Nutrient efficiency in Swedish dairy cows fed total mixed rations or partial mixed rations

Sammanfattning: The relatively poor economy in European dairy farming might be improved from efficient feeding systems and dietary management. Increasing herd sizes and transition to loose housing systems in Sweden, increases the possibilities for other feeding systems than separate feeding that is the traditional feeding system in Sweden. Other possible feeding systems are partial mixed ration (PMR) and total mixed ration (TMR), where the TMR system sometimes is associated with overfeeding and thereby increased environmental impact and high feed cost. Diets providing nutrients above or below animal requirements are considered as unbalanced, which in turn are associated with reductions in health, fertility and milk production. On the other hand, a balanced feed ration improves feed efficiency, nitrogen utilization and profitability. Feed efficiency is defined as kg energy corrected milk per kg dry matter intake in the present study, while nitrogen efficiency represents the nitrogen used for salable product in relation to total nitrogen intake. Separate feeding is well-known in Sweden, therefore the present study focused on TMR and PMR feeding systems, aiming for determining the feed efficiency, nitrogen efficiency and milk income over feed cost on commercial farms. The study was conducted during 24 April to 23 May 2013 and included visits to 20 selected dairy farms in the north of Sweden with PMR and TMR feeding sys-tems. Feed sampling, body condition scoring, feed ration formulation, feed intake, milk production parameters and feed cost were retrieved from the on farm visits. Feed samples were sent for analysis and used for calculations of average diet com-position of the herd, forage dry matter and total dry matter intake. Statistical anal-yses were performed using the software Minitab 17, where Pearson correlation, multiple regression and one-way ANOVA analyses were used for evaluation. Milk income was calculated from the official milk price first of May 2013 with adjust-ments for fat and protein concentration. Prices were received from farmers or the feed factories; however the price of forage and straw was estimated to 1.4 SEK/kg dry matter and 1 SEK/kg respectively. The results show a mean value of 1.35 and 1.43 kg energy corrected milk per kg dry matter intake for feed efficiency on farms practicing TMR and PMR feeding respectively, while the average for N efficiency was 28% and 29% for farms feed-ing TMR and PMR respectively. Milk income over feed cost averaged 45 SEK and 44 SEK for farms feeding TMR and PMR respectively. A positive correlation be-tween feed and nitrogen efficiency was determined, and feed efficiency was posi-tively correlated to profitability and negatively correlated to feed intake. Nitrogen efficiency was negatively correlated to dietary crude protein concentration. Milk income over feed cost was further positively influenced by milk yield. The use of TMR or PMR feeding systems did not affect the feed efficiency, nitrogen efficiency or milk income over feed cost. Improved feed efficiency seems to be associated with good health, productivity, profitability and reduced environmental impact. Further studies involving the relationship between feed and nitrogen efficiency would be interesting in order to identify the important factors for improved nitrogen efficiency at farm level.