Effects of irrigation deprivation during the harvest period on yield determinants in mature almond trees

Effects of irrigation deprivation during the harvest period on yield determinants in mature almond (Prunus dulcis (Mill.) D.A. Webb cv. Nonpareil) trees were investigated during a 3-year field experiment. Return bloom and fruit set were measured on 2185 individually tagged spurs. Water stress resulting from irrigation deprivation during the harvest period, which purportedly coincides with the time of flower initiation, had no effect on the percentage of spurs that flowered or set fruit during subsequent years. Although water stress had no apparent effect on spur mortality, 66% of the tagged spurs died within 3 years. In addition, many spurs were vegetative by the third year, indicating the importance of spur renewal for sustained fruit production. Reductions in nut yield were evident after two successive years of irrigation deprivation during the harvest period. Regression analysis indicated a loss in yield of 7.7 kg tree(-1) in response to each 1 MPa decrease in stem water potential below -1.2 MPa during the previous seasons. The number of fruiting positions per tree (estimated indirectly for whole trees based on weight of current-year shoots > 5 cm in length) was negatively associated with water stress. Yield reduction in response to water stress during harvest appears to be a compound, multiyear effect, associated with reduced annual growth and renewal of fruiting positions.     

Effect of intravenous lidocaine on isoflurane MAC in dogs

Lidocaine decreases minimum alveolar concentration (MAC) of inhalational anesthetics. This study determined the influence of a low dose, 50 µg kg^?1 minute^?1 (LDI) and high dose, 200 µg kg^?1 minute^?1 (HDI) constant rate infusion of lidocaine on the MAC of isoflurane (I) in dogs. Ten mongrel dogs were anesthetized with I in oxygen and mechanically ventilated. End‐tidal anesthetic (Fe ′A) and CO₂ (Pe ′CO₂) concentrations were monitored at the endotracheal tube adaptor with an infrared gas analyzer calibrated before each experiment with a standardized calibration gas mixture designed for the analyzer. Pe ′CO₂ and body temperature were maintained within normal limits. Noxious stimuli included clamping the hindlimb paw (HC) and electrical current (50 V at 50 cycles second^?1 for 10 milliseconds pulse^?1) applied subcutaneously to the forelimb (FE) at the level of the ulna. After an initial equilibration period of at least 40 minutes at an Fe ′A of 1.7%, the Fe ′A was decreased to a value close to the estimated MAC for dogs. MAC was defined as the Fe ′A mid‐way between the value permitting and preventing purposeful movement. Following baseline MAC, a loading dose of 2 mg kg^?1 of lidocaine IV was administered over 3 minutes followed by the LDI, and MAC determinations for the combination started after 30 minutes of infusion. Once determined, the lidocaine infusion was stopped for 30 minutes and the dog maintained at the ETC that prevented movement without the lidocaine. Following this period, a second loading dose of lidocaine was given (2 mg kg^?1) over 3 minutes followed by the HDI, and the MAC determination procedure repeated after 30 minutes of infusion. Data were analyzed using an anova for repeated measures. MAC of I was 1.34 ± 0.035% (mean ± SEM) for both the FE and HC stimuli. The LDI significantly decreased MAC to 1.09 ± 0.043% (18.7% reduction) and HDI to 0.76 ± 0.030% (43.3% reduction). In conclusion, lidocaine infusions decreased the MAC of isoflurane in a dose‐dependent manner.     

Programs for surveillance and monitoring of antibacterial residues in Australia, 1989 to 1993

SUMMARY The development of a State-based confirmatory testing capability for antibiotic residues in meat in Australia has allowed the rapid feedback to producers failing to comply with antibiotic maximum residue limits. The identification of problem areas in various categories of livestock, and subsequent focused surveillance programs, has reduced the prevalence of antibacterial residues in both domestic and export meat products. Failure to observe withholding periods of antibacterial drugs after treatment is the most significant cause of non-compliance. In the period July 1991 to June 1993 the compliance rate for antibacterial residues for all species was 99.9%.     

Effects of antibiotic therapy at drying off on mastitis in the dry period and early lactation

Four strategies for selecting cows for intramammary therapy with benzathine cloxacillin at drying off were compared in 12 Victorian dairy herds. The bacteriological status of all quarters of all (1044) cows was determined just before drying off, within 2 d of calving, and again 3 to 5 months after calving. All cases of clinical mastitis (from calving to mid-lactation) were recorded. Cows not infected at drying off were allocated randomly to 2 subgroups of approximately 350 cows each: not infected, not treated (NI-NT), or not infected, all quarters treated (NI-AT). New infection rates in the dry period (3.8% for NI-NT vs 2.1% for NI-AT) and in early lactation (4.1% for NI-NT vs 3.9% for NI-AT) were low and these differences were not significant. Incidence of clinical mastitis in early lactation was almost 50% higher for the treated group of uninfected cows compared with the untreated group (0.05 less than p less than 0.1). Cows infected in one or more quarters at drying off were split randomly into 2 subgroups of approximately 170 cows each: infected, all quarters treated (I-AT), or infected quarters treated only (I-QT). The new infection rate during the dry period was nearly 4 times higher for I-QT (15.3%) due to significantly more new infections by Staphylococcus aureus and Streptococcus uberis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of transcutaneous ultrasound over the right flank with transrectal ultrasound for pregnancy diagnosis in the dairy cow

