Reproductive Performance Of Ewes Research Articles

Influence of classification levels of ram sexual activity on spring breeding ewes

Ram lambs (7–8 months old) and mature rams (19–20 months old) were used to evaluate the effect of classification levels of male sexual performance on reproductive performance of ewes during spring breeding. In Exp. 1, sexually active ram lambs with high (1.8±0.3; n=5) and low (0.9±0.2; n=5) sexual performance scores (HP and LP; mean±S.E.M.) were used in single sire breeding pens. Ewes ( n=305) were stratified by age and assigned to 10 pens for 34 days starting in late March. For Exps. 2 and 3, two replicates were conducted for 2 years with sexually active mature rams in a single sire mating scheme. For Exp. 2, HP rams ( n=5) averaged 3.6±0.2 ejaculations and LP rams ( n=7) 1.8±0.2 ejaculations for sexual performance scores based on nine, 30 min serving capacity tests (SCT). Polypay ewes ( n=152 to 153 per year) were stratified by age and assigned to pens each year for 34–38 days starting in late March for years 1 and 2. For Exp. 3, HP rams ( n=6) averaged 3.7±0.1 ejaculations and LP rams ( n=10) 2.3±0.1 ejaculations for sexual performance scores based on 18, 30 min SCT. Polypay ewes ( n=229 in year 3 and n=244 in year 4) were stratified by age and assigned to pens each year for 34 days starting in late March. In Exp. 1, lambing rates for ewes bred to HP versus LP ram lambs did not differ (65.8 versus 53.0; P=0.20). Prolificacy tended ( P=0.06) to be increased by 0.1 lambs in ewes bred by LP ram lambs. Total number of lambs born per ewe present at lambing, and lambing distribution were not altered by HP and LP ram lambs. In Exp. 2, lambing rates for fall-lambing ewes bred to mature HP or LP rams did not differ (58.1 versus 60.1; P=0.78). In Exp. 3, lambing rates for fall-lambing ewes bred to mature HP or LP rams did not differ (74.3 versus 69.0; P=0.35). There was no difference ( P>0.10) between years for Exp. 2 or Exp. 3, and mature HP and LP rams did not affect the other reproductive variables monitored. Analyses of the combined data for Exps. 2 and 3 indicated only a year difference ( P<0.001) in lambing rates and total lambs born. Present studies indicate that different sexual performance classifications for ram lambs and mature rams did not alter lambing rates or distribution of lambing of Polypays bred in late March to April. These results indicate that HP and LP, sexually active, Polypay rams and ram lambs with average to high quality semen can provide a source of rams for spring breeding Polypays in ambient conditions and that there was no advantage to using HP over sexually active LP ram lambs or rams.

Sincronização do estro, indução da ovulação e fertilidade de ovelhas deslanadas após tratamento hormonal com gonadotrofina coriônica eqüina

Utilizou-se a sincronização do estro com esponjas vaginais de 30mg de acetato de fluorogestona durante 12 dias para avaliar o efeito de diferentes doses de eCG sobre o desempenho reprodutivo de ovelhas. Na retirada das esponjas as ovelhas foram divididas em três grupos para receberem 0 (n=26), 200 (n=30) ou 400UI (n=30) de eCG. O estro foi detectado a cada 12h utilizando-se um rufião. As fêmeas foram inseminadas por laparoscopia 60h após a retirada das esponjas. Realizaram-se colheitas de sangue aos 5 e 18 dias pós-inseminação para dosagem de progesterona e determinação do número de ovulações e prenhezes, respectivamente. A fertilidade foi verificada por ecografia aos 60 dias e ao parto. Das 86 ovelhas 70,9% apresentaram estro. Essa porcentagem foi maior (P&lt;0,05) nas fêmeas tratadas com eCG: 96,7% (400UI) e 76,7% (200UI) versus 34,6% (0 UI). O intervalo entre o final do tratamento e o início do estro foi maior (P&lt;0,05) no grupo sem eCG, 54,7±6,3h versus 45,9±7,8h para 200UI e 40,4±10,3h para 400UI. Verificou-se menor (P&lt;0,05) número de ovulações e prenhezes no grupo sem eCG. A não aplicação de eCG influiu negativamente no desempenho reprodutivo de ovelhas deslanadas.

