Forty meat or dairy kids were blocked within breed according to body weight. Kids within each block were then randomly allotted to a concentrate-based diet or an intensive rotational grazing system. Kids fed the concentrate-based diet were offered hay ad libitum and fixed amounts of whole corn and soybean meal to meet the requirements for maintenance and daily gain. Grazing kids from each breed were stocked in groups and offered a new paddock every day. Dry matter intake was not different between breeds. Meat kids had a greater average daily gain than dairy kids, but feeding treatments did not affect the growth rate. Dairy kids had greater anterior cuts (neck and shoulder), whereas meat kids tended to have greater posterior cuts (loin and leg). Meat kids accumulated more fat when they were fed concentrate in comparison with pasture, whereas this variable tended to be less influenced by dietary treatments in dairy kids. Meat of pasture-fed kids had greater Warner–Bratzler shear force and glycolytic potential, and lower ultimate pH than meat of concentrate-fed kids. The n-6/n-3 fatty acid ratio of intramuscular fat was almost 4-fold greater in concentrate- than pasture-fed kids; this ratio was 1.4-fold greater in dairy than meat kids.

The objective of the current trial was to evaluate the effect of feeding four different forage species on milk yield and composition, including protein and fatty acid profiles, in dairy goats. Two grasses (Timothy; mown at early heading, and Italian ryegrass; mown at 25 cm height) and two legumes (Alfalfa and White clover; both mown at 10% bloom) were harvested and conserved as silage. Twelve dairy goats of three different breeds (4 Alpine, 4 Toggenburg, and 4 Saanen) in late lactation were used in a replicated 4 × 4 Latin square design. Goats were offered ad libitum access to the tested forages supplemented with 180 g/d of concentrates based on rolled barley and heat-treated soybean meal. DM intake was lower with timothy, intermediate with ryegrass and white clover, and greater with alfalfa. Milk yield was lower with timothy as compared with the other three silages. Milk fat yield was similar among treatments. Milk CP yield was lower with timothy as compared with the other three silages. Milk N efficiency (N secreted/N intake) was greater with timothy, intermediate with ryegrass, and lower with the two legume silages. The proportion of true protein as a percentage of CP was lower in milk from goats fed legume as compared with grass silages. Proportions of casein and whey protein expressed as percentages of true protein were greater with timothy, intermediate with ryegrass and white clover, and lower with alfalfa. Among grass silages, intake and milk secretion of cis-9, cis-12 cis-15 18:3 was greater with ryegrass than with timothy. As a result, the transfer efficiency from dietary intake to secretion in milk was not different between these two treatments. Fewer differences were observed regarding legume forages, as cis-9, cis-12, cis-15 18:3 intake and milk secretion were similar with alfalfa and white clover. However, the transfer of cis-9, cis-12, cis-15 18:3 from diet to milk was highest when feeding alfalfa. In conclusion, forage species fed to dairy goats influence milk composition in terms of fatty acids and protein fractions, which can potentially impact the nutritive value and technological properties of milk.

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.

