Milk production and efficiency of utilization of nitrogen, metabolizable protein, and amino acids are affected by protein and energy supplies in dairy cows fed alfalfa-based diets.

Alfalfa has a lower fiber digestibility and a greater concentration of degradable protein than grasses. Dairy cows could benefit from an increased digestibility of alfalfa fibers, or from a better match between nitrogen and energy supplies in the rumen. Alfalfa cultivars with improved fiber digestibility represent an opportunity to increase milk production, but no independent studies have tested these cultivars under the agroclimatic conditions of Canada. Moreover, decreasing metabolizable protein (MP) supply could increase N use efficiency while decreasing environmental impact, but it is often associated with a decrease in milk protein yield, possibly caused by a reduced supply of essential AA. This study evaluated the performance of dairy cows fed diets based on a regular or a reduced-lignin alfalfa cultivar and measured the effect of energy levels at low MP supply when digestible His (dHis), Lys (dLys), and Met (dMet) requirements were met. Eight Holstein cows were used in a double 4 × 4 Latin square design, each square representing an alfalfa cultivar. Within each square, 4 diets were tested: the control diet was formulated for an adequate supply of MP and energy (AMP_AE), whereas the 3 other diets were formulated to be deficient in MP (DMP; formulated to meet 90% of the MP requirement) with deficient (94% of requirement: DMP_DE), adequate (99% of requirement: DMP_AE), or excess energy supply (104% of requirement; DMP_EE). Alfalfa cultivars had no significant effect on all measured parameters. As compared with cows receiving AMP_AE, the dry matter intake of cows fed DMP_AE and DMP_EE was not significantly different but decreased for cows fed DMP_DE. The AMP_AE diet provided 103% of MP and 108% of NEL requirements whereas DMP_DE, DMP_AE, and DMP_EE diets provided 84, 87, and 87% of MP and 94, 101, and 107% of NEL requirements, respectively. In contrast to design, feeding DMP_EE resulted in a similar energy supply compared with AMP_AE, although MP supply has been effectively reduced. This resulted in a maintained milk and milk component yields and improved the efficiency of utilization of N, MP, and essential AA. The DMP diets decreased total N excretion, whereas DMP_AE and DMP_EE diets also decreased milk urea-N concentration. Reducing MP supply without negative effects on dairy cow performance is possible when energy, dHis, dLys, and dMet requirements are met. This could reduce N excretion and decrease the environmental impact of milk production.

Economic and environmental effects of revised metabolizable protein and amino acid recommendations on Canadian dairy farms.

The objective of this research was to evaluate the potential economic and environmental effects of the formulation model used to balance dairy rations for metabolizable protein (MP) or 3 essential AA (EAA: His, Lys, and Met) in 3 regions of Canada with different farming systems. The Maritimes, Central Canada, and the Prairies reference dairy farms averaged 63, 71, 144 mature cows per herd and 135, 95, 255 ha of land, respectively. Using N-CyCLES, a whole-farm linear program model, dairy rations were balanced for (1) MP, based on National Research Council (NRC) requirements (MP_2001); (2) MP plus Lys and Met, based on NRC (AA_2001); (3) MP (MP_Rev); or (4) for His, Lys, and Met (AA_Rev), both based on a revised factorial approach revisiting both supply and requirements of MP and EAA. Energy was balanced to meet requirements based on NRC (2001). Assuming the requirements were met within each approach, it was considered that milk yield and composition were not affected by the type of formulation. Given the assumptions of the study, when compared with MP_2001 formulation, balancing dairy rations using the AA_Rev approach reduced calculated farm N balance by 3.8%, on average from 12.71 to 12.24 g/kg of fat- and protein-corrected milk; it also enhanced farm net income by 4.5%, from 19.00 to 19.70 $CAN/100 kg of fat- and protein-corrected milk, by reducing inclusion of protein concentrate in dairy rations. Calculated animal N efficiency was on average 4.3% higher with AA_Rev than with MP_2001 for mid-lactation cows. This gain in N efficiency would result in a reduction in N2O emission by manure, contributing to a partial decrease of total greenhouse gas emission by 1.7%, through a reduction of N excreted in manure. With the AA_2001 formulation, farm N balance was 1% higher than with MP_2001 formulation while reducing farm net income by 6.4%, due to the need to purchase rumen-protected AA, with no effect on total greenhouse gas emission. Both MP formulations lead to fairly similar outputs. The AA_Rev formulation also indicated that His might be a co-limiting AA with Met in dairy rations balanced with ingredients usually included in Canadian dairy rations. Given the assumptions of the study, balancing dairy rations for 3 EAA (His, Lys, and Met) rather than MP, has some potential positive effects on Canadian dairy farms by increasing net incomes through a reduction of crude protein supply, leading to a decreased environmental effect.

Tall fescue as an alternative to timothy fed with or without alfalfa to dairy cows.

