Improvement of the reproductive performance of Rasa Aragonesa flocks in frequent lambing systems. I. Effects of management system, age of ewe and season

doi:10.1016/0301-6226(89)90125-5

Livestock Production Science

Volume 22, Issue 1, May 1989, Pages 69-85

https://doi.org/10.1016/0301-6226(89)90125-5 Get rights and content

Abstract

The means and the environmental effects for several reproductive characters were estimated in 4 flocks of Rasa Aragonesa ewes submitted to intensive reproduction systems.

The age at first lambing (AFL) of the ewe was lower in the flocks with a system of 3 lambings every 2 years (545 and 528 days, respectively, in Flocks A and B) than in the flocks under continuous mating (688 and 599 days, respectively, in Flocks C and D). Ewes born multiple have a greater AFL while ewes born in spring have the smallest AFL.

Conception rate was over 0.80 in all the mating seasons of Flocks A and B. The average interval between lambings of the flocks under continuous mating was 286 and 253 days, respectively, in Flocks C and D. Both flocks present two differentiated seasons: the favourable one (lambings from April to September), with intervals between 7 and 8 months, and the unfavourable one (lambings from October to March), when this interval increases up to 301 days.

Average litter size was between 1.19 (Flock D) and 1.48 (Flock B). The factors season of lambing and age of the ewe are those with the greatest effect on litter size.

Résumé

On a estimé les moyennes et les effets du milieu sur plusieurs caractères de reproduction dans quatre troupeaux ovins d'Aragon soumis à un système de reproduction intensif.

L'âge des brebis au premier agnelage (AFL) est inférieur dans le système de trois agnelages en deux ans (545 et 528 jours, respectivement, dans les troupeaux A et B) que dans le système de lutte permanente (686 jours pour C et 599 jours pour D). Les brebis nées multiples ont un AFL plus élevée tandis que celles nées au printemps ont l'AFL le plus court.

La fertilité des troupeaux A et B est superieure à 0.80 dans toutes les saisons de lutte. L'intervalle moyen entre mises-bas est de 286 jours et de 253 jours dans les troupeaux C et D respectivement. On retrouve dans ces deux troupeaux, deux époques très différentes: l'une favorable, pour les misesbas entre avril et septembre compris, où la moyenne de l'intervalle entre mises-bas oscille entre 7 et 8 mois, et l'autre défavorable pour les mises-bas entre octobre et mars, au cours de laquelle l'intervalle augmente jusqu'à 301 jours. La prolificité moyenne des troupeaux est de 1,21 pour A, 1,48 pour B, 1,19 pour C et 1,18 pour D. Les effets qui influencent le plus la prolificité sont la saison et l.âge de la brebis.

Zusammenfassung

Bei vier Schafherde der Rasse Aragonesa, die einem intensiven Reproduktionssystem unterzogen worden waren, wurden die Mittelwerte und Umwelteinflüsse der verschiedenen Reproduktionsmerkmale geschätzt.

Das Alter der ersten Lammung (AFL) der Schafe war bei den Herden mit drei Lammungen alle zwei Jahre kürzer (545 und 528 Tage bei den Herden A und B) als bei den Herden mit ständiger Deckzeit (688 und 599 Tage bei den Herden C und D). Die in Mehrlingsgeburten geborenen Schafe hatten einen höheren AFL, während die im Frühjahr geborenen Schafe einen niedrigen hatten.

Die Konzeptionsrate lag über 0.80 in jeder der Deckzeiten der Herden A und B. Der Durchschnitt des Geburtsintervalls der Herden mit ständiger Deckzeit lag bei 286 und 253 für die Herden C und D. Beide Herden zeigen zwei verschiedene Epochen: die günstige (Geburten von April bis September) mit Intervallen zwischen 7 und 8 Monaten und die ungünstige, in der das Intervall bis zu 301 Tagen ansteigt.

Die mittler Wurfgrösse schwankte zwischen 1.19 (Herde D) und 1.48 (Herde B). Bei der Wurfgrösse spielen die Jahreszeit der Geburt und das Alter des Schafes die grösste Rolle.

