The effect of individual liveweight and use of teaser rams prior to mating on the reproductive performance of ewe hoggets

AIM: To determine the effects of liveweight (LW) and use of teaser rams prior to mating on both the mating performance and pregnancy rate of ewe hoggets.

METHODS: Romney hoggets (n=841) were weighed and randomly assigned to one of two treatment groups; either exposed to seven harnessed, vasectomised (teaser) rams for 17 days prior to the breeding period (n=283); or not exposed to teaser rams (unteased, n=558). Harnessed Perendale rams were then introduced for two oestrous cycles. Using crayon marks, hoggets were identified as having been mated during the first 17 days only, during the second 17 days only, during both periods, or not mated. All mated hoggets were then scanned for pregnancy using ultrasound, 48 days after the end of the breeding period, and identified as being either non-pregnant, or as single-, twinor triplet-bearing.

RESULTS: Hoggets mated in either the first 17 days only or in both the first and second 17-day periods were heavier than those mated in the second period only (p<0.001). Those mated in the first or second 17-day period only, and those mated in both periods were all heavier prior to mating than those not mated at all (p<0.001). Twin-bearing hoggets were heavier than both their single-bearing and non-pregnant counterparts (p<0.001). A greater proportion of the teased hoggets were mated in the first 17 days only compared with unteased hoggets (62.6 vs 32.1%; p<0.001). In contrast, more of the unteased hoggets were marked in the second 17-day period only (p<0.001). A greater proportion of mated, unteased hoggets were found to be non-pregnant in comparison to their teased counterparts (17.8 vs 11.2%; p=0.02).

CONCLUSIONS: Heavier hoggets at breeding were more likely to be mated in the first 17 days of the breeding period and more likely to be twin-bearing. Use of teaser rams for 17 days prior to the breeding period increased the proportion of hoggets mated in the first 17 days, increased conception rates, and thus increased the proportion of pregnant hoggets. These results indicate that farmers should utilise teasers for 17 days prior to commencement of the breeding period and avoid mating hoggets that weigh below 36 kg.     

The effect of individual liveweight and use of teaser rams prior to mating on the reproductive performance of ewe hoggets

AIM: To determine the effects of liveweight (LW) and use of teaser rams prior to mating on both the mating performance and pregnancy rate of ewe hoggets. METHODS: Romney hoggets (n=841) were weighed and randomly assigned to one of two treatment groups; either exposed to seven harnessed, vasectomised (teaser) rams for 17 days prior to the breeding period (n=283); or not exposed to teaser rams (unteased, n=558). Harnessed Perendale rams were then introduced for two oestrous cycles. Using crayon marks, hoggets were identified as having been mated during the first 17 days only, during the second 17 days only, during both periods, or not mated. All mated hoggets were then scanned for pregnancy using ultrasound, 48 days after the end of the breeding period, and identified as being either non-pregnant, or as single-, twin or triplet-bearing. RESULTS: Hoggets mated in either the first 17 days only or in both the first and second 17-day periods were heavier than those mated in the second period only (p<0.001). Those mated in the first or second 17-day period only, and those mated in both periods were all heavier prior to mating than those not mated at all (p<0.001). Twin-bearing hoggets were heavier than both their single-bearing and non-pregnant counterparts (p<0.001). A greater proportion of the teased hoggets were mated in the first 17 days only compared with unteased hoggets (62.6 vs 32.1%; p<0.001). In contrast, more of the unteased hoggets were marked in the second 17-day period only (p<0.001). A greater proportion of mated, unteased hoggets were found to be non-pregnant in comparison to their teased counterparts (17.8 vs 11.2%; p=0.02). CONCLUSIONS: Heavier hoggets at breeding were more likely to be mated in the first 17 days of the breeding period and more likely to be twin-bearing. Use of teaser rams for 17 days prior to the breeding period increased the proportion of hoggets mated in the first 17 days, increased conception rates, and thus increased the proportion of pregnant hoggets. These results indicate that farmers should utilise teasers for 17 days prior to commencement of the breeding period and avoid mating hoggets that weigh below 36 kg.     

