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Our objective was to develop an age × BCS factor (ABCf) that could be used to estimate the ADG of stockers grazing bermudagrass (Cynodon dactylon[L.] Pers.) pasture as influenced by their age and BCS at the onset of stocking, hereafter referred to as the initial age and BCS.

Our objective was to develop an herbage allowance (HA) and nutritive value (NV)-based pasture factor (PF) that could be used to estimate the daily herb- age intake (HI) of stockers grazing bermudagrass [Cyn-odon dactylon(L.) Pers.] pasture as constrained by herb-age mass.

The objective of this study was to determine the influence of varying levels of dried distillers grains with solubles (DDGS) supplemented daily on the performance of beef stocker cattle grazing Coastal bermudagrass [Cynodon dactylon(L.) Pers.] pastures.

Our objective was to develop models to estimate the CP, NDF, lignin, and ash concentrations of bermudagrass [Cynodondactylon(L.) Pers.] forage daily throughout the grazing season and use them to estimate TDN daily. We hypothesized that the CP, NDF, lignin, ash, and TDN concentrations might change daily.

The objective of this experiment was to measure feedlot performance, rumination, ruminal pH, and carcass characteristics of cattle consuming a finishing diet with increasing levels of corn stalks (CS).

The objective of this study was to determine the influence of varying rates of dried distillers grains with solubles (DDGS) supplemented daily on performance of beef stocker cattle grazing Tifton 85 (Cynodon dactylon[L.] Pers. × Cynodon nlemfuënsisVanderyst) bermudagrass pastures.

Two studies were conducted to evaluate the effects of sorghum wet distillers grains (SWDGS) in finishing diets on steer performance, carcass characteristics, and nutrient digestibility. In Exp. 1, 240 steers (initial BW = 379 ± 1 kg) were fed steam-flaked corn–based diets with or without 25% SWDGS and 7.5, 10.0, or 12.5% alfalfa hay. There were no effects of alfalfa hay concentration on BW, DMI, ADG, or G:F (P≥ 0.16). Including SWDGS reduced (P≤ 0.05) ADG and G:F. Fat thickness decreased (P= 0.03) and DP tended to decrease (P= 0.09) linearly as level of alfalfa hay increased. Final BW of steers consuming diets containing 25% SWDGS were 12 kg lighter (P= 0.05) than those of steers fed diets without SWDGS. Hot carcass weight tended (P= 0.09) to be lighter for steers fed SWDGS. In Exp. 2, effects of corn processing method (steam-flaked corn and dry-rolled corn) and 20% corn wet distillers grains with solubles (CWDGS) or SWDGS inclusion on ruminal pH and in situ digestibility were evaluated. Cattle consuming diets containing SWDGS had a greater (P≤ 0.05) ruminal pH than steers consuming diets with CWDGS or no wet distillers grains with solubles. Including wet distillers grains with solubles did not affect (P≥ 0.37) steam-flaked corn or dry-rolled corn in situ DM digestibility. In situ digestibility of DM and NDF differed between CWDGS and SWDGS (P< 0.0001). Differences in performance and nutrient digestibility between CWDGS and SWDGS are the result of differences in the product rather than an interaction with corn processing method.

Efficiency of animal production is an important component of the beef industry. The research objectives of this 2-yr study were to (1) estimate residual feed intake (RFI) of yearling Brahman (Bos indicus) bulls grazing Coastal bermudagrass [Cynodon dactylon(L.) Pers.] using DMI measured with n-alkanes; (2) compare RFI under grazing (RFIg) with RFI determined in confinement under restricted feed intake at 2.8% of BW (RRFIc); and (3) assess the relationships of carcass traits and gastrointestinal tract anatomy to RFIg. Bulls RRFIc-phenotyped as efficient (n-RFI) and inefficient (p-RFI) in both 2009 and 2010 were assigned to 2 replicate pastures at either low or high stocking intensity (STK) for 60 d. In 2009 there was no difference (P> 0.3) between n-RRFIc and p-RRFIc for initial or final BW, ADG, DMI, or feed-to-gain ratio. There was an interaction of RFIg × STK (P= 0.043) for ADG in which p-RFIg bulls on low STK had the greatest gain. The p-RFIg bulls had the greatest DMI regardless of STK (P< 0.01). In 2009 differences were found for carcass traits and gastrointestinal tract, and p-RFIg bulls on low STK had the greatest DMI and heaviest gastrointestinal tract. In 2010 p-RRFIc bulls had the heaviest initial BW (P= 0.048), final BW (P= 0.084), and metabolic BW (P= 0.054), and the greatest DMI (P< 0.01). From confinement to pasture, 37.5% of bulls on pasture maintained the same RRFIc rank in 2009, and 56.3% of bulls on pasture remained in the same RRFIc rank in 2010.