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Cited by (17)

Comparison between linear and proportional hazard models for the analysis of age at first lambing in the Ripollesa breed
2015, Animal
Age at first lambing (AFL) plays a key role on the reproductive performance of sheep flocks, although there are no genetic selection programs accounting for this trait in the sheep industry. This could be due to the non-Gaussian distribution pattern of AFL data, which must be properly accounted for by the analytical model. In this manuscript, two different parameterizations were implemented to analyze AFL in the Ripollesa sheep breed, that is, the skew-Gaussian mixed linear model (sGML) and the piecewise Weibull proportional hazards model (PWPH). Data were available from 10 235 ewes born between 1972 and 2013 in 14 purebred Ripollesa flocks located in the north-east region of Spain. On average, ewes gave their first lambing short after their first year and a half of life (590.9 days), and within-flock averages ranged between 523.4 days and 696.6 days. Model fit was compared using the deviance information criterion (DIC; the smaller the DIC statistic, the better the model fit). Model sGML was clearly penalized (DIC=200 059), whereas model PWPH provided smaller estimates and reached the minimum DIC when one cut point was added to the initial Weibull model (DIC=132 545). The pure Weibull baseline and parameterizations with two or more cut points were discarded due to larger DIC estimates (>134 200). The only systematic effect influencing AFL was the season of birth, where summer- and fall-born ewes showed a remarkable shortening of their AFL, whereas neither birth type nor birth weight had a relevant impact on this reproductive trait. On the other hand, heritability on the original scale derived from model PWPH was high, with a model estimate place at 0.114 and its highest posterior density region ranging from 0.079 and 0.143. As conclusion, Gaussian-related mixed linear models should be avoided when analyzing AFL, whereas model PWPH must be viewed as better alternative with superior goodness of fit; moreover, the additive genetic background underlying this reproductive trait supports its inclusion into current genetic selection programs given its economic importance.
Opportunities for genetic evaluation of reproductive performance in accelerated lambing systems
2012, Livestock Science
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For both first and second lambing intervals, effects of number of lambs reared at previous lambing, ewe lamb fertility, and age at lambing were all not significant. Gabiña (1989) also reported that litter size at previous lambing did not affect lambing interval and that ewe age only affected lambing intervals in seasons characterized by low fertility. Effects of previous lambing season were significant for both lambing intervals: the first lambing interval averaged 10.8±0.2, 10.3±0.1, 9.7±1.1, and 11.2±0.3 month, respectively, for ewes lambing in spring, summer, autumn, and winter.
Data from a Polypay sheep flock managed in an accelerated lambing system were used to estimate means, heritabilities, and genetic correlations for ewe lamb fertility (ELF); age at first, second, and third lambing (AGE1, AGE2, and AGE3, respectively); first and second lambing interval (INT1 and INT2); and number of lambings by 38 month of age (LAMB3). Summer matings had lower fertility than autumn and winter matings. Heritabilities of ELF, AGE1, AGE2, AGE3, and LAMB3 were 0.14, 0.39, 0.28, 0.36, and 0.27, respectively (P<0.01) but heritabilities for INT1 and INT2 were only 0.00 and 0.09, respectively. The quantity AGEACC=[(age in months at ith lambing)—12i] was proposed to compare observed ages at lambing to those expected in an annual lambing system using a repeated-measures analysis and had heritability of 0.31 and repeatability of 0.90. Genetic correlations of ELF with AGE1, AGE2, and LAMB3 were −0.89, −0.91, and 0.89, respectively (P<0.01). Genetic correlations of LAMB3 with AGE1 and AGE2 were −0.49 and −1.00, respectively. Genetic correlations of ELF and LAMB3 with direct genetic effects on WW were approximately −0.70, but correlations with maternal genetic effects on WW were 0.88 (P<0.10) and 0.58, respectively. Litter size was independent of ELF and LAMB3. Initial selection on ELF, augmented by additional selection on ewe ages at subsequent lambings, may allow prediction of genetic merit for reproductive performance and increase the frequency of lambing in accelerated lambing systems.
Factors influencing productive longevity of Awassi and Najdi ewes in intensive production systems at arid regions
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This finding agrees with Nugent and Jenkins (1992) who reported that intensive culling would increase production costs via growing or purchasing replacements, extra labor cost for ewe-lambs at lambing and additional feed. María and Ascaso (1999) and Gabina (1989) reported that litter size increased progressively with advance in parity. Litter size improved with advance in age through increased ovulation rate, uterine capacity and other maternal traits affecting the reproductive efficiency of the ewe (Fahmy, 1996).
Length of productive life (LPL) of a ewe is a trait of considerable economic importance in sheep farming. Records of 66,050 Awassi and 12,010 Najdi ewes belong to 28 flocks in the northern part of the Arabian Peninsula were used to investigate factors influencing their LPL under intensive production systems at arid regions. Ewes with first lambing January 1, 2003 through December 31, 2009 were subjected to survival data analysis. Weibull distribution model was used to explore different explanatory variables affecting LPL. Parity, breed, lambing interval, age at first lambing, flock effect and type of lambing were the variables with the largest contribution to the likelihood function for LPL. Average age at first lambing was 16.5 ± 1.18 and 17.7 ± 1.76 months for Awassi and Najdi ewes, respectively. Average LPL was 2204 ± 8.1 and 1635 ± 11.0 days for Awassi and Najdi ewes, respectively. Within analyzed LPL, Awassi ewes had an average of 4.1 ± 0.27 parities compared to 3.3 ± 0.34 for Najdi ones. Awassi ewes were more adaptable to intensive production system than Najdi ewes under arid conditions. Najdi ewe was 1.8 ± 0.32 more likely to be culled than Awassi ewe under the same conditions. The most important factor affecting LPL in the overall risk analysis was parity number. The relative culling risk was decreasing continuously in both breeds from the first parity (Awassi = 3.5, SE = 0.31; Najdi = 5.17, SE = 0.41) to the last one (Awassi = 0.45, SE = 0.14; Najdi = 0.63, SE = 0.42). The most appropriate lambing intervals (LI) were 221–340 days for Awassi and 251–310 days for Najdi ewes. LI below or above these ranges were significantly increased the risk of culling. Ewes lambed for the first time at ≤13 months