Tall fescue might be an alternative to timothy in northeastern North America because of its tolerance of recurring drought periods and its good summer regrowth, but is not always considered as an option in dairy rations because of its possible lack of palatability. The objective of this study was to evaluate the effects on the performance of lactating dairy cows of (1) replacing timothy silage by tall fescue silage, offered as sole forage in the diet or in combination with alfalfa silage, and (2) feeding tall fescue as silage (35% dry matter, DM) or haylage (55% DM). Experimental diets with a forage-to-concentrate ratio of 70:30 were (1) 100% timothy silage (TS); (2) 100% tall fescue silage (TFS); (3) 55:45 timothy:alfalfa silages (TS + AS); (4) 55:45 tall fescue:alfalfa silages (TFS + AS); and (5) 100% tall fescue haylage (TFH). Fifteen Holstein cows in mid-lactation (5 fitted with a rumen fistula) were randomly assigned to treatments in a triple 5 × 5 Latin square design with treatment periods of 21 d. Preplanned contrasts were timothy versus tall fescue silages, sole grass species versus grass-alfalfa, interaction between sole grass species and grass-alfalfa, and TFS versus TFH. Grass species did not affect dry matter intake (DMI) or milk yield and fat concentration. Milk protein concentration was not affected by grass species when offered in combination with alfalfa, but it was higher with the TS diet than the TFS diet when offered as sole forages. Adding alfalfa to either tall fescue or timothy silage resulted in greater DMI and milk yield, but lower milk fat concentration, than when the grass silages were the sole forage in the diet. The molar proportion of propionate in the rumen was greater when cows were fed diets with tall fescue silage compared with timothy silage, which resulted in a lower acetate-to-propionate ratio. Milk fat concentrations of fatty acids from microbial origin, namely branched-chain fatty acids, were greater when grass silage, and especially timothy silage, were fed as sole forages rather than with alfalfa silage. Feeding TFH rather than TFS caused a decrease in DMI and tended to lower milk protein concentration, but did not affect milk yield. A more fibrolytic fermentation profile was observed in rumen of cows fed TFH compared with TFS, as indicated by the increase in the molar proportion of acetate and the higher acetate-to-propionate ratio in rumen fluid, and a concomitant increase in branched-chain fatty acid concentration in milk fat. Tall fescue as silage or haylage is a valuable alternative to timothy silage for lactating dairy cows.

The relationship between the number of consecutive days with heat stress and milk production of Holstein dairy cows raised in a humid continental climate.

Heat stress is known to affect performance of dairy cows experiencing prolonged periods of high temperature and relative humidity. Less is known about its effects in cooler climates. The goals of the present study were to determine the prevalence of days susceptible to cause mild heat stress in dairy cows living in a humid continental climate and to investigate the relationship between the number of consecutive days of mild heat stress and milk, fat, protein, and lactose production. A 6-yr data set (2010-2015) containing 606,031 milk analysis records for 34,360 Holstein dairy cows at different parities was matched with the corresponding daily maximum temperature-humidity index. Exposure to heat stress conditions was divided into 5 categories corresponding to 0, 1 to 2, 3 to 4, 5 to 6, and 7 to 8 consecutive days before milk test date. On average, cows were exposed to heat stress conditions for 135.8 ± 5.9 d/yr in Southwest Quebec and 95.3 ± 10.2 d/yr in Eastern Quebec. Cows experiencing heat stress conditions produced on average less fat, protein, and energy-corrected milk and lower fat and protein concentrations. The decrease in milk fat reached 6% for category 7 to 8 exposure of cows in parity 3 or more. The association between exposure category and milk yield and lactose yield and concentration was weak. Heat stress lowered milk fat and protein production but had little effect on milk volume output. Further research is necessary to better understand the mechanism underlying the effects of sporadic low- to medium-intensity heat stress on dairy productivity.

Short communication: Summer on-farm environmental condition assessments in Québec tiestall farms and adaptation of temperature-humidity index calculated with local meteorological data.

