The growth performance and health status of ruminants always remain a primary goal of livestock production. Many attempts have been undertaken to increase ruminant productivity through manipulation of rumen microbes
(Elghandour et al., 2015; Ghorbani et al., 2002; Khan et al., 2016; Krehbiel et al., 2003; Seo et al., 2010). Several compounds have been used to improve ruminant performance either by manipulation of the rumen environment such as rumen buffers or by altering the composition and metabolic activities of rumen microbes
(Alhidary et al., 2019; Mao et al., 2017; Puniya et al., 2015). Since the ban of antibiotics in ruminant production, more emphasis has been given towards the increased use of natural growth promoters such as direct-fed microbial (DFM)
(Beauchemin et al., 2006; Buntyn et al., 2016; Chaucheyras-Durand and Durand, 2009; Gaggia et al., 2010; Puniya et al., 2015; Seo et al., 2010).
The term DFM is different from that of probiotic since the former involves the use of live naturally occurring microbe
(Krehbiel et al., 2003; Kenney et al., 2015). The DFM is a mixture of mono or mixed culture of live microorganisms, mainly the lactic acid-producing bacteria, which produce beneficial health effects by improving the gastrointestinal microbes balance
(Elghandour et al., 2015; Puniya et al., 2015). The DFM promotes digestion, increases feed intake, minimizes ruminal disorders and enhances animal performance
(Elghandour et al., 2015). In addition to improving the performance of the ruminants, DFM detoxifies undesirable compounds, improves the immune system, maintains gastric peristalsis and enhances intestinal mucosal integrity
(Jeyanathan et al., 2014; Khan et al., 2016; Krehbiel et al., 2003; McAllister et al., 2011; Seo et al., 2010).
Although there are some studies about the role of probiotics and DFM in nutrition of small ruminants in general
(Abas et al., 2007; Abdelrahman 2010; Abd El-Tawab et al., 2016; Alhidary et al., 2016), little information are available on the effect of DFM supplements on the general performance of newborn lambs particularly under different weaning conditions. Weaning period is a critical period during which growth rate declines. The level of weaning stress mainly depends upon several conditions including weaning age, diets and BW
(Peters and Laes-fettback, 1995). Therefore, the objective of this study was to evaluate the growth performance and metabolic profile of newborn Najdi lambs supplemented with DFM at different ages of weaning.
The study was undertaken at The Khalediah Farm, Tebrak, Riyadh region, Saudi Arabia, with the approval of the Departmental Board of Studies for Methodology and Welfare, King Saud University, Saudi Arabia. Sixty newborn Najdi male lambs (body weight (BW): 5.40±0.10 kg; age: 5 days old) were randomly assigned to one of four treatments (15 animals per treatment). Treatments included lambs receiving no treatment and weaned at 60 days old (control) or lambs receiving oral dose (5 ml) of a commercial DFM paste (BIOSTART™ Paste, Bio-Vet Inc., Barneveld, WI, USA) at 5, 10 and 15 days old and weaned 30 (DFM30), 45 (DFM45) or 60 (DFM60) days old. The commercial DFM contained active dry yeast, enzymes, minerals, vitamins, and lactic acid–producing bacteria (including
Bacillus licheniformis,
Bacillus subtilis,
Enterococcus faecium,
Lactobacillus acidophilus,
Lactobacillus casei,
Lactobacillus lactis,
Pediococcus cerevisiae and Saccharomyces cerevisiae), with a total of 2 billion colony-forming units/ml. Most of the bacteria mentioned above were classified as lactic acid producing bacteria
(Seo et al., 2010).
Immediately after birth, the navel cord of all lambs was cut and disinfected using iodine spray (10% Iodine Pump Spray, Nettex Agri, Rochester, UK). Thereafter, newborn lambs were allowed to suckle the colostrum from their dams and were vaccinated against Caseous Lymphadenitis diseases. At 6 weeks old, lambs were vaccinated against Pasteurella, Clostridium and Peste des Petits Ruminants. All lambs were offered the same basal diet consisting mainly of chopped alfalfa hay (
Medicago sativa), chopped Rhodes grass hay (
Chloris gayana Kunth) and complete pelleted rations and complete pelleted rations, containing 2.77 MJ of energy and 14.0% CP/kg (DM basis) with free choice to stuck milk from their dams (CP= 14%, Maram, Alshamel company, Riyadh, Saudi arabia).
Lambs were individually weighed immediately after birth, and every 2 weeks thereafter until weaning to determine body weight gain (BWG) and average daily gain (ADG). After the age of 5 days, the number of dead lambs for each treatment was recorded to determine the mortality rate.
Blood samples (10 mL) were collected from each lamb before the morning feeding via jugular venipuncture, using plain vacutainer tubes, at 1, 15, 30 and 60 days old. Serum was obtained by centrifugation at 3000 x g for 15 minutes at 4°C and then frozen at -20°C until analysis. The serum concentration of glucose, total protein, creatinine, urea-N, total cholesterol, triglyceride, calcium (Ca), phosphorus (P), zinc (Zn) and copper (Cu) was analyzed using a semi-automated analyzer (RX Monza; Randox Laboratories, Crumlin, UK) according to the manufacturer’s instructions. Serum cortisol concentration was measured using a commercial kit (Human Gasallschaft Fur Biochemicaund Diagnostica GmbH, Germany) and a microplate reader (Bio-Tek Instrument, VT, USA) according to the manufacturers’ procedures.
