expression of oestrus in multiparous sows

The ability to stimulate a fertile oestrus during early lactation provides an opportunity to increase piglet weaning age whilst maintaining 2.4 litters per sow per year. This study evaluated the effects of boar contact beginning on day 7 of lactation and lactation length on lactation oestrus induction and subsequent reproductive output in multiparous sows (parity 2.9 ± 0.16; mean ± SEM; range 2-6). Large White × Landrace multiparous sows were allocated to one of four treatment groups; weaning at 26 days post-partum and no boar contact (control); weaning at 26 days and boar contact (BC); weaning at 7 days and boar contact (BC+short lactation (SL)); and weaning at 7 days and no boar contact (SL). Control and SL sows were taken for a short walk daily during which a backpressure test was performed in the absence of a boar. Oestrus expression within 26 days of farrowing was significantly higher in BC (67%) and BC+SL (93%) sows than control (11%) and SL (13%) sows (P<0.05). Of sows mated within 26 days of farrowing, there was no difference in the number of piglets born alive or stillborn. Therefore, boar contact is an effective method to stimulate oestrus within 26 days of farrowing in both lactating and weaned sows.

Effects of altering the dose and timing of triptorelin when given as an intravaginal gel for advancing and synchronizing ovulation in weaned sows

Previous studies have shown that triptorelin gel (TG) given intravaginally in gel form is effective for advancing the time of ovulation in weaned sows. Three experiments were performed to determine the effects of altering the dose and timing of administration of intravaginal TG for advancing and synchronizing ovulation in weaned sows. In all experiments, estrus was detected twice or three times daily and ultrasound was performed to determine ovulation at 8-hour intervals. In experiment 1, sows (n = 131) received intravaginal gel containing 0 (Placebo), 25, 100, or 200 μg of TG at 96 hours after weaning and sows were inseminated on each day of standing estrus. Wean-to-estrus interval and duration of estrus were correlated (P < 0.0001) with estrus duration longer in TG (P < 0.05) compared with Placebo. More sows ovulated (P < 0.001) by 48 hours after treatment with 200 (81%), 100 (64%), and 25 μg (63%) of TG compared with Placebo (42%). The farrowing rate and total pigs born did not differ (P > 0.10). In experiment 2, sows (n = 126) received 200 μg of TG at 72, 84, or 96 hours after weaning or were untreated (Control-96). Sows receiving TG were inseminated once 24 to 28 hours after treatment. Control-96 sows were inseminated on each day of standing estrus. Wean-to-estrus interval was not affected by treatment, but wean-to-ovulation interval was reduced (P < 0.05) by TG-72 and TG-84 compared with TG-96 and Control-96. More sows ovulated 40 hours after treatment (P < 0.001) with TG-72 (56.5%) and TG-84 (32.2%) compared with TG-96 and Control-96 (13%) and for all TG treatments 48 hours after treatment (64%) compared with Control-96 (34%, P < 0.05). The farrowing rate was lower (P < 0.05) for sows assigned to TG-72 and TG-84 compared with TG-96 and Control-96, whereas the number of liveborn pigs did not differ (P > 0.10). In experiment 3, sows (n = 113) were assigned to receive no treatment (Control), intravaginal gel alone (Placebo), or 200 μg of TG given intravaginally (OvuGel) at 96 hours after weaning. Wean-to-estrus interval did not differ, but the duration of estrus tended (P < 0.10) to be reduced with OvuGel compared with the other treatments. More sows ovulated (P < 0.001) by 48 hours after OvuGel treatment (79.1%) compared with Control (46.4%) and Placebo (37.9%) and by 56 hours (P < 0.05). The farrowing rate and the number of liveborn pigs did not differ among treatments. The results of these studies indicate that 200 μg of TG given intravaginally at 96 hours after weaning (OvuGel) synchronizes ovulation and results in fertility similar to Controls.

