The effects of ewe live weight and body condition score around mating on production from four sheep breeds in extensive grazing systems in Uruguay

Abstract

Ewe live iveights were recorded 4 weeks prior to mating, at the beginning of mating and 22 to 23 days later over a period of 3 years in a flock of some 300 breeding ewes comprising approximately equal numbers of Australian Merino, Ideal (Polwarth), Merilin and Corriedale breeds in a pastorally based grazing system in Uruguay. Multiple-bearing ewes were generally heavier than single-bearing ewes which in turn were heavier than ewes which did not conceive, these differences being greatest in 3-and 4-year-old ewes (i.e. in their second and third breeding seasons). Body condition scores of non-pregnant ewes were lower than those of pregnant ewes, particularly in the 3and 4-year-old age groups. Ewe live weights achieved prior to, during and at the end of the mating period and the body condition score achieved 4 weeks prior to mating all had significant influences on the number of lambs born (P < 0-01) but there were no significant effects of changes in either live weight or body condition over the 4 weeks prior to mating or during the mating period. The effect of body condition score over the range from 2-0 to 4-0 was to increase the proportions of single-and multiple-bearing ewes and to decrease the proportion of non-pregnant ewes such that the number of lambs born per ewe mated increased from 0-94 to 1-38. Fleece weights differed significantly between breeds, Corriedales having the heaviest fleeces and Merilins the lightest (4-26 and 3-22 kg respectively). Wool production was also significantly and positively affected by age (P < 0-01) and by ewe weight at mating (P < 0-01). The results demonstrate the importance of giving preferential nutritional treatment to younger ewes to ensure a satisfactory subsequent lambing performance and improved wool production.

Review of sheep body condition score in relation to production characteristics

“…Similarly, Romney and Kivircik ewes of BCS of 2.0 and 2.5, respectively, at breeding, were more likely to get pregnant than ewes of lower BCS (Kenyon et al 2004b;Yilmaz et al 2011). Analysing the same issue another way, pregnant ewes had a higher mean BCS than their non-pregnant counterparts in Kurdi (Esmailizadeh et al 2009) and in various breeds (Gonzalez et al 1997). In manipulative studies, Gunn & Doney (1979) reported that when Cheviot ewes were fed to maintain a set BCS, those ewes with a BCS of 3.0 had higher pregnancy rates at first mating than ewes with a BCS of 2.0.…”

“…Furthermore, BCS, in comparison with live weight, circumvents the issues of skeletal size between and within breeds and physiological state (i.e. pregnancy) and is not influenced by gut fill or the length and wetness of the fleece (Jefferies 1961;Adalsteinsson 1979;Russel 1984a, b;Gonzalez et al 1997;Esmailizadeh et al 2009). …”

Mineral elements in grasses growing in contrasting environmental conditions in southern Patagonia

“…Sampling dates were selected because they were prior to mating, a period considered key for the proper nutrition of animals as preparation for reproduction. It has been shown that nutrition during the weeks before mating has an important effect on ovulation and lambing rates (González et al 1997).…”

An exploration of direct and indirect drivers of herbivore reproductive performance in arid and semi arid rangelands by means of structural equation models

“…Several authors have shown an association between nutritional status and ovulation rates in sheep and red deer (Gonzalez et al, 1997;Gunn et al, 1969;Langvatn et al, 1996;Russel, 1971). Higher EVI during fall e winter, could be thus associated to better nutritional status of ewe at mating and thus higher probabilities of ovulation and conception.…”