Lower Litter Size Research Articles

An assessment of reproductive and lifetime performances of Kagoshima Berkshire gilts and sows

We investigated the reproductive and lifetime performances of Kagoshima Berkshire gilts and sows. We examined 20 605 parity records of 4419 pigs for 2008 to 2012 on a farrow-to-finish commercial farm. The mean parity (± SD) of all animals was 3.0 ± 2.1. For farrowing performance, the highest numbers of total pigs born and pigs born alive were found in sows with parities 5 and 6 and with parity 3-6, respectively (P < 0.05). Regarding weaning and mating performance, sows with parity 2 had the lowest preweaning mortality (P < 0.05). The longest weaning-to-first-mating interval was found in parity 1 pigs, and the interval decreased as parity increased (P < 0.05). Parities 0 and 1 pigs had the lowest farrowing rate and those with parity 4 had the highest farrowing rate (P < 0.05). The mean parity at culling, total number of pigs born alive in a lifetime, and nonproductive days in a lifetime were 5.5 ± 2.93, 49.2 ± 24.72 pigs, and 132.1 ± 83.34 days, respectively. These animals had a lower litter size and fertility that the F1 crossbred sows mainly used in Japan, but a similar tendency for performance by parity.

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 &gt;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&lt;0,05). As fêmeas OP1 e OP2 tiveram maior chance (P&lt;0,05) de não parir na classe &gt;1% de perda de peso. A maior perda de peso não foi um fator de risco para não parir na condição OP3-5 (P&gt;0,05). Não houve interação de OP versus perda de peso (P&gt;0,05) para IDE e total de leitões nascidos. Fêmeas OP1 apresentaram IDE mais longo e menor tamanho da leitegada no parto subsequente (P&lt;0,05) do que fêmeas OP2 e OP3-5. As perdas corporais na lactação não influenciaram o IDE (P&gt;0,05), mas reduziram o tamanho da leitegada subsequente (P&lt;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.

Maternal Separation Affects Mothers’ Affective and Reproductive Behaviors as Well as Second Offspring’s Emotionality

Daily separation of rat pups from their mothers while the preweaning period has an impact on behavior and stress response of pups. We hypothesized that maternal separation may create a depression-like state in mother rats from which we separate the rat pups and decrease their reproductive function and fertility. Also, we aimed to evaluate the transmission degree of depression and anxiety across generations. Females aged 3 months were divided in two groups of 10 rats each. After a first mating and a first parturition, we conducted maternal separation 3 h during 22 days for the experienced group while the control group mothers kept their pups. At 4 months of age, females underwent behavioral tests and a second mating. Second generation’s pups were also subjected to behavioral tests. Behavioral tests showed that mothers which experienced separation were more depressive and anxious than control ones, also they had a lower litter size. Rats pups of the second generation whose mothers experienced maternal separation also revealed behavior changes akin to depression and anxiety. Thus, maternal separation causes depressive and anxious-likestates on mother rats which experienced separation and has an impact on their litter size. Also, consequences of maternal separation seem to last throughout generations.

Influence of rabbit sire genetic origin, season of birth and parity order on doe and litter performance in an organic production system.

