Stillborn Kits Research Articles

Potential use of dimethyl sulfoxide (DMSO) in artificial insemination of rabbits

The aim of this work was to analyse the effect of incubation dimethyl sulfoxide (DMSO) with insemination dose (ID) on reproduction parameters (kindling rate, number of live and still-born kits and birth weight of kits). The experiments were carried out under the conditions of two rabbit breeds. An ejaculate was diluted to concentration of 40 to 50 million/0.5 ml/ID. DMSO was added to the ID in concentration of 0.5 M DMSO. Control ID did not contain any DMSO. Kindling rates obtained from 2 different breeds (P1, P2) showed minor improvement (+4.36% P1; +4.06% P2) between the monitored groups of females, however without statistically significant differences. Number of live born kits in litter obtained from breeds P1 and P2 showed minor improvement (+0.61 pcs P1; +0.13 pcs P2) compared to the control groups (p>0.05). The weight of live born kits was higher in experimental groups (+3.85 g P1 = p≤0.001; +1.18 g P2 = p>0.05) compared to the control groups. Monitoring of sperm quality indicators (1, 3 and 6 hours incubation) in vitro conditions (CASA – Computer Assisted Semen Analyzer) showed the best results in the control group of non-affected DMSO. The data obtained from our experiments suggest the possitive effects of DMSO incubation on reproduction parameters especially in vivo.

Polymorphism and association of progesterone receptor gene with milk production and reproductive traits of rabbits

Using the PCR RFLP method polymorphism and three different genotypes (AA, AG and GG) were detected in the progesterone receptor gene (PGR) promoter in a local Slovak crossbred rabbit line. We have noted a slightly majority frequency of allele A (0.53) over allele G (0.47). Comparing the observed and expected genotype frequencies with the χ<sup>2</sup> test the results were statistically significant, which means the tested rabbit population was non-equilibrium. The best results and significantly highest milk production (P < 0.001) were recorded in the does of GG genotype compared to AA genotype. Other association studies aimed at the effect of genotypes on litter size showed the highest litter size and number of weaned rabbits per litter in GG genotype. A significantly higher (P < 0.05) average number of stillborn kits per litter was in the group of does with AA genotype (0.62) compared with GG genotype (0.34).

A diet supplemented with n-3 polyunsaturated fatty acids influences the metabomscic and endocrine response of rabbit does and their offspring.

The aim of the present study was to evaluate the productive, endocrine, and metabomscic responses as well as oxidative stress of rabbit does and their offspring when fed a diet supplemented with -3 PUFA during their first productive cycle. To this aim, a total of 105 rabbit does were fed ad mscibitum from d 60 to 172 of age 2 isoenergetic and isoproteic diets differing in fatty acid composition. The control diet ( = 52 does) contained 45.9 g/kg of -3 of the total fatty acids and the enriched diet ( = 53 does) contained 149.2 g/kg of -3 of the total fatty acids. Both experimental groups had similar feed intake during rearing, pregnancy, and lactation. The enrichment of diet had no effect on ultrasonographic assessment of does on d 9 and 16 of pregnancy, with an embryonic vesicle number and fetus and placenta size similar between groups ( > 0.05). Even though there were no major effects ( > 0.05) on fertimscity, duration of gestation, and number born amscive and stillborn kits at parturition, mscive kits from enriched does were longer (71.6 ± 2.42 vs. 79.5 ± 2.13 mm; < 0.05) and tended to be heavier (42.5 ± 3.94 vs. 50.8 ± 3.47 g; = 0.07) than those from control does ( < 0.05). The 2 groups had similar milk production and mortamscity values during lactation; consequently, there were no differences between diets in ADG, mscitter weight, and number of weaned kits ( > 0.05). In enriched does, higher plasma leptin and estradiol concentrations than in control does ( < 0.05) were observed. In addition, enriched females also had lower total and high-density mscipoprotein cholesterol (HDL-c) than control females during lactation ( < 0.05). Regarding offspring, the enrichment of diet with PUFA caused a hypermscipidemic status (greater values of plasma triglycerides, total cholesterol, and HDL-c; < 0.05) at 1 d postpartum (dpp), compared with the control group, that disappeared at 32 dpp. Supplemented does before parturition and their offspring at 1 dpp had greater oxidative stress than those in the control group. In conclusion, an increase of -3 PUFA concentration in the diet of rabbit does and, consequently, of their offspring during a productive cycle alters their mscipid profile and the indicators of oxidative stress, without major endocrine modifications or improvements in the productive variables.