Determining the dynamics of crop nitrogen (N) uptake is essential to optimize N management and increase the sustainability of crop production. The concept of critical N concentration helps to achieve this goal by defining the minimum shoot N concentration required to produce the maximum aerial biomass at a given time during the crop cycle. The objective of this study was to determine new critical N dilution curves of the main annual field crops used in Canada (spring wheat, canola and corn) using a classical approach well established and a new Bayesian approach and compare these curves with the curves previously published. A total of 557 data for the three crops were used, covering a wide range of pedoclimatic conditions, crop management and cultivars across Canada. These data were processed following a classical statistical approach involving two steps to determine critical points used to calculate the parameters of the critical N dilution curve and then validate these curves against N limiting and non-limiting points. Data were also processed with a new one step Bayesian approach which allows estimating the 95% credibility intervals of the calculated critical curves. For spring wheat, our analysis confirmed the results of a previous study showing that the critical N curve established for winter wheat was not adequate for spring wheat. The critical N dilution curve determined with the classical approach (N-c = 4.14 W-0.51) performed well in separating the N limiting to the N non-limiting data of the validation dataset. The use of a larger dataset than in the previous study conducted for spring wheat in eastern Canada allowed us to demonstrate that new critical, minimum and maximum N dilution curves for spring wheat has a larger domain of validity than suggested by results of previous studies. Our study shows the strong interaction between plant N and water status, and that N dilution concept allowed us to reveal the occurrence of interaction between water and N stresses for crops in Western Canada, explaining the lower efficiency of N fertilizer in western than in eastern regions.& nbsp;For corn, the refined critical N dilution curve was very close to the critical N dilution curve determined in France and in eastern Canada, but the Bayesian approach allowed to propose a specific critical N curve for Canada (N-c = 3.07 W-0.40). In addition, minimum and maximum N dilution curves for corn were determined in Canada's pedoclimatic conditions. For canola, the new critical (N-c = 4.26 W-0.26), minimum and maximum curves determined in this study were close to the curves found in previous studies during the vegetative stages. In addition, a new critical N curve valid after the flowering stage was determined.

Highlights Juice extraction resulted in a decrease in the nutritive value of the bagasse as compared with the initial biomass. Silages made from the second pressing bagasse were well conserved. Sweet sorghum silage has a better nutritive value than sweet pearl millet. Abstract . Pressing the biomass of sweet sorghum and sweet pearl millet in-field is one of the suggested options for bioethanol production. The extracted juice can be delivered to an ethanol plant, and the bagasse (pressing residue) can be used for ruminant feeding. Efficient carbohydrate extraction is highly important for good ethanol yield. However, enough carbohydrates must remain in the bagasse for its adequate conservation as silage. In this study, the ensilability and the chemical composition of the second pressing bagasse of sweet sorghum and sweet pearl millet were investigated. The bagasse was obtained following a second pressing of the first pressing bagasse after its impregnation with water based on three water:bagasse ratios (0.5, 1, and 1.5). Results indicated that water:bagasse ratio did not affect water-soluble carbohydrate (WSC) extraction for both crops. The second pressing bagasse of sweet sorghum and sweet pearl millet contained 80.5 ±4.6 and 60 ±4.6 g of WSC kg-1 dry matter (DM), respectively. The second pressing bagasse of both crops had reduced nutritive value compared to the initial biomass, i.e., higher neutral detergent fiber (NDF) and acid detergent fiber (ADF) concentrations along with lower non-structural carbohydrate (NSC) concentration, in vitro true digestibility of DM (IVTD), and in vitro NDF digestibility (NDFd). The second pressing bagasses of both crops also showed good ensilability, but sweet sorghum bagasse silages were of better nutritive value than sweet pearl millet bagasse silages (ADF = 446.2 ±3.7 vs. 463.2 ±3.7 g kg-1 DM, IVTD = 813.8 ±3.4 vs. 708.8 ±6.8 g kg-1 DM, and NDFd = 741.8 ±4.8 vs. 596.2 ±8.5 g kg-1 NDF, respectively). The water:bagasse ratio used for bagasse impregnation before the second pressing only affected the NDF concentration of silages, as a higher NDF concentration was obtained with a water:bagasse ratio of 1.5. Sweet sorghum and sweet pearl millet can be considered dual-purpose crops; the extracted juice can be fermented into ethanol, and the second pressing bagasse can be used to make good-quality silage. Keywords: Bagasse impregnation, Nutritive value, Silage, Sweet pearl millet, Sweet sorghum, Water-soluble carbohydrates.

