Cattle consuming low-quality forage may have decreased forage organic matter intake as a result of decreased nitrogen (N) intake. To date, a value has not been assigned to dried distillers' grains as a protein supplement to cattle consuming low-quality Bermudagrass forage. To address this shortcoming in the data, 13 duodenally and ruminally fistulated steers were arranged in an incomplete 13 x 4 Latin square with 13 treatments and 4 periods. Treatments were arranged as a 4 x 3 factorial plus a negative control (NC), which received no supplement. The first factor consisted of 4 levels of supplemental protein provided at 52, 104, 156, and 208 mg N/kg BW. The second factor consisted of one of three supplemental protein sources, cottonseed meal (CSM), dried distillers' grains (DDG), and dried distillers' grains plus urea (DDGU). Total digestible organic matter (TDOMI), and total organic matter intake (TOMI) increased in response to the increasing level of supplemental protein (P <0.01). Similarly, digestible neutral detergent fiber intake (DNDFI) increased as a result of supplementation (P = 0.06). Forage organic matter intake did not increase as a result of protein supplementation (P = 0.20). However, forage organic matter intake (FOMI) responded quadratically to provision of CSM (P = 0.02). In contrast, DDG and DDGU did not significantly increase FOMI. Organic matter digestibility (OMD) tended to increase (P= 0.09) as a result of protein supplementation. Ruminal ammonia concentrations increased linearly in response to increasing provision of supplemental protein and were greater than control steers (P less than 0.01). Supplementation with DDGU resulted in the greatest increase in ruminal ammonia concentrations. Plasma urea nitrogen (PUN) concentrations increased in a linear fashion in response to CSM and DDGU supplementation (P less than 0.01), while provision of DDG resulted in a quadratic response (P = 0.08). Based on these results, DDG can be utilized as a protein supplement to increase TDOMI, however, it accomplishes this without significantly impacting FOMI which is in contrast to CSM.

Microbial crude protein (MCP) is the main source of protein supplied to ruminants. Several studies report that the efficiency of MCP production (eMCP) from tropical forages is low due to low rumen degradable protein (RDP) content. The studies reported in this thesis determined the eMCP from tropical forages varying in crude protein (CP) and dry matter digestibility (DMD), examined strategies to increase eMCP and the possible practical methods of application under extensive cattle production systems. This was done through four metabolism experiments, one rate of digestion experiment and a preference test experiment. In Experiment 1, the eMCP of 3 tropical forages (speargrass (Heteropogon contortus), Mitchell grass (Astrebla spp) and pangola grass (Digitaria eriantha)), and temperate ryegrass (Lolium multiflorum cultivar aristocrat) was measured. All tropical forages were associated with low eMCP (102 - 110 g MCP/kg digestible organic matter (DOM)) due to low CP and RDP content. The RDP content of the tropical forages ranged from 43 - 103 g RDP/kg DOM compared to 214 g RDP/kg DOM in ryegrass. Retention time of Cr-EDTA and Ytterbium in the rumen ranged from 13 - 34 and 29 - 59 h for tropical forages respectively, compared to 10.2 and 13.2 h for ryegrass. In Experiment 2, the rate of digestion of speargrass, Mitchell grass and ryegrass varied when incubated in the rumen of steers consuming speargrass hay (1.8% CP). Addition of a variety of nitrogen supplements; urea-ammonium sulphate (US), US plus branch chain amino acids (leucine, isoleucine and valine) plus phenylalanine (USAA), casein, cottonseed meal (CSM), yeast and Chlorella (Chlorella pyrenoidea) algae to supply approximately 170 g RDP/kg DOM improved the rate of digestion of all three substrates. However, there was no difference in rate of digestion of the three substrates between the different nitrogen supplements. In Experiments 3 and 4, steers fed medium