The aim of this study was to compare both the performance of litters derived from two sire genetic origins (SGO), Vienna Blue (VB) and Burgundy Fawn (BF), along successive seasons of birth (SB; winter, spring, summer and autumn), and doe reproductive performance in an organic production system. A total of fifty-eight does consisting of a mixture of crosses of several medium-large size breeds at different parity order (P, 1 = nulliparous; 2 = primiparous; ≥3 = multiparous) and twelve males (6 VB and 6 BF) were housed indoors at environmental conditions that followed seasonality. An extensive reproductive rhythm was used and kits were weaned at 46±6 d of age. Doe reproductive performance and the data of 105 litters (55 from VB and 50 from BF SGO) were recorded throughout the SB. No statistically significant differences related to SGO effect were observed. As regards parity order, multiparous does showed higher live weights (LW) (p<0.05), total born (p<0.01), total born alive (p<0.05) per delivery, and litter weight of born alive (p<0.05), but lower milk output at 21st d than primiparous does (p<0.05). The extensive reproductive rhythm mainly increased litter performance at birth in multiparous does but was not sufficient to permit a complete recovery of body reserves lost during lactation. Autumn SB negatively affected doe LW variation between deliveries. The number of pups born and born alive per delivery (p<0.05) and litter size at 21 d of age and at weaning (p<0.01) were lower during hot SB. Due to the lower litter size of pups born in summer and autumn, their individual weight at 21st d of age and daily individual growth rate 0 to 21 d were higher than those of pups born in winter (p<0.001). Litter performance at 21st d of age and individual pup pre-weaning growth rate were poorer for those born in spring than in other seasons due to the harmful effects of increased environmental temperatures. SB affected most of the performance traits of does and young rabbits reared under the organic farming system. The rabbits seemed better suited to organic rearing conditions during winter than in other seasons. The worst results overall were obtained in the spring SB, whereas the hot SB negatively affected both doe energy balance and prolificacy. In conclusion, the pups of the 2 SGO showed good pre-weaning performance and seemed suited to the organic rabbit production system.

Polymorphism in BPM-15 gene and its association with litter size in Anglo-Nubian goat

For association between BMP-15 (exon2) gene polymorphisms and litter size trait in Anglo-Nubian goat, PCR-SSCP technique was developed. Twenty-five female Anglo-Nubian goats reared under Egyptian conditions were selected according to their litter size. DNA from blood samples of these animals was extracted to amplify 140-bp of the BMP-15 gene affecting litter size production trait in goats. Based on the breeding value, 25 animals were selected from the highest to the lowest litter size productivity. PCR amplification size of the BMP-15 gene (140-bp) was genotyped in all animals. PCR-SSCP analysis of the BMP-15 gene (140-bp) showed three various genotypes BB, BM and MM with frequencies 0.46, 0.43 and 0.11, respectively. The frequencies of the B and M alleles were 0.68 and 0.32, respectively. The results indicated that the BB genotype was higher in litter size productivity than the other genotypes with significant differences. The result of this study confirmed that BMP-15 gene may be a strong candidate gene for further applications in marker-assisted selection (MAS) for litter size in goats.

Maternal Exposure to High Temperatures Disrupts OCT4 mRNA Expression of Rabbit Pre‐Implantation Embryos and Endometrial Tissue

We examined the effect of prolonged high heat stress on reproductive performance and its relationship with gene expression in pre-implantation embryos and endometrial tissue. In experiment 1, primiparous rabbit does were divided into two environments: control does (maintained between 14 and 22°C) and heat-treated does housed in a climatic chamber (maintained between 25 and 35°C). Females were reproducing, and the litter size and live born kits were assessed at 2nd and 3rd partum. In heat-treated does, lower litter size (9.7±0.48 and 11.4±0.50) and fewer live born kits (7.2±0.55 and 10.2±0.57) were observed, although similar ovulation rates and numbers of pre-implantation embryos were noted. In experiment 2, after 3rd partum multiparous non-lactating does from each experimental group were used to obtain pre-implantation embryos and endometrial tissue. mRNA transcripts from OCT-4, VEGF, erbB3, Ifn-ɣ, HSP70 and HSP90 were analysed by real-time qPCR. Higher values of OCT-4 expression were observed in embryos and endometrial tissue in females reproduced under heat conditions. Moreover, elevated temperatures have been shown to up-regulate VEGF in embryos and down-regulate Ifn-ɣ in endometrial tissue. The findings suggest a deleterious temperature effect on litter size and live born kits as a consequence of variation in gene expression pattern of the pre-implantational embryo and the endometrium associated with proliferation and differentiation and probably with implantation and uterine and foetal development during gestation.