Effect of the ratio of teaser rams used prior to breeding on the reproductive performance of ewe hoggets

AIM: To determine the effects of the ratio of vasectomised (teaser) rams to ewe hoggets used prior to breeding on the breeding performance and pregnancy rate of ewe hoggets. METHODS: Romney-composite ewe hoggets (n=1,180), 7-8 months of age, were randomly assigned to one of five treatment groups (Day 1) and either exposed to harnessed teaser rams at a teaser-ram:ewe-hogget ratio of 1:32 (n=193 hoggets), 1:66 (n=199), 1:98 (n=197), or 1:197 (n=395), for 17 days prior to the breeding period, or not exposed to teasers (unteased; n=196). Harnessed entire rams were then introduced for the duration of two oestrous cycles (34 days). Using crayon marks, ewe hoggets were identified as having been mated during the first 17 days only, during the second 17 days only, during both 17-day periods, or not mated. Hoggets were weighed on Days 1 and 18. All ewe hoggets were scanned for pregnancy using ultrasound, 57 days after the end of the breeding period. RESULTS: Hogget groups did not differ in liveweight at Day 1, but at Day 18 hoggets exposed to teasers at a ratio of 1:66 were lighter, and those exposed to teasers at a ratio of 1:32 were heavier than all other groups by up 3.0 kg (p<0.05). Unteased ewe hoggets were less likely to be pregnant to the first 17 days of breeding compared with all teased groups, by at least 16.4% (p<0.05). Over the entire 34-day breeding period, however, only those teased at a ratio of 1:32 were more likely to be pregnant, by 11.9%, than unteased hoggets (p<0.05). Within the teased hogget groups, there were no differences between groups for either the percentage mated in the first 17 days of breeding only, or those pregnant to either the first 17 days of breeding only or the entire breeding period. CONCLUSIONS: The results of this study indicate that teaser-ram:ewe-hogget ratios as high as 1:197 can increase the percentage of ewe hoggets bred in the first 17 days of mating by at least 16.4%. Across the range of ratios used there was little difference in breeding pattern or pregnancy rate, although results might suggest ratios 1:98.     

The effect of the maturity and prior breeding activity of rams and body condition score of ewe hoggets on the reproductive performance of ewe hoggets

Abstract

AIM: To determine the effect of age and prior use of mature rams at a given ram-to-ewe ratio, and the effect of body condition on breeding performance and pregnancy rate of ewe hoggets.

METHODS: Ewe hoggets (n=733) aged 7–8 months were weighed and their body condition scored, then randomly assigned to one of three treatment groups (Day 0) and joined with either four two-tooth rams (20 months of age) not used previously (n=244; Two-tooth), four mixed-aged mature rams that had not been used earlier in the season (n=244; Mature-fresh), or four mixed-aged mature rams that had been used with mature ewes immediately prior to joining with hoggets (n=245; Mature-used). The breeding period was 34 days. Ewe hoggets were identified as having been marked during the first 17 days only, during both 17-day periods, during the second 17 days only, or not marked. Hoggets were re-weighed on Day 34, and pregnancy status determined using ultrasound on Day 92. The breeding soundness of the rams was assessed on Days ?34 and ?1.

RESULTS: Semen samples obtained from the rams did not differ significantly in any of the parameters measured (p>0.05). Ewe hoggets joined with Mature-fresh rams were less likely (p<0.05) to be marked in the second 17 days of breeding only than those joined with either Two-tooth or Mature-used rams. No other breeding parameters were affected by breeding group (p>0.05). Hoggets marked in the first 17 days only were heavier (p<0.05) at Day 0 than those marked in the second 17 days only or not marked. Hoggets diagnosed as twin-bearing were heavier (p<0.05) than non-pregnant or single-bearing hoggets. Those hoggets marked in the first 17 days only had a greater (p<0.05) body condition score (BCS) than those marked in the second 17 days only or not marked at all. These differences were no longer apparent after correction for liveweight (LW).Correction for LW at Day 0 or change in LW during the breeding period did not affect the results for breeding performance.

