Lamb Weaning Weight Research Articles

Factors affecting the length of productive life in U.S. Katahdin ewes.

The length of ewe productive life (LPL), defined as the number of days between the first and last lambing, is a key indicator of ewe longevity and is directly related to the sustainability of the sheep industry. Therefore, the primary objective of this study was to investigate systematic effects influencing LPL in Katahdin sheep. The LPL of 10,474 Katahdin ewes (69.5% with uncensored and 30.5% with right-censored observations) born between 1992 and 2021 in 58 flocks located across the United States were analyzed. The Kaplan-Meier (K-M) and Cox Proportional Hazard (Cox PH) methods were used to estimate survival probability. Four Cox PH models were evaluated. Model 1 included contemporary group (CG; flock-year-season of ewe birth) as a random effect and the ewe's dam's age (EDA), ewe's own birth-rearing type (BR; 1/1, 2/1, 2/2, 3/2, 3/3, with the digit-3 including lamb counts ≥3), and age at first lambing (AFL) as fixed effects. Models 2 to 4 were an extension of model 1. Model 2 also included average lamb birth weight (ABW) per ewe lifetime, while model 3 included average lamb weaning weight (AWW) per ewe lifetime. Both ABW and AWW were fitted as fixed effects. Model 4 fitted all previous effects together. The factors CG, BR, ABW, and AWW affected LPL (P < 0.05) in all models in which these effects were fitted. The EDA effect only influenced LPL (P < 0.05) in model 1, while AFL had no effect (P > 0.05) in any model. The median LPL ranged from approximately 2 to 3 yr, depending on the risk factors analyzed. In general, Katahdin ewes themselves born in multiple litters, and that produced lambs weighing ~5kg at lambing and 20 to 25kg at weaning (over their lifespan) had better survival probability. Although the LPL of Katahdin sheep is relatively low, it appears to be a consequence of voluntary culling due to its association with both ABW and AWW. Future studies should quantify the rate of involuntary culling in Katahdin ewes to identify whether longevity indicator traits should be included in more comprehensive breeding objectives.

Impacts of winter crop choice and ewe body condition score change on whole farm profitability and production

Variations in body condition score (BCS) in ewes influences lamb survival, ewe survival and ewe lactation performance. Feeding a low protein diet such as fodder beet to ewes in mid-to-late pregnancy increases lamb losses and reduces lamb weaning weight even further. However, using high yielding forages such as fodder beet can reduce the area of winter crop required, introducing potential whole-farm benefits which may alter profitability. We analysed the effects of winter crop choice (brassica or fodder beet) and BCS (maintaining or reducing) on whole-farm production and profitability, using a targeted supplement to offset the impacts of fodder beet feeding. Eight farms were selected to represent low or high rainfall (590 and 1090 mm/annum respectively) regions of the South Island. Impacts of changing BCS on ewe and lamb survival at lambing, and lamb liveweight gain to weaning were calculated when fed either adequate (brassica) or low protein (fodder beet) diets in mid-to-late pregnancy. Production statistics and profitability were calculated using Farmax. Whole farm profitability was analysed using BCS change and winter forage crop as main treatments, blocked by low or high rainfall. Applying the effects of BCS and low protein diets on reproductive performance from prior published studies resulted in variation of 102 to 141 lambs weaned per 100 ewes mated, with the lowest value when the low protein, fodder beet only diet was used. Greatest number of lambs weaned was achieved when BCS was maintained through winter through provision of a balanced supplement, regardless of winter forage diet (P&lt;0.05). Lamb sale dates were later when fodder beet was used, due to lower lamb weaning weights, resulting in marginally higher prices due to changes in pricing schedule. Farm profitability was increased by 25% when BCS was maintained though winter (P&lt;0.05) irrespective of the diet used. Use of fodder beet must be accompanied by targeted supplementation to avoid ewe BCS loss increased lamb losses and the negative effects on wastage and animal welfare. Extra profitability could only be generated by opportunities to sell surplus feed during the summer. These responses were similar in both high and low rainfall environments. This study is unique in testing measured responses of BCS and targeted nutritional supplementation under specific physiological conditions on whole-farm profitability. Farmer decisions on feed utilisation and sale also have a significant influence on the potential to mitigate the effects of variations in winter forage choice.

Negative energy balance affects perinatal ewe performance, rumen morphology, rumen flora structure, and placental function.