quality pangola grass hay (9.9% CP and 61% DMD) or low quality Mitchell grass hay (4.5% CP and 41% DMD) were supplemented with US, casein and USAA. US was provided at 130, 170, 210 and 250 g RDP/kg DOM. The USAA treatment was provided at a RDP/DOM of 170 with US and then amino acids (USAA) were provided in the same ratio and level as the amino acids in the casein treatment at 130, 170, 250 and 300 g RDP/kg DOM. Increased RDP intake from all supplements increased the rumen ammonia-N concentration for both hays. The molar percentage of branch chain fatty acids (BCFA) increased 3 - 4 fold (6.6% of total VFA) above control with increasing intake of USAA or casein supplements for both hays. However, eMCP did not increase in response to increasing RDP intake from either supplement for both hays. The RDP supplementation also had no effect on intake, rate of digestion and retention time of Cr-EDTA in the rumen. In Experiment 5, steers fed Mitchell grass hay (3.8% CP and 44% DMD) were supplemented with US and Spirulina (Spirulina platensis) algae. The US was supplied to provide 90, 130, 170 and 210 g RDP/kg DOM and the Spirulina supplied to provide 90, 130, 170 and 290 g RDP/kg DOM. Increased RDP intake from US and Spirulina was associated with linear and quadratic increases in eMCP respectively. The eMCP at the highest level of US (93 g MCP/kg DOM) was below the minimum feeding standards value of 130 g MCP/kg DOM, whilst the highest level of Spirulina reached the higher end of the feeding standards (166 g MCP/kg DOM). Increasing RDP intake resulted in increased hay DM intake and total DOM intake, which were both higher for the Spirulina than the US supplement (24.5 vs.18.5 g DM/kg W/d and 11.9 vs. 7.6 g DOM/kg W/d). The retention time of Cr-EDTA and lignin in the rumen decreased with increasing RDP intake and were both shorter with Spirulina compared with US supplementation (15 vs. 21 h for Cr-EDTA; 45 vs. 56 h for lignin). In addition, Spirulina increased the BCFA concentration to 4.2% of total VFA. In Experiment 6, four different concentrations of Spirulina solution were offered to steers fed restricted amounts (14 g DM/kg W/d) of pangola hay (3.4% CP). Drinking water containing Spirulina was highly preferred and had no deleterious effect on water or hay intake. Steers strongly preferred Spirulina solution to water, when offered both solutions. Approximately 20.5% of imbibed water by-passed the rumen, which was not influenced by the Spirulina concentration in the drinking water. It may be concluded that RDP is the primary factor affecting eMCP. High eMCP was associated with low retention time of water in the rumen and high intake. Once RDP is not limiting eMCP, a source of RDP rich in true protein, nucleic acids, fatty acids, vitamins and minerals, such as Spirulina algae, may be required for cattle fed low quality tropical hay to achieve the maximum eMCP reported in the feeding standards.

Three experiments were conducted to determine the effects of supplementing wheat-based dry distillers grains with solubles (DDGS) on cow performance, forage utilization, and production costs. In the first two experiments, 48 dry, pregnant Black Angus cows (mean BW±SD; 598.2±4.2 kg) stratified by body weight (BW) and days pregnant were allocated randomly to one of three replicated (n=2) treatments. Cows were managed on stockpiled crested wheatgrass pasture (TDN=49.0, CP=7.3 (% DM)) in experiment one (EXP 1) and barley straw-chaff residue (TDN=45.4, CP=8.6 (% DM)) in experiment two (EXP 2). EXP 1 supplement treatments were (1) 100% DDGS (70:30 wheat:corn blend; DDGS); (2) 100% commercial supplement (COMM); or (3) control no supplement (CONT). EXP 2 supplement treatments were (1) 100% DDGS (70:30 wheat:corn blend; DDGS); (2) 50% DDGS + 50% rolled barley (50:50); or (3) 100% rolled barley grain (control; BARL). Forage utilization was measured for both trials using the herbage weight disappearance method. Cow BW, body condition score (BCS), and rib and rump fat were measured at the start and end of trial and cow BW was corrected