The effect of dietary fiber on endogenous N secretion was studied using a 15N isotope dilution technique in four fistulated Holstein cows. Two isonitrogenous diets differing only in fiber (NDF and ADF) content were used in a crossover design. One diet (HF) contained 37.4% NDF, while the other (LF) contained 23.3%. A new model was developed to estimate endogenous N secretions and losses for the preintestinal, intestinal, and the total sections of the gastrointestinal tract. Three precursor pools: TCA-soluble fraction of plasma, intestinal mucosa, and milk were compared. Although endogenous losses estimated with the model were numerically different for each precursor pool selected (TCA-soluble fraction > mucosa > milk), treatment effects were similar. As intestinal mucosa is probably closest to the precursor pool, these data are discussed. Non-urea N endogenous secretions contributed 13% of the duodenal N flow but were not affected by the fiber content of the diet. The nonurea N endogenous flow at the duodenum was comprised of approximately equal inputs from endogenous N direct, and that incorporated into the microbial biomass. Total endogenous N flows at the duodenum exceeded, by nearly twofold, estimated inputs of urea-N to microbial biomass. Metabolic fecal output averaged 17% of fecal N and was not affected by level of dietary fiber, but net losses from secretions occurring in the small intestine were higher with the low fiber diet. Overall, endogenous N secretions represented 30% of total digestive tract protein synthesis.

Plasma concentrations of hormones and metabolites were measured in growing steers to establish their relation with degree of feed restriction. Sixty medium frame beef steers (259 ± 29 kg) were divided in groups of five and fed during 3 mo either timothy (T) or bromegrass (B) harvested at stem elongation of the first cut or at boot stage of the aftermath. Forages were fed at one of three levels of intake: ad libitum (FF), 80% of FF, or 65% of FF. Plasma concentrations of growth hormone (GH), insulin, glucagon, insulin-like growth factor-1 (IGF-1), glucose and nonesterfied fatty acids (NEFA) were measured on day 1 and day 78 before the morning meal. The effect of a meal on GH, insulin, glucagon, IGF-1, glucose and NEFA concentrations was also determined in 24 steers sampled from 3 h before to 3 h after a meal. Severity of feed restriction resulted in a linear decrease (P < 0.05) of plasma glucagon (0.139, 0.130, 0.121 ± 0.005 ng mL–1) and IGF-1 (109, 98, 84 ± 7 ng mL–1). Insulin concentration tended to be affected quadratically (0.37, 0.35, 0.27 ± 0.04ng mL–1 for FF, 80% of FF and 65% of FF, respectively, P < 0.10). Ingestion of a meal resulted in a decrease (P < 0.05) of GH, NEFA and glucose, and an increase of insulin concentrations (P < 0.05). There was a positive correlation (r = 0.53, P < 0.05) between IGF-1 and average daily gain, and lipid percentage of carcasses suggesting that IGF-1 is related to growth rate and fat accumulation in growing steers. Key words: Feed restriction, growth hormone, insulin, IGF-I, metabolites, grass silage

A study was conducted to determine the influence of intensity of mechanical conditioning on the nutritive value of alfalfa conserved as hay or silage. Fresh alfalfa was mowed and conditioned at three levels of maceration prior to field wilting during 45 h for silage (29–39% DM) or 94 h for hay (87% DM, after barn-curing), under light rain conditions during the first 2 d. The conditioning treatments were: control (conventional mowing-conditioning), light maceration (one passage through three knurled steel rolls), medium maceration (two passages), and intense maceration (three passages). Concentrations of NDF, ADF, hemicellulose, CP-NDF, and CP-ADF increased linearly (P < 0.001) with the level of maceration. Silage pH, acetic acid, propionic acid, and butyric acid increased, while lactic acid decreased (P < 0.001), with the level of maceration. The effective rumen degradabilities of DM, CP, and NDF, measured with fistulated cows, were not affected (P > 0.10) by the level of mechanical conditioning. Forty-eight male sheep (46.8 ± 6.7 kg BW) were fed a 100% forage diet according to a completely randomized design with a 2 × 4 factorial arrangement of treatments (two storage methods and four levels of conditioning). Under restricted feeding, DM, NDF, ADF, and hemicellulose digestibilities decreased linearly (P < 0.001) with the level of maceration. However, the digestibility of CP-NDF increased with the level of maceration; the effect was more important in hay than in silage (P < 0.001 for the interaction). When silages were fed ad libitum to 24 sheep, daily DMI was 2.31, 2.88, 2.76, and 2.41% of BW and DM digestibility was 60.8, 60.1, 56.2, and 46.7%, for control, light, medium, and intense maceration, respectively (P < 0.01). The results suggest that light maceration increases DM intake while maintaining digestibility of forages fed to sheep. Because of humid conditions and potential soil contamination due to multiple windrow pickup, intense maceration caused severe nutrient loss, which might be avoided under dry field wilting and good storage conditions. Key words: Alfalfa, hay, silage, digestion, degradability, intake

