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1.
The aim of this study was to examine the metabolic response to feed deprivation up to 48 h in low and high yielding lamb genotypes. It was hypothesised that Terminal sired lambs would have decreased plasma glucose and increased plasma non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHOB) concentrations in response to feed deprivation compared to Merino sired lambs. In addition, it was hypothesised that the metabolic changes due to feed deprivation would also be greater in progeny of sires with breeding values for greater growth, muscling and leanness. Eighty nine lambs (45 ewes, 44 wethers) from Merino dams with Merino or Terminal sires with a range in Australian Sheep Breeding Values (ASBVs) for post-weaning weight (PWT), post-weaning eye muscle depth and post-weaning fat depth (PFAT) were used in this experiment. Blood samples were collected via jugular cannulas every 6 h from time 0 to 48 h of feed deprivation for the determination of plasma glucose, NEFA, BHOB and lactate concentration. From 12 to 48 h of feed deprivation plasma glucose concentration decreased (P < 0.05) by 25% from 4.04 ± 0.032 mmol/l to 3.04 ± 0.032 mmol/l. From 6 h NEFA concentration increased (P < 0.05) from 0.15 ± 0.021 mmol/l by almost 10-fold to 1.34 ± 0.021 mmol/l at 48 h of feed deprivation. Feed deprivation also influenced BHOB concentrations and from 12 to 48 h it increased (P < 0.05) from 0.15 ± 0.010 mmol/l to 0.52 ± 0.010 mmol/l. Merino sired lambs had a 8% greater reduction in glucose and 29% and 10% higher NEFA and BHOB response, respectively, compared to Terminal sired lambs (P < 0.05). In Merino sired lambs, increasing PWT was also associated with an increase in glucose and decline in NEFA and BHOB concentration (P < 0.05). In Terminal sired lambs, increasing PFAT was associated with an increase in glucose and decline in NEFA concentration (P < 0.05). Contrary to the hypothesis, Merino sired lambs showed the greatest metabolic response to fasting especially in regards to fat metabolism.  相似文献   

2.
The aim of this experiment was to evaluate the impact of selection for greater muscling on the adrenaline responsiveness of muscle, adipose and liver tissue, as reflected by changes in plasma levels of the intermediary metabolites lactate, non-esterified fatty acids (NEFA) and glucose. This study used 18-month-old steers from an Angus herd visually assessed and selected for divergence in muscling for over 15 years. Ten low muscled (Low), 11 high muscled (High) and 3 high muscled heterozygotes for myostatin mutation (High(Het)) steers were challenged with adrenaline doses ranging between 0.2 to 3.0 μg/kg live weight. For each challenge, 16 blood samples were taken between -30 and 130 min relative to adrenaline administration. Plasma was analysed for NEFA, lactate and glucose concentration and area under curve (AUC) over time was calculated to reflect the tissue responses to adrenaline. Sixteen basal plasma samples from each animal were also assayed for growth hormone. Muscle glycogen and lactate concentration were analysed from four muscle biopsies taken from the semimembranosus, semitendinosus and longissimus thoracis et lumborum of each animal at 14, 90 and 150 days on an ad libitum grain-based diet and at slaughter on day 157. In response to the adrenaline challenges, the High steers had 30% lower lactate AUC than the Low steers at challenges greater than 2 μg/kg live weight, indicating lower muscle responsiveness at the highest adrenaline doses. Aligning with this decrease in muscle response in the High animals were the muscle glycogen concentrations which were 6.1% higher in the High steers. These results suggest that selection for muscling could reduce the incidence of dark, firm, dry meat that is caused by low levels of glycogen at slaughter. At all levels of adrenaline challenge, the High steers had at least 30% greater NEFA AUC, indicating that their adipose tissue was more responsive to adrenaline, resulting in greater lipolysis. In agreement with this response, the High steers had a higher plasma growth hormone concentration, which is likely to have contributed to the increased lipolysis evident in these animals in response to adrenaline. This difference in lipolysis may in part explain the reduced fatness of muscular cattle. There was no effect of selection for muscling on liver responsiveness to adrenaline.  相似文献   