CONCLUSIONS: Under the conditions of this study, two-tooth rams and mature rams that had been used previously were just as suitable as mature rams that had not been used previously for breeding with ewe hoggets. Further studies are warranted to verify this result. The re-use of rams without reducing breeding performance would reduce breeding costs and may make breeding hoggets a more viable option for farmers. The BCS of ewe hoggets affected breeding performance, and can thus be used to identify those animals most suitable for breeding.     

Effect of the age of rams on reproductive performance of ewe hoggets

AIM: To determine the effect of the age of rams, used at a standardised ram-to-ewe ratio, on the breeding performance and pregnancy rate of ewe hoggets. METHODS: Ewe hoggets ((1/2) Romney x (1/4) Texel x (1/4) Finnish Landrace; n=582) aged 7-8 months were exposed to nine two-tooth, harnessed, vasectomised teaser rams for a period of 17 days (Days 1-17). The ewe hoggets were then weighed and randomly assigned to one of three treatment groups (on Day 18) and joined with either four ram hoggets not used previously (n=194), four two-tooth rams not used previously (n=196), or four mixed-age mature rams (n=192) that had been used previously to mate mature ewes immediately before breeding with the ewe hoggets. The breeding period was 34 days. Ewe hoggets were identified as having been mated during the first 17 days only, during both 17-day periods, during the second 17 days only, or not mated. All ewe hoggets were scanned for pregnancy using ultrasound, 54 days after the end of the breeding period. RESULTS: Liveweights of ewe hoggets did not differ between treatment groups. More ewe hoggets were mated by the mature rams in the first 17 days than by either ram hoggets or two-tooth rams (p<0.05). However, more of the ewe hoggets mated by mature rams returned to service (failed to conceive), and the percentage of ewe hoggets bred in the first 17 days only or pregnant from a service in the first 17 days did not differ significantly between groups. Fewer of the ewe hoggets joined with ram hoggets were diagnosed as pregnant after 34 days of breeding compared with those joined with either two-tooth or mature rams (p<0.05), as more ewe hoggets failed to be mated at all by ram hoggets compared with those joined with mature rams (p<0.05). There was also a tendency for more ewe hoggets joined with ram hoggets not to be mated at all compared with those joined with two-tooth rams (p=0.07). CONCLUSIONS: Two-tooth rams previously unused and mature rams previously used for mating were a better option than unused ram hoggets to maximise the pregnancy rate of ewe hoggets to a 34-day breeding period. However, further work is required as it was unclear why lower conception rates were observed in ewe hoggets joined with mature rams which had been used previously. As a result, the advantage of using mature rams may have been underestimated.     

The effect of individual liveweight and condition scores of ewes at mating on reproductive and scanning performance

AIMS: To determine the effects of liveweight (LW) and condition score (CS) of ewes at mating on both mating performance and scanning percentage, and to determine if effects of CS were independent of LW. METHODS: Two groups of ewes, comprising 1,780 mixed-aged Romney (Rom MA) and 692 composite two-tooth (1/8 East Friesian 1/16 Finn 13/16 Romney, Comp TT) ewes were grazed separately with harnessed rams for two reproductive cycles. Romney rams were used for the first 17 days of mating and then replaced on the morning of Day 18 by Suffolk rams. Ewes were weighed and CS assessed on a scale of 0-5 before the introduction of the rams. Ewes were identified as having been mated during the first cycle only, during both cycles, during the second cycle only, or not mated. All mated ewes were scanned using ultrasound, 50 days after the end of mating, and identified as being either non pregnant, single-, twin- or triplet-bearing. RESULTS: Linear relationships (R2=0.99) between mean LW and CS at mating were evident for both Rom MA and Comp TT ewes and the mean increase in LW per unit increase in CS was greater in the Rom MA ewes (7.88 kg) than the Comp TT (4.78 kg) ewes (p<0.05). Ewes mated in the second cycle only were significantly (p<0.05) lighter than those mated in the first cycle only. In Rom MA ewes, a greater proportion were mated in the first cycle only if CS was >/=2.0 than if CS was <2.0, and the proportions of ewes mated in the first cycle only or in both cycles did not differ if CS was >/=2.5. In Comp TT ewes, there was no difference in the proportions mated in the first cycle or both cycles, if CS was >/=2.0. Triplet-bearing ewes were heavier than twin-bearing ewes, which were in turn heavier than both singleton-bearing and non pregnant ewes. Twin-bearing ewes had higher CS than both single-bearing and non pregnant ewes (p<0.05) but differences were not significant if LW was included as a covariate. In both Rom MA and Comp TT ewes, greater proportions were non pregnant and lower proportions had twins if CS was <2.0 than if CS was >/=2.0. In Rom MA ewes only, a greater proportion again had twins and a lower proportion had singletons if CS was >/=3.0 than if CS was <3.0. In Comp TT ewes, the proportion that were non pregnant or twin-bearing did not vary with CS if CS was >/=2.0. Reproductive performance was maximal for Rom MA and Comp TT ewes that had CS at mating >/=3.0 and >/=2.0, respectively, equating to LW of 62.6 and 48.5 kg, respectively. CONCLUSIONS: In both groups of ewes, CS and LW at mating positively affected reproductive performance measured at the time of mating and at scanning, however, no reproductive advantage was evident above a minimum CS of 3.0 and 2.0, equating to LW of 62.6 and 48.5 kg, for Rom MA and Comp TT ewes, respectively. Sheep farmers should direct management to ensure that no ewes are below these minimum targets rather than ensuring high average LW and/or CS of a mob.     

