Mcal Kg-1 Research Articles

Características agronómicas y calidad del maíz forrajero con riego sub-superficial

Subsurface drip irrigation (SDI) saves water and increases yields in forage maize production in comparison to furrow gravity irrigation (FGI). An evaluation was done of the effect of SDI with three different dripline spacings and FGI on selected agronomic characteristics and forage quality maize (Zea mays L., var. AS900). The study was done in the 2003 spring-summer growing season in the State of Coahuila, Mexico. The experimental plot was 4-00-00 ha, with 2-00-00 used for SDI and 2-00-00 for FGI. Three SDI treatments (80, 90 and 100 cm dripline spacing) and one FGI treatment (control) were distributed following a randomized block design with four replicates. Recorded agronomic variables were: yield (dry and fresh), plant height, tiller production, prolific plants, and stem lodging. Recorded forage quality variables were: acid detergent fiber (ADF), neutral detergent fiber (NDF), crude protein (CP), and net energy for lactation (NEL). The 80 cm had optimum agronomic performance (dry yield = 20.52 t ha-1, plant height = 2.97 m, tiller production = 16.25 %, prolific plants = 15.0 %), and the highest overall forage quality (CP = 10 %, ADF = 28.56 %, NDF = 54.41 %, NEL = 1.22 Mcal kg-1, TDN = 59.71 %). All three SDI treatments resulted in water savings (27.5 %) and higher yields (up to 160 %) versus the FGI treatment.

Effects of feeding wheat straw and middlings ensiled with whey on digestibility and growth of cattle

Two studies were conducted with the objective of evaluating the effects of feeding different levels of whey ensiled with wheat straw and wheat middlings (whey silage) compared to control diets on production parameters in growing cattle. Whey silage was included in diets at 55 and 65.5% on a dry matter basis with net energy for maintenance and crude protein calculated to be similar to control diets containing a combination of alfalfa hay, corn silage and wheat middlings at 1.74 Mcal kg-1 and 13.4%, respectively. Dry matter intake averaged 8.41 versus 8.91 kg d-1 (P < 0.05) and 8.68 versus 7.09 kg d-1 (P < 0.05) when whey silage was included at either 55 or 65.5% of the diets compared to the control diets. Average daily gains of cattle fed whey silage incorporated at 55% was 1.00 versus 1.14 kg d-1 (P < 0.05), and reflected the difference in dry matter intake; no differences (P > 0.05) in feed efficiency (8.73:1 versus 8.71:1) were observed. However, the higher dry matter intake (DMI) of cattle fed diets with whey silage incorporated at 65.5% did not (P > 0.05) translate into higher average daily gain (1.23 versus 1.18 kg d-1), resulting in a higher (P < 0.05) feed to gain (7.00:1 versus 6.01:1) for the whey-based silage diets. Incorporation of whey silage in diets at 55% increased (P > 0.05) the dry matter digestibility by 12%, whereas incorporation at 65.5% decreased (P < 0.05) dry matter digestibility by 12% compared to control diets, with no differences (P > 0.05) in percent neutral detergent fiber digestibility (NDFD) at either level. We conclude that whey silage can be included at between 55 and 65.5% of the total dry matter in diets with no adverse effects on production compared to cattle fed diets containing a combination of alfalfa hay, corn silage and wheat middlings. Key words: Agricultural by products, crop residues, digestibility, growing cattle, production, whey silage

Effect of dietary soybean or sunflower seeds on milk production, milk fatty acid profile and yield of conjugated linoleic acid

Eight cows in mid-lactation were used to determine the effects of feeding diets containing soybeans (SBS) or sunflower seed (SFS) on conjugated linoleic acid (CLA) yield and concentration in milk during two 3-wk periods. All cows were fed a standard pre-trial diet for 2 wk, before assignment to treatment diets in both periods of the 2 × 2 cross-over design used in the study. The two treatment diets contained on a dry matter (DM) basis: (1) SBS: 20% barley silage, 34.7% barley grain, 30% alfalfa cube, 13% crushed soybean seed and 0.36% sunflower oil, and (2) SFS: 17% barley silage, 34.6% barley grain, 40% sunflower seed incorporated into alfalfa cubes (cubes comprised 18% whole sunflower seed and 82% alfalfa hay), and 6.5% heat-treated soybean meal. The ingredients in the two diets were adjusted so that they would provide similar levels of energy (1.5 MCal kg-1) and have similar nutrient composition with regard to protein (16.7%), ether extract (5.2%) and fibre components (41%). Milk samples were collected, on 2 d prior to initiation of treatment diets and on days 6, 7, 13, 1 4, 20 and 21 of each experimental period. Cholecystokinin and insulin concentrations in blood samples collected at the start and end of each experimental period indicated no significant differences. Dry matter and net energy intake of cows fed the SBS and SFS were 23.3 and 21.4 ± 0.9 kg d-1; 34.4 and 31.6 ± 1.4 Mcal d-1, respectively, and in vitro volatile fatty acid concentration after 24 h of incubation was 123.3 and 114.7 ± 1.3 mM, respectively, and lower (P < 0.05) for the SFS diet. Milk, milk fat, protein and lactose yields from cows fed the SBS and SFS diets were similar (32.9 and 32.0 ± 2.4; 1.10 and 0.97 ± 0.07; 1.05 and 1.00 ± 0.05; 1.46 and 1.39 ± 0.12, respectively), but the CLA cis-9, trans-11 concentrations in the milk from cows fed the SBS and SFS diets were 4.05 and 7.28 mg g-1 of lipid and resulted in 66% higher (P < 0.01) CLA yield (g d-1) in milk for cows fed the SFS diet. This study confirmed that feeding sunflower seeds as a component of a hay cube increased CLA yield in the milk of dairy cows without affecting yields of other milk components. Key words: Dairy cows, sunflower, soybeans, milk production, conjugated linoleic acid

