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This study was carried out to evaluate the effects of the sperm cell dose and semen backflow on the pregnancy rate and number of embryos of sows inseminated once at 0-24 h before ovulation, using an intrauterine technique. The results were analysed from a total of 211 sows assigned to three groups inseminated with doses of 0.25 x 10(9) (T1), 0.5 x 10(9) (T2) and 1.0 x 10(9) (T3) spermatozoa. Semen backflow was observed in 95% of the females (143/151) evaluated for this purpose. The percentage of semen backflow is close to two-third of the volume and the percentage of sperm is around 15% of the infused sperm dose. Intrauterine insemination can be successfully performed provided that at least 0.5 billion of sperm cell dose is infused at an interval of 0-24 h before ovulation.

The aim of this study was to evaluate the influence of sow body reserves at weaning and body reserve losses during the first lactation on the second litter size (SLS). A number of 1222 females which reached the second parity without failures such as return to estrus after insemination, abortion or failure to farrow, were analyzed. Measurements of body weight (BW), backfat thickness (BT) and body condition score (BCS) were taken within 24 h after farrowing and on the weaning day. Body fat and body protein mass at first weaning and their losses during lactation were estimated based on BW and BT. The lactation length, the weaningto-estrus interval (WEI) and the number of weaned piglets were on average 19.6 days, 5.5 days and 10.5 piglets, respectively. During lactation, the sows had on average a reduction of 18.6 kg (9%) in BW, 3.1 mm in BT and 0.8 in BCS. In the first and second farrowings there were on average 12.4 and 9.7 total born piglets, respectively. Females with more than 178 kg, BT ≥ 16 mm or body fat ≥ 21% at weaning had a higher SLS (P b 0.05). Sows with a lipid:protein ratio at weaning N 1.40 had more piglets (P b 0.05) than those with a ratio b 1.22. Females in the categories of high BCS (≥ 3.0) or high body protein (N 15%) at weaning had more piglets in the second birth compared to females with a BCS ≤ 2 or body protein ≤ 14% (P b 0.05). Smaller SLS (P b 0.05) was observed in sows with a weight loss N 10%, body protein loss N 10%, body fat loss N 20% or a BCS loss ≥ 1.0 point. When sows were categorized into two groups of BW at farrowing-low (167-206 kg) or high (207-245 kg), higher SLS (P b 0.05) was observed in sows losing more than 8% of BW or 9% of protein mass. The loss of b 22% in fat mass increased the SLS in sows of high BW (P b 0.05) but not in those of low BW at farrowing. In conclusion, SLS is affected by absolute body reserves at weaning and by their mobilization during lactation indicating the importance of achieving an adequate body condition at parturition and of optimizing the feed intake in lactating primiparous sows.

Pre-weaning piglet mortality represents significant economic losses, and approximately half of this mortality occurs within the first 3 days after birth. Factors involved in postnatal mortality can also be associated with a poor growth performance until weaning. The aim of this study was to evaluate the effect of some variables measured right after birth on piglet survival during the first week of life and growth performance until weaning. Piglets included in the analysis (n=612) were born from 3 to 5 parity sows. Piglets were monitored for blood oxygen saturation (SatO2), heart rate (HR), blood glucose concentration, rectal temperature at birth (RT0 h) and at 24h after birth (RT24 h). Genetic line, birth following or not an obstetric intervention, birth order, sex, skin color, integrity of the umbilical cord, and time elapsed from birth until first attempts to stand were also recorded. Piglets were weighed at birth (BW), and at 7, 14 and 21 days after birth in order to evaluate their postnatal development. Cumulative mortality rates were 3.3%, 5.4% and 8.7% at 3, 7 and 21 days after birth, respectively. Body temperature at birth (RT0 h) did not affect (P>0.05) the survival nor the piglet growth performance. Piglets with cyanotic skin and those that took more than 5 min to stand showed higher chance of mortality (P<0.05) compared to normal skin piglets and to piglets which stood before 1 min, respectively. Piglets with broken umbilical cord had higher odds (P<0.05) of mortality up to 3 days after birth, respectively. Higher odds (P<0.05) of mortality up to 3 or 7 days were associated with later birth order (>9), low BW (<1275g), low (24-30 mg/dl) and high (45-162 mg/dl) blood glucose concentrations, or low RT24 h (<38.1°C). Piglets with BW<1545 g, low RT24 h (<38.6°C) and female piglets had higher odds of a low weight at weaning (P<0.05). Among the factors studied, cyanotic skin, delay for standing, broken umbilical cord, high birth order, low BW, low RT24 h, and both low and high blood glucose concentrations are indicators of a lower ability of piglets to survive during the first week after birth. The growth performance until weaning is compromised in piglets with a lower BW, a lower RT24 h and if they are female pigs.

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