Rumen Degradable Protein Source Research Articles

116 In-situ degradability of hemp (Cannabis sativa L.) plant components in cattle

Abstract The 2014 and 2018 Farm Bills defined hemp (Cannabis sativa L.) as an agricultural commodity and removed it from the controlled substances list, developing a pathway for commercialization and increasing interest in cultivating hemp in the United States. Demand for therapeutic, cannabinoid-based hemp products is increasing, and, as not all of the plant components are utilized for these products, there will likely be significant quantities of hemp by-products created. As these by-products are cellulosic, they may be marketed as livestock feed, especially for ruminant animals. There have been limited studies into hemp as cattle feed. Accordingly, the objective of this study was to determine the in-situ degradability of different hemp components in beef cattle. We conducted an in-situ trial with three ruminally cannulated steers (IACUC #8497) and 16 unique hemp samples: leaves, flower, stalk, or whole plant cultivated with four different seed inoculants. Samples were incubated in the rumen for 0, 4, 6, 12, 24, 48, and 72 h and replicated across each steer. After samples were removed, they were rinsed and analyzed for partial dry matter (DM), DM, organic matter (OM), and crude protein (CP). Solubility fractions [immediately soluble (IS), potentially soluble (PS), and not soluble (NS)], rate of degradation (kd), and rumen degradability was determined for OM and CP. Rate of passage (kp) was set at 4.7%. As there were not differences across seed inoculant method, data were combined across plant components. For OM, the NS fraction was greatest for hemp stalks (12%) and least for leaves (7%). The PS fraction ranged 72-75% across plant components with the least value for stalks and greatest for leaves. Of the PS fraction, ruminal OM degradability was least for stalks (51%) and greatest for leaves (72%). For CP, the NS fraction of hemp stalks (16%) was greater than other fractions, which ranged from 6-8%. The PS fraction was approximately 76% for both whole plant and leaves, a vast majority of which (71-73%) was degradable, indicating these plant components provide a good source of rumen degradable protein. The IS fraction was greatest (20%) for hemp flower. Although hemp flower may be easily digested by ruminants, it does not have practical value because this plant component competes in the human market as the flower contains a high percentage of cannabinoids which have therapeutic properties. Ultimately, our data indicate that hemp leaves have nutritional and practical value as feed for beef cattle and that hemp stalks would likely not be well-utilized as a forage source. Before hemp can be integrated into the beef cattle industry as feed, additional research is required to determine the effects of feeding hemp on animal performance and evaluate uptake and retention of cannabinoids in body tissues.

156 In-situ degradability of hemp (Cannabis sativa L.) plant components in cattle

Abstract The 2014 and 2018 Farm Bills defined hemp (Cannabis sativa L.) as an agricultural commodity and removed it from the controlled substances list, developing a pathway for commercialization and increasing interest in cultivating hemp in the United States. Demand for therapeutic, cannabinoid-based hemp products is increasing, and, as not all of the plant components are utilized for these products, there will likely be significant quantities of hemp by-products created. As these by-products are cellulosic, they may be marketed as livestock feed, especially for ruminant animals. There have been limited studies into hemp as cattle feed. Accordingly, the objective of this study was to determine the in-situ degradability of different hemp components in beef cattle. We conducted an in-situ trial with three ruminally cannulated steers (IACUC #8497) and 16 unique hemp samples: leaves, flower, stalk, or whole plant cultivated with four different seed inoculants. Samples were incubated in the rumen for 0, 4, 6, 12, 24, 48, and 72 h and replicated across each steer. After samples were removed, they were rinsed and analyzed for partial dry matter (DM), DM, organic matter (OM), and crude protein (CP). Solubility fractions [immediately soluble (IS), potentially soluble (PS), and not soluble [NS]), rate of degradation (kd), and rumen degradability was determined for OM and CP. Rate of passage (kp) was set at 4.7%. As there were not differences across seed inoculant method, data were combined across plant components. For OM, the NS fraction was greatest for hemp stalks (12%) and least for leaves (7%). The PS fraction ranged 72-75% across plant components with the least value for stalks and greatest for leaves. Of the PS fraction, ruminal OM degradability was lowest for stalks (51%) and highest for leaves (72%). For CP, the NS fraction of hemp stalks (16%) was greater than other fractions, which ranged from 6-8%. The PS fraction was approximately 76% for both whole plant and leaves, a vast majority of which (71-73%) was degradable, indicating these plant components provide a good source of rumen degradable protein. The IS fraction was largest (20%) for hemp flower. Although hemp flower may be easily digested by ruminants, it does not have practical value because this plant component competes in the human market as the flower contains an increased percentage of cannabinoids which have therapeutic properties. Ultimately, our data indicate that hemp leaves have nutritional and practical value as feed for beef cattle and that hemp stalks would likely not be well-utilized as a forage source. Before hemp can be integrated into the beef cattle industry as feed, additional research is required to determine the effects of feeding hemp on animal performance and evaluate uptake and retention of cannabinoids in body tissues.

