Biomedical subjects
Publications and source records attributed to C J Sniffen.
This article describes the National Research Council Model of protein metabolism and illustrates its use in meeting the protein requirements of lactating cows. Attention is then directed toward amino acid nutrition with emphasis on the need for models to estimate amino acid requirements. Finally, the potential to improve productivity with rumen-protected amino acids is considered.
The accuracy with which the Streptomyces griseus, ficin, and neutral protease with amylase in vitro methods could be used to predict in situ protein degradation of concentrate feeds was evaluated. Four types of soy products and two types of distillers grains were incubated using each of the four techniques for .5, 1, 2, 4, 8, 12, 24, and 48 h. The percentages of initial CP that remained undegraded over time were determined. Comparison of the degradation curves and contrast analysis of the data indicated that the in vitro methods generated degradability estimates in conflict with those obtained by the in situ method. However, the neutral protease with amylase method ranked the test feeds according to the extent of CP degradation at 24 h most similar to that in situ. Regression equations developed with the neutral protease with amylase degradability estimates explained 78, 76, and 74% of the variation in the in situ estimates obtained after 12, 18, and 24 h of incubation, respectively. At least 69% of the variation in the 18-h in situ estimates could be explained by the neutral protease with amylase estimates obtained after 1, 2, 4, 8, and 12 h of incubation. Little relationship was found between the ficin and S. griseus versus in situ results. Although none of the in vitro methods resulted in degradation curves consistently related to those generated by the in situ technique, relationships were found between protein degradability estimates obtained by the neutral protease with amylase method at specific time points and those obtained by the in situ technique.
Two experiments were conducted to ascertain lysine required for maintenance and milk production in lactating dairy cows. Multiparous Holstein cows fitted with abomasal cannulas were utilized in a replicated 3 x 3 extra-period Latin square design and infused with 0, 45, or 90 g of L-lysine-HCl daily (Experiment 1). In Experiment 2, 12 cows were utilized in a 5 x 5 Latin square design (with 2 replacement cows) and infused with 0, 22.5, 45, 90, and 180 g of L-lysine-HCl daily. Cows were housed in comfort stalls, milked at 0600 and 1700 h, exposed to a 16:8 h light:darkness cycle, and fed for ad libitum intake a 15.7% CP diet formulated to contain approximately 75% of dietary protein from corn-based feed ingredients. Milk yield was not affected in Experiment 1, but milk production increased linearly with lysine infusion level in Experiment 2. A linear response in daily yield of milk protein to lysine infusion was observed in both experiments. As lysine infusion increased, coccygeal plasma lysine concentrations tended to increase in Experiment 1, but in Experiment 2 free lysine increased linearly and quadratically in coccygeal plasma and increased linearly in plasma from the subcutaneous abdominal vein. The quadratic response in plasma free lysine (Experiment 2) suggested that lysine was the limiting AA for milk production from the composite protein flow to the small intestine. Using break-point analysis of plasma free lysine, it was estimated that the additional amount of abomasal lysine required to satisfy requirements was 64 g/d in cows producing about 30 kg of milk daily. Although additional lysine above microbial and undegraded intake protein lysine flow stimulated milk protein production, conversion efficiency to milk protein lysine was low.
Multiparous Holstein cows at six universities were utilized to examine effects of ruminally protected methionine and lysine on lactational performance. Three hundred and four cows began the study; 259 cows were included in the production analysis. Following a 21-d standardization period, cows received a basal diet of corn silage and ground corn supplemented with one of five dietary treatments, which were supplements of soybean meal or corn gluten meal, the latter with zero and three combinations of protected methionine and lysine (methionine; methionine and lysine; methionine and double (2x) lysine). Treatment effects were evaluated during early, mid, late, and total lactation (22 to 112, 113 to 224, 225 to 280, and 22 to 280 d postpartum, respectively). On a DM basis, ratios of forage to concentrate (50:50, 60:40, and 70:30) increased, and dietary CP (16.0, 14.5, and 13.0%) decreased during the three periods of lactation. Amount of amino acid supplementation also decreased (15, 12, and 9 g/d methionine; 20, 16, and 12 g/d lysine; and 40, 32, and 24 g/d 2x lysine) with period of lactation. Actual and least squares means for milk, FCM, and milk protein yields were greater for soybean than for corn gluten meal during early, mid, and total lactation. In addition, these variables responded linearly to lysine in early lactation. Response to lysine was quadratic during mid and total lactation for these variables. Differences in nutrient intake explained production responses to protein sources but not to lysine. Serum amino acid responses primarily reflected differences in dietary protein source and rumen-protected amino acid.