Productivity of Sardi, D’man and their crossbred ewes mated to terminal sires

Reproductive performance of 165 contemporary non-prolific Sardi (S), prolific D’man (D) and ¼-D, ½-D and ¾-D crossbred ewes mated to Ile-de-France (IF) and Mérinos Précoce (MP) rams, and growth and survival of their 209 lambs were analysed in order to assess the performance in a terminal crossbreeding system. Breed group of ewe had a significant effect on the litter size and ovulation rate, but not on embryo survival. The lowest litter size and ovulation rate were recorded for Sardi ewes, the highest for D’man and ¾-D ewes, and the other breed groups were intermediate, with an increase tendency as the proportion of D’man genes increased in the ewe genotype. Moreover, litter weight at birth and litter size at 60 days were affected by breed group of ewe, but conception rate and litter weight at 60 days were not influenced. Litter weight at birth of purebred and crossbred D’man ewes was the heaviest and that of Sardi breed was the lowest. Litter size at 60 days was the lowest for Sardi ewes, the highest for purebred D’man ewes and intermediate for crossbred D’man ewes. Sardi ewes weaned 0.49, 0.53, 0.88 and 1.05 lambs less than ¼-D, ½-D, ¾-D and purebred D’man ewes, respectively. Except conception rate on which service ram breed had a significant effect, the other reproductive traits were unaffected. Conception rate of ewes sired to MP rams was 19% lower than that of ewes mated to IF rams.Breed group of dam influenced significantly lamb weight at birth, at 30 days and at 60 days, but not lamb survival prior to weaning. Lambs born to Sardi and ¼-D crossbred dams had the highest weights, those from D’man and ¾-D dams had the lowest weight, and those from ½-D ewes were intermediate. Extreme differences between weights of lambs from different breed groups of dams were 0.78kg at birth, 1.72kg at 30 days, and 2.00kg at 60 days. Breed of sire had a significant effect on lamb weight at 30 days only. Lambs sired by IF rams were 0.62kg heavier at 30 days than those sired by MP rams. It was concluded that in a terminal sire production, using ¼-D, ½-D and ¾-D crossbred ewes would be better than the use of non-prolific purebred ewes, since this system takes advantage of increased reproductive capacity in the ewe with sensible increase in lamb performance.

Progestagen Supplementation During Early Pregnancy does not Improve Embryo Survival in Pigs

Progesterone supplementation during early pregnancy may increase embryo survival in pigs. The current study evaluated whether oral supplementation with an analogue of progesterone, altrenogest (ALT), affects embryo survival. A first experiment evaluated the effect of a daily 20-mg dosage of ALT during days 1-4 or 2-4 after onset of oestrus on embryo survival at day 42 of pregnancy. A control group (CTR1) was not treated. The time of ovulation was estimated by transrectal ultrasound at 12-h intervals. Altrenogest treatment significantly reduced pregnancy rate when start of treatment was before or at ovulation: 25% (5/20) compared to later start of treatment [85% (28/33)] and non-treated CTR1 [100% (23/23)]. Altrenogest treatment also reduced (p < 0.05) number of foetuses, from 14.6 ± 2.6 in CTR1 to 12.5 ± 2.5 when ALT started 1-1.5 days from ovulation and 10.7 ± 2.9 when ALT started 0-0.5 days from ovulation. In a second experiment, sows with a weaning-to-oestrous interval (WOI) of 6, 7 or 8-14 days were given ALT [either 20 mg (ALT20; n = 49) or 10 mg (ALT10; n = 48)] at day 4 and day 6 after onset of oestrus or were not treated (CTR2; n = 49), and farrowing rate and litter size were evaluated. Weaning-to-oestrous interval did not affect farrowing rate or litter size. ALT did not affect farrowing rate (86% vs 90% in CTR2), but ALT20 tended to have a lower litter size compared with CTR2 (11.7 ± 4.1 vs 13.3 ± 3.1; p = 0.07) and ALT10 was intermediate (12.3 ± 2.9). In conclusion, altrenogest supplementation too soon after ovulation reduces fertilization rate and embryo survival rate and altrenogest supplementation at 4-6 days of pregnancy reduces litter size. As a consequence, altrenogest supplementation during early pregnancy may reduce both farrowing rate and litter size and cannot be applied at this stage in practice as a remedy against low litter size.