Comparison of milk production, intake, and total-tract nutrient digestion in lactating dairy cattle fed diets containing either wheat middlings and urea, commercial fermentation by-product, or rumen-protected soybean meal

The objective of this study was to evaluate the effects of a commercially available fermentation by-product in a diet containing adequate rumen-degradable protein (RDP) on milk performance, intake, and total-tract nutrient digestion in lactating dairy cattle. Primiparous (n = 48) and multiparous (n = 144) lactating dairy cattle were stratified by milk production and randomly allocated into 12 pens containing 4 primiparous and 12 multiparous animals each. Cattle averaged 118 d in milk and 712 kg of body weight at trial start. Treatment diets, on a dry matter (DM) basis, consisted of 42% corn silage, 13% alfalfa hay and silage, 20% grain corn, and 25% protein premix containing either soybean meal, wheat middlings, and urea (SBM+U), soybean meal and fermentation by-product (SBM+F), or soybean meal and rumen-protected soybean meal (RP-SBM). All 3 diets provided a similar level (DM basis) of neutral detergent fiber analyzed using α-amylase and sodium sulfite and corrected for ash content (31%), crude protein (CP, 14.9%), starch (26%), and metabolizable energy (2.7 Mcal/kg), and differed in sources of RDP. The trial consisted of a 2-wk adaptation and covariate period during which all cows were fed the RP-SBM diet and covariate measurements were taken. Pens were then randomly allocated to treatments, and weekly measurements of milk production, intake, body weight, and condition score were taken for 10 wk. All data were analyzed using the Proc Mixed procedure in SAS (SAS Institute Inc., Cary, NC). Increased DM intake was observed for cows fed SBM+F compared with cows fed SBM+U and RP-SBM (28.3 vs. 26.9 and 26.7 kg/d, respectively). Cows fed SBM+F produced more energy-corrected milk (45.3 kg/d) compared with cows fed SBM+U and RP-SBM (43.6 and 43.7 kg/d, respectively). Milk protein yield was also increased in cows fed SBM+F. No differences were observed with body weight or condition score gain throughout the trial. Apparent total-tract digestibility of fiber was decreased in cows fed SBM+F, likely as a result of increased intake. Responses are consistent with previous research in our laboratory that demonstrated a decrease in ruminal CP degradation, leading to an increase in metabolizable protein supply in the small intestine. The fermentation by-product might be useful in diets containing adequate amounts of RDP from soybean meal or alfalfa. The results from this experiment demonstrate beneficial milk performance responses to fermentation by-product when fed with a source of RDP.