This study investigated the effects of negative energy balance (NEB) on perinatal ewes, with a focus on changes in growth performance, serum biochemical parameters, rumen fermentation, ruminal bacteria composition, placental phenotype-related indicators, and expression levels of genes related to placental function. Twenty ewes at 130 days of gestation were randomly allocated to either the positive energy balance (PEB) or NEB groups. In the experiment, ewes in the PEB group were fed the same amount as their intake during the pre-feeding baseline period, while ewes in the NEB group were restricted to 70% of their individual baseline feed intake. The experiment was conducted until 42 days postpartum, and five double-lamb ewes per group were selected for slaughter. The results demonstrated that NEB led to a significant decrease in body weight, carcass weight, and the birth and weaning weights of lambs (P < 0.05). Additionally, NEB caused alterations in serum biochemical parameters, such as increased non-esterified fatty acids and β-hydroxybutyrate levels and decreased cholesterol and albumin levels (P < 0.05). Rumen fermentation and epithelial parameters were also affected, with a reduction in the concentrations of acetic acid, butyric acid, total acid and a decrease in the length of the rumen papilla (P < 0.05). Moreover, NEB induced changes in the structure and composition of ruminal bacteria, with significant differences in α-diversity indices and rumen microbial community composition (P < 0.05). Gene expression in rumen papilla and ewe placenta was also affected, impacting genes associated with glucose and amino acid transport, proliferation, apoptosis, and angiogenesis (P < 0.05). These findings screened the key microbiota in the rumen of ewes following NEB and highlighted the critical genes associated with rumen function. Furthermore, this study revealed the impact of NEB on placental function in ewes, providing a foundation for investigating how nutrition in ewes influences reproductive performance. This research demonstrates how nutrition regulates reproductive performance by considering the combined perspectives of rumen microbiota and placental function.

Genetic parameters for ewe lifetime productivity traits in Central Anatolian Merino sheep

Rapidly increasing population size, recent breaks in production and supply chains, due to pandemics, and those further expected because of climate change emphasize the compelling importance of animal productivity. Traits associated with the productivity of ewes have a direct impact on the overall productivity, profitability and efficiency of sheep farms. Therefore, the objective of the current study was to estimate the variance components, heritabilities as well as genetic and phenotypic correlations, for traits associated with the lifetime productivity of Central Anatolian Merino ewes. Birth and weaning records of lambs for each ewe as well as environmental factors such as sex and birth type were utilized for deriving ewe lifetime productivity traits. Genetic parameter estimations involved observations from 3101 Central Anatolian Merino ewes, encompassing mean and total lamb birth weight per ewe (MBW and TBW), mean and total lamb weaning weight per ewe (MWW and TWW), and the mean and total number of lambs weaned (MNLW and TNLW). This analysis utilized a pedigree comprising 13229 animals. Average Information Restricted Maximum Likelihood (AIREML) based Animal Linear Mixed Model estimations for the decomposition of (co)variance components were implemented based on pedigree-derived numerator relationship matrix by also accounting for the number of parities as a fixed factor. Low to moderate heritability estimates, ranging between 0.29 and 0.42, were observed for the lifetime productivity traits of the breed. A wide range of genetic and phenotypic correlations (between −0.56 and 0.99) was observed among the traits of interest. The outcomes of the study are anticipated to significantly enhance the global sheep production systems by uncovering the essential parameters for incorporating ewe’s lifetime reproductive performance and productivity into the selection indices. This will also benefit Central Anatolian Merino farmers, who form a large proportion of sheep producers in Turkey.

Artificially reared ewes cannot be distinguished from natural reared ewes based on observed maternal behavior or lamb weaning weights.

Artificially rearing lambs is an important component of United States sheep production as some flocks select for increasing litter size to boost productivity. However, there is a conception among shepherds that artificially reared ewe lambs will ultimately result in poor mothers since they were not naturally raised. The objective of this study was to determine if differences in maternal behavior could be detected between ewes raised artificially and those raised naturally and if dam rearing type had an impact on lamb growth performance. Forty-eight ewes were enrolled comprised of 4 equal sized groups: artificially reared primiparous, naturally reared primiparous, artificially reared multi-parous, and naturally reared multi-parous. Ewes were observed using remote cameras to record maternal behaviors toward the lambs during and shortly after parturition. Behavior of 29 ewes during the first hour after parturition was analyzed. Independent multivariable regression models were evaluated for: proportion of time spent grooming, proportion of time spent helping the lambs nurse, number of helpful bouts, and the number of negative bouts. No statistically significant difference (P < 0.05) was detected between artificially reared and naturally reared ewes for the proportion of time spent grooming and the proportion of time spent helping the lambs nurse. Historical flock data were utilized to evaluate lamb growth between artificially and naturally reared ewes. No detrimental associations between artificially reared ewes and lamb weaning weights were observed. This study shows that artificially reared ewes are no different in terms of mothering behaviors and may be used as potential replacement candidates.

