Behaviour of roaster chickens towards an automatic weighing perch

1. Automatic weighing equipment was tested on a flock of 752 roaster chickens reared on litter to 10 weeks of age.

2. Mean body weights obtained automatically were lower than those obtained manually, mainly because of birds perching on the automatic weighing perch with part of their body in contact with the floor.

3. Birds observed on the weighing perch on one day of the week were 3–5 times more likely to use the perch again on the following 2 d than expected on the basis of random perch use by flock members. These birds were also more likely to be seen in the area immediately surrounding the perch than in similar areas elsewhere in the pen.     

Comparison of wheats of high or conventional protein content with added lysine in diets for layers

1. High‐protein wheats (196 or 210 g/kg) were compared with conventional wheat (163 or 162 g/kg) in layers’ diets in three experiments.

2. In diets of 160 g protein/kg without added lysine, high‐protein wheats caused lower rates of production and egg size than conventional wheats in White Leghorns. Lysine supplementation of the former diets eliminated these differences.

3. The improvements in egg production and egg weight were significant with 1 g additional lysine/kg and egg production tended to improve further with 2 g additional lysine/kg, as did egg weight with all subsequent additions, but not significantly so.

4. With diets containing high‐protein wheats supplemented with lysine, high egg production and egg weight could be obtained without a protein supplement (e.g. soyabean meal).

5. In broiler‐breeders egg production was lower and food conversion poorer with high‐protein wheat despite added lysine.     

Penetration of malathion into locusts

Topically applied dilute solutions of malathion in kerosene extract ‘bottoms’ are more toxic and rapid in action than concentrated ones. Dilute solutions spread farther, penetrate more rapidly and consequently their rate of activation into the more toxic malaoxon is higher. With a single dose of 2·5% malathion the rate of penetration and activation varies according to the loci of topical application, presumably reflecting differences in sclerotisation of the cuticle. There are also inherent differences in the susceptibility of various body regions associated perhaps with the differential vulnerability of some vital internal organ (e.g. the central nervous system). Very rapid hydrolytic degradation of malathion occurs through its conversion into malaoxon; locusts survive the lethal action of malathion by way of such degradation only where activation into malaoxon takes place in areas away from the sensitive head region, or where the rate of activation is slow, or where the circulatory system delays its arrival at such sensitive sites. The higher rate of activation observable in immature adults of Schistocerca gregaria compared with mature adults is, however, counterbalanced by a higher rate of hydrolysis in the former.     

The effect of subclinical Mycobacterium paratuberculosis infection on days open in Michigan, USA, dairy cows

A prospective cohort study design was used to evaluate the impact of subclinical Mycobacterium paratuberculosis infection on days open in a sample of Michigan dairy herds with a history of cows positive for M. paratuberculosis diagnosed by fecal culture. Participating herds were tested and productivity and reproduction records were monitored for 18 months. All cows > or = 24 months old were tested for M. paratuberculosis infection using the ELISA and radiometric fecal-culture (RFC) techniques. Test-negative cows were re-tested at the conclusion of the monitoring period. Multivariable regression models were used. Using both tests in parallel, the overall sample apparent prevalence for M. paratuberculosis infection was 41.8% (223/533 animals tested). Adjusting for diagnostic sensitivity and specificity, this resulted in a calculated sample true prevalence of 59.9%. ELISA-positive cows (on average) had a 28-day increase in days open when compared to ELISA-negative cows (p=0.02). The diagnostic method used to define a case altered the apparent association between paratuberculosis test status and days open. Fecal culture was a less-effective diagnostic tool for use in herds with a high prevalence of infected animals. The increase in days open in the ELISA-positive cows was an indication that perhaps reduced estrus expression or an increased post-partum anestrous period occurred in the subclinically infected ELISA-positive animals. This might have been due to a negative energy balance associated with M. paratuberculosis infection.     

Photosynthate distribution patterns in cherrybark oak seedling sprouts

We used 14C tracers to determine photosynthate distribution in cherrybark oak (Quercus pagoda Raf.) seedling sprouts following release from competing mid-story vegetation. Fall acquisition of labeled photosynthates by seedlings followed expected source-sink patterns, with root and basal stem tissues serving as the primary sinks. Four months after the seedlings had been labeled with 14C, they were clipped to induce sprouting. First-flush stem and leaf tissues of the resulting seedling sprouts were the primary sinks for labeled photosynthates stored in root tissues. Second-flush stem and leaf tissues, and first-flush stem and leaf tissues the following growing season, were not primary sinks for labeled photosynthates stored in root tissues despite the high radioactivity in root tissues. Root tissues appeared to deposit photosynthates in a layering process whereby the last photosynthates stored in new xylem were the first to be depleted during the initiation of a growth flush the following spring. There were more labeled photosynthates in roots of released seedling sprouts compared with non-released seedling sprouts, indicating increased vigor of released seedling sprouts in response to greater light availability. In contrast, stem and source leaf tissues of non-released seedling sprouts contained greater percentages of labeled photosynthates compared with released seedling sprouts, indicating either greater sink strength or poorly developed xylem and phloem pathways that created inefficiencies in distribution to root tissues. The 14C distribution coefficients confirmed the distribution patterns and provided additional information on the important sinks in released and non-released cherrybark oak seedling sprouts.