Competing seed consumers drive the evolution of scatter-hoarding: Why rodents do not put all their seeds in one larder

Competition for food resources amongst animal seed dispersers and pilferers has driven dispersers to increasingly innovative seed-caching methods.We determined cache sizes in the field as well as seed cache recovery ability of a scatter-hoarding mouse, Acomys subspinosus, and compared these results to its seed competitor, the seed predator Rhabdomys pumilio.We found that up to 76% of A. subspinosus caches in the field contained one seed and that A. subspinosus was able to find caches of all sizes equally well under wet and dry soil conditions. In contrast, R. pumilio was able to find caches of all sizes in wet soil conditions but recovery success of small caches (single-seed) was poor in dry soil conditions. This suggests that scatter-hoarding may have evolved in A. subspinosus as an anti-pilfering strategy. This strategy would likely work best in dry conditions, where cache pilferers have difficulty locating small caches.     

Visual and auditory cues facilitate cache pilferage of Siberian chipmunks (Tamias sibiricus) under indoor conditions

In the struggle for survival, scatter‐hoarding rodents are known to cache food and pilfer the caches of others. The extent to which rodents utilize auditory/visual cues from conspecifics to improve cache‐pilfering is unknown. Here, Siberian chipmunks (Tamias sibiricus) were allowed to search for caches of Corylus heterophylla seeds (man‐made caches and animal‐made caches) after experiencing cues from a conspecific's cache‐searching events. For each type of cache, 3 experimental scenarios were presented: (1) alone (control); (2) auditory/visual (hearing and seeing conspecific's cache‐searching events); and (3) auditory only (hearing conspecific's cache‐searching events only) with random orders. The subjects located man‐made caches faster, harvested more caches, and hoarded more seeds both in the auditory/visual and the auditory only treatments compared to the control, while scatter‐hoarding more seeds in the auditory/visual treatment but larder‐hoarding more seeds in the auditory only treatment. Compared to the control, the animals spent less time locating animal‐made caches, harvested more caches, ate fewer seeds, larder‐hoarded more seeds and hoarded more seeds in total both in the auditory/visual and the auditory only treatments, while eating more seeds and hoarded fewer seeds in total in the auditory only treatment than in the auditory/visual treatment. The results also show that females spent less time locating the animal‐made caches, but they scatter‐hoarded fewer seeds than males in the auditory/visual treatment. To the best of our knowledge, this is the first report that visual and/or auditory cues of conspecifics improve cache‐pilfering and hoarding in rodents.     

Visual landmark‐directed scatter‐hoarding of Siberian chipmunks Tamias sibiricus

Spatial memory of cached food items plays an important role in cache recovery by scatter‐hoarding animals. However, whether scatter‐hoarding animals intentionally select cache sites with respect to visual landmarks in the environment and then rely on them to recover their cached seeds for later use has not been extensively explored. Furthermore, there is a lack of evidence on whether there are sex differences in visual landmark‐based food‐hoarding behaviors in small rodents even though male and female animals exhibit different spatial abilities. In the present study, we used a scatter‐hoarding animal, the Siberian chipmunk, Tamias sibiricus to explore these questions in semi‐natural enclosures. Our results showed that T. sibiricus preferred to establish caches in the shallow pits labeled with visual landmarks (branches of Pinus sylvestris, leaves of Athyrium brevifrons and PVC tubes). In addition, visual landmarks of P. sylvestris facilitated cache recovery by T. sibiricus. We also found significant sex differences in visual landmark‐based food‐hoarding strategies in Siberian chipmunks. Males, rather than females, chipmunks tended to establish their caches with respect to the visual landmarks. Our studies show that T. sibiricus rely on visual landmarks to establish and recover their caches, and that sex differences exist in visual landmark‐based food hoarding in Siberian chipmunks.     

