NUTRITION ▶▶▶


The effect of intercropping on cattle feed, milk production and costs


What are the effects of various intercrops on the feed utilisation and milk production of dairy cows? And what is the best strategy for optimising intercropping systems? What is their economic impact? Let’s discuss these issues.


BY DR SALAH HAMED ESMAIL, FREELANCE JOURNALIST I


ntercropping is a husbandry system by which different crops are grown at the same time on the same area of land. The system has been practiced in many parts of the world in a variety of ways, depending on the pro-


ducer’s need, i.e., hay, silage, grazing, or green chop. As an agricultural practice, intercropping promotes yield stability because not all the crops in a mixed cropping system are likely to be equally affected by variations in weather condi- tions. Crops with different growth habits may also vary in their environmental requirements, leading to complemen- tary canopies and root systems. In some instances, they are able to exploit light, nutrients, and water more fully than monocultures.


The nutritional value of intercrops By intercropping soybeans with maize, for example, the mix- ture will be higher in crude protein (10-11% CP for maize-soy- bean intercrop vs. 8% CP for maize monoculture). The inter- crop will also deliver higher lysine and methionine values (219%) than maize monoculture. The increased production of quality protein and essential amino acids achieved by inter- cropping is of special importance in the nutrition of all classes of farm animals, including ruminants. Although ruminant ani- mals are thought to be less sensitive to protein quality and are able to overcome a dietary deficiency of essential amino acids such as lysine and methionine by synthesizing these ac- ids in the rumen, evidence with high-producing animals, par- ticularly dairy cows, suggests that optimum productivity can- not be obtained by feeding low-quality protein diets. This may be particularly true in areas known to be protein-defi- cient, such as many tropical and subtropical regions. The


greatest potential for intercropping is in these areas. In terms of mineral content, maize-soybean intercrops were found to be higher in calcium (0.7-0.8% vs. 0.2% for maize). The phos- phorus level of maize-soybean silage was slightly higher than for maize silage alone, but the higher calcium level delivers a ratio of 2:1 Ca:P, which is desirable for lactating cows. Planting soybean together with maize for silage will thus improve the protein and mineral content and will require less protein and mineral supplementation to meet the requirements of dairy cows, and so will deliver an economic advantage in the feeding programme.


Feed intake With most intercropping systems, no differences in feed in- take were noted, except in cases where the intercrops were preserved as silage. Intake may be reduced here to a varying extent, depending mainly on the crop variety and the pre-en- siling treatment used. In one study, the silage intake (kg dry matter per day) of dairy cows was 9.2 with grass silage and was reduced to 7.1 when grass silage was replaced by pea-barley intercrop silage. The low intake in the latter case was mainly attributed to the fermentation characteristics of the pea-barley intercrop and the formation of excessive amounts of lactic acid and ammonia, which adversely affect silage intake. Increasing the dry maater content of the silage raw material by wilting or by reducing the pea-to-cereal ratio appears to be beneficial in terms of ensiling quality.


Digestibility of intercrops In a study on intercropped grass-alfalfa as silage for dairy cat- tle, the dry matter and protein digestibility of the inter- cropped silage were improved compared to alfalfa silage alone. The improved digestibility in this case was the result of the following reasons:


- There is effective degradation thanks to an optimal ener- gy-to-protein ratio and increased microbial profiles due to the use of multiple substrates.


- The tissues of the harvested material subjected to inter- cropping are degraded to a greater extent than those of


▶ ALL ABOUT FEED | Volume 28, No. 6, 2020 29


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