for conceptus gain based on calving data. There was no effect (P > 0.05) of treatment on forage utilization in either experiment. In EXP 1, cow performance was not affected (P > 0.05) by supplement strategy. In EXP 2, BW change was 11.3, 6.8, and -6.5 (P < 0.01) for DDGS, 50:50, and BARL, respectively. Because forage utilization was not affected, the difference in cow BW was the result of supplement type. Costs per cow per day in EXP 1 were $0.66, $0.68, and $0.60 for DDGS, COMM, and CONT, respectively. In EXP 2, costs per cow per day were $0.79, $0.80, and $0.80 for DDGS, 50:50, and BARL treatments, respectively.<p> In experiment three (EXP 3), four ruminally cannulated beef heifers were individually fed a basal ration of 75% ground barley straw and 25% ground grass hay (TDN=46.3, CP=7.5 (% DM)). Heifers were supplemented with either (1) DDGS (70:30 wheat:corn blend; DDGS); (2) commercial range pellet (COMM); (3) barley grain and canola meal (BAR+CM); or (4) control no supplement (CONT). Forage intake, apparent total tract digestibility, and passage rate; rumen fermentation parameters; and the rate and extent of forage degradation were measured. Forage intake, passage rate, and apparent total tract digestibility of DM, NDF, and ADF were not affected (P > 0.41) by treatment. Apparent total tract digestibility of CP was increased (P = 0.02) by supplementation, but was not different between DDGS, COMM, and BAR+CM treatments. Ruminal pH was not affected (P = 0.20) by treatment diet, but rumen ammonia-N was increased (P < 0.01) by supplementation. The potentially degradable and undegradable forage fractions were affected (P < 0.02) by supplementation, reducing the extent of forage degradation. Also, there was a tendency (P = 0.06) for the rate of forage DM degradation to increase when supplements were fed. The results of these experiments indicate that wheat-based DDGS can be used as a supplement for beef cows consuming forages with similar or greater effects compared to a commercial pellet and barley grain. DDGS had similar effects on rumen metabolism as the commercial range pellet or barley grain and canola meal, suggesting DDGS can be substituted on a unit basis with these supplements. As such, the inclusion of wheat-based DDGS as a supplement for beef cows will depend on the initial price of the supplement.

Three experiments were conducted to determine the effects of supplementing wheat-based dry distillers grains with solubles (DDGS) on cow performance, forage utilization, and production costs. In the first two experiments, 48 dry, pregnant Black Angus cows (mean BW±SD; 598.2±4.2 kg) stratified by body weight (BW) and days pregnant were allocated randomly to one of three replicated (n=2) treatments. Cows were managed on stockpiled crested wheatgrass pasture (TDN=49.0, CP=7.3 (% DM)) in experiment one (EXP 1) and barley straw-chaff residue (TDN=45.4, CP=8.6 (% DM)) in experiment two (EXP 2). EXP 1 supplement treatments were (1) 100% DDGS (70:30 wheat:corn blend; DDGS); (2) 100% commercial supplement (COMM); or (3) control no supplement (CONT). EXP 2 supplement treatments were (1) 100% DDGS (70:30 wheat:corn blend; DDGS); (2) 50% DDGS + 50% rolled barley (50:50); or (3) 100% rolled barley grain (control; BARL). Forage utilization was measured for both trials using the herbage weight disappearance method. Cow BW, body condition score (BCS), and rib and rump fat were measured at the start and end of trial and cow BW was corrected for conceptus gain based on calving data. There was no effect (P > 0.05) of treatment on forage utilization in either experiment. In EXP 1, cow performance was not affected (P > 0.05) by supplement strategy. In EXP 2, BW change was 11.3, 6.8, and -6.5 (P < 0.01) for DDGS, 50:50, and BARL, respectively. Because forage utilization was not affected, the difference in cow BW was the result of supplement type. Costs per cow per day in EXP 1 were $0.66, $0.68, and $0.60 for DDGS, COMM, and CONT, respectively. In EXP 2, costs per cow per day were $0.79, $0.80, and $0.80 for DDGS, 50:50, and BARL treatments, respectively.