3.
The rate of oxidation of the carboxyl and methyl carbons of [14C]methionine to CO2 by homogenates of liver, kidney cortex, pancreas, muscle and small intestinal mucosa was studied in two breeds of sheep (Merino and Poll Dorset Horn) at three ages (2 weeks, 3 months, 4 years). Sodium alpha-keto-gamma- methiolbutyrate (0 X 4 mM) stimulated production of CO2 from the carboxyl carbon of methionine, but not from the methyl carbon. Sodium pyruvate did not affect the recovery of CO2 from either carboxyl or methyl of methionine. Sodium formate (15 mM) suppressed the conversion of the methyl carbon of methionine to CO2 by liver and kidney homogenates to 4 and 50%, respectively, of control values, but did not affect the percentage of carboxyl carbon of methionine recovered in CO2 with either tissue. With addition of S-methyl-L-cysteine (40 mM) and 3- methylthiopropionate (10 mM) the percentage of methyl and carboxyl carbons recovered in CO2 was reduced to about 20% of control values in homogenates of both tissues. Activity per gram of tissue was higher in liver and kidney cortex than in pancreas, intestinal mucosa, or muscle, with no significant differences due to breed (Merino or Poll Dorset Horn) or sex (ewe, ram or wether) of sheep. Conversion of both the carboxyl and methyl carbons to CO2 by liver was significantly lower in 2-week-old lambs than in older animals (P less than 0.01). The activity of other tissues was not markedly affected by age. Results are discussed in relation to evidence of alternative pathways of methionine catabolism, and capacities of the tissues of the sheep to catabolize methionine by alternative pathways.  相似文献   

4.
A genome scan was conducted to map the autosomal recessive lethal disorder brachygnathia, cardiomegaly and renal hypoplasia syndrome (BCRHS) in Poll Merino sheep. The scan involved 10 affected and 27 unaffected animals from a single Poll Merino/Merino sheep flock, which were genotyped with the Illumina Ovine SNP50 BeadChip. Association and homozygosity mapping analyses located the disorder in a region comprising 20 consecutive SNPs spanning 1.1 Mb towards the distal end of chromosome OAR2. All affected animals and none of the unaffected animals were homozygous for the associated haplotype in this region. These results provide the basis for identifying the causative mutation(s) and should enable the development of a DNA test to identify carriers in the Poll Merino sheep population. Understanding the molecular control of BCRHS may provide insight into the fundamental genetic control and regulation of the affected organ systems.  相似文献   

5.
研究选择了与产肉性能相关的5个微卫星标记,分析了这5个位点在杜泊、德国美利奴、特克塞尔、道塞特和右玉本地绵羊5个品种中的遗传多态性.通过遗传分析预测了4个国外引进肉用绵羊品种与右玉本地绵羊的杂种优势,并与实际测定结果进行了比较分析.结果表明,利用微卫星DNA多态性进行品种间杂种优势预测是可行的,杜泊羊与右玉本地绵羊杂交的杂种优势最大,与实际测定结果一致.  相似文献   

6.
LoinMAX (LM) is a quantitative trait locus (QTL), which was found to be segregated in Australian Poll Dorset sheep, and maps to the distal end of sheep chromosome 18. LM-QTL was reported to increase Musculus longissimus dorsi area and weight by 11% and 8%, respectively. The aim of this study was to comprehensively evaluate the direct effects of LM-QTL in a genetic background typical of the stratified structure of the UK sheep industry, before it can be recommended for use in the United Kingdom. Crossbred lambs, either non-carriers or carrying a single copy of LM-QTL, were produced out of Scottish Mule ewes (Bluefaced Leicester × Scottish Blackface) artificially inseminated with semen from two Poll Dorset rams that were heterozygous for LM-QTL. Unexpectedly, one of these rams was also heterozygous for a QTL that affects the overall carcass muscling (MyoMAX™). This was accounted for by nesting MyoMAX™ status (carrier or non-carrier) within sire in the statistical analysis. Lambs were weighed and scanned by using X-ray computed tomography (CT) at an average age of 113 days. Ultrasound scan measurements, along with lamb weights, were taken at an average age of 140 days and lambs were then slaughtered. Carcasses were weighed and classified for fat cover and conformation scores, based on the Meat and Livestock Commission (MLC) carcass classification scheme, and then scanned by using a video image analysis (VIA) system. M. longissimus lumborum (MLL) width, as measured by CT scanning, was greater (P < 0.05) in lambs heterozygous for LM-QTL compared with non-carriers. MLL in LM-QTL carrier lambs was also significantly deeper, as measured by both ultrasound muscle depth at the third lumbar vertebrae (+3.7%; P < 0.05) and CT scanning at the fifth lumbar vertebrae (+3.4%; P < 0.01). Consequently, MLL area, was measured by using CT scanning, was significantly higher (+4.5%; P < 0.01) in lambs carrying a single copy of LM-QTL compared with non-carriers. Additional traits measured by CT, such as leg muscle dimensions, average muscle density and tissue proportions, were not significantly affected by LM-QTL. LM-QTL did not significantly affect total carcass lean or fat weights or MLC conformation and fat score classifications. Using previously derived algorithms, VIA could detect a significant effect of the LM-QTL on the predicted weight of saleable meat yield in the loin primal cut (+2.2%; P < 0.05), but not in the other primal cuts, or the total carcass.  相似文献   