Eighty-nine calves born of dams from British (50% Hereford and 50% Red Angus) and Continental (50% Simmental and 50% Maine Anjou) breeds crossed with Charolais (CH), Belgian Blue (BB) and Piedmontese (PM) sires were used to evaluate the productivity of using double-muscled cattle in terminal crosses. Breed of sire did not exert a significant effect on any parameter measured before weaning. Calving difficulty was related to breed of dam, being higher in British than in Continental dams (P < 0.05) and tended to be higher for male than for female calves (P < 0.10). Average daily gains to weaning and weight corrected at 200 d were higher for male than for female calves (P < 0.05), and for calves from Continental dams than for those from British dams (P < 0.05). Average daily gain during backgrounding was higher for CH than for PM-sired calves (P < 0.05). Also, ADG in feedlot (backgrounding + fattening) was higher for male than for female calves (P < 0.05). Slaughter weight and dressing percentage were higher in calves from Continental dams than in those from British dams (P < 0.05). At similar backfat thickness, slaughter weight was higher in male than in female calves (P < 0.05). Total plasma cholesterol, HDL cholesterol and triglycerides were higher in PM sired cattle than in those sired by CH (P < 0.01 to 0.10). Similarly, cattle from British dams presented higher values of plasma cholesterol, HDL cholesterol and LDL cholesterol than cattle from Continental dams (P < 0.01 to 0.05). Insulin and IGF-I values increased with age (P < 0.01). Plasma insulin concentrations during fattening were higher for PM than for BB or CH sired cattle (P < 0.05), for cattle from Continental than from British dams (P < 0.01) and for males than for females (P < 0.01). During fattening, IGF-I values were higher in male than in female cattle (P < 0.01). The use of double-muscled sires in terminal crosses resulted in little effect on performance of the progeny. Key words: Double-muscled, terminal crosses, Belgian Blue, Piedmontese

The purpose of this study was to assess the quality of meat from 84 calves born from British (50% Hereford and 50% Red Angus) and Continental (50% Simmental and 50% Maine Anjou) dams inseminated with semen from normal (Charolais) or double-muscled (Piedmontese, Belgian Blue) sires. Lean composition of Belgian Blue and Piedmontese sired cattle had less intramuscular fat and more protein than Charolais sired cattle (P < 0.01 to 0.05). Breed of sire, origin of dam or calf sex had no effect on longissimus ultimate pH, thawing and cooking losses, shear forces, tenderness and overall flavour. However, meat from male progeny displayed higher drip loss (P < 0.05) and meat colour of male calves born from British dams was slightly more saturated than that of male calves born from Continental dams (P < 0.02). There were no other single effects of parental traits on meat quality. Significant interactions on total and soluble collagen content involving parental traits together with the single sex effect of the progeny (P < 0.05) did not induce textural differences, but meat from male progeny and that from Continental dams crossed with Belgian Blue sires was more juicy (P < 0.05). The use of DM bulls in terminal crosses resulted in increased lean yield and less marbling of the meat of the progeny but did not exert any other important effect on meat quality. Key words: Beef, double-muscling, meat quality