This study investigated the use of K2CO3 as dietary buffer to prevent or to recover from low milk fat production when early-lactating dairy goats are fed a high-starch, low-fiber (HSLF) diet. At kidding, 30 Alpine goats housed in pens with Calan gate feeders received a total mixed ration with a forage-to-concentrate ratio of 55:45 on a dry matter (DM) basis for a baseline period of 27 ± 4 d. Goats (milk yield, 4.14 ± 0.88 kg/d; milk fat, 4.28 ± 0.52%; mean ± SD) were then assigned to 1 of 10 blocks according to parity (first vs. second or more) and milk fat concentration, and fed a HSLF diet containing 45% forages and 55% concentrates for 2 experimental periods of 28 d. Treatments were identified as (1) control, in which the HSLF diet was fed throughout both periods; (2) preventive, in which the HSLF diet supplemented with K2CO3 (1.6% of DM) was fed during both periods; and (3) recovery, in which the HSLF diet was fed during the first period (P1) and the HSLF diet supplemented with K2CO3 was fed during the second period (P2). Data from P1 and P2 were analyzed separately. In P1, preplanned contrasts were used to evaluate the preventive effect of K2CO3 (control and recovery, both groups receiving the same diet during this period, vs. preventive), and in P2, to assess the potential of K2CO3 to alleviate an already existing state of low milk fat (control vs. recovery and preventive vs. recovery). Feeding the HSLF diet in P1 moderately decreased milk fat concentration (−16%) and yield (−13%) as compared with baseline. Dietary addition of K2CO3 decreased DM intake by 12 and 14% in P1 and P2, respectively. Ruminal pH was not different among treatments. There was also no significant difference in milk yield (4.13 and 3.71 kg/d on average in P1 and P2, respectively) for any tested contrasts. In P1, milk fat concentration and yield did not differ among goats fed control (3.58% and 151 g/d, respectively) and preventive (3.67% and 148 g/d, respectively) diets. In P2, milk fat concentration and yield did not differ among goats fed the control diet (3.38% and 137 g/d, respectively), and diets where K2CO3 was used as preventive (3.44% and 126 g/d, respectively) or recovery treatment (3.25% and 113 g/d, respectively). Supplementing a high-concentrate diet with 1.6% K2CO3 was therefore not effective in either preventing or suppressing already existing conditions of low milk fat production in dairy goats.

Forages can contribute to the nutrient supply for sows but the extent to which they can replace concentrate feeding is not well known. The objective of this study was to assess the effect of level of feed restriction and type of forage on the performance and activity of gestating sows under outdoor conditions. A total of 45 sows were distributed among three treatments, with five replicates of three sows/treatment, from week 5 of gestation until farrowing. Treatments differed in the daily level of concentrate feed provided and the type of forage offered during gestation: 90% of metabolisable energy (ME) requirements provided by concentrates and free access to a pasture (P90); 40% of ME requirements provided by concentrates and free access to a pasture (P40); and 40% of ME requirements provided by concentrates and free access to a bare paddock with hay ad libitum (H40). From farrowing to weaning (5 weeks), concentrate feed was offered to all sows ad libitum. Body weight and backfat thickness (BF) were measured seven times during gestation and lactation. Postures of sows and time spent in the pasture were assessed at the beginning, middle and end of gestation. Forage intake was estimated with a method based on sow performance using the InraPorc® model. At farrowing, P90 sows were heavier and had greater BF than P40 and H40 sows. At weaning, P90 sows maintained a higher BW and tended to have greater BF than H40 sows, but no longer differed from P40 sows. Treatments did not influence litter size, but piglets from P40 sows were lighter at birth than those from P90 sows (1.44 vs. 1.69 kg, P = 0.004). In late gestation, P90 sows spent less time standing over 24 h and less time in the pasture during daytime than P40 sows, suggesting less foraging behaviour. Sows fed concentrates to meet 40% of ME requirements during gestation did not consume enough forage to maintain the same body condition as sows fed at 90% of ME requirements. Despite their inability to fully compensate for concentrate restriction during gestation by consuming more forage, P40 sows reached a similar body condition to P90 sows at weaning. In conclusion, forage intake for outdoor gestating sows can compensate a concentrate feed reduction of 10% and possibly more, but not as much as 60%.

