Natural factors affecting puberty and reproductive performance in ewe lambs: A review

Dýrmundsson, Ó. R.

doi:10.1016/0301-6226(81)90030-0

Cited by 64 publications

(22 citation statements)

References 43 publications

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“…For instance, ewes born in the summer will be exposed to breeding during their 6th to 12th mo (in order for them to lamb during their 11th to 17th mo of age as precocious ewe lambs) in a season of low reproductive activity (December to end of July) compared with ewes born in winter or fall whose exposure would occur under a season of better reproductive activity. These results agree with those of Dyrmundsson (1981). Perinatal mortality, as well as frequencies of multiple births, were observed within arbitrary age categories to examine trends associated with age at first lambing.…”

Section: Resultssupporting

confidence: 81%

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Lambing Performance of Morlam and Dorset Ewes under Accelerated Lambing Systems

Iñíguez

Quaas

Vleck

1986

Journal of Animal Science

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Two accelerated lambing systems, Morlam using Morlam sheep (USDA, Beltsville 1966to 1975 and Carnal using Dorset ewes (Cornell 1978(Cornell to 1981, were evaluated for first lambing ages, interlambing intervals and conception probabilities. Morlam ewes were continuously exposed to rams over the year, while Carnal Dorset ewes were exposed every other month. Morlam lambs were mated as early as 367 d of age and Carnal Dorset lambs as early as 340 d. Early lambing was associated with higher rates of perinatal mortality (P>.05) and smaller litter size (P<.O1). Lambing years among Morlam ewes and season of birth of Carnal Dorset ewes influenced (P<.01) their first lambing ages. Lambing intervals averaged 293 and 303 d among Morlam and Carnal Dorset ewes, respectively. Age at first lambing and season in which the previous lambing occurred with influential factors (P<.01) on lambing intervals of Morlam ewes; longer intervals resulted when ewe lambs were mated at early ages (<12 too), and when the previous lambing occurred in winter. Estimates of conditional probabilities of conception by month given the occurrence of estrus, reflected seasonal changes in both systems. The overall probability of conception for the Morlain system (P=.16) was relatively higher than that for the Carnal Dorset system (P=.14); numbers of lambings per ewe per yr were 1.28 and 1.21, respectively. Estimates of heritability for age at first lambing, lambing interval and conception probability were. 31, .06 and .30, respectively.

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Section: Resultssupporting

confidence: 81%

“…Fewer live lambs per ewe were produced among precocious ewe lambs, because of higher rate of perinatal mortality (although statistically nonsignificant) and (or) decreased frequency of twins (X ~ (4) = 19.73, P<.01). Similar trends were found in other analyses (Branford-Oltenacu and Boylan, 1981 ;Dyrmundsson, 1981).…”

Section: Resultssupporting

confidence: 75%

Lambing Performance of Morlam and Dorset Ewes under Accelerated Lambing Systems

Iñíguez

Quaas

Vleck

1986

Journal of Animal Science

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“…Ewe hoggets displayed shorter and less intense periods of oestrus, and were less likely to seek the ram than mature ewes (Dyrmundsson 1973(Dyrmundsson , 1981Edey et al 1978), and rams experienced more diffi culty mating young ewes compared with mature ewes (Edey et al 1978;Rosciszewska 1985). In addition, ram hoggets were less suitable for breeding with ewe hoggets than either two-tooth (18-20 months of age) rams or mature rams (Kenyon et al 2007).…”

Section: Introductionmentioning

confidence: 94%

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

Kenyon

Smith

Morel

et al. 2009

New Zealand Veterinary Journal

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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.

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“…Using survey data, Kenyon et al (2004a) reported that the number of lambs present 1 month after lambing increased as the ram : ewe lamb ratio was reduced; however, below a ratio of 1 : 25 there was no further advantage. Ewe lambs display shorter and less intense periods of oestrus than do mature ewes and are less likely to seek the ram (Edey et al 1978;Dyrmundsson 1981), resulting in rams experiencing more difficulty mating with ewe lambs than with mature ewes (Edey et al 1978;Rosciszewska 1985). Best-practise guidelines now recommend exposing ewe lambs to vasectomised rams prebreeding.…”

Section: Introductionmentioning

confidence: 95%

Proportion of rams and the condition of ewe lambs at joining influences their breeding performance

Kenyon

West

2010

Anim. Prod. Sci.

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The aim of the present study was to examine the effects of ram : ewe lamb ratio and condition score on the reproductive performance of ewe lambs. In the 2007 study, ewe lambs were bred with rams, at ram : ewe lamb ratios of 1 : 30, 1 : 50, 1 : 75 or 1 : 100. In the 2008 study, ewe lambs were bred at ratios of 1 : 31, 1 : 50, 1 : 75 or 1 : 100. Ewe lambs were bred over two 17-day periods. In both studies, ewe lambs bred in the first 17 days of breeding only were heavier (P < 0.05) than those bred in the second 17-day period only, and those ewe lambs diagnosed as twin-bearing were heavier (P < 0.05) than their single-bearing counterparts. Ewe lambs with a condition score of 2.5 or greater were more likely (P < 0.05) to be bred, and be pregnant, in the first 17 days of breeding than those of condition score 1.5 or 2.0. Over the entire 34-day breeding period, ewe lambs with a condition score of 2.5 or greater had higher (P < 0.05) pregnancy rates than those with a condition score of 2.0, which in turn had higher rates than those of 1.5. In the 2007 study, after 34 days of breeding, there were no differences (P > 0.05) in pregnancy rates among the different ram : ewe lamb ratios. While in the 2008 study, pregnancy rates after 34 days were greater (P < 0.05) in the 1 : 50 compared with both the 1 : 75 and 1 : 100 treatments. Pregnancy rates of 1 : 31 ewe lambs were greater (P < 0.05) than those of 1 : 75 ewe lambs. In the 2007 study, pregnancy rates of ewe lambs to the first 17 days of breeding were greater (P < 0.05) for those bred at a ratio of 1 : 75 than for those bred at 1 : 50, and tended to be greater (P = 0.08) than for those bred at 1 : 100. In addition, those bred at a ratio of 1 : 30 tended to have higher pregnancy rates (P = 0.07) than those bred at 1 : 50. While in the 2008 study, pregnancy rates to the first 17 days of breeding were greatest (P < 0.05) in the 1 : 31 and 1 : 50 treatments groups. In conclusion, the results of the present study indicate that achieving greater liveweights and higher condition scores of ewe lambs at breeding will increase the proportion pregnant, especially early in the breeding period. The data also suggest, in combination with the results of previous research, that farmers should consider utilising ram : ewe lamb ratios lower than 1 : 100, although further studies are warranted.

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Natural factors affecting puberty and reproductive performance in ewe lambs: A review

Cited by 64 publications

References 43 publications

Lambing Performance of Morlam and Dorset Ewes under Accelerated Lambing Systems

Lambing Performance of Morlam and Dorset Ewes under Accelerated Lambing Systems

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

Proportion of rams and the condition of ewe lambs at joining influences their breeding performance

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