Morphometric analysis of involuting bovine mammary tissue after 21 or 42 days on non-suckling

Mammary gland involution was morphologically evaluated 21 or 42 d after prevention of suckling of one udder half in 10 crossbred beef cows. Parenchymal tissue was taken from lower, middle and upper zones of each quarter from the teat to the ventral body wall. Udder halves, trimmed of extraparenchymal tissue, were weighed and used for DNA determination. DNA content was reduced 50 and 64% after 21 and 42 d of involution. However, the percentage of tissue occupied by epithelium was similar in suckled and nonsuckled glands. Well-differentiated cells, typical of suckled glands, were rarely observed in nonsuckled glands. Alveolar structure was evident in nonsuckled glands, but the number of cells per alveolar cross-section was reduced (30 vs 22). Unlike in suckled glands, there was a marked gradation in classification of epithelial cells across zones in involuting glands. For example, nearly 10% of the epithelium was well-differentiated in the tissue from the upper zone, whereas no well-differentiated cells were found in the lower zones. Regression of the mammary parenchyma does not occur uniformly through the udder, so use of single biopsy to study involution should be avoided. Presence of alveoli after 42 d indicates that redevelopment of the udder with subsequent lactations is less dramatic than suggested from study of other species.     

Management of inappetant sheep during export by sea

In the first of 2 experiments, a simulated voyage was conducted to examine the effects of various treatments on bodyweight change and feeding frequency of inappetant sheep at the end of lot-feeding (non-feeders). The treatments, applied during simulated shipping, were: normal quantities of feed and length of troughs; extra trough length; extra feed. Adult Merino wethers (n = 108) were used in each treatment. A voyage to the Middle East was then conducted to establish whether shipboard mortality could be reduced by separating non-feeders (n = 305) from feeders (n = 5,620) late in the feedlot hase and housing the groups separately aboard ship. A control group of non-feeders (n = 215) mixed with feeders (n = 5,732) was used for comparison. Bars (marker bars), containing a coloured dye, were attached to feed troughs to mark sheep that fed. Most non-feeders (82%) began eating when placed in shipping pens in both studies. However, there was no significant difference in percentage of sheep that fed between non-feeders given extra trough length or extra feed compared with non-feeders given standard management at any stage of simulated shipping. There was no significant difference in mean bodyweights between treatment groups on days 1, 8 and 15 of simulated shipping. Differences in bodyweight on d 22 were probably associated with different levels of gut fill. Death rates were not significantly different in separated and control groups (1.1%, 0.9%, P = 0.6) in the voyage of 14 d to the Middle East.(ABSTRACT TRUNCATED AT 250 WORDS)     

桉树人工育种方法学

引言改良商业林的种植材料是一个长期不断的过程。种子最初是从自然林分和人工林的实生苗中采取;后来是采用林木选优,它是根据树木的特征,如材积、早期生长情况或抗病性来选择。可通过选出最好的基因进行组合,以进一行提高控制杂交群体增益。