Objective   Evaluate the sensitivity and specificity of transrectal ultrasound and transcutaneous ultrasonography across the right flank between days 31 and 196 of pregnancy in the dairy cow.
Procedure   Pregnancy status and stage of gestation at date of pregnancy diagnosis by transcutaneous and transrectal ultrasonography were determined for 1570 dairy cattle. Sensitivity and specificity values and probabilities of a correct diagnosis for both techniques were determined and compared. Possible effects of gestational age, herd, method of transcutaneous ultrasound diagnosis, cow age, cow and bull breed, and calf sex on the determination of a correct diagnosis of pregnancy status were evaluated for both techniques.
Results   The overall sensitivity and probability of a correct diagnosis of pregnancy status from days 31 to 196 of gestation were significantly higher when using transrectal ultrasound relative to transcutaneous ultrasound over the right flank. However, the sensitivity of transcutaneous ultrasound changed over the course of pregnancy: it was low (7–8%) before day 84, increased to 89% between days 141 and 154, and was close to 100% thereafter. The specificity of both methods did not differ significantly. Herd and gestational age at date of pregnancy diagnosis were significantly associated with making a correct test result using transcutaneous ultrasound, although only the latter predictor was significantly associated with making a correct test result using transrectal ultrasound.
Conclusion   Transcutaneous ultrasound can not be recommended as an accurate method for early pregnancy diagnosis in the dairy cow, particularly on a whole-herd basis. However, if pregnancy testing is undertaken in mid to late gestation, this technique could provide an accurate and rapid alternative to transrectal ultrasound or manual palpation per rectum.     

Association between gestational age and bovine fetal characteristics measured by transcutaneous ultrasound over the right flank of the dairy cow

Objective   To determine bovine fetal characteristics significantly associated with increasing gestational age as measured via transcutaneous ultrasonography over the right flank.
Methods   The length of gestation at date of pregnancy diagnosis via transcutaneous and transrectal ultrasonography was determined for 224 dairy cattle by estimation from subsequent calving dates. A separate dataset was created for each measurable fetal characteristic (i.e. thoracic diameter, abdominal diameter, umbilical diameter, placentome length and placentome height) and risk factors significantly associated with gestational age at pregnancy diagnosis within each dataset, including the fetal characteristic, were identified.
Results   Abdominal diameter was the most frequently observed fetal characteristic and thoracic diameter was the least. Gestational age at pregnancy diagnosis (d) was significantly associated with fetal thoracic diameter (P < 0.01), abdominal diameter (P < 0.01) and umbilical diameter (P = 0.02) when measured via transcutaneous ultrasound. Within each model, sire breed, dam breed, dam age and/or calf sex were also significantly associated with gestational age. Gestational age at pregnancy diagnosis was not significantly associated with either placentome height or length (P > 0.05).
Conclusion   Fetal thoracic diameter, abdominal diameter and umbilical diameter were found to be significantly associated with gestational age between approximate days 73 to 190 of gestation. Transcutaneous ultrasonography may prove a useful method of estimating gestational age in the absence of accurate breeding records.     

The incidence and aetiology of clinical bovine mastitis on 14 farms in Northland,New Zealand

AIM: To estimate the incidence of clinical mastitis and the frequency of isolation of mastitis-causing organisms from clinical cases in one lactation season (July 2005 to May 2006) on 14 dairy farms from the Northland region of New Zealand.

METHODS: Cases of clinical mastitis were determined by trained farm personnel who recorded the identity of affected cows. Pooled milk samples from affected quarter(s) were aseptically collected by the farm personnel, for microbiology. Mean numbers of affected cows and quarters were compared at the population and farm level per 305 cow-days-at-risk (DAR).

RESULTS: One or more cases of clinical mastitis occurred in 559/3,765 (14.8%) lactating cows. The average incidence of clinical mastitis was 0.19 cases per 305 DAR. The incidence in rear quarters (56.2%) was 1.3 times (p=0.027) that of front quarters (43.8%). The incidence of clinical mastitis and numbers of affected quarters were signifi cantly infl uenced by the stage of lactation (higher in early lactation), age (higher in older cows) and farm. At the cow level, the most common isolates were Staphylococcus aureus (23.7%) and Streptococcus uberis (23.3%). No causative organisms were identifi ed in 19.9% of the samples. Each cow had an average of 1.8 quarters affected during a case of clinical mastitis.

CONCLUSIONS: This study demonstrated a higher incidence of staphylococcal clinical mastitis on dairy farms from Northland than has been reported in other regions of New Zealand.