Nitrogen source and concentration affect utilization of glucose by mixed ruminal microbes in vitro

The availability of rumen-degradable protein (RDP) changes the use of carbohydrates by ruminal microbes. However, the effects of RDP on the simultaneous use of carbohydrate and formation of microbial products are not well described, although such information is needed to understand the potential effect on nutrient supplies for ruminants. The objective of this in vitro study was to compare the effects of different levels of RDP (0.15, 0.31, 0.46 g of N/L) from tryptone (Tryp) or urea (Ur) on product formation from glucose in fermentations with mixed ruminal microbes. The study had a randomized complete block design with 2 replicated fermentation runs and destructive sampling at 0, 0.5, 1, 2, 3, 4, and 5 h. All rates given are first-order rate constants. Glucose disappearance rates and organic acid carbon (C) production rates tended to be or were greater for Tryp (0.64 and 0.58 h-1) than for Ur (0.51 and 0.22 h-1), respectively, but did not differ by N level. Maximum detected microbial N production was 67% greater for Tryp (2.35 mg) than for Ur (1.41 mg), which did not differ from the basal medium (1.47 mg). The pattern of glycogen accumulation over time tended to differ between Tryp and Ur: glycogen peaked and declined earlier in the fermentations with Tryp, resulting in less glycogen remaining at 5 h with Tryp (7.2 mg) than with Ur (11.0 mg). At the point of maximum microbial N accumulation, Tryp and Ur did not differ in the amount of glucose C used (29.4 and 28.9 mg), but did differ in the amounts of cell C (10.1 and 6.0 mg), organic acid C (17.4 and 13.8 mg), glycogen C (3.81 and 6.07 mg), and total microbial product C (35.4 and 29.6 mg) present. This resulted in increased efficiency for Tryp compared with Ur for cell C produced per used glucose C, corrected for glycogen C (0.40 and 0.27 mg/mg), and it resulted in a tendency for increased yield of cell C per organic acid C (0.59 and 0.44 mg/mg). Total product C exceeded used glucose C for Tryp, likely because of incorporation or fermentation of C from the provided AA. Overall, RDP source altered the temporal patterns of glucose use and the patterns and amounts of microbial product formation.

Performance of beef cows and calves fed different sources of rumen-degradable protein when grazing stockpiled limpograss pastures.

Two experiments evaluated the effects of different sources of RDP on forage characteristics, animal performance, and ruminal and blood parameters of beef cattle grazing stockpiled limpograss (Hemarthria altissima) from January to May 2011 and 2012. In Exp. 1, 24 mature lactating beef cows and their respective calves were allocated to 8 stockpiled limpograss pastures (3 pairs/pasture). Treatments were 2 different sources of RDP, urea or cottonseed (Gossypium spp.) meal (CSM), distributed in a completely randomized design with 4 replicates. Feather meal and corn (Zea mays) meal were added to the urea treatments to balance RUP and energy. Treatments were mixed in sugarcane (Saccharum officinarum) molasses, which resulted in 3 kg DM/cow per day of supplement. There were no differences (P > 0.10) in herbage mass (HM; 3,200 ± 400 kg DM/ha), herbage allowance (HA; 1.9 ± 0.2 kg DM/kg of BW), CP (5.2 ± 0.2%), and in vitro digestible organic matter (IVDOM; 47 ± 0.5%) concentrations. There was a decrease (P < 0.10) in HM (from 4,100 to 2,600 kg/ha), IVDOM (from 46 to 39.9%), and HA (from 2.5 to 1.4 kg DM/kg BW) from January to March. Cow ADG (0.23 ± 0.08 kg/d), BCS (4.6 ± 0.2), milk yield (7.0 ± 0.4 kg/d), and plasma urea nitrogen (PUN; 16.1 ± 0.8 mg/dL) and calf ADG (0.71 ± 0.05 kg/d) were similar (P > 0.10) among treatments. Sixteen cow-calf pairs were moved to 8 drylot pens after Exp. 1, maintained on the same treatment, and evaluated for forage and total DMI. There was no difference in forage (P = 0.16; 2.1 ± 0.1% BW) and total DMI (P = 0.12; 2.5 ± 0.1% BW) between treatments. In Exp. 2, 2 rumen-cannulated steers were used in a 2 × 2 Latin square design, replicated in 2011 and 2012, to test the effects of the same treatments on rumen fluid and blood parameters. There was no difference (P > 0.10) in ruminal NH3-N (12.9 ± 0.3 mg/dL), pH (6.5 ± 0.1), propionic acid (25 ± 2.2 mol/100 mol), acetic acid (69.2 ± 2.9 mol/100 mol), and butyric acid (4.5 ± 0.5 mol/100 mol) as well as branched-chain VFA (1.3 ± 2.2 mol/100 mol) concentrations in the rumen. In addition, there was no difference (P = 0.91) in PUN (7.9 ± 0.3 mg/dL) concentration between treatments. Therefore, urea can be as effective as CSM as the main source of RDP in the molasses-based supplement offered to mature lactating beef cows grazing stockpiled limpograss pastures.