Production, reproduction, and some adaptation characteristics of Romanov sheep raised under humid temperate climate.

This study aimed to determine the fertility and growth traits, viability, and body measurements of the Romanov sheep under breeder conditions in the humid region of Turkey. The animal material of the research consisted of sheep imported from Ukraine in 2019. In the study, there are two farms with 31 and 44 ewes in the first year and three farms with 45, 34, and 32 ewes in the second year. The reproductive performances of 186 sheep and lambs in three different farms were examined, and nine rams, one ram per 20 sheep, were used for mating. Two-year (2020 and 2021) data on the reproductive performance of pure Romanov ewes, survivability in ewes and lambs, and development characteristics in lambs were used in the present study. The conceived rate (88.17%), fecundity at birth (1.42) and at weaning (1.29), litter size at birth (1.76) and weaning (1.56), single (50.98%), twin (41.83%), and triplet birth rate (6.54%), and abortion rate (6.71%) were determined for 2 years average. Birth and weaning weights of lambs were affected by sex and birth type (p < 0.01). The Romanov sheep and their lambs did not satisfy the breeder regarding reproductive performance and lamb development.

PSV-22 Productivity at Weaning of F1 Dorper X Pelibuey Ewes Carrying the Fecge Allele of the Ovine GDF9 Gene

Abstract The FecGE allele of the ovine GDF9 gene has been reported segregating in the Pelibuey hair type breed in México. Homozygous E/E ewes reproduce normally, in contrast to the sterility of homozygous ewes reported for other GDF9 variants. Thus, potential exists to cross homozygous and carrier Pelibuey ewes with meat type rams of low-prolificacy but well-adapted breeds to obtain F1 commercial flock ewes. The aim was to evaluate ewe productivity, as total lamb weight weaned (TWW), of FecGE carrier vs non-carrier F1 Dorper x Pelibuey ewes. Sixty one first lambing ewes (34 carrier and 27 non-carrier) equally served with two Texel rams were used. Management was under feedlot conditions. Genotyping was done by real time PCR (StepOnePlus) using the FAMACTTCAAACAGTTTCTTTTTMGBNFQ and VICTCAAACAGTGTCTTTTTMGBNFQ probes (Applied Biosystems). Type of birth (TB; twins vs single) and weaning (TW) were analyzed with PROC CATMOD of SAS. Fixed effects of ewe genotype (carrier vs non-carrier), contemporary group and ram of service were included in a logistic generalized linear model. Lamb weaning weights were adjusted to a common age of 75 d and by sex. Equivalent to male average birth lamb weight (ABW), average weaning lamb weight (AWW) and TWW per ewe were analyzed with PROC GLM of SAS. Carrier ewes had more twins (P &amp;lt; 0.01) for TB (75 vs 19.4 %) and TW (58.8 vs 21.7 %) than non-carrier ewes. Equivalent to male ABW on carrier ewes was less (P &amp;lt; 0.05; 3.17 ± 0.21 vs 3.97 ± 0.20 kg) than for non-carrier ewes but not difference (P &amp;gt; 0.05) was observed for AWW (21.96 ± 0.85 vs 22.93 ± 0.90 kg). Ewe productivity, as indicated by TWW, was greater (P &amp;lt; 0.05; 33.16 ± 1.78 vs 27.23 ± 1.88 kg) for FecGE carrier ewes than for the non-carrier ones. More research on this topic deserves further attention, especially under range conditions, with multiple parity ewes, different years and reproductive activity seasons, using a larger simple.

Characteristics of lambs and milk productivity of Tsigay breed ewes and F1 and F2 crosses with Assaf dairy sheep

