Effect of feed additives in growing lambs fed diets containing wet brewers grains

Asian - Australasian Journal of Animal Sciences, Oct, 2008 by J.I. Aguilera-Soto, R.G. Ramirez, C.F. Arechiga, F. Mendez-Llorente, M.A. Lopez-Carlos, J.M. Silva-Ramos, R.M. Rincon-Delgado, F.M. Duran-Roldan

ABSTRACT : The study was conducted to evaluate and compare the effects of feed additives on ruminal fermentation, nutrient digestibility and performance of lambs fed diets containing 60% wet brewers grains (WBG). In Experiment 1, two simultaneous trials were conducted. Fifty intact (20.2 [+ or -] 0.8 kg BW) lambs were used in a feedlot trial and 10 (rumen cannulated; 32 [+ or -] 1 kg BW) in a digestion trial. The pH, volatile fatty acids (VFA) and ammonia-N in lambs were also estimated. Lambs were randomly assigned to one of five diets: i) without additives (Con), ii) with 1% bicarbonate (Bic), iii) with 1% bentonite (Ben), iv) with 33 mg/kg monensin (Mon) and v) with 200 mg/kg fibrolityc enzymes (Enz). In Experiment 2, 120 Rambouillet x Pelibuey intact male lambs (19.5 [+ or -] 1.5 kg BW) were used in a feedlot trial and randomly assigned to four diets: i) without additives (control), ii) with 1% Bic, iii) with 33 mg/kg Mon and iv) with 1% Bic and 33 mg/kg Mon. In Experiment 1, lambs fed diets containing Bic or Mon had significantly higher final weight, DMI, ADG than other lambs. However, apparent DM, OM, CP, NDF and ADF digestibilities and ruminal individual VFA content were similar (p>0.05) among treatments. Conversely, treatment x collection period interaction was significant for ruminal pH and N[H.sub.3]. In Experiment 2, lambs fed diets containing a Bic and Mon combination had significantly higher final weight, DMI and ADG. It is concluded lambs fed Bic or Mon or Bic and Mon combination had better performance characteristics than lambs on Ben or Enz. (Key Words : Feed Additives, Sheep, Wet Brewers Grains)

INTRODUCTION

Brewers grains are by-products produced during beer production. These materials are acceptable sources of undegradable protein and water soluble vitamins (Westendorf and Wohlt, 2002). They have been used in animal feeding including ruminants and non ruminants (Younker et al., 1998). However, their nutritional content varies among brewing industries, type of substrate (barley, wheat, corn, etc.), and fermentative process (Murdock et al., 1981; West et al., 1994). Some industries will dry the brewers grains and sell it as dried brewer grains, while others sell as wet brewers grains (WBG; Crawshaw, 2001). Unfortunately, WBG need to be used in close proximity to the brewery plant, because transporting could become very expensive due to elevated water content (75-80%) (Westendorf and Wohlt, 2002). Nevertheless, water content may be very advantageous to livestock producers in areas, like the Central-North part of Mexico, where water quality and provision are limited (Aguilera et al., 2007).

It seems that ruminants fed large amounts of WBG have fast ruminal fermentation rates and low pH (3.8-4.8) due to low particle size and high soluble carbohydrates Gierus et al. (2005). Owens (1959) reported that animals feeding on large amounts of WBG were susceptible to ruminal acidosis. Moreover, Kwatra et al. (1983) reported lactic acidosis in buffaloes consuming WBG diets, presenting with clinical signs such ataxia, dehydration, glazed eyes and diarrhea. Furthermore, Morel and Lehmann (1997) found latent ruminal acidosis in feedlot steers fed WBG. In addition, Okwee-Acai and Acon (2005), reported increased incidence of lameness when dairy cows were fed with WBG diets compared to non-WBG diets (47.8 vs. 24.0%).

Under certain conditions, WBG can be a source of contamination with toxic agents. Aspergillus flavus (Wadhwa et al., 1995) was isolated from diets containing WBG and provided to buffaloes diagnosed with hepatotoxicity. Moreover, Simas et al. (2007) found aflatoxins (1-3 g/kg) on one third of WBG samples collected at dairy farms.

Feed additives are a group of feed ingredients that can cause a desired animal response in a non-nutrient role such as pH shift, growth, or metabolic modifier (Hutjens, 1991). Particularly, monensin sodium is used to manipulate ruminal fermentation (Bergen and Bates, 1984). Fibrolytic enzymes can increase fiber digestibility (Sheppy, 2001). Whereas, sodium bentonite participates by shifting VFA patterns, slowing passage rates, exchanging mineral ions and inactivating mycotoxins (Kabak et al., 2006). On the other hand, sodium bicarbonate/sodium sesquicarbonate, has a buffer activity and it has been proved to increase dry matter intake and to stabilize rumen pH (Hutjens, 1991).

Knowledge of the practical use of WBG for animal feeding has been the aim of several trials previously conducted by Aguilera et al. (2007) who found that feedlot lambs can be fed diets containing 60% of WBG. Thus, the purpose of these trials was to evaluate and compare the effects of feed additives on ruminal fermentation, nutrient digestibility and feedlot performance of lambs fed diets with 60% WBG.

MATERIALS AND METHODS

Experiment 1

Fifty Rambouillet x Pelibuey intact male, recently weaned lambs (20.2 [+ or -] 0.8 kg BW) were included in feeding trial 1. Vaccinated and dewormed lambs were randomly allotted to one of five diets (10 per treatment) as shown in Table 1. Dietary ingredients were mixed every two weeks and kept in a bunker silo. Additives were included in the diet prior to feeding, using a horizontal 100 kg-mixer. Lambs were adapted to diets for a period of 10 d; thereafter, they remained in the feeding trial for 90 d. Diets were offered twice a day (08:00 and 16:00 h), considering a 5% daily increase. Lamb intakes were determined by recording weight differences between offered and refused feed. Individual body weights of lambs were recorded every 30 d and initial body weight was used as a covariate for average daily gain (ADG) adjustments.

Ten ruminal cannulated RambouilletxPelibuey weathers (32 [+ or -] 1 kg BW) that were fed the same experimental diets used in feeding trial 1 (Table 1), were used in a replicated 5x5 Latin Square design, for a digestion and rumen fermentation trial. Every feeding period lasted 21 d (14 d of adaptation and 7 d of collection). Animals were housed in metabolic crates with free access to water. Diets were offered ad libitum twice daily (08:00 and 16:00 h). Feed consumption of lambs was determined by recording daily offered and refused feed. Diet samples and orts were collected daily, dried at 55[degrees]C for 48 h, and ground (1-mm screen) in a Wiley mill. Samples and composites were classified by period and stored for further analyses.