Age, body weight and backfat thickness at first observed oestrus in crossbred Landrace x Yorkshire gilts, seasonal variations and their influence on subsequence reproductive performance

The objective of the present study was to investigate puberty attainment in crossbred Landrace x Yorkshire (LY) gilts reared under tropical conditions and their subsequent reproductive performance. This study was carried out in a 2400-sow herd over a 1-year period. A total of 696 crossbred LY replacement gilts were included. Faecal samples from 214 gilts were collected to determine the faecal progesterone profiles around the time of first oestrus. Solid-phase 125I-radioimmunoassay was used to determine the progesterone concentrations in the faecal extract. The gilts entered the herd at an average age of 177.5 +/- 12.6 days, 95.7 +/- 10.2 kg body weight (BW) and a backfat thickness (BF) of 12.0 +/- 2.9 mm. On average, the gilts expressed first standing oestrus at 195 days of age, 106 kg of BW and a BF of 13.0 mm. The interval from entry to the gilt pool to the first observed oestrus (EOI) was 24.4 +/- 18.0 days (range 0-88 days). The hormonal profile indicated that the gilts that actually ovulated during the first observed oestrus was 34% (group A), the gilts that had ovulated before the first observed oestrus was 21% (group B) and the gilts that did not ovulate during the first observed oestrus was 45% (group C). During summer the proportion of group A gilts was significantly lower than during the winter and the rainy seasons (P < 0.05). The BW of gilts at entry significantly correlated with the BF at entry (r = 0.31, P < 0.001), the age at entry (r = 0.47, P < 0.001), the BW at first oestrus (r = 0.65, P < 0.001) and the BF at first oestrus (r = 0.33, P < 0.001). An increase of BW at entry of 1 kg resulted in a decrease of EOI of 0.28 days. The age, BW and BF of gilts at the first observed oestrus significantly influenced the total number of piglets born per litter (TB) and the number of piglets born alive per litter (BA) in the first three parities. Gilts expressing their first oestrus between 181 and 200 days had a significantly larger TB than gilts that expressed first oestrus between 150 and 180 days (P = 0.03) and between 201 and 220 days (P = 0.003). Gilts that showed first oestrus between 110.1 and 120.0 kg had a larger TB and BA than gilts that showed first oestrus between 80.0 and 100.0 kg (P < 0.05). Gilts that showed first oestrus with a BF between 13.1 and 15.0 mm had a larger TB and BA than gilts that showed first oestrus with a BF between 11.1 and 13.0 mm (P < 0.05). Group A gilts had a significantly larger TB than group B (10.5 piglets/L versus 9.4 piglets/L, P = 0.02), while farrowing rate (FR) did not differ significantly among groups A, B and C (78.1, 76.9 and 77.6%, respectively). Gilts that farrowed in the summer had a larger TB and BA than gilts that farrowed in the winter (TB, P = 0.03; BA, P = 0.09) and the rainy season (TB, P = 0.006; BA, P = 0.003). In conclusion, LY gilts reared under tropical conditions expressed first standing oestrus at 195 days of age, 106 kg BW and a BF of 13.0 mm. Under field conditions, 21% of the gilts with an observed oestrus had ovulated. The proportion of gilts that showed first oestrus and ovulated normally was lowest during the summer. The age, BW and BF at first observed oestrus influenced subsequent reproductive performance over the first three parities. The mean litter size (TB and BA) in the first three parities were highest in gilts that had a first observed oestrus between 181 and 200 days with 110.1-120.0 kg BW and 13.1-15.0 mm BF.     

Effect of insemination of estrus-induced prepuberal gilts on ensuing reproductive performance and body weight

Prepuberal gilts reared and managed to 85-90 kg live weight in a common system were allocated at random to one of three first-mating treatments in an experiment conducted over a period of more than 5 years. In two of the treatments, gilts received a single i.m. injection of 400 IU equine chorionic gonadotropin (eCG) and 200 IU human chorionic gonadotropin (hCG) (PG600; Intervet) and were either inseminated 4 and 5 days later on a fixed-time basis regardless of oestrus (treatment A), or at the second oestrus following treatment (treatment B). The third group of gilts remained untreated and was inseminated on the first spontaneous oestrus (treatment C). Thereafter, all gilts were managed in the same way and those observed in oestrus were re-inseminated. Significantly more gilts returned to oestrus after the first service in treatment A (35%) than in treatment B and C (12 and 17%, respectively; P<0.01). Gilts farrowed to the first or repeat inseminations at a significantly younger age (P<0.01) in treatment A (304 days) than treatment B (324 days) and C (320 days). The age difference at farrowing remained in surviving gilts at the end of their third parity. The first farrowing performance of the gilts was significantly affected by treatment in terms of litter size at birth (A 7.0, B 8.4 and C 8.3 live piglets per gilt; P<0.01), litter size at weaning (A 6.2, B 7.2 and C 7.2 live piglets per gilt, P<0.05), and piglet birth weight (A 1.4, B 1.3 and C 1.3 kg; P<0.05) but piglet survival rate and weaning weight were not affected by treatment. The live weights of the gilts were significantly different between the treatments at first insemination (A 95.7, B 106.5 and C 109.2 kg; P<0.01) but not when the first litter was weaned (A 133.6, B 135.1 and C 136.6; P>0.05). After the first farrowing there were no differences between the treatments in terms of the survival rate, productive or reproductive performance of the gilts/sows and their offspring. Without conducting a detailed cost-benefit-calculation it was deduced that, from an economical point of view, differences between treatment A and treatments B and C are negligible because the savings associated with farrowing at a younger age on this treatment just about compensated for any additional costs associated with the treatment and the lower number of piglets born at the first farrowing.     