Efeito da ordem de parto e da perda de peso durante a lactação no desempenho reprodutivo subsequente de matrizes suínas

Investigou-se o efeito da ordem de parto (OP) e da perda de peso durante a lactação no desempenho reprodutivo de 666 matrizes suínas. Foram formadas três classes de OP (OP1, OP2 e OP3-5) e duas classes de percentual de perda de peso (≤1% e >1%) durante a lactação. Foram avaliados: taxa de parto, intervalo desmame-estro (IDE) e tamanho da leitegada subsequente. Houve interação de OP versus perda de peso na taxa de parto das fêmeas (P<0,05). As fêmeas OP1 e OP2 tiveram maior chance (P<0,05) de não parir na classe >1% de perda de peso. A maior perda de peso não foi um fator de risco para não parir na condição OP3-5 (P>0,05). Não houve interação de OP versus perda de peso (P>0,05) para IDE e total de leitões nascidos. Fêmeas OP1 apresentaram IDE mais longo e menor tamanho da leitegada no parto subsequente (P<0,05) do que fêmeas OP2 e OP3-5. As perdas corporais na lactação não influenciaram o IDE (P>0,05), mas reduziram o tamanho da leitegada subsequente (P<0,05). Conclui-se que maior perda de peso na lactação resulta em aumento de falhas reprodutivas nas fêmeas mais jovens e reduz o tamanho da leitegada subsequente em todas as OP.

Differences in maternal plane of nutrition and body condition during late gestation coupled with estrus synchronization at weaning do not result in differences in embryonic development at 4 days of gestation

This study was conducted to assess the effects of dietary energy in late pregnancy and hormone therapy at weaning on plasma metabolite profile, litter performance, reproductive parameters, and embryo viability in the second pregnancy. A total of 23 first-parity sows at 75 d of pregnancy were randomly allocated to 4 treatments. Treatments were factorial (2 × 2) combinations of 2 nutritional strategies [standard-energy feed (SEF) and high-energy feed (HEF)] and 2 hormone therapies [600 IU eCG and 2.5 mg swine LH 72 h later (HO) and no hormone (WH)]. Sows were weighed weekly from 75 d of pregnancy until 3 d before farrowing; 1 d after farrowing; 7, 14, and 21 d into lactation; and at weaning. Back fat (BF) was measured at 75 d of pregnancy, 3 d before farrowing, and at weaning. Average daily gain and ADFI were also calculated. Plasma metabolites were analyzed after 82, 89, 96, and 103 d of pregnancy, at farrowing, and after 7, 14, and 21 d of lactation. Embryo viability was assessed after 4.55 d of second pregnancy. During pregnancy, HEF-treated sows displayed greater BW (P < 0.05) compared with SEF-treated females, but no differences were observed during lactation. There were no differences in BW of the piglets caused by the treatments. High-energy-treated females showed superior BF (P > 0.05) in all periods; however, significant differences were detected only at the prefarrowing measurement (P < 0.05). No differences in ADFI were observed during lactation. The SEF group showed positive ADG, whereas the HEF group showed negative ADG (0.216 vs. -0.266 kg/d for SEF and HEF, respectively; P < 0.05). High-energy-treated sows presented greater concentrations of total cholesterol after 89 and 103 d of pregnancy and greater concentrations of high-density lipid cholesterol (HDL) after 89 and 96 d. At farrowing and 14 and 21 d of lactation, NEFA concentrations were greater (P < 0.05) in the HEF group. After hormone treatment, no differences were observed on weaning-to-estrus intervals and estrus duration. Greater mobilization of body reserves observed in the HEF group during lactation did not affect reproductive performance negatively, suggesting that metabolic status was adequate for the first lactational catabolism.