Asymmetric competition for seeds between two sympatric food hoarding rodents: implications for coexistence

Asymmetric competition occurs when some species have distinct advantages over their competitors and is common in animals with overlapping habitats and diet. However, the mechanism allowing coexistence between asymmetric competitors is not fully clear. Chinese white-bellied rats (Niviventer confucianus, CWR) and Korean field mice (Apodemus peninsulae, KFM) are common asymmetric competitors in shrublands and forests west of Beijing city. They share similar diet (e.g. plant seeds) and activity (nocturnal), but differ in body size (CWR are bigger than KFM), food hoarding habit (CWR: mainly larder hoarding; KFM: both larder and scatter hoarding), and ability to protect cached food (CWR are more aggressive than KFM). Here, we tested seed competition in 15 CWR–KFM pairs over a 10-day period under semi-natural enclosure conditions to uncover the differences in food hoarding, cache pilferage, and food protection between the 2 rodents, and discuss the implication for coexistence. Prior to pilferage, CWR harvested and ate more seeds than KFM. CWR tended to larder hoard seeds, whereas KFM preferred to scatter hoard seeds. Following pilferage, CWR increased consumption, decreased intensity of hoarding, and pilfered more caches from KFM than they lost, while KFM increased consumption more than they hoarded, and they preferred to hoard seeds in low and medium competition areas. Accordingly, both of the 2 rodent species increased their total energy consumption and hoarding following pilferage. Both rodent species tended to harvest seeds from the source, rather than pilfer caches from each other to compensate for cache loss via pilferage. Compared to CWR, KFM consumed fewer seeds when considering seed number, but hoarded more seeds when considering the seeds’ relative energy (energy of hoarded seeds/rodent body mass^2/3) at the end of the trials. These results suggest that asymmetric competition for food exists between CWR and KFM, but differentiation in hoarding behavior could help the subordinate species (i.e. KFM) hoard more energy than the dominant species (i.e. CWR), and may contribute to their coexistence in the field.     

Does scatter‐hoarding of seeds benefit cache owners or pilferers?

The scatter‐hoarding behavior of granivorous rodents plays an important role in seed dispersal and seedling regeneration of trees, as well as the evolution of several well‐known mutualisms between trees and rodents in forest ecosystems. Because it is difficult to identify seed hoarders and pilferers under field conditions by traditional methods, the full costs incurred and benefits accrued by scatter‐hoarding have not been fully evaluated in most systems. By using infrared radiation camera tracking and seed tagging, we investigated the benefits and losses of scatter‐hoarded seeds (Camellia oleifera) for 3 sympatric rodent species (Apodemus draco, Niviventer confucianus and Leopoldamys edwardsi) in a subtropical forest of Southwest China during 2013 to 2015. We established the relationships between the rodents and the seeds at the individual level. For each rodent species, we calculated the cache recovery rate of cache owners, as well as conspecific and interspecific pilferage rates. We found that all 3 sympatric rodent species had a cache recovery advantage with rates that far exceeded average pilferage rates over a 30‐day tracking period. The smallest species (A. draco) showed the highest rate of scatter‐hoarding and the highest recovery advantage compared with the other 2 larger species (N. confucianus and L. edwardsi). Our results suggest that scatter‐hoarding benefits cache owners in food competition, supporting the pilferage avoidance hypothesis. Therefore, scatter‐hoarding behavior should be favored by natural selection, and plays a significant role in species coexistence of rodent community and in the formation of mutualism between seeds and rodents in forest ecosystems.     

Scatterhoarding rodents favor higher predation risks for cache sites: The potential for predators to influence the seed dispersal process

Scatterhoarding rodents often place caches in the open where pilferage rates are reduced, suggesting that they tradeoff higher risks of predation for more secure cache sites. We tested this hypothesis in two study systems by measuring predation risks inferred from measures of giving‐up densities (GUDs) at known cache sites and other sites for comparison. Rodent GUDs were measured with small trays containing 3 L of fine sand mixed with sunflower seeds. In the first experiment, we relied on a 2‐year seed dispersal study in a natural forest to identify caches of eastern gray squirrels (Sciurus carolinensis) and then measured GUDs at: (i) these caches; (ii) comparable points along logs and rocks where rodent activity was assumed highest; and (iii) a set of random points. We found that GUDs and, presumably, predation risks, were higher at both cache and random points than those with cover. At the second site, we measured GUDs of eastern gray squirrels in an open park system and found that GUDs were consistently lowest at the base of the tree compared to more open sites, where previous studies show caching by squirrels to be highest and pilferage rates by naïve competitors to be lowest. These results confirm that predation risks can influence scatterhoarding decisions but that they are also highly context dependent, and that the landscape of fear, now so well documented in the literature, could potentially shape the temporal and spatial patterns of seedling establishment and forest regeneration in systems where scatterhoarding is common.     

