Browsing by Author "Nowers, Nadine"

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    The effect of an oregano oil extract in a lactating dairy cow diet on production responses of Holstein cows
    (Stellenbosch : Stellenbosch University, 2016-03) Nowers, Nadine; Cruywagen, C. W.; Stellenbosch University. Faculty of Agrisciences. Dept. of Animal Sciences.
    ENGLISH ABSTRACT: Forty Holstein cows, 178 ± 17 (SE) DIM and weighing 624 ± 9 (SE) kg, were used in a lactation trial of 60 days to determine the effect of oregano essential oil on milk production and milk composition. The cows were ranked according to milk yield, DIM and lactation number and each consecutive pair formed a block. Treatments were allocated randomly to each of the 20 blocks. An essential oil product (Dosto Concentrate 500; DOS), was evaluated against a placebo control (CON) treatment. Cows were housed in a semi-open free-stall barn with sand beds and had free access to fresh water. All cows received a basal diet consisting of lucerne hay (53% NDF and 11% CP) that was offered ad libitum and 28 kg/day of a semi-complete lactation feed, offered twice daily at 07:30 and 16:00. All refused feed were weighed back weekly to determine intake per group. Treatments (DOS and CON) only differed in terms of a maize based supplement that, in the case of the DOS treatment, every 300 g maize supplement portion, contained 0.5 g of Dosto Concentrate 500. The cows were milked twice daily at 06:00 and 15:30 and the supplements were offered individually to cows in the milking parlour during each milking. Milk yield, milk composition and cow weights were recorded daily via the Afikim system. Milk samples were also collected during weeks three and eight for composition analysis at the Elsenburg Dairy Laboratory. Data collected over time were subjected to a repeated measurements ANOVA, while mean values were analysed according to a main effects ANOVA with treatment and block as main effects. All data were analysed with the aid of Statistica 64 version 12 and significance was declared at P < 0.05. Regarding all 40 cows, treatment had no effect (P > 0.05) on milk yield or milk composition over the entire period. However, in the CON treatment, the lactose content was higher (P < 0.05) during the first two weeks and the milk protein content was higher (P < 0.05) from week four to eight. When data of the ten top milk producing cows per treatment were analysed separately, the fat content and milk fat yield were higher (P < 0.05) for the DOS treatment during the first three weeks of the trial and lactose was higher (P < 0.05) for the CON treatment in the first week. Mean milk yield of the ten top milk producing cows per treatment did not differ (P > 0.05) and was 37.9 kg for the DOS treatment and 37.3 kg for the CON treatment. Mean fat content and fat yield was higher (P < 0.05) in the DOS treatment (37.1 g/kg and 1.41 kg/day) than in the CON treatment (33.8 g/kg and 1.26 kg/day). The higher fat content also resulted in a higher (P < 0.05) energy corrected milk yield of cows in the DOS treatment than in the CON treatment (38.8 and 36.6 kg/day, respectively). With regards to feed intake, the CON group consumed on average 17.3 kg more roughage per week than the DOS group. After a two month period 12 milk samples were collected from each group and was sent to be evaluated in terms of microbiological quality and sensory characteristics. The microbiological quality of the milk samples was evaluated by using petrifilm plates for total aerobic counts (TAC) and coliform counts (CC). Based on the microbiological analysis, all the milk samples were considered suitable for human consumption (< 200 000 cfu/ml). The treatment group differed (P ≤ 0.001) from the control group in terms of aroma and flavour. No oregano flavour was detected and the difference in aroma and flavour was probably due to the difference in fat content. It was concluded that oregano essential oil in dairy cow diets stimulated milk fat production and increased energy corrected milk yield in high milk producing dairy cows. Oregano essential oil had no adverse effect on milk aroma and flavour.