Influence of gestational maternal feed restriction on growth performance and meat quality of rabbit offsprings

The purpose of the present study was to evaluate the effect of feed restriction during pregnancy on reproductive performance of rabbit does and growth performance and meat quality of their offspring. A total of 26 primiparous non lactating does were equally divided into two treatment groups: the control group (C, n=13) that was fed ad libitum throughout gestation and the feed restricted group (R, n=13) that was fed to 75% of maintenance energy requirements from the 7th to the 26th day of gestation. Rabbit offsprings were weaned at 35 days of age and grown until the 72 days of age when they were slaughtered for meat quality assessment. Meat quality traits measured were pH24, colour (L*, a*, b*), percentage of released water, cook loss, shear values and intramuscular fat. At kindling, R does produced smaller litter weights compared with those of does from group C, 447.8 and 591.4 g, respectively, and smaller individual kit birth weights, 56.2 and 71.5 g, respectively (P<0.05). Ratio of stillborn kits and mortality rate from parturition until weaning was higher (P<0.05) in the R group, 21.4% and 11.1%, respectively, in comparison with the C group, 8.1% and 3.5%, respectively. Litter size and gestation length were unaffected by maternal undernutrition. Kit birth weight treatment differences were eliminated at weaning because of compensatory growth (P>0.05). Performance and meat quality characteristics of fattening rabbits at 72 days of age were not influenced by gestational feed restriction of their mothers (P>0.05). Taking into consideration that, simultaneous gestation and lactation in rabbit does may be simulated by gestational feed restriction, results of the present study suggest that lactating does can support a simultaneous gestation without any adverse effect on the offsprings’ quantitative and qualitative performance at the expense of increased mortality rates at parturition and until weaning.

Effects of Gestational Maternal Undernutrition on Growth, Carcass Composition and Meat Quality of Rabbit Offspring

An experiment was conducted in order to evaluate the effects of gestational undernutrition of rabbit does on growth, carcass composition and meat quality of the offsprings. Thirty primiparous non lactating rabbit does were artificially inseminated and randomly divided in three treatment groups: Control (C; fed to 100% of maintenance requirements throughout gestation, n = 10), early undernourished (EU; fed to 50% of maintenance requirements during days 7–19 of gestation, n = 10) and late undernourished (LU; fed to 50% of maintenance requirements during days 20-27 of gestation, n = 10). During the 4th week of the gestation period, LU does significantly lost weight compared to C and EU groups (P<0.05). At kindling, C does produced litters with higher proportions of stillborn kits (P<0.05) while the total litter size (alive and stillborn kits) was not different among groups (10.7, 12.8 and 12.7 kits in C, EU and LU groups, respectively). Kit birth weight tended to be lower in the LU group. During fattening, body weight and feed intake were not different among offsprings of the three experimental groups. Moreover, the maternal undernutrition did not have any impact on carcass composition of the offsprings in terms of carcass parts and internal organs weights as well as meat quality of L. lumborum muscle (pH24, colour, water holding capacity and shear values) at slaughter (70 days of age). Therefore, it can be concluded that the gestational undernutrition of the mother does not have detrimental effects on the productive and quality traits of the offsprings.

Dietary exposure of mink (Mustela vison) to fish from the upper Hudson River, New York, USA: Effects on reproduction and offspring growth and mortality