This article presents data on the growth and development of lambs from birth until weaning, from their mothers of the Tsigay breed, as well as crossbreeds F1 ♀Tsigay X ♂Assaf, F2 ♀ Tsigay 25% X ♂Assaf 75%, and F3 ♀Tsigay 12.5% X ♂Assaf 87.5%. The measurements of udder size, udder volume, milk productivity for twenty days after lambing, fostering and milking periods, and overall lactation were recorded. Additionally, the average daily milk yield, milk composition, fat, and protein content in the milk were analyzed. The average weaning weight of F3 lambs from their mothers was 32.81±0.99 kg, F2 was 29.40±1.78 kg, which is 3.41 kg lower, and F1 was 28.56±1.11 kg, significantly lower (P ≤ 0.01) by 4.25 kg. In the first 20 days after lambing, the milk productivity of F2 ewes was 64.09±7.85 kg, higher compared to F1 ewes by 15.41 kg and by 27.87 kg (P ≤ 0.01) compared to purebred Tsigay ewes. The largest udder volume was found in F2 ewes, measuring 2275.20±257.90 cm3, which is 785 cm3 less than in F1 ewes and 943 cm3 less than in purebred Tsigay ewes. The difference between the two groups is statistically significant (P ≤ 0.05). Over 208 days of lactation, crossbred F2 ewes produced 268.38±33.67 kg of milk, which is 62 kg more than F1 ewes, who produced 206.00±26.86 kg in 207 days, and 126 kg more than purebred Țigay ewes, who produced 141.72±13.83 kg in 198 days. The difference is statistically significant (P ≤ 0.01). Regarding the chemical composition, there were slight differences between purebred Tsigay ewes and F1 ♀Tsigay X ♂Assaf crossbreeds, while the fat and protein percentages were the same (9.03 and 8.91, respectively). In F2 ♀ Tsigaiy25% X ♂Assaf 75%, fat, protein, and fat +protein content was higher.

Ewe udder and teat traits as potential selection criteria for improvement of Merino lamb survival and growth

Neonatal lamb mortality is a major economic and welfare issue for Australian sheep producers. The contribution of udder and teat traits of the dam to the survival and subsequent growth of the lamb is relatively unknown. This study aimed to estimate phenotypic and genetic parameters associated with objectively measured and visually scored udder and teat traits in Australian Merino sheep, and to evaluate the impacts of udder and teat traits of the dam on survival and growth of their lambs to weaning. Ewes from the New England Merino Lifetime Productivity flock (n = 1341 ewes) were assessed for udder and teat traits, and phenotypic and genetic parameters for individual traits and relationships among them were estimated using linear mixed models. Odds ratios were calculated to investigate the influence of udder soundness on lamb mortality. Further, the influence of udder traits on variation in lamb weaning weight was explored. Measured udder and teat size traits were estimated to have moderate to high heritabilities (0.32 (0.09) to 0.56 (0.10)), while the heritabilities of visually scored traits were lower (0.09 (0.05) to 0.17 (0.07)). Measured traits were highly correlated genetically with their equivalent visually scored traits. The odds ratio of mortality for lambs born to ewes with unsound versus sound udders was 1.54 (95 %CI 1.1–2.2, P < 0.05). The odds ratio of lamb mortality from starvation compared to all other causes of death for lambs born to ewes with unsound versus sound udders was 4.62 (95 %CI 2.4–8.9, P < 0.001). Dam udder and teat traits collectively contributed 8 % of the variation in lamb weaning weight observed. Results suggest that targeting optimal ewe udder and teat characteristics in sheep breeding programs has the potential to significantly improve lamb survival and growth in extensive production systems.

Bigger lambs or more lambs: The conundrum for New Zealand lamb producers

New Zealand sheep producers generate most of their income from sheep sales, particularly lamb sales. To increase revenue from lamb sales producers have two choices, increase the number of lambs weaned or increase the weight of lambs produced and sold. Lifting the number of lambs sold requires an increase in lambs born per ewe, however this comes at a cost as these lambs are typically smaller and may not reach optimal slaughter weight within the desired timeframe. Alternatively, increasing the weight of lambs, while maintaining total feed supply constant, means that the number of breeding ewes carried on the farm may have to be reduced. This study utilises an existing bioeconomic model to examine the impact on farm productivity and profitability of increasing lambing percentage from an average of 133.5% to 140, 150 or 160%, or increasing lamb weaning weight from 30 kg and 25 kg for singles and twins respectively, by 10, 20 or 30%, or alternatively a mix of the two, i.e., 140% lambing rate and weaning weights of 33 and 27.5 kg for singles and twins, respectively. The results show that lifting lamb weaning weight, by 10, 20 or 30%, increases enterprise cash operating surplus (COS) from $291/ha to $342, $392, or $444/ha, respectively, which is more than the increases in COS from lifting lambing percentage by 10, 20 or 30%, which increased COS to $313, $345, or $368/ha, respectively. The alternative of lifting lambing percentage by 10% and lamb weaning weight to 33 kg and 27.5 kg, increased COS by $74/ha. Overall, increasing pre-weaning lamb growth was more profitable than increasing lambing percentage. Therefore, if a producer has a lambing percentage of 140% or above their focus should be on improving pre-weaning lamb growth rates rather than lifting lambing percentage.