Temperature-humidity index (THI) calculation following the equation developed by the National Research Council (A Guide to Environmental Research on Animals, 1971) requires ambient temperature (AT) and relative humidity (RH). Those data are widely and readily available at local meteorological stations. However, studies showed that using average AT and RH retrieved from the closest stations is not appropriate for estimating on-farm conditions. The present objectives were (1) to study summer on-farm environmental conditions, (2) to explore the relationship between summer THI calculated with on-farm data and summer THI calculated with local weather station data, and (3) to verify whether THI calculated with summer meteorological station data could be adapted to better represent summer on-farm conditions. Six tiestall dairy farms located in 2 regions of the province of Québec [Eastern Québec (EQ) and Southwestern Québec (SWQ)] were enrolled in this study. Within-barn conditions were monitored using 3 remote data loggers from August 2016 through August 2017. Two loggers were installed inside at varying distances relative to the ventilation inlet (L1: closest to inlet; L2: farthest from inlet) and a third was installed just outside of the barn (L3). Values retrieved from each logger and the closest local meteorological station were used to calculate daily THI according to the National Research Council formula and were ultimately compared. Our results showed that THI varied within the barn depending on the proximity relative to the inlet because THI measured by L1 was lower than THI measured by L2 in both regions. Moreover, our results showed that in both regions AT measured on-farm was consistently higher than AT measured at the weather station. The opposite was observed with RH, as it was significantly lower on-farm in EQ and numerically lower in SWQ compared with RH extracted from weather stations. Overall, this led to THI being lower by 4.6 and 3.7 units at the weather stations compared with within-barn conditions for EQ and SWQ farms, respectively. Hence, using local meteorological station data to estimate on-farm conditions would lead to an underestimation of heat stress level in dairy cows. Adapting THI calculations by including daily maximum AT and minimum RH retrieved from the local weather station instead of their average counterparts led to a better estimation of within-barn conditions. However, the difference between THI measured on-farm and the adapted THI calculated with weather station data remained significant. Although the adaption made to THI allowed for a closer relation to on-farm conditions, THI calculated with weather station data should only be used to assess heat stress level in dairy cows when heat stress thresholds are adapted for such data.

Prediction of the amino acid digestibility of legume seeds in growing pigs: a meta-analysis approach.

On pig farms, a high proportion of the cost of production comes from feed costs. However, the use of alternative ingredients such as legume seeds may help to reduce this cost. In fact, legume seeds are an important source of essential amino acids (EAA) and can therefore be an alternative to oilseed meals. However, the accurate use of these legume seeds requires a precise knowledge of the standardized ileal digestibility (SID) of EAA, which may vary depending on its botanical variety. A meta-analysis was performed on a database compiling data from 41 studies published between 1981 and 2013 and 178 dietary treatments. Models of prediction of the SID of EAA as well as the dietary concentration of digestible standardized EAA (dEAA) were obtained, based on the chemical composition of ingredients reported in the publications. The effect of the type of legume seeds (faba bean, lupin, pea and soya bean), surgical procedures (T-cannula, re-entrant cannulas, post valve T-cannulas and ileo-rectal anastomosis), and BW of pigs (BW⩽25 kg BW>25 kg) were also tested in each model. Results showed that dietary CP and crude fibre (CF) were, respectively, the best predictors of each EAA SID for faba bean, lupin and pea (R 2=0.42 to 0.89) and soya bean (R 2=0.32 to 0.77). For the dEAA content, the best prediction models included dietary CP and ADF for faba bean, lupin and pea and soya bean, respectively, with R 2 ranging from 0.66 to 0.98. Models developed in this study allow predicting the digestibility of EAA in these alternatives feedstuffs.

Interaction of potassium carbonate and soybean oil supplementation on performance of early-lactation dairy cows fed a high-concentrate diet.

Potassium carbonate supplementation is known to improve milk fat synthesis and to modify milk mineral composition in dairy cows. The objective of the current experiment was to evaluate the effect of K2CO3 on production performance, biohydrogenation of fatty acids (FA), and mineral composition of milk in early-lactation dairy cows fed a high-concentrate diet with or without soybean oil (SBO), as a source of polyunsaturated FA. Twenty-eight ruminally fistulated Holstein cows were used in a randomized complete block design. The experiment lasted 33 d, including a 5-d pretreatment collection period used as a covariate. Experimental treatments were arranged as a 2 × 2 factorial with 0 or 1.5% K2CO3 and with 0 or 2% SBO, and balanced to contain 40% forage (57% corn silage + 43% grass silage) and 60% concentrate. Preplanned orthogonal contrasts were used to assess the effects of K2CO3, SBO, and their interaction. Feeding K2CO3 did not affect milk yield, but tended to increase 4% fat-corrected milk and fat yield when combined with SBO. However, adding SBO to diets increased milk yield. Dietary K2CO3 supplementation did not affect milk fat concentration of trans-10 18:1 or any other identified biohydrogenation intermediates. Soybean oil supplementation decreased milk fat concentration of C16 and de novo synthesized FA, and increased preformed FA. Among the other effects of SBO supplementation observed, concentrations of cis-9,trans-11 18:2 increased, as well as most of the cis and trans isomers of 18:1 and 18:0. Milk urea N decreased in cows fed K2CO3 as compared with unsupplemented diets. A positive relation was established between milk Cl concentration and milk yield, suggesting that the equilibrium of this ion is linked to the efficiency of lactogenesis. The effect of K2CO3 on this mineral equilibrium in the mammary gland remains to be established. Overall, results have shown that potential effect of K2CO3 on milk fat synthesis is dependent on the levels of dietary polyunsaturated FA.

Economic effect of reducing nitrogen and phosphorus mass balance on Wisconsin and Québec dairy farms.