The effects of feeding farm-raised mink (Mustela vison) diets containing polychlorinated biphenyl (PCB)-contaminated fish from the upper Hudson River (New York, USA) on adult reproductive performance and kit growth and mortality were evaluated. Diets contained 2.5 to 20% Hudson River fish, providing 0.72 to 6.1 µg ∑PCBs/g feed (4.8-38 pg toxic equivalents [TEQWHO 2005 ]/g feed). The percentage of stillborn kits per litter was significantly increased by dietary concentrations of 4.5 µg ∑PCBs/g feed (28 pg TEQWHO 2005 /g feed) and greater. All offspring exposed to dietary concentrations of 4.5 and 6.1 µg ∑PCBs/g feed (28 and 38 pg TEQWHO 2005 /g feed) died by 10 weeks of age, and all offspring exposed to 1.5 and 2.8 µg ∑PCBs/g feed (10 and 18 pg TEQWHO 2005 /g feed) died by 31 weeks of age, leaving juveniles in the control and 0.72 µg ∑PCBs/g feed (0.41- and 4.8 pg TEQWHO 2005 /g feed) groups only. The dietary concentration predicted to result in 20% kit mortality (LC20) at six weeks of age was 0.34 µg ∑PCBs/g feed (2.6 pg TEQWHO 2005 /g feed). The corresponding maternal hepatic concentration was 0.80 µg ∑PCBs/g liver, wet weight (13 pg TEQWHO 2005 /g liver, wet wt). Mink residing in the upper Hudson River would be expected to consume species of fish that contain an average of 4.0 µg ∑PCBs/g tissue. Thus, a daily diet composed of less than 10% Hudson River fish could provide a dietary concentration of ∑PCBs that resulted in 20% kit mortality in the present study.

Maternal behaviour in peripartum influences preweaning kit mortality in cage-bred wild rabbits.

This study describes and models maternal nest-building and parturition behaviour in cage-bred wild rabbits (oryctolagus cuniculus), and its influence on the kits’ pre-weaning mortality. In a total of 91 litters, perinatal mortality was 33%; mortality during the nursing period was 16.05%, and therefore the accumulated mortality up to weaning was 43.94%. These mortality rates, higher than those described in the literature among domestic breeds, were linked to failures in maternal behaviour. Such failures included the non-introduction of straw into the nest box (41.8% of births), a lack of hair lining in the nest (28.6%), births in which one or all of the kits were born outside the nest box (18.7%), and births in which one or all of the kits were cannibalised by the doe (13.2%). Maternal behaviour in relation to the kits’ viability was modelled by performing multiple correspondence and cluster analyses with two dimensions and a 67.2% total inertia. The fi rst dimension (inertia: 0.400) was represented by the presence of hair in the nest box; the place where the kits were born (inside or outside the nest box), and the doe’s previous experience (primiparous or multiparous), while the total number of kits born represents the second dimension (inertia: 0.272). Three maternal behaviour types were identified: types 1 and 3 representing births in which the failure of maternal behaviour at kindling led to high kit mortality. Maternal behaviour type 1 corresponds to primiparous does of parity orders 1 and 2 with a high number of total kits born and of stillborn kits. Type 3 births were characterised by all of the kits died during peripartum, with a high incidence of cannibalism. Type 2 included births of experienced does showing successful development of maternal behaviour, as well as high kits’ survival rates during the peripartum and nursing periods. Although wild rabbits are subject to the same modulating factors in the development of the maternal repertoire as domestic does, showed a lower preweaning viability due to the failure to display maternal behaviour during peripartum.&lt;p class="MsoNormal"&gt; &lt;/p&gt;

Oestrus synchronisation of rabbit does at early post-partum by doe–litter separation or ECG injection: Reproductive parameters and endocrine profiles

Inseminating rabbit does at early post-partum, in combination with early weaning, can increase prolificacy (total kits born and still born per parturition) and decrease parturition intervals. Oestrus synchronisation increases fertility and prolificacy, while decreasing the number of inseminations required for gestation. However, little is known about the effectiveness of different oestrus synchronisation methods at early post-partum. In this study, does ( n = 138) were artificially inseminated nine times (over a period of 1 year, kits weaned at 25 days), on day 4 post-partum after separation from the litter (for 48 or 24 h) or 48 h after 25 UI eCG injection. Plasma levels of prolactin and estradiol were also evaluated in a subsample of 12 multiparous lactating does per treatment, on days 2, 3 and 4 post-partum. The three treatments increased overall fertility of multiparous females compared to controls (which were not synchronised), but there were no differences among treatments in total kits born or stillborn. Does treated with eCG had a higher culling rate. The interval between parturitions and the number of inseminations required for gestation tended to decrease with increasing number of inseminations. In lactating does, there was an interaction between treatment and insemination order. Fertility decreased with increasing inseminations in eCG does but tended to increase above control values in the separated does until the fourth insemination. Control lactating does had significantly less kits per parturition compared to treatments, but eCG lactating does had more stillborn kits. Oestradiol levels increased on day 4 post-partum in all synchronised lactating does (and immediately before artificial insemination in 48 h doe–litter separation), so ovarian activity could be stimulated at early post-partum using all treatments. However, the increase could not be explained by prolactin levels, since there were no effects of suckling absence on plasma prolactin in separated does. In conclusion, separating does from the litter before insemination can be just as effective as eCG treatment, especially during for the first four inseminations.