Factors influencing age at first mating in purebred Swedish Landrace and Swedish Yorkshire gilts

The aim of the present study was to retrospectively analyze causes of the variation in age at first mating in Swedish Landrace (L) and Swedish Yorkshire (Y) gilts. Production traits including growth rate from birth to 100kg body weight and backfat thickness at 100kg body weight were also studied. Data analyzed were obtained from 11 L and 11 Y nucleus herds and included gilts born during a 5-year-period from October 1993 until September 1998. The complete data set included information on 14,761 gilts (6997 L and 7764 Y). Traits analyzed included age of gilt at first mating, growth rate and backfat thickness. Seven statistical models were used for analyzing the data. Factors included were gilt breed, birth month, parity number and size of the litter in which the gilt was born as well as their interactions. Compared with Y gilts, L gilts grew faster (571 versus 556 g/day; P<0.001), had a thinner backfat (11.9 versus 12. 3mm; P<0.001) at 100kg body weight and were 12 days younger at first mating (237 versus 249 days; P<0.001). Birth month significantly (P<0.001) influenced age at first mating, growth rate and backfat thickness. Gilts born from smaller litters were mated at younger age than gilts born from larger litters even when age at first mating was adjusted for the effect of growth rate and backfat thickness. Growth rate of the gilts decreased when 'birth litter size' increased. Gilts born from primiparous sows grew slower, had a thinner backfat at 100kg body weight and were older at first mating compared with gilts born from multiparous sows. Gilts with a higher growth rate were younger at first mating than those with a lower growth rate. Gilts with a thicker backfat at 100kg body weight were mated earlier than the thin ones. However, the effect of growth rate on age at first mating was more pronounced in the gilts with a thinner backfat rather than the ones with a thicker backfat.     

The involvement of boar submaxillary salivary gland secretions in boar-induced precocious puberty attainment in the gilt

The involvement of secretions from boar submaxillary salivary glands in mediating the induction of precocious puberty in the gilt was investigated as follows. Forty-eight Large White × (Large White × Landrace) prepubertal gilts from 12 litters were randomly allocated within litters by weight, to four treatment groups of six, in two replicates, at 145 days of age. Treatments commencing at a mean group age of 165 days, were: (1) control (no boar exposure); (2) gilts exposed to a mature sialectomised boar (submaxillary salivary glands were removed at 9 weeks of age); (3) gilts exposed to a mature sham-operated boar; (4) gilts exposed to a mature unoperated boar.Boar exposure occurred for 30 min per day for 75 days, or until pubertal oestrus was observed. Gilts showing pubertal oestrus were removed and slaughtered. Ovaries were examined to confirm reproductive status. Gilts failing to exhibit oestrus by 240 days of age were slaughtered and nominally ascribed a pubertal age of 245 days. Age at puberty was significantly earlier in all three boar-exposed treatments than in the control treatment (P<0.05 for treatments 2 and 3, P<0.001 for treatment 4; median ages at puberty being 227.0, 203.5 , 202.0 and 179.0 days for treatments 1 to 4 respectively). No frothy saliva was ever produced by the sialectomised boar, and chromatographic analysis of saliva produced by the sham-operated boar during mating revealed very low levels of 16-androstene pheromones, while levels in the unoperated boar's saliva were normal. These results provide further evidence for an important role of boar salivary pheromones in the induction of precocious puberty attainment in the gilt.     

The effects of PG600 and boar exposure on oestrus detection and potential litter size following mating at either the induced (pubertal) or second oestrus

