Fermented Total Mixed Ration Alters Rumen Fermentation Parameters and Microbiota in Dairy Cows

This study aimed to determine changes and interactions of ruminal microbiota and chemical parameters in dairy cows fed FTMR. Twelve multiparous Holstein dairy cows (Body weight = 616 ± 13.4 kg; day in milk = 106 ± 7.55 d; and parity = 2.31 ± 0.49; mean ± standard deviation) were divided randomly into two treatments depending on the day in milk, milk production, and parity. The two treatments were: (1) total mixed ration (TMR) and (2) FTMR. Illumina MiSeq sequencing was used to explore the changes in the ruminal microbiota. The results revealed that the bacterial and fungal diversity of the FTMR group were significantly higher than the TMR group. The predominant microbiota phyla in the bacteria and fungi showed significant differences between TMR and FTMR, as follows: Verrucomicrobia (p = 0.03) and Tenericutes (p = 0.01), Ascomycota (p = 0.04) and Basidiomycota (p = 0.04). The dominant bacterial genera in the bacteria, fungi, protozoan, and archaea that showed significant differences between TMR and FTMR were Unclassified_Bacteroidales (p = 0.02), Unclassified_RFP12 (p = 0.03), Candida (p = 0.0005), Bullera (p = 0.002), Cryptococcus (p = 0.007), and Ostracodinium (p = 0.01). LefSe analysis was performed to reveal the biomarker genera of the rumen microbiota community (bacteria, fungi, protozoan, and archaea) in the TMR and FTMR were the genera Shuttleworthia, Ruminococcus, Cryptococcus, Mycosphaerella, Bullera, Candida, and Ostracodinium. NH3-N concentration (p < 0.0001), total VFA concentration (p = 0.003), and molar proportion in total VFA of acetate (p = 0.01) were higher for the cows fed FTMR compared with the cows fed the TMR. Several bacterial genera showed significant correlations with rumen fermentation parameters. The genus Unclassified_Bacteroidales and Bullera were positively correlated with total volatile fatty acids (VFA) and acetate, whereas Candida and Ostracodinium showed negative correlations. Meanwhile, propionate was positively correlated with Candida and negatively correlated with Bullera. The PICRUSt functional profile prediction indicated that the xenobiotics biodegradation and metabolism, the lipid, amino acid, terpenoids, and polyketides metabolisms of the FTMR group were significantly higher than that of the TMR group. The results imply that FTMR can increase lipid and amino acid metabolism, and modulate the rumen microbiome and improve ruminal fermentation.

Effects of soil ingestion on nutrient digestibility and rumen bacterial diversity of Tibetan sheep

Tibetan sheep (Ovis aries) are the most numerous livestock in Tibet Plateau pasture ecosystem and have strong ecological adaptability. In the natural grazing system, soil as a natural nutrient carrier and involuntarily or intentionally ingested by Tibetan sheep contribute as an important feed approach. However, quantifying the dosages of soil ingestion for the Tibetan sheep still needs to be clarified. This study aims to characterize nutrient digestibility and rumen bacterial communities by Tibetan sheep in response to different levels of soil ingestion. Thirty sheep were selected and divided into five treatments with soil ingestion (0%, 5%, 10%, 15%, and 20%). The conclusion demonstrated that soil ingestion improved the dry matter digestibility (59.3-62.97%), ether extract (59.79-67.87%) and crude protein (59.81-66.47%) digestibility, particularly 10% soil ingestion has highest nutrient digestibility. The rumen fermentation environment adjusted after soil ingestion by improvement of pH, ammonia nitrogen and volatile fatty acids. Appropriate soil ingestion reduced the bacterial diversity ranged from 946 to 1000 OUTs as compared control (1012), and the rumen bacterial community dominant by typical fiber digestion associated Firmicutes (47.48-53.56%), Bacteroidetes (34.93-40.02%) and Fibrobacteres (4.36-9.27%). Especially, the highest digestible feed capacity and stronger environment adaptability present in 10% soil ingestion Tibetan sheep. Overall, soil ingestion stimulates rumen metabolism by creating a favorable environment for microbial fermentation, improved bacterial community abundance associated with cellulose and saccharide degradation, contribute nutrient digestibility and growth performance of Tibetan sheep.