Cystic ovaries in intermittently-suckled sows: follicle growth and endocrine profiles

This paper presents follicle development and hormone profiles for sows with normal ovulation or cystic follicles during an intermittent-suckling (IS) regime that started at Day 14 of lactation. Sows were subjected to separation from their piglets during blocks of 6h or 12h. In total, 8 out of 52 sows developed cystic follicles; either full cystic ovaries (n=6) or partial ovulation (n=2). Increase in follicle size of these sows was similar to that of normal ovulating sows until pre-ovulatory size at Day 5 after the start of separation, but from then on became larger (P<0.05). LH surge was smaller or absent in sows that developed (partially) cystic ovaries (0.4 ± 0.1 vs 3.6 ± 0.3 ngmL(-1); P<0.01). Peak levels of oestradiol (E2) were similar but high E2 levels persisted in sows that developed (partly) cystic ovaries and duration of oestrus tended to be longer. The risk of developing (partly) cystic ovaries was higher when IS occurred in blocks of 6h versus 12h (33 vs 10%). In conclusion, the appearance of cystic ovaries at approximately Day 20 of ongoing lactation was related to an insufficient LH surge, as is also the case in non-lactating sows.

The intermittent suckling regimen in pigs: consequences for reproductive performance of sows

Intermittent suckling (IS), a system in which the sow and the piglets are separated for a number of hours per day during lactation, is put forward as a system that can increase piglet welfare around weaning and also induce lactational oestrus. To be of practical use, IS regimes need to result in a predictable oestrus and good reproductive performance. This review describes the effects of IS on sow reproductive performance. During IS, the LH pulsatility pattern switches to a high frequency, low amplitude release during separation, as is normally observed at weaning. In sows that ovulate during IS, LH pulsatility remains higher than in anovulatory sows. Around 90% of the IS sows show follicle growth up to pre-ovulatory size in a similar time period as sows post-weaning. Depending on the stage of lactation that IS commenced, 13% (day 21) to 21% (day 14) of the sows with pre-ovulatory follicles did not ovulate, but follicles either regressed or developed into cystic follicles. In the ovulatory IS sows oestradiol production is comparable but the LH surge is lower with an early start of IS (day 14) when compared with the weaned sows. Continuation of IS post-ovulation has negative effects on pregnancy rate, embryo development and progesterone levels. Factors related to lactation (e.g. a high metabolic clearance rate), may play a role in this. In conclusion, IS can result in a fertile oestrus when the timing of start of IS and duration of IS are taken into account, but for practical use IS regimes result in a too variable reproductive performance.

LH and FSH secretion, follicle development and oestradiol in sows ovulating or failing to ovulate in an intermittent suckling regimen

The present paper describes LH and FSH secretion, follicle development and ovulation in sows that were subjected to a limited nursing regimen. From Day 14 of lactation, 32 sows were separated from their piglets for 12 h every day (intermittent suckling; IS). Half the sows had boar contact during separation. Nine of 32 sows ovulated spontaneously within 14 days from initiation of IS. The frequency of LH pulses on the first day of IS tended to be higher in anovulatory sows (6.3 v. 4.2 pulses per 12 h; P < 0.10); other characteristics of LH secretion were similar to sows that ovulated. The characteristics of FSH secretion did not differ over the 8-h sampling period. Boar contact did not influence either LH and FSH secretion or the number of sows that ovulated. Up to 58% of anovulatory sows showed an increase in follicle size after initiation of IS and, 4 days after the initiation of IS, one-third still had follicles similar in size to those in ovulatory sows. However, the oestradiol concentration in anovulatory sows did not increase. We conclude that FSH and LH stimulation in anovulatory sows is not limiting for normal follicle development, but that ovarian follicles are not responsive to increased LH secretion.

Peri-oestrus hormone profiles and follicle growth in lactating sows with oestrus induced by intermittent suckling

