Effect of day of the estrous cycle at the initiation of a timed artificial insemination protocol on reproductive responses in dairy heifers

Our objectives were to identify stages of the estrous cycle at which initiation of a timed artificial insemination (Ovsynch/TAI) protocol may reduce pregnancy rates and to monitor ovarian follicle dynamics and corpus luteum development after initiation of the Ovsynch/TAI protocol at different stages of the cycle. Cycling Holstein heifers (n = 24) were injected twice with prostaglandin F2alpha to induce estrus and were scanned by ovarian ultrasonography to determine the day of ovulation (d 0). Heifers were assigned to initiate the Ovsynch/TAI protocol at d 2 (n = 5), 5 (n = 5), 10 (n = 4), 15 (n = 5), or 18 (n = 5) of the cycle. The Ovsynch/TAI was initiated with an injection of gonadotropin-releasing hormone agonist followed 7 d later with an injection of prostaglandin F2alpha. At 36 h after injection of prostaglandin F2alpha, heifers were injected with gonadotropin-releasing hormone agonist and inseminated 16 h later. Heifers were scanned daily during the Ovsynch/TAI protocol and every other day after insemination until 16 d later. Blood samples were collected daily starting at the 1st day heifers were scanned and continued until 16 d after insemination. Initiation of the Ovsynch/TAI protocol at d 15 of the estrous cycle caused heifers to ovulate prior to insemination. A shortened return to estrus (< 16 d) was caused by ovulation failure to the second gonadotropin-releasing hormone injection, by incomplete regression of the corpus luteum, and by short life-span of the induced corpus luteum. Day of the cycle in which the Ovsynch/TAI protocol is initiated affects dynamics of follicular development, plasma progesterone profiles, and occurrence of premature ovulation. Size of the pre-ovulatory follicle was associated positively with subsequent progesterone concentrations following insemination.     

Aflatoxin B<Subscript>1</Subscript> Binding to Sorbents in Bovine Ruminal Fluid

A recent approach to the problem of contamination of agricultural products by aflatoxin B₁ (AFB₁) is to add non-nutritional adsorbents to animal diets in order to sequester ingested aflatoxins. We conducted in vitro experiments to develop a rapid and cheap model using ruminal fluid to assess the ability of sorbent materials to bind AFB₁. Seven sorbents (hydrated sodium calcium aluminosilicate; clinoptilolite; zeolite; two types of bentonite; sepiolite; and PHIL 75), commonly added to bovine diets were incubated in water and ruminal fluid in the presence of AFB₁. Hydrated sodium calcium aluminosilicate, sepiolite and one of the bentonites bound 100% of the AFB₁ in the presence of both ruminal fluid and water; clinoptilolite bound about 80% of AFB₁ in both liquids; whereas the affinities for the mycotoxin of zeolite (50%) and the other sample of bentonite (60%) in water seem to be increased by about 40% in ruminal fluid incubations. PHIL 75 had the poorest binding ability: about 30% in water and 45% in ruminal fluid. In view of the differences in toxin binding in water and ruminal fluid, it is preferable to use the ruminal fluid model for the in vitro pre-screening of sorbent materials potentially useful as adjuvants to ruminant feeds.     

Subcutaneous administration of paclitaxel in dogs with cancer: A preliminary study

Intravenous paclitaxel has been underused in dogs due to severe and acute hypersensitivity reactions. Subcutaneous (SC) administration of paclitaxel and its safety are unknown. In this preliminary study, SC administration of paclitaxel was evaluated for hypersensitivity reactions and toxicity in 21 dogs with advanced cancer. Dogs received 1 to 5 paclitaxel doses, ranging from 85 to 170 mg/m², SC every 14 or 21 days. A total of 40 paclitaxel doses were administered and none of the 21 dogs developed systemic or acute local hypersensitivity reactions. Severe skin lesions at the injection site developed in 2 dogs after the 4th injection at the same location. Grade 4 neutropenia was observed in 50% of the dogs 5 days after the first treatment at 115 mg/m² (n = 14). Two animals developed Grade 5 diarrhea and died likely due to hemodynamic failure or sepsis. Paclitaxel can be administered SC in dogs with no hypersensitivity reaction.