Effects of Different Roughage Diets on Fattening Performance, Meat Quality, Fatty Acid Composition, and Rumen Microbe in Steers

This study aimed to evaluate different roughages on fatting performance, muscle fatty acids, rumen fermentation and rumen microbes of steers. Seventy-five Simmental crossbred steers were randomly divided into wheat straw group (WG), peanut vine group (PG) and alfalfa hay group (AG), with 5 replicates of 5 steers each. The results showed a highest average daily gain and lowest feed/gain ratio in AG group (P = 0.001). Steers fed alfalfa hay had the highest muscle marbling score and n-3 polyunsaturated fatty acid (PUFA), and also the rumen NH3-N and microbial protein (MCP) concentration among the three groups (P < 0.05). Correlation analysis showed that ruminal NH3-N and MCP were negatively correlated with muscle saturated fatty acid (SFA), while ruminal MCP was positively correlated with muscle PUFA and n-3 PUFA (P < 0.05). 16S rRNA analysis indicated that fed alfalfa hay decreased the abundance of Ruminococcaceae_UCG-001(P = 0.005). More importantly, muscle SFA deposition were positively correlated to the abundance of Ruminococcaceae_UCG-001 (P < 0.05), while the muscle PUFA and n-3 PUFA deposition were negatively correlated to it (P < 0.01). Therefore, alfalfa hay provides a better fattening effect on steers. Alfalfa rich in n-3 PUFA would reduce the abundance of Ruminococcaceae_UCG-001 involved in hydrogenation, increase the rumen protective effect of C18:3 n-3, which is beneficial to the deposition of muscle n-3 PUFA and PUFA.

Effects of Replacing Alfalfa Hay With Native Grass Hay in Pelleted Total Mixed Ration on Physicochemical Parameters, Fatty Acid Profile, and Rumen Microbiota in Lamb

This study aimed to investigate the effects of replacing alfalfa with native grass on growth performance, meat quality, and rumen microbiota of lambs. Forty-five 6-month-old Ujimqin lambs with live body weight (BW) of 29.50 ± 0.26 kg were used for the experiment, and the lambs were assigned to three diet treatments (three pens per treatment and five lambs per pen) with 30 square meters per pen in semi-open housing based on similar BW. The lambs have received 30% alfalfa (HA, high alfalfa percentage group), 20% alfalfa (MA, moderate alfalfa percentage group), and 10% alfalfa (LA, low alfalfa percentage group) diets, respectively (dry matter basis). The diet treatments had a significant (P < 0.05) influence on the dry matter intake of lambs and the dry matter intake increased with the increasing percentages of native grass hay, while the significantly (P < 0.05) lower final BW and average daily gain were observed in the MA and LA groups compared with that in the HA group. The diet had a significant (P < 0.05) difference in meat pH value, water loss rate, cooked meat rate, moisture, and intramuscular fat, while no significant (P > 0.05) difference was found in protein. As native grass hay percentages increased in the diet, the contents of palmitic (C16:0) and palmitoleic (C16:1 cis-9) in the HA and MA groups were significantly (P < 0.05) lower than that in the LA groups, and compared with the HA group, the contents of elaidic (C18:1 trans-9), oleic (C18:1 cis-9), and linoleic (C18:2 cis-9–cis-12) were significantly (P < 0.05) increased in the MA and LA groups. The content of α-linolenic (C18:3n3) was significantly (P < 0.05) higher in the LA group than that in the HA and MA groups. The principal coordinate analysis profile displayed that the composition of the bacterial community of these groups was distinctly separated from each other. No significant (P > 0.05) difference was observed in the dominant rumen bacteria at the phyla and genus levels. In conclusion, the meat quality and fatty acid profile analysis revealed that replacing alfalfa hay with native grass hay is more beneficial for Mongolian lambs, and the meat from LA diet treatment is better than the others. In addition, correlation analysis of the association of rumen microbiome with growth performance, meat quality, and fatty acid profile provides us with a comprehensive understanding of the composition and function of rumen microbiota. These findings could provide knowledge of how the diet affects the animal performance, meat quality of lambs, and microbiota of the rumen, laying a theoretical basis for replacing alfalfa with native grass.