Within gilt pools, incidences of delayed puberty attainment, failure to exhibit regular oestrous cycles and low first litter size are often high. Boar exposure is an effective method of accelerating puberty; however, the timing of gilt response can vary greatly. Although, PG600 (400 IU of PMSG and 200 IU of hCG; Intervet) can induce a rapid and synchronous ovulatory response, thus providing an alternative to boar contact, the quality of the response is often variable. This study compared the effect of PG600, either alone (NBC) or in conjunction with boar exposure (BC), on puberty attainment and maintenance of oestrous cyclicity. The effects of first mating these gilts at the hormonally induced (pubertal) or second oestrus on ovulation rate and early embryo survival were also studied. Eighty Large White cross terminal (Duroc) line gilts were used in this study. The study was conducted in two blocks, with 10 gilts allocated to each of the four treatments in each block. Gilts were artificially inseminated at the allocated oestrus, with the reproductive tracts collected at 26.5+/-0.29 days after first mating (mean+/-S.E.M.), and the number of corpora lutea and viable embryos recorded. Mean days-to-puberty was significantly reduced (P<0.05) when gilts received both PG600 and boar exposure as opposed to PG600 alone (5.7+/-0.15 versus 6.9+/-0.37 days; P<0.01). The proportion of gilts exhibiting an ovulatory response to PG600 was similar for the BC and NBC treatment groups (0.88 and 0.84); however, the proportion of gilts exhibiting visible signs of oestrus in response to PG600 was significantly higher for the BC compared to the NBC treatment groups (0.81 versus 0.49; P<0.05). Boar contact resulted in a numerical, but not significant, increase in the proportion of gilts exhibited a second oestrus (1.00 versus 0.76). There was no significant effect of boar contact on ovulation rate, embryo number or survival. Although ovulation rate was unaffected by oestrus at mating, embryo number was significantly increased (P<0.05) following mating at the second compared to the first oestrus (11.2+/-0.96 versus 7.8+/-1.17). In conclusion, the current data indicate that the timing of puberty attainment and oestrus detection are significantly improved when PG600 treated gilts receive full boar contact. Further, it is evident that mating gilts at their second as opposed to the hormonally induced oestrus significantly increases embryo number at day 26 post-mating.     

Clinical,Morphological and Endocrinological Studies in Gilts with Delayed Puberty

Thirty-six gilts which had not shown oestrus at about 8 months of age or more were transported from the pig research station to the clinic, a journey of 12 km. The gilts were examined by laparoscopy and those which had only small follicles in the ovaries were catheterized and placed in pens, with sexually mature boars kept in adjacent pens. Oestrus detection was done twice daily and blood was sampled three times a day. After 7 days the laparoscopy was repeated and gilts which still had only small follicles in their ovaries were given 250 μg GnRH intravenously the following day. Blood samples were taken frequently before and after GnRH treatment. One week. after administration of GnRH the ovaries were inspected by laparoscopy once more. The first laparoscopic examination showed that 42 % of the gilts were sexually mature. One gilt had no uterus or ovaries. Twenty gilts had only small follicles in the ovaries and fourteen of these gilts showed ovulatory oestrus 5.5 days (4-7.5 days) after arrival. In these fourteen gilts a rise in the oestradiol-17B level (>30 pmol/1) was seen at an average time of 1.9 days and a rise in LH (preovulatory peak) was seen at an averaged 4.5 days after the start of blood sampling. Six gilts were given 250 ug GnRH. An immediate rise in LH could be seen in all the gilts (mean peak level was 6.18 μg/l) and the elevated levels had a duration of 4 hours. None of the GnRH-treated gilts responded with oestrus symptoms or increased ovarian activity.     

Steroidome and metabolome analysis in gilt saliva to identify potential biomarkers of boar effect receptivity

Optimal management of gilt reproduction requires oestrus synchronization. Hormonal treatments are used for this purpose, but there is a growing demand for non-hormonal alternatives, especially in organic farms. The boar effect is an important alternative opportunity to induce and synchronize oestrus without hormones. Before puberty, gilts exhibit a ‘waiting period’ during which boar exposure could induce and synchronize the first ovulation. We searched for salivary biomarkers of this period of boar effect receptivity to improve detection of the gilts to stimulate with the perspective of enhancing the efficacy of the boar effect. Saliva samples were collected from 30 Large-White × Landrace crossbred gilts between 140 and 175 days of age. Gilts were exposed twice a day to a boar and subjected to oestrus detection from 150 to 175 days of age. Among the 30 gilts, 10 were detected in oestrus 4 to 7 days after the first introduction of the boar and were considered receptive to the boar effect, 14 were detected in oestrus more than 8 days after first boar contact, and six did not show oestrus and were considered non-receptive. Saliva samples from six receptive and six non-receptive gilts were analyzed for steroidome and for metabolome using gas chromatography coupled to tandem mass spectrometry and ¹H nuclear magnetic resonance spectroscopy, respectively. Four saliva samples per gilt were analyzed: 25 days and 11 days before boar introduction, the day of boar introduction, 3 days later for receptive gilts or 7 days later for non-receptive gilts. Twenty-nine steroids and 31 metabolites were detected in gilt saliva. Salivary concentrations of six steroids and three metabolites were significantly different between receptive and non-receptive gilts: progesterone and glycolate 25 days before boar introduction, 3α5β20α- and 3β5α20β-hexahydroprogesterone, dehydroepiandrosterone, androstenediol, succinate, and butyrate 11 days before boar introduction, and 3β5α-tetrahydroprogesterone on the day of boar introduction. Thus, nine potential salivary biomarkers of boar effect receptivity were identified in our experimental conditions. Further studies with higher numbers of gilts and salivary sampling points are necessary to ascertain their reliability.     

