J.W. West

Effect of enzyme or microbial treatment of bermudagrass forages before ensiling on cell wall composition, end products of silage fermentation and in situ digestion kinetics

Tifton 85 bermudagrass (T85) and Coastal bermudagrass (CBG) established on adjacent plots and managed similarly were harvested after 3 or 6 weeks of regrowth and used to investigate the effects of fibrolytic enzymes or microbial inoculant treatment before ensiling on nutrient composition and recovery, cell wall chemistry and digestion. Prior to ensiling T85 had higher concentrations of neutral detergent fiber (NDF) and acid detergent fiber (ADF), similar concentrations of total lignin, and greater (p < 0.05) in vitro and in situ dry matter (DM) and NDF disappearances when compared with CBG. Coastal bermudgrass had higher (p < 0.05) concentrations of acid-insoluble lignin and ether-linked ferulic acid (monomers and dimers), and lower concentrations of glucose and mannose than T85. Treatment of bermudagrass forages with microbial inoculant decreased (p < 0.05) concentrations of NDF, hemicellulose, butyrate, lactate, cell walls and acid-insoluble lignin, and increased (p < 0.05) concentrations of ammonia, total volatile fatty acids (VFA) and acetate in silages. Treatment of bermudagrass forages with fibrolytic enzymes had no effect on silage fiber concentration, cell wall carbohydrate fraction or concentration of p-coumaric and ferulic acids, but increased the concentration of butyrate. Among silages, T85 had higher (p < 0.05) in vitro and in situ dry matter DM and NDF disappearance and higher (p < 0.05) potentially digestible fractions and smaller (p < 0.05) indigestible fractions of DM and NDF than CBG. Treatment of bermudagrass forages with fibrolytic enzymes had no effect on in vitro or in situ DM or NDF disappearance of silages. Treatment of bermudagrass forages with microbial inoculant increased in situ DM disappearance at 72 h of incubation (p < 0.10) and the potentially digestible fraction of DM (p < 0.05) of silages. Although treatment of bermudagrass forages with microbial inoculant had no effect on silage in vitro or in situ NDF disappearance at 48 h of incubation, it increased in situ NDF disappearance at 72 h (p < 0.05) and the potentially digestible fraction of NDF. It is concluded that the greater cellulose content of cell walls with the same or less lignin in T85, and the greater concentration of ether-linked ferulic acid in CBG explain the greater digestibility of T85 when compared with CBG at similar stages of maturity. Treatment of bermudagrass forage at ensiling with microbial inoculants may have more potential than extracts of fibrolytic enzymes in improving silage fiber digestion.

Effects of the addition of direct-fed microbials and glycerol to the diet of lactating dairy cows on milk yield and apparent efficiency of yield

A study was conducted to evaluate the effects of a direct-fed microbial (M) and dietary glycerol (G) on milk yield, efficiency of yield, and nutrient digestibility during hot weather. Sixty Holstein cows averaging 120 d in milk (DIM) and 36.2 kg/d of milk were used in a 12-wk 2×2 factorial design trial from June through September 2008. Cows were fed a common diet during the 2-wk standardization period and were blocked by milk yield, DIM, parity, and dry matter intake. Diets were based on corn and ryegrass silages and balanced to be isocaloric and isonitrogenous. Treatments included a negative control (M- or G-), 4 × 10(9) cfu/head of a combination of Lactobacillus acidophilus NP51 and Propionibacterium freudenreichii NP24 (M+), control plus 400 g/h per day of 99% pure food-grade glycerol (G+), and 4×10(9) cfu/h per day of a combination of Lactobacillus acidophilus NP51 and Propionibacterium freudenreichii NP24 plus 400 g/h per day of 99% pure food-grade glycerol (MG++). No interactions were observed between direct-fed microbials and dietary glycerol in the study except on apparent nutrient digestibility. No differences were observed in dry matter intake, which averaged 22.7, 23.1, 23.4, and 22.9 for M-, G-, M+, and G+, respectively. Milk yield was increased for M+ compared with M- at 34.1 and 31.7 kg/d, but G+ had no effect on yield. No treatment effect was noted for milk fat percentage or milk protein percentage among diets. Milk protein yield was higher for M+ compared with M- at 0.93 versus 0.87 kg/d. Energy-corrected milk was improved for the M+ versus M- groups at 33.5 and 31.6 kg/d, respectively. No differences in respiratory rate, skin temperature, body temperature, or concentrations of serum glucose or urea N were observed among treatments. Improvement in apparent digestibility was observed with M+ and G+ compared with M-/G- in this experiment. The addition of a direct-fed microbial alone improved milk and protein yield, energy-corrected milk, and apparent digestibility of crude protein, neutral detergent fiber, and acid detergent fiber, and the inclusion of glycerol (G+) had a positive effect on apparent dry matter and acid detergent fiber digestibility compared with M-/G-. The addition of a direct-fed microbial and dietary glycerol may improve yield and digestibility for cows subject to heat stress.