Reducing the impact of adverse summer-autumn pasture conditions on livestock performance: results from farmer experience

A group of 12 farmers managing a total of 8845 ha in the West Waikato Region of the North Island, conducted a project to understand and overcome poor livestock performance during the summer- autumn period. Pastures and livestock were monitored to measure the impact of the conditions. Metabolisable energy (ME) of pasture averaged 9.0, 9.8 and 9.3 mega joules per kg of dry matter over the 3 years of study and elevated levels of pasture toxins were consistently found from mid- January to the end of May. To counter these conditions, farmers adopted varying strategies including pasture management and alternative feeding (silage and forage crops). A computerbased tool that enabled the user to make livestock feeding decisions based on the pasture cover, the ME of the pasture, and the quantity and ME of a feed supplement was developed. Farmers were able to reduce the proportion of damaged livers in lambs from 60 to 40% of the flock, which was against the district trend. When the right strategies were implemented, lamb and cattle liveweight gains increased from 52 to 146 g/day and 0.34 to 0.5 kg/day respectively. On average, ewe reproductive performance also improved during the period from 2.4 to 2.8% of lambs scanned/kg ewe body weight. The project emphasised to farmers that their resident pastures did not meet the needs of a high performing livestock production system and that alternative feeding strategies were required if higher performance was to be achieved. Keywords: Androvax, livestock feeding, metabolisable energy, pasture toxins, zinc

Comparison of five crossbreeding types involving Timahdit, D’man and improved terminal sire breeds of sheep: ewe reproduction, lamb survival and growth performance

AbstractA crossbreeding experiment involving Timahdit (T), D'man (D) and improved sire breeds (M) was conducted to compare lamb production in five crossbreeding types: D ✕ D, T ✕ T, D ✕ T (DT), M ✕ T, and M ✕ DT lambs. Reproductive and production traits were analysed in 1187 litters, 1586 lambs born and 1346 lambs weaned, progeny of 605 ewes. Effects of crossbreeding type, year of birth, sex of lamb, age of dam, and type of birth were significant on the majority of traits studied. The D ✕ D and M ✕ DT crossbreeding system showed the highest litter sizes at lambing and at weaning with respective values in D ✕ D (2·17, 1·34) and M ✕ DT (1·72, 1·39). Ewes bearing the M ✕ DT cross lambs showed the highest (P &lt; 0·05) litter weight at weaning (28·28 kg) followed by those with M ✕ T (23·14 kg), and D ✕ D (22·53 kg) lambs. M ✕ DT and M ✕ T lambs were heavier and grew faster than the other lambs. On the other hand, lamb survival rates and growth traits were the lowest in D ✕ D but those in T ✕ T and D ✕ T genetic types of lamb were intermediate. Results showed that D as a dam breed had a favourable effect on litter size (P &lt; 0·01) but unfavourable effect on lamb survival and birth weight. The reproductive performance of DT crossbred ewes, due to their high prolificacy and lamb survival, associated with the favourable effect of an improved terminal sire (M) for growth traits, indicated that the three breed cross (M ✕ DT) could enhance lamb production in Morocco.

Ewe reproductive performance and growth rate of suckling-lambs on endophyte-infected perennial ryegrass pasture

Two groups (n=39) of Romney breeding ewes were maintained under the same grazing management on either endophyte-infected (E+) or endophytefree (E-) perennial ryegrass pasture for two years (1997-1998) following a one-year equilibration period. The ewes were naturally mated in March each year and ovulation rate at 1st mating was measured, and conception and the number of lambs born and weaned were recorded. All ewes were weighed monthly and lamb growth rates were determined between birth and weaning. Mean mating date was delayed by 1.8 days (P