Our objective was to explore the trade-offs between economic performance (farm net income, FNI) and environmental outcomes (whole-farm P and N balances) of dairy farms in Wisconsin (WI; United States) and Québec (QC; Canada). An Excel-based linear program model (N-CyCLES; nutrient cycling: crops, livestock, environment, and soil) was developed to optimize feeding, cropping, and manure management as a single unit of management. In addition to FNI, P and N balances model outputs included (1) the mix of up to 9 home-grown and 17 purchased feeds for up to 5 animal groups, (2) the mix of up to 5 crop rotations in up to 5 land units and c) the mix of up to 7 fertilizers (solid and liquid manure and 5 commercial fertilizers) to allocate in each land unit. The model was parameterized with NRC nutritional guidelines and regional nutrient management planning rules. Simulations were conducted on a typical WI farm of 107 cows and 151 ha of cropland and, a Southern QC farm of 87 cows and 142 ha of cropland and all results were expressed per kg of fat- and protein-corrected milk (FPCM). In absence of constraints on P and N balances, maximum FNI was 0.12 and 0.11 $/kg of FPCM for WI and QC, respectively, with P and N balances of 1.05 and 14.29 g/kg of FPCM in WI but 0.60 and 15.70 g/kg of FPCM in QC. The achievable reduction (balance at maximum FNI minus balance when the simulation objective was to minimize P or N balance) was 0.31 and 0.54 g of P/kg of FPCM (29 and 89% reduction), but 2.37 and 3.31 g of N/kg of FPCM (17 and 24% reduction) in WI and QC, respectively. Among other factors, differences in animal unit per hectare and reliance on biological N fixation may have contributed to lower achievable reductions of whole-farm balances in WI compared with QC. Subsequent simulations to maximize FNI under increasing constraints on nutrient balances revealed that it was possible to reduce P balance, N balance, and both together by up to 33% without a substantial effect on FNI. Partial reduction in P balance reduced N balance (synergetic effect) in WI, but increased N balance (antagonistic effect) in QC. In contrast, reducing N balance increased P balance in both regions, albeit in different magnitudes. The regional comparison highlighted the importance of site-specific conditions on modeling outcomes. This study demonstrated that even when recommended guidelines are followed for herd nutrition and crop fertilization, the optimization of herd feeding, cropping, and manure spreading as a single unit of management may help identify management options that preserve FNI, while substantially reducing whole-farm nutrient balance.

Nitrogen efficiency of eastern Canadian dairy herds: Effect on production performance and farm profitability.

Nitrogen efficiency (milk N/dietary N; NE) can be used as a tool for the nutritional, economic, and environmental management of dairy farms. The aim of this study was to identify the characteristics of herds with varying NE and assess the effect on farm profitability. One hundred dairy herds located in Québec, Canada, comprising on average 42 ± 18 cows in lactation were visited from October 2014 to June 2015. Feed intake was measured over 24 h. Samples of each feedstuff were taken and sent to a commercial laboratory for analysis of chemical composition. Feeding management and feed prices were recorded. Milk yield was recorded and milk samples were collected over 2 consecutive milkings. Fat, protein, and milk urea N were analyzed. Balances of metabolizable protein (MP; MP supply - MP requirements) and rumen degradable protein (RDP; RDP supply - RDP requirement) were calculated. A hierarchical cluster analysis was conducted and allowed grouping the farms by their NE. Four clusters were identified with an average NE of 22.1 (NE22), 26.9 (NE27), 30.0 (NE30), and 35.8% (NE36). Herds in clusters NE30 and NE36 were fed diets with greater concentrations of starch, net energy for lactation, and nonfiber carbohydrates than those in the other 2 clusters. Moreover, the average proportion of corn silage was lower for herds in cluster NE22 compared with NE30 and NE36 (8.23 vs. 31.8 and 31.3% of total forages, respectively). In addition, crude protein of the diets declined from an average of 16.0 to 14.9% with increasing NE among clusters. Average dry matter intake declined from 26.1 to 22.5 kg/d as NE of clusters increased. Herds in cluster NE22 had lower yields of milk (28.7 vs. 31.8 kg/d), fat (1.15 vs. 1.29 kg/d), and protein (0.94 vs. 1.05 kg/d) than the other clusters. Also, milk urea N was greater for farms in cluster NE22 (13.2 mg/dL) than for farms in the other clusters (11.4 mg/dL). Furthermore, MP and RDP balances decreased from 263.2 to -153.7 g/d and from 594.7 to 486.9 g/d, respectively, with increasing NE among clusters. Income over feed cost increased from $14.3 to $17.3/cow per day (Can$) as NE among clusters augmented. Results from this study showed that some farms were able to achieve high NE by using lower levels of dietary N and having cows with lower DMI while maintaining milk performance. These farms had a potentially lower environmental impact, and they were more profitable.

Potassium carbonate as a cation source for early-lactation dairy cows fed high-concentrate diets.

