Deviation Of Nutrient Intake Of Lactating Cow Herds Fed Total Mixed Ration: Reason Analysis And Effects On Production Performance

At present, the large and medium-sized dairy farms in our country have adopted the total mixed ration(TMR) feeding technology. Compared with traditional feeding methods, TMR has obvious advantages, which can provide stable and balanced nutrients for rumen microorganisms, optimize rumen function and improve nutrient utilization efficiency.However, in China, there are many problems in the application of TMR technology, such as the inaccuracy of the diets, the imbalance of nutrient intake and so on, which will affect the health and production performance of dairy cows.This experiment analyzed the reason for deviation of nutrient intake of lactating cow herds fed TMR and the effects on production performance. Thirty cow herds with high milk yield were chosen and sampled for 5 days per herd. TMR and refusal feed samples were collected to assess nutrient composition and particle size distribution, and the coefficients of variation(CVs) of indexes were calculated. Milk yield was recorded, and milk sample was detected for milk composition. A multiple linear regression analysis between CVs of nutrients/particle sizes and production performance of cow herds was carried out. The results showed as follows: net energy for lactation(NEL) and the contents of crude protein(CP),NDF? ADF, microbial protein(MCP), ruminal undegradable protein(RUP), ruminal balance of energy and nitrogen(RENB), small intestinal digestible protein(DCPSI) and calcium(Ca)of TMR for 30 cow herds were 6.56MJ/kg, 16.22%, 35.71%, 21.38%, 77.84g/kg, 92.15g/kg,14.77g/kg, 104.04 g/kg and 1.43% respectively, among which NDF(1.94%), Ca(0.57%),RUP(5.03g/kg) and RENB(6.95g/kg) were higher than formula target values, and CP(-0.36%), ADF(-1.54%), NEL(-0.12MJ/kg), MCP(-7.71g/kg) and DCPSI(-2.12g/kg) were lower than formula target values(positive value indicate increase, and negative value indicate decrease). During the observation period, CVs of RUP [( 16.26±7.10) %], MCP[(22.78±13.38)%], RENB [(64.29±34.29)%] were more than 10%, and those of the other nutrients were less than 10%. CVs of long, medium, short and fine particles were(15.78±9.25)%,(9.12±7.86)%,(6.00±4.00)% and(11.15±9.62)%, respectively. The regression analysis showed that variation of TMR nutrients and particle sizes affected milk yield and milk composition. Every 1-percentage-point increase in CV of NEL resulted in decreasing of 3.662 kg/d for milk yield. Every 1-percentage-point increase in CV of long particles resulted in decreasing of 0.124 kg/d for milk yield and increasing of 0.012% for milk fat percentage.The conclusions are as follows1. The reason for difference between TMR nutrient intakes of lactating cows and formula nutrients lies in inaccurate feeding, unstable processing quality, mixing uniformity,and feed sorting.2. The stability of TMR processing quality can affect milk yield and milk composition,among which the variation of refusal rate, long particles, NEL, DCPSI and RENB affects milk yield, and that of long particles and RUP influences both milk yield and milk fat percentage.3. In order to improve the production performance of the herd, the analysis of feed raw materials should be regularly conducted to improve the accuracy and precision of the ingredients.