Breeding ewe lambs successfully to improve lifetime performance

Kenyon, P. R.; Thompson, A. N.; St, Morris

doi:10.1016/j.smallrumres.2013.12.022

Cited by 75 publications

(106 citation statements)

References 103 publications

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“…The fair reproductive response of HE than ME ewes coincide with the reproductive differences that are observed between mature ewes and ewe lambs during their spontaneous breeding season (for review: see Kenyon et al, 2014). Moreover, considering body weight reached HE ewes approximately 6 months after the previous breeding season, it may be assumed that they did not reach puberty during the previous breeding season (Foster et al, 1985;Land, 1978), but their response should also be limited by the lack of previous contact with rams (Gelez et al, 2004).…”

Section: Discussionmentioning

confidence: 92%

“…As the introduction of rams also induces an increase of LH secretion that ends in ovulation in female lambs (Knights et al, 2002), it may be used to advance puberty in extensively managed flocks (Bichard et al, 1974). However, in general, oestrus, ovulation and conception rates are lower in ewe lambs than in adult ewes (for review see: Kenyon et al, 2014). In extensive grazing systems female lambs commonly do not reach the threshold body weight to achieve puberty during their first breeding season (Foster et al, 1985), and thus farmers delay their first breeding period until their second autumn (Kenyon et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

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Reproductive response of mature and nulliparous yearling ewes to the ram effect during the non-breeding season

Ungerfeld

2016

Small Ruminant Research

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Section: Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Reproductive response of mature and nulliparous yearling ewes to the ram effect during the non-breeding season

Ungerfeld

2016

Small Ruminant Research

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“…Heavier ewes achieved puberty in the first breeding season, had a higher number of lambs, and produced more multiples at 2 years old (Edwards et al, 2014). Kenyon et al (2014) reported a greater effect of ewe LW on reproductive performance in younger ewes than older ewes. All these data indicate that well-developed ewes may have an advanced reproductive performance compared to weaker ewes at the same age.…”

Section: Fertility Rate and Multiple Birth Ratementioning

confidence: 88%

Effects of ewe live weight and age on reproductive performance, lamb growth, and survival in Central Anatolian Merino sheep

et al. 2015

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Abstract. The aim of this study was to evaluate the effects of premating ewe weight and age on ewe reproductive performance, lamb growth and survival in Central Anatolian Merino (CAM) sheep.The trial included 4935 ewes and 5548 lambs from 23 breeder flocks in Eskişehir Province. The live weights (LWs) and ages of the ewes were recorded 1 week before the mating season. The number of lambs born, fertility rate, multiple birth rate (MBR), and lamb survival rate (SR) at days 75 and 120 were determined. The effects of the LW and age of the ewe were found to be important for the reproductive performance of ewes and for the lamb's growth rate (P < 0.05-0.001). Ewe MBRs and the birth weight (BW) and LW of the lambs at days 75 and 120 increased proportionally with the increase in LW in ewes prior to mating. The fertility rate and MBR were lower (P < 0.05-0.001) in 1.5-year-old ewes than in older ewes. However, lambs' SR at days 75 and 120 were not affected by the premating LW and age of the ewe. In summary, a better reproductive performance and lamb growth rate in CAM flocks may be achieved by the selection of breeding ewes from ewes weighing more than 60 kg.

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“…Ewes generally reach their mature body size after 4 or 5 years so a high reproductive effort in early life may hinder their full body development and ultimately shorten lifespan. The breeding of ewes early in life as hoggets can lead to a reduced mature BW, however no effects of longevity have been detected yet (Kenyon et al, 2014). Although breeding ewes to first lamb at 1 year of age is currently advocated in New Zealand as an efficient management option to increase lifetime productivity, results from this study suggest that further investigation in contrasting flock environments may lead to different conclusions.…”

Section: Discussionmentioning

confidence: 76%

Effects of the level of early productivity on the lifespan of ewes in contrasting flock environments

Douhard

Jopson²,

Friggens

et al. 2016

animal

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Selection for high levels of prolificacy has allowed substantial improvements in the production efficiency of New Zealand (NZ) sheep farms, but the consequences on ewe lifetime performance are mostly unknown. In this study, the relationship between the level of prolificacy early in ewes' productive lives and their probability to survive later (i.e. stayability) was evaluated in two contrasting NZ flock environments. Records were obtained from 6605 ewes from four ram breeder flocks representing either a moderate ( n = 2) or a highly variable ( n = 2) nutritional environment. All ewes lambed for the first time at 2 years of age and were mated the following year. The number of lambs born during the first 2 years of productive life (NLB 2-3 ) was used as a measure of early prolificacy. Effects of NLB 2-3 on stayability to 4, 5, 6, 7 and 8 years old were analysed using logistic regression. Curvilinear effects (logit-transformed) were detected ( P < 0.05) until stayability to 6 years and to 8 years old in the highly variable and the moderate environment, respectively. The NLB 2-3 that resulted in maximum expected stayability to various ages was 3.9 to 4.2, and 4.5 to 4.7 lambs in the highly variable and in the moderate flock environments, respectively. In addition, ewe stayability was reduced when the proportion of the litter that survived from birth to weaning (i.e. ewe rearing ability) was submaximal during the early productive life. High prolific ewes had a low rearing ability whatever the environment whereas the rearing ability of lowly prolific ewes was apparently more sensitive to the nutritional environment. The poor maternal performance of ewes with low levels of NLB 2-3 led to a premature culling by breeders whereas the high early reproductive effort associated with high levels of NLB 2-3 seemed to be at the cost of ewes' survival, even in the moderate flock environment. In conclusion, the flock environment influenced the level of early prolificacy beyond which ewe longevity was reduced. It is suggested that further selection for high and early prolificacy in NZ flocks is likely to impair ewes' lifetime productivity.

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Breeding ewe lambs successfully to improve lifetime performance

Cited by 75 publications

References 103 publications

Reproductive response of mature and nulliparous yearling ewes to the ram effect during the non-breeding season

Reproductive response of mature and nulliparous yearling ewes to the ram effect during the non-breeding season

Effects of ewe live weight and age on reproductive performance, lamb growth, and survival in Central Anatolian Merino sheep

Effects of the level of early productivity on the lifespan of ewes in contrasting flock environments

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