S. Gelaye

Anthelmintic resistance on goat farms in Georgia: efficacy of anthelmintics against gastrointestinal nematodes in two selected goat herds

Gastrointestinal nematode (GIN) parasitism is a major constraint to production of goats in the southeastern United States. The conventional method of control used by producers in this region is frequent use of anthelmintics during the warm season. Overuse of anthelmintics has led to an increase in the incidence of anthelmintic resistance in many parts of the world, but data on prevalence of anthelmintic resistance in GIN of goats in the southeastern United States are very limited. To address this issue, anthelmintic efficacy was determined in goat herds at the Fort Valley State University, Agricultural Research Station (FVSU-ARS) and the University of Georgia, College of Veterinary Medicine (UGA-CVM) using fecal egg count reduction (FECR) tests and DrenchRite((R)) larval development assays (LDA). At FVSU-ARS, 2-year-old Spanish goat does were randomly allocated to one of nine different treatment groups (n = 10): albendazole (ABZ; 20mg/kg body weight (BW)), fenbendazole (FBZ; 20mg/kg BW), ivermectin (IVM; 0.4 mg/kg BW), doramectin (DRM; 0.4 mg/kg BW), moxidectin (MOX; 0.4 mg/kg BW), levamisole (LEV; 12 mg/kg BW), morantel tartrate (MOR; 10mg/kg BW), a combination of IVM (0.4 mg/kg BW) and ABZ (20 mg/kg BW), and untreated controls. At UGA-CVM, goats were randomly allocated to one of five different treatment groups (n = 8): ABZ (20 mg/kg BW), IVM (0.4 mg/kg BW), MOX (0.4 mg/kg BW), LEV (12 mg/kg BW), and untreated controls. All drugs in both experiments were administered orally. Anthelmintic efficacy was calculated by comparing 14-day post-treatment FEC of treated and control animals, and percent reductions were interpreted using the World Association for the Advancement of Veterinary Parasitology guidelines for resistance. For the LDA, nematode eggs were isolated from pooled fecal samples of untreated control goats in each herd and used to perform DrenchRite((R)) assays. In the FVSU-ARS herd, MOX, LEV, the combination of IVM and ABZ, IVM, DRM, ABZ, MOR, and FBZ reduced FEC by 100, 91, 88, 78, 76, 62, 48, and 10%, respectively. In the UGA-CVM herd, MOX, LEV, ABZ and IVM, reduced FEC by 100, 94, 87, and 0%, respectively. In both herds moxidectin was the only drug tested that was fully effective. Results of the LDA were in agreement with results of the FECR tests for both herds. These data demonstrate the presence of GINs resistant to all three major anthelmintic classes in both goat herds.

Superovulation, synchronization and breeding of does

Abstract Goats can be synchronized for breeding at the convenience and advantage of the producer with exogenous hormones like progesterones or analogues of progesterones (e.g. 6α-methyl-17α-acetoxyprogesterone, fluorogestone acetate), in association with pregnant mare serum gonadotropin, human chorionic gonadotropin, porcine follicular stimulating hormone or injections of cycling does with luteolytic agents like cloprostenol which is a prostaglandin analogue. Anestrous does can be primed with progesterone or its analogues resulting in a diestrus condition. At the withdrawal of the priming agents, gonadotropins or gonadotropin releasing hormone (GnRH) can be administered for estrus and ovulation to occur. Exogenous hormones or their combinations including luteinizing hormone, follicular stimulating hormone and estradiols have been used successfully. These hormone combinations may enhance estrus induction soon after cessation of treatment (20–72 h), or duration of estrus (16–48 h), resulting in improved ovulation (1.4–24.5) and conception rate. Return to estrus, especially for anestrous does during the non-breeding season, is rare for does treated with the above methods. However, by administering melatonin to simulate physiological short day-length conditions, does will conveniently cycle several times for breeding. Thus, does can be superovulated and prepared for embryo transfer or in-vitro fertilization anytime during the year.

Performance of yearling goats fed alfalfa and florigraze rhizoma peanut hay

Two trials comparing the nutritional value of peanut (P) hay (Arachis giabrata Benth.) and alfalfa (A) (Medicago sativa L.) hay were conducted. The first involved 45 growing goats (24 Saanen, 11 Alpine, seven Toggenburg and three Nubian) averaging 18.3 kg body weight (BW). Goats had free access to feed and water throughout the 20-week study and were weighed at weekly intervals. They were offered equal amounts of A, P or AP twice daily. Goats fed P consumed approximately the same amount of dry matter (DM) but gained more BW (P<0.10) and were more efficient (P<0.10) in converting DM into gain than those fed A or AP. A balance trial with 16 wether goats (12 Saanen, three Toggenburg and one Alpine) averaging 25.6 kg resulted in higher digestible DM (P<0.05) and digestible cell wall fractions for goats fed P than A. All goats were in positive nitrogen balance, and nitrogen retained as a percentage of intake declined (P<0.08) from 31.0% for goats fed A to 18.4% for those fed AP, with an intermediate value of 26.5% for goats fed P. In these studies, goats utilized the dry matter of P more efficiently for body weight gain.