All data were analyzed as repeated measures using the General Linear Model (SAS Institute Inc., Cary, NC, USA) for a completely randomized design. The model includes the treatment (age of supplementation DFM), lambs within treatment, the day of measurement, and the interaction of the treatment x measurement day, with the DFM treatment as the main effect. Lambs within treatment were a random variable and the error term for the main effect. Least square means were used to compare treatment means and used in tables with the pooled stranded error of means. Differences among treatment means were detected using protected least significant differences (LSD) procedure, with P<0.05 considered statistically significant unless otherwise noted.
The effects of DFM supplementation on growth rate, ADG and the mortality rate of newborn lambs weaned at different ages (30, 45 or 60 days old) are presented in Table 1. There was no difference (P>0.05) in final body weight (FBW), BWG and ADG between the control and DFM treatments over the experimental period (days 0-60). The means of the FBW, BWG and ADG were similar among treatments (16.49±2.34, 11.04±1.13 and 0.19±0.02 kg, respectively, data not shown). However, a treatment x day of measurement interaction was found for FBW, BWG and ADG during the second period of the experiment (P<0.05). The BWG and ADG were (P<0.05) greater in lambs in the control and DFM45 between day 30 and 45, but higher in the DFM60 lambs from day 45 to day 60. There also was an effect (P<0.05) of the day of measurement on FBW, BWG and ADG. The improved growth performance in our DFM lambs is consistent with results of
Pond and Goode (1985) who reported a greater ADG in lambs fed DFM before and after weaning up to four weeks. Similarly,
Birch et al., (1994) also documented a greater ADG in lambs supplemented with probiotic. The DFM is known for their ability to enhance nutrients absorption, increase feed intake and ADG and improve feed conversion ratio
(Khan et al., 2016; Whitley et al., 2009). Furthermore,
Elghandour et al., (2015) reported a rapid rumen development by DFM supplementation to newborn calves and showed rumination at the age of 30 days with increasing of a solid diet. Other health and nutritional benefits of the DFM and probiotics for ruminants have been explained in various reports (Dicks and Botes, 2010;
Elghandour et al., 2015; Gilliland 1989; Seo et al., 2010). Mortality rates in DFM45 and DFM60 lambs was declined from 33.33% to 6.67% compared with those of control lambs (Table 1). This finding agreed with
Kritas et al., (2006) who reported a lower mortality rate of DFM-fed lambs compared with control lambs. Generally, DFM supplements mediate immune response especially in young ruminants since the microorganisms in the small intestinal tract is not well established with more susceptibility to the colonization of pathogenic microorganisms
(Elghandour et al., 2015; Khan et al., 2016; McAllister et al., 2011).
Effects of DFM on serum cortisol and metabolites concentration are shown in Table 2. No treatment differences were found (P>0.05) in the serum concentrations of glucose, total protein, urea-N, and creatinine. Cortisol concentration tended to decrease (0.1>p>0.05) with DFM compared to control. The serum total cholesterol concentration was increased (P= 0.02) in DFM60 lambs while the DFM30 lambs had the lowest serum concentration of triglyceride (P=0.02) compared with those of control lambs. The serum concentrations of cortisol, glucose, creatinine, and total cholesterol were affected (P<0.05) by day of measurement. In addition, treatment x day of measurement interactions for the concentrations of cortisol, glucose, total cholesterol, and triglyceride (P<0.05) were also found (Table 2). The altered serum concentrations of total cholesterol and triglyceride of DFM-fed lambs in the current study may indicate a role of DFM in modulating carbohydrate and lipid digestion and metabolism
(Antunovic et al., 2005; Khan et al., 2016). Similar observations were previously reported in lambs fed DFM and probiotics
(Abdelrahman 2010; Lubbadeh et al., 1999). In this study, DFM administration decreased the serum cortisol and creatinine levels implying a role in alleviating stress and decreasing tissue damage. Abdelrahman (2010) reported a declined creatinine in lambs fed DFM while the immunomodulating role of DFM and probiotics in small ruminants has been reported elsewhere
(Abd El-Tawab et al., 2016; Khan et al., 2016).
Effects of DFM on mineral profile of new born lambs are illustrated in Table 3. Serum Ca did not differ among treatments, but serum P, Zn and Cu were affected (
P<0.05) by treatment. The DFM30 lambs had the lowest serum P concentration (
P =0.01). Serum Zn and Cu concentrations in DFM30, DFM45, and DFM60 lambs were less than (
P<0.05) those of control lambs. Generally, the effects of DFM supplementation on mineral utilization, including absorption, retention, and appearance, in ruminants at different physiological stages have not been reported previously or are not fully understood. Rumen microbes produce fermentation by-products, including short-chain fatty acids and lactic acid which contribute to reducing the pH and consequently may affect, positively or negatively, the minerals solubility, absorption and retention
(Cashman, 2003; Khan et al., 2016). In addition, the chelating effect of Ca on microminerals could not be neglected especially the DFM used in this study had a higher Ca content. Yet, the changes in serum concentrations of P, Zn and Cu of DFM lambs were within the normal ranges for sheep
(Herdt and Hoff, 2011; Puls 1988).