Two experiments were conducted to examine the impact of source, urea (U) or Optigen II (OP), and level of dietary NPN on performance (Exp.1) and N balance (Exp. 2) of growing cattle. Sixty Angus crossbred steers (initial BW = 353 ± 13.9 kg) were used to evaluate performance, and fed 1 of 3 steam-flaked corn based diets: U (U1.2, 1.2% NPN), OP (OP1.3, 1.3% NPN), or OP without cottonseed meal (OP3.1, 3.1% NPN). U1.2and OP1.3contained cottonseed meal and NPN as CP sources, whereas OP3.1contained only NPN. For Exp. 1, steers were blocked by postweaning BW and assigned to treatment (TRT) and pen within block. Body weight was collected every 14 d during the 105-d trial. Six steers from each TRT were selected based on residual feed intake (RFI) and harvested. Carcass and organ measurements were obtained. Cumulative animal performance was evaluated in 3 periods (0 to 35, 0 to 70, and 0 to 105 d) using a mixed coefficient model with initial BW as a covariate. For Exp. 2, 5 ruminally cannulated Holstein steers in a 5 × 5 Latin square design were used to evaluate N balance. Steers were fed a steam-flaked corn based diet with either no NPN, 0.75% U or N equivalent OP, or 1.5% U or N equivalent OP. Intake was measured, and feed, orts, urine, and fecal samples were obtained and composited for each steer by period. Data were analyzed using a mixed coefficient model. Orthogonal contrasts were used to evaluate differences between OP and U, and high and low level of NPN. For Exp. 1, there were no differences (P> 0.10) in initial BW, final BW, ADG, or DMI among TRT for any of the periods. However, for period 1 steers on OP3.1had reduced F:G than U1.2(5.71kg/kg vs. 7.39kg/kg; P= 0.03), and steers fed OP1.3tended to have less F:G than those fed U1.2(6.07 kg/kg vs. 7.39kg/kg; P= 0.07). In period 2, OP3.1had reduced F:G than U1.2(5.58 kg/kg vs. 6.56kg/kg; P= 0.03), but did not differ from OP1.3(5.97). For Exp. 2, steers fed OP tended (P= 0.09) to have less apparent N absorption than those fed U. Apparent N absorption differed (P< 0.05) for level of NPN. There were no differences (P> 0.10) in intake or digestibility among source or level of NPN. No major differences (P> 0.10) on performance and carcass composition were observed between U and OP diets. Steers had better initial F:G (Period 1 and 2) when OP was used as the only source of feed N (OP3.1), suggesting that OP may replace true protein feeds in finishing cattle diets, minimizing feed use with no impact on carcass quality.

Twenty-four multiparous and fifteen first lactation Holstein cows averaging 263 days in milk and weighing 614kg were fed diets adequate or deficient in ruminal nitrogen (N), based on predictions of the Cornell Net Carbohydrate and Protein System (CNCPS). After adjustment to a low crude protein (CP) total mixed rations (TMR; 12.6% CP), the cows were allocated to 13 blocks based on lactation number, milk production, body condition score, and body weight. Within each block, cows were randomly assigned to one of the 3 treatment (TRT) diets (9.4, 11.1 and 14.1% CP for TRT 1, 2, and 3, respectively). All diets contained the same proportion of high moisture corn, chopped grass hay, and minerals, with urea substituted for corn silage as needed to reach the three CP levels. The TRT diets were then fed to the cows for 4 wk. Milk production was significantly affected by TRT: 15.5, 18.8, and 21.7 kg/d for TRT diets 1, 2, and 3, respectively. DMI was increased significantly as the percentage of CP increased from 9.4 to 14.1% CP: 17.6, 20.0, and 21.2 kg/d for TRT diets 1, 2, and 3, respectively. CNCPS predictions for production (with and without the N adjustment for ruminal N deficiency) of metabolizable protein (MP) allowable milk were compared with observed milk production. Using the average individual weekly cow data from all 3 TRT, we found that the CNCPS accounted for 72 and 68% of the variation in MP allowable milk without and with the N deficiency adjustment, respectively. The overall mean bias without the N adjustment was 3.3kg of milk (over prediction model bias of 14.6%, P<0.001), and the N adjustment reduced the model over-prediction bias to 0.01kg of milk (P= 0.96).

The objective of this study was to determine the effect of oral doses of ruminal fluid (RF) on the growth and health of newborn, milk-fed heifer dairy calves (0 to 6 wk of age). Calves given 8ml of RF each day until weaning gained more weight and had fewer scours than controls that did not receive RF. Because RF that was exposed to oxygen or was autoclaved also gave a response, it is unlikely that the preparations were acting as a probiotic. When the RF was centrifuged to separate the cells (RFC) from the fluid (RFS), both fractions had similar activity, and this result indicated that the response was not nutritional; that is, 1) RFC supplied a small amount of protein (approximately 8 mg/d), but RFS had much less protein, and 2) RFS had volatile fatty acid, but RFC had little if any volatile fatty acid. However, both RFS and RFC had bacterial polysaccharide, and bacterial polysaccharide has strong antigenic properties. In the first three studies, treated calves were given RF preparations each day until weaning (6 wk), but a subsequent experiment indicated that calves given autoclaved RF for only 5 d (d 1 to 5) also had greater body weight gains during the first 2 wk of life and fewer scours than untreated controls. Given that the dosage of RF was small and the material could be autoclaved to prevent disease transmission, RF supplementation could be a practical tool for improving calf health.