Breed Genetic Components of Ewe Reproductive Performance and Lamb Survival Rates for Egyptian Rahmani and Ossimi Breeds and Their Crosses With Finnsheep

Breed Genetic Components of Ewe Reproductive Performance and Lamb Survival Rates for Egyptian Rahmani and Ossimi Breeds and Their Crosses With Finnsheep

The implications of controlling grazed sward height for the operation and productivity of upland sheep systems in the UK. 4. The effect of seasonal pattern of nitrogen fertilizer application and annual stocking rate

Greyface (Border Leicester × Scottish Blackface) ewes, mated in October, were housed in winter and turned out after lambing in late March to one of four treatments replicated three times on perennial ryegrass (Lolium perenne)‐dominated pastures. On three of the treatments the stocking rate was 12·5 ewes plus lambs ha−1 annum−1 (SR12·5), whereas on the fourth it was 15·0 ewes plus lambs ha−1 annum−1 (SR15·0). There were two levels of applied fertilizer nitrogen (N), 152 kg N ha−1 annum−1 (N152) and 205 kg N ha−1 annum−1 (N205). Three patterns of nitrogen application were used: predominantly in spring (E), predominantly in autumn (L), and mainly in spring and autumn (E + L). Grazed sward surface height was controlled within the range 3·5–5·5 cm during spring and summer, and supplementary feed was offered when sward height was below 3·5 cm.The effects on animal performance, yield of silage and requirement for supplementary feed were measured over 3 years (1986–88). Management of the sward height within the specified limits resulted in similar levels of individual animal performance for all treatments, but treatment SR15·0N205E + L produced a significantly (P &lt; 0·05) greater output of lamb per hectare. There was no evidence to suggest that, by increasing the amount of N fertilizer applied in the autumn, ewe reproductive performance was increased. Neither the treatment with the lower level of N applied in the spring (SR12·5N152L) nor the high stocking rate treatment (SR15·0N205E + L) was self‐sufficient in winter feed (silage) production. SR15·0N205E + L also required more supplementary feed in both the lactation (38·1 kg ewe−1) and the mating (9·1 kg ewe−1) periods. SR12·5N152L required the second greatest amount of supplementary feed during lactation (36·1 kg ewe−1), whereas SR12·5N205E + L required the least supplementary feed over both periods (27·8 kg and 4·8 kg ewe−1). Taking all treatments together, there were significant (P &lt; 0·05) differences between years in lamb weaning weight (kg), lamb output (kg ha−1), yield of silage (kg ewe−1) and supplementary feed required (kg ewe−1), arising mainly from a lower level of herbage production in one year. Treatment SR12·5N152E generated the highest gross margin per hectare.

Effect of strategic supplementary feeding on ewe productivity under range conditions in North Kordofan, Sudan

Strategic supplementary feeding practices were imposed on ewes prior to mating (flushing) and during late pregnancy (steaming-up) at two locations in North Kordofan, Sudan. The objective was to improve ewe reproductive performance and increase lamb birth weight. A completely randomized block design was used and the results analyzed from the economic point of view. Strategic supplementary feeding of ewes increased conception and lambing rates ( P<0.01), reduced abortions ( P<0.01), and resulted in higher lamb birth weights ( P<0.05). The treatment also reduced ewe weight loss ( P<0.05) and caused no ewe mortality. Respective lambing rates for the supplemented and control ewes were 91.7 and 41.7%. Strategic supplementary feeding was economically more advantageous and could accrue up to 382540 additional Sudanese pounds (US $273.24) in returns. It was concluded that steaming-up and flushing are essential for improving ewe reproductive performance, increasing lamb birth weights, and minimizing pregnancy stress of ewes. Hence, the practice is recommended in similar ecological zones to improve productivity of desert sheep.