The effect of individual liveweight and condition scores of ewes at mating on reproductive and scanning performance

Abstract

AIMS: To determine the effects of liveweight (LW) and condition score (CS) of ewes at mating on both mating performance and scanning percentage, and to determine if effects of CS were independent of LW.

METHODS: Two groups of ewes, comprising 1,780 mixedaged Romney (Rom MA) and 692 composite two-tooth (? East Friesian 1/16 Finn 13/16 Romney, Comp TT) ewes were grazed separately with harnessed rams for two reproductive cycles. Romney rams were used for the first 17 days of mating and then replaced on the morning of Day 18 by Suffolk rams. Ewes were weighed and CS assessed on a scale of 0–5 before the introduction of the rams. Ewes were identified as having been mated during the first cycle only, during both cycles, during the second cycle only, or not mated. All mated ewes were scanned using ultrasound, 50 days after the end of mating, and identified as being either non pregnant, single-, twin- or triplet-bearing.

RESULTS: Linear relationships (R²=0.99) between mean LW and CS at mating were evident for both Rom MA and Comp TT ewes and the mean increase in LW per unit increase in CS was greater in the Rom MA ewes (7.88 kg) than the Comp TT (4.78 kg) ewes (p<0.05). Ewes mated in the second cycle only were significantly (p<0.05) lighter than those mated in the first cycle only. In Rom MA ewes, a greater proportion were mated in the first cycle only if CS was .2.0 than if CS was <2.0, and the proportions of ewes mated in the first cycle only or in both cycles did not differ if CS was ≥2.5. In Comp TT ewes, there was no difference in the proportions mated in the first cycle or both cycles, if CS was ≥2.0. Triplet-bearing ewes were heavier than twin-bearing ewes, which were in turn heavier than both singleton-bearing and non pregnant ewes. Twin-bearing ewes had higher CS than both single-bearing and non pregnant ewes (p<0.05) but differences were not significant if LW was included as a covariate. In both Rom MA and Comp TT ewes, greater proportions were non pregnant and lower proportions had twins if CS was <2.0 than if CS was ≥2.0. In Rom MA ewes only, a greater proportion again had twins and a lower proportion had singletons if CS was ≥3.0 than if CS was <3.0. In Comp TT ewes, the proportion that were non pregnant or twin-bearing did not vary with CS if CS was ≥2.0. Reproductive performance was maximal for Rom MA and Comp TT ewes that had CS at mating ≥3.0 and ≥2.0, respectively, equating to LW of 62.6 and 48.5 kg, respectively.

