Catherine Gulliver Collaborators: Dr Edward Clayton, Dr Michael Friend, Dr John Wilkins, Dr Belinda King, Dr Susan Robertson
Outline Background Why alter sex ratio? Factors affecting sex ratio? Maternal nutrition Polyunsaturated fatty acids (PUFAs) Omega-3, omega-6 and sex ratio Pen trial Take home messages
Why Alter Sex Ratio? Skew offspring sex ratio to favour preferred gender Prime lambs Maternal flocks Dairy cattle Male offspring Female offspring Female offspring
Factors Affecting Sex Ratio? X or Y sperm Genetic factors Environmental factors: Maternal nutrition Timing of insemination Time of season Litter size
Factors Affecting Sex Ratio? Adapted from Cameron (2004)
Factors Affecting Sex Ratio? Food Condition Weight Adapted from Cameron (2004)
Maternal Condition Strongest correlation with sex ratio when condition measured at/near conception (Cameron, 2004) Females in poorer condition at conception less male offspring (Review: Rosenfeld & Roberts, 2004) Deer, pigs, sheep
Maternal Diet Increased glucose in vitro favours male embryos (Cattle: Gutierrez-Adan et al. 2001) Increased glucose in vivo male-biased litters (Mice: Cameron et al. 2008) Mice fed high-fat / low carbohydrate diet male-biased litters (Rosenfeld et al. 2003) Mechanism?
Potential Mechanisms Pre-conception mechanisms: A) Differential motility/transport B) Selective fertilisation Post-conception mechanisms: C) Faster embryo development pre-implantation D) Developmental arrest of embryo pre-implantation (Rosenfeld & Roberts, 2004)
Polyunsaturated Fatty Acids (PUFAs) Long-Chain Omega-3 Long-Chain Omega-6
Polyunsaturated Fatty Acids (PUFAs) Omega-3 Fresh forage Omega-6 Grain α-linolenic acid (C18:3n-3) Short-chain fatty acids Linoleic acid (C18:2n-6) Eicosapentaenoic acid (EPA) Arachidonic Acid (AA) Long-chain fatty acids
PUFAs and Reproduction Improve fertility Reduce post-partum interval to ovulation (De Fries et al. 2008) Increase follicular growth (Lucy et al. 1991) Improve oocyte quality & embryo survival (Santos et al. 2008) Sperm transport (Rooke et al. 2001) Sex ratio?
PUFAs and Sex Ratio Omega-3 α-linolenic acid Omega-6 Linoleic acid Eicosapentaenoic acid (EPA) Arachidonic Acid (AA) Prostaglandin Series-3 (PG-3) ANTI - INFLAMMATORY Prostaglandin Series-2 (PG-2) PRO - INFLAMMATORY Improve survival of males? (Marsupials: Rosenfeld & Roberts, 2004) (Heifers: Wamsley et al. 2005) Loss of male embryos? (Mice; Fountain et al. 2008)
Research Questions 1. Can we alter sex ratio of offspring by altering ratio of omega-6:omega-3 in the maternal ewe diet? 2. Physiological mechanisms? a) Fatty acid concentrations in plasma and RBC b) Prostaglandins & inflammation Experiments Animal house trial prostaglandin response Pen trial sex ratio
Pen Trial - Aims Determine effect of high omega-3 diet on: 1. Blood fatty acid profile 2. Time to oestrus 3. Ovulation rate 4. Pregnancy rate 5. Sex ratio of offspring
Dietary Treatments High omega-3 88% Silage High omega-6 70% Oats Omega-6 : Omega-3 0.93 : 1 Omega-6 : Omega-3 13.03 : 1
Pens and Feeding Pen layout randomised block design 3 pens per treatment Total N = 148 per treatment Fed diets 6 weeks pre- and 3 weeks post mating
Measurements Live weight and condition score Blood samples for fatty acid analysis (every 2 weeks)
Mating Synchronised with CIDRS mated on 1 st natural oestrus
Mating Synchronised with CIDRS mated on 1 st natural oestrus Mating with crayon-harnessed rams (2 per pen)
Pregnancy and Lambing Transrectal-ultrasound ovulation rate & pregnancy Corpus luteum September lambing record sex of lambs
Plasma Omega-6:Omega-3 Ratio
Plasma Omega-6:Omega-3 Ratio Oats High Omega-6 p < 0.05 Silage High Omega-3
Prostaglandin (PGFM) Response