Improvement of feed intake, digestibility, plasma metabolites, and lactation performance of dairy cows fed mixed silage of sugar beet pulp and rice straw inoculated with lactic acid bacteria

A study was conducted to investigate the inclusion effects of sugar beet pulp and rice straw mixture silage with inoculation (BRMS), in place of whole-plant corn silage (CS), on the dry matter intake, total-tract nutrient digestibility, plasma metabolites, rumen fermentation, and lactation performance in high-production dairy cows. Sixteen multiparous Holstein cows (body weight, 622 ± 35 kg; days in milk, 90 ± 11 d; mean ± standard deviation) were used in our experiments; the experiments were based on a repeated 4 × 4 Latin square design for 21 d, and each experimental period consisted of 14 d of adaptation, followed by 7 d of data collection. The 4 dietary treatments used were (dry matter basis): (1) 0% BRMS and 28.6% CS (0BRMS); (2) 4.3% BRMS and 24.3% CS (15BRMS); (3) 8.60% BRMS and 20.0% CS (30BRMS); and (4) 12.9% BRMS and 15.7% CS (45BRMS). The increasing inclusion of dietary BRMS was observed to linearly increase the total volatile fatty acids and the propionate concentration. The dry matter intake and digestibility values of neutral detergent fiber and acid detergent fiber increased linearly as the percentage of BRMS increased up to 45%. Milk yield linearly increased with the increase in the content of BRMS (39.0, 39.8, 40.9, and 40.3 kg/d for 0BRMS, 15BRMS, 30BRMS, and 45BRMS, respectively). The increasing inclusion of dietary BRMS induced a decrease in the ammonia nitrogen and milk urea nitrogen concentration, leading to a linear increase in milk protein production (1.15, 1.26, 1.35, and 1.27 kg/d for 0BRMS, 15BRMS, 30BRMS, and 45BRMS, respectively). In conclusion, the diets with the replacement of CS with BRMS up to 45% were beneficial to the production performance of high-production dairy cows, indicating that this method may be an appropriate use of sugar beet pulp and rice straw.

Comparison of the effect of sodium bicarbonate, sodium sesquicarbonate, and zeolite as rumen buffers on apparent digestibility, growth performance, and rumen fermentation parameters of Arabi lambs

The current research was conducted to compare the effect of various buffers or alkalizers in Arabi lambs and find new and less expensive buffering resources. Forty-five Arabi lambs with an average weight of 29.37 ± 3.63 kg were used in a completely randomized design with five treatments and nine replicates. Treatments included 1 - control diet (no buffer); 2 - base diet + 0.75% sodium sesquicarbonate, 0.75% sodium bicarbonate; 3 - base diet + 2% zeolite; 4 - base diet + 1.5% sodium bicarbonate; and 5 - base diet + 1.5% sodium sesquicarbonate. Results showed that rumen pH increased and ammonia nitrogen concentration decreased in diets containing buffer in comparison to control diet (P < 0.05). Rumen concentration of acetate and acetate to propionate ratio showed reduction in experimental diets compared to control (P < 0.05). The concentration of propionate in control diet increased significantly compared to diets receiving buffer (P < 0.05). Using 1.5% sodium bicarbonate in the diet causes a significant increase in rumen protozoa population compared to the control group (P < 0.05). There was no significant difference in dry matter intake and growth performance of lambs. Generally, the effects of using 2% of zeolite were competitive with the effects of other buffers, and caused an increase in the rumen pH and concentration of the acetate. Therefore, the use of buffer in fattening lambs ration fed moderate concentrate diets is beneficial, and it is possible to use low-cost zeolite buffer in the ration of livestock as an alternative to sodium bicarbonate and/or sodium sesquicarbonate.

Replacing Alfalfa with Paper Mulberry in Total Mixed Ration Silages: Effects on Ensiling Characteristics, Protein Degradation, and In Vitro Digestibility

Simple Summary

The usage of alfalfa (Medicago sativa L.) as a dietary protein source for ruminants in China is limited by forage quality and planting scale. Paper mulberry (Broussonetia papyrifera L., RY) has emerged as a new and representative high-protein woody forage resource for ruminants. However, information is less available regarding how substituting RY for alfalfa affect the fermentation and protein quality in total mixed ration (TMR) silages. This study evaluated ensiling characteristics, protein quality, and in vitro digestibility in TMR silages by mixing RY with alfalfa at different rations. The TMR were made with alfalfa and RY mixtures (36.0%), maize meal (35.0%), oat grass (10.0%), soybean meal (7.5%), brewers’ grain (5.0%), wheat bran (5.0%), premix (1.0%), and salt (0.5%) on a dry matter basis, respectively. The alfalfa and RY mixtures were made in the following ratios of dry matter: 36:0 (RY0), 27:9 (RY9), 18:18 (RY18), 9:27 (RY27), and 0:36 (RY36). The results showed that RY substitution had no adverse effect on fermentation quality and nutritional composition, but inhibited true protein degradation, while decreasing in vitro dry matter and crude protein digestibility. Therefore, RY and alfalfa mixtures at a ratio of 18:18 is suitable for silage-based TMR.

