Effect of Yeast Culture on Efficiency of Nutrient Utilization for Milk Production and Impact on Fiber Digestibility and Fecal Particle Size

ABSTRACT

Approximately 260 Holstein cows on a commercial dairy were utilized in a switchback study. Treatments consisted of control or 56 g/d of yeast culture. The objectives of this experiment were to quantify the benefit of yeast culture on 1) efficiency of milk production, and 2) nutrient flows within the dairy system that utilizes a solids separator. Milk yield was recorded every 12 d. Pen feed intakes and refusals were recorded daily. Manure fiber particle size was determined from fecal grab samples via wet sieving. In addition, a mixture of feces plus water was sieved through a screen to replicate a manure solids separator. Cows receiving yeast culture showed numerically greater DMI (0.13 kg/d), an increase (P 0.05). Milk yields were similar between treatments; however, there was a trend for an increase (P

Key words: yeast culture, milk production, nutrient utilization, fecal particle size

INTRODUCTION

Dairy farms use the manure produced on the farm as fertilizer for crops. Application of manure is based on N and P concentrations of the manure and the crops' requirements for these nutrients. If requirements are met with manure application and there is excess manure, it must be either applied above the requirement or removed from the farm. If the manure is over-applied, nutrient run-off into surface waters or leaching into ground waters may occur, causing an adverse environmental impact such as eutrophication. Removing manure from the farm can be economically unfavorable due to the high concentration of water. A solid form of manure is a more economically favorable way to transport nutrients off the farm.

Solid separation of dairy manure is an effective practice of removing solids and nutrients from the effluent (Chastain et al, 2001). The remaining liquid will subsequently have a decreased amount of nutrients such as N and P. The solids portion can be removed from the farm boundaries as a way to decrease nutrient application to the farm fields. An increase in diet digestibility can result in a decrease in nutrient and solid content of manure. Previous field study research has shown feeding yeast culture reduces undigested feed particles in manure (Belknap and Yoon, 2001).

Feeding yeast culture can increase feed efficiency and net return of lactating dairy cattle. Schingoethe et al. (2004) observed a 7% increase in feed efficiency (kg of energy-corrected milk/kg of DMI) when yeast culture was fed to midlactation cows during heat stress. Diet DM, hemicellulose, and CP digestibility increased when a yeast culture was supplemented (Wiedmeier et al., 1987). Shaver and Garrett (1997) calculated a net return of $0.13/d per cow when feeding yeast culture to commercial dairy herds. The objectives of this experiment were to quantify the benefit of yeast culture in a dairy ration on 1) efficiency of milk production, and 2) nutrient flows within the dairy system that utilizes a solids separator.

MATERIALS AND METHODS

Animals

Approximately 260 Holstein cows were utilized in a 96-d lactation switchback designed study. The study was conducted on a commercial dairy farm in western Washington and consisted of 40- and 49-d periods. The Washington State University Animal Care and Use Committee approved the experimental protocol. Cows were blocked and assigned to treatments based on the following criteria: >30 DIM, milk production, parity, pregnancy, and BW. Treatments consisted of control (no supplemental yeast culture) or 56 g/d of yeast culture (Diamond V XP Yeast Culture, Diamond V Mills, Cedar Rapids, IA). Average pen DIM for control and treatment groups were 179 and 191, respectively, at the beginning of trial. Cows were milked 3 times a day. Cows removed from pens for health reasons were excluded from the study. Therefore, only 222 cows completed the study (111 cows per pen).

Diets

All diets were fed as a TMR, mixed using a Loewen mixer (Matsqui, British Columbia, Canada), and loaded per manufacturer's recommendations. Diets were balanced at or above National Research Council's recommendations for high-producing Holstein cows in midlactation by a consulting nutritionist (NRC, 2001). The basal diet TMR consisted of soybean meal, steam rolled corn, cull raw potatoes, canola meal, whole cottonseed, corn silage, alfalfa hay, and vitamin-mineral mix (Table 1). Yeast culture was incorporated into a premix (56 g XP yeast culture in 140 g premix) containing ground corn, mill run, and soybean meal that was mixed into the TMR at a rate of 56 g yeast/d per cow. The control diet was TMR plus 140 g/d of the carrier grains alone.

Measurements

Milk yield was recorded every 12 d by Dairy Herd Improvement personnel (Burlington, WA), and 24-h composite milk samples were collected from 3 milkings for fat and protein analyses. Pen feed intakes and refusals were recorded daily. Feed was sampled weekly for nutrient analysis of acid AIA, CP, NDF, ADF, ADL, Ca, P, and K (Dairyland Laboratories, Arcadia, WI; Table 2). Body weights were recorded at the beginning and end of each period. Fecal grab samples of approximately 200 g and urine samples of approximately 200 mL were collected twice during the last 2 wk of each period from 20 to 25 cows per treatment. Samples were pooled for chemical analysis (Dairyland Laboratories, Arcadia, WI). Fecal samples were analyzed for AIA, CP, NDF, ADF, ADL, Ca, P, and K. Urine samples were analyzed for Na, K, Cl, total N, ammonia N, and creatinine.