(Co)variances for reproduction, egg weight and chick weight in ostriches

Cloete, S.W.P.; Bunter, KL; Brand, Z.; Lambrechts, H.

doi:10.4314/sajas.v34i6.3818

Cited by 11 publications

(13 citation statements)

References 8 publications

(2 reference statements)

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“…The highest mean egg weight 1444 ± 11 g for 4-year old hens occurred in November with the lowest 1294 ± 14 g for 2-year olds in July. These mean egg weights are in accordance with those of 1416 ± 128 g, 1419 ± 123 g and 1425 ± 107 g reported by Bunter et al (2001a), Cloete et al (2004) and Brand et al (2008), respectively. The mean chick weights followed similar trends to that of mean egg weights and thus will not be graphically presented.…”

Section: Resultssupporting

confidence: 92%

“…The high maximum of 17 eggs for EP and 16 chicks for CP were not the norm and were achieved only by seven and five hens, respectively. Coefficients of variation of MEW and MCW's were comparatively low (10 and 11%, respectively), and are consistent with values for average annual hen records in other studies (Bunter et al, 2001a;Cloete et al, 2004). Comparing MEW and MCW means showed an average weight loss of 39% at hatching.…”

Section: Resultssupporting

confidence: 89%

“…Egg production and CP had relatively high ranges of 0 -17 and 0 -16, resulting in the high coefficients of variation (CV) of respectively 93 and 128%. High CV's, albeit somewhat lower than those in the present study, are commonly reported for annual egg and chick production in ostrich females (Deeming, 1996;Van Schalkwyk et al, 1996;Bunter et al, 2001a;Cloete et al, 2004). A high frequency of zero records presumably contributed to excessive variation in monthly egg and chick production records.…”

Section: Resultscontrasting

confidence: 61%

“…Annual reproduction over an eight month breeding season was shown to be heritable (Bunter et al, 2001a;Cloete et al, 2004), while responses to selection for egg and chick production, based on the maternal phenotype, have also been reported 2008a). It is known that ostrich reproduction is affected by hen age Lambrechts, 2004), with 2-year old ostriches generally producing fewer eggs or chicks than their mature contemporaries.…”

Section: Introductionmentioning

confidence: 99%

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Parameter estimates for reproductive output and product quality traits of ostrich females within breeding seasons

Fair¹,

Wyk²,

Cloete³

2011

SA J. An. Sci.

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Data involving monthly records of egg production (EP), chick production (CP), hatchability (H), mean egg weight (MEW) and mean day-old chick weight (MCW) were analysed using REML procedures. All traits were treated as hen traits. Egg production of young birds increased to reach a peak of approximately 4 to 5 eggs per month relatively late in the breeding season (September to December). Older hens reached a higher peak of 6 to 9 eggs per month earlier in the breeding season (August to September). There was a secondary peak in older birds from November to December. All birds except 2-year olds exhibited evidence of a slump of production during October. Chick production, MEW, MCW and H followed similar trends. The random effects of direct additive genetic, permanent environment (PE), temporary environment (TEunique hen-year combinations) and service sire (SS) were estimated from the data. Heritability estimates of the direct additive genetic effect (h 2 a ) of the hen were 0.04 for EP, 0.05 for CP, 0.44 for MEW, 0.67 for MCW and 0.02 for H. The estimates of permanent environment (c 2 pe ) as a ratio of phenotypic variance for the four traits (MCW did not exhibit a significant c 2 pe effect) were 0.08, 0.08, 0.09 and 0.11, respectively. The effect of service sire as a ratio (c 2 ss ) was significant but relatively low for all traits, ranging from 0.04 for MEW and MCW to 0.06 for CP. Monthly EP and CP were highly correlated at all levels, ranging from 0.74 for the TE correlation to unity (1.00) for the genetic correlation. Egg production was favourably correlated with H at a genetic level (0.98). The genetic correlations of EP and CP with MEW and MCW were variable and in some cases antagonistic as is often found in poultry. The genetic correlations of H with MEW and MCW were positive (0.52 and 0.47, respectively). As expected, the genetic correlation of MEW and MCW was very high at 0.94. The results indicate that selection for improved reproduction (reproductive output and product quality traits) in ostriches is possible. Selection is unlikely to be complicated by unfavourable correlations with H, MEW and MCW. ________________________________________________________________________________

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 89%

Section: Resultscontrasting

confidence: 61%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Parameter estimates for reproductive output and product quality traits of ostrich females within breeding seasons

Fair¹,

Wyk²,

Cloete³

2011

SA J. An. Sci.

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“…The mean was slightly lower than previous weights reported by Cloete et al (2004), and Brand et al (2008a;b) for eggs collected from the same resource flock. This observation could probably be attributed to the small sample of eggs used in the present study.…”

Section: Resultscontrasting

confidence: 71%

Changes in the air cell volume of artificially incubated ostrich eggs

Brand¹,

Cloete²,

Malecki³

et al. 2013

SA J. An. Sci.

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________________________________________________________________________________ AbstractA total of 2160 images of candled, incubated ostrich eggs were digitized to determine the percentage of egg volume occupied by the air cell at different stages of incubation. The air cell on average occupied 2.5% of the volume of fresh eggs. For eggs that hatched successfully, this volume increased to an average of 24.4% at 41 days of incubation, just prior to hatching. Air cell volume at 29 days of incubation for infertile eggs (19.3%) was significantly higher when compared to dead-in-shell (DIS) eggs (14.3%) and eggs that hatched (13.8%). There was a significantly larger air cell volume in eggs that hatched normally compared with DIS eggs at 41 days of incubation (28.3% vs. 21.7%, respectively). No differences in air cell volume were observed up to day 17 of incubation for eggs that hatched normally between eggs that exhibited high, average or low rates of water loss, but from 20 days of incubation the air cell volume was significantly larger for high weight loss eggs. However, for the DIS eggs, air cell volume was consistently larger in eggs that exhibited high rates of water loss. Air cell volume was largely independent of adult strain (SA Black or Zimbabwean Blue) or whether chicks were assisted to hatch. Although some subtle differences in air cell size were detected between hatched and DIS chicks during this study, it is unlikely to find useful application in the broader industry.________________________________________________________________________________

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