Reproductive performance of second parity sows: Relations with subsequent reproduction

The objective of this study was to determine relations between reproductive performance, i.e. being a repeat breeder and litter size, in 2nd parity and reproductive performance in later parities. In addition, relations between the 1st and 2nd parity litter size and litter size in later parities were determined. First, 184,135 records from 46,571 sows were used to analyze the effect of being a repeat breeder in 2nd parity on subsequent farrowing rate, litter size and parity number at culling. Second, 161,521 records of 39,654 sows were used to analyze the effect of litter size from 1st insemination in 2nd parity, being either low (≤10 piglets total born), medium (11–13) or high (≥14), on subsequent litter size, farrowing rate and parity number at culling, with litter size in 1st parity included in the model as well. In total 15.7% of the sows inseminated in 2nd parity were a repeat breeder in 2nd parity. Being a repeat breeder in 2nd parity did not affect litter size in subsequent parities, however it decreased farrowing rate in parity 3 (4.1%) and 4 (3.4%), but not in later parities (P<0.05). Repeat breeders in 2nd parity were culled on average 2 parities earlier compared with non-repeat breeders (resp. parity 5 vs. 7, P<0.05). Sows with a low litter size in 2nd parity showed a lower litter size in parity 3 and up compared with sows with a medium or high litter size in 2nd parity (P<0.05). The magnitude of this effect, however, decreased if litter size in 1st parity increased. For example, the difference in piglets born in parity 3–5 between sows with a low and high litter size in 2nd parity was −4.6 piglets for sows with a low litter size in 1st parity. This difference decreased to −3.3 piglets for sows with a high litter size in 1st parity. Sows with a high litter size in 2nd parity had 2% lower farrowing rate in parity 3, but not in later parities. Sows with a low litter size in 2nd parity were culled 1 parity earlier compared with sows with a medium or high litter size in 2nd parity. This study showed that a large part of the sows with poor reproductive performance in 2nd parity can be expected to have a poor reproductive performance in subsequent parities. The effect of 2nd parity litter size on subsequent litter size, however, depends on 1st parity litter size.

Effectiveness of Vitamin C Consumption In Pregnancy On Dexamethasone Induced Low Birth Weight.

Synthet ic glucocor t icoids, including Dexamethasone have been shown to induce Intra Uterine Growth Retardat ion (IUGR) when administered in the last trimester of pregnancy. This study was designed to investigate the effect of Vitamin C on Dexamethasone induced low birth weight anexperimental model using theAlbino rats. Pregnant Sprague Dawley rats were divided into four groups of six rats each; group A- vehicle only,group B- Vitamin C treated (100mg/kg maternal body weight), group C-Dexamethasone treated (bolus dose of 100 micro grams of Dexamethasone/kg maternal body weight on day 13 followed by a daily dose of 200 micro grams/kg maternal body weight from day 14 tilldelivery) and group D -Dexamethasone and Vitamin C treated (100mg/kg maternal body weight of Vitamin C from day 7 of pregnancy to term; and on day 13 of pregnancy, were injected with a bolus dose of 100micro grams/kg maternal body weight of Dexamethasone and subsequently a daily dose of 200 micro grams/kg maternal body weight until term). The weight and size of the litters along with the gestationperiod and weight gain during the period of study were recorded.T h e r e s u l t s s h owe d t h a t t h o u g h Dexamethasone caused low birth weight, Vitamin C had no significant (p>0.05) effect on dexamethasone induced low birth weight, litter size or gestation period.It was hereby concluded that this was probably due to the inability of Vitamin C to influence the mechanisms by which dexamethasone induces low birth weight.

