Lamb Weaning Research Articles

Tactical versus continuous stocking in perennial ryegrass-subterranean clover pastures grazed by sheep in south-western Victoria. 3. Herbage nutritive characteristics and animal production

A 4-year grazing experiment was carried out in south-western Victoria to compare the effect of tactical stocking with continuous stocking on the persistence of perennial ryegrass (Lolium perenne L.) and the productivity of sheep used for prime lamb production. Tactical stocking consisted of variable length summer, autumn and winter rotations and continuous stocking in spring. The 2 grazing strategies were compared on 2 contrasting pastures: an upgraded pasture, sown with newer cultivars of perennial ryegrass and subterranean clover (Trifolium subterraneum L.) with 26 kg phosphorus/ha.year, and a naturalised perennial ryegrass pasture receiving 6 kg phosphorus/ha.year. Paddocks were grazed by Border Leicester x Merino ewes, which were mated to a terminal sire to lamb in September. In this final paper of the series, the effects of the grazing systems and pasture treatments on animal production and herbage quality are presented. The liveweights of the ewes were similar across all treatments during autumn and winter, but the tactically stocked ewes were 3–6 kg lighter than continuously stocked ewes during spring and summer. The lower liveweight was attributed to the lower (P<0.001) herbage quality on the tactically stocked pastures in spring (P<0.001). Both digestibility and crude protein concentration were about 4 percentage units lower with tactical stocking in spring. This lower quality was associated with the higher herbage mass (by 500–900 kg dry matter/ha) on the tactically stocked pastures, which presumably had a higher stem:leaf ratio and showed reproductive growth earlier than the continuously stocked pastures. Although there were differences in ewe liveweight, this did not affect individual lamb weaning weight or ewe fleece weight. There were significant increases in production per hectare from tactically stocked or upgraded pasture treatments due to the higher stocking rates that could be carried, 9 and 51%, respectively. In 1998, 544 kilograms of lamb per hectare was weaned from continuously stocked paddocks and 607 kg/ha from tactically stocked paddocks (P<0.05), and 449 and 702 kg/ha from the typical and upgraded pastures, respectively. This study reinforces the view that soil fertility and pasture improvement have a much greater impact on animal productivity than changes to grazing method with little effect on per head productivity. The negative impact of rotational stocking on herbage quality reinforces the need to use these systems strategically when benefits from increased herbage mass are expected to increase animal production or overcome sustainability or pasture persistence problems.

The timing of nutritional restriction during reproduction influences staple strength

The staple strength of wool from Merino ewes (liveweight 41 kg; condition score 1.5) was assessed in response to a short-term nutritional restriction at different stages of pregnancy and lactation. Single- and twin-bearing ewes were fed to maintain maternal liveweight (control) or restricted to lose 2 kg in maternal liveweight between Days 85 and 98, 113 and 126, or 141 and 154 of pregnancy, or Days 169 and 182 in early lactation. Unmated control ewes were fed to maintenance, and a group of unmated ewes was restricted between the equivalent of Days 141 and 154 of pregnancy. All groups were maintained in group-feeding pens from Day 8 of pregnancy to 4 weeks after weaning of lambs. The ewes were fed lucerne hay. Control ewes fed to maintain liveweight produced sound wool (unmated 52.7, or single-rearing 46.0, and twin-rearing 43.0 N/ktex). Nutritional restriction only reduced the staple strength of wool produced by unmated ewes by 2.2 N/ktex (P > 0.05), but reduced that of reproducing ewes by 0–26.8 N/ktex. The decline in staple strength of reproducing ewes increased as the time of restriction during pregnancy advanced. Restriction during lactation did not significantly (P > 0.05) influence staple strength. The effect of restriction appeared to be mediated via changes in diameter along fibres. The results indicate that there is variation in the sensitivity of staple strength to short-term nutritional restriction, with both pregnancy status and the stage of pregnancy at which the restriction is imposed influencing the impact on staple strength.