Previous studies reported that addition of K2CO3 to high-concentrate diets improved milk fat synthesis, although the mechanism is yet to be established. The objective of the current experiment was to investigate the effects of dietary cation-anion difference (DCAD), cation source, and buffering ability of the mineral supplement on rumen biohydrogenation of fatty acids and production performance in dairy cows fed a high-concentrate diet. Thirty-five early-lactation Holstein cows (25 multiparous ruminally fistulated and 10 primiparous nonfistulated) were used in a randomized complete block design (7 blocks) with 33-d periods, including a 5-d pre-treatment collection period used as a covariate. Diets were (1) control, a basal diet [47% nonfibrous carbohydrates, DCAD (Na + K - Cl - S) = 65 mEq/kg of dry matter (DM)] containing 40% forage (including 60% corn silage) and 60% concentrate, (2) K2CO3 (control + K2CO3, 1.8% of DM, DCAD = 326 mEq/kg of DM), (3) KHCO3 (control + KHCO3, 2.6% of DM, DCAD = 324 mEq/kg of DM), (4) KCl (control + KCl, 2.0% of DM, DCAD = 64 mEq/kg of DM), and (5) Na2CO3 (control + Na2CO3, 1.4% of DM, DCAD = 322 mEq/kg of DM). Pre-planned orthogonal contrasts were used to assess the effects of K2CO3 (control vs. K2CO3), buffering ability (K2CO3 vs. KHCO3), DCAD (K2CO3 vs. KCl), and cation type (K2CO3 vs. Na2CO3). Supplementing K2CO3 in a high-concentrate diet did not improve milk fat yield or 4% fat-corrected milk yield. Milk fat concentration was greater in cows fed K2CO3 compared with control (4.03 vs. 3.26%). Milk yield tended to decrease (34.5 vs. 38.8 kg/d) and lactose yield decreased in cows fed K2CO3 as compared with KCl (1.64 vs. 1.87 kg/d). Milk fat concentration of trans-10 18:1 was increased when cows were fed Na2CO3 as compared with K2CO3. A positive relationship was observed between concentrations of anteiso 15:0 and trans-10,cis-12 18:2 in milk fat from cows receiving K2CO3. Milk Na concentration was increased, whereas milk Cl was decreased with K2CO3 as compared with KHCO3 or KCl. A positive relationship was established between milk Cl concentration and milk yield (R2 = 0.34) across all dietary treatments. Cation-anion difference (Na + K - Cl - S) in ruminal fluid was increased with K2CO3 as compared with control or KCl. Blood pH tended to decrease in cows fed KCl compared with K2CO3. Our results suggest that mineral supplementation tends to affect milk and milk fat synthesis and that factors other than DCAD, potassium ion, or buffer ability may be implicated. The variations observed in mineral composition of milk suggest an allostatic process to maintain an ionic equilibrium in mammary epithelial cells in response to mineral composition of the diet.

Meta-analysis of the amino acid digestibility of oilseed meal in growing pigs.

Oilseed meal is an important source of essential amino acids (EAA) for livestock production. It is the second most important ingredient in pig feed after grains. Optimal use of these ingredients requires precise knowledge of amino acid standardized ileal digestibility (SID), which may vary depending on several factors including botanical variety or processing treatments. A meta-analysis was performed in order to derive models for predicting the SID of soybean, cotton and rapeseed meal EAA, based on chemical composition data such as CP, total concentration of each EAA and fibre (crude fibre, ADF and NDF) content. A database of 47 references (224 experimental treatments) was built. A model incorporating processing method of the meals (e.g. cold pressed, expeller pressed, solvent extracted), experimental surgical procedure (T-cannula, re-entrant cannula, post valve T-cannula and ileo-rectal anastomosis) and pig growth stage (BW⩽ or ⩾25 kg) was tested. Results indicated that neither processing nor BW affected EAA SID. NDF was the best predictor of SID (R 2=0.944, 0.836, 0.779, 0.899 and 0.814, respectively, for Lys, Met, Thr, Trp and Val). The total EAA content was the best predictor of digestible content (g/kg diet) for each EAA (R 2=0.990, 0.985, 0.977, 0.985 and 0.978, respectively, for Lys, Met, Thr, Trp and Val). This study shows that routine chemical analyses may be used to predict EAA digestibility with satisfactory accuracy.

Selenium-fertilized forage as a way to supplement lactating dairy cows.

