J.G. Fadel

Evaluation of mathematical models to describe neutral detergent residue in terms of its susceptibility to degradation in the rumen

Abstract Disappearance of neutral detergent residue (NDR) from ryegrass hay, brewers dried grains, beet pulp and babassu meal was measured using nylon bags incubated in the rumens of dairy cows eating a ration of 1 3 long hay and 2 3 pelleted concentrate at two levels of feed intake. Ryegrass hay was tested after grinding to pass either a 3- or 1-mm screen while other ingredients were ground to pass a 5-mm screen. Loss of NDR was described by first order, surface, logistic and second order models assuming one degradable fraction of NDR. The first three models were expanded to include a second degradable fraction, while first order and surface models were further expanded by addition of a discrete degradation time-lag. Goodness of model fit was evaluated on the basis of bias and consistency of predicted NDR fraction sizes among cows. Bias was defined as a consistent and repeatable over- or under estimation of residual NDR associated with particular ranges of rumen incubation times. The incubation time required to reduce residual NDR to a minimum varied from less than 3 to more than 30 days among test feeds. None of the models that included only one degradable NDR fraction predicted loss of NDR free of bias. Extent of bias varied among models and ingredients. Compared with the one degradable fraction first order model with a discrete degradation lag, no other one degradable fraction model consistently reduced bias. The second order model was most biased. Bias for ryegrass and beet pulp was moderate, while that for brewers grains and babassu was considered severe. The first order model expanded to include a second degradable NDR fraction predicted loss of NDR free of bias for all ingredients. However, there was only consistency of fraction sizes among cows for brewers grains and babassu. Beet pulp and ryegrass degradable NDR fraction sizes were highly variable. No other model with a second degradable fraction consistently reduced this variation. The simplest model that predicted loss of NDR was the first order model (with lag). However, a model with only one degradable NDR fraction was not adequate for all feeds and a second degradable NDR fraction is supported for some. First order models have the potential to describe NDR in terms of its susceptibility to rumen degradation. However, unaccounted prediction bias and variation in predicted NDR fraction sizes suggest that these models are not biologically correct.

Prediction of enteric methane emissions from cattle

Agriculture has a key role in food production worldwide and it is a major component of the gross domestic product of several countries. Livestock production is essential for the generation of high quality protein foods and the delivery of foods in regions where animal products are the main food source. Environmental impacts of livestock production have been examined for decades, but recently emission of methane from enteric fermentation has been targeted as a substantial greenhouse gas source. The quantification of methane emissions from livestock on a global scale relies on prediction models because measurements require specialized equipment and may be expensive. The predictive ability of current methane emission models remains poor. Moreover, the availability of information on livestock production systems has increased substantially over the years enabling the development of more detailed methane prediction models. In this study, we have developed and evaluated prediction models based on a large database of enteric methane emissions from North American dairy and beef cattle. Most probable models of various complexity levels were identified using a Bayesian model selection procedure and were fitted under a hierarchical setting. Energy intake, dietary fiber and lipid proportions, animal body weight and milk fat proportion were identified as key explanatory variables for predicting emissions. Models here developed substantially outperformed models currently used in national greenhouse gas inventories. Additionally, estimates of repeatability of methane emissions were lower than the ones from the literature and multicollinearity diagnostics suggested that prediction models are stable. In this context, we propose various enteric methane prediction models which require different levels of information availability and can be readily implemented in national greenhouse gas inventories of different complexity levels. The utilization of such models may reduce errors associated with prediction of methane and allow a better examination and representation of policies regulating emissions from cattle.

Digestion kinetics of neutral detergent fiber and chemical composition within some selected by-product feedstuffs

Nine by-product feedstuffs (BPF) obtained from three different sources were evaluated for nutrient composition, estimated nonstructural carbohydrate (NSC) and TDN content, and total extent and rate of digestion of DM and NDF. The nine BPF evaluated included: beet pulp (BP), rice bran (RB), almond hulls (AI-I), citrus pulp (CT), bakery waste (BW), wheat mill run (WMR), brewers’ grains (BG), distillery grains (DG) and soy hulls (SH). Twenty-seven samples were evaluated and were a subset of a larger study reported previously. In sacco techniques were used to measure the amount of NDF and DM remaining in nylon bags after 0, 1, 2, 4, 8, 16, 24, 36, 48, and 72 h of incubation in the rumen of a rumen listulated cow. Chemical analyses measured included ash, crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), and crude protein in the NDF (NDFCP) and ADF (ADFCP) fractions. Chemical composition differed among BPF source. This difference could be due to processing method or ingredients added to BPF during processing. The amount of CP associated with the NDF fraction varied among sources of each BPF. The amount of NDFCP also differed for each BPF. The NDFCP content of CT, O&l%, was low compared with DG, 14.5%, which was high compared with the other BPF evaluated. Correcting for the fiber-bound protein increased the estimate of NSC slightly for most BPF, but the NSC content of DG was increased 88%. The results indicate a correction for NDFCP is necessary for an accurate estimation of NSC in BPF. Within a given BPF, the extent and rate of digestion of NDF were different for each source. The TDN content of each sample was calculated using the rate of in sacco NDF digestion for each BPF at three theoretical rates of passage from

