Zhang C.,University of Auckland |
Easteal A.J.,University of Auckland |
Edmonds N.R.,University of Auckland |
Liang G.,University of Auckland |
And 3 more authors.
Macromolecular Research | Year: 2010
A polymer-vitamin B12 implant system has been developed to overcome the disadvantages of traditional vitamin B12 administration to sheep. The ethylene/vinyl acetate (EVAc) copolymer was pre-blended with crystalline vitamin B12. The blends were then extruded at 100 °C at a constant pressure and rate using a piston extruder to form a polymer-vitamin B12 composite cord. The final implant was a cylinder 2 mm in diameter and 4 mm in length. Determination of the rate of vitamin B12 release from the implant into a pH7.4 phosphate buffer at 37 °C showed that the release rate was strongly dependent on the feed concentration, size and shape of vitamin B12 crystals. The well-known Korsmeyer-Peppas exponential equation was applied to and the release mechanism was found to be a typical anomalous transport mechanism with a strong diffusion-controlled feature between pure diffusion-controlled and Case-II transport mechanisms because the n values obtained were between 0.45 and 0.51 for most polymer-vitamin B12 cylindrical implant systems. © The Polymer Society of Korea.
Bryan M.A.,VetSouth Ltd. |
Bo G.,Institute Reproduccion Animal Cordoba IRAC |
Mapletoft R.J.,University of Saskatchewan |
Emslie F.R.,Bomac Laboratories Ltd.
Journal of Dairy Science | Year: 2013
In seasonally calving, pasture-based dairy farm systems, the interval from calving to first estrus is a critical factor affecting reproductive efficiency. This study evaluated the effects of equine chorionic gonadotropin (eCG) on the reproductive response of lactating, seasonally calving dairy cows diagnosed with anovulatory anestrus by rectal palpation. Cows on 15 commercial dairy farms were selected for initial inclusion based on nonobserved estrus by 7d before the planned start of mating. All cows were palpated rectally and evaluated for body condition score and ovary score, and were included for treatment according to the trial protocol if diagnosed with anovulatory anestrus. All cows received a standard anestrous treatment protocol consisting of insertion of a progesterone device, injection of 100μg of GnRH at the time of device insertion, and injection of PGF2α at device removal (GPG/P4). Cows were randomly assigned to 1 of 2 groups (6d or 7d) for duration of progesterone device insertion. Within each of these groups, cows were further randomly assigned to receive either 400IU of eCG at device removal or to remain untreated as controls, resulting in a 2×2 arrangement of treatment groups: (1) 6-d device and no eCG (n=484); (2) 6-d device and eCG (n=462); (3) 7-d device and no eCG (n=546); and (4) 7-d device and eCG (n=499). Cows were detected for estrus from the time of progesterone device removal and were inseminated; those not detected in estrus within 60h after progesterone device removal received 100μg of GnRH and were inseminated at 72h. The primary outcomes considered were proportion of cows conceiving within 7d of the beginning of breeding (7-d conception rate; 7-d CR), proportion pregnant within 28d (28-d in calf rate; 28-d ICR), and days to conception (DTC). We found no significant differences between the 6- and 7-d insertion periods and found no 6- or 7-d insertion period × eCG treatment interactions. Inclusion of eCG into either length of GPG/P4 protocol increased 7-d CR (36.0 vs. 30.6%) and 28-d ICR (58.6 vs. 52.3%) and decreased median days to conception. The use of eCG in GPG/P4 breeding protocols will improve reproductive efficiency in seasonally calving, anestrous dairy cattle. © 2013 American Dairy Science Association.
Bryan M.A.,VetSouth Ltd |
Bo G.A.,Catholic University of Córdoba |
Heuer C.,Massey University |
Emslie F.R.,Bomac Laboratories Ltd
Reproduction, Fertility and Development | Year: 2010
In seasonally calving dairy areas, a critical index of efficiency and profitability is the ability to maintain a short annual calving spread. In essence, this means that all cows need to conceive within 90 days of calving. Anovulatory anoestrus (AA) is a major barrier to reproductive performance under these conditions and the successful treatment of AA is an important aspect of reproductive intervention. The present paper reviews regimens used to treat AA in New Zealand and reports on a large-scale field trial investigating the effects of equine chorionic gonadotrophin (eCG) within a proven efficacious treatment protocol. The administration of eCG at the time of removal of a progesterone-releasing device in an 8-day, oestradiol benzoate (EB)-based treatment protocol increased the percentage of cows in calf after 7 and 28 days of breeding. The interaction between cow age and treatment with eCG was significant, with cows over 5 years of age having higher conception rates (P ≤ 0.002) and 7 day in-calf rates (P ≤ 0.002) than cows on a standard 8-day treatment protocol without eCG. The addition of eCG to a standard 8-day EB/progesterone protocol can improve reproductive success in seasonally calving AA dairy cows.© 2010 IETS.
Bayer AG and Bomac Laboratories Ltd | Date: 2010-07-13
veterinary preparations, namely, mineral supplements for livestock; vaccines.