Publications by authors named "A M Swinbourne"
Treatment with intra-vaginal progesterone pessaries for synchrony of estrus is essential in fixed-time artificial insemination (AI) of sheep. Globally, the conventional 14-day pessary treatment is the mainstay of commercial AI programs. It has remained largely unchanged for many decades even though it is associated with variable patterns of estrus and often disappointing pregnancy rates.
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- Twin lamb mortality is a major economic issue in the Australian sheep industry, and maternal betaine supplementation may improve lamb survival rates.
- The study tested the effects of giving ewes 4 g/day of betaine during late gestation on twin lambs' live weight, temperature regulation, vigour, and survival under field conditions.
- Results showed that while betaine increased certain health indicators in ewes and improved neonatal thermoregulation, control lambs were initially heavier and suckled faster than those from betaine-supplemented ewes.
In Australia, dystocia is responsible for 53% of lamb mortalities, and calcium deficiencies may be a contributing factor. A negative dietary cation-anion difference (DCAD) diet can increase calcium concentrations in sheep. Therefore, this study aimed to investigate the effects of a negative DCAD diet on metabolic state, mineral status, and parturition duration in ewes compared with those fed a positive DCAD diet.
View Article and Find Full Text PDFEach year in Australia, 53% of lamb mortalities are attributed to dystocia, with subclinical maternal calcium deficiencies likely contributing to dystocia rates. A negative dietary cation and anion difference (DCAD) diet has increased circulating calcium in sheep. Therefore, this study aimed to investigate the effects of supplementing twin-bearing, grazing ewes with a negative DCAD partial mixed ration (PMR) during late gestation on ewe calcium and magnesium concentrations and subsequent lamb growth and survival.
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- The study investigated how long-term nutrition (LTN), short-term nutrition (STN), and progesterone supplementation affect the timing of estrus and reproductive success in ewes.
- High LTN improved pregnancy rates and litter size but interacted with STN in affecting estrus timing, while STN alone raised pregnancy rates without changing litter size.
- Progesterone supplementation enhanced estrus synchrony but delayed its onset and did not impact overall pregnancy rates or litter size, indicating nutrition strategies are crucial for improving artificial insemination outcomes.