**2.2 Meeting energy and nutrient requirement**

The calculation of the ration by means of a computer program and table values must be preceded by an assessment (sensory testing, laboratory analyses), especially in the case of farm-produced feedstuff, as the nutrient content of feed can vary in a high range. This often results in discrepancies between calculated and actually fed rations, which give rise to complaints (see **Table 3**).

Often the rations had insufficient fibre content (< 16%) and at the same time very high starch and sugar content (in total > 300 g/kg dm). This feeding situation involves the risk of rumen acidosis. During the dry period, the animals were often oversupplied with energy. A possible fatty degeneration associated with this is undesirable, especially around the time of birth. In almost 20% of the samples, elevated mineral content was detected, which is contrary to the DCAB concept and involves the risk of milk fever.


**Table 3.**

*Criticism of rations for cows during lactation and dry period.*

Microbial fermentations during silage preparation not only influence the energy and nutrient intake of cows, but - depending on the amount and proportional composition - also milk yield and composition [13].

For the assessment of ensiling success and protein intake via fresh and preserved green fodder, the pure protein content provides important information (see **Table 4**).

If ensiling is only insufficiently successful, proteolytic processes can lead to protein degradation [14]. The result is reduced pure protein content, which - if only the crude protein content of the fresh and preserved green fodder is assessed - can lead to an incorrect assessment of the protein supply of the dairy cow (see **Table 5**).

Grass silages with a low true protein percentage in the total crude protein are supposed to contribute to the aetiology of a disease that is described as "factorial disease of dairy herds" or a higher incidence of fertility disorders, respectively [15].

During such proteolyses, biogenic amines are produced, among other things, which significantly influence the acceptance of a feed. Gamma-aminobutyric acid (GABA) is the so-called lead substance, the analytical detection of which can be carried out quickly and without great effort in the laboratory. GABA correlates closely with the pure protein level of a silage (see **Figure 3**) and thus gives a first impression of the silage quality. It is also known from feeding trials that GABA contents >7 g/kg dry matter lead to a massive reduction in feed intake [15, 16].

In the case of inhomogeneous mixtures (insufficient mixing, strongly inhomogeneous particle lengths of the individual ingredients), the cows can select more palatable components (e.g. maize silage), so that - despite a balanced ration calculation on paper - there can then be insufficient fibre and simultaneously higher starch/sugar intakes [17].


### **Table 4.**

*Crude protein and pure protein levels in fresh and preserved green fodder.*

### *Nutrition of the High-Yielding Dairy Cow DOI: http://dx.doi.org/10.5772/intechopen.99438*


**Table 5.**

*Pure protein content in grass silage\* of high or poor ensiling quality.*

### **Figure 3.**

*GABA-levels in dependence of the pure protein level of grass silages.*

A Total Mixed Ration (TMR) fulfils this requirement offering a simultaneous amount of richly-structured fibre and energy-rich components at the same time. But even if a homogenous and well-balanced feed mixture is offered the chemical composition (especially starch and fibre content) might differ between the offered and the actually ingested feed due to a selective feed intake behaviour in cows. In order to investigate this aspect 158 cows (Holstein Frisian) were split into two groups (group A, n = 76, TMR: 30.0 kg corn silage, 11.0 kg grass silage, 5.0 kg concentrate, 3.0 kg soybean meal, 2.4 kg alfalfa; Group B, n = 82, TMR: 29.0 kg corn silage, 11.0 kg grass silage, 3.6 kg concentrate, 2.0 kg soybean meal, 2.0 kg alfalfa). Starch and crude fibre were analysed using conventional methods. Measurement of particle size distribution followed recommendations of a commercial forage particle separator (Shaky 4.0, Wasserbauer, Waldneukirchen, Austria), consisting of three sieves with hole diameters of 19, 8 and 4 mm besides a collection tray for particles <4 mm.

Already in the first 30 minutes after feed offer a selective feed intake behaviour could be observed (see **Table 6**).