In vitro fertilization of goat oocytes during the non-breeding season

A total of 12 does, from mixed Swiss breeds (11 Alpine and 1 Saanen), comprising donors (na 6) and recipients (na 6), were used in two experiments during the non-breeding season (January to June 1997) at the Agricultural Research Station of Fort Valley State University, Georgia, USA. Immature cumulus-oocyte complexes (COC) were collected either by laparotomy (surgery, Experiment 2) or aspirated from ovaries obtained from ovariectomized does (Experiment 1). The oocytes were recovered from 2 to 6 mm diameter follicles and matured in vitro for 24 h in TCM-199 medium supplemented with 10% fetal bovine serum (FBS), 100 mg LH/ml, 0.5 mg FSH/ml and 1 mg estradiol 17b/ml at 38.58C in humid 5% CO2 in air. Expanded COC, obtained from 24 h maturation, were fertilized as described by Parrish et al. (Parrish, J.J., Susko-Parrish, J.L., LeibfriedRutledge, M.L., Critser, E.S., Eyestone, W.H., First, N.L., 1986. Theriogenology 25, 591‐600). Methods of oocyte retrieval (laparotomy vs. ovariectomy) did not affect maturation and fertilization rates. Although the cleavage rate was significantly higher for oocytes obtained by ovariectomy (100%) compared to those retrieved after laparotomy (79%; P 0.05) and morula/blastocyst-stage embryos (90% vs. 65%; Pa 0.05) after ovariectomy and laparotomy, respectively. A total of 21 morula/blastocyst-stage embryos were transferred to six recipients. No pregnancy was detected either by progesterone assay or ultrasonography. Results from this study indicate that oocytes from Swiss Alpine and Saanen breeds born and raised under the climate conditions prevailing in Georgia, USA (3285’N latitude and 8388’W longitude) can be successfully matured and fertilized in vitro, during the nonbreeding season, and that embryo production through in vitro fertilization technology may be an alternative approach to circumvent seasonal anestrus in temperate climates. # 2000 Elsevier Science B.V. All rights reserved.

Nutritive value of florigraze rhizoma peanut as an alternative leguminous forage for goats

Two studies were conducted to evaluate growth performance and nitrogen utilization by yearling goats fed alfalfa (A) or florigraze rhizoma peanut meals (Pe). During the 49-day growth trial,36 growing goats (BW 30.1 kg) were randomly assigned to experimental diets containing the same concentration of crude protein (16%), digestible energy (2.67 Mcal·kg−1) Ca (0.84%) and P (0.56%), as-fed. Alfalfa and peanut meal accounted for 10.5% of dry weight in diet A and Pe, respectively, and an equal mixture of the two test forages was included in diet APe. Fifteen castrated male yearling goats (BW 47.9 kg) were used in a balance trial consisting of a 7-day adjustment and a 10-day collection phase. Feed was offered ad libitum and 100% of voluntary intake determined during the preliminary phase, during the growth and balance trials, respectively. Dry matter (DM) intake in the growth trial tended to decline from 1.41 kg for A to 1.36 kg for Pe. Goats fed A or Pe had similar daily gain (191.8 g), which tended to be higher (P<0.11) than APe (179.6 g). During the balance trial, DM and water intakes were unaffected by diet and were 2.23 and 5.97% of BW, respectively. Digestibility of neutral detergent fiber was improved (P<0.07) from 41.1 to 50.9% when goats were fed Pe instead of A. Treatments did not influence amounts of nitrogen consumed, or excreted in feces and urine. Data from both trials demonstrated that A and Pe have comparable nutritional value and both are utilized efficiently by growing goats.

Embryo recovery, evaluation, storage and transfer in goats

Abstract Embryo recovery, manipulation and preservation (frozen at −196°C) with cryoprotective agents like glycerol or dimethyl sulfoxide make future transfer of genetic resources possible. Survival of embryos has been better for those beyond the two-cell stage of development. Positioning transferred embryos in the oviduct or uterus, and ovaries with functional corpora lutea (CL) in the recipient doe are factors affecting successful implantation. Techniques in embryo recovery, temporary storage, longterm preservation of goat embryos, and methods of transfer for successful pregnancy in goats are reviewed. It is concluded that over 70% of fertilized ova can be surgically recovered from most superovulated does using exogenous hormones like equine anterior pituitary extract (HAP) or follicle stimulating hormone (FSH). Embryos, after microscopic morphological evaluation, can be temporarily stored cultured in bicarbonate or phosphate buffer saline medium enriched with homologous goat serum, for 2–3 d at below 10°C, or indefinitely at −196°C in liquid nitrogen. Successful transfer with good embryo survival has to take into consideration the stage of development (2–3 d post fertilization; 2–12-cell stage), rate of ovulation or state of CL of recipients and place of deposition of embryos relative to CL.