The effect of level of feeding in early gestation on reproductive success in young rabbit does

An experiment examined the effect of restricted feeding during early gestation on later feed intake and on kindling performance in young rabbit does. Nulliparous rabbit does ( n=94) were inseminated at 14.5 weeks of age. During the first 10 days of gestation, does were fed individually either to appetite (AL) or 1.35 times maintenance requirement (R). After 10 days of gestation, all animals were fed to appetite. Does were weighed at insemination and after kindling. Feed intake was recorded during the first 10 days of gestation and weekly, thereafter. The number of does that kindled, number of live and stillborn kits and litter weight was recorded. The experiment ended after kindling. During feed restriction, AL does consumed 70 g/day more on an average than R does (209 and 139±4 g for AL and R, respectively; P<0.001). In the first and second week after feed restriction, compensatory feed intake occurred. Restrictive fed does ate more than AL does (+34±5 g/day from days 11 to 17 of gestation; P<0.001; +17±6 g/day from days 18 to 24 of gestation; P<0.05). In the last week of gestation, feed intake of AL and R was comparable (89 and 100±5 g, respectively). At kindling, AL does had consumed 8±3 g/day more feed over the total gestation period than R does ( P<0.04). Feeding level during early gestation neither affected the kindling rate (83%), total litter size (7.9±0.4) nor the number of does with stillborn kits (10 versus 9 for AL and R, respectively). Regardless of treatment, in the last week of gestation (days 25–32) the number of does with stillbirth was lower and average birth weight was higher ( P<0.01) in does eating more than the average daily feed intake compared to does eating below average. Based on the results of this study it was concluded that feed restriction for 10 days in early gestation does not affect kindling performance of young does, but feed intake in the last week of gestation affects kit survival and birth weight.

An Outbreak of Toxoplasmosis in Farmed Mink (Mustela Vison S.)

A large Wisconsin mink (Mustela vison) farm experienced an outbreak of toxoplasmosis in the spring of 1999 following an outbreak of canine distemper during the previous fall. Major clinical signs for pregnant females included reduced feed consumption, abortions, and stillborn kits; kits < or =3 weeks old experienced ataxia and mortality. Of 7,800 females, 1,976 (26%) lost their entire litter either from abortion or neonatal mortality. Kit mortality from 7 days to 3 weeks of age was 3,300, and overall kit mortality attributed to the toxoplasmosis outbreak was 10,408. Six neonatal mink kits, 12 3-week-old kits, and 2 adult female mink were submitted to the University of Minnesota Veterinary Diagnostic Laboratory for diagnostic workup. Gross postmortem lesions were limited to empty stomachs (12 of 12 kits) and pale livers (4 of 12 kits) for the 3-week-old kits. Major microscopic lesions included interstitial pneumonia, encephalitis, encephalomalacia, and myocarditis. Toxoplasmosis was diagnosed by microscopic lesions, microscopic lesion distribution, and the detection of Toxoplasma gondii tachyzoites by immunohistochemistry. This is the first detailed report of an outbreak of toxoplasmosis in mink in the United States.

The effect of litter size before weaning on subsequent body development, feed intake, and reproductive performance of young rabbit does.