The objectives of this study were to observe endocrine and reproductive responses of cows and heifers fed two diets (16 and 19% CP), which met undegradable protein requirements but differed in rumen degradable protein. Cows (n = 33) and heifers (n = 32) were randomly assigned within parity to diets at calving and remained on diets for 20 d after first breeding. Energy balance was determined twice weekly through the first luteal phase. Blood and milk samples were taken three times per week. Diet did not affect average daily energy balance, days to negative energy balance nadir, days to first ovulation, days to first service, or plasma glucose concentrations. First service conception rate was lower (31% vs. 48%) and plasma urea higher in animals fed the high protein diet. Days to energy balance nadir was correlated with days (r = .75) to first ovulation. Luteinizing hormone pulse frequency increased and pulse amplitude decreased in frequent samples (12-min intervals for 8 h) collected at 14 d postpartum versus sampling after the energy balance nadir. These data suggest that energy balance status plays an important role in determining the postpartum return of cyclic ovarian activity. Feeding excess CP as rumen degradable protein elevated plasma urea concentrations and decreased first service conception rate.
The relationship of body condition score with disease occurrence was examined in 561 cows in nine herds. Cows were body condition scored on a five-point scale (1 = thin, 5 = obese) every 2 wk from drying off until 150 d in milk. Cows scored between 3- and 3+ were considered to be in average or good condition. Cows scored less than or equal to 2+ were considered to be underconditioned, whereas those scored greater than or equal to 4- were considered to be overconditioned. Relationships of health and condition score were examined using multiple logistic regression for dichotomous outcomes (e.g., diseased or healthy). Cows that developed dystocia or were culled lost more condition during the dry period than those that did not develop dystocia or were not culled. Cows overconditioned at drying off were more likely to develop cystic ovarian disease and reproductive problems. Cows underconditioned or overconditioned at drying off were more prone to foot problems after calving. Cows overconditioned at 30 d postpartum were more likely to have metritis.
Energy density of weight gain increases with age and weight for age. Gains by more mature cattle contain more fat, less protein, and less water than gains by less mature cattle. The energy density of body tissue reserves mobilized during negative energy balance in early lactation is greater than that in the apparently contributing weight gains. The data reviewed had 140% as much fat and 60% as much protein in mobilized reserves as in gains. These observed differences justified the requantification of the energy density of tissue reserves mobilized for milk synthesis. The energy of gains was estimated by using equations published by the Agricultural Research Council to predict the fat and protein contents of the gains and multiplying them by their respective energy densities. The energy of mobilized reserves (weight losses) were estimated by predicting the fat and protein per kilogram of the contributing gains with the Agricultural Research Council equations, multiplying those fractions by 1.4 and .6, respectively, and multiplying the adjusted fractions by the respective energy densities of fat and protein. There was a close agreement between the predicted and observed energy values of both weight gains and weight losses.