Suplementação energética e proteica de um volumoso de baixa qualidade pela técnica de produção cumulativa de gás in vitro

Um experimento foi conduzido utilizando-se a técnica semiautomática de produção cumulativa de gás in vitro com o objetivo de avaliar a combinação da suplementação energética com a proteica em dietas à base de um volumoso de baixa qualidade, feno de capim-tifton (Cynodon dactylon L.), com 7,69% de proteína bruta, 70,34% de fibra em detergente neutro e 57,98% de digestibilidade in vitro da matéria orgânica. Foram avaliadas duas fontes de proteína degradável no rúmen (ureia ou proteína isolada de soja); quatro níveis de grão de milho moído (0, 20, 40 e 60%) e quatro níveis suplementares de proteína degradável no rúmen (0; 2,8; 5,6 e 8,4%) em delineamento completamente casualizado em um fatorial 2 × 4 × 4. A digestibilidade in vitro da matéria orgânica aumentou linearmente em resposta à inclusão de milho com inclinação maior utilizando proteína isolada de soja. O fator de partição foi superior com proteína isolada de soja e foi detectado aumento linear em resposta ao aumento da proteína degradável com 20% de milho. A produção máxima de gás da fração de rápida (A) e de lenta (D) degradação aumentou linearmente em resposta à inclusão de milho, com proteína isolada de soja, e quadraticamente com ureia. A taxa de degradação de A aumentou com a inclusão de até 20% de milho e a taxa de degradação de D foi maior com ureia. O lag-time de A aumentou linearmente em resposta a inclusão de milho e no lag-time de D foi observada diminuição com até 20% de milho sem alterações em níveis superiores. A suplementação com até 60% de milho moído foi benéfica para a digestibilidade de dietas com volumoso de baixa qualidade. A associação entre energia e proteína foi benéfica em alguns parâmetros estudados. A ureia gerou melhores respostas em níveis moderados de grão de milho moído.

Effects of ratios of non-fibre carbohydrates to rumen degradable protein in diets of Holstein cows: 2. Rumen and plasma parameters and nitrogen metabolism

Nine multiparous mid-lactation Holstein cows, averaging 171 ± 17 days in milk and producing 24.1 ± 3.3 kg of milk/d were assigned to a replicated 3 × 3 Latin square design to study the effects of altering the non-fibre carbohydrates (NFC) to rumen degradable protein (RDP) ratios on rumen and plasma parameters and nitrogen (N) metabolism. Diets were based on a barley concentrate and 45 forage to 55 concentrate ratio. Rumen degradable protein (g/kg) and NFC : RDP ratios averaged 98 and 4.10; 108 and 3.71 and 118 and 3.34 for the LRDP, MRDP and HRDP treatment diets, respectively (dry matter (DM) basis). Ratios were achieved through altering the RDP content of the diets while NFC was held constant at 401 g/kg DM. Urea was supplemented as a source of RDP to decrease the ratio. The effect of treatments on NH3-N concentration in rumen fluid and plasma urea nitrogen (PUN) was significant and increased linearly. Nitrogen intake, absorbed N and urinary N increased linearly between LRDP to HRDP. As a proportion of N intake, faecal N tended to decrease linearly from the LRDP diet to the HRDP diet, i.e. as dietary RDP increased. As a proportion of N apparently absorbed, milk N tended to decrease linearly from LRDP to HRDP as dietary the NFC: RDP ratio decreased. Results showed that indicators of the metabolic efficiency of N were more affected than milk yield, confirming that low producing cows are less likely to respond to altering NFC : RDP ratios. Hence, balancing rations to further improve the N utilization efficiency may be of a higher priority. Keywords: Dairy cow, nitrogen metabolism, non-fibre carbohydrates, rumen degradable protein

