Accuracy and homogeneity of total mixed rations processed through trailer mixer or self-propelled mixer, and effects on the yields of high-yielding dairy cows

Highlights

• Quality of total mixed ration (TMR) prepared by a trailer mixer (TM) or a self-propelled loading mixer (SPLM) was examined.

• The difference between the programmed and actual loaded forage feeds was greater for TM.

• There were differences in the chemical composition and homogeneity between the TMRs.

• Difference in distribution, but not homogeneity, of particle size was observed between the TMRs.

• Milk yield was greater and milk-fat content was lower in cows fed the SPLM TMR.

Abstract

Total mixed ration (TMR) quality depends on feed levels and values, and appropriate diet formulation, but also on diet preparation practice. We examined the accuracy and homogeneity of rations, as affected by the machinery used for TMR preparation, and their effects on dairy cow performance. Multiparous Israeli-Holstein cows (n = 216) were stratified into 2 groups, according to milk yields, days in milk, parity, and body weight; they were fed the same formulated TMR, prepared by either a trailer mixer (TM) or an self-propelled loading mixer (SPLM). To examine the accuracy of diet preparation we have recorded and analyzed 10 times the difference between the programmed and the actual loaded content (as fed matter) of each feed ingredient. For evaluation of the accuracy and homogeneity of the ration contents, the TMRs from 6 spots along the feeding trough were sampled at 10 time-points, and the samples were analyzed for DM, protein, ADF, aNDF and ash contents; the results were compared with the programmed values. On another 7 occasions, samples of the TMRs were taken from 3spots along the feeding trough for evaluation of the particle sizes distribution using the Penn State Particle Separator. The mean difference – in percentage units – between the programmed and actual, loaded concentrate feeds was similar (∼5.7 %) for both TMRs (SEM = 1.5; P = 0.98), but for forage feeds it was +17.6 and - 0.6 % (SEM = 3.7; P = 0.001), for TM and SPLM TMR, respectively. The mean differences of contents (in percentage units; DM basis) between the programmed and prepared diets, were: for protein – 1.1 and 0.9 % (SEM = 0.2, P = 0.25), for ADF – 2.7 and 1.3 % (SEM = 0.2, P < 0.001), and for aNDF – 6.9 and 5.7 % (SEM = 0.2; P < 0.002), in TM and SPLM TMRs, respectively. Except for ash content, the chemical-composition homogeneity was greater in the SPLM TMR than in the TM TMR. The fraction of particles>19 mm was 2.9 percentage units greater (P = 0.04), and that of particles ≤8 mm was 3.3 percentage units less (P = 0.04) in the TM than in the SPLM ration. The milk yield was 1.2 kg/d greater (2.7 %) in cows fed the SPLM than in those fed the TM TMR (P < 0.001), and the milk-fat content was 0.8 g/kg greater in cows fed the TM TMR (P = 0.03). In conclusion, the accuracy and homogeneity of the SPLM-prepared TMR were greater than those of the TM-prepared TMR, which influenced the cows’ performance. This study demonstrates the importance of the preparation machinery for TMR quality, indicating that more attention should be dedicated in practice and research to the methods used for TMR preparation.

Introduction

In light of increasing dairy-cow yields, most dairy herds in Israel and elsewhere use a total mixed ration (TMR) feeding system; these include about 90 % of large dairy herds in the USA (Schingoethe, 2017), and almost all dairy herds in Israel. There are many advantages of TMR feeding over component feeding as: minimizing the sorting and separation of feed ingredients by the animal, which ensures that each bite takes a uniform nutritionally balanced feed; high production (Ferland et al., 2018); possibility of incorporating unpalatable by-products, etc. In practice there are three types of rations: i) the programmed ration, ii) the prepared ration, and iii) the consumed ration. The programmed ration is formulated by using least-cost computerized software, based on lab analysis and database information from the literature regarding the available feed ingredients (grains, meals, forages, etc.), to meet the cow's estimated requirements. The prepared ration depends on the machinery used for mixing and delivering the ration, the quality of the operator, the control system, loading sequence, etc. The consumed diet depends on accuracy and homogeneity of the ration, feeding management, stocking density, etc.

Efforts to improve TMR formulation have addressed the quality and contents of feed ingredients, and the machinery involved in TMR preparation and delivery; but the accuracy and homogeneity of the resulting TMR – which are very important factors influencing the health and productivity of the cow – were rarely examined. Furthermore, inclusion in the modern cow's ration of a variety of forages, grains, meals, byproducts, minerals, and feed additives, all with differing physical properties, makes attention to these factors more challenging. Use of high-quality feed ingredients that are appropriately formulated in terms of nutritional and feed values does not guarantee an accurate and homogenized ration. The programmed ration can be adequate and appropriate for a cow’s requirements, but if the diet is not prepared precisely or the nutrition management is not appropriate, the animal may end up consuming an unbalanced diet.

The machinery used for ration preparation is an essential factor in determining the quality of the resulting ration. The TMR feeding system is based on a mixer feeder that can be loaded either by a front loader (loader) or by a special mechanism that is an integral part of the mixer/feeder. Trailer mixer (TM) feeders and stationary mixer feeders are loaded by a loader, whereas the self-propelled loading mixer (SPLM) feeder is loaded by a special mechanism that is an integral part of the SPLM. As aforementioned, accuracy and homogeneity of the resulting TMR were rarely examined. We hypothesized that the TMR’s quality prepared by TM or SPLM will be different, mainly because of the different loading system, which may affect the cows’ performance. Therefore, in the present study, for the first time, we examined the accuracy and homogeneity of TMRs prepared by using a TM or SPLM, and assessed the effects on yields of high-yielding dairy cows.