CONCLUSIONS: In both groups of ewes, CS and LW at mating positively affected reproductive performance measured at the time of mating and at scanning, however, no reproductive advantage was evident above a minimum CS of 3.0 and 2.0, equating to LW of 62.6 and 48.5 kg, for Rom MA and Comp TT ewes, respectively. Sheep farmers should direct management to ensure that no ewes are below these minimum targets rather than ensuring high average LW and/or CS of a mob.     

The effect of mating age on the reproductive performance,food utilisation and liveweight change of the female pig

Sixty-four crossbred gilts were used to study the effect of mating at the first oestrus period following puberty. Puberty was induced at different ages by the introduction of the gilts to boars at either 160 or 200 days of age. Mating was delayed until second oestrus, when the mean age of the two groups was 197.8 and 237.2 days respectively. The difference of 39.4 ± 5.14 days was significant (P < 0.001). There were no significant differences in the number of weight of pigs born or reared in any of the first five parities. Thirty four sows (seventeen from each treatment) completed five parities. The gilts mated at 237 days of age consumed 159 ± 38 kg (P < 0.01) more food between 160 days of age and weaning their fifth litters. The gilts mated at the younger age consumed 6.2% less food per unit of weaner liveweight over the five litters. Initial differences in liveweight between the two groups had disappeared by the middle of the second pregnancy.     

The effect of individual liveweight and condition of beef cows on their reproductive performance and birth and weaning weights of calves

AIM: To examine of the influence of liveweight (LW), condition (CS) and age of dam on inter-calving interval (ICI), date of calving, days from joining to calving, and birth and weaning weights of calves. METHODS: LW and CS were measured in a herd of mixed-aged (3-8 years) Hereford x Friesian beef cows on four occasions, annually, over a 3-year period from joining (the date bulls were introduced into the herd at the start of a restricted breeding season) in November 2000 to weaning in March 2004. The four dates of weighing and condition-scoring were joining (November), weaning (March), winter (June), and pre-calving (August). Calves were tagged, identified to their dam, and weighed within 24 h of birth, and at weaning. Date of calving, ICI and days from joining to calving were determined. RESULTS: The CS and LW of cows varied between years. LW increased in cows up to 6 years of age. Three-year-old cows had a longer ICI than older cows. Change in CS and LW from winter to pre-calving and pre-calving to joining were negatively correlated with ICI for younger cows but not for cows > or = 5 years (CS) and 6-8 years (LW) old. No difference in CS or LW precalving was evident between cows that subsequently became pregnant compared with non-pregnant cows, although cows that became pregnant gained more condition from pre-calving to joining than non-pregnant cows. Pregnant cows were heavier and had higher CS at joining than non-pregnant cows. CONCLUSIONS: Young cows, up to second-mating as 3-year-olds, would benefit from separate nutritional management from older cows, to ensure ICI and days to conception are kept at targeted levels. In addition, increasing CS from pre-calving to joining and higher LW and CS at joining resulted in higher pregnancy rates.     

The reproductive performance of anoestrous dairy cows following treatment with progesterone and oestradiol prior to the start of mating

Aims: To determine the reproductive performance of cows diagnosed as anoestrus prior to the planned start of mating (PSM) when they were either treated when first diagnosed, or left untreated until 16 days after the PSM.

Methods: A clinical trial was conducted during the 1996/97 and 1997/98 breeding seasons involving 823 anoestrous dairy cows in 14 herds. On Day-8 (PSM = Day 0), cows in one group (Treated) were each treated with an intravaginal device containing 1.9 g of progesterone (CIDR).The CIDR device was removed on Day-2, and on Day-1 each cow was injected intramuscularly with 1 mg oestradiol benzoate. Cows in the second group (Control) remained untreated at the time of first examination. All cows detected in oestrus after the PSM were mated by artificial insemination (AI) or a bull. Sixteen days after the PSM, all cows that had not been mated were presented for veterinary examination, and those which were still classified as anoestrus were treated with the previously described CIDR regimen. Pregnancy status and approximate date of conception were determined by palpation per rectum 10-13 weeks after the PSM or 6 weeks after the end of the mating period.