The effect of weaning weight on subsequent lamb growth rates

The effect of weaning weight on the subsequent growth rate of lambs was estimated from data collected at Winchmore Research Station. The lamb weight data were collected over a 3-year period involving dryland and irrigated farmlets with two contrasting forage systems. Lambs were weighed at 2-weekly intervals with the weights for the periods immediately pre- and post-weaning being used for the comparisons in this study. Results overall indicated that, following adjustments for pasture type, gender, birth and rearing rank, heavier lambs at weaning had faster growth rates post-weaning than lighter lambs. However, lighter lambs suffered a lower drop in growth rate (defined as growth rate before weaning minus growth rate post-weaning) than heavier lambs. This was universal across both pasture types, both genders and all combinations of birth and rearing ranks. Possible explanations are that the lighter lambs at weaning were receiving less milk from their mothers or that they were under some mob pressure and had limited access to quality pastures. In some cases, the lighter lambs even increased their growth rates post-weaning when compared to pre-weaning. It is suggested that weaning light lambs is an option for farmers, particularly when feed supply is limiting or when dry stock are required to clean up poor quality pastures and set up high quality feed for young stock. Keywords: dryland, irrigated, lamb growth, lamb weaning, pasture quality, weaning weights

Increasing lamb output by crossing commercial Merino ewes with South African Meat Merino rams

Commercial Merino ewes were randomly allocated to 1 of 2 groups, which were joined either to commercial Merino or South African Meat Merino rams during October 1996 and 1997. Merino rams were involved in 161 joinings, and South African Meat Merino rams in 157 joinings. The proportions of ewes that lambed were independent of the breed of the sire when expressed relative to the number of ewes joined (0.809 and 0.801 in ewes joined to South African Meat Merino and Merino rams, respectively). The proportion of multiple lambs was similarly not affected by the breed of the service sire. Lambs sired by South African Meat Merino rams were on average ( s.e.) heavier (4.17 0.07 v. 3.86 0.07 kg; P<0.01) at birth. They also tended to have a better (0.69 v. 0.59; P<0.10) survival to weaning, and were heavier (26.9 0.6 v. 22.8 0.6 kg; P<0.01) at weaning than purebred Merino contemporaries. The combined effect of the tendency towards an improved survival rate as well as the increased lamb weaning weight resulted in a 36% increase (P<0.01) in lamb output in Merino ewes joined to South African Meat Merino ewes compared with ewes joined to Merino rams. Higher (P<0.01) proportions of ram lambs sired by South African Meat Merino rams reached slaughter weight (about 40 kg) before the onset of the dry Mediterranean summer than purebred Merinos. Two-tooth ewes sired by South African Meat Merino rams were heavier (P<0.01) at 2-tooth age (53.0 0.6 v. 52.0 0.6 kg) than purebred Merinos. The 2-tooth greasy fleece weight of South African Meat Merino sired 2-tooth ewes were lower (3.85 0.08 v. 4.66 0.09 kg; P<0.01), with a lower (66.8 0.6 v. 70.5 0.7 %; P<0.01) clean yield than that of purebred Merinos. This resulted in a marked difference in clean fleece weight between the 2 types (2.56 0.06 v. 3.28 0.06 kg, respectively). Wool produced by South African Meat Merino sired 2-tooth ewes was generally broader (21.8 0.3 v. 20.3 0.3 m; P<0.01) and shorter (87.3 1.3 v. 96.4 1.4 mm; P<0.01) than that of their purebred Merino contemporaries. The coefficient of variation of fibre diameter as well as staple strength was independent of the breed of the sire. Liveweight of adult ewes and wool traits were independent of the breed of the service sire.

Lamb and milk production traits of Serrai sheep in Greece

This study is based on data from 1238 lambings, 1516 lambs and 979 lactation records from Serrai ewes. Litter size averaged 1.25 lambs at birth, 1.23 lambs born alive and 1.17 lambs at weaning. Lambs weighed 4.3 kg at birth and 13.5 kg at weaning (42 days). Milk production averaged 70.7 kg in a lactation length of 157 days. Month of lambing influenced litter size, lamb birth and weaning weight, milk yield and lactation length ( P < 0.05). Lactation number influenced litter size, lamb weaning weight, milk yield and lactation length ( P < 0.05). There was a significant effect of litter size on lamb weight at birth and weaning and on milk production. The ewe weight at lambing had a significant effect on weights of lambs at birth and weaning and on milk production.

Psychobiological consequences of two different weaning methods in sheep.