Application of Classification and Regression Tree (CRT) Method for Predicting the Some Environmental Factors Affecting Weaning Weight of Awassi Lamb

: In this study, the effects of some environmental factors on the weaning weights of Awassi lambs, raised within the scope of the Awassi sheep breed sub-project of the Ovine Breeding National Project in the Hands of the People Project under the coordination of the General Directorate of Agricultural Research and Policies affiliated to the Ministry of Agriculture and Forestry, were investigated. For this purpose, estimation was made with the regression decision tree (CRT) method, which is one of the machine learning algorithms. In the study, the effects of age of dam, gender, birth type and flock type (elite and base flock), which are thought to influence weaning weight in Awassi lambs, were considered independent variables, while weaning weight was considered as the dependent variable. According to the regression tree estimations, the most effective environmental factor on weaning weight of Awassi lambs was found to be the birth type. While the effective factor for singleton lambs was the gender, it was determined that the important factor for male lambs was the type of flock. Age of dam was found to be effective on the weaning weights of the lambs in the base flock.

Effects of lamb sex and ewe parity on suckling-related neonatal behaviors and weaning weight of small-tailed han lambs

Suckling behavior is essential for the growth, health, and welfare of the lamb. The factors that influence the suckling-related behavior varied across breeds, and they remain unclear in Small-tailed Han lamb. This study aims to investigate the effects of ewe parity, lamb sex, and birth order on the suckling-related behaviors of Small-tailed Han lamb. The neonatal behaviors of 36 lambs were observed during the first week after birth using focal-animal sampling methods, and the levels of cholecystokinin (CCK), endogenous opioid peptides and growth hormone (GH) were measured with ELISA methods before weaning. Results showed that male lambs began standing and suckling behaviors earlier than female lambs, and the duration of each suckling bout was longer in male lambs (P < 0.05). Lambs born to multiparous ewes more frequently suckled and attempted to stand earlier than lambs from primiparous ewes (P < 0.05). The weaning weights of male lambs and lambs from multiparous ewes were heavier, and the serum levels of CCK, opioid peptides, and GH were sometimes higher in these lambs before weaning (P < 0.05). Meanwhile, lamb birth order has no significant effect on the suckling-related behaviors of lambs (P > 0.05). In addition, the suckling-related behaviors of male lamb and lambs born to multiparous ewes were found to strongly correlate with each other. In conclusion, lamb sex and ewe parity could affect the suckling-related behaviors and weaning weights of Small-tailed Han lambs. Moreover, male lambs and lambs born to multiparous ewes seemed to have better suckling-related behaviors. Many of these behaviors were highly connected with one another. These phenomena may be related to the higher serum levels of CCK, opioid peptides, and GH. The effects of lamb sex on suckling-related behaviors were different from those of other breeds in previous research. The male lambs were observed to initiate sucking-related behaviors earlier in this study. Our findings will also help in extensively understanding the variability in the effects of these factors on suckling-related behavior across sheep breeds.

Produktivitas peternakan domba menggunakan sistem kawin alam di CV Gumukmas Multi Farm Kabupaten Jember

The study was conducted to determine the productivity of local ewes and crossings carried out in Purwoasri Village, Gumukmas District, Jember Regency. This study used 30 local and crossing sheep and 65 lambs. The method used is a survey method. The observation sample was determined by purposive sampling. The variables used were birth weight, weaning weight, and litter size. The data obtained in the form of parent productivity is presented in tabular form and analyzed descriptively. The results showed that the litter size (LS) of local ewes was 1.35 ± 0.49 and that of crossing ewes was 1.92 ± 0.25. The lamb interval for local ewes was 10.55 ± 1.24 and that of crossing ewes was 9.87 ± 0.88. The weaning weight of male local lambs was 12.5 ± 0.25 and for female local lambs was 11.8 ± 0.35, the weaning weight of male crossing lambs was 14.6 ± 0.51 and for female crossing lambs was 14 0.0 ± 0.15. The productivity of local ewes is 17.92 and crossing ewes is 20.53.

Colostrum Quality of Ewe Fed Flushing Diet Containing EPA and DHA Associated with Lamb Performance

