Dairy cow nutrition in organic farming systems. Comparison with the conventional system

Abstract

The energy supplied by the high-forage diets used in organic farming may be insufficient to meet the requirements of dairy cattle. However, few studies have considered this problem. The present study aimed to analyze the composition of the diets and the nutritional status (focusing on the energy–protein balance of the diets) of dairy cattle reared on organic farms in northern Spain, which are similar to other organic farming systems in temperate regions. Exhaustive information about diets was obtained from organic (ORG) and representative conventional grazing (GRZ) and conventional no-grazing (CNG) farms. Samples of feed from the respective farms were analyzed to determine the composition. Overall, the diets used on the ORG farms were very different from those used on the CNG farms, although the difference was not as evident for GRZ. The CNG farms were characterized by a higher total dry matter intake with a high proportion of concentrate feed, maize silage and forage silage. By contrast, on ORG and GRZ farms, the forage, pasture and fibre intake were the most important variables. The ration used on ORG farms contained a significantly higher percentage of ADF and lower organic matter (OM) content than the rations used in both of the conventional farming systems, indicating that the diets in the former were less digestible. Although the protein concentration in the diets used on the grazing farms (ORG and GRZ) was higher than those used on CNG farms, the protein intake was similar. The results indicated an imbalance between energy and protein due to the low level of energy provided by the ORG diets, suggesting that more microbial protein could be synthesized from the available rumen-degraded dietary nitrogen if rumen-fermentable OM was not limiting. The imbalance between energy and protein led to a reduced amount of total digestible protein reaching the intestine and a lower milk yield per kilogram of CP intake on the ORG farms. In order to improve the protein use efficiency and consequently to reduce the loss of nitrogen to the environment, organic farming should aim to increase the energy content of cattle diets by improving forage quality and formulating rations with more balanced combinations of forage and grain.

Influence of beef genotypes on animal performance, carcass traits, meat quality, and sensory characteristics in grazing or feedlot-finished steers

“…Although the crude protein of the diet was greater in GRASS, forages usually present an unbalanced protein: energy ratio. This is mainly because the energy content is low in forages (approximately 61% compared to 79% in TMR), which is the main limitation to achieving optimal animal performance in grazing diets ( Orjales et al, 2019 ; Teobaldo et al, 2020 ). The efficiency of energy utilization decreases with high CP due to the energy cost of urea synthesis from excessive ammonia in the liver ( NRC, 2016 ).…”

“…Although the quality of forage is an important factor for crude protein levels, the species cultivated also change the nutritional value of the diet consumed by animals on pasture. For example, pastures containing clover are rich in N whereas CP levels of perennial ryegrass are lower than that of the leguminous species ( Van Vuuren and Dasselaar, 2006 ; Orjales et al, 2019 ). Our pasture was rich in legume, since it contained more than 20% of clover and 10% of alfalfa ( Figure 2 ), which explain the high values of CP observed.…”

Organic Milk Production and Dairy Farming Constraints and Prospects under the Laws of the European Union

“…By comparing the forage base available in organic and conventional systems, it can be concluded that, in organic systems, the energy concentration of forage is much lower than in conventional systems [84,85]. This is mainly due to the limited use of corn silage and the use of hay in winter feed, which is in line with the general assumptions of organic farming.…”

Organic versus Conventional Raw Cow Milk as Material for Processing

“…Moreover, at least 60% of the dry matter in the feed ration should be roughage, green fodder, dried fodder, or silage. Pastures should be maximized accordingly to their availability in different seasons of the year [31][32][33]. The differences in non-conventional and organic feeding result mainly from the diversity of available vegetation in pastures, mainly in the spring and early summer.…”