Shifting the cutting of grass from morning to afternoon has been shown to increase the concentration of nonstructural carbohydrates (NSC) in forages. We compared the effects of diets (66:34, forage:concentrate ratio) containing a mix (% of the diet dry matter) of baleages (46.5%) and silages (19.3%) harvested from timothy cut in the afternoon (p.m.-cut TIM diet) or morning (a.m.-cut TIM diet) on omasal flows of NSC and nitrogenous fractions, ruminal and total-tract digestibilities of nutrients, plasma concentration of AA, and milk yield and composition. Eight ruminally cannulated Holstein cows averaging (mean ± standard deviation) 31.4 ± 6.13 kg/d of milk, 136 ± 17.0 d in milk, and 611 ± 66.4 kg of body weight in the beginning of the experiment were used in a crossover design with 21-d periods (14 d for diet adaptation and 7 d for data and sample collection). Intake of total ethanol-soluble carbohydrates (TESC; +150 g/d), starch (+129 g/d), and total NSC (TESC plus starch = +278 g/d) was greater with feeding the p.m.- than the a.m.-cut TIM diet. Likewise, the apparent ruminal digestibilities of TESC (+149 g/d), starch (+167 g/d), and total NSC (+316 g/d) increased in the p.m.-cut TIM diet. Diets, however, had no effect on the omasal flows and apparent ruminal and total-tract digestibilities of dry matter and organic matter. Intake of N increased in cows fed the p.m.- versus the a.m.-cut TIM diet (562 and 528 g/d, respectively) despite no effect of diets on dry matter intake. Diets did not affect the omasal flows of total nonammonia N, total bacterial nonammonia N, nonammonia and nonbacterial N, and individual AA, and the efficiency of microbial protein synthesis in the rumen. Contrarily, supply of rumen-degradable protein increased (+9.2%) in cows fed the p.m.-cut TIM diet, with this response driven by the 6.4% increase in N intake. Plasma concentrations of essential and nonessential AA followed the omasal flow of AA and were not changed by diets. Feeding the p.m.- versus the a.m.-cut diet significantly increased yields of 4% fat-corrected milk and milk fat, and tended to increase energy-corrected milk, milk true protein, and milk lactose yields. Overall, feeding the p.m.-cut TIM diet to mid-lactation dairy cows did not improve microbial protein synthesis and omasal flow of AA, and these responses were in line with the lack of a treatment effect on dry matter intake.

Legacy phosphorus (P), corn (Zea mays L.) hybrids, weather conditions, and regulation on land-applied manure affect site-specific mineral P requirements. Mineral P fertilizers are still banded at corn seeding as insurance policy even where manure P is applied in compliance with regulation in Eastern Canada. Our objective was to measure the effects of site-specific factors on the response of corn hybrids of the "new" era (1991+) to mineral and manure P fertilization under regulatory constraints. A dataset of 370 corn P fertilizer trials conducted between 1998 and 2004 in Quebec, Canada, comprised trials using mineral P alone (229 trials) or in combination with manure (141 trials). Linear mixed statistical models tested the effect of P fertilization on seedling biomass, grain yield, grain bulk density, and grain moisture content as affected by weather and soil indices. Early plant growth proved to be a poor indicator of final crop performance. Where no manure was applied, grain yield and quality were affected primarily by soil pH, texture, and genesis. There were responses to P additions only where the saturation index (P/Al)(M3) was less than 5%. Mineral P fertilizers showed no significant effect on crop performance where manure was applied, but manured soil generally showed (P/Al)(M3) percentages exceeding 5%. Banding mineral P at corn seeding where manure was applied at rates complying with the regulation and the (P/Al)(M3) percentage exceeded 5% appeared to be a waste of resource under the soil and climate conditions in Eastern Canada.

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.