A computer simulation model was developed using theoretical equations to predict DM intake in dairy cattle when the NDF and energy content of the diet and the energy requirements of the animal were known. An adjustment factor for NDF quality was determined to account for differences in intake with legume-based and grass-based diets when formulated at equal NDF content. Mathematical functions were developed from actual data to describe body reserve tissue mobilization and deposition and used to refine the determination of energy requirements and energy balance of the animal. Actual data on milk production and BW changes of Holstein cows under three feeding systems (individual concentrate, one- and two-group total mixed rations) were used to evaluate the model. There was good agreement between observed and predicted production responses, except for the one group total mixed ration, where daily milk yield was overpredicted during early lactation. Further calculations showed that the amount of available CP was too low to support the high milk production that the model predicted in early lactation with the one-group feeding system. This problem was corrected by incorporating a protein restriction on milk production using NRC guidelines.
A 3 x 3 factorial response surface design was used to study the effects of feeding rumen-protected methionine and lysine to dairy cows between 22 and 305 d of lactation. A total of 130 dairy cows at three universities were individually fed a corn silage and corn grain-based diet that contained either soybean meal or corn gluten meal and urea. An unsupplemented control diet plus nine treatment combinations of three amounts of rumen-protected DL-methionine (3.4, 7.8, and 12.2 g/d) and three amounts of rumen-protected L-lysine (5.9, 13.5, and 21.1 g/d) were fed at all locations. Plasma concentrations of methionine and lysine were increased when rumen-protected methionine and lysine were supplemented to the diets. Rumen-protected methionine and lysine did not affect feed intake by cows fed either by soybean meal or corn gluten meal and urea based diets. Milk protein percentage was increased, but milk and milk protein yields were not improved when diets containing soybean meal were supplemented with rumen-protected methionine and lysine. In contrast, milk and milk protein yields were improved when a diet that contained corn gluten meal and urea was supplemented with rumen-protected methionine and lysine. Health and reproduction measurements were similar for cows receiving all treatments.
Eighty primiparous cows were assigned to either soybean meal, fish meal, or A and B treatments. Commercial supplement A was a blend of meat and bone, meat, poultry, blood, and feather meals. Commercial supplement B included the same ingredients as A but had a higher amount of blood meal and also a low concentration of fish meal. In vitro undegradabilities of protein were 32.0, 37.8, 38.8, and 42.4% for soybean meal, fish meal, A, and B rations, respectively. Milk yields and body weight changes were not significantly affected by treatments. Because of the lower milk fat content on fish meal diet, FCM yield was lower for cows fed fish meal than soybean meal or B supplements. Milk protein content was 3.19, 3.19, 3.03, and 3.09% on soybean meal, fish meal, A, and B diets, respectively. The calculated protein efficiency (100* output/input) on soybean meal, fish meal, A, and B diets were 47.8, 51.6, 45.9, and 48.7, respectively. The undegraded protein in the fish meal after an 18-h in vitro incubation with protease enzyme (Streptomyces griseus, type V) had a higher concentration of methionine and lysine than the undegraded protein of other supplements. Flavor of milk produced on the soybean and fish meal diets was evaluated. No flavor differences were detected.
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When mixed ruminal bacteria were incubated with a pancreatic casein hydrolysate and free amino acids of a similar composition, rates of ammonia production were much greater for peptides than for amino acids. The pancreatic digest of casein was then fractionated with 90% isopropyl alcohol. Hydrophobic peptides which dissolved in alcohol contained an abundance of phenolic and aliphatic amino acids, while the hydrophilic peptides which were precipitated by alcohol contained a large proportion of the highly charged amino acids. The Km values of the mixed ruminal bacteria for each fraction were similar (0.88 versus 0.98 g/liter), but the Vmax of the hydrophilic peptides was more than twice that of the hydrophobic peptides (18 versus 39 mg of NH3 per g of bacterial protein per h). Pure cultures of ruminal bacteria had a similar preference for hydrophilic peptides and likewise utilized peptides at a faster rate than free amino acids. Since peptide degradation rates differed greatly, hydrophobicity is likely to influence the composition of amino acids passing unfermented to the lower gut of ruminant animals.