The effects of iodine deficiency on ewe fertility and perinatal lamb mortality

dAims. To substantiate a previous report of improved fertility and perinatal lamb mortality rate following iodine supplementation in a Manawatu Romney ewe flock. To contribute data which might be used to predict a response to iodine supplementation. dMethods. A controlled iodine supplementation trial was performed over 2 successive years. The possible confounding factor of different lambing paddocks on perinatal lamb mortality was removed by the reversal of the paddocks used by the supplemented and control ewes during the second year. dResults. During 2 successive years, iodine supplementation resulted in improved reproductive performance in a Manawatu Romney flock with 21% and 14% more lambs born to supplemented than to control mixed-age ewes in 1996 and 1997 respectively. Supplementation also resulted in improved perinatal lamb survival, although this effect was greater during the wetter 1996 Lambing season. Despite the production response during both years, a difference in lamb thyroid:bodyweight ratio was only noted following the drier 1997 winter. Ewe thyroid hormone concentrations before mating and during mid-pregnancy were poor indices of deficiency. dConclusions. Iodine deficiency should be included in the list of differential diagnoses for poor reproductive performance in ewes and in the investigation of high perinatal lamb mortality rates. dClinical significance. The annual cost associated with iodine deficiency in this Manawatu Romney flock is conservatively estimated at $6.00 per ewe. This economic loss is considerably greater than the annual cost of iodine supplementation using iodised oil.

Reproductive performance of ewes and preweaning growth of lambs from three native Moroccan breeds mated to rams from Moroccan and improved breeds

A total of 545 performance data of Timahdite, Sardi and Béni Guil ewes bred to Ile de France, Suffolk, Mérinos Précoce, and rams of their own breeds were studied during three breeding seasons. The breed of service ram had a significant effect on fertility and litter weight at weaning, but not on litter size at birth. Litters sired by rams from meat-type breeds, especially Ile de France, were heavier at weaning than litters sired by rams from native breeds. The breed of sire significantly affected the weight of lambs at birth and at 90 days, but not preweaning lamb survival. Progeny of Ile de France rams had the heaviest weights at birth and at 90 days (4.09 and 22.4 kg). The breed of dam did not significantly affect lamb growth, but had a significant effect on fertility, litter size at birth, and litter weight at weaning. Timahdite ewes weaned the heaviest litters (21.2 kg). We concluded that the use of rams from meat-type breeds, particularly Ile de France, on ewes from native breeds, increased litter weight at weaning by approximately 12% as compared with rams from native breeds.

Growth and Reproductive Performance of Small Ruminants under Intergrated Livestock-Oil Palm Production System

The effects of supplementation with mixed fodder or concentrate were investigated on the performance of a) growth of male lambs;md kids grazing extensively under oil palm trees and b) reproduction of ewes and goats stall-fed with native herbage. Supplemented kids and lambs had higher average daily weight gain than controls but the effect was only significant for those which received concentrate (p 0.05) on the reproductive performance of ewes apart fi om highest body weight of first lambing in animals supplemented with concentrate (p < 0.05). Native herbage available under oil palm trees of 5 years old was sufficient for growth and reproduction of sheep and goats. Concentrate was better than mixed fodder as supplement for enhancing the reproductive performance of goats but both appeared to have limited effects on the performance of reproduction in ewes and growth in male kids.

The effect of melatonin treatment in combination with progestagen pessaries on reproductive performance of ewes during the anoestrous period

AbstractThe objective of this study was to compare the effects of melatonin implants combined with intravaginal, progestagen-impregnated pessaries with the conventional treatment of progestagen pessaries followed by pregnant mare serum gonadatrophin (PMSG) on the reproductive performance of ewes during the anoestrous period.A commercial flock of 179 seasonally anoestrous Chios crossbred ewes was used. The ewes within the flock were randomly allocated to one of two groups. Ewes of group MP (melatonin + pessaries) received melatonin implants on 20 March (50 days before the target breeding date of 10 May) and were treated with intravaginal progestagen pessaries 35 days later (25 April). Ewes of group PP (pessaries + PMSG) were also treated with pessaries on 25 April. After 14 days the pessaries were removed from both groups and 500 i.u. PMSG was injected (i.m.) into ewes of group PP only. Fertile rams were introduced into both groups 24 h after sponge removal. Pregnancy rate and litter size were determined by ultrasound scanning 80 days after ram introduction.Pregnancy rate at first oestrus was significantly higher in group MP than in group PP (57 v. 40%, P &lt; 0·05). The overall conception rate during two oestrous cycles was significantly higher in group MP than in group PP (78 v. 59%, P &lt; 0·02). The groups did not differ significantly in the mean number of foetuses per pregnant ewe that conceived during the first or second oestrus after pessary removal (1·78 and 1·87, respectively). The total number of foetuses per treated ewe was higher in group MP than in group PP (1·39 v. 1·10) as a consequence of the difference in pregnancy rate.