7.

Background

The accuracy of genomic prediction depends largely on the number of animals with phenotypes and genotypes. In some industries, such as sheep and beef cattle, data are often available from a mixture of breeds, multiple strains within a breed or from crossbred animals. The objective of this study was to compare the accuracy of genomic prediction for several economically important traits in sheep when using data from purebreds, crossbreds or a combination of those in a reference population.

Methods

The reference populations were purebred Merinos, crossbreds of Border Leicester (BL), Poll Dorset (PD) or White Suffolk (WS) with Merinos and combinations of purebred and crossbred animals. Genomic breeding values (GBV) were calculated based on genomic best linear unbiased prediction (GBLUP), using a genomic relationship matrix calculated based on 48 599 Ovine SNP (single nucleotide polymorphisms) genotypes. The accuracy of GBV was assessed in a group of purebred industry sires based on the correlation coefficient between GBV and accurate estimated breeding values based on progeny records.

Results

The accuracy of GBV for Merino sires increased with a larger purebred Merino reference population, but decreased when a large purebred Merino reference population was augmented with records from crossbred animals. The GBV accuracy for BL, PD and WS breeds based on crossbred data was the same or tended to decrease when more purebred Merinos were added to the crossbred reference population. The prediction accuracy for a particular breed was close to zero when the reference population did not contain any haplotypes of the target breed, except for some low accuracies that were obtained when predicting PD from WS and vice versa.

Conclusions

This study demonstrates that crossbred animals can be used for genomic prediction of purebred animals using 50 k SNP marker density and GBLUP, but crossbred data provided lower accuracy than purebred data. Including data from distant breeds in a reference population had a neutral to slightly negative effect on the accuracy of genomic prediction. Accounting for differences in marker allele frequencies between breeds had only a small effect on the accuracy of genomic prediction from crossbred or combined crossbred and purebred reference populations.  相似文献   

8.
We determined the polymorphism C242T of the aromatase gene (Cyp19) and its allelic frequency, as well as the effect of the variants on productive and reproductive traits in 71 purebred Santa Inês sheep, 13 purebred Brazilian Somali sheep, nine purebred Poll Dorset sheep, and 18 crossbred 1/2 Dorper sheep. The animals were genotyped using the PCR-RFLP technique. The influence of the animal's genotype on its performance or on the performance of its lambs was analyzed by the least square method. Another factor assessed was the importance of the animal's genotype in analysis models for quantitative breeding value estimates, and whether there were differences among the averages of breeding values of animals with different genotypes for this gene. In the sample studied, no AA individuals were observed; the AB and BB frequencies were 0.64 and 0.36, respectively. All Brazilian Somali sheep were of genotype BB. All 1/2 Dorper BB animals presented a lower age at first lambing, and the Santa Inês BB ewes presented a lower lambing interval. In these same genetic groups, AB ewes presented higher litter weight at weaning. This is evidence that BB ewes have a better reproductive performance phenotype, whereas AB ewes present a better maternal ability phenotype. However, in general, animals with genotype AB presented better average breeding values than those with genotype BB.  相似文献   