This study evaluated the effect of a flushing diet containing docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) from lemuru fish oil in ewe ration on colostrum quality and lamb performance. Twenty Garut ewes were divided into four treatments of flushing concentrate: control concentrate (P1), flushing concentrate containing 6% palm oil (P2), flushing concentrate containing 3% lemuru oil and 3% palm oil (P3), flushing concentrate containing 6% lemuru oil (P4). The animal consumed Napier grass and concentrate with a diet ratio of 30%:70% based on dry matter. The experimental ewes were fed flushing rations two weeks before and two weeks after mating continued with 2 weeks before and two weeks after lambing. The ewes and their lambs were put together until weaning time with around two months. The parameters observed in ewes were nutrient consumption and their colostrum qualities. Meanwhile, the lamb parameters measured were nutrient consumption, lamb blood metabolites at birth, and lamb performance. The experimental design used a randomized blocked design (RBD). Analysis of variance (ANOVA) followed by Duncan test was used to analyze data. The results showed that treatment did not significantly affect dry matter consumption in ewe and lamb, ewe’s colostrum quality, and lamb’s blood metabolites. However, the treatment significantly improved (p<0.05) average daily gain and weaning weights of lambs. In conclusion, the flushing ration did not affect the quality of colostrum produced. Feeding of experimental ewes 2 weeks before and 2 weeks after mating continued with 2 weeks before and 2 weeks after parturition with flushing rations of 6% lemuru oil containing EPA and DHA can produce twin lambs with good growth performances such as daily gain and weaning weight similar to the control, which has single litter size.

Effect of Breeding Heavier Romney Ewe Lambs at Seven Months of Age on Lamb Production and Efficiency over Their First Three Breeding Seasons.

Simple SummaryThis experiment examined the impact of breeding heavier ewe lambs on lamb production and the ability of a ewe to produce a high number and heavier lambs (i.e., efficiency) over the first three breeding seasons. Two groups of ewe lambs were bred at seven months of age at an average live weight of either 47.9 ± 0.36 kg (n = 135) or 44.9 ± 0.49 kg (n = 135). Ewe live weight, number of lambs born and weaned, and lamb live weights were recorded, and ewe efficiency was calculated for each ewe. The weight and number of lambs at weaning over the three-year period did not differ between treatments, however, when data were pooled, heavier ewe lambs at breeding had a greater number and lamb weaning weight over the three-year period. Breeding heavier ewe lambs had no effect on ewe efficiency. There was a positive relationship between ewe lamb breeding live weight and their mature weight. These results suggest that breeding heavier ewe lambs increased the total lamb production over the three-year period, however, it had no effect on ewe efficiency. Before final recommendations can be made, ewe lifetime performance and longevity of heavier ewe lambs at breeding are required.This experiment examined the effect of breeding heavier ewe lambs on lamb production and their efficiency over their first three breeding seasons. Two groups of ewe lambs were bred at seven months of age at an average pre-breeding live weight of either 47.9 ± 0.36 kg (heavy; n = 135) or 44.9 ± 0.49 kg (control; n = 135). Ewe live weight, number of lambs born and weaned, and lamb live weight were recorded until 39 months of age, and efficiency was calculated for each ewe. Although the number and lamb weaning weight did not differ between treatments over three years, when data were pooled, heavier ewe lambs at breeding weaned a greater number of lambs over the three-year period. The total lamb weaning weight over the three-year period increased by 2% for each additional kilogram at ewe lamb breeding. Breeding heavier ewe lambs had no effect on efficiency. These results suggest that although breeding heavier ewe lambs had a positive effect on lamb production over the three-year period, it had no effect on efficiency. Before final recommendations can be made, lifetime performance and longevity to five years of age of heavier ewe lambs at breeding are required.

MAGRARIO: UN NUEVO GENOTIPO PARA PRODUCIR CARNE OVINA DE CALIDAD

Generally there is poor tradition to produce and to commercialize heavy lean lamb carcasses. To achieve a better product for the ovine meat market Ideal (Polwarth) breed ewes were backcrossed to Texel breed rams (breed recognized to reduce carcass fat). Ideal breed (I) is one of the most ordinary breeds in Argentina. However, when their lambs are reared in feed-lot conditions, a high fat content is found in their lamb carcasses. After three generations of backcrosses followed by a breeding program for increase male lamb weaning weight and female fertility a new genotype was obtained for the local ovine meat production systems. This new genotype registered as Magrario (M) was obtained at Villarino Field Station of UNR (Zavalla, Santa Fe, 33º S, 61º W). It was verify that M produced more lean meat than I breed under feet lot conditions. M rams were introduced in flocks of Hampshire Down (HD) breed to evaluate lamb crosses with lean meat. Genotype M was compared under feed lot conditions with HD lambs during two months in the post weaning. Also crosses (MxHD), (MxI) and (IxHD) were evaluated in the same conditions. At the end of the experiment ultrasonic methods were used to evaluate fat depot on Longissimus dorsi. The (MxHD) showed a reduction of 20% respecting to HD. These results suggested that M genotype could be a useful paternal genotype to reduce fat depots when the aim is to produce lamb crosses under feed lot conditions in a short period of time. Key words: ovine, lean meat, feed lot, crossing.