The accuracy of prediction of microbial growth in the rumen and flow of microbial protein to the small intestine is important in predicting protein and carbohydrate utilization in dairy cattle as well as the development of a protein and carbohydrate feeding system that will be an improvement over present systems. Empirical multiple and simple regression equations are presented that demonstrate the impact of body size, proportion of forage in the diet, and dry matter intake on flow of microbial protein into the small intestine from the rumen. Concepts are developed and validated for a mechanistic, dynamic approach for prediction of microbial growth and flow of microbial protein based on Michaelis-Menton equations, microbial substance affinities, and rumen liquid flow kinetics. Emphasis is placed on the importance of quantifying dynamics of rumen function, the need for experimentation to develop a carbohydrate system that will include methods for analysis, and a factorial approach to digestion and utilization.
Eighteen Holstein cows in midlactation were used to study the effectiveness of encapsulated rumen-protected methionine and rumen-protected lysine to deliver methionine and lysine postruminally. The experimental design was a 2 X 2 factorial, a center point, and a control treatment run in a partially balanced, incomplete block design. Treatments were administered over three periods of 3 wk. Cows were fed a blended diet consisting of corn silage, corn, and soybean meal supplemented with five different amounts of rumen-protected methionine and lysine. The amounts of DL-methionine and L-lysine (g/d), respectively, supplied from the encapsulated rumen-protected preparations for the six treatments were 1) 0, 0; 2) 10.40, 18.00; 3) 4.52, 7.82; 4) 16.28, 7.82; 5) 16.28, 28.18; and 6) 4.52, 28.18. In vitro results indicate that amino acids in both of the encapsulated preparations were 94% stable at a pH (5.4), which simulated the rumen, and 94% released at a pH (2.9), which simulated the abomasal environment. A linear increase of plasma methionine and lysine was observed as the amount of methionine and lysine supplied postruminally increased. The concentrations (microgram/ml) of methionine and lysine in plasma for the six treatments were 1) 2.47, 9.05; 2) 3.73, 11.59; 3) 3.60, 11.86; 4) 6.09, 10.45; 5) 5.28, 13.43; and 6) 3.33, 13.27. Rumen-protected lysine increased feed intake, milk yield, and 4% fat-corrected milk production within the surface treatments but had no effect when compared with the unsupplemented control treatment. Rumen-protected methionine and lysine increased production of milk protein. Lysine appeared to improve the utilization of methionine.
Experiments were conducted to ascertain the effect of dietary protein (type and amount) and feeding frequency on peptide concentration and flow from the rumen of lactating Holstein cows. When rations supplemented with soybean meal were fed 12 times/d and CP was 14.5, 17.1, or 20.6%, the estimated flow of N from the rumen was 22, 33, and 34 g/d, respectively. When the soybean meal was autoclaved to decrease protein solubility (14.4, 16.9, and 19.3% CP the flow of peptide N was 19, 26, and 31 g/d, respectively. In both of these experiments rumen volume and dilution rate remained relatively constant throughout the day, and flow was proportional to concentration. If the cows were fed rations containing 17.8% CP once a day, the peptide concentration and dilution rate were highest 2 h after feeding and declined significantly thereafter. Replacement of half the soybean protein with either extruded soybean meal or fish meal decreased the flow of peptide N from the rumen (19 versus 14 and 15 g/d, respectively). Because the total flow of soluble protein and ammonia as well as peptides was less if cows were fed once a day than 12 times per day, increased feeding frequency appeared to increase ruminal proteolysis.