Effects of ratios of non-fibre carbohydrates to rumen degradable protein in diets of Holstein cows: 1. Feed intake, digestibility and milk production

To evaluate the effect of different ratios of non-fibre carbohydrates (NFC) to rumen degradable protein (RDP) on lactation responses, digestion and dry matter intake (DMI), nine multiparous mid-lactation Holstein cows, averaging 171 +-17 days in milk and 24.1+-3.3 kg of milk/d were assigned to a 3 x 3 Latin square design. The total mixed rations (TMR) included 45% forage on a dry matter (DM) basis and 55% concentrates. The RDP (g/kg of DM) and NFC : RDP ratios of diets were respectively: 1) 98 and 4.10 (LRDP), 2) 108 and 3.71 (MRDP), 3) 118 and 3.34 (HRDP). Ratios were achieved through altering the RDP content of the diets while the NFC was held constant at 401 g/kg of DM. Urea was supplemented as a source of RDP to decrease the ratio. DMI and organic matter intake (OMI) were affected by treatment and tended to decrease linearly from LRDP to HRDP. Crude protein intake (CPI) increased linearly as the amount of RDP in the diets increased. Apparent organic matter digestion in the total tract decreased significantly in the HRDP diet. Percentage of protein and solid non-fat (SNF) and concentration of milk urea-nitrogen (MUN) in milk increased linearly when cows were fed diets with the higher amounts of RDP. Results showed that low producing cows are less likely to respond to altering NFC : RDP ratios than high producing cows, but digestibility in the MRDP treatment was higher and RDP level equal to 108 (g/kg of DM). A NFC : RDP ratio equal to 3.71 was useful and recommendable for mid-lactation dairy cow. Keywords: Dairy cows, milk production, non-fibre carbohydrates, rumen degradable protein

The Relative Merit of Ruminal Undegradable Protein from Soybean Meal or Soluble Fiber from Beet Pulp to Improve Nitrogen Utilization in Dairy Cows

Early lactating dairy cows were used to determine whether the replacement of solvent-extracted soybean meal [SSBM; a source of rumen-degradable protein (RDP)] with expeller soybean meal (ESBM; a source of rumen-undegradable protein), or the replacement of high-moisture shelled corn (HMSC) with beet pulp (a source of soluble fiber) would be effective in improving efficiency of N usage for milk production. The study was designed as a replicated 4×4 Latin square with 21-d periods. Eight multiparous Holstein cows were fed, ad libitum, the following diets, which were based on alfalfa silage and HMSC, and formulated to be isocaloric: 1) basal diet without a protein supplement (negative control diet: NC); 2) NC supplemented with solvent-extracted SBM (diet SSBM); 3) NC supplemented with expeller SBM (diet ESBM); 4) SSBM in which unmolassed dried beet pulp replaced half of the HMSC (diet SSBMBP). Compared with diet NC, protein supplementation increased intake of organic matter and dry matter. Milk and milk protein yields were lower with NC but this diet resulted in the greatest efficiency of N usage for milk production (30% milk N/N intake). Supplementation with ESBM, a proven source of RUP, increased plasma concentrations of histidine and branched-chain amino acids, and reduced milk urea N concentration, but failed to improve the yields of milk or milk protein. Milk fat yield tended to decrease with RUP supplementation. Replacing part of HMSC with soluble fiber from beet pulp (SSBMBP) tended to decrease milk production compared with SSBM; the effect was due to a reduction in dry matter intake. There were no differences among diets SSBM, ESBM, or SSBMBP in urinary excretion of purine derivatives. Neither substitution of ESBM for SSBM nor partial replacement of HMSC with beet pulp altered the efficiency of N usage for milk production or manure N excretion.

