Evaluation of appropriate storage conditions of liquid brewer’s yeast as feed supplement for lactating dairy cows and its effect on milk quality

Abstract

Milk production in Kenya is dominated by smallholder dairy farmers who are faced with challenges on feeding dairy cows. This is generally due to inadequate and low quality feeds and high cost of inputs. Thus, utilization of inexpensive nutrient dense feed supplement such as liquid brewer’s yeast (LBY) is inevitable. However, LBY is rarely used due to its short shelf life and lack of technical information on effect on milk quality. This study was performed to investigate the appropriate storage conditions of LBY and to ascertain its suitability for use as alternative feed source for dairy cows without compromising on milk quality in smallholder dairy farms in Githunguri Sub-County, Central region in Kenya. First phase of the study involved collection of samples from three source of LBY (supplier, distributors and farmers), stored under aerobic condition at 10, 20 and 30 °C, then tested at days 0, 7, 14 and 21 in a 3 x 3 x 4 factorial arrangement. The parameters tested were total viable counts (TVC), total coliform counts (TCC), lactic acid bacteria (LAB), yeast and mould. The second phase entailed evaluation of milk for physicochemical: butter fat, milk protein, solid not fat, lactose, ash, freezing point depression, electrical conductivity (EC) and microbiological: TVC and TCC parameters. Thirty farms were randomly selected from three milk delivery routes. A longitudinal survey was conducted where farms were nested within routes and equal number of farms selected per route based on supplementation of lactating cows with either LBY or commercial dairy meal (CDM). A repeated measure analysis was performed using linear mixed models methodology by PROC MIXED of SAS for milk quality and questionnaire data summarized using descriptive statistics. The results revealed statistically significant levels (p<0.05) on sources and storage time of LBY while the interventions were insignificant (p>0.05). The results on milk quality indicated significantly (p<0.05) higher milk protein levels and low freezing point depression for milk from LBY supplemented cows (3.07 ± 0.03% and -0.532 ± -0.005 °C) than those supplemented with CDM (2.99 ± 0.03% and -0.516 ± -0.005

°C) respectively. This was an indication of increase in total solids. The study concluded that appropriate storage time of LBY is seven days, thereafter, a significant increase in microbial load is observed. Conversely, the use of LBY as a protein feed supplement improved milk quality. The research recommends capacity building to enable stakeholders in the dairy industry appreciate the importance of hygienic storage and utilization of LBY as alternative protein source for dairy cows.