were under considerable culling risk (Awassi = 1.42, SE = 0.19; Najdi = 2.73, SE = 0.33) compared to ewes lambed at older ages. The research showed that the optimum ages at first lambing were 17–19 months for Awassi and 20–22 months for Najdi. Ewes lambed triplets or more were under higher culling risk (Awassi = 1.72, SE = 0.10; Najdi = 1.97, SE = 0.19) than ewes lambed twins or singles. Interaction analysis showed that ewes lambed triplets or more during parity #1 were 3.42 ± 0.50 more likely to be culled than ewes lambed singles during the same parity. LPL could be increased by allowing optimum lambing intervals, mating for the first time at maturity stage, and avoiding enhancement of large litter sizes particularly during early and late parities. Different management and housing systems applied in different flocks showed significant effects on culling risk. Considerable variations in calculated LPL were due to breed and flock effects. This can be utilized by sheep breeders to increase LPL through genetic and environmental manipulations. Genetic evaluation of longevity trait in Awassi and Najdi breeds should be conducted, which will be of importance for sheep breeding programs at arid regions.
Litter size, lambing interval and lamb mortality of Salz, Rasa Aragonesa, Romanov and F<inf>1</inf> ewes on accelerated lambing management
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Litter size, lamb mortality at birth and lambing interval of the native Spanish breed Rasa Aragonesa (RA), Romanov (RO), their F₁ cross (RA × RO) and the composite line Salz, with 50% RA and 50% RO (SA), were studied under an accelerated lambing system. The data comprised 25 960 records collected from 1986 to 1992 during which 5372 ewes managed to lamb three times every 2 years. The fixed effects investigated were genotype, parity, lambing season and their first order interactions. Litter size was added to the model used to analyse for lamb mortality and lambing interval. All the main factors had a significant effect (p < 0.01) on the three traits studied. The first-order interactions of genotype with season, parity and litter size were significant except for genotype X season on lambing interval. Least squares means for the four genotypes, RA, RO, F₁ and SA were 1.40, 2.34, 1.87 and 1.71, respectively, for litter size, all differing significantly from each other. The corresponding figures for lamb mortality were 0.11, 0.25, 0.15 and 0.17 and for lambing interval were 257, 280, 228 and 255, respectively. The RO being significantly different from the other genotypes, litter size increased and both lamb mortality and lambing interval decreased with advance in parity. Litter size was significantly larger in winter and spring (1.60) and smaller in summer (1.4). Lambing interval was longest in spring and summer than in winter and autumn (p < 0.05). Lamb mortality was similar in various seasons. The results indicated that the composite line SA has a good potential for production systems requiring improved prolificacy or accelerated lambing management. Its advantage over the use of F₁ is the simplification in husbandry resulting from using only one genotype.
Analyses of lamb weight and ewe litter size in various lines of Spanish Merino sheep
1998, Small Ruminant Research
Data on weights of 4425 lambs and on 3355 litters of 974 ewes from six lines of an experimental flock of Merino sheep were analyzed. The objective was to estimate the effects of line, sex, type of birth, year–season of lambing and age of dam, as well as inbreeding depression and heterosis. Results showed that lines with low potential for growth in contrast were more prolific. In weight traits, the depression due to a 10% increase in inbreeding varied from 17% to 20% of the average performance. Heterosis was of similar magnitude, but obviously, in the opposite direction. Neither inbreeding depression nor heterosis showed a significant effect on litter size. Average performances for weights and litter size for the six lines were similar, if not slightly higher, than those of the main meat sheep breeds in Spain. It may be more convenient to cross the six lines into a single flock which could constitute the framework for Merino meat production improvement.
Effect of mating season and level of body reserves on fertility and prolificacy of Manchega ewes
1994, Small Ruminant Research
A flock of 530 Manchega ewes, under semi-intensive regime and a reproductive program of three births per 2 years, was used to study the effect of mating season (MS), level of energy reserves at mating, measured by body condition scoring at mating (BCM), and live weight at mating (LWM) on fertility and prolificacy. Fertility of the flock was affected by BCM (P<0.05), while LWM had no influence and MS was found to have an effect with a P-tail of 8%. December matings gave highest value for fertility (89.9%) compared to April (82.1 %) and August (80.4%). In order to study the relationship between BCM and fertility, a logistic regression model was used, with which a good prediction was obtained (P<0.05). Prolificacy was only affected by LWM (P<0.05) with a significant prediction (P<0.01) through a logistic regression. As LWM increased, the probability of twin birth increased. Body condition score (BCS) evolution has also been studied at different points of the reproductive cycle for the effect of the previous cycle on fertility and prolificacy. Fertility was affected by BCM, while prolificacy was influenced not only by LWM but also by live weight in the next phase.
En un rebaño de 530 ovejas de raza Manchega explotadas en régimen semi-extensivo, con un ritmo reproductivo de tres partos cada dos años, se ha estudiado el efecto que sobre la fertilidad y la prolificidad tienen la época de monta (MS) y el nivel de reservas energéticas en la monta, medido por medio de la nota de condición corporal (BCM) y el peso vivo (LWM). La fertilidad del rebaño se vió estadísticamente afectada por la BCM (P<0.05), mientras que la LWM no influyó y la MS alcanzó una significación estadística del 8%. Las cubriciones de diciembre alcanzaron el valor más alto de la fertilidad (89.9%), frente a las de abril (82.1%) y agosto (80.4%). Para estudiar la relación entre la fertilidad y la BCM se ensayó una regresión logística, mediante la cual se consigue una buena predicción (P<0.05). Respecto a la prolificidad, sólo se vió afectada por el LWM (P<0.05) también con un buen ajuste (P<0.01) de la regresión logística, en el sentido de que al aumentar W LW se incrementa la probabilidad de conseguir parto doble. También se ha estudiado la evolución de la condicion corporal (BCS) en diferentes puntos del ciclo reproductivo para tratar de estudiar el efecto del ciclo anterior sobre la fertilidad y prolificidad del siguiente, llegandose a la conclusión de que la fertilidad se vé afectada por BCM, mientras en que la prolificidad influyen tanto LW a la monta como LW del periodo immediatamente posterior.

