Sirvi Autor "Jonkus, D." järgi
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Kirje Effect of dietary crude protein concentration on milk productivity traits in early lactation dairy cows(2021) Ruska, D.; Jonkus, D.The evaluation and control of nitrogen balance at the farm and its relation to milk productivity traits are becoming essential in dairy farming. Increasing in milk productivity farmers tend to increase protein content in feed. The research complied into three (A, B, C) dairy cow groups (8 cows in each group) with LB and HM breed’s cows in the early lactation period divided into three phases (I, II, III) from 10 till 30 lactation days and lasting to 90 lactation days. Each group cows were feeders with total mixed ration (TMR) with different CP content (approx. 17.0%; 16.0%; 15.0% accordingly). The amount of feed consumed by each cow were recorded and feed samples collected during the study. Feed samples were analysed for CP and other feed quality descriptive traits. Milk yield ( kg d -1 ) and milk samples were collected at day 21 of each phase for analysis. Milk samples were analysed for fat (%), total protein (%), casein (%), and urea content (mg dL-1 ). The statistical analyses were conducted using ANOVA and descriptive parameters. To evaluate the feed CP conversion efficiency estimated part of that in the yield of milk protein for each cow and on average for the study group in each study phase. The conversion efficiencies of feed CP in milk were ranged from 28.5% to 40.7% in study phase I, and from 33.0% to 39.9% in phase II, and the differences were statistically significant. In phase III, the range from 30.4% to 36.3% were not statistically significant. The objective of this study was to evaluation of feed protein conversion efficiency for dairy cows in the early lactation phase and define the optimal crude protein (CP) content in the feed.Kirje Evaluation of feed conversion efficiency for different dairy cows breeds by milk yield, milk content and faecal amount(2020) Ruska, D.; Jonkus, D.; Cielava, L.The objective of this study was to evaluation of feed conversion efficiency for Latvian Brown (LB) and Holstein Black and White (HM) dairy cows breeds to define optimal crude protein (CP) content in the feed. In the research study were completed three (A, B, C) dairy cows group (8 cows in each group) with LB and HM breed’s cows in the early lactation period, from 10 till 30 lactation days. Each groups cows were feeder with total mixed ration (TMR) with different CP content (approx. 18.0%, 17.5%, 17.0% accordingly). In the research period were controlled the amount of feed fed and regularly collected feed samples. After 21 days feeding was controlled milk yield, collected milk samples for content testing, and faecal amount and samples. Milk samples were analysed for fat, total protein (%) and urea content (mg dL-1 ). Milk samples for content parameters were analysed in an accredited milk quality laboratory. The statistical analyses were performed with the SPSS program package. The results acquired show that in all studied parameters were not significant differences between study groups. To evaluate the feed conversion efficiency during the study, we used the energy corrected milk (ECM) and the feed dry matter content during research and calculated the coefficient for each cow individually and on average in the study group. Milk yield, protein and faecal amount were significantly different among breeds. Milk urea content was average 28.5 mg dL-1 for all LB breed cows in all groups, for HM breeds it was 23.6 mg dL-1 . These results show that LB breed cows did not converse feed proteins wholesome. Total milk and faecal amount were decreased in a group with CP 17% in feed by 10% and 7% accordingly. By using this data, the farmer may make evaluations and forecast of farming efficiency; cows breed preference and environmental threats.Kirje The influence of dietary inclusion of peas, faba bean and lupin as a replacement for soybean meal on pig performance and carcass traits(2018) Degola, L.; Jonkus, D.The effect of peas, faba bean and lupin seed inclusion in growing and finishing pig diets was evaluated. The control diet included soybean meal at 15%, but in the trial groups diets peas were 15 or 28%, faba bean 20 or 25%, lupin seed 12 or 15%, completely replacing soybean meal. Diets formulated to be isoenergetic for ME and with the same crude protein content. The faba bean and, especially, lupin seed meal inclusion in pig diets for growing per iod significantly reduced ADG P = 0.02 and 0.01 ), and G : F was also signi fi cantly influ enced ( P = 0.02 ) for pigs in lupin seed meal groups. There were no effects on finisher pigs average daily gain, inclusion peas or faba bean, daily gain were, respectively 892 ± 19 and 915 ± 11, 867 ± 12 and 828 ± 11, except lupin seed meal ( P = 0.04 ) inclu sion. There were no significantly effects on carcass quality and to pork chemical content, but pigs fed the diets with peas 28% and faba bean 25% had less of lean meat content, greater backfat thickness and internal fat than other groups which have a simil ar results. The muscle chemical content show that inclusi o n of pulses increased the total fat content in pork. In conclusion, results from this experiment suggest that pigs fed peas and faba bean have equal or slightly lower growth performance and carcass traits than pigs fed soybean meal, except lupin seed meal.Kirje Longevity and milk production efficiency of Latvian local breeds during last decades(2020) Jonkus, D.; Paura, L.; Cielava, L.The aim of the study was to analyse the longevity and the amount of energy-corrected milk (ECM) per day of local dairy cattle breeds Latvian Brown (LB) and Latvian Blue (LZ). The study was based on the data of LB genetic resources (LB) 1770 and LZ 921 cows, which were born from January 1st, 2000 till December 31st year 2015. Milk productivity and longevity of the LB and LZ cows were analysed by birth year periods: 2000–2005, 2006–2010 and 2011–2015. LZ culled cows lifespan was in average 2,762.8 ± 55.14 days, or 7.6 years and it was significantly higher than for LB. The average lifespan of LB culling cows was 6.7 years. There are cows which had closed 7–12 lactations. On average, cows’ lifespan decreased during analysed period. In general, LZ cows are characterized by higher length of productive life and milking days. LZ cows produced more EC milk during their productive life; however, they had the lower milking day ECM productivity than LB cows.Kirje Trends in milk yield productivity and emissions from the dairy sector in Latvia(Estonian University of Life Sciences, 2023) Paura, L.; Berzina, L.; Degola, L.; Aplocina, E.; Kairisa, D.; Jonkus, D.; Skiste, O.Dairy cow productivity continuously increased in Latvia in recent years. Despite decreasing numbers of dairy cow population dairy farms have been identified as an important source of greenhouse gas (GHG) emissions. Dairy sector emissions create the largest share of enteric fermentation emissions as well as emissions from manure in housing facilities, during long-term storage and field application within agriculture sector total emissions. The main objective of this study is to present the results of trend analysis in the productivity of the dairy sector and corresponding emission in Latvia. Research is focused on analysis of dairy cow productivity and feeding strategies to quantify the effect of increasing milk yield on GHG emissions. In the framework of this research, emissions were calculated and evaluated for low and high productivity dairy cows according to the methodology of ‘2019 Refinement to the 2006 Guidelines for National Greenhouse Gas Inventories’. During the last decade dairy cow productivity in Latvia has increased and the average milk yield in standard lactation was 8,320 kg per year in 2021. It was observed that 60% of the total number of dairy cows met the requirements of a high-productivity system, while 40% of the dairy cows belonged to low-productivity systems in Latvia. Research results show that total GHG emissions for high-productivity system can reach 5.3 kt CO2 eq. per 1,000 cows per year, however, for low-productivity system the total amount of emissions does not exceed 3.1 kt CO2 eq. per 1,000 cows.