星鸦(Nucifraga caryocatactes)对集中放置红松球果的分散贮藏与临时贮点管理

星鸦(Nucifraga caryocatactes)对红松种子进行分散贮藏、重取、建立和更新临时贮点,这一过程的研究对丰富贮食行为理论很有意义。2017年10—11月,采用红外相机监测和样方调查的方法,分析凉水国家级自然保护区星鸦对集中堆放红松球果的贮食行为、临时贮点管理以及影响贮点生境选择的主要因素。结果表明:贮藏地星鸦的重取行为比例最高,为(55.42±1.34)%,移动行为占(25.74±6.24)%,贮藏行为占(11.08±2.69)%,且有争斗行为。星鸦贮点大小为(2.39±0.09)粒,密度为(1.82±0.11)个/m^2,贮藏深度为(1.55±0.03)cm。不同生境类型(F=7.471,P<0.05)及基质类型(F=3.205,P<0.05)的贮点密度具有显著差异。贮点数量、贮点更新率最高的是距离食物源最近的人工针叶林样地。贮食距离短、频繁更新贮点、冬季之前全部重取等行为特征,是星鸦对短暂爆发性集中食物源的适应。     

Molecular phylogeographic analyses and species delimitations reveal that Leopoldamys edwardsi (Rodentia: Muridae) is a species complex

Leopoldamys edwardsi is a species with wide distribution ranges in southern China but is not discussed in studies on geographic variation and species differentiation. We used 2 mitochondrial (Cytb, CO1) and 3 nuclear (GHR, IRBP and RAG1) genes to clarify species phylogeography and geographical differentiation. Maximum likelihood (ML) and Bayesian phylogenetic inference (BI) trees consistently indicated that L. edwardsi is a species complex containing 3 main lineages with high Kimura‐2‐parameter (K2P) divergences (i.e. lineages L_N, L_S and L_HN) found in the northern and southern China and Hainan Island, respectively. The 3 species delimitation methods, automated barcoding gap discovery, Bayesian poisson tree process analysis and Bayesian phylogenetics and phylogeography, consistently supported the existence of cryptic species. Divergence times among the main lineages were inferred to be during the Pleistocene, with L_HN/L_S split at 1.33 Ma and L_N/(L_HN+L_S) at 2.61 Ma; the diversifications of L. edwardsi complex might be caused by the rapid uplifts of Tibetan Plateau, paleoclimate change and complex topography. The divergence between L_HN and L_S was probably related to the separation of Hainan Island from the mainland via the formation of the Qiongzhou Strait. Lineages L_N and (L_S+L_HN) likely diverged due to the Wuyi‐Nanling mountain range forming a dispersal barrier. Our results suggested that L. edwardsi complex contains at least 3 distinct species: L_HN represents L. hainanensis, endemic to Hainan Island and previously considered as a subspecies L. e. hainanensis; L_S represents a cryptic species distributed throughout the southern Chinese continent; and L_N represents the nominotypical species L. edwardsi.     