Weaning is associated with a break in the mother-infant contact. In sheep, under natural conditions, the rupture of the social bond is progressive. In contrast, weaning imposed by breeders may result in psychobiological disturbances. The aim of this experiment was to measure the behavioural, hormonal and immune consequences of two types of sudden weaning: total separation (TS) and partial separation (PS), in 42 Ile-de-France ewes and their 60 lambs. TS animals (lambs and ewes) vocalized less frequently and for a shorter period of time than did the PS animals. Neither the plasmatic cortisol level in lambs nor the humoral response of dams and young were modified by the two weaning methods. In contrast, the excretion of coccidial oocysts increased significantly after weaning in TS lambs only and the growth rate of TS females was lower than that of the other lambs. These results suggest that these methods of rupture of mother-young social contact have only limited negative consequences on both partners in sheep, contrary to primates and rodents.

クリープフィーディングが子羊の反すう胃の発達に及ぼす影響

The effects of creep feeding on the growth of body weight and the development of ruminoreticulum were investigated during 3 months of nursing period.Eight Suffolk ewes and their lambs (two single born lambs and six twins) were used for this study. Three twins were fed creep feed from 2 weeks of age. The data for ram lambs only were used for this study.Ewes and their lambs were kept in pen of 4-5 m2 each. Ewes were fed at 8 : 30 and 17 : 00. Creep feed for lambs was given once a day in the adjoining pen. The residues of creep feed was measured at the next feeding. Body weight of ewes and lambs were measured once a week. After the weaning at 3 months of age, lambs were slaughtered, then the weight of ruminoreticulum, omasum and abomasum was measured, and the length of papillae was measured. Difference between means were tested for significance by two sample t-test. The twin lambs fed creep feed showed satisfactory growth until weaning. However, the growth rate of the other lambs decreased after 7-8 weeks of age. The mean body weight at weaning and the daily gain from birth until weaning of the twin lambs fed creep feed were 1.48 times and 1.53 times bigger than the means of the other twins, respectively (P < 0.05). In the case of the single born lambs, those means were intermediate values between the means of the twin lambs fed creep feed and the other twins.The mean weight of ruminoreticulum, omasum and abomasum of the twin lambs fed creep feed were 1.54 times, 1.60 times and 1.54 times bigger than the means of the other twins, respectively (P< 0.05). In the case of the single born lambs, those means were intermediate values between the means of the twin lambs fed creep feed and the other twins.The ratio of the weight of ruminoreticulum to the body weight, the metabolic body size and the weight of abomasum at weaning did not show significant difference between the values of the twin lambs fed creep feed and the values of the other lambs. These results showed that ruminoreticulum, omasum and abomasum were developed simultaneously with the increase of body weight by creep feeding.The twin lambs fed creep feed showed higher development of papillae than the other lambs (P< 0.05).

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.

Effects of complementary grazing by goats on sward composition and on sheep performance managed during lactation in perennial ryegrass and white clover pastures

The liveweight (LW) response of Gallega and Lacha ewes with their single suckling lambs when grazing with a mob of goats on perennial ryegrass ( Lolium perenne L.)/white clover ( Trifolium repens L.) pastures and its consequence on sward composition were analysed. From early March (turnout) to mid-June (lamb weaning), swards were grazed either simultaneously mixed in a 1:1 goat to sheep ratio or separately in a goat-first and sheep-last sequential grazing at 6 or 8 cm sward heights or in a 4-paddock rotation where goats grazed swards from 9 to 7 cm followed by sheep from 7 to 4 cm. Changes in botanical composition and in sheep liveweight performance were more significantly affected by the management and species grazing than by the sward height treatment. Swards where goats were last in had higher herbage masses, higher live clover and lower dead and stem proportions than swards where sheep and goats were mixed or sheep were last in. As a consequence of a sward clover enhancement over all treatments, ewe and lamb performances were benefited especially in the Lacha genotype, with the rotational and sequential managements having, respectively, an output of 298 and 252 kg LW/ha greater than the mixed management. These results suggest that goats could be used as a pasture management tool when integrated with sheep under these different grazing systems to enhance ovine performance during lactation.

