Habitat-related prevalence of macroscopic Mycobacterium bovis infection in brushtail possums (Trichosurus vulpecula), Hohonu Range, Westland, New Zealand

AIM: To identify broadscale habitat factors influencing the prevalence of macroscopic Mycobacterium bovis infection in brushtail possums (Trichosurus vulpecula) at a site in Westland, New Zealand. METHODS: During 1973/74, 1989/90 and 1997, we undertook repeated cross-sectional surveys of M. bovis infection in a possum population on the Hohonu Range , Westland. Data were analysed to determine the influence of site-specific habitat characteristics (land form, aspect, slope, altitude), distance from forest-pasture margin and time since infection on the spatial and temporal prevalence of macroscopic M. bovis infection. RESULTS: The prevalence of M. bovis infection was highest in 1973/74 (13.4%), compared with 1989/90 (3.1%) and 1997 (9.4%). The prevalence of macroscopic M. bovis infection was significantly influenced by habitat, as indexed by altitude and slope in this study site. Every 100 m increase in elevation was associated with a 29% decrease in the odds of infection, and every 10 degrees increase in slope was associated with a 20% decrease in the odds of infection. For possums caught in the lowland podocarp forest (altitude 100-200 m, average slope=5.7 degrees ), the odds of infection were nearly 30-fold higher than those for possums caught in high-altitude hardwood forest near the tree line (altitude 900-1000 m, average slope=28 degrees ). Whilst the prevalence of disease fluctuated markedly between surveys, its broadscale spatial distribution changed little over time. Proximity to the forest-pasture margin had no significant influence on the prevalence of disease, once the effect of habitat was taken into account. CONCLUSION: The prevalence of macroscopic M. bovis infection in possums was strongly influenced by habitat type, being highest in habitats that supported the highest density of possums, and lowest in habitats where population density was low. There was no evidence of progressive spread of M. bovis infection in possums into forest away from pasture-forest margins over the 24-year period of these surveys.     

Estimated genetic parameters for palatability traits of steaks from Brahman cattle

Heritabilities and genetic and phenotypic correlations were estimated from carcass and beef palatability data collected from Brahman calves (n = 504) born in central Florida from 1996 to 2000. Traits evaluated included Warner-Bratzler shear force (after 7, 14, and 21 d of aging), panel tenderness score, connective tissue amount, juiciness, flavor intensity, and off flavor (after 14 d of aging), percentages of raw and cooked lipids, and milligrams per gram of muscle calpastatin activity. Parameters were estimated using an animal model and derivative-free restricted maximum likelihood procedures. Estimated heritabilities for d 7, 14, and 21 shear force were 0.14,0.14, and 0.06, respectively, indicating that improvement in these traits by selection would be slow. Estimated heritabilities of sensory panel attributes were 0.11, 0.12, 0.05, 0.04, and 0.01 for tenderness, connective tissue amount, juiciness, flavor intensity, and off flavor, respectively. The estimated heritabilities for percentages of raw and cooked lipids, and calpastatin activity were 0.34, 0.17, and 0.07, respectively. Most of the estimated genetic correlations among palatability traits and for palatability traits with fat thickness, marbling score, and loin muscle area were consistent with other estimates from the literature. Results indicated that improvement in tenderness based on selection for favorable shear force, sensory panel tenderness, or calpastatin activity would be slow; therefore, postslaughter intervention programs should also be considered.     

Human factors affecting the behaviour and productivity of commercial broiler chickens

1. The purpose of this study was to examine the relationship between stockperson attitude and behaviour; bird behaviour and productivity in the chicken meat industry. 2. No relationship between stockperson attitude and behaviour was observed, which is in contrast to studies in the pig and dairy industries. 3. Evidence is provided for the existence of sequential relationships between stockperson behaviour, bird fear levels and productivity in the broiler farms examined. 4. The mechanism(s) responsible for the negative relationships between fear levels and production is unclear. It is hypothesised that chronic stress or a series of acute stress responses may be the mechanism through which fear affects productivity. 5. The relationship between human behaviour, bird fear levels and productivity indicates the potential that exists to improve productivity and perhaps welfare of commercial broilers by reducing fear levels in broiler chickens.     

Effects of 21-day treatment with melengestrol acetate (MGA) with or without subsequent prostaglandin F2 alpha on synchronization of estrus and fertility in beef cattle

Beef cattle were treated to synchronize estrus using one of three procedures, and effects on subsequent endocrine responses and fertility were studied. Procedures were 1) feeding .5 mg.head-1.d-1 of melengestrol acetate (MGA) for 21 d (M), 2) feeding .5 mg.head-1.d-1 of melengestrol acetate for 21 d followed 14 d later by a single injection of prostaglandin F2 alpha (M + P) and 3) two injections of prostaglandin (PGF) 14 d apart (P). In Exp. 1, 94 beef cows were assigned to be artificially inseminated 12 h after detection of estrus. Procedures for synchronizing estrus did not affect the proportion of cows observed in estrus within 7 d (mean = 70.2%). However, conception rate of cows treated with MGA alone was lower (P less than .01) than that of cows treated with PGF alone (31.8 vs 78.3%). The conception rate of cows in the M + P group was intermediate (57.1%) but greater than that of cows treated with MGA alone (P less than .10). In Exp. 2, 18 heifers were observed for estrus four times daily and bled daily from 1 wk before predicted estrus until second estrus or 35 d post-treatment. Heifers treated with MGA alone maintained lower concentrations of progesterone and higher concentrations of estradiol-17 beta before first estrus than heifers treated with MGA and PGF or PGF alone (P less than .01). Conception rate following insemination was lower after long-term feeding of MGA than after two injections of PGF. Delaying insemination until after a PGF-shortened cycle 14 d after MGA resulted in an intermediate conception rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in protein synthesis during drought conditioning in roots of jack pine seedlings (Pinus banksiana Lamb.)

The impact of drought conditioning on the ability of eight-week-old jack pine (Pinus banksiana Lamb.) seedlings to withstand drought was assessed. Two progressive cycles of drought conditioning significantly increased the survival of seedlings subjected to a subsequent prolonged drought. The in vivo accumulation of several root membrane proteins during drought conditioning was correlated with an increase in seedling survival. A group of root proteins, ranging in molecular mass from 43 to 47 kDa, increased accumulation during one cycle of drought conditioning and to a lesser extent during two cycles of drought conditioning. The accumulation of several low molecular mass membrane and soluble proteins also increased during drought conditioning, suggesting that these proteins may play an important role in the enhancement of drought tolerance. In vitro translation studies showed a general increase in the abundance of protein products encoded by mRNAs from drought-conditioned seedlings. Although the majority of the in vitro translation products appeared in both control and drought-conditioned seedlings, one mRNA encoding a 15 kDA translated protein was more prominent during the second cycle of drought conditioning.