Effects of feeding different amounts of supplemental glycerol on ruminal environment and digestibility of lactating dairy cows

A replicated 3×3 Latin square study was conducted to evaluate the effects of replacing a portion of ground corn in the diet with dietary glycerol on rumen environment, blood metabolites, and nutrient digestibility. Six rumen-cannulated Holstein cows, averaging 56±18 DIM and 38.0±8.2 kg of milk/d, were used in the study. Experimental periods included 3 wk for treatment adjustment period followed by 1 wk for data collection. Diets were corn silage based and balanced to be isocaloric and isonitrogenous. Treatments were 0 g of glycerol/d (control, CON), 200 g of glycerol/d (G2), and 400 g of glycerol/d (G4). Dry matter intake (DMI) decreased as the amount of glycerol fed increased. Milk yield was higher for CON and G2 cows in comparison with G4 cows. Milk fat percentage and yield were reduced when glycerol was fed compared with CON cows but increased the milk protein percentage at the highest concentration of dietary glycerol. These changes resulted in decreased energy-corrected milk yield and efficiency (milk/DMI) in diets supplemented with G4 compared with CON. No differences were observed in ruminal pH and ammonia concentrations. Molar proportions of acetate, valerate, and acetate:propionate ratio decreased, whereas propionate increased as the amount glycerol fed increased. Molar proportions of butyrate were greatest when glycerol was included in the diet compared with CON. Nutrient intake and digestion were not different among treatments. Results of this trial suggest that feeding increasing amounts of glycerol may decrease DMI and alters ruminal fermentation, resulting in reduced yield of milk, fat, and energy-corrected milk.

Wool cortisol is a better indicator of stress than blood cortisol in ewes exposed to heat stress and water restriction.

This study investigated the effect of water restriction on wool and blood cortisol concentrations and water consumption patterns in heat-stressed sheep. Nine Corriedale female sheep (average BW=43±6.5 kg) were individually fed diets based on maintenance requirement in metabolic crates. They were assigned to three treatments according to a Latin square design (3×3) for three periods with a 21-day duration for each period (nine sheep per treatment). Treatments included free access to water (FAW), 2 h water restriction (2hWR) and 3 h water restriction (3hWR) after feeding. Average temperature-humidity index in the experimental room was 27.9 throughout the experiment that defines heat stress conditions. Wool samples were taken at the end of each period on day 21. No differences were found in cortisol concentration in each fragment (dried, washed and residual extract) of wool (P<0.05). Total wool cortisol concentration was higher in the 3hWR group than the other treatments (P<0.05). Blood cortisol was not different among the treatments (P>0.05) and resulted in higher variable data compared with wool cortisol. Blood neutrophils and neutrophil/lymphocyte ratio suppressed in FAW and 3hWR groups compared with the 2hWR group (P<0.05). The duration of water consumption recorded after feeding in the 3hWR group was higher than in the 2hWR group when recorded in the afternoon (P<0.01). Water consumption rate was higher in the 3hWR group than in the 2hWR group (P<0.01). However, total water consumed was lower in the 3hWR group compared with other treatments (P>0.05). It can be concluded that wool cortisol provides more precise and accurate data than blood cortisol during heat stress conditions. Water restriction for 3 h after feeding can act as a stressor and is critical for sheep during heat stress as the consumption of water decreases with restriction.

Performance of lactating dairy cows fed ryegrass silage and corn silage with ground corn, steam-flaked corn, or hominy feed.

Forty-eight mid-lactation Holstein cows were used in a 6-wk completely randomized block design trial with a 4 x 3 factorial arrangement of treatments to determine the effects of feeding different proportions of corn silage and ryegrass silage with supplemental ground corn (GC), steam-flaked corn (SFC), and hominy feed (HF) on the performance of lactating dairy cows. Forage provided 49% of the dietary dry matter in the experimental diets, which were formulated to meet National Research Council requirements. Ryegrass silage provided 100, 75, 50, or 25% of the total forage dry matter, with corn silage supplying the remainder. There were no interactions between the proportion of forage provided by ryegrass silage and energy supplement. Dry matter intake and milk protein percentage decreased linearly with increasing proportions of ryegrass silage, but milk protein yield was similar among forage treatments. There were no differences among forage treatments in milk yield, milk fat percentage and yield, and energy-corrected milk yield. Dry matter intake was higher and there was a tendency for increased milk fat percentage for GC compared with SFC or HF. No other differences were observed in milk yield or composition among energy supplements. Plasma urea nitrogen and glucose concentrations were similar among treatments. Under the conditions of this trial, our results indicate that feeding a combination of corn silage and ryegrass silage is more desirable than feeding ryegrass silage alone, whereas supplementation with GC, SFC, or HF supports similar levels of milk production.

