Lifetime traits comparison between annual and accelerated lambing systems for dairy ewes

El-Saied, U.M.; Fuente, L. F. de la; Primitivo, F. San

doi:10.1016/j.livsci.2005.11.003

Cited by 5 publications

(5 citation statements)

References 17 publications

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“…Production Traits. The genetic model was always supported by the data and heritability estimates were in line with estimated values previously reported for the respective traits in this breed (Othmane et al, 2002;El-Saied et al, 2006). However, the magnitude of the estimated heritabilities for these traits was lower than those reported for other dairy sheep breeds performing under less variable environments; for example, Lacaune (Barillet and Boichard, 1987).…”

Section: Repeatabilities Heritabilities and Ratios Of Permanent Varsupporting

confidence: 88%

Genetic determination of fatty acid composition in Spanish Churra sheep milk

Sánchez

Primitivo

Barbosa

et al. 2010

Journal of Dairy Science

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The objective of this study was to estimate the genetic variation of ovine milk fatty acid (FA) composition. We collected 4,100 milk samples in 14 herds from 976 Churra ewes sired mostly by 15 AI rams and analyzed them by gas-liquid chromatography for milk fatty acid composition. The studied traits were 12 individual FA contents (proportion in relation to the total amount of FA), 3 groups of fatty acids [saturated fatty acids (SFA), monounsaturated FA (MUFA), and polyunsaturated FA (PUFA)], and 2 FA ratios (n-6:n-3 and C18:2 cis-9,trans-11:C18:1 trans-11). In addition, percentages of fat and protein and daily milk yield were studied. For the analysis, repeatability animal models were implemented using Bayesian methods. In an initial step, univariate methods were conducted to test the hypothesis of the traits showing additive genetic determination. Deviance information criterion and Bayes factor were employed as model choice criteria. All the studied SFA showed additive genetic variance, but the estimated heritabilities were low. Among unsaturated FA (UFA), only C18:1 trans-11 and C18:2 cis-9,cis-12 showed additive genetic variation, their estimated heritabilities being [marginal posterior mean (marginal posterior SD)] 0.02(0.01) and 0.11(0.04), respectively. For the FA groups, only PUFA showed significant additive genetic variation. None of the studied ratios of FA showed additive genetic variation. In second multitrait analyses, genetic correlations between individual FA and production traits, and between groups of FA and ratios of FA and production traits, were investigated. Positive genetic correlations were estimated among medium-chain SFA, ranging from 0 to 0.85, but this parameter was close to zero between long-chain SFA (C16:0 and C18:0). Between long- and medium-chain SFA, estimated genetic correlations were negative, around -0.6. Among those UFA showing significant additive genetic variance, genetic correlations were close to zero. The estimated genetic correlations among all the investigated FA, milk yield, and fat and protein percentages were not different from zero. Our results suggest that low additive genetic variation is involved in the determination of the FA composition of milk fat in Churra sheep under current production conditions, which results in low values of heritabilities.

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Section: Repeatabilities Heritabilities and Ratios Of Permanent Varsupporting

confidence: 88%

Genetic determination of fatty acid composition in Spanish Churra sheep milk

Sánchez

Primitivo

Barbosa

et al. 2010

Journal of Dairy Science

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“…Moreover, a high replacement rate was observed in the flocks in our study, resulting in a short ewe lifespan (approximately 4.0 yr). The lifespan value in our study was lower than that in Churra dairy ewes submitted to an annual lambing system (5.7 yr) or to an accelerated lambing system (6.5 yr) in Castilla y León, as reported by El-Saied et al (2006). Although most farms suckled the lambs from their mothers (Table 4), artificial lamb rearing with milk powder substitutes was done in approximately onethird of the farms (automatic, 80.8%; manual, 19.2%).…”

Section: Feeding and Management Practicescontrasting

confidence: 68%

Structure and performance of Awassi and Assaf dairy sheep farms in northwestern Spain

Sendra

Caja

González-González³

et al. 2011

Journal of Dairy Science

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Data of 69 dairy sheep farms (70% Assaf and 30% Awassi crossbred), located in the Spanish Autonomous Community of Castilla y León and grouped for receiving technical advice, were used to study their structure and performance. Farm surface was 55.4ha, on average. Approximately 25% of the farms did not have cultivation land, and the other 75% had, on average, 73ha (from which 67% were devoted to forage). Farms used 2.1 annual work units (familiar, 90%), 493 ewes, and yielded 147,000 L/yr of milk. Farmers were tenant (84%), younger than 45 yr (70%), had new houses, and were grouped in cooperatives (83%). Sheep were fed indoors (occasional grazing only) in modern loose stalls and had machine milking. Planned mating (summer to fall) was done in 91% of farms (hormonal treatment, 54%) but artificial insemination was scarce (23%). Annual milk sales averaged 309 L/ewe (fat, 6.5%; protein, 5.3%; log(10) somatic cell count, 5.7), and milk was sent to local dairy industries for cheese production, and 1.35 lambs/ewe were harvested as milk-fed lambs (lechazo). Artificial lamb rearing was done in 38% of farms (automatic, 81%; manual, 19%). Total mixed rations were used in 33% of farms, and the rest used rationed concentrate (including self-produced cereals) according to physiological stage of the ewes (0.45 to 1.97 kg/d) and ad libitum forage (dehydrated, 70%; hay, 68%; fresh, 25%; silage, 12%). The concentrate-to-forage ratio ranged between 32 and 61%. In total, 68% of farms bought more than half of the forage, and 87% of them bought more than half of the required concentrates. According to structural, productive, and managerial traits, 4 types of farms were differentiated by using multiple correspondence analysis and cluster analysis. Type groups were: 1) large-surface farms, devoted to cereal and forage production, predominantly with Awassi crossbreed sheep and a high level of self-consumed commodities (12% of the farms); 2) large flocks with intermediate farm surfaces devoted to forage production and predominantly with Assaf sheep (30% of the farms); 3) high-yielding farms, with intermediate sized flocks of Assaf sheep and very intensive management (42% of the farms); and, 4) no-land farms predominantly with Assaf sheep (16% of the farms). In conclusion, the dairy sheep farms studied showed more adoption of intensive production systems than traditional farms, which resulted in higher milk and lamb yields. Despite all of them being based on familiar units, as traditional farms, they were highly dependent on external resources and became more vulnerable, faced with future uncertainties of the market.

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“…Thus little genetic variation remained for age at second or third lambing after accounting for variation in age at first lambing. A significant heritability estimate of 0.1370.03 was also reported for age at first lambing in four flocks of Spanish Churra dairy ewes allowed to lamb up to three times every 2 yr and was larger than the estimate of 0.03 70.03 observed in six spring-lambing flocks (El-Saied et al, 2006).…”

Section: Tablementioning

confidence: 61%

“…However, crossbred yearling ewes that weaned lambs subsequently weaned 12% more lambs per year at second and third lambing compared to ewes that did not wean lambs as yearlings (Po0.05; Fogarty et al, 2007), and age at first lambing had an unfavorable genetic correlation of À0.45 with measures of productive life and a small unfavorable correlation of À 0.15 with lifetime number of parities in dairy ewes in an accelerated lambing system (El-Saied et al, 2006).…”

Section: Tablementioning

confidence: 91%