Extent of variability in nutrient composition within selected by-product feedstuffs

Abstract The nutrient composition of nine by-product feedstuffs (BPF) was determined. BPF were selected based on economic importance to the dairy industry, nutritional value, and availability. Three to nine different samples for each BPF were obtained throughout California. A total of 51 samples were collected: nine beet pulp (BP), eight rice bran (RB), seven almond hulls (AH), four citrus pulp (CT), five bakery waste (BW), eight wheat mill run (WMR), four brewers grains (BG), three distillery grains (DG), and three soy hulls (SH) samples. Chemical analyses measured included dry matter, ash, crude protein (CP), fiber fractions, macrominerals, and microminerals. The average chemical analyses determined for each BPF were compared with average values reported by the National Research Council (NRC). Considerable variation within a given BPF was observed in the present study. For example, BP was found to contain 18.81% acid detergent fiber (ADF) while the NRC reported an average composition of 25% ADF. The ether extract content of RB was found to be 20.48% compared with 15.1% reported by NRC. Much of this variability was related to how the commodity was handled during or after processing. In the second part of this study, two theoretical diets were formulated to calculate the effect of nutrient variability on diet composition. The BPF compositions of the two diets were 27% and 50% in Diet 1 and Diet 2, respectively. Specific by-products sources of BP, RB, DG, and SH were compared with the NRC diet composition used in the initial diet formulation. As the proportion of BPF in the diet was increased (Diet 2) nutrient composition of the diet was more variable with CP content ranging from 14.30 to 15.20%. Similar changes to those observed for CP were observed for the other chemical components. The effect of variability in by-product composition was more evident when evaluated on a concentrate mix basis. Variability in the chemical component of BPF influenced the composition of both the total diet and the concentrate mix, and the magnitude of effect depended upon the contribution of BPF to the total ration and the nutrient of interest.

Compositional analyses and rumen degradability of selected tropical feeds

Vadive!oo. 3. and Fade& J.G., 1992. Compositional analysesand nrmendegradabilityofselectedtrop ical feeds. Anim FeedSci. Technol., 37: 265-279. The chemical composition (nitrogen fractions, tibre components, phenolic compsunds, neutral sugars and uranic acids) and rumen degradability of the dry matter (DMD) and neutral detergent tibre (NDFD) of six crop by-products (raw palm oil mill efiluent (POME), dried POME, palm kernel cake, palm press fibre, cocoa pods and rice straw) and the leaves of two legumes (Leucaenti ler~cocep;Wa and Gliricid:n sepiurn) were measured. Univariate and multivariate statistical analyses were used to compare and classify the feeds according to chemical composition and degradability. Lianin ooorlv differentiated between feeds and was ~oorlv related lo 48 h DMD: the maior anomalies wehigb DMD). The xylose:arabinose ratio, an indicator ofbcmicellulose digestion, was higher in the legumes than in the by-products. The ratio of rapidly degradable (arabinose+glucose) to slowly degradable (xylose+uronic acids) sugars was not a good indicator of cell wall digestion; the correlation with 48 h NDF degradability (NDFD) was only 0.69. Cluster analysis showed that conventional classitication of the feeds into by-products and legumes did not reflect their compositional or degradability attributes. These attributes were also poorly related to each other. Two unusual feeds were identified, cocoa pods and palm kernel cake.

Effects of shade and sprinklers on performance, behavior, physiology, and the environment of heifers

The objective was to measure effects of cooling technique (shade vs. water sprinklers) on performance, behavior, physiology, and the environmental effect of 40 Holstein heifers housed in drylot corrals during the hot summer months. The experiment was a replicated crossover design with four 21-d periods and 2 treatments: 1) shades installed in the front half of the pen or 2) sprinklers, which applied water to the pen surface at 2-h intervals from 1100 to 1900 h. Animal performance measures were dry matter intake, average daily gain, and feed efficiency (gain:feed). Behavioral measures, elimination patterns, and corral spatial distribution were measured in 5-min scan frequencies over four 24-h periods. Physiological measures were rectal temperature, respiration rate, urinary urea N, and blood urea N. Environmental measures were corral soil surface temperature and moisture, particulate matter, and surface NH(3) volatilization; meteorological measures were also collected. Shaded compared with sprinkled heifers had increased dry matter intake (3.4%), increased average daily gain (14%), and increased feed efficiency (11%). Heifers in shaded vs. sprinkler treatments had decreased respiration rates (13%). Behavioral differences between the treatments varied by time of day. Heifers spent most time in either the shaded or sprinkled areas of their corrals (65.9 and 64.2%, respectively). Elimination behavior occurred predominantly at the front of the corral in close proximity to the feed bunks and additionally at the water trough in sprinkled corrals. Sprinkler treatment had a 31.7% greater average corral surface moisture than the shaded treatment. Corral surface temperature varied based on areas of surface moisture, shade location, and elimination concentration within the corral. Sprinkled corrals had less particulate matter emissions than shaded (25%), but NH(3) emissions were 46% greater in sprinkler vs. shaded treatment. Overall, the use of shade in heifer corrals improved heifer performance and physiological measures, but sprinkler treatment had less PM [corrected] emissions from corral surfaces under heat stress conditions. Both cooling techniques affected spatial distribution and behaviors of the heifers, which affected pen usage and surface characteristics.