The use of blood equol values in devising grazing management strategies for red clover-based pastures

Feeding and grazing trials were carried out to establish relationships between formononetin intakes and blood equol levels, and to characterise the build-up and clearance of free and conjugated equal in the blood of sheep feeding on either high (Grasslands Pawera) or low (G27) formononetin red clovers. In the feeding trials, blood equol levels were positively correlated with formononetin intakes, and levels peaked at 2-4 hours after feeding. In the grazing trial, groups of 10 sheep grazed either Pawera or G27 red clover pastures for l-, 2-, or 3-week periods while a control group was on grass-dominant pasture. Analysis of blood equal showed differences in the rates of accumulation and in the mean blood concentrations. Free equol was present in the blood of sheep after one day of grazing on Pawera whereas it was not detected in blood of sheep on G27 until 5 days after grazing began. Blood equal rose to equilibrium levels and remained thus until sheep were removed from the red clovers. The concentrations of equol in Pawera ewes were approximately three times those in G27 ewes. Free equoal was rapidly cleared from the blood and was below the limit of detection by day 2 after transfer to a ryegrass pasture. The 4-day lag between start of grazing and the appearance of free equal in the blood of ewes on G27 offered scope for devising grazing management strategies which might enable use of G27 for flushing without an adverse effect on fertility. Results of trials in 1995 and 1996, in which ewes grazed alternately for 3.5 or 3 days on G27 and then for 3.5 or 4 days on grass pastures (per week) for 4 weeks before and during a 4-week mating period showed that the reproductive performance of ewes was unaffected. Such on/off systems of grazing management, therefore, enable G27 to be grazed safely by ewes around the time of mating. Keywords: equol, ewe fertility, flushing, formononetin, grazing management, oestrogenic compounds, Trifolium pratense

Lupinosis of ewes around the time of mating reduces reproductive performance

Lupinosis was induced in Merino ewes by subcutaneous injections of phomopsin toxins, given for 2 weeks before and up to 2 weeks after the start of joining, and the reproductive performance of the injected ewes was compared with untreated control ewes. Two experiments were conducted in consecutive years, with similar results. The liver damage and impairment of liver function due to lupinosis were measured by increases in plasma activities of glutamate dehydrogenase and gamma glutamyl transferase, plasma concentration of bilirubin, and plasma clearance of bromosulfthalein. Ovulation rate was depressed by phomopsin administration (1.11 v. 1.33 for the combined phomopsin-treated and control ewes, P &lt; 0.001), and fewer phomopsin-treated ewes were pregnant (70.4% for the combined phomopsin-treated ewes v. 93.8% for the combined control ewes, P &lt; 0.01). Thus, fewer lambs were born to the phomopsin-treated ewes compared with the control ewes (66.0 v. 109.3% for the combined years, P &lt; 0.01). These results indicate that there may be severe detrimental effects of phomopsin intoxication on reproductive performance of ewes.

Effects of limit feeding a high-grain diet on puberty and reproductive performance of ewes.