9.
The objective of this study was to determine the effect of a single generation of artificial selection for sexual performance in rams on the sexual behavior and fecundity of their male and female progeny. Ninety-two ram lambs born to sires selected for either high or low sexual performance were evaluated for their sexual behaviors at approximately 8 months of age when individually exposed to four estrous ewes for 30min in four weekly serving capacity tests. Number of mounts and successful matings (ejaculations) were recorded. Fourteen of the 17 high-performing ram lambs identified were sired by high-performing sires, whereas 22 of 37 low-performing ram lambs were sired by low-performing sires (P<0.01). Sons of high-performing sires exhibited more ejaculations (P<0.04) and more mounts without ejaculation (P<0.02) than sons of low-performing sires. The two groups of ram lambs did not differ in mating efficiency (ratio of ejaculations to total mounts). Daughters of high-performing rams (N=79) exhibited their first behavioral estrus approximately 8 days earlier than daughters (N=61) of low-performing sires (P<0.005). Ovulation rates for the two groups of ewe lambs did not differ (P=0.55). It was concluded that there was sufficient genetic variation in the population of sheep studied to obtain a significant response to selection for ram sexual performance in both male and female offspring in a single generation.  相似文献   

10.
The Ram Genotyping Scheme was launched in Great Britain in 2001 as part of the National Scrapie Plan and was devised to reduce and eventually eradicate classical scrapie susceptible genotypes from the national pedigree flock. Anecdotal claims from breeders suggest that sheep with more resistant PrP genotypes may have inferior phenotypes. In this study, we test this possibility for lamb production traits in three breeds of lowland sheep: Charollais (22 752 lambs), Poll Dorset (22 589 lambs) and Texel (23 492 lambs). Data were received from 50 breeders and comprised weights at birth, 8 weeks and scanning (from which average daily weight gain was derived), and ultrasonic muscle and fat depths. Animal (direct) genetic effects and up to three maternal effects were fitted in linear mixed models for each trait. Fitting either PrP genotype or number of copies of individual alleles carried as fixed effects allowed potential associations with the PrP gene to be assessed. There were no significant associations seen in the Poll Dorset breed; however, significant associations were found with the number of allele copies carried in the other two breeds included in this study. Charollais lambs carrying one copy of the VRQ allele had significantly (P < 0.01) greater ultrasonic muscle depth (0.58 mm) and fat depth (0.2 mm) than non-carriers. In the Texel breed, lambs with one ARR allele were significantly heavier than those with two or zero ARR alleles; heterozygous ARR lambs were 0.07 kg heavier at birth (P < 0.05), 0.42 kg heavier at 8 weeks (P < 0.01) and 0.17 kg heavier at scan weight (P < 0.01), than non-carriers. After Bonferroni corrections to adjust significance thresholds to account for the large number of independent comparisons made, all significant results remained so at P < 0.05 or greater, except for the ARR allele effect on birth weight in the Texel breed, which was no longer significant. These results compare favourably with others from studies on many continental breeds of sheep, published in recent years, and add credence to the conclusion that selection on PrP genotype is unlikely to have any noticeable impact on the measured growth and carcass traits in sheep.  相似文献   