Abstract

To develop an alternative high-protein forage resource to alleviate ruminant feed shortages, we investigated the effects of replacing alfalfa (Medicago sativa L.) with different ratios of paper mulberry (Broussonetia papyrifera L., RY) on fermentation quality, protein degradation, and in vitro digestibility of total mixed ration (TMR) silage. The TMR were made with alfalfa and RY mixtures (36.0%), maize meal (35.0%), oat grass (10.0%), soybean meal (7.5%), brewers’ grain (5.0%), wheat bran (5.0%), premix (1.0%), and salt (0.5%) on a dry matter basis, respectively. The alfalfa and RY mixtures were made in the following ratios of dry matter: 36:0 (RY0), 27:9 (RY9), 18:18 (RY18), 9:27 (RY27), and 0:36 (RY36). After ensiling for 7, 14, 28, and 56 days, fermentation quality, protein degradation, and microbial counts were examined, and chemical composition and in vitro digestibility were analyzed after 56 days of ensiling. All TMR silages, irrespective of the substitution level of RY, were well preserved with low pH and ammonia nitrogen content, high lactic acid content, and undetectable butyric acid. After ensiling, the condensed tannin content for RY18 silages was higher than the control, but non-protein nitrogen, peptide nitrogen, and free amino acid nitrogen contents was lower, while the fraction B1 (buffer-soluble protein) was not different among all the silages. Dry matter and crude protein digestibility for RY27 and RY36 silages was lower than the control, but there was no difference between control and RY18 silages. This study suggested that ensiling RY with alfalfa inhibited true protein degradation, but decreased in vitro dry matter and crude protein digestibility of TMR silages, and that 18:18 is the optimal ratio.

Effects of replacing soybean meal with pumpkin seed cake and dried distillers grains with solubles on milk performance and antioxidant functions in dairy cows

Pumpkin seed cake (PSC), a byproduct of pumpkin seed oil processing, is used in ruminant feed as a beneficial protein source. Experiments were conducted to evaluate PSC as a substitute for soybean meal in the diets of lactating cows based on performance, rumen fermentation, antioxidant function and nitrogen partitioning. Six multiparous lactating cows were used in a replicated 3 × 3 Latin square experiment with 27-day periods. The cows were randomly divided into three treatment groups: group (1) was fed a diet containing no PSC (0PSC), and groups (2) and (3) were fed diets in which soybean meal was replaced with PSC and dried distillers grains with solubles (DDGS) at levels of 50% (50PSC) and 100% (100PSC), respectively. The diets were isonitrogenous and contained identical roughage but different proportions of PSC and DDGS. Replacement of soybean meal with PSC and DDGS did not influence rumen degradation, milk performance, rumen fermentation, DM intake or apparent total tract digestibility, and nitrogen partitioning between milk, feces and urine did not differ in the animals fed the three diets. However, compared with a diet containing no PSC, the total antioxidant capacity (P < 0.05) and antioxidant enzymes (total superoxide dismutase, glutathione peroxidase and catalase) activities (P < 0.05) were increased in the animals that received the 50PSC and 100PSC diets. In contrast, addition of PSC significantly reduced concentrations of aspartate transaminase (P < 0.05), alkaline phosphatase (P < 0.05) and malondialdehyde (P < 0.05) in the plasma. These results demonstrate that PSC can be completely substituted for soybean meal in the diet of dairy cows without any negative impact on milk performance, rumen fermentation or apparent digestibility and that this dietary change improves antioxidant functions and blood parameters in dairy cows, indicating that PSC has the potential for use as a feed source for dairy cows.