358 Effect of Molasses Type on Pre-weaning Lamb and Ewe Performance

Abstract The objective of this study was to investigate the effects of form of molasses on lamb and ewe performance. Creep feeding of lambs is essential to lamb growth, rumen development, and reduction of milk production from dams. Molasses is often added for increased palatability and energy. Crossbred lambs (n = 47; average age = 30 d) and their accompanying dams (n= 35) were assigned to one of two treatments using a completely randomized design with similar distributions of single and twin-born lambs and sexes. Treatment diets were formulated to be isonitrogenous and contained either wet (WMOL) or dry (DMOL) molasses. Dry molasses was added at 10% of the diet DM, whereas, wet molasses was added at 14.3% of the diet DM. Lambs were fed creep rations for 42 d prior to weaning. Creep feed was provided ad libitum and mixed grass hay was offered free-choice. Lamb weights were recorded weekly until weaning (d 42) and ewe BCS was measured at d 0 and d 42 (weaning). Overall lamb ADG was comparable (DMOL = 0.268 kg/hd, WMOL = 0.293 kg/hd; P = 0.30). Lamb weaning weights were similar between DMOL and WMOL (DMOL = 27.9 kg; WMOL = 27.5; P = 0.79). Ewe BCS was similar (P = 0.88) between DMOL and WMOL at 1.4 and 1.4, respectively. Estimated creep intake was calculated based upon total consumption following the end of the project and was found to be similar between treatments (DMOL = 0.54 kg/hd/d; WMOL = 0.59 kg/hd/d). Lamb pre-weaning growth and ewe performance was similar between DMOL and WMOL. Further research is needed to further explore the economic impact and use post-weaning.

The effect of behavioral reactivity on maternal behavior and offspring growth performance in Norduz ewes

The aim of this study was to determine the effect of behavioral reactivity on maternal behavior of ewes and early postnatal behavior and growth in lambs until weaning. The study was carried out with 100 multiparous Norduz ewes and 30 lambs. The study began by performing arena and scale tests and determining the test cortisol level in ewes during the anestrus period. Then, ewes were divided into two groups according to test reactivity as either “reactive” or “proactive” by using hierarchical cluster analysis. On the 50th day after mating, 15 reactive and 15 proactive gestating ewes of similar live weight, body condition and age (54.5 ± 0.58 kg, 3.19 ± 0.023 points and 4.07 ± 0.089 years, respectively) and carrying a single fetus each were selected and placed in one of two groups. Behavior of ewes and lambs from each group were monitored for a 3 -h period post-partum and the ewe-lamb separation test was performed within first 3 days postnatal. Ewes were phenotyped according to grooming duration, number of bleats, leaving lamb, preventing sucking etc., while lambs were phenotyped based on number of successful sucks, bleats, total suck duration, etc. Growth was determined by recording live weights of lambs at 2-week intervals until the 90th day. The whole trial lasted a total of 9 months. Ewes grazed entirely on rangeland with no extra feed supplementation. Ewes were fed with alfalfa hay and gradually supplemented with barley and concentrate during the winter. Serum cortisol levels were found significantly different in reactive and proactive ewes (1.57 ng/ml and 0.86 ng/mL, respectively; p < 0.001). During the early postnatal period, more high-pitched bleats were counted for proactive ewes, who also left their lambs alone more often than reactive ewes (p < 0.01), whereas reactive ewes had higher scores for following during ewe-lamb separation tests (p < 0.05). Lambs of reactive ewes had a higher total number of successful sucks, longer sucking duration (p < 0.05), and better growth performance at day 30 and day 45 (p < 0.05) as compared to lambs of proactive ewes. However, the weaning weights of reactive and proactive lambs were found similar as 30.3 ± 1.01 vs 30.2 ± 0.71 kg, respectively. In sum, the results of the present study indicated that some early postnatal ewe-lamb behaviours, ewe-lamb separation test score and lamb growth may be associated with behavioral reactivity. Given these findings, it was concluded that behavioral reactivity has potential use in efforts to improve maternal care and lamb welfare.