Effects of type of supplemental carbohydrate and source of supplemental rumen degradable protein on low quality forage utilization by beef steers

This study was conducted to assess the impact of type of supplemental non-fiber carbohydrate (NFC) and source of supplemental rumen degradable protein (RDP) on low quality forage intake, ruminal fermentation, and total tract digestion. Twelve ruminally fistulated beef steers (average initial body weight (BW) 500±22 kg) given ad libitum access to a low quality grass hay (53 g/kg crude protein; 748 g/kg neutral detergent fiber (NDF)) were used in a two period, two treatment crossover design nested within a six treatment completely randomized design. Periods consisted of an 11 day adaptation to treatments, a 5 day interval for intake and digestibility determination, and a 2 day ruminal sampling interval. Treatments were arranged as a 2×6 factorial and consisted of two different NFC types (corn starch and dextrose; fed at 1.6 g/kg of initial BW) each offered with an equal amount of RDP (0.87 g/kg of initial BW) but with six different proportions of non-protein nitrogen (NPN; supplied as urea) and true protein (supplied as casein) as sources of RDP. Proportions of supplemental N from urea, expressed as a percent of the supplemental RDP, were: 0, 20, 40, 60, 80 and 100. Treatments were dosed ruminally once daily. There were no NFC type×RDP source interactions for forage intake, digestion, or passage rate. Forage organic matter (OM) and total digestible OM intakes decreased linearly ( P<0.05) in response to increased supplemental N from urea. However, NFC type did not affect intake. Digestibilities of OM and NDF were higher ( P=0.05 and 0.06, respectively) when dextrose was provided compared with starch. Rumen solids passage rate initially decreased but then plateaued (quadratic; P=0.06) in response to increasing supplemental N from urea, and it was slower ( P=0.02) for dextrose versus starch fed steers. The NFC types evaluated did not interact with source of supplemental RDP with regard to intake and digestion, although both exerted independent effects on these characteristics. Forage digestion was affected by the provision of sugar versus starch, whereas the relative proportion of true protein versus NPN in the supplemental RDP affected forage intake.

Concentrados protéicos para bovinos: 1. Digestibilidade in situ da matéria seca e da proteína bruta

O objetivo deste trabalho foi determinar a degradação ruminal, pela técnica in situ, da matéria seca (MS) e da proteína bruta (PB) de 10 concentrados protéicos. As degradações potenciais da MS e da PB das farinhas de origem vegetal, soja, algodão, mamona e palmiste, mostraram-se elevadas (próximas a 100%), porém em função de taxas de degradação mais altas para o farelo de soja (10%) e menores para o algodão (4%), mamona (MS:3%; PB:1,2%) e palmiste (1,7%), as degradabilidades efetivas (DE) foram bem superiores para o farelo de soja, independentemente da taxa de passagem, o que a torna a fonte protéica de maior disponibilidade ruminal. O glúten de milho mostrou ser uma fonte protéica de baixa degradabilidade ruminal (DE da PB: 16% para 0,05 de taxa de passagem). Dentre os alimentos de origem animal, a maior degradabilidade potencial da proteína bruta foi verificada para a farinha de carne e ossos ( 75,5%), seguida das farinhas de peixe I (58,5%), de penas e vísceras (52,3%) e de sangue (36,7%). A maior degradabilidade efetiva para a taxa de passagem de 5% foi a da farinha de carne e ossos (51%), seguida da farinha de peixe I (41%), de penas e vísceras (40,0%) e de sangue (33%). A farinha de peixe II apresentou valores muito baixos de degradabilidade, apenas 22% com 48h de incubação ruminal.

Effects of Rumen Undegradable Protein and Minerals Proteinate on Early Lactation Performance and Ovarian Functions of Dairy Cows in the Tropics