Seasonal changes in the parasite prevalence of a small Malagasy lemur species (Lepilemur edwardsi)

Parasitic infections can impact the fitness of individuals and can have influence on animals’ population dynamics. An individuals’ parasite prevalence often changes depending on external or seasonal changes, for example, rainfall and ambient temperatures, but also on internal changes, for example, changes in body condition. In this study we aimed to identify the environmental factors that may influence the intestinal parasite and ectoparasite prevalence of the folivorous Malagasy primate species, Lepilemur edwardsi, living in a seasonal dry deciduous forest. Species living in this habitat have to adapt to seasonal changes of ambient temperature, with almost no precipitation during the dry season and hence strong fluctuations of resource availability throughout the year. We sampled the feces and ectoparasites of L. edwardsi throughout the year. Intestinal parasite prevalence increased from the wet to the dry season and was highest in the late dry season, which might be due to the accompanying decrease in diet quality. Conversely, ectoparasite prevalence decreased in the dry season, presumably due to the prevailing unfavorable environmental conditions for the development of ectoparasites (i.e., mites and ticks). Paired with the higher resting metabolism and stress level of L. edwardsi during the late dry season, it seems that this species may struggle when dry seasons intensify in its habitat.     

Seed value influences cache pilfering rates by desert rodents

Some rodents gather and store seeds. How many seeds they gather and how they treat those seeds is largely determined by seed traits such as mass, nutrient content, hardness of the seed coat, presence of secondary compounds, and germination schedule. Through their consumption and dispersal of seeds, rodents act as agents of natural selection on seed traits, and those traits influence how rodents forage. Many seeds that are scatter‐hoarded by rodents are pilfered, or stolen, by other rodents, and seed traits also likely influence pilfering rates and seed fates of pilfered seeds. To clarify coevolutionary relationships between rodents and the plants that they disperse, one needs to understand the role of seed traits in rodent foraging decisions. We compared how the seeds of 4 species of plants that are dispersed by scatter‐hoarding animals and that differ in value (singleleaf piñon pine, Pinus monophylla; desert peach, Prunus andersonii; antelope bitterbrush, Purshia tridentata; Utah juniper, Juniperus osteosperma) were pilfered and recached by rodents. One hundred artificial caches of the 4 seed species (25 per species) were prepared, and removal by rodents was monitored. Rodents pilfered high‐value seeds more rapidly than the other seeds. Desert peach seeds, which contain toxic secondary compounds, were more frequently recached. Relatively low value seeds like Utah juniper and antelope bitterbrush were pilfered more slowly and were sometimes left at cache sites, and seeds of the latter species were transported shorter distances to new cache sites. The background density of seeds also appeared to influence the relative value of seeds.     

Camera-trapping and seed-labelling reveals widespread granivory and scatter-hoarding of nuts by rodents in the Fynbos Biome

Many plant–animal interactions can be challenging to directly observe, due to species being small, cryptic and/or nocturnal. Previous research on seed predation and dispersal by rodents in the Fynbos Biome of South Africa has relied on indirect evidence, as methods for directly monitoring rodent–seed interactions were not available. The aims of the study were to determine which resident small mammals scatter-hoard nuts and the geographic, seasonal and taxonomic extent of scatter-hoarding in the Fynbos Biome. We used camera traps focused on seed stations at eight sites in the Fynbos Biome to determine the responses of small mammals to tagged nut-like fruits (nuts) of seven endemic plant species belonging to the Proteaceae (n = 3), Rosaceae (n = 2), Restionaceae (n = 1) and Cupressaceae (n = 1), as well as commercial sunflower seeds. We found Acomys subspinosus and Gerbilliscus paeba scatter-hoarded nuts, which they typically carried and buried individually. Rhabdomys pumilio and Micaelamys namaquensis only consumed nuts. Leucadendron pubescens and L. loranthifolium are added to the list of known plant species that are scatter-hoarded by rodents. Nuts of Cliffortia cuneata and C. phillipsii, and the critically endangered Widdringtonia cedarbergensis, were consumed but not dispersed by small mammals, whereas nuts of Ceratocaryum argenteum were neither consumed nor scatter-hoarded by rodents (within its native range). Gerbilliscus paeba and A. subspinosus scatter-hoarded nuts aseasonally, outside of seed-fall periods. Scatter-hoarding was widespread throughout the Fynbos Biome, although it was highly localised across and within sampled sites. The absence of scatter-hoarding rodents at sites with rodent-dispersed plants remains an important aspect for future investigation.     