<p> In experiment three (EXP 3), four ruminally cannulated beef heifers were individually fed a basal ration of 75% ground barley straw and 25% ground grass hay (TDN=46.3, CP=7.5 (% DM)). Heifers were supplemented with either (1) DDGS (70:30 wheat:corn blend; DDGS); (2) commercial range pellet (COMM); (3) barley grain and canola meal (BAR+CM); or (4) control no supplement (CONT). Forage intake, apparent total tract digestibility, and passage rate; rumen fermentation parameters; and the rate and extent of forage degradation were measured. Forage intake, passage rate, and apparent total tract digestibility of DM, NDF, and ADF were not affected (P > 0.41) by treatment. Apparent total tract digestibility of CP was increased (P = 0.02) by supplementation, but was not different between DDGS, COMM, and BAR+CM treatments. Ruminal pH was not affected (P = 0.20) by treatment diet, but rumen ammonia-N was increased (P < 0.01) by supplementation. The potentially degradable and undegradable forage fractions were affected (P < 0.02) by supplementation, reducing the extent of forage degradation. Also, there was a tendency (P = 0.06) for the rate of forage DM degradation to increase when supplements were fed. The results of these experiments indicate that wheat-based DDGS can be used as a supplement for beef cows consuming forages with similar or greater effects compared to a commercial pellet and barley grain. DDGS had similar effects on rumen metabolism as the commercial range pellet or barley grain and canola meal, suggesting DDGS can be substituted on a unit basis with these supplements. As such, the inclusion of wheat-based DDGS as a supplement for beef cows will depend on the initial price of the supplement.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-02-09T18:53:53Z No. of bitstreams: 1 2016 - Leonardo Fiusa de Morais.pdf: 1229717 bytes, checksum: 4c0be638ee0ef0a26e196c1343e1858b (MD5) / Made available in DSpace on 2017-02-09T18:53:53Z (GMT). No. of bitstreams: 1 2016 - Leonardo Fiusa de Morais.pdf: 1229717 bytes, checksum: 4c0be638ee0ef0a26e196c1343e1858b (MD5) Previous issue date: 2016-07-29 / CAPES / The aim of this study was to evaluate the effect of ammoniated with different doses of urea in two treatment periods, and 3 different sources of urease on the nutritional value of elephant grass harvested after flowering in two chapters. The first chapter assessed the nutrition value of hay application of 2, 4, 6 and 8% of urea in two treatment periods (30 and 45 days) and control (not hay ammoniated). The second chapter evaluated the legume soybean, pigeon peas and jack beans sedds as urease sources, with the addition of 1, 2, 3 and 4% in ammoniated hay with urea and the control treatment (ammoniated hay with 4% urea without urease sources). The Experimental design was completely randomized in organized in double factorial arrangement with additional treatment. Dry matter (DM), ash, ether extract (EE), neutral detergent fiber (NDF), neutral detergent fiber corrected for the ash and the protein (NDFap), acid detergent fiber (ADF), cellulose, lignin, total nitrogen (TN), acid detergent insoluble nitrogen (ADIN), neutral detergent insoluble nitrogen (NDIN), Non protein N (NPN), in vitro gas production(Parameters: Vf1, k1, Vf2, K2 e L) and Carbohydrates fractioning were analysed. In the first study, was applied urea different doses at treatment periods, there was a difference (p<0,05) between the control and combination of factorial treatments for DM, EE, NDF, ADF, lignina, cellulose, NDFap, A + B1 fraction, B2 fraction, C fraction, TN, NPN, ADIN, NDIN, k1, L, Vf2, k2. Linear effect from dose was observed to NDFap, ADIN and NDIN and increasing dose to A+B1 fraction, TN, NNP. A quadratic effect for to Vf2, with point absolute maximum of 5,2% urea, and effect treatment period to Vf2 e K2, with higher and lower Vf2 K2 for hay treated 45 days. There was interaction (p<0,01) between sources of urease and level for NDF, ADF and lignin. The addition of 3% soybean or