Effect of substituting wet corn gluten feed and corn stover for alfalfa hay in total mixed ration silage on lactation performance in dairy cows

Wet corn gluten feed (WCGF) is a high moisture feed containing rapidly digestible, non-forage fiber and protein. The objective of this study was to investigate the effect of substituting WCGF and corn stover for alfalfa hay in total mixed ration (TMR) silage on lactation performance and nitrogen balance in dairy cows. Nine multiparous Holstein dairy cows (BW = 532 ± 28.9 kg and day in milk = 136 ± 5.6 d; mean ± SD) were used in a replicated 3 × 3 Latin square design with 21-d periods (14 d of diet adaption and 7 d of sample collection). Groups were balanced for parity, day in milk, and milk production and consumed one of three treatment diets during each period. The treatment diets were fed as TMR and contained similar concentrate mixtures and corn silage but different proportions of roughage and WCGF. The three treatments were: (1) 0% WCGF, 0% corn stover, and 22.1% alfalfa hay (0% WCGF); (2) 6.9% WCGF, 3.4% corn stover, and 11.8% alfalfa hay (7% WCGF); and (3) 13.3% WCGF, 4.9% corn stover, and 3.9% alfalfa hay (13.3% WCGF). Compared to the 0% WCGF diet, the cows fed the 7% and 13.3% WCGF diets had a higher milk yield and concentration of milk fat, protein, lactose, and total solids. Effective degradability of DM was higher in the cows fed the 7% and 13.3% WCGF diets than it was with the 0% WCGF diet. Cows fed the 13.3% WCGF had a higher CP effective degradability and a lower rumen undegraded protein than cows fed the 0% WCGF diet. The concentration of ruminal volatile fatty acids and ammonia-N was higher in cows fed the 7% and 13.3% WCGF diets than cows fed the 0% WCGF diet. The fecal N was lower in cows fed the 7% and 13.3% WCGF diets than it was in cows fed the 0% WCGF diet. Milk N secretion and milk N as a percent of N intake were higher in cows fed the 13.3% WCGF diet than cows fed the 0% and 7% WCGF diets. In conclusion, it appears that feeding a TMR silage containing WCGF and corn stover in combination, replacing a portion of alfalfa hay, may improve lactation performance and nitrogen utilization for lactating dairy cows.

Effects of Sodium Formate and Calcium Propionate Additives on the Fermentation Quality and Microbial Community of Wet Brewers Grains after Short-Term Storage

Simple Summary

The objective of this study was to examine the effect of sodium formate and calcium propionate on the fermentation quality and microbial community of wet brewers grains (WBG) after short-term storage. Both additives improved the silage quality of WBG ensiled for 20 days to different extents. However, ensiled WBG treated with sodium formate had higher contents of dry matter, water-soluble carbohydrates, and neutral detergent fibers and better fermentation quality, rumen degradation, and microbial composition. The addition of sodium formate enhances the abundance of desirable Lactobacillus and reduces the abundance of undesirable microorganisms, including Clostridium. In summary, during short-term storage of high-moisture feed, sodium formate has a more beneficial preservation effect than an equivalent dose of calcium propionate.

Abstract

The objective of this research was to examine the effect of sodium formate (SF) and calcium propionate (CAP) on the fermentation characteristics and microbial community of wet brewers grains (WBG) after short-term storage. In the laboratory environment, fresh WBG was ensiled with (1) no additive (CON), (2) sodium formate (SF, 3 g/kg fresh weight), and (3) calcium propionate (CAP, 3 g/kg fresh weight) for 20 days. After opening, fermentation characteristics, chemical composition, rumen effective degradability, and the microbial community of ensiled WBG were analyzed. The addition of CAP had no effect on pH and lactic acid concentration and increased the concentrations of propionic acid; the SF group had the lowest pH and acetic acid, butyric acid, and ammonia nitrogen contents and the highest lactic acid concentration. After fermentation, the SF group had the highest contents of dry matter (DM), water-soluble carbohydrates (WSCs), and neutral detergent fiber (NDF). The contents of the three nutrients in the CAP group were significantly higher than those in the CON group. The addition of the two additives had little influence on the crude protein (CP) and acid detergent fiber (ADF) contents of the ensiled WBG. Two additives elevated in situ effective degradability of DM and NDF compared with the parameters detected in the CON group; WBG ensiled with SF had higher effective in situ CP degradability than that in the CON and CAP groups. The results of the principal component analysis indicate that the SF group and two other groups had notable differences in bacterial composition. The analysis of the genus level of the bacterial flora showed that the content of Lactobacillus in the SF group was significantly higher than that in the two other treatment groups, while the content of Clostridium was significantly lower than that in the two other treatment groups. Therefore, the addition of sodium formate can suppress the undesirable microorganisms, improve the fermentation qualities, and ensure that WBG is well preserved after 20 days of ensiling.