Induction of APS after TTd Hyper-Immunization has a Different Outcome in BALB/c and C57BL/6 Mice

The antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by vascular thrombosis and/or pregnancy complications (lower fecundity and lower litter size), as well as by an increase in anti-β(2) glycoprotein I (β(2) GPI)-specific autoantibody titer. We have investigated how the genetic background of the immune system [T helper (Th) prevalence] and the type of animal model of APS influence the induced pathology. Antiphospholipid syndrome induced by tetanus toxoid (TTd) hyper-immunization and by intravenous application of monoclonal anti-β(2) GPI-specific antibody 26 was compared in C57BL/6 (Th1 prone) and BALB/c (Th2 prone) mice. Tetanus toxoid hyper-immunization of BALB/c mice led to reduction in fertility, but in C57BL/6 mice a decrease in fecundity occurred. In both cases, pathology was caused by anti-β(2) GPI antibodies, the production of which was adjuvant and strain dependent. We conclude that TTd immunization and i.v. application of monoclonal antibody 26 induced the same reproductive pathology and that the type of pathology is strain dependent.

EFFECT OF DIFFERENT FEED RESTRICTIONS DURING REARING ON PRODUCTION PERFORMANCE IN RABBIT DOES

Ad libitum fed ten-week-old littermate female NZW rabbits were divided into four equal groups (n=4 x 50) based on their body weight. They were raised during the next 7 to 12 weeks as follows: a control group with ad libitum feeding (C); access to a restricted 130 g daily feed portion per head until 17 weeks of age and 140 g/day until first insemination (130R); one day (24 hours) fasting every week (10); 9 hours' daily access to the diet (9H). When the young does reached 75 to 80% of adult weight (3.4 to 3.5 kg, between 17 and 22 wk of age), the feed supply returned to ad libitum tour days before the first Al, resulting in a 4-day flushing in the 3 treated groups. The does were reinseminated 9-11 days post partum and three consecutive deliveries were investigated. Fertility was significantly higher in nulliparous 1D group (92%) than in the control (70%). Litter size at birth, at 21 and at 35 days of age in groups 130R (8.8, 7.6, 7.3) and 9H (8.9, 8.3, 8.2) while at the same age litter weights of 130R (502 g, 2760 g, 6295 g) and 9H does (543 g, 2848 g, 6761 g) were insignificantly higher than for C ones (8.7, 7.3, 7.0 and 472 g, 2451 g and 6032 g, resp.). The lowest litter size and litter weight of 1 D females could be explained by their smallest body weight throughout the trial. Among the tour groups, the 130R females lost less weight at kindling and they were the heaviest during the lactation period. In general, it was concluded that raising young rabbits with restricted 130 g diet per day or with access of 9 hours' daily feeding time resultad in doe performances that neither decreased nor improved significantly.

Effects of Dextrose Plus Lactose in the Sows Diet on Subsequent Reproductive Performance and within Litter Birth Weight Variation

Effects of dextrose plus lactose in sow's feed were tested on subsequent reproductive performance and within litter birth weight variation. During the last week of gestation and lactation, sows were either fed a commercial lactation diet (Control: C), or an isocaloric diet containing 25 g/kg dextrose plus 25 g/kg lactose ( T). In the subsequent weaning-to-oestrus interval (WEI), all sows received the same amount of a commercial feed, but T sows were supplemented with 150 g dextrose plus 150 g lactose per day. Weight and backfat changes were recorded as well as litter characteristics during the treatment period and the subsequent parity. No significant effect of treatment was found on the subsequent reproductive performance, including the number of piglets born, although the number of live born piglets was 0.51 larger (p=0.31) and weight of the live born piglets was 84 g higher in the T sows (p=0.07) than in the C sows. When sows were categorized in sows with 12 or less and more than 12 total born piglets in the previous litter, treatment of sows with dextrose plus lactose resulted for the group with 12 or less piglets in a strong increase in subsequent total born piglets (13.97), whereas in the untreated sows the subsequent litter size was 11.89. In the group with more than 12 total born piglets, no effect of treatment was found (interaction between previous litter size and treatment p=0.03). The within litter variation in birth weight in the subsequent litter was numerically lower in the T sows. We concluded that the use of dextrose and lactose during lactation and WEI seems to enhance litter size in sows with low previous litter size and seems to have the potential to reduce the within litter variation in birth weight.