Metabolizable energy (ME), net energy for maintenance and net energy for growth of grass silages were evaluated by the comparative slaughter technique using a 2 × 2 × 3 factorial design. Sixty medium frame beef steers (259 ± 29 kg BW) were divided in groups of five and fed during 3 months either Timothy (T) or Bromegrass (B) harvested at stem elongation (S) of the first cut or at boot stage of the aftermath (A). Forages were fed at one of three levels of intake: ad libitum (FF), 80% of FF, or 65% of FF. Silages averaged 26.9% DM, 16.0% CP and 37.7% ADF. Regression of logarithm of heat production (HE) against ME intake were similar for all silages (log HE = 0.00046*ME + 2.4923; r2 = 0.89). From this equation, fasting HE of 311 kJ kg−0.75 d−1, ME for maintenance of 559 kJ kg−0.75 d−1 and efficiency of utilization of energy for maintenance of 56% were determined. Regression of ME intake against retained energy (RE) were similar for all silages. Efficiency of ME utilization for growth was 33% using the regression of ME over RE with a ME requirement for maintenance fixed at 559 kJ kg−0.75 d−1. Net energy for maintenance and growth were similar for all silages, averaging 6.17 and 3.70 MJ kg−1, respectively. The use of a prediction equation based on ADF of forages underestimated ME values of silages by approximately 25%. Moreover, NRC (1984) equations that estimate NE from experimentally estimated ME values tended to overestimate the net energy of our grass silages. Key words: Net energy, grass silages, timothy, bromegrass, beef cattle

An intensive mechanical conditioning treatment, referred to as maceration, was applied at mowing to alfalfa or timothy in order to enhance drying rate, reduce wilting time and possibly reduce respiration losses and proteolysis. In 1995, a laboratory trial was conducted using two levels of force (1750 and 3500 Newton) and five levels of conditioning: a control (no conditioning), one passage, three passages, five passages and seven passages through two steel knurled rolls. All forages were dried in a controlled environment at 30 °C and conserved as hay. The level of force did not affect the chemical composition of the forages obtained. However the nitrogen (N) fractions were affected by the level of maceration. As the level of conditioning increased, the soluble N fractions (A and B1) of both forages decreased (P < 0.001). Meanwhile, the slowly degradable N fraction (B3) increased linearly (P < 0.001) in timothy and quadratically (P < 0.003) in alfalfa. The fraction of unavailable N (fraction C) also increased linearly (P < 0.01) with intensity of maceration. In 1996, alfalfa was conditioned in the field at four intensity levels: a control (rubber roll-conditioning), one passage, two passages, and three passages through a full-size mower-macerator with three knurled rolls. The alfalfa dried under poor climatic conditions with alternating rain and sunshine and was conserved as silage at 30% dry matter (DM) after a 40-h wilt or as hay after a 90-h wilt. Neutral detergent fibre (NDF), acid detergent fibre (ADF), and ash contents increased linearly (P < 0.001) with the level of maceration; the increase was greater in hay than in silage. The non protein nitrogen (fraction A) decreased (P < 0.001) while fraction B3 and unavailable N (fraction C) increased (P < 0.001) with level of maceration. The results suggest that maceration decreases the extent of proteolysis during conservation and preserves a higher proportion of the slowly degradable N (escape nitrogen). Key words: Forage, maceration, chemical composition, nitrogen fractions

Forty Holstein bull calves (73.6 ± 6.3 kg) were used in a randomized complete block design to determine if varying the corn-to-barley ratio in the diet affects growth, diet digestibility and carcass quality of grain-fed veal calves. Five diets consisting of corn:barley ratios of 100:0, 75:25, 50:50, 25:75, 0:100 were offered along with a protein supplement (43.6% CP). Grain-to-protein supplement ratios were 2:1, 3.5:1 and 5:1 for the starting, growing and finishing phases, resulting in diets of 23.5, 20.3, and 18.7% CP, respectively. Incidence of diarrhea increased with an increase in dietary barley (P < 0.05). Apparent digestibility of diets decreased as the proportion of barley increased (P < 0.01). Throughout the experiment, DMI was the highest for diets containing 75% barley and the lowest for those containing 100% corn (P < 0.01). Average daily gains behaved in a quadratic manner during the starting phase only (P < 0.01). This effect became linear during the growing and finishing phases, with ADG decreasing as dietary barley increased (P < 0.01). Average feed to gain ratio increased linearly with dietary barley content (P < 0.01). Hot carcass weights and yields decreased linearly with increasing proportions of barley (P < 0.01). Carcass color was not affected by treatments. Carcass classification tended to decrease as dietary barley increased. The results indicate that compared with barley, the use of corn improves performance and diet digestibility of grain-fed veal. Key words: Veal calves, corn, barley, starch digestion, carcass quality

