Share this page
Alignment with SDGs
Christian Alvarado1, Juan Pablo Keim1, Guillermo Seguel1, Einar Vargas-Bello-Pérez2
1 Instituto de Producción Animal, Facultad de Ciencias Agrarias, Universidad Austral de Chile, Valdivia, Chile. 2 Departamento de Ciencias Animales, Facultad de Agronomía e Ingeniería Forestal, Pontificia Universidad Católica de Chile, Santiago, Chile.
In Chile, the relative importance of grazing systems has increased steadily over time. One characteristic of pastures in the south of Chile is that there is a relatively high pasture growth during spring and autumn; and low growth, and thus pasture availability, during winter and summer. Considering that most calving’s in dairy farms of southern Chile occur in fall (March, April and May) and spring (August, September and October), a low pasture availability during early and mid-lactation usually occurs, and it is common to observe an overgrazing and pasture degradation. In addition to the affected-on growth rate of the permanent prairies in summer season, the nutritive quality of pastures also decreases. Thus, concentrate supplementation is a typical measure in dairy farms during winter and summer although it is not always profitable due to the increasing costs of concentrate. It has been suggested that growing crops on-farm helps to reduce the need for purchased supplements and, therefore reduces production costs and increases profitability. However, the use of supplementary crops in Chilean grazing dairy systems is still low representing less than 5% of the mean annual diet.
Summer Brassica crops might be a complement to pastures due to their high dry matter yield and relatively high nutritive value. Turnip and rape are crops of the genus Brassica used to supply feed demand in the summer. In the literature, milk production of cows supplemented with Brassicas has had a variable response. In addition, there are few studies describing the fatty acid profiles contained in milk and derived products. Therefore, the objective of this study was to evaluate the effect of summer supplementation with turnip (Brassica rapa spp. rapa L.) and rape (Brassica napus spp. biennis L.) in dairy cows on the DMI, production and milk composition, and fatty acids profile of milk and cheese.
Materials and methods
The investigation was carried out in the Experimental Agricultural Austral Station (EEAA) of the Austral University of Chile. The animals were selected according to milk production in the previous lactation. Twelve multiparous lactating dairy cows (25 kg/day of milk production, 90 DIM) were randomly allocated to the three dietary treatments according to milk production measured during the uniformity period, in a replicated 3 x 3 Latin Square design with three 28-day periods. Each experimental period consisted of 14 d of adaptation to diets and 7 d of experimental measurements. Cows were held in individual tie stalls. The first group (control) was offered a diet similar in type and quantity of feed offered to cows in dryland farms (16 kg DM: 6 kg DM of pasture, and 6 kg DM pasture silage and 4 kg DM of concentrate). The same levels of feed were offered to the other two groups, but in addition 6 kg DM of either turnip or rape was offered, thus substitution of brassica supplementation was determined. A 200 g mineral mixture was offered along with the silage. Prior feeding, all feeds were weighed and offered individually for each cow according to the dietary treatments.
During the 7 days of measurement milk production and dry matter intake (DMI) were recorded, and samples diet of ingredient were taken and analyzed for DM, crude protein, metabolizable energy and NDF. Additionally, blood and milk samples were taken for fatty acid analysis by gas chromatography. At the last day of each period 15 L of milk were obtain from each treatment for cheese production.
Results and Conclusions
Dry matter intake (DMI) and production are shown in table 1. The DMI was lower in treatment were brassicas were included (1 kg lower, approximately), with no differences in milk production or composition but, cows supplemented with turnip and rape were more efficient, that mean, this cows’ production was similar with less DMI.
Fatty acid profile of milk and cheese are presented in table 2. In general terms, the results indicate that the supplementation with turnip and rape, substantially modified the profile of fatty acids (AG) contained in the blood plasma and in the milk, increasing the saturated fraction and decreasing the content mono and polyunsaturated, when comparing the results with the control treatment. The organoleptic characteristics of the cheeses made from the milk of cows supplemented with turnip and rape, showed a greater intensity in the flavour, aroma, itch and bitterness.
Our study shows that turnip and rape could be an interesting alternative to concentrate for summer supplementation with no negative effects on milk production but with a lower DMI, and decreasing the cost of milk production, since lest concentrate and lower DMI is needed.
This work was supported by the Chilean National Fund for Science and Technology (FONDECYT) number 11150538 “Optimising milk production of pasture-fed lactating dairy cows through the utilization of winter and summer brassicas”