In Exp. 1, 39 ewe lambs (initial BW 29 +/- .1 kg) were used in a 2 x 2 factorial arrangement with two breeds (Polypay and Targhee) and two diets (high-forage and high-grain) to examine the effects of restricting intake of a high-grain diet on onset of puberty and lamb performance. The experimental diets were fed from 13 to 40 wk of age. The high-forage diet was composed of 80% alfalfa cubes and 20% supplement. The high-grain diet was 90% concentrate and 10% alfalfa cubes. Feed intake of the diets was controlled so that lambs fed the high-grain diet had the same growth rate as those fed the high-forage diet. Plasma insulin concentration was higher (P < .001) for lambs fed the high-grain diet than for those fed the high-forage diet. However, no diet effect on age at puberty was observed. In Exp. 2, 88 mature Targhee ewes were used to determine the effects of limiting intake of a high-grain diet on pregnancy and number of lambs born per ewe. Intake of the high-grain diet was restricted to achieve similar ME intake between diets. There were no diet effects on number of lambs born per ewe or subsequent lamb performance. Ewes fed the high-forage diet had a lower (P < .001) weight gain than those fed the high-grain diet. It was concluded that restricting intake of high-grain diets is an effective alternative to feeding high-forage diets for meeting the nutrient requirements of ewe lambs and gestating ewes; however, no improvements on reproductive performance were observed.

The effect of supplementary minerals, retinol and α -tocopherol on the vitamin status and productivity of pregnant Merino ewes

Four hundred and twenty Merino ewes were divided into four treatment groups: control (NaCl at 175 g head-1 week-1 ), vitamins (salt containing 0.24 g/kg retinol plus 12 g/kg �-tocopherol), minerals (a multi-element mineral mix (Siromin ) at 175 g head-1 week-1) and vitamins plus minerals (mineral mix plus vitamins) in a two by two factorial design. Treatments started in November prior to mating and finished in May 1 week prior to lambing. Measurements of vitamin status and animal productivity were made on ewes and foetal and weanling lambs. Compared with salt, the mineral mix increased ewe body weight by up to 3% ( P &lt; 0.05), annual wool growth by 4.4% ( P &lt; 0.001) and birth and weaning weights of single lambs by 7.3% ( P &lt; 0.01) and 3.7% (P &lt; 0.05) respectively. Since ewes had been given selenium and cobalt bullets at weaning, the results suggest either that the bullets do not offer protection for the lifetime of the ewe and that additional bulleting is warranted, or that other minerals are limiting production. As pastures dried off, the concentrations of �-tocopherol and G-carotene fell and this was reflected in a decline in the concentrations of �-tocopherol and retinol in liver. However, the liver stores at the beginning of summer were sufficient to prevent the appearance of clinical signs of vitamin deficiency. Vitamin supplementation significantly increased the concentration of vitamins in the plasma and liver of ewes ( P &lt; 0.001)) but it had no significant effect on ewe reproductive performance or on ewe or lamb body weights or wool growth. Vitamin supplements increased the concentrations of retinol and �-tocopherol in the liver of foetal lambs, but even with supplements the levels remained well below normal adult reference values.

The effect of GnRH agonist (buserelin) treatment on day 12 post mating on the reproductive performance of ewes

AbstractAn investigation was conducted to determine the effects of treatment with the GnRH agonist buserelin on day 12 post mating on the reproductive performance of ewes. There was a non-significant (P &gt; 0·05) increase in nonreturn rate (control 0·76 v. buserelin 0·83) and litter size (control 1·51 v. buserelin 1·77) in three flocks. However, there was a significant (P &lt; 0·05) increase in the number of twin lambs born (control 20 v. buserelin 40) and litter size (control 1·44 v. buserelin 1·68) in the yearling flock. There was no effect of buserelin on oestrous cycle length, although there was a tendency for treated animals to have a longer gestation length and heavier lambs. In a ewe lamb flock there was no effect of buserelin on non-return rate or litter size assessed post slaughter on day 31 of pregnancy. However, ovulation rate tended to be greater in the treated animals, which suggests that buserelin may have induced the formation of accessory corpora lutea. These results indicate that buserelin treatment improves embryo survival and that this effect is particularly evident in yearling ewes.