Effects of inclusion of corn gluten feed in dairy rations on dry matter intake, milk yield, milk components, and ruminal fermentation parameters: a meta-analysis

Corn gluten feed (CGF) is a co-product of wet milling that can replace energy or fiber ingredients in dairy cow rations. The present meta-analysis examines how inclusion of CGF can affect dry matter intake (DMI), milk yield (MY), milk components, and ruminal fermentation parameters. A literature search was conducted to identify papers published from 1990 to 2018. Effect size for all parameters was calculated as standardized mean difference with a 95% confidence interval. Heterogeneity was determined using Q test and I² statistic, while meta-regression was used to examine factors influencing heterogeneity. Results indicate that feeding CGF increased the effect size for DMI and MY. No differences were observed for effect size for percentage milk fat or protein; however, increases were observed in the effect size for milk fat yield, milk protein yield, milk lactose percentage, and milk lactose yield. Ruminal fermentation parameters revealed a decrease in the effect size for pH and acetate and an increase for propionate. No differences were observed in the effect size for total VFA or butyrate. The Q test demonstrated heterogeneity (P < 0.1) for MY, MFP, and pH. The results indicate differences in forage intake between groups receiving CGF and control as an important factor contributing to heterogeneity for DMI, MFP, and pH. It can be concluded from this meta-analysis that in addition to increased DMI, inclusion of CGF in cow diets increases MY and improves milk components. Furthermore, inclusion of CGF in the diet lowers ruminal pH while decreasing acetate and increasing propionate contents.

Estimating ruminal crude protein degradation from beef cattle feedstuff

We estimated ruminal crude protein degradation of twelve feedstuffs commonly used in China using in vitro and in vivo methods. The in vivo net protein utilization (NPU) levels of corn, sorghum, barley, wheat, Chinese wild rye grass, corn stalk, rice straw, soybean straw, soybean meal, distillers' dried grains with solubles (DDGS), Brewers' spent grains, and sunflower meal were 52.57, 49.68, 65.38, 72.58, 82.41, 72.26, 68.57, 76.95, 54.75, 56.27, 29.03 and 41.88%, respectively. The linear regression between NH3-N incorporated into microbial proteins and gas production after incubation (6, 12, and 24 h) was significant (r = 0.9948 and P < 0.001, r = 0.9874 and P < 0.01, and r = 0.9912 and P < 0.01, respectively). Based on the linear regression equations, we estimated in vitro protein degradability (IVPD) and generated the regression equations between IVPD and NPU. The linear regression equations between IVPD and NPU after 6 h incubation in the energy, protein, and roughage feed groups were Y = 0.5633X + 33.20 (R2 = 0.8517, P < 0.05), Y = 0.8482X+ 34.81 (R2 = 0.8650, P < 0.05), and Y = 1.6295X - 17.70 (R2 = 0.909, P < 0.05), respectively. The in vitro gas production method is useful for the determination of protein degradation in feedstuffs.

Nutrient digestibility, rumen microbial protein synthesis, and growth performance in sheep consuming rations containing sea buckthorn pomace

This experiment was conducted to investigate nutrient digestibility, rumen microbial protein synthesis, and growth performance when different proportions of sea buckthorn pomace (SBP) were included in the diet of sheep. A total of forty1/2 Dorper × 1/2 thin-tailed Han ram lambs (BW = 22.2 ± 0.92 kg, age =120 ± 11 d; mean ± SD) were selected and divided into four groups in a randomized design and were randomly allocated to one of four treatment diets. Diets were formulated isonitrogenously and contained different levels of SBP: 1) 0% SBP (control), 2) 7.8% of DM SBP (8SBP), 3) 16.0% of DM SBP (16SBP), and 4) 23.5% of DM SBP (24SBP). A portion of corn and forages were replaced with SBP. DMI and ADG increased linearly (P = 0.001), but feed efficiency was not affected (P ≥ 0.460) by increasing SBP inclusion rate. As the SBP inclusion increased, OM, NDF, and ADF digestibility decreased linearly (P ≤ 0.005) and that CP increased linearly (P = 0.012). Response to inclusion level of SBP was quadratic (P = 0.003) for the estimated microbial CP yield with the greatest at intermediate SBP levels. For intestinally absorbable dietary protein, quadratic (P = 0.029) effects were observed among treatments. The metabolizable protein (MP) supplies were linearly (P < 0.0001) improved with increasing SBP inclusion rate. The results indicated that SBP can be incorporated in the ration of ram lambs and improve MP supply and ADG. However, high content of it in the diet was adverse for nutrient digestibility. The optimal proportion was 16.0% under the condition of this experiment.