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^☆: Project financed by “Comisión Asesora para la Investigación Ciéntifica y Técnica” (CAICYT).

^∗∗: Present address: Departamento de Agricultura y Pesca, Gobierno Vasco, Granja Modelo, Apartado 46, Vitoria-Gasteiz, Spain.

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Abstract

Résumé

Zusammenfassung

Livest. Prod. Sci.

El empleo de la presencia de machos como técnica de inducción y sincronización de celos durante el período de anoestro estacionario en la oveja Rasa Aragonesa

Selection for early puberty and increased fertility at first mating

Economic importance of the reproductive results in flocks of the Ebro Valley

Puberty and early reproductive performance in sheep

I. Ewe lambs. Anim. Breed. Abstr.

Effect of rams on the onset of breeding activity in Clun Forest ewe lambs

J. Agric. Sci.

Studies on sheep production records. II. Effect of environmental factors on fertility, fleece and body weight of ewes

Acta Agric. Scand.

Influencia del efecto macho sobre la aparición de la pubertad en corderas Segureñas, en función de la época de nacimiento. II. Jornadas sobre Producción Animal

I.T.E.A.

Influencia de la alimentación sobre la actividad reproductiva de la oveja Rasa Aragonesa en primavera. I. Efecto del nivel de alimentación en pastoreo

I.T.E.A.