An experiment was performed to study the effect of litter size before weaning on subsequent body development and composition, feed intake, and reproductive performance of young rabbit does with the objective to improve reproductive performance. Litter size (LS) before weaning (treatment) was 6, 9, or 12 kits. After weaning (30 d), 58 female kits per treatment (in two successive replicates) were reared and fed for ad libitum intake to 14.5 wk of age (end of rearing). At 14.5 wk of age, receptive does were inseminated. Nonreceptive and nonpregnant does were inseminated at 17.5 wk of age. The experiment ended when the second litter was weaned. Part of the animals was slaughtered to determine body composition at the end of the experiment (replicate one) and at the end of rearing (replicate two). At weaning, BW differed among treatments (P < 0.05; 855, 773, and 664 +/- 15 g for LS6, 9, and 12, respectively). Compensatory growth was observed. At the end of rearing, LS12 does were smaller (P < 0.05) than LS9 and LS6 does (3,524, 3,778, and 3,850 +/- 48 g, respectively). After first lactation, no difference in BW among treatments was found. Compared with LS6, empty body weight (BW minus gut, bladder, and uterus content) of LS12 contained more (P < 0.05) nitrogen (32.5 vs 31.1 +/- 0.3 g/kg), more (P < 0.05) ash (30.7 vs 28.3 +/- 0.6 g/kg), and less (P < 0.05) fat (168.6 vs 200.2 +/- 8.6 g/kg). No differences in body composition among treatments were found at the end of the experiment. During rearing, LS12 had the lowest (P < 0.05) daily feed intake (152, 164, and 169 +/- 2 g/d for LS12, 9, and 6, respectively). During the reproductive period, no differences in feed intake among treatments were found. Kindling rate (the number of kindlings per number of inseminations) was not influenced by treatment. In the first parity, total litter size (number of alive and stillborn kits) was lower (P < 0.10) for LS12 than for LS9 (6.4 vs 8.6 +/- 0.5, respectively). When first mating was delayed by 3 wk, an increased (P < 0.05) total litter size was found regardless of treatment (7.5 and 9.4 +/- 0.3 for 14.5, and 17.5 wk, respectively). Decreasing litter size before weaning from nine to six kits did not alter future reproductive performance. Based on results of this study, it seems advisable to perform a limited standardization level (at nine kits) after kindling and postpone first mating to an older age (17.5 wk) to improve reproductive performance.

Postnatal Development in Mink Kits

Abstract The relative growth rate of mink kits during the 42 day lactation period was evaluated. Postnatal development, including chemical composition of the body, relative weights of liver and digestive tracts, liver glycogen, plasma glucose and cortisol, was studied from birth until 5–6 days of age. A maximum relative growth rate of 23%/d was recorded between 1 and 2 days of age. The average over 42 days was 9%/d. Body fat content increased from 1.4% at birth to 4.4% at 5 days of age. Stillborn kits tended to have a lower fat content than live born. Nutrient and energy retention data indicated a ten-fold increase in fat, a doubled protein content, and a three-fold increase in energy retained from birth until 5 days of age. The liver and digestive tract made up 3.5 and 5.6% of body weight at birth, respectively, a ratio that increased to 5% (liver) and 6.5% (digestive tract) from 3 and 2 days of age. Liver glycogen tended to be lower in dead than in live kits and tended to increase from 1 to 2 and 3 days...

A survey on perinatal mortality in young mink

The incidence of perinatal mortality in mink was investigated in commercial farms in Argentina. Of a total of 2122 kits, 548 of those that were born alive died within the first four weeks of life (25.8% mortality) and there were also 62 stillborn kits. Death resulted from a variety of causes of which septicaemia, starvation and hypothermia were the most common conditions. The highest mortality occurred within the first week of life (61.9%). The lesions found in young kits at post-mortem examination are described and related to contributory factors such as weight, litter size and age at death.

Flushing of mink. Effects of level of preceding feed restriction and length of flushing period on reproductive performance

In an experiment with 200 standard mink females (five groups of 40 females) the effect of flushing (a period of restriction followed by refeeding preceding the mating season) on reproductive performance was evaluated. The results of a non-flushed control group were compared with flushing from 20 February or 4 March until mating. For each date for start of flushing, the flushing period was preceded by a 2-week period of either moderate or severe restriction. Reproductive results confirm earlier data in that flushing from March 4, preceded by a 2-week period of moderate restriction, resulted in improved litter sizes (with 1.2 kits on average). Flushing from February 20 was less efficient. When comparing level of restriction, severely restricted females responded less to flushing than did moderately restricted females. The experimental treatment did not affect readiness to mate and the frequency of barren females was not conclusively affected. The rate of stillborn kits was not significantly affected but the highest rate was recorded in the group with superior litter size. In this investigation, both yearlings and adult females responded similarly to flushing.