Prediction of ammonia emission from dairy cattle manure based on milk urea nitrogen: relation of milk urea nitrogen to ammonia emissions.

The main objectives of this study were to assess the relationship between ammonia emissions from dairy cattle manure and milk urea N (MUN; mg/dL) and to test whether the relationship was affected by stage of lactation and the dietary crude protein (CP) concentration. Twelve lactating multiparous Holstein cows were randomly selected and blocked into 3 groups of 4 cows intended to represent early [123+/-26 d in milk (DIM)], mid (175+/-3 DIM), and late (221+/-12 DIM) lactation stages. Cows within each stage of lactation were randomly assigned to a treatment sequence within a split-plot Latin square design balanced for carryover effects. Stage of lactation formed the main plots (squares) and dietary CP levels (15, 17, 19, and 21% of diet dry matter) formed the subplots. The experimental periods lasted 7 d, with d 1 to 6 used for adjustment to diets and d 7 used for total collection of feces and urine as well as milk sample collection. The feces and urine from each cow were mixed in the proportions in which they were excreted to make slurry that was used to measure ammonia emissions at 22.5 degrees C over 24 h using flux chambers. Samples of manure slurry were taken before and after ammonia emission measurements. The amount of slurry increased by 22% as dietary CP concentration increased from 15 to 21%, largely because of a greater urine volume (25.3 to 37.1 kg/d). Initial urea N concentration increased linearly with dietary CP from 153.5 to 465.2 mg/dL in manure slurries from cows fed 15 to 21% CP diets. Despite the large initial differences, the final concentration of urea N in manure slurries was less than 10.86 mg/dL for all dietary treatments. The final total ammoniacal N concentration in manure slurries increased linearly from 228.2 to 508.7 mg/dL as dietary CP content increased from 15 to 21%. Ammonia emissions from manure slurries ranged between 57 and 149 g of N/d per cow and increased linearly with dietary CP content, but were unaffected by stage of lactation. Ammonia emission expressed as a proportion of N intake increased with percentage CP in the diet from about 12 to 20%, whereas ammonia emission as a proportion of urinary urea N excretion decreased from 67 to 47%. There was a strong relationship between ammonia emission and MUN [ammonia emission (g/d per cow)=25.0 (+/-6.72)+5.03 (+/-0.373) x MUN (mg/dL); R(2)=0.85], which was not different among lactation stages. Milk urea N concentration is one of several factors that allows prediction of ammonia emissions from dairy cattle manure.

In vitro gas production as a method to compare fermentation characteristics of steam-flaked corn

An in vitro gas production technique was used to determine differences in starch availability that occurred with steam flaking of corn among eight feed mills (MILL) in California. Whole corn (WC) and steam-flaked corn (SFC) grain samples were obtained from six commercial mills and two mills at the University of California (Davis and El Centro, CA). The WC sample was collected prior to the steam chest and represented unprocessed corn. The SFC sample was collected at the rolls and represented a typically processed corn. Ground samples of WC and SFC were evaluated by incubation in buffered rumen fluid using an in vitro gas technique for a 72 h incubation period to compare processing (PROCESS) method. Starch reactivity was determined as the percentage of starch degraded to glucose by amylase after 4 h of incubation. Starch reactivity of SFC was higher (P<0.01) than WC. Starch reactivity was different for MILL (P<0.01) and the interaction of MILL and PROCESS was significant (P<0.01). Total gas produced at 8 h of incubation was higher (P<0.01) for SFC than WC, but total gas production did not differ for PROCESS at 24 and 72 h. Gas production after 8 h also differed for MILL (P<0.01). Time required for 25, 50, 75, and 90% disappearance of starch was estimated and in general disappearance of starch occurred sooner for SFC than WC. Fifty percent disappearance of starch occurred at 6.8 h for WC and at 5.5 h for SFC. Total volatile fatty acids (VFA) production did not differ for MILL or PROCESS at 8 or 72 h of incubation. Propionate production was higher (P<0.01) for SFC than WC at both 8 and 72 h. This in vitro gas production technique can be used to determine the effect of grain processing on fermentation rate and to identify differences among mills in potential digestibility of the processed grain.

A linear programming model to optimize diets in environmental policy scenarios.

The objective was to develop a linear programming model to formulate diets for dairy cattle when environmental policies are present and to examine effects of these policies on diet formulation and dairy cattle nitrogen and mineral excretions as well as methane emissions. The model was developed as a minimum cost diet model. Two types of environmental policies were examined: a tax and a constraint on methane emissions. A tax was incorporated to simulate a greenhouse gas emissions tax policy, and prices of carbon credits in the current carbon markets were attributed to the methane production variable. Three independent runs were made, using carbon dioxide equivalent prices of

The interactive effects of selenomethionine and methylmercury on their absorption, disposition, and elimination in juvenile white sturgeon

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