11.
TM-QTL is a quantitative trait locus (QTL) on ovine chromosome 18 (OAR18) known to affect loin muscling in Texel sheep. Previous work suggested that its mode of inheritance is consistent with paternal polar overdominance, but this has yet to be formally demonstrated. This study used purebred Texel sheep segregating for TM-QTL to confirm its presence in the chromosomal region in which it was first reported and to determine its pattern of inheritance. To do so, this study used the first available data from a Texel flock, which included homozygote TM-QTL carriers (TM/TM; n=34) in addition to homozygote non-carriers (+/+; n=40 and, heterozygote TM-QTL-carriers inheriting TM-QTL from their sire (TM/+; n=53) or their dam (+/TM; n=17). Phenotypes included a wide range of loin muscling, carcass composition and tissue distribution traits. The presence of a QTL affecting ultrasound muscle depth on OAR18 was confirmed with a paternal QTL effect ranging from +0.54 to +2.82 mm UMD (s.e. 0.37 to 0.57 mm) across the sires segregating for TM-QTL. Loin muscle width, depth and area, loin muscle volume and dissected M. longissimus lumborum weight were significantly greater for TM/+ than +/+ lambs (+2.9% to +7.9%; P<0.05). There was significant evidence that the effect of TM-QTL on the various loin muscling traits measured was paternally polar overdominant (P<0.05). In contrast, there was an additive effect of TM-QTL on both live weight at 20 weeks and carcass weight; TM/TM animals were significantly (P<0.05) heavier than +/+ (+11.1% and +7.3%, respectively) and +/TM animals (+11.9% and +11.7%, respectively), with TM/+ intermediate. Weights of the leg, saddle and shoulder region (corrected for carcass weight) were similar in the genotypic groups. There was a tendency for lambs inheriting TM-QTL from their sire to be less fat with slightly more muscle than non-carriers. For example, carcass muscle weight measured by live animal CT-scanning was 2.8% higher in TM/TM than +/+ lambs (P<0.05), carcass muscle weight measured by carcass CT-scanning was 1.36% higher in TM/+ than +/+ lambs (P<0.05), and weight of fat trimmed from the carcass cuts was significantly lower for TM/+ than +/+ lambs (−11.2%; P<0.05). No negative effects of TM-QTL on carcass traits were found. Optimal commercial use of TM-QTL within the sheep industry would require some consideration, due to the apparently different mode of action of the two main effects of TM-QTL (on growth and muscling).  相似文献   

12.
Under current Australian industry pre-slaughter guidelines, lambs may be off feed for up to 48 h before slaughter. The purpose of this study was to examine what proportion of circulating metabolites at slaughter are due to stress and feed deprivation and if this response differs between Merino and Terminal genotypes. In addition the effect of feed deprivation on carcass weight and meat quality was examined. Jugular blood samples were collected from 88 Merino and Terminal sired lambs at rest and at slaughter following 24, 36 and 48 h of feed deprivation and plasma analysed for glucose, lactate, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHOB). From the same carcasses hot carcass weight (HCWT) were measured as well as a suite of meat quality traits measured such as M. longissimus lumborum (loin) and M. semitendinosus pH at 24 h postmortem. Loin samples were also analysed for intramuscular fat content and Warner–Bratzer Shear Force. Merino sired lambs had a higher NEFA response compared to Terminal sired lambs at slaughter after 24, 36 and 48 h of feed deprivation, with NEFA levels up to 35% higher than previously reported in the same animals at rest in animal house conditions, whereas BHOB response to feed deprivation was not affected by sire type (P>0.05) and similar to previously reported at rest. In addition to the metabolic effects, increasing feed deprivation from 36 h was associated with a 3% reduction in HCWT and dressing percentage as well as causing increased ultimate pH in the M. semitendinosus in Merino sired lambs. Findings from this study demonstrate that Merino and Terminal sired lambs differ in their metabolic response to feed deprivation under commercial slaughter conditions. In addition, commercial feed deprivation appears to have a negative effect on ultimate pH and carcass weight and warrants further investigation.  相似文献   

13.
Plasma samples were collected at intervals of about 2 weeks from about ten 2 1/2 year old, or older, and five 1 1/2 year old ewes of each of the Scottish Blackface, Finnish Landrace and Tasmanian Merino ewes and were assayed for their non-esterified fatty acid (NEFA) concentrations. The NEFA concentrations showed an increase with time for every animal. The NEFA concentrations and their linear increase was least in the Finnish Landrace animals. The increase with time was greatest in the Merinos. There was no difference between the age groups. There was no evidence of any annual, cyclical trend.  相似文献   

14.
Myostatin, which is also known as growth and differentiation factor 8 (GDF8), acts as a negative regulator of skeletal muscle growth. Variation in the myostatin gene (MSTN) has been associated with variation in muscularity in many animals including sheep. Polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis was used to investigate MSTN in a diverse range of sheep breeds including the New Zealand (NZ) Romney, Coopworth, Corriedale, Dorper, Perendale, Suffolk, Merino, Dorset Down, Poll Dorset, Texel and other NZ cross-bred sheep. A total of 28 nucleotide substitutions were identified from nucleotide c.-1199 in the promoter region to c.*1813 (based on NCBI GenBank accession number DQ530260) and including the well-described substitution c.*1232G>A (MSTN g+6223G>A). Of these 28 substitutions, 3 were located in the promoter region, 3 in the 5′UTR, 11 in intron 1, 5 in intron 2 and 5 in the 3′UTR. One substitution in exon 1 (c.101G>A) potentially results in an amino acid substitution of glutamic acid (Glu) with glycine (Gly) at codon 34. Ten of these substitutions have not been reported previously. The genetic variation revealed in this study suggests this gene is more variable than hitherto reported and provides a foundation for future research into how this variation affects muscle and growth traits.  相似文献   