Attainment of puberty in female pigs: Clinical appearance and patterns of progesterone,oestradiol-17β and LH

The object of the study was to investigate the clinical and endocrine patterns of progesterone, oestradiol-17β and LH during the peripubertal period in female pigs. Crossbred gilts were penned in groups at an age of 10–12 weeks and boars were kept in adjacent pens during the entire experimental period. Daily oestrous checks started at 4.5 months of age and the gilts were slaughtered after their third heat. At the age of 4.5–5 months a permanent catheter was inserted in the cephalic vein and blood samples were collected from the gilts once daily until either the first or second oestrus. In three gilts hourly blood samples were taken during their first and second oestrus, beginning at early pro-oestrus.The gilts showed their first oestrus at the average age of 183 days. No corpora lutea from earlier ovulations were observed in gilts laparoscoped after their first detected oestrus. During the 30-day period before first oestrus the mean daily progesterone levels varied between 32 and 329 pmol/l. The average levels of oestradiol-17β varied between 15.6 and 30.8 pmol/l. There was no tendency for the oestradiol-17β level to rise before onset of first pro-oestrus. The average levels of LH varied between 0.15 and 0.94 μg/l. The statistical analyses revealed no significant relationship between the level of the hormones studied and onset of first oestrus. The mean progesterone levels during the first and second oestrous cycles were almost identical, however. Oestradiol-17β increased gradually during pro-oestrus, reaching maximum levels before onset of oestrus and thereafter decreasing sharply to values around 30 pmol/l. The oestradiol-17β levels were higher at the second than at the first pro-oestrous period. The concentrations of plasma LH rose sharply with declining plasma levels of oestradiol-17β. The duration of elevated plasma LH levels (> 1 μg/l) was, on average, 26 h and the LH levels were higher during the first oestrus than during the second oestrus. The first rise in progesterone was observed 11–29 h after the LH levels had decreased to concentrations below 1 μg/l.     

Effects of a diet containing fusarium toxins on the fertility of gilts and on bulbourethral gland weight in barrows

Nine gilts weighing 80 kg at the beginning of the trial were fed a mycotoxin contaminated diet containing 2 mg deoxynivalenol (DON) and 0.4 mg zearalenone (ZON) per kg (Diet M). Their daily weight gain until 103 kg BW was reduced in comparison to the nine control animals fed an uncontaminated diet (Diet C) (763 vs. 912 g; p = 0.02). There was no treatment effect on the age at first observed oestrus. Seven and eight gilts receiving Diet M and C, respectively, became pregnant after being mated once or being again mated three weeks later. The examination of the uteri of gilts slaughtered 35–61 days after mating showed that the exposure to DON and ZON had no effect on the number of foetuses per gilt (p = 0.54), but increased their growth rate (p = 0.003). Thus, low dietary DON and ZON levels had no negative effects on the reproductive parameters examined. The hypothesis that the bulbourethral gland weight of barrows can be used for the bioassay of low dietary ZON levels was rejected since feeding Diet M from 80–103 kg BW did not increase the weight of that accessory sex gland (p = 0.51).     

Estimation of genetic parameters for BW and body measurements in Brahman cattle

Body weight and body measurements are commonly used to represent growth and measured at several growth stages in beef cattle. Those economically important traits should be genetically improved. To achieve breeding programs, genetic parameters are prerequisite, as they are needed for designing and predicting outcomes of breeding programs, as well as estimating of breeding values. (Co)variance components were estimated for BW and body measurements on Brahman cattle born between 1990 and 2016 from 17 research herds across Thailand. The traits measured were BW, heart girth (GR), hip height (HH) and body length (BL) and were measured at birth, 200 days, 400 days and 600 days of age. The number of records varied between traits from 18 890 for birth BW to 876 for GR at 600 days. Estimation of variance components was performed using restricted maximum likelihood using univariate and multivariate animal models. Pre-weaning traits were influenced by genetic and/or permanent environmental effects of the dam, except for BL. Heritability estimates from birth to 600 days of age ranged from 0.28±0.01 to 0.50±0.06 for BW, 0.27±0.01 to 0.43±0.09 for GR, 0.28±0.01 to 0.58±0.08 for HH and 0.34±0.01 to 0.51±0.08 for BL using univariate analysis. Heritability estimates for the traits studied increased with age. A similar trend was observed for the phenotypic and genetic correlations between subsequent BW and body measurements. A positive correlation was observed between different traits measured at a similar age, ranging from 0.22±0.01 to 0.72±0.01 for the phenotypic correlation and 0.25±0.04 to 0.97±0.11 for the genetic correlation. Also, a positive correlation was observed for similar traits across different age classes ranging from 0.07±0.03 to 0.76±0.02 for the phenotypic correlation and 0.24±0.11 to 0.92±0.05 for the genetic correlation. Therefore, all correlations between body measurements at the same age and across age classes were positive. The results show the potential improvement of growth traits in Brahman cattle, and those traits can be improved simultaneously under the same breeding program.     