Utilising dual-purpose crops to produce prime lambs: comparison of White Dorper and Merino sheep on crops and pasture

Context Dual-purpose crops (for grazing and grain) are an important part of the feedbase in mixed farming systems in the medium-rainfall zone of southern Australia. On these farms, non-wool sheep breeds such as the Dorper may provide an opportunity to increase lamb production while reducing labour costs compared with traditional sheep breeds. Aims This study was designed to compare lamb production systems based on White Dorper and Merino ewes joined to a terminal sire, while exploiting a feedbase that included dual-purpose crops. Methods Two experiments were conducted at Wagga Wagga, New South Wales, during 2013 (Expt 1) and 2014 (Expt 2). In February in both experiments, White Dorper ewes were joined to either White Dorper or White Suffolk rams (lambs designated DD and WSD, respectively), and Merino ewes were joined to White Suffolk rams (lambs designated WSM). In Expt 1 a dual-purpose wheat (Triticum aestivum L.) crop was established and the paddock subdivided into nine plots (0.93 ha each). Pregnant ewes were allocated to plots on the basis of genotype (DD, WSD or WSM grazing separate plots) after blocking for number of fetuses identified at mid-pregnancy scanning, with three replicates based on genotype. Lambing commenced on 28 June, and ewes grazed the crop from 27 June to 14 August and then continued to graze in the same groups on a lucerne (Medicago sativa L.)–clover (Trifolium spp.) pasture subdivided into nine plots (2.1 ha), maintaining the same replicates until weaning on 2 October. In Expt 2, the cropping paddock was subdivided into six plots (1.86 ha each) sown to either dual-purpose wheat or canola (Brassica napus L.), with three replicates. Lambing commenced on 13 July. Merino and White Dorper ewes grazed the crops concurrently from 19 June to 12 August, and then lucerne–clover pasture until weaning on 29 September. In both experiments a mineral supplement was fed to ewes grazing wheat during the crop-grazing period. Key results Feed on offer was low (0.33 t/ha) in dual-purpose wheat crops at the start of grazing in Expt 1 and did not differ among genotypes at the cessation of grazing crops. Feed on offer was higher in wheat than canola at the commencement of grazing in Expt 2 (2.6 vs 2.3 t/ha; P = 0.009), and a higher stocking rate was maintained on wheat than canola from the start of lambing. White Dorper ewes maintained a higher body condition score than Merino ewes throughout both experiments. In Expt 2, some ewes had serum magnesium and calcium levels below the normal range, and a high number of ewes (20%) required assistance at lambing. Number of lambs weaned per ewe scanned pregnant was similar among genotypes in both experiments. WSD lambs were heaviest (P &lt; 0.05) at weaning and DD lambs had greatest (P &lt; 0.05) fat depth over the eye muscle at weaning. Conclusions and implications When grazed on a feedbase typical of mixed farms in the medium-rainfall zone of southern NSW, White Dorper ewes were in higher body condition than Merino ewes; however, reproductive rates were similar. Joining White Dorper ewes to a terminal sire may increase weaning weight of lambs compared with joining to a White Dorper ram, or a Merino maternal system.

142 Reproductive performance of land race hair sheep ewes in different breeding seasons under a semi-continuous production

Abstract A system for semi-continuous lamb production was evaluated using Barbados Blackbelly and St. Croix hair sheep ewes under 8-mo accelerated mating. Ewes were managed in a forage-based production system using rotational grazing. Two flocks of ewes (n = 30–35), equally representing the breeds, were bred 4 mo apart. Ewes were synchronized by feeding melengestrol acetate for 10 d, and mated in two single sire groups to like breed sires in November (NOV), March (MAR), and July (JUL) in a 25-d mating period. Pregnancy was recorded by transrectal ultrasound 22 d after breeding. Ewes were supplemented with corn/soybean meal during late gestation (0.75% of BW) and during lactation (1.5% of BW). They lambed on pasture with limited supervision, and lambs were weaned at 2 mo of age. Lambs had access to the supplement provided to ewes. Ewe performance (pregnancy rate, litter size, lamb survival, and birth and weaning weight) was recorded during a 2 yr production cycle, and analyzed for the effect of mating season. Pregnancy rate was not statistically different (P &amp;gt; 0.1) between season, and ranged from 93.9% in NOV, to 85.9 and 86.6% in MAR and JUL. Litter size (lambs born/ewe lambing) was higher (P &amp;lt; 0.05) in NOV (2.09) than MAR (1.68) and JUL (1.82). Lamb survival at birth was reduced (P &amp;lt; 0.001) in JUL (86.5%) compared to NOV (99%) and MAR (100 %), but was not different between seasons for survival to weaning (86 to 90%). Lamb birth weights were higher (P &amp;lt; 0.05) in MAR (3.16 kg) than JUL (2.99 kg), with NOV (3.05 kg) intermediate, while lamb weaning weights were higher (P &amp;lt; 0.001) in NOV (13.6 kg) compared with MAR (11.9 kg) and JUL (11.4 kg) mating. Data suggest that dual flock, accelerated mating of landrace hair sheep ewes can produce lamb cohorts of similar size in 4 mo intervals under a low-input, forage-based production system.