The rôle of cortisol and β-endorphin in the response of the immune system to weaning in lambs

AbstractThe relationship between weaning stress-induced changes in stress hormone profiles and immune function was investigated in groups of 10 lambs immunized against adrenocorticotrophic hormone (ACTH; treatment A) or fi-endorphin (treatment B) to reduce the circulating concentrations of cortisol and fi-endorphin respectively. Control animals (treatment C) were immunized against a porcine thyroglobulin carrier protein. Application of weaning stress was associated with significantly elevated plasma cortisol concentrations but no significant increase in fi-endorphin concentrations in C lambs. Immunization against ACTH suppressed the post-weaning increase in cortisol concentration. This was associated with a transient reduction in the lymphocyte stimulation response to keyhole limpet haemocyanin (KLH) antigen in the A animals but there was no effect on the antibody response or interferon-y production by antigen stimulated lymphocytes. There were no significant effects of immunization against fi-endorphin on the capacity to mount antibody or cell-mediated immune responses. It is concluded that weaning stress-induced increases in cortisol did not inhibit the immune response. Since cortisol concentrations and the cell mediated immune response at 8 days after immunization were positively associated it is concluded that these indices are not independent measures of stress.

Comparison of Lohi and crossbred ewes: productive and reproductive traits

Data from 6305 lambings of Lohi, 7/8 Lohi: 1/8 Awassi (LA) and 7/8 Lohi: 1/8 Kachhi (LK) ewes from 1981 through 1993 were used to analyse growth and reproductive traits and wool production. Mean litter size at birth ranged from 1.37 for Lohi ewes to 1.41 for LA ewes and corresponding values at weaning were 1.32 and 1.30, respectively. Litter size varied among ewe age and season of lambing ( P<0.01). Litter size was consistently lowest for one-year-old, with a substantial increase at two, three and four years of ewe age and marginal increase thereafter. Ewes lambing in spring weaned 0.10 more lambs than ewes lambing in autumn ( P<0.01). Lamb birth weights were affected by ewe genotype ( P<0.01) and increased with ewe age. Mean lamb weaning weight (120 d) of 5587 lambs was 22.1 kg, which was affected by genotype, sire, year of birth, sex, litter size and weaning age ( P<0.01). Lambs from LK ewes were heaviest at weaning (23.0 kg) followed by lambs from LA ewes (22.9 kg) and Lohi ewes (20.5 kg). Lambs from crossbred ewes were 5% heavier at birth and 12% heavier at weaning than pure Lohi lambs. Twin-born lambs were 18% lighter at birth and 17% at weaning than single-born lambs. Male lambs were 7% heavier at birth and 14% heavier at weaning than female lambs. Lohi ewes produced 3% more wool than crossbred ewes. Crossbred ewes were superior to pure Lohi ewes by 2% in litter size at birth, 5% for lamb birth weight and 12% for lamb weaning weight. Heterozygosity among the crossbred ewes has resulted in improved productivity over purebred Lohi ewes.

Responses to various selection protocols for lamb production in Rambouillet, Targhee, Columbia, and Polypay sheep.

To investigate the effectiveness of four selection protocols for improving reproduction in sheep, we evaluated nine selection lines and two random-bred control lines for lamb and wool production. Results were based on 25,026 dam and 30,628 lamb records from Rambouillet (R), Targhee (T), Columbia (C), and Polypay (P) sheep collected from 1976 through 1988. Phenotypic trends over years were positive (P < .01) for most reproductive traits, body weight, wool grade (coarser grades), and lamb weaning weight in nearly all selected lines. Small positive trends for both random-bred control lines indicated there were improvements in management and(or) environment during the period. Small but significant phenotypic declines in fleece weights occurred in most lines, including controls. Substantial genetic gains (P < .01) in litter weight weaned (120 d), net reproductive rate (lambs weaned divided by ewes mated), prolificacy, body weight, and weaning weight were made in nearly all selected lines. There were also small but significant improvements in milk score in most lines. There were significant genetic declines and improvements in fleece weights; however, the average genetic change in fleece weight for lines selected for litter weight weaned was negligible. Genetic improvement in litter weight weaned was attributed approximately 37% to prolificacy, 27% to percentage of lambs weaned, 17% to lamb weaning weight, 12% to fertility, and 7% to ewe viability from breeding to lambing. On average, selection based on independent culling levels (litter weight weaned plus yearling body weight), yearling body weight, or early puberty was only 85, 67, or 59%, respectively, as effective as that based solely on litter weight weaned for improving litter weight weaned. The net value of the average (over all breeds) annual increase in production per ewe resulting from selection for litter weight weaned accumulated over 12 yr to an estimated $11.40 and $21.51 annually for genetic and phenotypic increases, respectively.

