Some compositional and health indicators of milk quality of dairy cows with higher milk yield at including of selected corn species into feeding ration

Because of economical reasons the substitution of maize by feed corn as wheat (Sulamit) and triticale (Kitaro) was revolved in concentrate part of dairy cow feeding rations. The design of mentioned replacement in feeding rations was carried out according to results of previous research (Pozdíšek and Vaculová, 2008) for nutrition experiment. The aim of this paper was to evaluate the possible effects of corn replacement in cow feeding rations on milk composition and properties. The expressively different variants of corn were selected for experiment in comparison to maize (reference). Dairy cows were fed by total mixed ration on the basis of maize and clover silage and hay. Otherwise the identical day feeding rations among cow groups differed only in concentrate portions ((K, control group) maize 1.5 kg, wheat (P1) 2.0 kg and triticale (P2) 2.0 kg (experimental groups)). Group feeding rations 1 (K), 2 (P1) and 3 (P2) had: NEL/kg dry (DM) matter (6.524, 6.512 and 6.491); NL % in DM (17.9, 18.2 and 17.9); fibre % in DM (15.96, 15.74 and 15.72); PDIN/PDIE (1.189, 1.189 and 1.191). The experiment took six weeks, there were included 8, 9 and 9 cows (n = 26) of Czech Fleckvieh breed. Feed groups were well balanced in terms of milk yield, days in milk and number of lactation. The tie stable and pipeline milking equipment were used in experiment. Animals were milked twice a day and sampled at morning milking in intervals about seven days approximately. Cows were relatively healthy in terms of occurrence of milk secretion disorders. Within groups the individual milk samples (in total 182 in experiment) were aggregated into bulk samples (n = 21 = 3 groups × 7 sampling periods), which were analysed on 45 milk indicators, 18 of them were evaluated in this paper. The differences in milk yield were significantly advantageous for K group (15.32 > 14.07 (wheat) or 13.86 kg (triticale) at morning milking), while fat (3.27 < 3.47 or 3.44 %) was lower (P < 0.05). Lactose was not influenced. More important differences were in total dry matter, 12.09 (K) < 12.23 (P1) or 12.40 % (P2). While for wheat was not for triticale was similar effect observed in crude protein (CP) of milk (3.08 (K) or 3.05 (P1) < 3.23 % (P2)). Similar trend was also confirmed in casein (CAS; 2.43 or 2.44 < 2.55 %; from P < 0.05 to P < 0.001 for CP and CAS). There were insignificant differences between groups for casein number, pH acidity, electrical conductivity, Mg and Cu (P > 0.05). Milk specific weight was lowest in P1 (P < 0.01), but this indicator is practically less important. More expressive differences were in somatic cell count (SCC) in geometric mean 249 (P2) > 76 (K) or 72 10³/ml (P1). Because of quite typical high SCC variability in triticale P2 group (in opposite to this low variability in K and P1 groups) it could be caused by chance in animal selection for groups and all values met the standard demand for extra quality of milk. Therefore, it is not necessary to over estimate this result. Milk urea as metabolical indicator was higher in wheat group, significantly (P < 0.05) versus triticale group (23.39 (P1) > 20.80 (K) and 20.50 mg/100ml (P2), but all values lay in respected physiological range (from 20 to 30 mg/100ml). In the Ca case it was significantly higher (P < 0.05 versus wheat) in triticale milk group by 5.7 and 4.0 % (1306 (P2) > 1231 (K) or 1253 (P1) mg/kg). This increase could be interested in terms of milk nutritive value, but not for routine milk payment. The levels of P and Fe in milk were higher in K versus experimental groups (P < 0.05). It is less interesting in terms of economy or nutrition. In general milk was a little different according to differences in corn portions of cow feeding rations and corn variant replacement. In terms of experiment the concrete corn replacement in concentrate portion of feeding ration could not have an essential impact on milk quality and it si possible to agree with such conception. However, the milk quality and yield were not overcome by replacement of maize by wheat (Sulamit) or triticale (Kitaro). At triticale the lower milk yield was compensated by higher levels of DM, fat, CP, CAS, Ca and also SCC as compared to maize and wheat. The used corn replacement variants were not expressively worse than maize.

Keywords: cow, feeding ration, milk, milk yield, fat, lactose, casein, urea, somatic cell count, calcium, magnesium

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Tato práce byla podporována řešením projektu MZe ČR, NAZV, QF3133.