To optimize the use of conserved forages in the feeding of sows, it is necessary to better understand how conservation methods influence their forage intake. The aim of this study was to determine sows' preferences for forages from different conservation methods. Forages composed of red clover and timothy, offered either fresh, as haylage, or hay were compared using two blocks of 6 sows housed in individual pens. A voluntary intake test was done by offering forage from each conservation method separately (one forage/day) during 45 min over 3 days according to a double 3 x 3 Latin square design. A preference test took place over 6 consecutive days, during which all 3 combinations of two forage conservation methods (one combination/day) were offered twice to each sow for 45 min. The difference among treatments in the voluntary intake of sows was determined using a variance analysis followed by Tukey tests for post hoc comparisons. During preference tests, difference in intake between the two forages offered was determined using a paired Student's t-test and the most ingested forage was considered as the preferred one. Sow voluntary DM intake was greater for haylage than hay, and intermediate for fresh forage. The preference tests revealed that sows preferred haylage over hay and fresh forage, whereas fresh forage was preferred over hay. The sows' preference for haylage over fresh forage and hay needs to be investigated further, but chemical composition and/or sensory characteristics such as smell and taste may have played a role.

Providing forage to feed-restricted pregnant sows may improve their welfare by reducing their high feeding motivation. The aim of this study was to determine sows' preferences for four forage mixtures cultivated in Canada. Forage mixtures were compared when offered either fresh or dry. The four forage mixtures were composed of different proportions and species of legumes (alfalfa (Alf) or red clover (Clo)) and grasses (tall fescue (F) and/or timothy (T)): (1) Alf-F, (2) Alf-F-T, (3) Clo-T and (4) Clo-F-T. Voluntary intake was measured, and preference tests were carried out for two experiments: one in spring for fresh forages ( n = 8) and the other in autumn for hays ( n = 8) with different sows housed in individual pens and fed a concentrated diet meeting their nutritional requirements for maintenance and foetal growth. Voluntary intake was measured by offering each forage mixture separately (one forage mixture/day) during 90 min according to a 4 × 4 Latin square design replicated four times. During preference tests, all six combinations of two forage mixtures were offered once (one combination/day) for 45 min to each sow. Individual forage intake was measured, and feeding behaviour was observed. Forages were analysed for botanical and chemical composition. Difference in voluntary intake among the four forage mixtures was determined using a variance analysis followed by Tukey tests for post hoc comparisons. In preference tests, differences between the two forage mixtures offered were determined using a paired Student's t test, and the most ingested forage mixture was considered the preferred one. Results from both experiments revealed clear preferences for some forage mixtures when offered either fresh or dry. Forage mixtures with a greater proportion of legumes (AlfT and CloT) were preferred over forage mixtures with a higher proportion of grasses (AlfFT and CloFT). The AlfFT and CloFT forage mixtures contained at least 30% of fescue; therefore, the greater preference for the AlfT and CloT forage mixtures could also be due to the absence of fescue. Sows preferred forages with low DM and NDF concentrations and high CP and non-structural carbohydrates concentrations. Based on results from previous studies, the preferences seen in the present study are most likely due to the greater proportion of legumes, although an effect of tall fescue in preference cannot be excluded. Therefore, offering forages with a high proportion of legumes would be a good strategy to maximise both fresh and dry forage intake in pregnant sows.

Silage making can be conveniently divided into field, ensiling, storage, and feed-out phases. In all of these stages, controllable and uncontrollable components can affect silage quality. For instance, silages produced in hot or cold regions are strongly influenced by uncontrollable climate-related factors. In hot regions, crops for silage are influenced by (1) high temperatures negatively affecting corn yield (whole-crop and grain) and nutritive value, (2) butyric and alcoholic fermentations in warm-season grasses (Panicum, Brachiaria, and Pennisetum genera) and sugarcane, respectively, and (3) accelerated aerobic deterioration of silages. Ensiling expertise and economic factors that limit mechanization also impair silage production and utilization in hot environments. In cold regions, a short and cool growing season often limits the use of crops sensitive to cool temperature, such as corn. The fermentation triggered by epiphytic and inoculated microorganisms can also be functionally impaired at lower temperature. Although the use of silage inoculants has increased in Northern Europe, acid-based additives are still a good option in difficult weather conditions to ensure good fermentation quality, nutritive value, and high intake potential of silages. Acid-based additives have enhanced the quality of round bale silage, which has become a common method of forage preservation in Northern Europe. Although all abiotic factors can affect silage quality, the ambient temperature is a factor that influences all stages of silage making from production in the field to utilization at the feed bunk. This review identifies challenges and obstacles to producing silages under hot and cold conditions and discusses strategies for addressing these challenges.