Lamb survival in relation to lambing and neonatal behaviour in medium wool Merino lines divergently selected for multiple rearing ability

Summary. Two lines of Merino sheep were divergently selected from the same base population since 1986 on maternal ranking values for multiple rearing ability. In the high (H) line, ewe and ram progeny were preferably descended from ewes that reared &gt;1 lamb per joining. In the low (L) line, replacements were the progeny of ewes that reared &lt;1 lamb per joining. Data on lamb mortality, lambing and neonatal behaviour as well as lamb production were obtained from these lines over 5 years (1993–97). Lamb survival was improved (P&lt;0.01) in the H line, mainly as a result of the improved survival of multiples. It was evident that the survival of lambs was not compromised by selection for ewe multiple rearing ability, despite the fact that higher mortality levels are expected with an increase in multiple birth rate. No line difference was found for the time lapse from birth to first standing for &gt;10 s, but H line lambs were quicker (P&lt;0.01) to progress from standing to suckling than L line contemporaries (28 v. 38 min respectively). This line difference remained after adjustment for better co-operation of H line ewes with the first suckling attempts of their progeny. Ewes in the H line tended (P = 0.18) to remain longer on or near their birth sites than L line contemporaries (403 v. 362 min respectively). They also tended to be less (P = 0.07) likely to desert their lambs than L line ewes (12/424 = 0.028 v. 14/230 = 0.061 respectively). After least-squares adjustment for their heavier (P&lt;0.01) litter weight, H line ewes experienced shorter (P&lt;0.05) births than their L line contemporaries (46 v. 57 min respectively). Fewer (P&lt;0.05) H line lambs died during or shortly after parturition (respective proportions of 22/890 = 0.025 and 25/441 = 0.057), while maiden H line ewes were less (P&lt;0.05) likely to be assisted at lambing than L line contemporaries (4/107 = 0.037 v. 8/61 = 0.131 respectively). With regard to overall lamb production, it was found that the number of lambs weaned per ewe present at lambing in the H line was improved (P&lt;0.05) in all years relative to that observed in the L line, the differences ranging from 25% in 1993 to 47% in 1997. Lamb weaning weight was correspondingly improved (P&lt;0.05) in H line lambs, the differences ranging from 8% in 1994 to 22% in 1996. Fairly high levels of production could thus be attained with predominantly pasture-fed ewes selected for multiple rearing ability.

A long-term study of superphosphate and stocking rate on sheep production and plant and soil characteristics in central west New South Wales

Summary. The effect of 4 rates of superphosphate application (250 kg/ha. year, 125 kg/ha. year, 125 kg/ha every 2 years or 125 kg/ha every 4 years) and a low and high stocking rate (3.6 and 5.4 ewes/ha, 1980–86; and 4.0 and 7.0 ewes/ha, 1986–89) on sheep liveweight, fleece weight, lamb weaning weight, pasture production and botanical composition, soil pH, soil phosphorus, manganese and aluminium concentrations were measured on a Phalaris aquatica–subterranean clover pasture at Stuart Town, New South Wales. Only when 250 kg/ha of superphosphate had been applied annually was there a higher level of soil phosphorus than with the other 3 systems. None of the treatments affected soil pH, soil manganese or aluminium. There were large year effects and individual plot effects on pasture and sheep production but neither the superphosphate rates nor stocking rate significantly affected pasture or animal production. It was concluded that over a 9-year period the application of 125 kg/ha in alternate years can maintain adequate soil phosphorus levels, and satisfactory pasture and animal production on the central tablelands of New South Wales.