Scatter‐hoarding rodents as secondary seed dispersers of a frugivore‐dispersed tree Scleropyrum wallichianum in a defaunated Xishuangbanna tropical forest,China

Local extinction or population decline of large frugivorous vertebrates as primary seed dispersers, caused by human disturbance and habitat change, might lead to dispersal limitation of many large‐seeded fruit trees. However, it is not known whether or not scatter‐hoarding rodents as secondary seed dispersers can help maintain natural regeneration (e.g. seed dispersal) of these frugivore‐dispersed trees in the face of the functional reduction or loss of primary seed dispersers. In the present study, we investigated how scatter‐hoarding rodents affect the fate of tagged seeds of a large‐seeded fruit tree (Scleropyrum wallichianum Arnott, 1838, Santalaceae) from seed fall to seedling establishment in a heavily defaunated tropical forest in the Xishuangbanna region of Yunnan Province, in southwest China, in 2007 and 2008. Our results show that: (i) rodents removed nearly all S. wallichianum seeds in both years; (ii) a large proportion (2007, 75%; 2008, 67.5%) of the tagged seeds were cached individually in the surface soil or under leaf litters; (iii) dispersal distance of primary caches was further in 2007 (19.6 ± 14.6 m) than that in 2008 (14.1 ± 11.6 m), and distance increased as rodents recovered and moved seeds from primary caches into subsequent caching sites; and (iv) part of the cached seeds (2007, 3.2%; 2008, 2%) survived to the seedling stage each year. Our study suggests that by taking roles of both primary and secondary seed dispersers, scatter‐hoarding rodents can play a significant role in maintaining seedling establishment of S. wallichianum, and are able to at least partly compensate for the loss of large frugivorous vertebrates in seed dispersal.     

Effects of melatonin on oocyte maturation in PCOS mouse model

The purpose of oocyte in vitro maturation is generation of mature oocytes that could support future development. Efforts have been made to enhance oocyte developmental competence by developing optimal culture conditions. The present study is conducted to determine melatonin effects on quality of polycystic ovarian syndrome (PCOS) oocytes when it has been added during in vitro maturation, and immature oocytes were cultured in defined conditioned medium with and without different melatonin concentrations. Melatonin could significantly improve nuclear maturation of PCOS oocytes (81.1% vs. 56.3%, P < 0.05 were achieved with 10^?6 mol/L concentration). Cleavage rate was significantly higher in 10^?5 mol/L concentration compared to untreated oocytes in PCOS (54% vs. 35%, respectively) and it was significantly higher with 10^?6 mol/L concentration in the control group, 55% versus 38%, compared to untreated oocytes. This study showed that melatonin has the potential to induce oocyte nuclear maturation and guarantee fertilization potential. © 2016 Japanese Society of Animal Science     

Comparison of pregnancy per AI of heifers inseminated with sex-sorted or conventional semen after oestrus detection or timed artificial insemination

The objective of the study was to compare the fertility after using sex-sorted or conventional semen either with oestrus detection (EST) or timed artificial insemination (TAI) in Holstein heifers. Holstein heifers were randomly assigned to one of the following treatments in a 2 × 2 factorial design. Heifers in the EST group were inseminated with sex-sorted (n = 114) or conventional semen (n = 100) after spontaneous or induced oestrus. Heifers in the TAI, subjected to the 5-day Cosynch+Progesterone protocol (GnRH+P4 insertion-5d-PGF_2α+P4 removal-1d-PGF_2α-2d-GnRH+TAI), were inseminated with sex-sorted (n = 113) or conventional semen (n = 88). Statistical analyses were performed using PROC GLIMMIX procedure of SAS 9.4 (SAS Institute Inc., Cary, NC). Overall P/AI was 60.7% for EST and 54.2% for TAI regardless of types of semen and 68.1% for conventional and 48.9% for sex-sorted semen regardless of insemination strategies. Fertility of heifers inseminated with either sex-sorted (53.5%; 44.2%) or conventional (69.0%; 67.0%) semen did not differ between EST and TAI respectively. Besides, the interaction between the semen type and the insemination strategy was not significant for P/AI. The embryonic loss was significantly greater with sex-sorted semen (17.1%) compared to conventional semen (1.6%). There was no sire effect with sex-sorted semen on P/AI (52.6% vs. 46.2%) and embryonic loss (16.4% vs. 18.0%). As expected, sex-sorted semen resulted in more female calves (89.8% vs. 51.6%) than conventional semen. Thus, sex-sorted semen can be used with 5-day Cosynch+Progesterone protocol to eliminate the inadequate oestrus detection and to increase female calves born in dairy heifers.     