This study describes follicle dynamics, endocrine profiles in multiparous sows with lactational oestrus compared with conventionally weaned sows (C). Lactational oestrus was induced by Intermittent Suckling (IS) with separation of sows and piglets for either 12 consecutive hours per day (IS12, n = 14) or twice per day for 6 h per occasion (IS6, n = 13) from day 14 of lactation onwards. Control sows (n = 23) were weaned at day 21 of lactation. Pre-ovulatory follicles (> or =6 mm) were observed in 100% of IS12, 92% of IS6 and 26% of C sows before day 21 of lactation and in the remaining 74% C sows within 7 days after weaning. All sows with pre-ovulatory follicles showed oestrus, but not all sows showed ovulation. Four IS6 sows and one IS12 sow developed cystic follicles of which two IS6 sows partially ovulated. Follicle growth, ovulation rate and time of ovulation were similar. E(2) levels tended to be higher in IS sows (p = 0.06), the pre-ovulatory LH surge tended to be lower in IS12 (5.1 +/- 1.7 ng/ml) than in C sows (8.4 +/- 5.0 ng/ml; p = 0.08) and P(4) levels were lower in IS12 and IS6 than in C sows (at 75 h after ovulation: 8.8 +/- 2.4 ng/ml vs 7.0 +/- 1.4 ng/ml vs 17.1 +/- 4.4 ng/ml; p < 0.01). In conclusion, sows with lactational oestrus induced by IS are similar to weaned sows in the timing of oestrus, early follicle development and ovulation rates, but the pre-ovulatory LH surge and post-ovulatory P(4) increase are lower.

Feeding level does not affect progesterone levels in intermittently suckled sows with lactational ovulation

The aim of this study was to examine whether the low post-ovulatory plasma P(4) levels found in intermittently suckled (IS) sows are related to the high feeding level during intermittent lactation. Multiparous sows (n=21) were separated from their piglets for 12h per day starting at day 14 of lactation until 6 days after ovulation. At day 28 of lactation, 9 sows had ovulated (spontaneous) and the remaining 12 sows were treated with PG600 (PG600-induced). At ovulation sows were allocated to either a high (H) feeding level (on average 6.5 kg) or a low (L) feeding level (high feeding level minus 2.5 kg) until 6 days after ovulation. Plasma P(4) levels were not affected by feeding level or type of ovulation (P>0.10), and neither were CL parameters, embryo survival rate and embryo development at day 30 of gestation. In conclusion, low levels of plasma P(4) were found in IS sows with lactational ovulation but these were not affected by feeding level during the first week after ovulation. Further studies are needed to investigate which factors cause the lower plasma P(4) levels in these sows.

Time of ovulation and reproductive performance over three parities after treatment of primiparous sows with PG600

Primiparous sows from a commercial pig farm in central Brazil were utilized to investigate the effect of post-weaning gonadotrophins (given during summer) on estrus, time of ovulation and reproductive performance over three parities. One group of sows (PG600) was treated with a combination of 400 IU equine chorionic gonadotrophin (eCG)+200 IU human chorionic gonadotrophin (hCG) (PG600) 24h after weaning (n=420), whereas the control group received saline (n=408). In a subset of sows (n=150), estrus was detected and time of ovulation was determined by transcutaneous ultrasound. Treatment with PG600 increased the percentage of primiparous sows in estrus within 10 days after weaning (94.8% versus 79.7%) and reduced the first weaning-to-estrus interval (5.3 days versus 8.0 days) relative to control sows (P<0.05). Although the duration of estrus was longer (P<0.05) in sows given PG600 (65.7 h versus 61.0 h), the interval from estrus to ovulation was not different (P>0.05) between PG600 and control sows (46.6 h versus 43.3 h). Treatment with PG600 did not affect (P>0.05) rates of return-to-estrus and farrowing over three parities, but it increased the number of total piglets born (P<0.05) in the second parity (11.2 versus 10.4), thereby minimizing the magnitude of second-litter syndrome. Culling rates from the first to the fourth parity were 26.7 and 24.5% (P>0.05) for PG600 and control sows, respectively. In conclusion, PG600 given 24 h after the first weaning reduced the weaning-to-estrus interval and increased the size of the second litter.