Performance of Dairy Cows Fed Annual Ryegrass Silage and Corn Silage with Steam-Flaked or Ground Corn

Twenty-four lactating Holstein cows were used in a 6-wk randomized block design trial with a 2 x 2 factorial arrangement of treatments to determine the effects of feeding ground corn (GC) or steam-flaked corn (SFC) in diets based on either annual ryegrass silage (RS) or a 50:50 blend of annual ryegrass and corn silages (BLEND). Experimental diets contained 49.6% forage and were fed as a total mixed ration once daily for 4 wk after a 2-wk preliminary period. No interactions were observed among treatments. Cows fed BLEND consumed more dry matter (DM), organic matter (OM), neutral detergent fiber (NDF), and acid detergent fiber (ADF) than those fed RS, but total-tract digestibility of OM, NDF, and ADF was greater for RS than for BLEND. No differences in nutrient intake were observed among treatments during wk 4 when nutrient digestibility was measured, but digestibility of DM and OM was greater for SFC than for GC. Cows fed BLEND tended to produce more energy-corrected milk than those fed RS, resulting in improved efficiency (kg of milk per kg of DM intake). When diets were supplemented with SFC, cows consumed less DM and produced more milk that tended to have lower milk fat percentage. Yield of milk protein and efficiency was greatest with SFC compared with GC. Blood glucose and milk urea nitrogen concentrations were similar among treatments, but blood urea nitrogen was greater for cows fed GC compared with those fed SFC. Results of this trial indicate that feeding a blend of annual ryegrass and corn silage is more desirable than feeding diets based on RS as the sole forage. Supplementing diets with SFC improved performance and efficiency compared with GC across forage sources.

Effects of water restriction following feeding on nutrient digestibilities, milk yield and composition and blood hormones in lactating Holstein cows under heat stress conditions

The effects of water restriction following feeding under heat stress conditions on nutrient digestibilities, milk yield and composition and some blood hormones in lactating Holstein cows were evaluated. The design was completely randomized with 30 high producing lactating Holstein cows (80.8±40.5 DIM) which were assigned to two treatment groups (15 cows per treatment). Treatments were free access to water (FAW) and 2 h water restriction (2hWR) following feeding. Average temperature-humidity index (THI) in the farm was over 80 throughout the experiment which defines heat stress conditions. Neutral detergent fibre, organic matter and ether extract digestibilities increased by water restriction (P<0.05); however, crude protein, acid detergent fibre, nitrogen free extract and dry matter digestibilities were not affected (P>0.05). Water intake was recorded daily during the digestibility period and was not different between FAW and 2hWR group (P>0.05). Fat corrected milk was higher in 2hWR group than FAW group (P<0.05). Milk fat was higher (P<0.05) in 2hWR group than the FAW group whereas milk protein, urea nitrogen, and solids not fat were not different among the treatment groups (P>0.05). Somatic cell counts were greater in 2hWR than FAW group (P<0.05). Free fatty acid concentration in blood was not affected by treatments (P>0.05). Blood prolactin and growth hormone were higher in 2hWR group than the FAW group (P<0.05). It is concluded that water restriction for 2 hours following feeding improved nutrient digestibility of some dietary components and increased milk fat percentage in lactating Holstein cows under heat stress conditions.

Effects of addition of bacterial inoculants to the diets of lactating dairy cows on feed intake, milk yield, and milk composition

Forty-eight lactating Holstein cows (38 multiparous, 10 primiparous) were used in a 10-wk randomized block trial to determine the effect of 2 supplemental bacterial inoculants on DMI, milk yield, and milk composition. Experimental diets were top dressed with ground corn plus one of 2 bacterial inoculant mixtures. Treatments were control (no bacterial inoculant); 2 × 109 cfu/d of Propionibac-terium freudenreichii strain NP24 plus 1 × 109 cfu/d of Lactobacillus acidophilus strain NP51 (B1); and 2 × 109 cfu/d of P. freudenreichii strain NP24 plus 5 × 108 cfu/d each of L. acidophilus strain NP51 and strain NP45 (B2). Cows fed bacterial inoculants had greater yields of milk fat (P = 0.02), FCM (P = 0.007), and energy-corrected milk (P = 0.03) than did controls. Efficiency of milk production (defined as energy-corrected milk yield per unit of DMI) was greater (P = 0.03) for cows fed bacterial inoculants compared with control cows. There was no effect of treatment on DMI, milk fat percentage, or milk protein yield or percentage. There was a tendency (P = 0.08) for increased milk yield with inoculant supplementation compared with the control treatment. Serum urea N concentrations were greater for control cows compared with those receiving inoculants, and there was a tendency for B2 cows to have greater serum urea N concentrations compared with B1 cows. Results of this trial suggest that supplemental bacterial inoculants containing P. freudenreichii and L. acidophilus can improve milk yield and apparent efficiency of nutrient utilization.