A survey of the fish fauna of Transkei estuaries Part Three: The Mtata River estuary

The species composition, seasonal abundance and spatial distribution of the fish fauna of the Mtata estuary (8,5 km long) was determined by means of gill nets. Nine hundred and ninety fish (462,9 kg) comprising 26 species were caught of which M. cephalus (43,3%), A. hololepldotus (18,9%), P. commersonnii (7,9%), machnata (7,1%) and L. amia (5,45) were most abundant in terms of biomass. Mullet species constituted 48,3% of the biomass caught, representing 25,6% of the numbers. Seasonal patterns were ascertained for M. cephalus, M. capensis, V. buchanani, A. hololepidotus, P. commersonnii, P. kaakan, £ machnata, L. amia, J. dussumieri, T. vitrirostris and L. equula. A mean of 19,4 fish with a mean mass of 9,1 kg were caught per net per station. Numerically the highest catches were made in the upper reaches; gravimetrically in the middle reaches. Temperatures ranged from 10,5-25,5°C; a salinity gradient was usually present in all reaches; oxygen levels and turbidities were high.     

Reproductive Performance of Purebred Swedish Landrace and Swedish Yorkshire Sows: I. Seasonal Variation and Parity Influence

The objective of this retrospective study was to investigate the causes of variation in the reproductive performance of purebred Swedish Landrace (L) and Swedish Yorkshire (Y) sows. Data analysed comprised farrowings from 1994 through 1997 from 19 Swedish nucleus herds and included 20 275 litters from 6989 purebred sows (3598 L and 3491 Y). The main traits analysed were litter size, weaning-to-first-service interval (WSI), farrowing rate, remating rate and age at first farrowing. Analysis of variance was used for the statistical analysis of quantitative data. Logistic regression analysis was applied for binary data using the GLIMMIX macro in the SAS program. Factors included in the analyses were breed of sow, breed of boar, parity number, herd-year combination within breed, mating type (natural mating or artificial insemination), lactation length and month of the year. L sows, compared with Y sows, produced larger litters [11.61 vs 11.54 total born/litter (ns) and 10.94 vs 10.58 born alive/litter (P<0.001)] and had a longer WSI (5.5 vs 5.4 days, P<0.001), a higher farrowing rate (82.8 vs 80.9% units, P<0.05) and a lower remating rate (6.2 vs 8.8% units, P<0.001). On average, L sows were younger at first farrowing than Y sows (355.6 vs 368.6 days, P<0.001). The seasonal influence on WSI was greater for primiparous sows than for multiparous sows. Primiparous sows weaned from June to October had a longer WSI than those weaned from January to May or in November (P<0.05). Mating in August resulted in the lowest farrowing rate and the highest remating rate. The seasonal influence on farrowing rate and WSI was more pronounced in Y sows than in L sows. However, season had no significant influence on litter size in either L or Y sows.     

Effect of wilting on biochemical and microbiological changes in Kikuyu (Pennisetum clandestinum Hochst) silage

Small‐scale laboratory silos were used to study the fermentation process of Kikuyu (Pennisetum clandestinum Hochst) silage prepared from grass containing 25% and 40% dry matter. Silage made from grass containing 40% dry matter was found to be better preserved and of better quality than silage made from wetter grass. The better preservation and quality of the drier grass was reflected in the lower production of ammonia‐N (0,19 vs 0,26%) and total volatile fatty acids (5,48 vs 16,27%). Better quality was also reflected in the higher content of crude protein (16,3 vs 14,4%), true protein (9,0 vs 7,0%), residual total non‐structural carbohydrates (2,4 vs 2,3%), and in vitro dry matter digestibility (58,7 vs 55,2%). Both low and high dry matter silages had a low lactic‐acid content and high pH throughout fermentation. Both silages were of the acetate type.     

