Benefits and risks of antimicrobial drugs, used in food-producing animals, continue to be complex and controversial issues. This review comprehensively presents the benefits of antimicrobials drugs regarding control of animal diseases, protection of public health, enhancement of animal production, improvement of environment, and effects of the drugs on biogas production and public health associated with antimicrobial resistance. The positive and negative impact, due to ban issue of antimicrobial agents used in food-producing animals, is also included in discussion. As a double-edged sword, use of these drugs in food-animals persists as a great challenge.

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Benefits and risks of antimicrobial use in food-producing animals

The main objective was to determine the prevalence of intramammary infections (IMI) in dairy cows in Flanders, Belgium. Data were obtained from quarter milk samples of dairy herds subjected to a mandatory yearly screening of all lactating cows. A total of 178 668 quarter milk samples were collected at 1087 cross-sectional dairy herd screenings performed in three consecutive years. Of the dairy cows, 40% had at least one culture-positive quarter. More than 50% of all IMI were caused by non-aureus staphylococci. Streptococcus agalactiae is almost eradicated in Flanders, whereas Staphylococcus aureus was isolated from 18% of the culture-positive quarters. In addition, the distribution of mastitis pathogens in quarter milk samples from selected dairy cows with an elevated somatic cell count (SCC) is described. From 6390 cows with a geometric mean composite SCC ⩾250 000 cells/ml, nearly 65% had at least one culture-positive quarter. The majority of the IMI were caused by non-aureus staphylococci (41·1%), whereas Staph. aureus and aesculin-positive cocci were found in respectively 25% and 18% of the culture-positive milk samples. We conclude that more efforts are needed in the prevention and control of subclinical mastitis in Flanders. Non-aureus staphylococci are the predominant cause of IMI, warranting more research regarding the epidemiology and pathogenicity of those species.

Prevalence and distribution of mastitis pathogens in subclinically infected dairy cows in Flanders, Belgium.

https://jcp.bmj.com/content/jclinpath/30/11/1089.1.full.pdf

Theory and Practice of Histological Techniques

Sperm competition is now recognised as a potent selective force shaping many male reproductive traits. While the influence of sperm competition on sperm number is widely accepted, its effects upon sperm size remain controversial. It had been traditionally assumed that there is a trade-off between sperm number and sperm size, so that an increase in sperm number would result in a decrease in sperm size, under conditions of sperm competition. Contrary to this prediction, we proposed some time ago that sperm competition favours an increase in sperm size, because longer sperm swim faster and are more likely to win the race to fertilize ova. Comparative studies between species show that in many taxa such a relationship exists, but the consequences of an increase in sperm size may vary between taxa depending on the environment in which spermatozoa have to compete. We present new evidence showing that in mammals longer sperm swim at higher speeds. We also show that mean swimming speed is highly correlated with maximum swimming speed, so even if the fastest swimming sperm are more likely to fertilize, both measures are informative. When individuals of the same species are compared, ratios between the dimensions of different sperm components, as well as the shape of the head, seem better at explaining sperm swimming velocity. Finally, we show that mean and maximum sperm swimming speed determine male fertility. Other studies have shown that in competitive contexts, males with faster swimming sperm have higher fertilization success. We conclude that the available evidence supports our original hypothesis.

/pdf/implications-of-diversity-in-sperm-size-and-function-for-38og988qs0.pdf

Implications of diversity in sperm size and function for sperm competition and fertility

Predictors of success of semen cryopreservation in chickens.

During the last decade, several computer assisted sperm analysis (CASA) systems have been validated for canine sperm quality assessment. Regarding the impressive possibilities of these systems, further research is required to determine which CASA measurements are of clinical importance in canine andrology. In the present study, the sperm quality parameters obtained by the Hamilton-Thorne Semen Analyser (Ceros 12.1; HTR) were correlated with the body weight and the age of the dogs. Moreover, the sperm quality parameters of dogs with a different breeding history were compared. The sperm-rich fraction was collected from 111 dogs of 50 different breeds, which were presented at our department. Immediately after collection, the concentration, the total sperm output (TSO) and 13 different sperm motility and velocity characteristics were measured by the HTR. The percentage of live spermatozoa and the spermatozoal morphology were examined on eosin/nigrosin stained smears. Based on their breeding history, the dogs were divided in three groups: 'fertile' (n = 60), 'subfertile' (n = 17) or 'not used for breeding' (n = 34). Significant (p < 0.05) correlations were established between the body weight of the dogs and the TSO (r = 0.245) and velocity curvilinear (VCL; r = -0.220), respectively. The age was negatively correlated with the percentage of normal spermatozoa (r = -0.203; p < 0.05). The correlations with all the other evaluated sperm parameters were low and not significant. Significant differences between the 'fertile' and the 'subfertile' group were found for all of the evaluated sperm quality parameters (except for BCF, LIN, STR and MEDIUM). In conclusion, dogs tend to produce ejaculates with a lower percentage of normal spermatozoa with increasing age and dogs with higher body weights produce ejaculates with a higher TSO and a lower VCL. Significantly poorer sperm characteristics were found for dogs with lower in vivo fertility results.

Effect of body weight, age and breeding history on canine sperm quality parameters measured by the Hamilton-Thorne Analyser

tears may have been caused by direct physical damage from the areas of abnormal cartilage, or they may have occurred secondary to low-grade joint inflammation. Some direct physical relationship is possible, due to the fact that the lesions were seen in the lateral side of the joint and no medial meniscal lesions were seen. In one human study, magnetic resonance imaging (MRI) revealed lateral meniscal tears in some patients with osteochondritis dissecans in the lateral condyle (Yoshida and others 1998). In mature dogs presenting with pelvic limb lameness, stable stifles and radiographic evidence of stifle osteochondritis, a tear of the lateral meniscus may be present. An arthrotomy, arthroscopic or MRI evaluation may be warranted to obtain a definitive diagnosis and institute treatment. Piermattei and Flo ( 1997) suggested that 'meniscectomy helped the lameness'. However, a guarded prognosis should be given for a full recovery as, in this report, the lameness after surgery was resolved in only one dog and in the other two there was some improvement but the lameness was still intermittent.

Geert Hoflack

Papers

Effect of body weight, age and breeding history on canine sperm quality parameters measured by the Hamilton-Thorne Analyser

Aggressive angiomyxoma in a cow.

Elevated number of coliform bacteria in the bulk milk due to chronic Klebsiella oxytoca mastitis.

Het afscheuren van de navelstreng bij kalveren

Fertility in Belgian Blue bulls