A relatively simple and sensitive procedure was developed to measure the concentration of peptides in rumen fluid. Feed particles and microorganisms were removed by centrifugation, and the supernatant was treated with perchloric acid (5% final concentration). Perchloric acid precipitated macromolecules that included protein, RNA, and DNA. Perchlorate was subsequently removed by precipitation with an excess of potassium carbonate. Ammonia was removed by boiling the alkaline sample. Supernatant samples were then analyzed for ninhydrin reactive material before and after HCl hydrolysis. Because ninhydrin reaction was 3 to 7.5 times greater after HCl hydrolysis, peptides rather than amino acids were the primary source of nonprotein, nonammonia nitrogen. Rumen fluid from a cow fed timothy hay and concentrate supplement (16% crude protein) contained more than 1200 mg peptides/L (192 mg N/L), 1 h after feeding, and this value declined the prefeeding value of 400 mg/L (64 mg N/L) by 8 h after feeding. Comparison of ninhydrin reactivity with and without HCl hydrolysis indicated that peptides present before feeding contained more peptide bonds than the peptides soon after feeding. High pressure liquid chromatography revealed a variety of peaks soon after feeding and fewer dominant peaks 8 h later. The data suggest that peptide uptake into rumen microorganisms can be a rate-limiting step in ruminal protein degradation.
Three lactating Holstein cows, averaging 510 kg and fitted with T-type duodenal cannulae in the proximal duodenum, were in a 3 X 3 Latin-square experiment to measure digestion in forestomachs and whole tract of feed nitrogen and neutral detergent fiber components as influenced by frequency of feeding. Cows were fed one diet containing 65% chopped grass legume hay, 26% cracked corn, and 8% soybean meal. Mixed ration was fed either once daily, four times daily, or the concentrate portion of the diet was fed once daily and the forage portion four times. Ytterbium, as ytterbium chloride, was included with diets to allow calculation of flow rates of duodenal and fecal dry matter. Assayed ratios of nitrogen to diaminopimelic acid in ruminal bacteria and duodenal digesta or fecal bacteria and feces were used to calculate duodenal and fecal bacterial nitrogen flows respectively. Ratios of nitrogen to diaminopimelic acid in ruminal and fecal bacteria averaged 4.15 and 2.38 g/mmol. Apparent digestibility of organic matter in the forestomachs and whole tract averaged 43.7 and 66.4%. Forestomach and whole tract digestibility of cellulose, hemicellulose, and lignin averaged 56.1, 52.0, 14.7, and 58.7, 58.5, and 16.8. Bacterial nitrogen flows averaged 255 and 91 g/day at the duodenum and in the feces. Bacterial nitrogen yield in the rumen averaged 36.6 g/kg organic matter apparently digested in the forestomachs. Frequency of feeding had no effect on almost all measures and components of rumen and whole tract metabolism and digestion. For these intakes, frequency of feeding had little effect on feed intake and nutrient utilization.
Path analysis and logistic regression were used to model direct and indirect relationships among clinical periparturient (within 30 d after calving) retained placenta, metritis, veterinary-assisted dystocia, uncomplicated and complicated ketosis, left displaced abomasum, parturient paresis, mastitis, and estimated nutrient intakes (protein, calcium, phosphorus, energy; coded into terciles) in the last 3 wk of the dry period. Data were from 1,374 multiparous Holstein lactations for calvings from March 1981 through February 1982 in 31 commercial herds in central New York. Periparturient disorders occurred as a complex. Odds ratios for the multiplicative effects of parturient paresis on incidence of veterinary-assisted dystocia, retained placenta, complicated ketosis, and clinical mastitis were 7.2, 4.0, 23.6, and 5.4, respectively. Reproductive disorders were interrelated. Retained placenta, left displaced abomasum, and parturient paresis directly increased risk of complicated ketosis (odds ratios were 16.4, 53.5, and 23.6, respectively). Higher terciles of estimated energy intake in the last 3 wk of the dry period decreased risk of veterinary-assisted dystocia and left displaced abomasum, while higher terciles of estimated protein intake decreased risk of retained placenta and uncomplicated ketosis. Estimated nutrient intakes were directly related to subsequent metabolic disorders and directly and indirectly related (mediated by metabolic disorders) to reproductive disorders. The study suggests that feeding higher intakes (relative to National Research Council recommendations) of protein and energy in the last 3 week of the dry period may reduce the incidence of metabolic and reproductive disorders. Exact recommendations as to the amounts and types of feed cannot be made from our results.