jack bean as a source of urease, resulted in lower NDF, and were not statistically different (p> 0.05), while pork beans had the highest NDF. There was a difference (P<0,05) between the control and combination of factorial treatments for NDF, A + B1 fraction. There was no interaction (p> 0.05) between source application level of urease, but was no effect (p <0.01) of urease source for NPN and ADIN. There was interaction (p <0.05) between source application level of urease to Vf1, but there was no interaction (p> 0.05) for k1, L, Vf2 and k2. Ammoniation urea and adding urease sources is an efficient method for chemical treatment of the elephant grass hay harvested after flowering, mainly by increasing the solubility fiber, in addition to the increased supply of non-protein nitrogen to rumen microorganisms, which resulted in improvement in vitro gas production of the kinetic parameters. / Objetivou-se avaliar o efeito da amoniza??o com aplica??o de diferentes doses de ur?ia em dois per?odos tratamento, e 3 diferentes fontes de urease, sobre o valor nutritivo do feno de capim-elefante colhido ap?s o florescimento, em dois cap?tulos. O primeiro cap?tulo avaliou o valor nutritivo do feno com aplica??o de 2, 4, 6 e 8% de ureia com base na mat?ria seca, em dois per?odos de tratamento (30 e 45 dias) e o controle (feno n?o amonizado),e o segundo que avaliou o efeito da adi??o de gr?os mo?dos das leguminosas soja, feij?o guandu e feij?o de porco como fontes de urease, em niveis de 1, 2, 3 e 4% com base na mat?ria seca do feno amonizado com 4% de ureia, e o tratamento controle (feno amonizado com 4% de ureia sem adi??o de fonte de ur?ase). O Delineamento experimental foi inteiramente casualizado em esquema fatorial duplo com tratamento adicional com 4 repeti??es por tratamento para os dois estudos. Foram realizadas as an?lises de mat?ria seca (MS), cinzas, extrato et?reo (EE), fibra em detergente neutro (FDN), fibra em detergente neutro corrigido para cinzas e prote?nas (FDNcp), fibra em detergente acido (FDA), celulose, lignina, prote?na bruta (PB), nitrog?nio insol?vel no detergente ?cido (NIDA) e produ??o cumulativa de g?s in vitro (Par?metros: Vf1, k1, Vf2, K2 e L) e o fracionamento de carboidratos. No primeiro estudo, houve diferen?a entre controle e a combina??o de tratamentos fatoriais para MS, EE, FDN, FDA, Lignina, celulose, FDNcp, fra??o A + B1, fra??o B2, fra??o C, NT, NNP, NIDA, NIDN, K1, L, Vf2, K2, e efeito (p <0,05) linear decrescente de dose de ureia para FDNcp, NIDA e NIDN e crescente de dose para fra??o A+B1, NT, NNP, efeito quadr?tico crescente de dose de ureia para Vf2 com ponto m?ximo absoluto de 5,2% de ureia.houve efeito de per?odo de tratamento para Vf2 e K2, com maior Vf2 e menor K2 para o feno tratado durante 45 dias. Houve intera??o (p<0,01) entre fonte de ur?ase e n?vel de fonte de ur?ase para FDN, FDA e lignina, sendo que a adi??o de 3,0% de soja ou feij?o guandu como fonte de ur?ase, resultaram em menores valores de FDN. Houve diferen?a (P<0,05) entre o controle e a combina??o de tratamentos fatoriais para FDN e fra??o A + B1 , mas n?o houve diferen?a (p > 0,05) entre o controle e a combina??o de tratamentos fatoriais para mat?ria seca, cinzas e extrato et?reo, mas foi observado efeito (p < 0,01) de fonte de ur?ase para extrato et?reo. N?o houve intera??o (p>0,05) entre fonte de ur?ase de n?vel de aplica??o, mas houve efeito (p<0,01) de fonte de urease para NNP e NIDA. Houve intera??o (p<0,05) entre fonte de ur?ase de n?vel de aplica??o para Vf1, mas n?o houve intera??o (p>0,05) para k1, L, Vf2 e k2. A dose m?nima de 5,2% de ureia durante um per?odo de 45 dias, proporcionou melhoria valor nutricional do feno de capim elefante. A amoniza??o com ureia e adi??o de fontes de ur?ase ? um m?todo eficiente para tratamento qu?mico do feno de capim elefante colhido ap?s o florescimento, principalmente pelo aumento da solubilidade fibra, al?m da maior oferta de nitrog?nio n?o proteico aos microrganismos ruminais, que resultou em melhoria dos par?metros cin?ticos de produ??o de g?s in vitro.