Some Notes on Biological Aspects of Captive Javan Warty Pig (Sus verrucosus)

The Javan warty pig (Sus verrucosus) is an endemic pig to Java and Bawean Islands, while population on Madura Island is thought to be extinct. The problem in establishing ex-situ captive breeding is the lack of information on biology or physiology. A study on these aspects was conducted in 16 Javan warty pigs and 2 cadavers in Surabaya Zoo, Surabaya. Birth profile was evaluated and blood collections were conducted, as well as analysis on spermatozoa morphology. Data showed that blood parameters were not different among the age groups (juvenile and adult) or sex and within the range of Sus scrofa. Extreme values were only obtained from the palette with the female reaching 14.5 x 103/mm3, while adult male and juvenile pigs were 58-75 x 103/mm3. Diameter of both testicles with skin intake was 56.42 mm, with the length of left testicle being 83.29 mm and right testicle 78.88 mm. Javan warty pig spermatozoa had longer size for the head and tail lengths compared to average pigs sperms. Litter size was between two to four, with the average of 2.75 litters (SD 0.98). Low litter size in this species is something that has to be concerned from the conservation point of view, therefore a captive breeding population program needs to be considered.Key words: Javan warty pig, Sus verrucosus, blood parameters, sperm

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.

Variation in chromosome number in the blue fox (Alopex lagopus) and its effect on fertility

Effects on fertility exerted by polymorphism for a centric fusion between chromosome Nos. 23 and 24 were investigated in the blue fox (Alopex lagopus). The pregnancy rate was not affected by the chromosome type, but the litter size was lower for the centric fusion heterozygotes compared to the homozygous animals. The pregnancy rate was affected by the time of mating, and the litter size was also affected by parity. The survival rate was higher among the centric fusion heterozygotes compared to the homozygous animals. It is concluded that the centric fusion polymorphic system is balanced, the higher survival rate among heterozygotes counteracting the lower litter size of these animals.

Variation in Reproductive Patterns of Antelope Ground Squirrels, Ammospermophilus leucurus, from Oregon to Baja California

Abstract Clines of biological variation result from variation in physical environmental conditions. We report new reproductive data for a population of antelope ground squirrels, Ammospermophilus leucurus, at the northern geographic limit of this species. We then analyze reproductive patterns at 3 sites spanning the entire north–south extent of the geographic range, covering more than 2,500 km and 21 degrees of latitude. The overall breeding season of populations is relatively short in Oregon (42°N) and California (37°N), but in Baja California (24°N) it encompasses half a year. Mean litter size decreases significantly from north to south, from 9.3 (SD = 1.8) per litter in Oregon to 5.9 (SD = 1.5) in Baja California. Major shifts in seasonality of precipitation and ecosystem composition and diversity are associated with longer breeding season and lower litter size at the southern geographic extreme of A. leucurus. The environmental predictability for the northern populations is due to “constancy,” whereas...