Forty-eight lambs (29.0 ± 4.7 kg BW) were used to study the effects of protein supplementation of forages on performance and diet digestibility. Lambs were fed grass hay or silage ad libitum plus a daily supplement of either: C, a control supplement supplying 1.2 g kg−1 BW of dry molasses and 0.6 g kg−1 BW of minerals, vitamins and lasalocid; CM, control supplement + 5.48 g kg−1 BW of canola meal; or FM, control supplement + 3 g kg−1 BW of fish meal. Apparent digestibility of all dietary components was higher in lambs fed silage than in those fed hay (P < 0.04). Addition of CM or FM improved apparent digestibility of energy and crude protein (CP) of lambs fed hay (P < 0.02) and CP digestibility of lambs fed silage (P < 0.01). Apparent digestibility of CP was higher in lambs fed FM than in those fed CM with either hay or silage (P < 0.03). Addition of CM or FM tended to decrease ADF digestibility of silage-based diets (P < 0.06). Apparent ADF digestibility of hay-based diets was lower in lambs fed CM than in those fed FM (P < 0.02). Forage DM intake was similar for all treatments. Addition of CM or FM to the diets improved average daily gains by 24% (P < 0.03), an effect that was higher with hay (35.1%, P < 0.02). Feed efficiency was 23.6% better in lambs fed protein-supplemented hay than in those receiving C (P < 0.04). Neither dressing percentage nor carcass lean yield was affected by protein supplementation. Digestible DM and TDN intakes were higher in lambs fed silage (P < 0.03) as a result of higher apparent digestibility for silage than hay. Furthermore, CM increased TDN intake by 7.6 and 8.2% in lambs fed hay and silage, respectively, compared with lambs fed FM. Addition of canola and fish meals improved forage nutritive value for lambs. Key words: Canola meal, fish meal, forages, digestibility, lambs, growth

Thirty-three lambs (25.2 ± 2.7 kg body weight) were used to determine if mechanical treatment of canola seed could improve the performance of growing lambs and diet digestibility. All lambs received a basal diet of 179 g d−1 of a 16% crude protein (CP) commercial concentrate and grass silage fed ad libitum. The basal diet was supplemented with the following dietary treatments (dry matter basis): C, a control supplement supplying 182 g of a mixture of 66% canola meal and 34% canola oil; WCS, 187 g of whole canola seeds; RCS, 188 g of rolled canola seeds; and GCS, 189 g of ground canola seeds. Dry matter intake was similar for all diets. Average daily gain (ADG) was 20% lower (P < 0.001) for lambs fed whole or crushed canola seeds than for those fed the C diet. Lambs fed GCS had intermediate ADG between those fed C and those fed WCS and RCS diets. In general, apparent digestibility of C was higher (P < 0.01) than that of WCS and RCS and digestibility of GCS was intermediate. Rumen pH and molar proportions of individual volatile fatty acids (VFA) were not affected by treatments. Rumen ammonia-N concentration was similar among treatments. Utilization of whole canola seeds as a protein and energy supplement to grass silage resulted in lower performance of lambs compared to that obtained with a mixture of canola meal and canola oil. Key words: Canola seeds, silage, lamb growth

Ten Holstein cows in early lactation were used in a replicated 5 × 5 Latin square design to study the effects of MgO and three buffers added to diets containing Ca salts of canola oil fatty acids. Treatments were 1) control (basal diet; no buffer), 2) 1.1% NaHCO3 plus 1.1% KHCO3, 3) 1.9% NaHCO3,4) 0.5% MgO, and 5) 2.0% Na sesquicarbonate (percentage of dry matter). The control diet contained 53% grass silage, 43% concentrate, and 4% Ca salts. Body weight, intake, milk yield, and percentages of milk fat, protein, and lactose were unaffected by treatments. Buffers and MgO tended to increase triacylglycerol extraction by the mammary gland and changed the proportions of some fatty acids in milk. Arterial concentrations of acetate and triacylglycerol were correlated with their respective arteriovenous differences. Extraction by the mammary gland was high for acetate (≈58.2%), triacylglycerol (≈47.3%), propionate (≈34.6%), and glucose (≈24.3%). Extraction of free fatty acids, phospholipids, or cholesterol was negligible. Mammary triacylglycerol arteriovenous difference tended to be higher when MgO was fed than when NaHCO3 was fed. Sodium sesquicarbonate, NaHCO3, and the blend of bicarbonate buffers increased C18:2 in milk fat when compared with the control treatment. The concentration of C18:2 in milk fat decreased when MgO was fed, but the ratio of cis-C18:1 to trans-C18:1 increased compared with effects of dietary NaHCO3. Medium-chain fatty acids in milk fat tended to be higher with Na sesquicarbonate than with NaHCO3. Buffers and MgO modified the profiles of fatty acids in milk.