Master of Science / Animal Sciences and Industry / John R. Jaeger / Cattle consuming low-protein forage (<7% CP) require additional supplemental protein to maintain BW and BCS. Daily delivery of protein supplements places undue financial burden on cattle producers. Supplementing cows as infrequently as once every 6 d) has resulted in similar changes cow BW and BCS when compared to daily supplementation. As calving season nears, producers may wish to increase supplementation frequency. The responses to a change in supplementation frequency during the third trimester of gestation have not been widely investigated. Therefore, our objective in Study 1 was to evaluate the effect of altering supplementation frequency during late gestation on performance of spring-calving cows grazing low-quality, dormant native range and supplemented with dried distillers grains with solubles (DDG). Angus × cows (n = 238; mean age = 6 ± 2.5 yr; average initial BW = 618 ± 56.2 kg; average initial BCS = 5.7 ± 0.03) were stratified by age, BW, BCS, and assigned randomly to 1 of 4 treatments: 1) DDG daily (D1); 2) DDG once every 6 d (D6); 3) DDG daily from d 1 to d 60 and then every 6 d (D1-D6); 4) DDG every 6 d from d 1 to d 60 and then daily (D6-D1). Treatments were initiated 100 d prior to expected onset of calving. Cow BW and BCS were measured every 28 d. Cows were sorted daily before supplementation at 0830 h. Supplement delivery was calculated to meet dietary CP requirements. Increasing supplementation frequency 28 d prepartum negatively affected final BW and BW change from d 61-88 for the D6-D1 supplementation group (P < 0.05) compared to other supplementation groups. Cow BW change for the study (d 1-88) was also less (P < 0.02) for the D6-D1 group compared to other groups but was also affected (P < 0.01) by year. Under the conditions of our study, increasing supplementation frequency 28 d before calving was not a viable means of increasing prepartum cow performance. The development of replacement heifers is a significant expense for cow-calf producers. Reducing the cost of heifer development programs while achieving high pregnancy rates is an industry-wide goal. Therefore, our objective in Study 2 was to determine if DDGS was a viable replacement for an oilseed meal-based protein supplement when developing heifers on low-quality, dormant native range. Treatments consisted of daily supplementation of either 1.65 kg DM DDG (DDG; 0.57 kg CP) or 1.37 kg DM of a 73.6% soybean meal and 26.4% rolled sorghum grain mixture (SBM-S; 0.56 kg CP). Treatments were administered from 1/15 until 4/8 (84 d). Initial BW and BCS were not different between treatments (P ≥ 0.29). Final BW and BCS also did not differ (P ≥ 0.55) between treatments; moreover, rates of BW and BCS change were not different (P ˃ 0.30) between treatments. Proportions of heifers pubertal before ovulation synchronization, first service conception rates, and final pregnancy rates were not affected (P > 0.40) by treatment. Under the conditions of our study supplemental CP fed at a rate of approximately 0.56 kg daily was sufficient to promote growth and BCS change adequate for optimal reproductive performance; moreover, supplement ruminal degradability of CP did not influence heifer performance over an 84-d development period.

