Effect of dietary phosphorus content on milk production and phosphorus excretion in dairy cows

Background：Phosphorus（P） supplementation is costly and can result in excess P excretion.This study investigated the effects of reducing dietary P on milk production and P excretion in dairy cows over a full lactation.Method：Forty-five multiparous Holstein dairy cows were divided into 15 blocks according to expected calving date and previous milk yield,and assigned randomly to one of the three dietary treatments：0.37,0.47,and 0.57%P（DM basis）;these P levels represent the NRC recommendations,Chinese recommendations,and the amount of dietary P commonly fed by Chinese dairy farmers,respectively.Average daily feed intake was calculated from monthly data on feed offered and refused.Milk yields of individual cows were recorded weekly,and milk samples were taken for analysis of protein,fat,solids-not-fat,lactose,and somatic cell count.Blood samples were collected on days-6,-3,0,3,6 relative to calving,and then monthly throughout lactation,and analyzed for P and Ca concentrations.Spot samples of feces and urine were collected for 3 consecutive d during weeks 12,24,and 36,and P concentrations were analyzed.Reproduction and health data were recorded.Results：Dietary P did not affect dry matter intake or milk yield（P〉 0.10）.Milk fat content was slightly higher in cows fed 0.37%P than in cows fed 0.47%P（P = 0.05）.Serum concentrations of P and Ca did not reflect dietary P content（P〉 0.10）.Fecal and urinary P both declined linearly（P〈 0.05） as dietary P decreased from 0.57 to0.37%.Fecal P content was 25%less when dietary P was 0.37%compared to 0.57%.Health events and reproductive performance were not associated with dietary P content（P〉 0.05）.Conclusions：Lowering dietary P from 0.57 to 0.37%did not negatively affect milk production,but did significantly reduce P excretion into environment.

Application of Liquid Chromatography-High Resolution Time-of-flight Mass Spectrometry in the Detection of Raw Milk and Dairy Products

Milk and dairy products are more and more popular with consumers due to their various nutrients, and their quality and safety issues have always been concerned. Therefore, the development of rapid, accurate and simple screening techniques is of great significance. Liquid chromatography-high resolution time-of-flight mass spectrometry has high-resolution and high-throughput detection functions, and has gradually begun to be applied in the detection of milk and dairy products. This paper summarized the application of milk and dairy products in liquid chromatography-high resolution time-of-flight mass spectrometry, laying a foundation for the development of new methods.

Challenges in enriching milk fat with polyunsaturated fatty acids

Milk fatty acid composition is determined by several factors including diet. The milk fatty acid profile of dairy cows is low in polyunsaturated fatty acids, especially those of the n-3 series. Efforts to change and influence fatty acid profile with longer chain polyunsaturated fatty acids have proven challenging. Several barriers prevent easy transfer of dietary polyunsaturated fatty acids to milk fat including rumen biohydrogenation and fatty acid esterification. The potential for cellular uptake and differences in fatty acid incorporation into milk fat might also have an effect, though this has received less research effort. Given physiological impediments to enriching milk fat with polyunsaturated fatty acids, manipulating the genome of the cow might provide a greater increase than diet alone, but this too may be challenged by the physiology of the cow.

Effects of total replacement of corn silage with sorghum silage on milk yield,composition, and quality

Background： In the last years, difficulties occurring in corn cultivation（i.e., groundwater shortages, mycotoxin contamination） have been forcing dairy farmers to consider alternative silages. Some experiments conducted on lactating cows have proven that the total replacement of corn silage with sorghum silage did not reduce milk yield.However, this kind of substitution involves supplementing sorghum-based diets with grains, to compensate for the lower starch content of sorghum silage compared to corn silage. Change of silage type and inclusion of starch sources in the diet would influence rumen fermentations, with possible effects on milk composition（i.e., fatty acid profile） and coagulation properties. A worsening of milk coagulation properties would have a negative economic impact in Italy, where most of the milk produced is processed into cheese.This study was designed to compare milk composition and quality, with emphasis on fatty acid profile and coagulation properties, in dairy cows fed two diets based on corn or sorghum silage.Results： The sorghum diet reduced milk yield（P = 0.043） but not 4% fat corrected milk（P = 0.85）. Feeding sorghum silage did not influence milk contents of protein（P = 0.07） and lactose（P = 0.65）, and increased fat content（P = 0.024）.No differences emerged for milk concentrations of saturated（P = 0.61） and monounsaturated fatty acids（P = 0.50）,whereas polyunsaturated fatty acids were lower（P 〈 0.001） for the sorghum diet. Concentrations of n-6（P 〈 0.001） and n-3 fatty acids（P = 0.017） were lower in milk of cows fed the sorghum diet. Milk coagulation properties did not differ between the two diets, except the ＂a30＂（the curd firmness, expressed in mm, 30 min after rennet addition）, that was lower（P = 0.042） for the sorghum diet.Conclusions： Feeding a forage sorghum silage, properly supplemented with corn meal, as total replacement of corn silage maintained milk composition and did not influence negatively milk coagulation properties, which have a great economic relevance for the Italian dairy industry. Thus, silages obtained from forage sorghums could have a potential as substitute of corn silages in dairy cow diets.

Global warming potential associated with Irish milk powder production

Climate change is an ever growing issue and a major concem worldwide. Both producers and processors need to address the issue now by reducing, their carbon footprint. Additionally, if Ireland is to meet their climate and energy targets, as outlined in Food Harvest 2020, which outlines a range ot objectives for the Irish agricultural sector, the efficient use of resources and fuels within the industry will need to be increased. In Ireland, agriculture accounts for 29.2% of the total greenhouse gas powder, is examined in order to estimate the global warming potential （GWP） associated with its manufacture using life cycle assessment. A cradle-to-processing factory gate analysis, which includes raw milk production, raw milk transportation to the processmg tactory, its processing into eacla product and product packaging, is assessed in this study using data collected circa 2013. The factories surveyed processed approximately 24% of the total raw milk processed in the Republic of Ireland in 2013, which was 5.83 billion liter. The average total GWP associated with the manufacture of milk powder is 9.731 kg CO2eq·kg^-1 milk powder, which has a standard deviation of 2.26 kg CO2eq·kg^-1 milk powder, for the life cycle stages analyzed in this study. The most significant contributor to GWP is raw milk production （84%）, followed by dairy processing （14%）, with the remainder of the life cycle stages contributing approximately 2%.