Thirty-three lambs (25.2 ± 2.7 kg BW) were used to study if mechanical treatment of canola seeds can exert an effect on carcass quality, blood lipids, and fatty acid profile of depot fat. All lambs received a basal diet of 179 g d−1 of a 16% CP commercial concentrate and grass silage fed ad libitum. The basal diet was supplemented with the following dietary treatments (dry matter basis): C, a control supplement supplying 182 g of a mixture of 66% canola meal and 34% canola oil; WCS, 187 g of whole canola seeds; RCS, 188 g of rolled canola seeds; and GCS, 189 g of ground canola seeds. Dressing percentage was higher (P < 0.05) for diet C (45.6%) than for WCS (42.5%) and RCS (41.9%). The highest and lowest carcass grades were obtained with diets C and RCS, respectively (P < 0.05). Blood lipid concentrations increased as the lambs grew older (P < 0.01). Lambs fed the GCS diet had lower plasma concentrations of total cholesterol and high density lipoprotein cholesterol than lambs fed the WCS or RCS diets (P < 0.05). Kidney fat of lambs on the C diet contained more trans -C18:1 and less C18:0 compared with the other diets (P < 0.01). The utilization of untreated or rolled canola seeds as protein and fat supplements decreased carcass quality, increased blood triglycerides and changed fatty acid composition of depot fat. Key words: Canola seeds, lambs, carcass composition, blood lipid

The in situ dry matter disappearance technique (Ørskov and McDonald, 1979) evaluates forages for their rate and extent of degradation in the rumen. However, this method does not allow the evaluation of a large number of samples at one and the same time and therefore which limits screening of treatments applied to forages. The in vitro gas production method is faster and allows handling of many samples per batch; therefore, gas production could be an alternative to the use of nylon bags if the response to treatments between the two methods is similar among treated forages. The objective of this experiment was to compare results obtained with both the gas production and the nylon bag techniques for forages treated with four levels of maceration and conserved as hay or silage.

Twenty-eight lambs (23.4 ± 4.7 kg BW, 59 days old) were used to compare fish meal to canola and heat-treated canola meals as protein supplements to grass silage and their effects on the performance and apparent digestibility of diets. Silage was fed ad libitum, assuring 20% orts. In addition to silage, lambs received daily a fixed quantity of one of four supplements: C, a control supplement supplying 6.78 g kg−1 BW of a commercial diet (73.5% barley, 14.7% dry molasses and 11.8% minerals, vitamins and Bovatec); CM, control supplement + 8.05 g kg−1 BW of canola meal; HCM, control supplement + 7.52 g kg−1 BW of heated-canola meal (105 min at 150°C) and FM, control supplement + 4.0 g kg−1 BW of fish meal. Heating decreased the effective degradability of canola meal protein from 78.5% to 19.8%. Silage dry matter (DM) intake was not affected by protein supplementation. Supplementation with CM and FM improved the average daily gains (ADG) by 60.2% and 49.7%, respectively, when compared to lambs that were fed with C diet (P < 0.01). Heated CM had little effect on ADG (233 and 191 g for HCM and C, respectively; P > 0.10). Feed efficiency was 32.4% higher in lambs fed with CM and FM than in those receiving the C and HCM treatments (P < 0.05). Carcass yield and classification were not affected by the treatments. Fish meal supplementation did not affect the apparent digestibility of the diets, but CM and HCM decreased the digestibility of DM, neutral detergent fiber (NDF) and acid detergent fiber (ADF) (P < 0.05). The heating of canola meal resulted in decreased apparent digestibility of DM, energy, protein and NDF (P < 0.05) when compared to lambs fed with CM. Nutritive value (intake × digestibility) of the diets was lower for lambs fed with HCM than for those fed with CM and FM. Protein supplementation improved the efficiency of ME utilization for growth when compared to lambs fed with C diet. Canola meal was as good as fish meal as a protein supplement for lambs fed with high-silage diets. The heat-treatment applied to canola meal resulted in a decrease in protein availability, thus decreasing its nutritive value.