We conducted a lactation trial with a fresh forage diet in order to evaluate 1) the effects of monensin on nitrogen metabolism, and 2) the Cornell Net Carbohydrate and Protein System (CNCPS). Thirty Holstein cows in midlactation (eight fitted with ruminal fistulas) were gradually introduced to a fresh forage diet. A concentrate mix based on corn meal was fed before the a.m. and p.m. milking times 0730 and 1730h, then the fresh forage was fed at 0830 and 1830h. Fifteen cows each were allocated to a control (no monensin) and a treatment group receiving 350 mg/cow per day of monensin in the p.m. concentrate feeding. A 7-d fecal and urine collection period and a 3-d rumen sampling period were conducted with the fistulated cows. After the lactation study was concluded, the fistulated cows were fed forage regrowth and a 3-d rumen sampling period was repeated. Monensin increased milk production by 1.85kg. Milk fat and protein concentrations decreased and milk fat and protein yields increased, but the effects were nonsignificant. Monensin did not significantly affect DMI. Ruminal ammonia and the acetate-to-propionate ratio decreased with the addition of monensin in both fed forages. Monensin decreased fecal N output, and increased apparent N digestibility by 5.4%. Because of the decrease in ruminal ammonia and increase in apparent N digestibility, we concluded monensin was sparing amino acids from wasteful rumen degradation with a fresh forage diet. The precision of the CNCPS in predicting performance was high (r2= 0.76), and the bias was low (overprediction of 3.6%). These results indicate that the CNCPS can be used for dairy cows consuming fresh forage and gives realistic predictions of performance.

We developed a diet optimizer for least-cost diet formulation with the Cornell Net Carbohydrate and Protein System (CNCPS) using linear programming. The CNCPS model is intrinsically nonlinear, and feed biological values vary with animal and feed characteristics. To allow linear diet optimization, we first used the CNCPS model to generate biological values to characterize the energy and protein content of each feed for the specific group for which the diet was being formulated. The biological values used were metabolizable energy (Mcal/kg), metabolizable protein [(% dry matter (DM)], passage rate (%/h), bacteria yield efficiencies (g/g), and degradation rate of the carbohydrate B2 fraction (%/h). In addition, the ruminal balances for nitrogen and peptides were included in the optimizer to optimize ruminal degradation of fiber. The objective function was to minimize diet cost subject to animal requirement and feed availability constraints. The animal constraints were set by requirements for DM intake (kg/d), metabolizable energy (Mcal/kg), metabolizable protein (%DM), and effective neutral detergent fiber (%DM) for a given level of production. Data from a dairy farm were used to evaluate this linear diet optimizer. Across all classes of dairy cattle, the CNCPS 4.0 model typically obtained a solution in less than six iterations that met the requirements with nearly 100% accuracy. We conclude this linear optimizer can be used to accurately formulate least-cost diets with the CNCPS model.

The objective of this paper was to develop a linear optimization procedure for allocating homegrown feeds across the herd to optimize use of their nutrients in whole farm nutrient management planning. The first step involved developing an optimal diet for each group by a linear programming (LP) procedure developed for the Cornell Net Carbohydrate and Protein System (CNCPS). Information (feed biological values, nutrient requirements, animal and environmental factors, nutrient excretion, and the optimal diet) for each group was exported to a whole farm worksheet, where another LP procedure was used to optimize the allocation of homegrown crops by satisfying the set requirements of each animal group while optimizing return over feed costs and nutrient excretion constraints.

The objectives of this paper were to use a linear programming model previously described to evaluate different alternatives for reducing excess nutrients that may influence water quality on a case study farm (300 lactating cows on 430ha of cropland growing alfalfa, grass, and corn). Several alternatives perceived to influence farm nutrient balance were evaluated for their potential to reduce N and P mass balance. Dividing lactating cow diets into three groups according to their level of milk production versus a one-group total mixed ration decreased mass balance (tonne/yr) from 51.7 to 44.7 for N, from 6.7 to 6.1 for P and from 16.2 to 14.8 for K with little influence on return over feed costs. Increasing forage quality (lower neutral detergent fiber and higher crude protein) did not improve N balance because of the increased N fixation from the air to the soil, but it increased returns over feed costs by $31,385. Improving yields to the maximum potential for the farm reduced mass balance by 29, 51, and 100% for N, P, and K, respectively, and increased returns over feed costs by $70,579. Changing the crop hectare proportions to more corn and less alfalfa reduced N and K balances by 19 and 29%, respectively, and increased returns over feed costs $39,383. Increasing annual milk production 10% by increasing milk production per head 10% compared with increasing animal numbers at the current average milk production per cow until total milk increased 10% gave $34,132 more return over feed costs with less N, P, and K retained on the farm.