Fertilization with Se improves forage organic Se concentration, but comparisons with other forms of Se supplementation in feeding lactating dairy cows are scarce. Our objective was to compare the effect of Se-enriched forages to dietary sources of inorganic and organic Se. Digestibility, retention, and balance were assessed by measuring Se concentrations in feces, urine, milk, and blood. The resulting effect on antioxidant status and lactation performance of dairy cows was also determined. High-Se silages [1.72 mg of Se/kg of dry matter (DM)] were produced following a spring application of 2.5 kg/ha of Selcote Ultra, whereas low-Se silages (0.05 mg of Se/kg of DM) were produced in the Se-unfertilized portion of the same fields. After a 77±17 d period of Se depletion, 33 late-lactation primiparous Holstein cows were blocked and randomly assigned for 43 d to 1 of 4 experimental total mixed rations fed for ad libitum intake in an unbalanced randomized block design. Treatments consisted of 4 diets: control with low-Se silages, without Se supplement (0.12±0.04 mg of Se/kg of DM); ISe with low-Se silages and inorganic Se (0.80±0.14 mg of Se/kg of DM); YSe with low-Se silages and organic Se from yeast (0.70±0.11 mg of Se/kg of DM); and FSe with high-Se silages, without Se supplement (0.79±0.14 mg of Se/kg of DM). Organic Se, either as YSe or FSe, was more available and more effective to increase blood and milk Se concentrations than ISe. Moreover, FSe was more available than YSe, as cows fed FSe excreted 16 and 22% less Se (as percentage of intake) in feces and urine, respectively, had higher Se apparent absorption (17%), retention (37%), and balance (45%), and had greater concentration of Se in serum (16%) and milk (11%) than cows fed YSe. Antioxidant status (whole blood and plasma glutathione peroxidase, and milk thioredoxin reductase and malondialdehyde) was not affected by treatments. Dry matter intake, yield of actual, energy-corrected, and fat-corrected milk, as well as milk fat and lactose concentrations, were not affected by the dietary treatments. Cows fed ISe had lower milk protein concentration (3.44%) than cows fed YSe (3.58%) or FSe (3.51%). Cows fed Se-supplemented diets had a lower milk somatic cell count than cows fed the control diet. Results from the current study showed that the production of Se-enriched forages is an effective method to supplement dairy cows in Se as it was more available than YSe, and did not alter antioxidant status and performances of lactating dairy cows.

Evaluation of calving indicators measured by automated monitoring devices to predict the onset of calving in Holstein dairy cows.

Dystocias are common in dairy cows and often adversely affect production, reproduction, animal welfare, labor, and economics within the dairy industry. An automated device that accurately predicts the onset of calving could potentially minimize the effect of dystocias by enabling producers to intervene early. Although many well-documented indicators can detect the imminence of calving, research is limited on their effectiveness to predict calving when measured by automated devices. The objective of this experiment was to determine if a decrease in vaginal temperature (VT), rumination (RT), and lying time (LT), or an increase in lying bouts (LB), as measured by 3 automated devices, could accurately predict the onset of calving within 24, 12, and 6 h. The combination of these 4 calving indicators was also evaluated. Forty-two multiparous Holstein cows housed in tie-stalls were fitted with a temperature logger inserted in the vaginal cavity 7±2 d before their expected calving date; VT was recorded at 1-min intervals. An ear-attached sensor recorded rumination time every hour based on ear movement while an accelerometer fitted to the right hind leg recorded cow position at 1-min intervals. On average, VT were 0.3±0.03°C lower, and RT and LT were 41±17 and 52±28 min lower, respectively, on the calving day compared with the previous 4 d. Cows had 2±1 more LB on the calving day. Of the 4 indicators, a decrease in VT≥0.1°C was best able to predict calving within the next 24 h with a sensitivity of 74%, specificity of 74%, positive and negative predictive values of 51 and 89%, and area under the curve of 0.80. Combining the indicators enhanced the performance to predict calving within the next 24, 12, and 6 h with best overall results obtained by combining the 3 devices for prediction within the next 24 h (sensitivity: 77%, specificity: 77%, positive and negative predictive values: 56 and 90%, area under the curve: 0.82). These results indicate that a device that could simultaneously measure these 4 calving indicators could not precisely determine the onset of calving, but the information collected would assist dairy farmers in monitoring the onset of calving.

Timothy silage with low dietary cation-anion difference fed to nonlactating cows.

Decreasing the dietary cation-anion difference (DCAD) by using anion sources before calving reduces hypocalcemia in cows at calving. Reduced DCAD from CaCl2-fertilized timothy hay achieves similar results, but the effects of feeding low-DCAD forage as silage have not been determined. The objective of this study was to evaluate the effect of low-DCAD timothy silage on dry cows. Six nonlactating and nonpregnant Holstein cows were used in a replicated 3 x 3 Latin square. Treatments were 1) control diet (DCAD = 232 mEq/kg of dry matter, DM); 2) low-DCAD diet using a low-DCAD timothy silage (LDTS; DCAD = -21 mEq/kg of DM); and 3) low-DCAD diet using a fermentation by-product (LDBP; DCAD = -32 mEq/kg of DM). Differences between dietary treatments were considered statistically significant at P < or = 0.05 and tendencies were noted when 0.05 < P < 0.10. Compared with the control, feeding LDTS tended to decrease DM intake (10.6 vs. 12.5 kg/d) and decreased urinary pH (6.15 vs. 8.18) as well as apparent digestibility of DM (67 vs. 69%). Blood pH (7.37 vs. 7.42), HCO3- (25.3 vs. 27.5 mM), and base excess (0.4 vs. 3.1 mM) were decreased, and blood Cl- (29.6 vs. 29.1 mg/dL) was increased. Apparently absorbed Na and Cl were higher and apparently absorbed K, P, and digested ADF were lower for LDTS compared with the control. Both LDTS and LDBP resulted in similar DM intake. Urinary pH tended to be higher (6.15 vs. 5.98) and percentage of digested DM was lower (67 vs. 70%) with LDTS compared with LDBP. Blood ionized Ca (5.3 vs. 5.4 mg/dL) tended to be lower and blood Cl- (29.6 vs. 30.1 mg/dL) was lower, whereas blood pH (7.37 vs. 7.33), HCO3- (25.3 vs. 21.5 mM), and base excess (0.4 vs. -3.8 mM) were higher with LDTS compared with LDBP. Apparent absorption of Na, Cl, S, and P, as well as apparent digestion of acid detergent fiber, neutral detergent fiber, and N were lower, and K, Cl, S, P, Mg, and N were less retained with LDTS compared with LDBP. Results confirm that low-DCAD timothy silage can be used to produce a compensated metabolic acidosis by decreasing the DCAD of rations served to nonlactating dairy cows.