The distribution of particle sizes at the particular points of time as well as the chemical analysis of the feed suggest that the dairy cattle preferably ingest certain nutritious components (here probably corn silage). This selective feed intake behaviour implies the risk of SAARA due to the high starch and low fibre content in the actually ingested feed. The presented results show that selective feed intake is a non-negligible factor in dairy cattle nutrition. A synchronised intake of crude fibre and starch is not ensured even if the feed is offered homogenously. To avoid this


**Table 6.**

*Development of particle size distribution and crude and fibre level in a TMR in the period following feed offer.*

selection all components would have to have identical particle sizes (as practiced with the compact-TMR or shredlage). The question is, however, if the cows would still show a physiological rumination behaviour under those conditions.

For decades, the question of the desirable/necessary supply of structured fibre to dairy cows (including cattle) has been the focus of animal nutrition science. Against this background, in 2014 the assessment of rations for dairy cows with regard to "fibre supply" was changed to a new system, namely the "physically effective NDF" (peNDF; [18]). The innovative feature of this concept is the unification of two criteria previously treated separately, namely.


by multiplying the result of the sieve analysis (%, mass fractions) by the NDF content in the total ration (% of DM). According to previous studies and experience, a TMR should contain >18% peNDF>8 or > 32% peNDF>1.18 in the total DM to achieve optimal structural supply in dairy cows [19].

In feeding practice, the "shaker box" (so-called Penn State Particle Separator) offers an important tool for assessing the particle size distribution of a ration and, together with the NDF content, also for assessing the "structural effectiveness" of a ration. In our own investigations, however, it was shown that this approach is subject to various errors (**Figure 4**).

In addition to the mesh size of the sieves and the dry matter content of the silage (moist silage tends to stick together and thus gives the impression of longer particles), the result also depends to a large extent on the person carrying out the analysis. If an identical grass silage is examined by different persons, there is a very high scattering of the results.

### **2.3 Assessment of the feeding situation on the farm**

A frequent animal welfare-relevant problem in the feeding of dairy cows is the insufficient intake of fibre-rich coarse feeds or the lack of synchronicity in the rumen. Consumption of sufficient quantities initially requires the production of

## *Nutrition of the High-Yielding Dairy Cow DOI: http://dx.doi.org/10.5772/intechopen.99438*

### **Figure 4.**

high-quality grass silage and hay. However, studies from practice show that these often have higher contents of spoilage-indicating microorganisms (e.g. yeasts), sand, less palatable components (e.g. velvet grass) and ingredients (e.g. gammaaminobutyric acid) or even just an unfavourable low dry matter (DM) content [7]. If these are mixed into a total mixed ration, the actually realised DM intake falls short of the expected one and the cow is sometimes not sufficiently supplied with energy and nutrients.

The factors influencing the DM intake of the dairy cow and thus ultimately also the performance are manifold and are summarised in the following **Table 7**.

A suitable indicator to check whether feeding is in line with animal welfare is the recording of feed intake quantities. Here the question arises as to whether the quantities of feed presented via the feed mixer and the quantities of concentrated feed correspond to the herd size. However, this approach considers the herd as a whole and not the individual animal. The same applies to the milk yield data, which


### **Table 7.**

*Factors influencing the dry matter intake of dairy cows.*

provide conclusions on the supply of energy and nutrients (protein, fibre). Feedback from the slaughterhouse (e.g. increased incidence of fatty liver or liver abscesses) allows an assessment of the feeding situation on the farm, also under animal welfare aspects. For the assessment of the individual animal, the assessment of the Body Condition Score (BCS), which is also a component of the Animal Welfare Quality® Assessment protocol reviewed at PHÄNOMICS, is a suitable method. This procedure enables an assessment of the quality of the husbandry system from the animal's point of view. This would also satisfy another legal regulation of the Animal Welfare Act (§ 11, para. 8), which reads: "Anyone who keeps farm animals for commercial purposes must ensure through in-house inspections that the requirements of § 2 are met. In particular, he shall collect and evaluate appropriate animal-related characteristics (animal welfare indicators) for the purpose of his assessment that the requirements of § 2 are met." Thus, the livestock farmer cannot escape the responsibility to continuously check the feeding of his animals under animal welfare aspects (cross compliance; Directive 98/58 Annex No. 2; TierSchNutztV § 4 para. 1).