Two experiments were conducted to determine the effects of supplementing grass silage (S) with isonitrogenous amounts of fish meal (FM; 380 g head−1 d−1) or fish protein hydrolysate (FPH; 300 g head−1 d−1) on growth, diet digestibility and rumen fermentation in beef cattle. In the first experiment, 36 crossbred steers were used in a 112 d growth trial to determine treatment effects on dry matter intake (DMI), average daily gains (ADG) and feed to gain ratio. Protein supplementation did not affect silage DMI, but increased ADG by 18% (P < 0.01) and feed to gain ratio by 6% (P < 0.08). The increase in ADG with FM was 12% higher than that obtained with FPH (P < 0.01). In a second experiment, six rumen fistulated heifers were used in a double 3 × 3 Latin square to study treatment effects on apparent digestibility and rumen fermentation. Protein supplementation increased apparent DM and N digestibility when compared to the S treatment (P < 0.04). Apparent ADF digestibility was 3.0% higher in heifers fed FM than in those fed FPH (P < 0.05). Rumen pH decreased immediately after feeding (P < 0.001), but was not affected by the treatments. Total volatile fatty acids (VFA) concentrations were not significantly affected by supplementation but by time; they were higher for the FM than for the FPH diet at all times (P < 0.02). Acetate propionate ratio was lower in heifers fed silage alone (P < 0.02). Rumen NH3N levels during the first 4 h after feeding were higher in animals receiving protein supplements (P < 0.001). From 0 to 2 h after feeding, rumen free α-amino-N increased almost twice as high in heifers fed FM than in those fed FPH (P < 0.05); however, at 4 and 6 h post feeding, the situation reversed. Plasma urea N was lower in animals fed only silage (P < 0.01). Total essential amino acids were higher in animals receiving protein supplementation than in those fed silage alone (P < 0.03) and tended to be higher in heifers fed FM than in those fed FPH (P < 0.08).

Eight mature wethers fitted with rumen cannulae were used in a double 4 × 4 Latin square feeding trial to study the effect of dietary alkalis on digestive physiology of sheep fed a high-barley diet. The treatments were: C = control diet composed of 17% alfalfa meal and 83% concentrate, on as-fed basis; CA = control plus 1% Ca(OH) 2 ; MG = control plus 0.79% Mg(OH) 2 ; CAMG = control plus 0.5% Ca(OH) 2 and 0.39% Mg(OH) 2 . Dry matter intake averaged 1.91, 2.54, 2.79, and 2.72% of BW for diets C, CA, MG and CAMG, respectively (P < 0.01). Digestible DM intake was also affected by the treatments and averaged 0.97, 1.26, 1.35 and 1.37 kg d −1 for C, CA, MG, and CAMG diets, respectively (P < 0.01). Apparent DM digestibility was higher in sheep fed the C diet than in those fed the other diets (P < 0.03) and it was inversely related to intake (P < 0.01). Total VFA concentration was lower in sheep fed C than in those fed the hydroxides (P < 0.01). Proportions of individual VFA were not altered by the diet except for isobutyrate which was higher in sheep fed the C diet (P < 0.01). Rumen NH 3 -N concentration was lower in sheep fed the hydroxide-containing diets than in animals fed the control diet (P < 0.01). Plasma urea nitrogen was lower for the C diet (P < 0.01). Plasma glucose tended to be lower for the C diet than for the other diets (P < 0.06). The control diet induced a mild form of systemic acidosis as indicated by the decrease in blood pH, HCO 3 − and base excess (P < 0.01). Addition of Ca(OH) 2 and Mg(OH) 2 to the diet, alone or in combination, improved the systemic acid-base status of sheep and was associated with increased DM intake. Key words: Hydroxides, acid-base balance, rumen fermentation, sheep

Twenty-four castrated lambs (32.4 ± 4.1 kg BW) were used to study the effect of varying dietary cation–anion concentration [C–A] on performance and acid–base balance. The diets contained approximately 100, 300, 500 and 700 mequiv Na + K − Cl kg−1 of feed. Each group of six lambs was fed one of the diets ad libitum during a 6-wk test. Increasing the [C–A] of the diets resulted in higher feed intake and higher daily gains (P < 0.01) without affecting feed efficiency. Apparent digestibility of nutrients was not affected by the dietary treatments but a negative relationship was found between intake and energy digestibility (P < 0.01). Blood pH was lower in lambs receiving the 100 [C–A] diet (P < 0.05). Blood bicarbonate and base excess increased as [C–A] in the diet increased from 300 to 700 mequiv (P < 0.05). Plasma Mg concentration decreased with increasing dietary [C–A] (P < 0.01). Urinary pH and urine volume increased as [C–A] in the diet increased (P < 0.01). The results indicate that diets containing between 500 and 700 mequiv Na + K − Cl kg−1 stimulated growth by allowing greater feed intake and greater daily gains with little effect on nutrient digestibility. Blood profile showed a systemic response to dietary changes in [C–A], but indicated that lambs were able to adapt to cation loads since the values obtained for acid–base balance were within physiological range for lambs. Key words: Cation–anion, acid–base, lambs

