Feeding organic ewes, ewe body condition and production over the reproduction cycle. Sheep have different nutritional requirement over the production cycle depending on the stage they are going through. Needs for energy are high at the end of gestation (especially for ewes carrying multiple lambs) and at beginning of the lactation. Ewe body condition scoring is a tool for evaluation feeding status in farm.
In 2010–2012, field trial were carried out in three different sheep farm. On each of the organically farmed test farms (Farm A, B and C) rations were prepared and samples of feeds were analysed to check that they met nutritional requirements. Ewe’s body condition scores were measured at weaning, at tupping and at lambing and production data (ewe litter size, lamb birth weight and lamb 100 day weight) were obtained from the Estonian sheep recording database "Pässu".
During the free period between weaning and tupping, while at pasture, the ewes all improved their condition scores (0.93). It was estimated that the ewes consumed from 6–8 kg of forage per day. Most of the ewes at tupping had body condition scores between 3–4 (in farm A 91.2% of ewes; in farm B and in farm C respectively 97.8% and 94.1%). This shows that the pasture area and pasture quality was sufficient for maintenance. During gestation, on all of the test farms, the ewes were fed hay for the first four months. From the fourth month they were fed a mix of hay and silage (farm A, B) or hay and whole oats (farm C).
There was a mean loss in body condition score from lambing to tupping of 0.42, and on each farm were losses in condition. To cover the energy demands energy is mobilised from body tissue. Offering only forage during this period cannot support the nutritional demands of gestation. In farm C oats were also fed during this period, and the loss in condition score was less than on the other farms (0.35). The greatest loss was on the farm A (0.47). Adding silage to the ration can satisfy the protein demand. Our analyses has shown that the most problematic period for nutritional status on organic farms is the gestation period.
During the beginning of the suckling period ewes were kept inside in the barn and fed with the winter ration. The diet consisted of hay and silage (farm B) silage only (farm A) or a mix of hay and oats (farm C). There were moderate mean body condition losses on the test farms (0.27 points) in the suckling period, when more energy is needed for milk production. Feeding oats (0.3 kg per ewe per day) during the suckling period covered energy demand but not the protein demand. As there were so few thin ewes there was insufficient data on these for meaningful statistical analysis and therefore there were no clear relationships found with the ewe litter size. On farm A, ewes with a score below three had fewer lambs per lambing than ewes with a score of 3–4. The same tendency was seen for the total of all farms. There were no significant linear correlations between ewe body condition scores and litter size. This is because some may be too thin, some may be too fat and the litter size will decline. The ewes of a score of three and less were grouped and within this group there was a significant correlation between ewe body condition score at tupping on the ewe litter size (+ 0.21).
The influence of ewe body condition score (on tupping) on the lamb birth weight and 100 day body weight was analysed. There wasn’t a clear tendency with the ewe body condition score and lamb birth weight in ewes with body condition between 3–5, but ewes with body condition score less than 2.5 have lighter lambs on birth (single lambs 7% and multiple born 11.3% less compared with ewes scored 3).
However, it seems that a better birth weight of lambs was obtained from ewes with body condition score 3 at tupping rather than from ewes with scores 3.5 and between 4–5.
Also, the data showed that the weaker-fed ewes (body condition score ≤ 2.5 at mating) reared lambs with lower 100 days body weight.
There wasn’t a clear tendencies between well fed and overfed ewes (score 3–5) and their lambs body weight at 100 day in all three farms, as the trends were different in separate farms. However, on the average, it appeared that the optimal ewe body condition score was 3 and 3.5 at the tupping, because their lambs had higher growth rate than from ewes having body condition score 2.5 or 4–5.
Keywords: sheep feeding, rations for organic ewes, evaluation ewe body condition scores, lamb birth weight, lamb 100 day weight, ewe litter size.