Time filter

Source Type

Gulliver C.E.,Charles Sturt University | Gulliver C.E.,Co operative Research Center for Future Farm Industries | Friend M.A.,Charles Sturt University | Friend M.A.,Co operative Research Center for Future Farm Industries | And 4 more authors.
Animal Reproduction Science | Year: 2012

The positive effects of fat and energy supplementation on improvements in reproduction are well documented. However, the specific effects of omega-3 polyunsaturated fatty acids (n-3) on reproductive success in ruminants have not been examined in detail. While the link between n-3 and markers associated with reproduction, in particular, prostaglandin F 2α (PGF 2α) and the link between PGF 2α and reproductive outcomes are well established, evidence of a direct effect of high n-3 diets on measurable reproductive outcomes in ruminants is lacking. Therefore, the aim of the current review was to examine the effect of n-3 on a number of reproductive markers and measurable outcomes in sheep and cattle. There is strong evidence linking consumption of diets high in n-3 with reduced circulating peripheral inflammatory markers such as PGF 2α. Inflammatory eicosanoids including PGF 2α, in particular, can significantly affect reproduction outcomes such as the onset of oestrus, embryo survival and parturition. While there is also evidence linking n-3 supplementation with longer time to oestrus and parturition associated with reduced PGF 2α, the effects of n-3 on other measurable outcomes of reproductive success, such as pregnancy rate, embryo survival and intergenerational effects on the health and production of offspring are largely unknown. Similarly, the effects of diets high in n-3 or n-6 polyunsaturated fatty acids on male fertility are also unknown. © 2012 Elsevier B.V.

King B.J.,Charles Sturt University | King B.J.,Co operative Research Center for Future Farm Industries | Robertson S.M.,Charles Sturt University | Robertson S.M.,Co operative Research Center for Future Farm Industries | And 3 more authors.
Animal Reproduction Science | Year: 2010

This study evaluated the ability of short-term grazing of live=green pasture to increase ovulation rate during late summer when annual pasture is generally dead and of low quality. Ovulation rates, measured by the number of corpora lutea, were compared between 4 nutritional treatments: senesced phalaris (Phalaris aquatica), phalaris plus 500. g lupin grain per day, lucerne (Medicago sativa) or chicory (Chicorum intybus) pastures. The study used 100 Merino ewes per treatment, divided between 2 replicates. The experiment was repeated in 3 years; February 2006, and January 2007 and 2008. Oestrus was synchronised and the ewes grazed the pastures for 9 days prior to ovulation at times corresponding to days 8-17 of the cycle in 2006, and days 6-14 in 2007 and 2008. The proportion of ewes producing multiple ovulations was higher (P<0.05) in the lucerne and chicory (0.36, 0.38) than the phalaris (0.27), and intermediate in the lupin (0.33) treatment. Regression analysis showed that the proportion of ewes with multiple ovulations increased with the quantity of live herbage (P<0.04). Responses were achieved even at low levels of live herbage with 90% of the maximum proportion of multiples occurring at 350. kg DM/ha. It is concluded that providing short-term grazing of live chicory or lucerne to ewes can increase ovulation rates relative to ewes grazing senesced phalaris and to levels similar to those achieved by lupin grain supplementation. © 2010.

Robertson S.M.,Charles Sturt University | Robertson S.M.,Co operative Research Center for Future Farm Industries | Southwell A.F.,Charles Sturt University | Southwell A.F.,Co operative Research Center for Future Farm Industries | And 2 more authors.
Animal Production Science | Year: 2014

Month of joining and lamb sale strategy influence both the quantity and so value of lamb produced, and the feed required, so are important management decisions contributing to the profitability of sheep systems. Simulation modelling was used to evaluate the impact on gross margins of three lamb sale strategies for different months of joining and varying stocking rates. A flock of purchased Merino ewes producing crossbred lambs in southern Australia was modelled between 1971 and 2011. April joining produced higher gross margins than November or January only if the number of ewes per hectare was increased to potential carrying capacity. At the optimum stocking rate for each month of joining, three sale policies - a flexible lamb sale policy (where lambs were sold depending on seasonal conditions); selling lambs in December; or selling at 45-kg liveweight, all produced a similar mean gross margin, but the feed resources required were least using the flexible strategy (April-joined mean 195 ± 253 s.d. kg/ha for flexible compared with 219 ± 270 kg/ha if selling December or 1085 ± 459 kg/ha if sold at 45 kg). Mean gross margin differed between sale strategies by up to AU $66/ha if the optimal stocking rate was not used. These results suggest that the most advantageous lamb sale strategy will vary with both month of joining and stocking rate used, and should be considered when optimising sheep management systems. © CSIRO 2014.

Gulliver C.E.,Charles Sturt University | Gulliver C.E.,Co operative Research Center for Future Farm Industries | Friend M.A.,Charles Sturt University | Friend M.A.,Co operative Research Center for Future Farm Industries | And 5 more authors.
Animal Production Science | Year: 2013

Diets high in omega-6 (n-6) fatty acids in mice have been associated with a higher proportion of female offspring, however, the specific effects of dietary fatty acids on the sex ratio of sheep has not previously been reported. The aim of the present study was to determine whether feeding ewes a diet differing in n-6 for 6 weeks before and 3 weeks following conception would increase the proportion of female lambs born. Merino × Border Leicester ewes (n = 296) were allocated to receive either a diet high in n-6 (70% oat grain, 8% cottonseed meal, High n-6 diet) or, a control diet low in n-6 (88% legume silage, Low n-6 diet), for 42 or 53 days before and 17 days after conception, using a stratified block randomisation procedure based on body condition score and liveweight. Following synchronisation, oestrus was detected daily during natural mating with rams. After mating, all ewes grazed improved pastures as one group until lambing. Plasma n-6 concentrations were greater (P < 0.001), the time to parturition was shorter (P < 0.001) and the proportion of female offspring was higher (58.2 vs 43.5%, P = 0.010) when ewes were fed the High n-6 diet compared with the Low n-6 diet. Further research is required to determine whether the observed differences in sex ratio were due to specific alterations in n-6 fatty acids, or other differences in the diets not specifically related to n-6 such as saturated fat or energy density. Copyright © CSIRO 2013.

Broster J.C.,Charles Sturt University | Broster J.C.,Co operative Research Center for Future Farm Industries | Rathbone D.P.,Charles Sturt University | Robertson S.M.,Charles Sturt University | And 5 more authors.
Animal Production Science | Year: 2012

This experiment used contact loggers and GPS collars to evaluate the effect of stocking rate during lambing on ewe movement and contact levels between animals. Twin-bearing Merino ewes were placed in 0.5-ha paddocks sheltered with rows of hessian at stocking rates of 16 and 30 ewes/ha for the low and high stocking rates, respectively. The ewes did not spend more time in more sheltered areas of the paddock, and use of shelter was not influenced by stocking rate. Ewes at the high stocking rate travelled 11% farther per day but crossed through the hessian rows 37% less than ewes at the low stocking rate. Stocking rate did not change the level of contact between ewes, but higher levels of contact were shown between ewes and their lambs at the high stocking rate. The results suggest that the interaction between ewes and their lambs is modified by stocking rate and/or flock size for small groups lambing in shelter rows. © 2012 CSIRO.

Discover hidden collaborations