Pasture management to minimise the detrimental effects of pre‐lamb shearing

The purpose of this study was to examine whether the performance of pre‐lamb shorn sheep is influenced by pasture allowance in the immediate post‐shearing period and whether the relationship between performance and pasture allowance differs according to whether the ewes are shorn by standard comb or cover comb. The trial was replicated across two years to allow for climatic variations between years. Fifty‐four ewes were used in each year in a 3 × 3 × 2 factorial design with three shearing treatments (standard comb, cover comb, and unshorn), three sward surface height (SSH) treatments (nominal 3, 5, and 7 cm), and two pregnancy status treatments (single and twin). Rectal temperatures of standard comb or cover comb ewes were significantly lower (P < 0.05) than those of unshorn ewes on day 2 following shearing (S2), and on S4, S8, and S20. Pasture allowance, however, did not affect rectal temperatures of shorn ewes. There was an interaction (P < 0.05) between shearing treatment and SSH. Thus, liveweight gains during the period from pregnancy day 115 (P115) to P135 were 275, 613, and 4518 g; 1557, 2314, and 3997 g; and 3623, 2894, and 3997 g for standard comb, cover comb, and unshorn (control) ewes set‐stocked on 3, 5, and 7 cm SSH, respectively. There was no interaction between shearing treatment and SSH for lamb birth weight, but the birth weights of lambs born to standard comb ewes (4.9 ± 0.1 kg) were significantly greater (P < 0.05) than those of lambs born to unshorn ewes (4.3 ±0.1 kg). There were no effects of shearing treatment or SSH on lamb weaning weight, ewe wool growth rate or mean fibre diameter. Likewise, there were no effects of shearing treatment or SSH on ewe organic matter intake (OMI), except on the second day following shearing when the OMIs of ewes set‐stocked on 3 cm (941 ± 147 g) were significantly (P < 0.05) lower than those of ewes grazing 5 cm (1628 ±101 g) or 7 cm (1349 ± 135 g) SSH pasture. The results suggest that hypothermia, as determined by rectal temperatures and induced by pre‐lamb shearing, cannot be avoided by pasture management, provided SSH exceeds 3 cm. This reflects the fact that, in the period immediately after shearing, ewes do not increase feed intake when provided with increased pasture allowances.

Effect of ewe ovine lentivirus infection on ewe and lamb productivity

We used a previously described sensitive and specific ovine lentivirus (OLV) recombinant transmembrane (rTM) protein enzyme-linked immunosorbent assay (ELISA) to detect anti-OLV antibodies and define OLV infection in breeding ewes from nine US Meat Animal Research Center (MARC) flocks. We estimated the production impacts of dam rTM ELISA seropositivity on ewe and lamb productivity in the birth-to-weaning interval using production data from 1466 breeding ewes (of which 1242 actually lambed) and their 2452 lambs born in spring 1992 using several multiple linear and logistic regression models. By adjusting for lamb weaning age, gender, type of birth and rearing, birth difficulty, dam age, and flock, the component of ewe or lamb productivity related to ewe OLV infection alone was isolated. The rTM ELISA-negative ewes produced significantly more total weight of weaned lamb per ewe-lambing (3.84 kg) and per ewe ram-exposed (4.95 kg) compared to their OLV-positive flockmates. Negative ewes also weaned 0.11 more lambs per ewe-lambing and 0.09 more lambs per ewe ram-exposed, gave birth to 0.13 more lambs per ewe ram-exposed, and were more likely to lamb after breeding (odds ratio (OR) = 1.9) compared to equivalent OLV-positive ewes. Lambs reared by OLV-negative ewes weighed 0.15 kg more at birth, gained 8 g more per day through weaning, and weighed 0.59 kg more at 56-day weaning. Preweaning mortality was lower (OR = 0.8) among lambs born to OLV-negative compared to OLV-positive ewes, although this difference was not significant. Our results suggest that subclinical OLV infection has important detrimental effects on sheep production which occur in cumulative fashion from breeding through weaning and that OLV control efforts may be financially justified in some sheep flocks.

Lamb growth and milk production of hair and wool sheep in a semi-arid tropical environment

St. Croix White hair ( n = 11), Barbados Blackbelly hair ( n = 10) and Florida Native wool ( n = 9) ewes were used to evaluate milk production and lamb growth under semi-arid tropical conditions. Milk production was measured on day 3 after lambing and at weekly intervals beginning on day 7 through weaning on day 63. Milk production decreased over time in St. Croix White and Barbados Blackbelly ewes more rapidly than in Florida Native ewes ( P < 0.01). Total milk yield was not different ( P > 0.1) among Barbados Blackbelly, Florida Native and St. Croix White ewes, or between ewes raising single or twin lambs. Udder volume was largest ( P < 0.08) in St. Croix White ewes, smallest in Florida Native and intermediate in Barbados Blackbelly ewes. All ewes had similar patterns of weight change during the study, but Barbados Blackbelly ewes weighed less than either St. Croix White or Florida Native ewes ( P < 0.05). There was no difference ( P > 0.1) in lamb weaning weight or average daily gain among the three breeds. The results show that Barbados Blackbelly, Florida Native and St. Croix White breeds of sheep produce similar amounts of milk and wean similar size lambs under tropical conditions, even though there are breed differences in body and udder size.