Genetic and phenotypic parameters of body weight in West African Dwarf goat and Djallonké sheep

The International Trypanotolerance Centre's small ruminant breeding programme was initiated in 1995. The aim was to increase the efficiency of meat production and the trypanotolerance of the animals (sheep and goat). To achieve that goal, selection was based on estimated breeding values for daily weight gain from 4 to 12 months of age measured on trypanotolerance challenge. The purpose of this study was to estimate genetic parameters for growth traits and to evaluate genetic trends in West African Dwarf goat and Djallonké sheep resulting from the breeding programme under a low input production environment. Data for West African Dwarf goat and Djallonké sheep included birth weight (BW), weaning weight (W120), yearling weight (W360), pre-weaning (GR0–4) and post-weaning (GR4–12) growth rate. The data were analysed using an animal model that accounted for fixed effects of sex, year of birth, season of birth, parity of the dam, type of birth and the interaction year by season of birth. Estimates of heritability for BW, W120, W360, GR0–4 and GR4–12 were 0.5, 0.43, 0.30, 0.32 and 0.11 for goats and 0.39, 0.54, 0.21, 0.54 and 0.23 for sheep, respectively. The genetic correlation between BW and W120 was high for goats (0.74) and moderate for sheep (0.47). Genetic correlations between W120 and GR4–12 were high (0.92) for goats and moderate (0.49) for sheep. Between GR0–4 and BW the correlation was positive but low for sheep (0.26) and moderate for goats (0.60). Positive trends were found in mean estimated breeding values for animals born in the period 1995–2002 which demonstrated the effectiveness of the implemented breeding programs.     

Mixing gilts in early pregnancy does not affect embryo survival

There is general acceptance that mixing sows during the first 3 weeks of gestation is detrimental to embryo development and survival. However, there is a paucity of data describing the influence of group housing and remixing during the first 14 days of gestation on pregnancy outcomes. Using 96 purebred maternal (Large White)/terminal (Duroc) line gilts, the current study determined the effects of regrouping, and the timing of regrouping, during the pre-implantation period on embryo mortality. The study was conducted in 2 blocks, with 12 gilts allocated to each of 4 treatments in each block. At 175 days of age, the combination of PG600 and 20 min of daily physical boar contact was used to stimulate puberty, with boar contact resuming 12 days after first detection of oestrus and gilts receiving two artificial inseminations (AIs), 24 h apart, at their second oestrus. After their first AI gilts were allocated to one of four treatment groups (n=12 gilts/treatment). Gilts in one treatment group were housed individually in stalls (STALL). The remaining gilts continued to be housed in their pre-AI groups and were either not remixed (NOMIX), or remixed to form new groups on day 3/4 (RMIXD3/4) or day 8/9 (RMIXD8/9) of gestation (day 0=day of first detection of second oestrus and first insemination). Group-housed gilts were housed in groups of 6, with a space allowance of 2.4 m2/gilt. All gilts were fed once a day (2.2 kg/gilt). Reproductive tracts were collected on day 26.6+/-0.13 of gestation, and the number of corpora lutea (CL) and viable embryos counted. Pregnancy rate was similar across all treatments, averaging 94.5% across the four treatment groups. The number of embryos present on day 26 of gestation was unaffected by housing treatments (P>0.05); gilts in the STALL, NOMIX, RMIXD3/4 and RMIXD8/9 groups possessed 13.2+/-0.67, 12.9+/-0.66, 14.1+/-0.46 and 13.8+/-0.57 embryos, respectively. Similarly, embryo survival rates were 0.91+/-0.04, 0.85+/-0.04, 0.91+/-0.02 and 0.87+/-0.05 for the STALL, NOMIX, RMIXD3.4 and RMIXD8/9 groups, respectively (P>0.05). In conclusion, the current data indicate that individually housing gilts immediately after their first AI does not improve embryo survival. There also appear to be no adverse effects on embryo development or survival when group-housed, mated gilts are remixed during the first 10 days of gestation.     

Effect of birth litter size, birth parity number, growth rate, backfat thickness and age at first mating of gilts on their reproductive performance as sows

The present study was performed to evaluate retrospectively the influence of birth litter size, birth parity number, performance test parameters (growth rate from birth to 100kg body weight and backfat thickness at 100kg body weight) and age at first mating (AFM) of gilts on their reproductive performance as sows. Traits analysed included remating rate in gilts (RRG), litter size, weaning-to-first-service interval (WSI), remating rate in sows and farrowing rate (FR). Data were collected from 11 Swedish Landrace (L) and 8 Swedish Yorkshire (Y) nucleus herds and included 20712 farrowing records from sow parities 1-5. Sows that farrowed for the first time during 1993-1997, having complete records of performance test and AFM, were followed up to investigate their subsequent reproductive performance until their last farrowing in 1999. Analysis of variance and multiple regression were applied to continuous data. Logistic regression was applied to categorical data. The analyses were based on the same animals and the records were split into six groups of females, i.e. gilts, primiparous sows, and sows in parities 2-5, respectively. Each additional piglet in the litter in which the gilt was born was associated with an increase of her own litter size of between 0.07 and 0.1 piglets per litter (P<0.001). Gilts born from sow parity 1 had a longer WSI as primiparous sows compared with gilts born from sow parity 4 (0.3 days; P<0.05) or parity 5 (0.4 days; P<0.01). Gilts with a higher growth rate of up to 100kg body weight had a larger litter size (all parities 1-5; P<0.05), shorter WSI (all parities 1-5; P<0.05) and higher FR (parities 2 and 5; P<0.05) than gilts with a lower growth rate. Gilts with a high backfat thickness at 100kg body weight had a shorter WSI as primiparous sows (P<0.001) compared with low backfat gilts, and 0.1 piglets per litter more as second parity sows (P<0.01). A 10 day increase in AFM resulted in an increase in litter size of about 0.1 piglet for primiparous sows (P<0.001) and a decrease (P<0.05) for sow parities 4 and 5.     