This study was conducted to determine if nutrient utilization and enteric methane (CH4) emissions could be improved in overwintering beef cows consuming low-quality forage supplemented with protein in the form of dried distillers grain with solubles (DDGS) in thermal-neutral and cold-stressed environments. Thirty mature, dry and non-pregnant beef cows were divided into three treatment groups and fed diets consisting of low-quality (6.0% crude protein; CP) forage with no DDGS (control, CON), 10% DDGS (borderline sufficient CP, 8.7% CP), or 20% DDGS (excess CP, 11.6% CP). Cold acclimatization did not appear to affect nutrient intake and digestibility by beef cows, but increased N and P excretion by 1.2x and 2.5x, respectively. Cold acclimatized cows reduced energy excretion by 26.8% (7.1 vs. 5.2 ± 0.30% GEI in fall and winter, respectively; P < 0.0001) in accordance with a 33.8% increase in rumen fluid rate of passage (ROP). Supplementation with DDGS improved digestibility of N and P (40.6 vs. 61.2 ± 2.45% N and -23.9 vs. 5.7 ± 5.95% P for CON and 20%DDGS, respectively; P < 0.0001) by increasing digestible substrate in the diet. Protein supplementation increased rumen NH3-N concentrations (1.5, 2.1 and 3.1 ± 0.15 mg 100 mL-1; P < 0.0001) enough to increase rumen fermentation efficiency, resulting in 18.5% lower enteric CH4 emissions when CP was fed in excess of animal requirements. Total excretion of N and P were increased two- and 45-fold, respectively, when excess CP was fed. Reduced enteric CH4 emissions as a result of cold acclimatization suggest an advantage for the Canadian beef herd in terms of environmental sustainability. Supplementing CP in excess of cow requirements may improve nutrient utilization and rumen fermentation efficiency, and mitigate enteric CH4 emissions in beef cows fed low-quality forage diets, but may also contribute to greater N and P loading of soil and ground water.

This study was conducted to determine if nutrient utilization and enteric methane (CH4) emissions could be improved in overwintering beef cows consuming low-quality forage supplemented with protein in the form of dried distillers grain with solubles (DDGS) in thermal-neutral and cold-stressed environments. Thirty mature, dry and non-pregnant beef cows were divided into three treatment groups and fed diets consisting of low-quality (6.0% crude protein; CP) forage with no DDGS (control, CON), 10% DDGS (borderline sufficient CP, 8.7% CP), or 20% DDGS (excess CP, 11.6% CP). Cold acclimatization did not appear to affect nutrient intake and digestibility by beef cows, but increased N and P excretion by 1.2x and 2.5x, respectively. Cold acclimatized cows reduced energy excretion by 26.8% (7.1 vs. 5.2 ± 0.30% GEI in fall and winter, respectively; P < 0.0001) in accordance with a 33.8% increase in rumen fluid rate of passage (ROP). Supplementation with DDGS improved digestibility of N and P (40.6 vs. 61.2 ± 2.45% N and -23.9 vs. 5.7 ± 5.95% P for CON and 20%DDGS, respectively; P < 0.0001) by increasing digestible substrate in the diet. Protein supplementation increased rumen NH3-N concentrations (1.5, 2.1 and 3.1 ± 0.15 mg 100 mL-1; P < 0.0001) enough to increase rumen fermentation efficiency, resulting in 18.5% lower enteric CH4 emissions when CP was fed in excess of animal requirements. Total excretion of N and P were increased two- and 45-fold, respectively, when excess CP was fed. Reduced enteric CH4 emissions as a result of cold acclimatization suggest an advantage for the Canadian beef herd in terms of environmental sustainability. Supplementing CP in excess of cow requirements may improve nutrient utilization and rumen fermentation efficiency, and mitigate enteric CH4 emissions in beef cows fed low-quality forage diets, but may also contribute to greater N and P loading of soil and ground water.