The extent of the usefulness of a lactation model depends on how well it succeeds in imitating the biological lactation process and how well it adjust for environmental and other factors that could influence production. Therefore, the objective of this study was to compare five different lactation curve models (Wood, Cobby and Le Du, Wilmink, Exponential and Parabolic Exponential model), and to find the best model that provided a good description of the lactation curve of Jersey cattle herd. Data used in this study were the first to seventh lactation official milk yield records from monthly recording of 3 630 lactations between 1984 and 2008 in the farm. The results showed that Wood model which has minimum residual standard deviation (3.562), maximum adjusted R 2 value (91.6 %) and maximum persistency value (93.3 %) performed the best fit to the data and allowed a suitable description of the lactation curve. It was concluded that the Wood model provided accurate estimates of milk yield for all lactation numbers because this model was found to be more superior to the other models. Consequently, the usage of Wood model would provide some useful information on genetic improvement of the Jersey breed under pasture-based dry seasonal production systems.
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Carbonic anhydrase (CA) enzymes have been shown to play an important role in ion transport and in pH regulation in several organisms. Despite this information and the wealth of knowledge regarding the significance of CA enzymes, few studies have been reported about bee CA enzymes and the hazardous effects of chemicals. Using Apis mellifera as a model, this study aimed to determine the risk of pesticides on Apis mellifera Carbonic anhydrase enzyme (Am CA). CA was initially purified from Apis mellifera spermatheca for the first time in the literature. The enzyme was purified with an overall purification of ∼35-fold with a molecular weight of ∼32 kDa. The enzyme was then exposed to pesticides, including tebuconazole, propoxur, carbaryl, carbofuran, simazine and atrazine. The six pesticides dose-dependently inhibited in vitro AmCA activity at low micromolar concentrations. IC50 values for the pesticides were 0.0030, 0.0321, 0.0031, 0.0087, 0.0273 and 0.0165 μM, respectively. The AmCA inhibition mechanism of these compounds is unknown at this moment.
Dairy records, containing 1269 lactation record of 462 Jersey dairy cows collected over 16 years, from an agricultural state farm were used. Data for reproductive performance of cows were also collected. Means of the herd for lactation milk yield, calving interval, days open, interval from calving to the first insemination, lactation length, gestation length and dry period were 3195.7±20.2 kg, 366.6±1.7 d, 92.9±1.6 d, 78.0±1.3 d, 301.7±1.1 d, 275.2±0.2 d and 69.3±0.8 d, respectively. The effect of calving season (winter, spring, summer and autumn) on reproductive performance for high, low and moderate milk-yield cows was investigated. Calving season affected the days from calving to first insemination in high and moderate yielding cows (P<0.001) while didn't affect low yielding cows. In summer, days open in high yielding cows were 35 days longer compared to winter season (P<0.001) as observed for moderate yielding cows (P<0.01). In high yielding cows, calving interval was 18 days longer in spring compared to winter calving season. Calving season also affected the first service conception rate in high yielding cows (P<0.05). Services per conception in autumn were lower than the other seasons (P<0.001). In conclusion, high yielding dairy cows need more attention in summer season with respect to body condition score, dietary energy: protein ratio, uterus health and elimination of heat stress, to get more profit in dairy farm.
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