Prostaglandin (PGFM) Response Oats High Omega-6 Silage High Omega-3 p < 0.05
Time to Oestrus
Time to Oestrus Oats High Omega-6 Silage High Omega-3 p < 0.05 Day of Mating Cumulative Proportion Showing Oestrus (%)
Time to Lambing
Time to Lambing Oats High Omega-6 Silage High Omega-3 p < 0.05
Reproduction Results Dietary Treatment Reproduction Measure High Omega-3 High Omega-6 P-value Proportion of ewes ovulating (%) 82.73 88.11 0.200
Reproduction Results Dietary Treatment Reproduction Measure High Omega-3 High Omega-6 P-value Proportion of ewes ovulating (%) 82.73 88.11 0.200 Mean ovulation rate: For ewes that ovulated 1.03 (± 0.02) 1.04 (± 0.02) 0.558 For all ewes 0.77 (± 0.05) 0.83 (± 0.06) 0.190
Reproduction Results Dietary Treatment Reproduction Measure High Omega-3 High Omega-6 P-value Proportion of ewes ovulating (%) 82.73 88.11 0.200 Mean ovulation rate: For ewes that ovulated 1.03 (± 0.02) 1.04 (± 0.02) 0.558 For all ewes 0.77 (± 0.05) 0.83 (± 0.06) 0.190 Proportion of ewes pregnant (%) 89.44 91.84 0.483
Reproduction Results Dietary Treatment Reproduction Measure High Omega-3 High Omega-6 P-value Proportion of ewes ovulating (%) 82.73 88.11 0.200 Mean ovulation rate: For ewes that ovulated 1.03 (± 0.02) 1.04 (± 0.02) 0.558 For all ewes 0.77 (± 0.05) 0.83 (± 0.06) 0.190 Proportion of ewes pregnant (%) 89.44 91.84 0.483 Mean foetal number: For ewes pregnant 1.19 (± 0.03) 1.15 (± 0.03) 0.451 For all ewes 1.07 (± 0.04) 1.05 (± 0.04) 0.764
Reproduction Results Continued... Dietary Treatment Reproduction Measure High Omega-3 High Omega-6 P-value Pregnancy loss (%) 5.65 2.22 0.153
Reproduction Results Continued... Dietary Treatment Reproduction Measure High Omega-3 High Omega-6 P-value Pregnancy loss (%) 5.65 2.22 0.153 Proportion of ewes lambing (%) 82.39 90.48 0.044
Reproduction Results Continued... Dietary Treatment Reproduction Measure High Omega-3 High Omega-6 P-value Pregnancy loss (%) 5.65 2.22 0.153 Proportion of ewes lambing (%) 82.39 90.48 0.044 Mean number of lambs born: For ewes lambing 1.26 (± 0.04) 1.26 (± 0.04) 0.989 For all ewes 1.04 (± 0.05) 1.14 (± 0.05) 0.148
Sex Ratio Males Females Males Females Silage High Omega-3 Oats High Omega-6
Sex Ratio 56.5 41.8 Males Females Males Females Silage High Omega-3 Oats High Omega-6
Sex Ratio 56.5 58.2 43.5 41.8 Males Females Males Females Silage High Omega-3 Oats High Omega-6
Sex Ratio p = 0.117 56.5 p = 0.036 58.2 43.5 41.8 Males Females Males Females Silage High Omega-3 Oats High Omega-6
Sex Ratio p = 0.010 p = 0.117 56.5 p = 0.036 58.2 43.5 41.8 Males Females Males Females Silage High Omega-3 Oats High Omega-6
Sex Ratio High Omega-6 Oats diet
Conclusions Ewes fed high omega-6 oats diet had: Higher omega-6 levels in blood Increased prostaglandin response Shorter time to oestrus and lambing Higher proportion of female lambs Pre-conception mechanism? Timing of oestrus in relation to ovulation and fertilisation?
Take Home Messages Omega-6:omega-3 ratio in feed important Further research: Mechanisms Pre- or post-conception nutrition? Prostaglandin and inflammation? Useful, practical and cost effective feed types
Acknowledgements WWAI Farm Staff: Greg Scott, Greg Clark, Steven Huckell, Michael Loiterton, Rex Edis John Wilkins ultrasounding John Piltz, Craig Rodham, Penny Philips, Geoff Casburn, Richard Meyer, Peter Hawkins, Jamie Ayton Brian Alston, Tony Hobbs, Brad Kelk, John Broster, Steph Knott CSU Students Jess & Alex Ausfarm Nutrition My family and anyone else that I ve forgotten!
Questions?
Contact Details Catherine Gulliver Mobile: 0427 587 312 Email: cath_gully@hotmail.com Location: Orange, NSW
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Oestrous Cycle of the Ewe