Genetic rescue and inbreeding depression in Mexican wolves

Although inbreeding can reduce individual fitness and contribute to population extinction, gene flow between inbred but unrelated populations may overcome these effects. Among extant Mexican wolves (Canis lupus baileyi), inbreeding had reduced genetic diversity and potentially lowered fitness, and as a result, three unrelated captive wolf lineages were merged beginning in 1995. We examined the effect of inbreeding and the merging of the founding lineages on three fitness traits in the captive population and on litter size in the reintroduced population. We found little evidence of inbreeding depression among captive wolves of the founding lineages, but large fitness increases, genetic rescue, for all traits examined among F1 offspring of the founding lineages. In addition, we observed strong inbreeding depression among wolves descended from F1 wolves. These results suggest a high load of deleterious alleles in the McBride lineage, the largest of the founding lineages. In the wild, reintroduced population, there were large fitness differences between McBride wolves and wolves with ancestry from two or more lineages, again indicating a genetic rescue. The low litter and pack sizes observed in the wild population are consistent with this genetic load, but it appears that there is still potential to establish vigorous wild populations.

Embryonic Loss in Sows with Repeated Propensity for Small Litter Size

Information is lacking as to the timing and cause of sows that repeatedly have low litter size over several parities. Sows evaluated for the present study had at least two parities either small <or=7 (SL) or normal >or=12 (NL) litter size. Following breeding of sows with contemporary boars, reproductive tracts were obtained on day 30 of gestation. There was no difference (p > 0.10) between SL and NL sows in the number of CL, embryo weight or placental length. The total number of embryos and embryonic survival tended to be lower (p < 0.10) in SL sows compared with NL sows, but there were 5.1 less viable embryos (p < 0.03) in SL. Results indicate that time of conceptus loss in SL sows was variable throughout gestation.

Ultrasonographic assessment of embryonic, fetal and placental development in Ossimi sheep

The aim of the present study was to determine the pattern of fetal growth in breeds characterized by low litter size and birth weight. Also, accuracy of the fetal kidney length (KIL) in predicting the gestational age (GA) in sheep was investigated. In experiment 1, serial ultrasonographic examinations were performed in 12 Ossimi ewes for a total of 336 times between days 22 and 146 of gestation. Sequential changes of the fetal crown-rump length (CRL), diameter of the amniotic vesicle (AVD), chest depth (CHD), abdominal diameter (ABD), eyeball diameter (EBD), ruminal length (RUL), placentome diameter (PLD), and kidney length (KIL) were recorded. Changes in echogenicity of the placentome and fetal fluids, and beginning of ossification were registered. Regression models for estimation of the gestational age were derived from the biometric indices. In experiment 2, the KIL was estimated in 30 Ossimi ewes and the GA was calculated with the mean squared predicted errors method. The value obtained was compared with the actual GA. The embryo and amniotic vesicle were first observed by days 25.38 ± 1.2 and 28.67 ± 1.0, respectively. Organization of the embryo into head, body and limb buds was detected by day 38 ± 3.2. Ossification was observed on the head, ribs and vertebrae by days 44.86 ± 2.5, 50.25 ± 3.4 and 51.50 ± 2.5, respectively. The amniotic fluid remained clear and echo-free until day 80.67 ± 11.2, then it became slightly turbid. Definite turbidity was observed by day 103.0 ± 8.0. Echogenic spots appeared in the allantoic fluid by day 138.0 ± 9.5. The placentome increased in size until day 82.73 ± 7.7, then it began to collapse. The fetal kidney was first visualized by day 73.2 ± 6.3. Its mean long axis increased linearly from 1.41 ± 0.2 cm on day 76 to 3.61 ± 0.3 cm on day 146 ( Y = 0.0345 X − 1.2052, R 2 = 0.81). Except the PLD, regression and correlation coefficients of the various measurements on gestational age were high significant. Using the KIL—predicting equation, no significant difference was found between the expected and observed fetal ages. In conclusion, sonographic fetometry in Ossimi sheep can be valuable for the evaluation of fetal development, the estimation of gestational age and the prediction of parturition dates. The KIL was easy to make and could therefore be included into the model for dating pregnancies. The times of organization, ossification, turbidity of the fetal fluids and degeneration of placentome might be helpful in judging the fetal age.