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.

Extensive degradation of proteins combined with insufficient readily fermentable energy in alfalfa (Medicago sativa L.) results in poor forage N utilization by ruminants and substantial N losses into the environment. Selection for increased nonstructural carbohydrate (NSC) concentration in forage crops is considered to be an effective approach to improve the feeding value of forage. Our objective was to assess the extent of genetic variability for NSC concentration and to identify DNA polymorphisms associated with that trait in alfalfa. A divergent selection was applied for forage NSC concentration among 560 alfalfa genotypes. Ten plants with high (NSC+), 10 plants with low (NSC-) and 10 plants randomly selected within the base population (NSC0) were selected to make three populations. Genetic variability for NSC concentration in alfalfa was observed (ranging from 73 to 230 mg/g DM under field conditions). Genotypes that consistently maintained high or low NSC concentrations were singled out under repeated assessments and were subsequently confirmed with clonal propagules. Although it is effective, phenotypic selection for NSC is resource intensive. Our identification of DNA polymorphism associated with this trait suggests the possibility of developing marker-assisted approaches to facilitate the identification of superior genotypes.

Shifting cutting from morning to afternoon has been shown to increase the concentration of nonstructural carbohydrates in forages. We hypothesized that, compared with a total mixed ration containing timothy baleage and silage cut in the morning (a.m.-cut TIM), a total mixed ration containing timothy baleage and silage cut in the afternoon (p.m.-cut TIM) would improve animal performance and N use efficiency in mid-lactation Holstein cows due to enhanced supply of ruminal fermentable energy. The objective of this study was to compare the effects of p.m.- versus a.m.-cut TIM on milk yield, concentrations and yields of milk components, ruminal metabolism, and plasma concentrations of AA in mid-lactation Holstein cows. Ten (6 ruminally cannulated) primiparous cows averaging 139 ± 13 d in milk and 550 ± 56 kg of body weight, and 6 (2 ruminally cannulated) multiparous cows averaging 128 ± 11 d in milk and 632 ± 57 kg of body weight at the beginning of the experiment, were used in a crossover design. Each period lasted 21 d with 14 d for diet adaptation and 7 d for data and sample collection. The concentration of nonstructural carbohydrates (water-soluble carbohydrates plus starch) was numerically greater in the p.m.- versus the a.m.-cut TIM and averaged 13.2 ± 1.06% and 12.2 ± 1.13%, respectively. Treatment × parity effects were observed for milk urea N, feed efficiency, and milk N efficiency, whereas parity effects were observed for nutrient intake, milk yield, and plasma concentration of several essential and nonessential AA. Intakes of dry matter (19.3 versus 18.6 kg/d) and nonstructural carbohydrates (2.56 versus 2.31 kg/d), and yields of 4% fat-corrected milk (23.1 versus 22.2 kg/d), energy-corrected milk (25.0 versus 24.1 kg/d), milk fat (0.91 versus 0.88 kg/d), and milk protein (0.77 versus 0.73 kg/d) were all greatest with feeding p.m.-cut TIM. Milk yield (23.5 versus 22.7 kg/d) tended to increase in cows fed p.m.-cut TIM. The ruminal fermentation profiles and plasma concentrations of AA were mostly unaffected by treatments. However, ruminal valerate (1.01 versus 1.17 mol/100 mol) and plasma Gly (172 versus 188 µM) were lowest with feeding p.m.-cut TIM. Overall, feeding mid-lactation dairy cows a total mixed ration that consisted of p.m.-cut timothy baleage and silage significantly increased dry matter intake and yields of milk, milk fat, and milk protein.

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.