Hay to reduce dietary cation-anion difference for dry dairy cows.

Timothy grass has a lower dietary cation-anion difference [DCAD = (Na + K) - (Cl + S)] than other cool-season grass species. Growing timothy on low-K soils and fertilizing it with CaCl2 could further decrease its DCAD. The objective of this study was to evaluate the effects of feeding low-DCAD timothy hay on dry dairy cows. Six nonpregnant and nonlactating cows were used in a replicated 3 x 3 Latin square. Treatments were as follows: 1) control diet (control; DCAD = 296 mEq/kg of dry matter); 2) low-DCAD diet based on low-DCAD timothy hay (L-HAY; DCAD = - 24 mEq/kg of dry matter); and 3) low-DCAD diet using HCl (L-HCl; DCAD = - 19 mEq/kg of dry matter). Decreasing DCAD with L-HAY had no effect on dry matter intake (11.8 kg/d) or dry matter digestibility (71.5%). Urine pH decreased from 8.21 to 5.89 when L-HAY was fed instead of the control. Blood parameters that decreased with L-HAY were base excess (- 0.4 vs. 3.8 mM) and HCO3- (23 vs. 27 mM), and blood parameters that increased were Ca2+ (5.3 vs. 5.1 mg/dL), Cl- (30.5 vs. 29.5 mg/dL), and Na+ (60.8 vs. 60.1 mg/dL). Compared with the control, L-HAY resulted in more Ca in urine (13.4 vs. 1.2 g/d). Comparing L-HAY with L-HCl, cow dry matter intake tended to be higher (11.5 vs. 9.8 kg/d), and blood pH was higher (7.37 vs. 7.31). Urine pH; total dry matter; Ca, K, P, and Mg apparent absorption; and Ca, K, Na, Cl, S, P, and Mg apparent retention were similar. Absorption as a percentage of intake of Na and Cl was lower for L-HAY as compared with L-HCl. In an EDTA-challenge test, cows fed L-HAY regained their initial level of blood Ca2+ twice as quickly as the control treatment (339 vs. 708 min); there were no differences between L-HAY and L-HCl. This experiment confirms that feeding low-DCAD hay is an effective means of decreasing the DCAD of rations and obtaining a metabolic response in dry dairy cows.

Long-term survival of heart transplant recipients with lung cancer: the role of chest computed tomography screening.

OBJECTIVE: We sought to evaluate the screening modality and outcome of lung cancer occurring in heart transplant recipients (HTR) during a 21-year period. METHODS: We conducted a retrospective review to investigate the incidence, risk factors, screening modality, treatment, and outcomes in HTR with lung cancer. We compared them with a case-matched HTR control group. RESULTS: Out of 829 recipients of heart transplants, 19 cases of bronchogenic carcinoma were found either by routine chest X-ray (n = 10), chest computed tomographic (CT) scanning (n = 4), or by assessment of clinical symptoms (n = 5). The mean time from transplantation to bronchogenic carcinoma diagnosis was 68.8 +/- 42.4 months. A history of smoking was the only risk factor in HTR with bronchogenic carcinoma compared to their case-matched HTR control group ( P < 0.05). Of 18 patients with non-small cell lung cancer (NSCLC), 13 underwent surgery and 5 with advanced cancer underwent chemotherapy and/or radiotherapy. NSCLC was diagnosed by chest X-ray (n = 10), and 6 of these patients died after an average of 43.7 +/- 62.2 months following cancer detection. NSCLC was also diagnosed on the basis of clinical symptoms (n = 4), and 2 of these patients died after a mean follow-up of 9 +/- 4.2 months after cancer diagnosis. All 4 patients in whom cancer was detected by CT scan were alive at an average of 53.5 +/- 36.7 months following cancer detection. The survival rates did not differ between the study and control groups ( P = 0.5). CONCLUSIONS: Optimal outcomes of treatment for primary lung cancer after heart transplantation seem to be related to early detection. A high proportion of deaths from NSCLC may be prevented by chest CT scan screening.