Effects of different rearing systems on muscle and meat quality traits of slow- and medium-growing male chickens

1. This experiment was conducted to evaluate the effect of production system on the meat quality of slow- and medium-growing chickens. A total of 1075 1-d-old male chicks were equally divided into 6 experimental groups, represented by three strains (SG: TETRA-H, MG1: TETRA HB Color, MG2: Shaver Farm) and were reared in a poultry house in floor pens (12 males/m²).

2. On d 49, 150 healthy birds (50/genotype) were placed in a free-range family farm while the rest of the birds remained indoors. All birds were fed ad libitum and consumed the same diet. On d 70, 20 birds of each experimental group were slaughtered and muscle samples were taken from the left breast and thigh muscles.

3. Thigh muscle of SG males kept on free range was darker (L* = 75.12 vs. 78.33) with lower frying loss (45.9% vs. 55.9%) compared with the indoor group. Similar results were obtained from the MG1 group. Free-range MG2 males had lighter thigh meat (L* = 50.7 vs. 57.8) and lower frying loss compared to the indoor group.

4. In general, the indoor treatment had a lower impact on breast meat than the outdoor system. Regardless of the rearing system, genotypic differences were more pronounced in thigh than in breast muscle.

     

A new rolling culture‐based in vitro fertilization system capable of reducing polyspermy in porcine oocytes

The high incidence of polyspermy is one of the major obstacles during in vitro fertilization (IVF) in pigs. To overcome this, we developed a novel IVF method, which involves constant rotation. Oocytes matured in vitro were mixed with spermatozoa (0.2 × 10⁵ sperm/mL) in an IVF medium (200 μL) using a 200 μL PCR tube. This tube was then rotated at 1 rpm for 6 h at 38.5°C in a rotation mixer (experimental group). A second PCR tube was simultaneously cultured without rotation (control group). The rate of polyspermy was evaluated 12 h after insemination and was significantly (P < 0.05; 21.0% vs. 48.3%) lower in the experimental group than in the control group. Sperm penetration rate was similar in oocytes from the experimental and control groups (75.2% vs. 83.1%). However, monospermic fertilization rate of the oocytes was significantly (P < 0.05; 44.8% vs. 21.2%) higher in the experimental group than in the control group. Furthermore, the rate of blastocyst formation (30.1% vs. 20.8%) increased in the experimental group, as compared to the control group. This present system will contribute to increase the efficacy of blastocyst production through reduction of polyspermic penetration.     

Interactions between metabolic status, pre-breeding protein supplementation, uterine pH, and embrionic mortality in ewes: Preliminary observations

The effect of prebreeding short-term protein supplementation level (PL) and body condition (BC) on fertility rate (FERT,%), uterine pH and embryonic mortality (EMORT,%) in sheep, was evaluated. Multiparous Rambouillet ewes at low BC (LC; n = 6, 62.7 ± 1.7 kg) or high BC (HC; n = 6, 71.9 ± 1.7 kg), received. within BC, one of two levels of ruminally undegradable protein: low (LP, 14 g/ewe per day) and high (HP, 30 g/ewe per day). Once the animals were euthanized, corpus luteum number (CLN), as an indicator of ovulation rate, was registered and uterine horns were irrigated to recover embryonic tissue plus associated membranes as well as to measure uterine pH (UpH). While EMORT-1 considered a nonadjusted relationship between the number of embryos and CLN, EMORT-2 considered an analysis of covariance using CLN as the covariate. The HP-supplemented ewes had the lowest FERT (p=0.06; 100% vs 50%) and the highest EMORT (EMORT-1, 16.6% vs 53.8%, p = 0.08; EMORT-2, 52.0% vs 14.5%, p = 0.07) when compared to the LP-supplemented ewes. Neither BC nor PL affected CLN, CL weight or P₄ release (p > 0.10). While the lowest UpH (p = 0.04) was observed in the HP-supplemented ewes, this group also showed the lowest fertility and the highest embryonic mortality.