Effects of plant extracts on milk yield and apparent efficiency of lactating dairy cows during hot weather 1

ABSTRACT A study was conducted to evaluate the effects of plant extracts on milk yield, apparent efficiency of yield, and nutrient digestibility in hot weather. The plant extracts were composed of proprietary blends of selected fermentation metabolites CitriStim yeast, Aspergillus niger, and plant extracts capsicum, cinnamaldehyde, and eugenol, which were selected for the potential ability to improve physiological response to heat stress. Thirty-six Holstein cows averaging 187 ± 16 DIM and 44.1 ± 0.5 kg/d of milk were used in a 10-wk randomized complete-block design from June through August 2007. Cows were fed a control diet during a 2-wk standardization period. Cows were blocked into groups of 3 based on DIM, DMI, and milk yield, and randomly assigned within block to 1 of 3 treatments for 8 wk. Treatments were control (C), ThermalCare D (TD), and ThermalCare R (TR). Diets were cornsilage-based and balanced to be isocaloric and isonitrogenous. No differences in DMI, milk yield, or energy-corrected milk were observed among treatments. Milk fat percentage was reduced (P = 0.003) for TD and TR versus C and milk fat yield (kg/d) was reduced (P = 0.05) for TD versus TR (1.49) and C. Efficiency (defined as energy-corrected milk/DMI) was reduced (P = 0.03) for TD compared with C. No differences were observed in body temperature, respiration rate, or concentrations of serum glucose and urea N among treatment. Intake of DM (P = 0.05) and ADF (P = 0.01) was increased for TR, and digestibility of ADF was increased for TD and TR compared with C during wk 5. Results suggest that feeding supplemental plant extracts did not affect milk yield, but did affect milk components and improved ADF digestibility.

Pigeon peas as a supplement for lactating dairy cows fed corn silage-based diets

Holstein rumen-cannulated cows [n=7; initial body weight (BW) 640.56±71.43 kg] were fed a corn silage basal diet with 1 of 3 concentrates (C=control; P10=10% pigeon peas; P20=20% pigeon peas). Cows were randomly assigned to treatments in a replicated 3×3 Latin square and individually fed using Calan gates. Each experimental period was 21 d with 7 d for adaption and 14 d for sample collection. Ruminal fluid samples were taken the last day of each experimental period and analyzed for pH, ammonia, long-chain fatty acids, and volatile fatty acids (VFA). Consecutive a.m. and p.m. milk samples were taken during the last 2 wk of the 21-d period and analyzed for fat, protein, long-chain fatty acids, and somatic cell count. Dry matter intake (kg/d) was reduced during the second period and was greater for P10 diets. Milk protein was greater for cows fed P20 compared with P10. Energy-corrected milk was greater for cows fed the control diet compared with P10. Treatment had no effect on milk yield. Ruminal fluid pH decreased over sampling times; however, pH remained at or above 5.5. Diets did not affect ruminal fluid pH; however, pH was different for sampling periods. Ruminal ammonia decreased until 8h postfeeding at which time it peaked consistent with changes in ammonia concentrations that usually peak 3 to 5h postfeeding on diets high in plant proteins. Dietary treatments altered ruminal fluid VFA with reduced concentrations of acetate and greater concentrations of propionate for control diet, resulting in reduced acetate:propionate ratio. Isobutyrate exhibited an hour by treatment interaction, in which isobutyrate decreased until 8h postfeeding and then tended to be greater for P10 than for other treatments. Animals fed the P10 diet had greater concentrations of ruminal isovalerate. Ruminal cis-9,trans-11 and trans-10,cis-12 conjugated linoleic acid (CLA) isomers were not affected by dietary treatments. The P10 diet had greatest ruminal synthesis of cis-9,trans-11, but control cows had greatest ruminal synthesis of trans-10,cis-12. Milk CLA isomers were similar among treatments. Trends were observed for greater cis-9,trans-11 and trans-10,cis-12 for the P10 diet. Pigeon peas may be used as a protein supplement in dairy diets without affecting milk production, dry matter intake, or ruminal environment when they replace corn and soybean meal.