Milk from forage as affected by rumen degradable protein and corn grinding when feeding corn- and alfalfa silage-based diets.

To increase the production of milk from forage (MF), a previous experiment with alfalfa silage showed the importance of a complementary combination of concentrates and forages offered. When corn silage is fed with alfalfa, increasing the rumen degradable protein (RDP) content in the diet should allow a better utilization of forage energy. To evaluate this hypothesis, 8 multiparous Holstein cows in early lactation were used in a replicated 4 x 4 Latin square design with 3-wk periods. Diets were fed as total mixed rations and were formulated to provide similar levels of net energy for lactation and crude protein but differing in RDP. Corn and alfalfa silages were used. Treatments were: 1) cracked corn-based concentrate providing low RDP [level recommended by the NRC (2001); RDP = 11.1% of dry matter (DM)]; 2) cracked corn-based concentrate providing medium RDP (RDP = 12.8% of DM); 3) cracked corn-based concentrate providing high RDP (RDP = 14.5% of DM); and 4) ground corn-based concentrate providing high RDP (RDP = 13.6% of DM). The first 3 treatments, using cracked corn, were compared on the basis of their RDP level. For these treatments, MF, calculated on a protein basis, decreased and the average of MF calculated on an energy basis and MF calculated on a protein basis tended to decrease as RDP increased. There was no difference for MF calculated on an energy basis between treatments. Increasing dietary RDP levels decreased the milk yield (from 32.8 to 30.7 kg/d) and milk protein yield (from 1,094 to 1,005 g/d) but not the milk fat yield. The milk urea N concentration increased as RDP increased. This suggests that there is no advantage of feeding RDP above the NRC recommendations when diets are based on corn and alfalfa silage. At high RDP levels (treatments 3 and 4), ground corn supported higher DM intake and yields of milk and protein than did cracked corn. Milk from forage, calculated on a protein basis, was higher and milk urea N decreased with ground corn. Even with corn silage in the diet, grinding corn grain proved to be beneficial to milk yield and MF production.

Impact of lowering dietary cation-anion difference in nonlactating dairy cows: a meta-analysis.

A meta-analysis of previous studies was performed to clarify the response of prepartum dairy cows to lowering dietary cation-anion difference (DCAD) and to compare different equations that have been proposed to calculate DCAD. Twenty-two published studies containing 75 treatment groups met criteria for inclusion in the meta-analysis. Five different equations used to calculate DCAD were compared for their association with clinical milk fever and urinary pH. The DCAD equation (Na + K) - (Cl + 0.6 S) was the most highly associated with clinical milk fever (R(2) = 0.44) and urinary pH (R(2) = 0.85). Lowering DCAD reduced clinical milk fever but also reduced DM intake. Lowered DCAD was associated with reduced urinary pH, blood bicarbonate, and blood CO(2), suggesting a metabolic acidosis with respiratory compensation. Blood pH was very slightly lowered by lowered DCAD. Lowering DCAD increased ionized Ca in blood before and at calving. The model predicted that lowering DCAD from +300 to 0 mEq/kg reduced risk for clinical milk fever from 16.4 to 3.2%, reduced urinary pH from about 8.1 to 7.0, and reduced DM intake by 11.3%.

Milk from forage as affected by carbohydrate source and degradability with alfalfa silage-based diets.

Milk from forage (MF) is an estimation of the milk produced solely from forage intake. It is calculated by subtracting milk production theoretically allowed by concentrates from total milk production, assuming that maintenance requirements are covered by the forage portion of the diet. Eight multiparous Holstein cows in early lactation were used in a replicated 4 x 4 Latin square design to evaluate the impact on MF of different sources of carbohydrate with forage that was high in RDP. Diets were alfalfa-based total mixed rations that were formulated to provide similar concentrations of NEL and CP while differing in rumen degradability of concentrate carbohydrates. Treatments were 1) cracked corn (control), 2) ground corn (GC), 3) GC plus wheat starch (GC+S), and 4) GC plus dried whey permeate (GC+W). The GC and the GC+S treatments increased MF as calculated on a protein basis (14.8 vs. 10.5 kg) and increased average MF production (8.6 vs. 5.5 kg) compared with the control. Protein of forage was used more efficiently with GC and with GC+S, as shown by the lower differences between allowable MF, which estimates the potential for milk production from forage, and MF on a protein basis for these 2 treatments when compared with the control. Compared with the control, DMI increased with GC and GC+S; GC+W yielded the highest DMI. Milk production with GC+W (35.8 kg/d) was lower than with GC and GC+S (37.5 kg/d) but was higher than the control (34.0 kg/d). Milk fat concentration was higher with GC+W and lower with GC+S; GC and the control had intermediate values. Milk urea was higher with the control diet compared with the other 3 treatments. Results emphasize the advantage of using concentrates of higher degradability in the rumen to improve MF and milk production when feeding silage with high rumen-degradable protein.