Results: Treatment of anoestrous cows 8 days before the PSM significantly increased the number of cows detected in oestrus (95.0% vs 63.1%;p < 0.001) and conceiving (59.5% vs 38.8%;p < 0.001) during the first 21 days of mating, and reduced the interval from PSM to conception by 7.5 days (p < 0.001). There was no significant difference between the conception rate of cows mated following the CIDR treatment regimen compared to cows mated at their first spontaneous oestrus after calving (52.4% vs 58.3%; p = 0.143).

Conclusion: Diagnosis and treatment of anoestrous dairy cows prior to the start of mating significantly improves their reproductive performance under the seasonal mating conditions typical of spring-calving New Zealand dairy herds.     

The reproductive performance of anoestrous dairy cows following treatment with progesterone and oestradiol prior to the start of mating

AIMS: To determine the reproductive performance of cows diagnosed as anoestrus prior to the planned start of mating (PSM) when they were either treated when first diagnosed, or left untreated until 16 days after the PSM. METHODS: A clinical trial was conducted during the 1996/97 and 1997/98 breeding seasons involving 823 anoestrous dairy cows in 14 herds. On Day -8 (PSM = Day 0), cows in one group (Treated) were each treated with an intravaginal device containing 1.9 g of progesterone (CIDR). The CIDR device was removed on Day -2, and on Day -1 each cow was injected intramuscularly with 1 mg oestradiol benzoate. Cows in the second group (Control) remained untreated at the time of first examination. All cows detected in oestrus after the PSM were mated by artificial insemination (AI) or a bull. Sixteen days after the PSM, all cows that had not been mated were presented for veterinary examination, and those which were still classified as anoestrus were treated with the previously described CIDR regimen. Pregnancy status and approximate date of conception were determined by palpation per rectum 10 -13 weeks after the PSM or 6 weeks after the end of the mating period. RESULTS: Treatment of anoestrous cows 8 days before the PSM significantly increased the number of cows detected in oestrus (95.0% vs 63.1%; p<0.001) and conceiving (59.5% vs 38.8%; p<0.001) during the first 21 days of mating, and reduced the interval from PSM to conception by 7.5 days (p<0.001). There was no significant difference between the conception rate of cows mated following the CIDR treatment regimen compared to cows mated at their first spontaneous oestrus after calving (52.4% vs 58.3%; p = 0.143). CONCLUSION: Diagnosis and treatment of anoestrous dairy cows prior to the start of mating significantly improves their reproductive performance under the seasonal mating conditions typical of spring-calving New Zealand dairy herds.     

The effect of breeding ewe lambs on subsequent two-year-old ewe performance

This study was undertaken to determine if breeding ewe lambs (hoggets) would influence subsequent two-year-old (two-tooth) ewe liveweight and reproductive performance and their lamb's performance to weaning. Two-tooth Romney ewes that had been bred and lambed as a hogget (n = 505) were compared with those of 196 ewes that were bred as a hogget but did not lamb and 235 ewes that were not presented for breeding as a hogget. Hogget lambing resulted in reduced (P < 0.05) two-tooth liveweight and body condition score at breeding although still present this liveweight difference was reduced by two-tooth lamb weaning. Two-tooth ewes that had previously lambed as a hogget had greater (P < 0.05) returns to service rates and lower (P < 0.05) fecundity (multiple-bearing/two-tooth bred) than those that were bred for the first time. Two-tooth lamb liveweights were unaffected by hogget lambing. These results show that hogget lambing had a small negative effect on subsequent two-tooth reproductive performance. This was most likely caused by reduced liveweight at two-tooth breeding and indicates that farmers need to ensure management practices are in place to reduce the impact of hogget lambing on two-tooth liveweight.     

The effects of melatonin and light treatment on the reproductive performance of yearling Suffolk rams

The effects of melatonin and light treatments on the reproductive performance of yearling Suffolk rams was investigated. One group (group A, n = 5) remained in the local light environment (lat. 51 degrees 43'N). The other two groups (group B, n = 5; group C, n = 5) were given a priming period of long days [18 h light (L):6 h dark (D)] during 26 January-9 March. During 9 March-16 October, group B was exposed to short days (9L:15D) and group C was given melatonin implants (Regulin) at 5-weekly intervals. Testis diameter, sexual behaviour and semen quality were used to assess reproductive performance. The responses of groups B and C were similar and peak reproductive performance occurred in these groups significantly earlier than in group A. Peak performance was not maintained in groups B and C throughout the short day and melatonin treatment periods and this has been attributed to refractoriness. The response of group C clearly indicates that melatonin treatment may be considered as an alternative to photostimulation for the preparation of rams for out-of-season breeding.     