Nutrition level and season of birth do not modify puberty of Payoya goat kids

This study analysed the effect of level of nutrition and date of birth (age) on the onset of puberty in Payoya she-kids born in autumn (November) or in winter (February). Two experiments were conducted to examine pubertal events at the onset of puberty. For each date of birth (age), two experimental groups were used, differing on the level of nutrition. Groups were balanced for live weight (LW) and body condition score (BCS). For the first experiment (goat kids born in autumn), 27 Payoya she-kids were used: high-nutrition group (H1, n = 13) and control group (C1, n = 14). For the second experiment (goat kids born in winter), 25 Payoya she-kids were used: high-nutrition group (H2, n = 13) and control group (C2, n = 12). In both experiments, the level of feeding was adjusted weekly according to LW so that the animals would gain about 50 and 100 g per day for C and H groups, respectively. Oestrus was tested daily using young aproned bucks. Ovulation rate was assessed by laparoscopy 7 days after identification of oestrus. Plasma samples were obtained weekly for progesterone assay. LW and BCS were recorded weekly. No effect of nutrition level or birth date (Experiment 1 v. 2) on the date of the first ovarian activity or the first detected oestrus was observed. No effect of nutrition on LW or BCS at the first detected oestrus was observed. Birth date influenced significantly the LW of the animals at the onset of ovarian activity or first oestrus (P < 0.001). Irregular sexual activity was frequently observed before the first oestrus (74.7% and 48.0% of the first reproductive activity was irregular for Experiments 1 and 2, respectively). No effect of nutrition level or birth date on ovulation rate was observed. Ovulation rate at first oestrus was influenced by LW in November-born goat kids (1.06 ± 0.06 v. 1.67 ± 0.21 corpora lutea for LW < 30 and 30 kg, respectively, P < 0.01). These results demonstrate that the age at puberty was very dependent upon the season of birth in Payoya goat kids, and that there could be some benefit in breeding November-born goat kids at a higher LW to obtain a higher prolificacy at the first kidding as a consequence of a higher ovulation rate at puberty.     

Productive performance, carcass and meat quality of intact and castrated gilts slaughtered at 106 or 122 kg BW

A total of 200 (Landrace × Large White dam × Pietrain × Large White sire) gilts of 50 ± 3 days of age (23.3 ± 1.47 kg BW) were used to investigate the effects of castration (intact gilt, IG v. castrated gilt, CG) and slaughter weight (SW; 106 v. 122 kg BW) on productive performance, carcass and meat quality. Four treatments were arranged factorially and five replicates of 10 pigs each per treatment. Half of the gilts were ovariectomized at 58 days of age (8 days after the beginning of the trial at 29.8 ± 1.64 kg BW), whereas the other half remained intact. The pigs were slaughtered at 106 or 122 kg BW. Meat samples were taken at Musculus longissimus thoracis at the level of the last rib and subcutaneous fat samples were taken at the tail insertion. For the entire experimental period, CG had higher (P < 0.05) BW gain and higher (P < 0.001) backfat and Musculus gluteus medius fat thickness than IG. However, IG had higher (P < 0.05) loin and trimmed primal cut yields than CG. Meat quality was similar for IG and CG but the proportion of linoleic acid in subcutaneous fat was higher (P < 0.001) for IG. Pigs slaughtered at 122 kg BW had higher (P < 0.001) feed intake and poorer feed efficiency than pigs slaughtered at 106 kg BW. An increase in SW improved (P < 0.001) carcass yield but decreased (P < 0.05) trimmed primal cut yield. Meat from pigs slaughtered at the heavier BW was redder (a*; P < 0.001) and had more (P < 0.01) intramuscular fat and less thawing (P < 0.05) and cooking (P < 0.10) loss than meat from pigs slaughtered at the lighter BW. In addition, pigs slaughtered at 122 kg BW had less (P < 0.01) linoleic acid content in subcutaneous fat than pigs slaughtered at 106 kg BW. Castration of gilts and slaughtering at heavier BW are useful practices for the production of heavy pigs destined to the dry-cured industry in which a certain amount of fat in the carcass is required. In contrast, when the carcasses are destined to fresh meat production, IG slaughtered at 106 kg BW is a more efficient alternative.     