15.
Wool growth in Merino sheep demands a high level of sulphur amino acids, competing with body growth and the immune system, which may play a role in increasing the risk of lamb mortality. The hypothesis that dietary supplementation of methionine (Met) to Merino ewes during the late stages of pregnancy will improve foetal growth and alter immune competency of ewes and lambs was tested in a total of 120 grazing, pregnant Merino ewes. Sixty ewes were group-supplemented with 6.3 g/d rumen-protected Met (Met-Plus) per sheep from day 111 of pregnancy until day 7 after lambing, and the other 60 animals were used as a non-supplemented Control. Lambs from Met-supplemented ewes tended to be 10% heavier than Control lambs (p = 0.10), which did not affected the survival rate at weaning significantly. The supplemented ewes had slightly higher concentrations of total glutathione (GSH) in plasma at lambing (p < 0.06), but there were no differences between 1 and 3 months post-lambing in GSH, glutathione disulphide (GSSG) and the GSSG:GSH ratio. The GSSG:GSH ratio in the blood of ewes was elevated at lambing (p < 0.05), hinting that ewes were undergoing increased oxidative stress. The Met supplementation elevated the total IgG concentration (p < 0.05) in lambs aged 4 and 6 weeks, but did not change the IgG concentrations in colostrum and in plasma of 1-week-old lambs, and white blood cell counts and leukocyte types. The trend towards higher lamb birth weights in the Met-supplemented group requires further investigation as this may influence survival at birth and weaning.  相似文献   

16.
The aim of this study was to fine map the genomic location of the Horns locus in the Australian Merino sheep population and to identify markers that can be used to predict the horn phenotype. A linkage disequilibrium analysis of horn data from Australian Merino sheep mapped the Horns locus to a small region on chromosome 10. A single nucleotide polymorphism in the region was found to be highly predictive for the polled phenotype in an experimental population of Merino sheep. This was owing to a dominance effect of one of the alleles when inherited maternally. It was suggested that a genetic test would provide a good predictor of the polled phenotype. Finally, an evaluation of industry data showed that the SNP is at very different frequencies in Poll Merino sheep that have been bred for polledness (based on phenotype alone) compared with the Merino sheep breed.  相似文献   

17.
Active immunization of Merino and crossbred ewe lambs early in life with a partly purified inhibin derived from bovine follicular fluid (bFF) advanced their puberty. This occurred whether the lambs were immunized from 3 weeks of age or from 9 weeks of age or just 3 times between 3 and 9 weeks. However, the effect was more obvious with multiple injections starting at 3 weeks of age. The ovulation rate of the immunized lambs was significantly higher than that of the control ewes. When lambs were subjected to multiple immunizations the increased ovulation rate persisted in Merinos for at least 1 year after immunization ceased. The lambs injected 3 times only (at 3, 6 and 9 weeks of age) did not show any increase in ovulation rate. Plasma concentrations of FSH and LH measured in blood samples taken 1 week after immunization were not significantly different between the treatment groups. Daily sperm output in the urine and testis diameter were measured in ram lambs from the same breeds and flocks as the ewe lambs. Immunization with the inhibin preparation from 3 weeks of age resulted in a significant increase in daily sperm output (4255 +/- 701 vs 2344 +/- 344 x 10(6), P less than 0.01) and testis diameter (5.21 +/- 0.3 vs 4.33 +/- 0.2 cm, P less than 0.05) in Merino rams examined in the non-breeding season when the rams were aged 23 months. Although the same trend was seen in the following year the differences were not significant. Immunization from 9 weeks of age had no effect. A similar increase in daily sperm output was seen (at 20 and 25 months of age) in crossbred rams immunized from 3 weeks of age but the difference was not significant. Plasma concentrations of FSH (but not LH) in samples from rams immunized from 3 weeks of age were significantly higher than those of control rams at 7 and 60 weeks of age in Merino rams and at 23 and 31 weeks of age in crossbred rams. Plasma FSH concentrations at 21 and 26 weeks of age in the Merino rams immunized from 3 weeks of age were higher than those of control lambs, and these increases preceded a significant (P less than 0.05) increase in testicular diameter at 30 weeks of age (4.99 +/- 0.2 vs 4.37 +/- 0.2 cm). These results suggest that active immunization early in life with an inhibin-enriched fraction from bFF advances puberty in ewe lambs.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   