A 90 d study was designed to investigate the effects of rumen undegradable protein (RUP) and a mixture of Cu, Zn and Mn proteinate (CZMP) on milk yield and composition and ovarian functions during rainy months. Twenty four Holstein× indigenous cows in their 2nd and 3rd lactation were randomly allocated to total mixed rations (TMR) containing soy bean meal (SBM) as a source of rumen degradable protein (RDP), SBM plus CZMP, and formalin treated SBM (FSBM) as a source of RUP. Maximum and minimum temperature humidity index during the experimental period were 83.6-84.7 and 75.4-76.1. There were no differences (p>0.05) in intakes of dry matter, crude protein and net energy and in contents of butterfat, lactose and minerals. Cows on TMR containing FSBM not only lost less weight (-278, -467 and -433 g/d) with more intake of RUP (0.92, 0.58 and 0.59 kg/d) but also produced more milk (19.27, 18.23 and 18.13 kg/d) and 4% fat corrected milk (18.57, 17.57 and 17.51 kg/d) with more protein (3.06, 2.81 and 2.80%), solids-not-fat (8.69, 8.38 and 8.38%) and less milk urea N (9.3, 15.4 and 15.0 mg/dl) compared with those on TMR containing SBM and SBM+CZMP, respectively (p 0.05). Whereas incidence of cystic ovaries at 20 and 90 d pospartum was less (p<0.01) in cows on TMR containing SBM+CZMP (37.3 and 12.5%) than those on TMR containing SBM (62.5 and 25%), it was nil for cows on TMR containing FSBM. Cows in all three group differed (p<0.01) from each other for the recurrence of first observed estrus with those on TMR containing FSBM having least days (22, 36 and 47 d) compared with their counterpart on TMR containing SBM+CZMP and SBM, repectively. The results suggest that RUP is one of the limiting factors affecting milk yield and its composition and ovarian functions during early lactation of dairy cows in the tropics. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 6 : 806-811)

Source and level of crude protein for implanted finishing steers

One hundred medium-framed, crossbred steers (738 lb) were used to compare nonprotein nitrogen to natural protein supplementation of finishing diets for implanted steers. Diets were formulate d to contain 11.5 or 13.5% crude protein and were supplemented with either urea or soybean meal. A fifth treatment of cottonseed meal supplementation (13.5% dietary crude protein) was added to evaluate differences between natural sources of rumen degradable protein. Steers were implanted with Revalor® and fed for 132 days. During the first 70 days, daily gain and feed efficiency were improved 8.8 and 6.1%, respectively, for steers supplemented with soybean meal vs urea. No difference was observed with protein level. For the entire feeding period, soybean meal increased dry matter intake 3.8% compared to urea. Protein source and level interacted on daily gain. Increasing dietary protein from 11.5 to 13.5% decreased gain by urea-fed steers 8%, whereas increasing dietary protein fr om 11.5 to 13.5% increased gain 6.1% for steers supplemented with soybean meal. Soybean meal improved feed efficiency 7.6% compared to urea. Protein level had no effect on feed efficiency. Steers supplemented with soybean meal had larger loineye areas than those supplemented with urea. Carcass finish, percentage of carcasses grading Choice, and yield grade were not affected by treatment . Performance and carcass traits of steers fed cottonseed meal were similar to those of steers fed soybean meal. We conclude that urea cannot meet the metabolizable protein needs of implanted finishing steers. Cottonseed meal did not differ from soybean meal as a protein source in this study.

Whey as a Source of Rumen-Degradable Protein. I. Effects on Microbial Protein Production

Whey as a Source of Rumen-Degradable Protein. I. Effects on Microbial Protein Production

Whey as a Source of Rumen-Degradable Protein. II. For Growing Ruminants

Whey as a Source of Rumen-Degradable Protein. II. For Growing Ruminants

The effect of three sources of rumen degradable protein on the digestibility of hay and silage diets fed to sheep

Protein supplementation of silage diets using fishmeal can increase both the voluntary intake of silage and liveweight gain in young growing calves. In association with these responses, increases in ration digestibility have also been observed which are not predicted by ARC (1980) (Bax, J.A. and Offer, N.W., 1982). Similar unpredicted responses have also been observed in older cattle (Waterhouse, A., Laird, R., Holliday, R.J., 1983). ARC (1980) assumes that increases in digestibility following supplementation with RDP occur only if the basal diet provides less than 7.8 g RDP/MJ ME irrespective of the source of RDP. The objective of the present study was to subject the microbial requirements proposed in ARC (1980) to a critical evaluation.