Effects of social environment on welfare status and sexual behaviour of female pigs. II. Effects of space allowance

This study examined the effects of housing groups of adult female pigs (6 pigs per group) with a space allowance of 1, 2 or 3 m² per pig on sexual behaviour and welface status, determined by plasma free-corticosteroid concentrations. A lower percentage of gilts was detected in oestrus and a lower percentage of gilts was mated when housed with a space allowance of 1 m² per gilt than with a space allowance of either 2 or 3 m² per gilt (oestrus detection rate of 79, 88 and 100%, respectively, and a mating rate of 77, 85 and 97%, respectively). There was a significant increase in plasma free-corticosteroid concentrations when gilts were housed with a space allowance of 1 m² per gilt. The elevated free corticosteroid levels of gilts in the 1 m² per gilt treatment suggests that a chronic stress response due to crowding may have been responsible for the apparent impairment in the sexual behaviour of these animals.     

Litter size and piglet traits of gilts with different prolactin receptor genotypes

Seventy-seven Large White x Meishan F2 crossbred gilts with prolactin receptor (PRLR) genotype AA (n = 26), AB (n = 36) and BB (n = 15) were compared for teat number (FTm), age at first estrus, gestation length (GL), litter size, and litter means of functional teat number (FTp), birthweight (BW), and pre-weaning growth rate (GR). Own placental information was available for 88% of 620 live-born piglets (62 gilts), since placentae were labeled during farrowing. The effect of PRLR genotype of the mother on average placenta weight (PLW) and placenta efficiency (EFF = BW/PLW), was therefore, also analyzed, PRLR genotype significantly (P < 0.05) affected age at first estrus and, as a result (since the gilts were inseminated at a fixed estrus number), age and bodyweight at insemination. Furthermore, PRLR genotype affected total number of piglets born (TNB, P = 0.056) and number of piglets born alive (NBA, P = 0.072), but it did not affect (P > 0.3) GL, BW or GR, neither before nor after correction for litter size. BB gilts were significantly younger at first estrus and younger and lighter at insemination than AA gilts (P < 0.05). AA gilts had larger TNB (P = 0.047) and tended to have a larger NBA (P = 0.062) than BB gilts. TNB was 11.4 +/- 0.7, 10.8 +/- 0.6, and 8.8 +/- 0.9; NBA was 11.1 +/- 0.6, 10.5 +/- 0.6, and 8.7 +/- 0.9; BW was 1309 +/- 40, 1277 +/- 34, and 1290 +/- 53 g; and GL was 113.6 +/- 0.3, 113.8 +/- 0.3, and 113.5 +/- 0.4 days for AA, AB and BB gilts, respectively. The effects on litter size and age at first estrus are independent effects. PRLR affected PLW (P = 0.050) and EFF (P = 0.066), resulting in a difference between AA and BB gilts. PLW was 160 +/- 9, 181 +/- 7 and 196 +/- 11 g and EFF was 7.6 +/- 0.2, 7.3 +/- 0.2 and 6.7 +/- 0.3 for AA (n = 19), AB (n = 29) and BB (n = 14) gilts, respectively. After correction for TNB, the differences disappeared. Functional teat number of the AA. AB and BB gilts was 15.35 +/- 0.22, 15.53 +/- 0.18, and 15.60 +/- 0.29, respectively, and was not affected by PRLR genotype (P = 0.7). Functional teat number of piglets from AA, AB and BB mothers was 14.20 +/- 0.10, 14.37 +/- 0.08, and 14.63 +/- 0.13, respectively. Piglets from BB mothers had on average larger numbers of functional teats compared to piglets from AA mothers (P = 0.028). In conclusion, PRLR gene is a major gene or marker for age at first estrus, litter size, and litter average of number of functional teats in the Large White x Meishan F2 crossbred gilts studied. The favorable allele for litter size (A allele) is the unfavorable allele for age at first estrus and for litter mean of functional teat number.     

Effects of nutrient intake and number of oestrous cycles on in vitro development of preimplantation pig embryos

The effects of nutrient intake and insemination of gilts at first versus third oestrus on the in vitro development of preimplantation pig embryos were investigated. Standard swine management involves ad libitum feeding of gilts at first oestrus and restricted feeding of gilts at third oestrus. According to previous research, gilts inseminated at first oestrus demonstrate greater embryonic mortality than gilts inseminated at third oestrus, and it is possible that differences in nutrient intake between gilts inseminated at first versus third oestrus affect the viability of eggs or embryos. In the present study, experimental gilts were assigned to three treatments: animals designated 1A were inseminated at first oestrus and fed ad libitum; animals designated 3R were inseminated at third oestrus and were fed a restricted diet; and 3A animals were inseminated at third oestrus and fed ad libitum. Embryos collected from each treatment group were cultured in vitro, and data were evaluated according to cell stage at collection. Comparison of treatments 1A and 3R supported the contention of increased embryo mortality in gilts inseminated at first oestrus under normal management conditions. When cultures were initiated at the one- to two-cell or two- to four-cell stages, the percentage of 1A embryos developing to the morula stage (50.9%, 68.0%) was significantly lower than that of 3R embryos (88.9%, 90.9%; P < 0.05). Comparison of treatments 1A and 3A addressed effects due to the number of oestrous cycles. Significantly more two- to four-cell embryos from gilts inseminated at third oestrus and fed ad libitum reached the morula and expanded blastocyst stages of development (87.0%, 41.3%) compared with embryos from gilts inseminated at first oestrus and fed ad libitum (68.0%, 20.3%; P < 0.05). Finally, the effects of ad libitum feeding were determined by comparing treatments 3A and 3R. These data were inconclusive, as both positive and negative effects were observed. More one- to two-cell embryos from treatment 3R developed to the morula stage (88.9%) compared with 3A embryos collected at the same stage (64.7%), whereas a greater number of 3A embryos in the two- to four-cell category reached the expanded blastocyst stage (41.3%) than 3R embryos (21.2%; P < 0.05). These results support the hypothesis of lower in vitro developmental capacity for embryos collected from gilts inseminated at first oestrus. Furthermore, the findings indicate that differences in embryo viability between gilts inseminated at first versus third oestrus are related to the number of oestrous cycles and possibly to differential nutrition.     

