Genetic aspects of puberty in Awassi ewes

Alkass, Jalal E.; Aziz, D.A.; Al-Nidawi, K.A.

doi:10.1016/0921-4488(94)90049-3

Cited by 10 publications

(2 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These observations extend those of Hawker and Kennedy (1978) and Alkass et al (1994) who showed that ewes that grew faster reached puberty at a younger age. In addition, our observations agree with those by Kenyon et al (2010) who observed that ewe lambs that attained heavier LW and higher condition score at mating were more likely to get pregnant and improve the fecundity rate.…”

Section: Discussionsupporting

confidence: 90%

Selection for superior growth advances the onset of puberty and increases reproductive performance in ewe lambs

Ariza-Nieto

Ferguson

Macleay

et al. 2013

Animal

View full text Add to dashboard Cite

The reproductive efficiency of the entire sheep flock could be improved if ewe lambs go through puberty early and produce their first lamb at 1 year of age. The onset of puberty is linked to the attainment of critical body mass, and therefore we tested whether it would be influenced by genetic selection for growth rate or for rate of accumulation of muscle or fat. We studied 136 Merino ewe lambs with phenotypic values for depth of eye muscle (EMD) and fat (FAT) and Australian Sheep Breeding Values at post-weaning age (200 days) for live weight (PWT), eye muscle depth (PEMD) and fat depth (PFAT). First oestrus was detected with testosterone-treated wethers and then entire rams as the ewes progressed from 6 to 10 months of age. Blood concentrations of leptin and IGF-I were measured to test whether they were related to production traits and reproductive performance (puberty, fertility and reproductive rate). In total, 97% of the lambs reached first oestrus at average weight 39.4 6 0.4 kg (mean 6 s.e.m.) and age 219 days (range 163 to 301). Age at first oestrus decreased with increases in values for PWT (P , 0.001), and concentrations of IGF-I (P , 0.05) and leptin (P , 0.01). The proportion of ewe lambs that achieved puberty was positively related with increases in values for EMD (P , 0.01), FAT (P , 0.05) or PWT (P , 0.01), and 75% of the ewe lambs were pregnant at average weight 44.7 6 0.5 kg and age 263 days (range 219 to 307). Ewe lambs that were heavier at the start of mating were more fertile (P , 0.001) and had a higher reproductive rate (P , 0.001). Fertility and reproductive rate were positively correlated with increases in values for EMD (P , 0.01), FAT (P , 0.05), PWT (P , 0.01) and leptin concentration (P , 0.01). Fertility, but not reproductive rate, increased as values for PFAT increased (P , 0.05). Leptin concentration increased with increases in values for EMD (P , 0.001), FAT (P , 0.001), PWT (P , 0.001), PEMD (P , 0.05) and PFAT (P , 0.05). Many of these relationships became non-significant when PWT or live weight was added to the statistical model. We conclude that selection for genetic potential for growth can accelerate the onset of puberty and increase fertility and reproductive rate of Merino ewe lambs. The metabolic hormones, IGF-I and leptin, might act as a physiological link between the growing tissues and the reproductive axis.Keywords: ewe lambs, phenotypic selection, ASBV, reproductive efficiency ImplicationsGenetic selection can improve the rates of growth and muscle development in sheep, and should also permit reproduction at a younger age because the onset of puberty depends on attainment of sufficient body mass. Our data support this hypothesis, suggesting that phenotypic and genetic selection for growth or muscling will improve the reproductive performance of Merino ewes mated to lamb at 1 year of age. These findings will inform bio-economic models and promote genetic selection strategies with a view to improving profitability of sheep production systems by achieving improvements i...

show abstract

Section: Discussionsupporting

confidence: 90%

Selection for superior growth advances the onset of puberty and increases reproductive performance in ewe lambs

Ariza-Nieto

Ferguson

Macleay

et al. 2013

Animal

View full text Add to dashboard Cite

show abstract

“…Heritability data for many ewe lamb reproductive traits are sparse, but knowledge is increasing. Overall, the available data suggest that the heritability of traits such as age and live weight at puberty [ 70 , 71 ], number of cycles in the first year [ 72 ], fertility, fecundity, and number of lambs born and weaned by ewe lambs are low to moderate at best [ 73 , 74 ], indicating that genetic gains can be made but will be slow. Newton [ 75 ] indicated that the fertility of ewe lambs was correlated with their later reproductive performance; however, they were genetically different traits.…”

Section: Factors Affecting Ewe Lamb Performance Prior To and During B...mentioning

confidence: 99%

Breeding Ewe Lambs: An Australasian Perspective

Kenyon

Corner-Thomas

2022

Animals

View full text Add to dashboard Cite

A number of potential advantages have been identified for breeding ewe lambs at 7 to 9 months of age, including increased lifetime productivity and profitability. However, breeding at this young age in extensive pastoral systems, such as in Australasia, can be associated with a number of disadvantages resulting in uptake of this management procedure being relatively low. This review highlights the known differences between ewe lamb and mature ewe reproductive performance, thus differing in their management. The review then summaries the scientific literature of factors that affect ewe lamb reproductive success, with a focus on recent studies conducted under extensive pasture-based conditions in Australasia. In particular, this review outlines the importance of ewe lamb live weight and body condition score on their productivity. The potential long-term consequences of breeding a ewe lamb at a young age in terms of her future success and that of her offspring to weaning are briefly outlined. In addition, the potential impacts of selecting progeny born to ewe lambs as future replacement ewes are discussed. Throughout this review, optimal management guidelines from prior to breeding the ewe lambs until rebreeding at 2 years of age are provided. Lastly, areas requiring future research are identified and discussed.

show abstract