Hypomagnesaemia in beef cows wintered in Ontario.

A field experiment was undertaken in northern Ontario in order to assess the magnesium status of beef cattle raised in the area. Magnesium status was assessed using several criteria including blood and urine magnesium levels, and bone biopsy samples. Eighteen groups each containing four pregnant Shorthorn beef cows were used. Each of the following three mineral feeds were offered to six groups throughout the experiment: a mineral feed without magnesium, a mineral feed containing 8% magnesium in the form of magnesium oxide and the third containing sequestered magnesium with a magnesium level of about a tenth of that in the mineral feed containing magnesium oxide. During the winter, when the cows were housed indoors, they were fed grass silage. Six groups, two of each mineral feed, remained indoors throughout the summer. The other 12 groups were turned out to pasture on May 25 and continued receiving the appropriate mineral feed. There were no differences in serum magnesium owing to magnesium-supplementation treatments observed at any time during any experiment. Serum magnesium levels fell drastically in all groups before the cows were released to pasture, implying that the hypomagnesaemic condition was attributable to the stress of yarding. The rate of recovery from hypomagnesaemia was slower in the cows released to pasture than in those kept indoors. Urine samples from cows returned to the pasture were indicative of low magnesium status. At the end of the experiment, the magnesium levels in the bones of the housed animals were higher than for those on pasture. In spite of severe cases of hypomagnesaemia, no clinical signs of this metabolic condition were observed.     

"增奶威"饲喂奶牛的效果试验

选择中国荷斯坦泌乳牛饲喂增奶威活性饲料添加剂。结果表明:增奶威可提高产奶量5-5.8%,增加乳脂率0.04%,牛奶中的体细胞数下降57%,胎衣滞留比率降低,投入产出比达到1:3.8。     

奶牛隐性乳房炎发生规律的调查分析

奶牛乳房炎作为奶牛疾病中发生率最高的疾病之一，一直困扰着奶牛业，成为影响其经济效益及发展的主要因素之一。多数乳房炎在临床上不表现症状，必须借助生化检验或细菌检验方可查出异常，这一类乳房炎称为隐性乳房炎。隐性乳房炎发病率极高，据北京、上海、广州和哈尔滨等地的调查结果表明，奶牛隐性乳房炎发病率为10％～40％，西欧部分经济发达国家奶牛隐性乳房炎发病率也高达25％。     

Changes in walking parameters of milking cows after hoof trimming

We examined the walking parameters of milking cows in relation to hoof trimming. The hooves of eight Holstein cows were trimmed. Two days before and after the hoof trimming, walking behavior, limb angles, back posture and vertical movement of the back while walking were measured. Walking rate (1.27 vs 0.87 m/s; P = 0.003), step length (1.46 vs 1.33 m; P = 0.009) and stepping rate (0.78 vs 0.65 steps/s; P = 0.046) were found to increase significantly after hoof trimming. Limb angles at the start and end of the support phase changed significantly after hoof trimming, thus indicating an improvement in the ‘on tiptoe’ appearance. The parameters relating to backline indicated that the marked arched shape of the back diminished after hoof trimming. Before hoof trimming, the positions of the withers varied widely and irregularly while walking; however, it changed after hoof trimming as the sinusoid curve and the range of vertical movement of withers decreased significantly. Overall, it has been quantitatively indicated that walking characteristics are improved after hoof trimming. The parameters used in the present study are expected to be useful for monitoring the walking characteristics of cows.     

Association of automatic milking systems milking frequency in primiparous and multiparous cows with their yield and milkability

The aim of the study was to determine the association of automatic milking systems milking frequency (≤2.40, 2.41–2.80 and >2.80 times/day) in primiparous and multiparous cows with their daily milk yield and milkability. The analysis included of the milk production level and the interaction between milking frequency per day and daily milk yield. Regardless of the daily production level, most primiparous cows were milked 2.41–2.80 times/day and most multiparous cows >2.80 times/day. Higher daily milk yield and a more favourable effect of increasing milking frequency on this parameter were observed in multiparous cows, with an increase from 29.7?kg (milking frequency ≤2.40 times/day) to 31.1?kg milk (>2.80 times/day). In primiparous cows, this increase was smaller and amounted to 0.8?kg milk (from 29.2 to 30.0?kg).     

Hypomagnesaemia in cattle

Leptospirosis is an important animal and human health problem in New Zealand, and the epidemiological and ecological aspects of infection in domestic species and free-living species are described. The characteristics of infection with a particular serovar are often considerably different in different species of animal and primary epidemiological investigations involve differentiating between maintenance-host populations and accidental-host populations for the serovars present in a particular ecosystem.

Cattle and pigs are maintenance hosts for hardjo and pomona respectively. Balcanica is maintained by possums (Trichosurus vulpecula) and ballum is maintained by the house mouse (Mus musculus), ship rat (Rattus rattus) and hedgehog (Erinaceus europaeus). In some regions, foci of copenhageni infection are maintained by Norway rats (Rattus norvegicus). Each serovar shows a high degree of parasitic adaption to its maintenance-host species and this is reflected in the nidality of leptospirosis in intensive farming environments. Accidental infections in domestic animals and man are the consequence of ecological associations with maintenance-host populations for particular serovars.

Control of leptospirosis in domestic animals depends on decreasing the prevalence of infection with serovars maintained within populations of domestic animals, and decreasing the degree of ecological association with free-living maintenance-host populations. Vaccination of cattle against hardjo. will considerably reduce the prevalence of infection in vaccinated herds and therefore decrease the prevalence of accidental hardjo infections in man.     

Detection model for mastitis in cows milked in an automatic milking system

Automated detection of diseases (such as mastitis) in dairy cows might be an alternative for detection by observation during milking - especially when using an automatic milking system (AMS). An outline of a detection model is given. This detection model includes time-series models for two variables (milk yield and electrical conductivity of milk), with interpolation on previous values. The model is flexible in the number of variables actually used. Parameter values and the residual variances are updated by linear regression after each milking. Alerts for mastitis are given when the residuals fall outside given confidence intervals. A data set with 111 cows for 16 months (on average, 58 lactating cows per day) was used to test the model. Depending on the chosen confidence interval, 42-44 out of 48 cases of clinical mastitis were detected; the remaining cases were not detected because not all data needed were available. These results were better than the results obtained with the model usually used on the farm. The number of false-positive alerts depended on the chosen confidence interval and was higher than the number found with the model usually used.