18.
Daily methane production and feed intake were measured on 160 adult ewes, which were the progeny of 20 sires and 3 sire types (Merino, dual-purpose and terminal) from a genetically diverse flock. All animals were housed in individual pens and fed a 50/50 mix of chaffed lucerne and oaten hays at 20 g/kg liveweight (LW), with feed refusals measured for at least 10 days before the first of three 22-h measurements in respiration chambers (RC). Feed was withdrawn at 1600 h on the day before each RC test to encourage the ewes to eat the entire ration provided for them in the RC. After the first 1-day RC test, the sheep were returned to their pens for a day, then given a second 1-day RC test, followed by another day in their pens, then a third RC test. After all animals had been tested, they were ranked according to methane emissions adjusted for feed intake in the RC and on the previous day, enabling 10 low and 10 high methane animals to be chosen for repeat measurement. No variation between sires nor consistent effects of LW on feed eaten (%FE, expressed as per cent of feed offered) was evident in the 10 days before the first RC measurement. However, significant differences between sires (equivalent to an estimated heritability of 41%) were identified for %FE during the 2nd and 3rd days of RC testing (2 and 4 days after the initial RC test). The analysis of all data showed that methane emissions in the RC were related to feed intake on the day of testing and the two previous days (all P<0.0005). Before correcting for feed intake on previous days, there was some variation between sires in methane yield, equivalent to an estimated heritability of 9%. Correction for feed intake on the 2 previous days halved the residual variation, allowing other effects to be detected, including effects of LW, twins reared as singles, test batch, RC and test-day effects, but estimated sire variation fell to zero. In order to avoid potential biases, statistical models of methane emissions in the RC need to consider potential confounding factors, such as those identified as significant in this study.  相似文献   

19.
Effect of cortisol on hepatic gluconeogenesis in the fetal sheep   总被引:1,自引:0,他引:1  
To determine whether the prenatal surge in cortisol induces the onset of gluconeogenesis in the fetal sheep, we performed studies in eight fetal sheep of 124 +/- 3 days gestational age. Catheters were inserted chronically in the descending aorta, inferior vena cava, and hepatic and umbilical veins, allowing the measurement of substrate flux across the liver and placenta. Cortisol was infused over a 48-h period, raising plasma cortisol concentrations from 3.5 +/- 2.5 ng/ml to 78 +/- 22 ng/ml at 24 h and 111 41 ng/ml at 48 h. At 24 and 48 h, [14C]lactate was infused into the inferior vena cava, and blood samples were obtained to measure plasma concentrations and specific activities of glucose and lactate. Comparison of the cortisol-treated group with an untreated control group of animals revealed no differences in blood gases, haemoglobin concentrations, or glucose and lactate levels. Similarly, there were no differences between groups in liver oxygen consumption, glucose and lactate flux, or gluconeogenesis from lactate. In two animals we demonstrated hepatic glucose production from lactate. One of these was in active labor at the time of study, and one aborted within hours of the study. We conclude that the prenatal cortisol surge alone is not responsible for the onset of hepatic gluconeogenesis in the perinatal period. However, cortisol may have a permissive action, promoting hepatic gluconeogenesis in response to other hormonal stimuli.  相似文献   

20.
The distribution of the R-r-i blood group system was studied in eight breeds of Australian sheep. The recessive i gene was found to be absent from Merinos and, consequently, the i phenotype was absent in Merino crosses. Distribution of the groups in Dorset Horns and Ryelands was found to be strikingly different from that of other breeds. Two animals were found to have anti-r antibodies in serum.  相似文献   

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