Nine DLS rumen-cannulated wethers (69 kg avg BW) were used to study the effects of dietary supplementation with two types of fermented, ammoniated, condensed whey permeate on performance, rumen physiology and acid-base status in sheep fed high-grain diets. Sheep were fed three isonitrogenous (16% CP) diets according to a triple 3 × 3 Latin square design, with three 21-d periods each. One whey permeate contained ammonium lactate (AL) while the other contained ammonium propionate (AP). Urea was used as a source of NPN in the control diet (C). Diets, offered ad libitum, contained 78% barley and 18% dehydrated alfalfa meal. Dry matter and digestible energy intakes were about 15% higher for diets AL and AP than for diet C (P < 0.05). Dry matter digestibility was not affected by the treatments, whereas organic matter and energy digestibilities tended to be higher for diet AP than for diet AL (P < 0.07). Rumen fermentation was not affected by the treatments. Over a 4-h post-feeding period, sheep fed diet C had higher plasma concentrations of lactate (P < 0.06) and acetate (P < 0.04) but lower levels of plasma propionate (P < 0.06) than sheep fed the AL and AP diets. Plasma propionate 2 h after feeding was higher in sheep fed the AL diet versus the AP diet (P < 0.01). Sheep blood was mildly alkalotic despite the fact that sheep were fed a high-grain diet. The two types of fermented, ammoniated and condensed whey permeate were found to be good sources of NPN. Key words: Whey, rumen fermentation, acid-base balance, sheep

Eight wethers (40 to 60 kg), each fitted with a ruminal fistula and a reentrant cannula in the proximal duodenum, were used in a partially balanced incomplete block design with 2 x 2 factorial arrangement of treatments and periods to study. effects of forage conservation (silage vs. hay) and protein supplementation (none vs. fish meal) on ruminal and total digestion of nitrogen (N), and on flow of nutrients into duodenum of sheep. Total essential and nonessential amino acids in forage decreased by 36 and 44% during ensiling, respectively. A greater (P < 0.05) amount of total-N and amino acids entered the small intestine of sheep fed hay compared with silage. The duodenal flow of total-N and amino acids increased (P < 0.01) due to fish meal supplementation. Microbial-N yield did not differ (P > 0.10) among treatments. Apparent digestion of N in stomach and the total digestive tract was greater (P < 0.01) for silage than for hay. Fish meal supplementation did not affect (P > 0.05) the proportion of N apparently digested in the stomach, but increased (P < 0.01) apparent N digestion in the total digestive tract. Our results suggest that utilization of N in hay is superior to that in silage, probably because of decreased N loss in the rumen, a greater amount of amino acids and N reaching the duodenum and increased apparent absorption of N in the intestinal tract. Fish meal supplementation also increased N utilization, and the effect was greater for silage than for hay.

Field and animal feeding experiments were conducted in 1989 at the Station agronomique de l'Université Laval near Québec City to compare quackgrass (Elytrigia repens (L.) Nevski.) with timothy (Phleum pratense L.) hay in terms of forage quality, productivity and feeding value. Timothy stands infested with 0, 50 or 100% quackgrass were cut at early heading and fed to Charolais × Simmental growing heifers. Quackgrass forage contained more (P < 0.05) crude protein (CP), and less neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) than timothy. The timothy-quackgrass mixture had a greater CP concentration, and similar NDF, ADF and ADL concentrations compared with timothy. Mineral composition, as measured by calcium (Ca), phosphorus (P) and magnesium (Mg), did not differ among forages. Quackgrass and the timothy-quackgrass stands yielded more dry matter than timothy stands. Feed conversion ratio tended to be better for timothy (8.5) than for quackgrass (9.2) and quackgrass-infested timothy (9.3). Animal yield from quackgrass (309 kg gain ha−1) exceeded that from timothy (237 kg gain ha−1). Animal yield did not differ between timothy and quackgrass-infested timothy. Quackgrass may not be considered as a weed in timothy forage destined for beef cattle production, as long as it does not interfere with cropping sequence or spread to cultivated cropland.