Produção de carne em ovinos de cinco genótipos: 1. Crescimento e desenvolvimento

O trabalho foi realizado no Centro de Pesquisa de Pecuária dos Campos Sulbrasileiros - CPPSUL - EMBRAPA de Bagé, RS, nos anos de 1994/95, com cordeiros das raças Texel, Romney Marsh, Corriedale, Ideal e Merino nascidos e criados até o desmame (10 semanas) em campo nativo, (predominância de Paspalum notatum Flügge e Axonopus affïnis Chase). Objetivou estudar aspectos relativos ao crescimento e desenvolvimento, com suplementação alimentar a campo, até o abate aos 7,5 meses de idade. A partir do desmame, iniciou-se a suplementaçào dos cordeiros (10 por raça, recebendo 200 g/cab./dia) com uma ração contendo 17% de PB e 75% de NDT. Até uma semana pós-desmame a ração foi oferecida em regime de confinamento e. após, a campo até o abate. Os resultados mostraram que os pesos ao nascer foram semelhantes (P&gt;0,05), porém, do desmame e a partir deste, o crescimento ponderal e o desenvolvimento de cordeiros Texel e Romney Marsh foram sempre superiores aos de Corriedale, Ideal e Merino. Após o desmame, principalmente nos primeiros 45 dias, a capacidade de conversão dos alimentos (suplemento + pasto) foi maior nas raças Texel, Romney Marsh e Ideal. Em todos os genótipos, observou-se que as variações de peso corporal (em relação ao tempo), após os 5,5 meses de idade, pouco contribuíram no peso final de abate.

Yield, composition and certain physicochemical characteristics of milk of the Epirus mountain sheep breed

This work deals with the production properties of a local Greek sheep breed which is extensively kept. Milk yield and composition, as well as certain physicochemical characteristics of the milk, were measured from the 7th week (lamb weaning) to the 37th week (end of lactation) using 352 ewes of the Epirus mountain breed. The average yield per ewe was 92 ± 2.4 (SE) kg, and the length of the milking period was 217 days. The average milk yield per day was 424 ± 11 g. The mean fat content of the milk was 7.85 ± 0.05%, the mean protein content was 6.56 ± 0.036%, the mean lactose content was 4.77 ± 0.009% and the mean non-fat solids content was 12.13 ± 0.033%. The average values for physicochemical characteristics were: acidity, 22.50 ± 0.085 °Dornic; specific gravity, 1.0372 ± 7 × 10 −5. The week and month of lactation had an effect ( P < 0.05) on all the milk variables studied. Correlations between the milk variables are reported. During double-milking periods the evening milk was richer in fat than the morning milk ( P < 0.05), whereas no significant difference was noted for the other milk components. This work shows that the Epirus breed of mountain sheep produces milk of high fat and protein content, which is important for the cheese manufacturing industry.

Supplementation of high fecundity Border Leicester x Merino ewes with a high protein feed: its effect on lamb survival

Two hundred and fifty Border Leicester x Merino ewes (40% heterozygous for the Booroola Fec B gene) were used in an experiment, replicated over 2 years, to examine the effects of cottonseed meal-based supplementation on lamb survival, birth, marking and weaning weight, as well as, liveweight and fleece characteristics of ewes. From 50 to 100 days of pregnancy, half of the ewes were supplemented with 80 g/head.day. The supplemented group was then split according to litter size and, until 30 days after lambing, were offered pellets at 80, 160 and 220 g/head .day, respectively, for ewes bearing single, twin and triplet (or more) lambs. Over the 2 years, ewes averaged 2.11 lambs per parturition and supplementation significantly increased lamb survival to weaning (73 v. 58%) with no interaction with litter size. Although supplementation had a positive effect on birth weight of all but twins, the effects of supplementation on survival were independent of birth weight effects. Significant effects of year, sire breed and litter size on lamb survival and birth weight were also noted. No effects of supplementation were apparent on lamb growth while ewe age, sire breed, sex and rearing rank all significantly influenced growth rates. Ewe weights, fleece weights and staple strength were significantly influenced by year, ewe age and litter size but not by supplementation. These findings indicate the benefits to lamb survival of providing a 'bypass' protein supplement to high fecundity flocks even when ewes are grazing good quality pastures.