Development of bone mineralization and body composition of replacement gilts fed a calcium and phosphorus depletion and repletion strategy

This study investigated the ability of replacement gilts to adapt their calcium and phosphorus utilization and their kinetics in bone mineralization to compensate for modified intake of these nutrients by applying a novel Ca and P depletion and repletion strategy. A total of 24 gilts were fed according to a two-phase feeding program. In the first phase, gilts (60–95 kg BW) were fed ad libitum a depletion diet providing either 60% (D60; 1.2 g digestible P/kg) or 100% (D100; 2.1 g digestible P/kg) of the estimated P requirement. In the second phase, gilts (95–140 kg BW) were fed restrictively (aim: 700–750 g/d BW gain) a repletion diet. Half of the gilts from each depletion diet were randomly assigned to either a control diet or a high-P diet (R100 and R160; with 2.1 and 3.5 g digestible P/kg, respectively) according to a 2 × 2 factorial design, resulting in four treatments: D60-R100, D60-R160, D100-R100 and D100-R160. Dual-energy X-ray absorptiometry was used to measure whole-body bone mineral content (BMC), bone mineral density (BMD) and lean and fat tissue mass on each gilt at 2-week intervals. The depletion and repletion diets, fed for 5 and 8 weeks, respectively, did not influence growth performance. The D60 gilts had a reduced BMC and BMD from the second week onwards and ended (95 kg BW) with 9% lower values than D100 gilts (P < 0.001). During repletion, D60 gilts completely recovered the deficit in bone mineralization from the second and fourth week onwards, when fed R160 (D60-R160 vs D100-R160) or R100 (D60-R100 vs D100-R100) diets, respectively (treatment × time interaction, P < 0.001); thus, the depletion diets did not affect these values at 140 kg BW. These results illustrate the rapid homeostatic counter-regulation capacity of dietary Ca and P, and they show the high potential to limit dietary digestible P concentration by completely excluding the use of mineral phosphates during the depletion phase, representative of the fattening period, without causing any detrimental effects to gilts at mating. The gilts were able to recover their BMC deficit between their selection at 95 kg BW and first mating at 140 kg BW by increasing their dietary Ca and P efficiency. Finally, excess dietary digestible P, requiring increased amounts of mineral phosphates, further increased the gilts’ BMC.     

Gilt development and mating in commercial swine herds with varying reproductive performance

The primary objectives were to improve standard operating procedures for gilt development and mating, based on a comparison of practices among commercial Japanese herds with varying reproductive performance. Questionnaires were sent to 115 herds; the 96 herds (83.5%) responding were classified, on the basis of the upper and lower 25th percentiles of pigs weaned per mated female per year, into high-, intermediate- or low-performing herds. During gilt development, high-performing herds switched to a gilt developer diet at an earlier age than low-performing herds (P < 0.05). More high-performing herds performed first insemination “immediately,” with second insemination “6 to 12 h” after first estrus detection than low-performing herds (P < 0.05). However, there were no differences (P > 0.05) among productivity groups with regard to the use of nutritional flushing or percentage of AI used. In multilevel analyses (17,582 service records), gilts in herds using direct boar contact were 13.73 d younger at first mating than those in the herds using indirect boar contact (P < 0.05), but age was not related to feeding practices or the number of days of boar contact per week (P > 0.05). First-serviced gilts in the herds that performed first insemination “immediately” after first estrus detection had an 8.3 to 8.4% higher farrowing rate (FR) than those in herds that performed first insemination at “6 to 12 h” and “24 h” (P < 0.01). Reserviced gilts in the herds with first insemination “immediately” after first estrus detection had 7.5% higher FR than those in herds with first insemination at “6 to 12 h” (P < 0.05). Meanwhile, first-serviced and reserviced gilts in herds that restricted feed after insemination had 0.23 and 0.17 more pigs born alive (PBA) than gilts in the herds that did not restrict feed (P < 0.05). However, PBA was not related to time of insemination (P > 0.05). In conclusion, to improve gilt reproductive performance, we recommend stimulating gilt estrus by using direct boar contact, performing first insemination “immediately” after first estrus detection, and restricting feed intake after insemination.