The effect of feeding strategy during the pre-follicular phase on subsequent follicular development in the pig

In female pigs feeding level has important effects on reproductive performance. This review is focused on the follicular development after low and high feeding levels during the luteal phase in gilts. Although aspects of diet composition seem to have a role in regulating reproductive performance, the most important aspect appears to be the plane of nutrition. Similar effects are described during lactation in primiparous sows, when their metabolism is challenged to its maximum. Also in this situation feeding level clearly affects weaning to oestrus interval, follicular development, oocyte maturation, ovulation rate and subsequent embryonic survival.

Factors regulating ovarian function in pigs

The hormonal interactions of the hypothalamic-pituitary-ovarian-uterine axis are accountable for a normal reproduction in female pigs. It is of importance to have knowledge of estrous symptoms and hormonal profiles around ovulation. The introduction of the transrectal ultrasonography in sows has given us the possibility to study ovarian activity in conscious animals and relate the timing of estrus to ovulation. Combining this technique with measuring of several hormones like luteinizing hormone (LH), follicle-stimulating hormone (FSH), inhibin, estradiol, progesterone, insulin-like growth hormone I (IGF-I), prostaglandin F2alpha (PGF2alpha) metabolite, oxytocin, facilitate our knowledge about the sequence of ovarian events. Evidence suggests that activation of the hypothalamic-pituitary-adrenal axis may hamper the normal gonadotropin secretion and in consequence, the ovarian function. The metabolic status during lactation, weaning of piglets and social stress might affect onset of ovarian activity and the related estrous behavior. The role of seminal plasma, artificial insemination and presence of the boar might also be included as factors regulating the temporal kinetics of ovulation, corpus luteum development, uterine function and steroid production in the ovary. Studies using a simulated stress by means of adrenocorticotrophic hormone (ACTH) administration or food deprivation are tools in understanding how the ovary is susceptible to impairment. The intention of this paper is to review current knowledge concerning the endocrine aspects of normal and stress-influenced ovarian function in pigs.

Factors affecting temporal relationships between estrus and ovulation in commercial sow farms

The main objective was to examine effects of season, parity, genotype, lactation length, and weaning-to-estrus interval on duration of estrus (DE) and onset of estrus-to-ovulation interval (EOI) in three sow farms. Detection of estrus and ovulation by the back-pressure test and transabdominal ultrasonography, respectively, were performed every 6 h from day 2-10 postweaning in 535 sows (approximately 89 per farm per season). The average weaning-to-estrus interval, DE, and EOI of the 501 sows that returned to estrus by day 10 postweaning were 4.6+/-0.1 days, 55.2+/-0.5 h, and 41.8+/-0.5 h, respectively. Farm x season (P<0.01), parity x season (P <0.05), and farm x weaning-to-estrus interval (P<0.05) interactions for DE and EOI were detected. Sows weaned in the summer had an 8 h longer (P<0.001) DE and EOI than those weaned in the spring on farms 1 and 3. On farm 2 however, DE and EOI did not differ (P=0.09) in sows weaned in summer versus spring. On each farm, parity 3 and > or =4 sows had a 4.5 h longer (P<0.05) DE and EOI than parity 1 and 2 sows in the summer, but there were no differences (P>0.11) in DE or EOI among parity classes in the spring. There was a linear decrease of DE (P<0.001) and EOI (P<0.05) as weaning-to-estrus interval increased from the 3 to the > or =7 day class on each farm. However, the range of weaning-to-estrus interval that exhibited a stepwise decrease of DE and EOI was narrower on farm 1 (3-5 days) than farms 2 and 3 (3-6 days). Only farms 1 and 3 had multiple genotypes. Genotype did not affect (P>0.14) DE on either farm, but the EOI of genotype B was 4 h shorter (P<0.05) than genotype C on farm 1. On each farm, DE decreased linearly (P<0.01) as lactation length increased from < or =13 to > or =20 days. In general, factors that affected EOI also affected (P<0.05) the percentage of inseminations that occurred within 24 h pre- to 3h post-ovulation. These data indicate that factors other than weaning-to-estrus interval, such as season and parity, can significantly alter DE and EOI. However, the effects of season and weaning-to-estrus interval on DE and EOI can be inconsistent among different farms.