Reproductive performance and genetic parameters for Australian Dorset Sheep

Reproductive performance of ewes in a large Dorset stud flock is reported. The data included 2488 ewes with 10016 joining records over 25 years. Average performance for reproductive traits were: fertility 92%, litter size 1.31, neonatal lamb survival 91%, lamb survival to weaning 85%, with overall lambs born 1.20 and lambs weaned 1.02 per ewe joined. Differences between breeds (Poll Dorset and Dorset Horn), season of birth (spring and autumn) and season of joining (spring and autumn) were significant for most reproduction traits. Linear and quadratic regressions for age of ewe at joining were highly significant for all traits (P &lt; 0.001) with maximum performance between three and six years of age. Estimates of heritability for ewe reproductive traits were: 0.062 � 0-02 for number of lambs born and 0.04 � 0.01 for number of lambs weaned per ewe joined, and component traits, 0.02 �0 -01 for fertility, 0 08 � 0 -02 for litter size and 0.00 � 0.01 for lamb survival. Estimates of repeatability were less than 0.14 for all the reproduction traits, which resulted in substantially higher predicted heritabilities when repeated records were used. Heritability estimates for average ewe lifetime performance, with approximately four records, were 0.08 � 0 06 for lambs born, 0.12 � 0.05 for lambs weaned, 0.08 � 0.04 for fertility, 0.l9 � 0 -04 for litter size and zero for lamb survival. The genetic correlations between litter size and lambs born and weaned were close to unity, whereas those for fertility were lower and declined from lambs born (0.6l � 0.22) to lambs weaned (0-45 � 0.30). The estimated heritability for ewe longevity, defined as the number of years the ewe remained in the breeding flock, was 0.00 � 0.03. The potential for genetic improvement in reproductive rate is discussed in relation to other reports in the literature and in the context of the roles of the Dorset breed in the Australian lamb industry. Increased reproductive rate in Dorset flocks impacts on stud profitability and the rate of genetic improvement from selection for other traits such as liveweight. The parameter estimates derived will be used in compiling breed-specific parameter sets for genetic evaluation in LAMBPLAN.

Using blup to estimate responses est a sheep flock selected for litter size

The reproductive performance of ewes is an important contributor to flock profitability in many different situations. Although the heritability of reproductive traits is low there is often enough phenotypic variance to make a consideration of selection a possibility for improvement in litter size. Genetic trends in selection experiments have traditionally been monitored using a control flock which should be kept as an unseletced group. The recent availability of user friedly BLUP programs have added an extra method for estimating genetic trends. This paper reports the use of BLUP to estimate the genetic trends in a sheep population selected for litter size.

Performance of three tropical hair sheep breeds

The performance of three hair sheep breeds (Brazilian Somali, Morada Nova, and Santa Ines) was evaluated in the production environment of northeastern Brazil. Data from a total of 524 lambs sired by 21 rams and out of 190 ewes were analyzed. These data were collected from 1980 to 1983 at Sobral, Brazil from an experiment designed to compare performance of the three breeds. The traits included weights of lambs at birth, weaning, 8 mo, 10 mo, and yearling ages and ewe characters of weight at lambing (EWT), total lamb weight born (LWB), total lamb weight weaned (LWW), and prolificacy rate (PR). Differences (P < .01) among breeds were found for all characters. The Brazilian Somali, the smallest and slowest-gaining breed, was less sensitive to yearly variation than were the other breeds. The Santa Ines, the largest and fastest-gaining breed, was superior in LWB and LWW per ewe lambing. Averaged over the 4-yr period, the Morada Nova had the highest PR (1.82), and the Brazilian Somali and Santa Ines had similar PR (1.39 and 1.31, respectively). Environmental effects on PR due to yearly rainfall quantity and distribution pattern influenced lamb growth up to weaning and ewe reproduction performance. Breed x year (P < .05) interaction effects on PR were largely attributable to the Somali breed's exhibiting higher PR than the Santa Ines and Morada Nova breeds during the relatively wet years of 1981 and 1982.