Reproductive performance of Suffolk and Suffolk-cross ewes and ewe lambs exposed to vasectomized rams before breeding

Multiparous Suffolk and Suffolk-cross ewes were randomly allotted to treatments within breed and year to measure effects of ram exposure, during transition from anestrus to breeding activity, on reproductive performance. Treatments were: 1) ewes joined with two mature vasectomized Rambouillet rams for 15 d before breeding (DC), 2) ewes maintained across a net wire fence from two vasectomized rams for 15 d before breeding (FC) and 3) ewes maintained approximately 400 m away from rams (NC). At the end of the 15 d, all ewes were placed in one pasture and mated to three fertile Suffolk rams during a 34-d breeding season. A total of 96 Suffolk and 177 Suffolk-cross ewes was utilized during the 3-yr experiment. A greater (P less than .05) prebreeding ovulation percentage was observed in DC and FC than in NC ewes. Mating and lambing occurred approximately 6 d earlier for DC or FC ewes than for NC ewes. A similarly designed experiment was conducted using Suffolk and Suffolk-cross ewe lambs allotted to treatments within breed and year to measure effects of ram exposure during the natural breeding season, but prior to breeding. Treatment differences were not detected (P greater than .05) for date of first observed estrus, date of lambing, percentage of ewes lambing in the first 17 d of the lambing season, number of lambs born per ewe lamb exposed or number of lambs born per ewe lamb giving birth.     

Effect of cobalt deficiency in the pregnant ewe on reproductive performance and lamb viability

Reproductive performance and lamb viability in cobalt sufficient and subclinically deficient ewes, and from ewes experiencing repletion from and depletion into cobalt deficiency, were investigated in two experiments. The sheep were fed a cobalt deficient ration and supplementation was by oral dose according to treatment. The treatments had a significant effect (P less than 0.001) on ewe serum vitamin B12 and methylmalonic acid concentrations. There were no significant effects on ewe liveweight, condition score or conception rate. Cobalt deficient ewes produced fewer lambs and had more stillbirths and neonatal mortalities than cobalt sufficient controls. Lambs from deficient ewes were slower to start suckling (P less than 0.05), had reduced concentrations of serum immunoglobulin G and zinc sulphate turbidity levels (P less than 0.05), and had lower serum vitamin B12 and higher methylmalonic acid concentrations (P less than 0.05), than lambs from cobalt sufficient dams. Cobalt supplementation in either the first or second half of pregnancy only did not fully alleviate these adverse effects.     

PCV2疫苗对仔猪体重和死亡率的影响

许多养猪生产者发现,在开始对仔猪接种猪圆环病毒2型(PCV2)疫苗后,猪场生产效益要好于PCV2感染之前。这是怎么回事呢?     

The effects of albendazole treatment on spring-rise in faecal nematode egg output and reproductive performance in the ewe

The effects of albendazole treatment in late autumn and winter on the spring-rise in faecal nematode egg output and reproductive performance in the ewe were investigated. The control measure effectively prevented the egg output in spring and lambs born to treated ewes had increased birthweights in comparison with those born to untreated ewes.     

胎次、配种季节对大约克母猪繁殖性能的影响

为研究胎次、配种季节对大约克母猪繁殖性能的影响,运用SPSS 16.0软件对753窝大约克纯种母猪的产仔数、出生窝重和断奶窝重等进行比较分析。结果表明：产总仔数第8胎最高（15.25头）,与第1胎差异显著（P＜0.05）,总的呈现随胎次增加而上升的趋势。大约克母猪春季和冬季配种产总仔数与秋季差异显著（P＜0.05）;冬季配种母猪的出生窝重、断奶均重、断奶窝重均高于其他三季。