Effect of variety and maturity stage on chemical composition, carbohydrate and protein subfractions, in vitro rumen degradability and energy values of timothy and alfalfa

The objective of this study was to investigate the effects of forage variety and stage of maturity on chemical composition, protein and carbohydrate subfractions, in vitro rumen degradability and energy content under the climatic conditions of western Canada. Two varieties of alfalfa (Medicago sativa L. cvs. Pioneer and Beaver) and timothy (Phleum pratense L. cvs. Climax and Joliette), grown at three locations in Saskatchewan (Canada), were cut at three stages [1 = 1 wk before commercial cut (early bud for alfalfa; joint for timothy); 2 = at commercial cut (late bud for alfalfa; pre-bloom head for timothy); and 3 = one week after commercial cut (early bloom for alfalfa; full head for timothy)]. The results showed that: (1) the varieties had minimal effects on nutritional value; however, (2) stage of cutting had a large impact on chemical composition, protein and carbohydrate fractions, in vitro rumen degradability and energy value. As plant maturity advanced from stage 1 to 3, the following changes were noticed: (a) CP was decreased [alfalfa: 20.2 to 17.6; timothy: 11.1 to 7.9% dry matter (DM)]; fibre was affected very little in alfalfa but increased in timothy [acid detergent fibre (ADF): 38.0 to 40.7; neutral detergent fibre (NDF): 68.7 to 72.8% DM]; lignin and neutral detergent insoluble protein (NDIP) were not affected in either forage; acid detergent insoluble protein (ADIP) was increased in alfalfa (3.5 to 17.1% CP), but no effect was seen in timothy; (b) the rapidly degradable protein fraction (PA) was reduced in alfalfa (51.2 to 34.8% CP) but increased in timothy (9.2 to 27.5% CP); the rapidly degradable fraction (PB1) increased in alfalfa (0.0 to 25.2% CP), but decreased in timothy (31.6 to 16.7%); the intermediate degradable fraction (PB2) decreased in both forages (alfalfa: 14.1 to 5.2; timothy: 37.8 to 29.4% CP); the slowly degradable fraction (PB3) declined in alfalfa (33.1 to 17.7% CP), but was not affected in timothy (averaging 21.3% CP); the unavailable fraction (PC) associated with the cell wall increased in alfalfa (3.5 to 17.1% CP), but did not change in timothy (averaging 5.2% CP); (c) in vitro rumen degradabilities of DM (IVDMD) and NDF (IVNDFD) increased at stage 2 and then declined at stage 3. The highest IVDMD and IVNDFD after a 48-h incubation were at cutting stage 2 (50.5 and 37.3%; 42.8 and 37.3% for alfalfa and timothy, respectively); (d) the energy content behaved in a quadratic fashion; it increased initially and then decreased with the highest energy contents at stage 2 for both forages (TDN1x, DE1x, DEp, MEp, NELp: 63.8% DM, 2.92, 2.68, 2.26, 1.40 Mcal kg-1 DM for alfalfa; 45.3% DM, 2.03, 1.86, 1.43, 0.82 Mcal kg-1 DM for timothy, respectively). In general, the best cutting was found at stage 2, which was late-bud for alfalfa varieties and pre-bloom head for timothy. Key words: Alfalfa, timothy, variety, maturity, nutritive value

Effect of dietary particle size and nutrient supply on energy digestibility and nitrogen excretion in ileal cannulated grower pigs

Diets with two particle sizes (600 and 900 µm) and two nutrient supply levels [digestible energy (DE)-limiting and amino acid (AA)-limiting; 2.8 and 1.8 g digestible lysine Mcal-1 DE, 3.15 and 3.40 Mcal DE kg-1, respectively] were used. Eight ileal cannulated pigs (25 ± 2 kg) had restricted access to feed (3 × maintenance DE) for three periods (N = 6 per diet). Reducing particle size from 900 to 600 µm did not alter urinary or total N excretion (P > 0.10), reduced faecal N excretion 11%, increased total-tract digestibility of N and energy 3%, and increased ileal digestibility of N 9% and energy 11% (P < 0.05). Reducing particle size increased energy digestibility but did not reduce total N excretion. Key words: Particle size, pig, nitrogen, excretion, energy, digestibility

Polyethylene Glycol Affects Goats' Feeding Behavior in a Tannin-Rich Environment

High concentrations of condensed tannins in browse impair brush clearing by goats. We studied the effect of polyethylene glycol (PEG, MW 4000), a polymer that binds condensed tannins, on the feeding behavior of Damascus goats (Capra hircas) on a range dominated by tannin-rich lentisk (Pistacia lentiscus L.). This was done with or without a nutritious alternative to browse (alfalfa hay) available at pasture. In phase 1, no hay was provided to goats; in phase 2, hay was distributed daily in the field. In both phases, 6 goats had free access to PEG while at pasture, while 6 goats that grazed separately on another paddock did not. All goats received each night an allowance of concentrate (400 g day-1 of 40% ground corn grain, 40% ground barley, 17% soybean meal and 3% of a mineral-vitamin premix, and contained as fed 16% crude protein (CP) and 2.66 Mcal kg-1 of Metabolizable Energy). The 2 groups of goats alternated daily between paddocks. Goats supplemented with PEG spent more time browsing lentisk than goats in the control group (73 and 41%, respectively, P < 0.0001). Goats in the control group spent more time foraging on dry grasses than their PEG-fed counterparts (28 and 12%, respectively, P < 0.0001). Goats from the PEG group gained body weight at a higher rate than controls. The daily intake of PEG was 450 g, with an intake rate of 1.2 g sec-1. Supplemental alfalfa hay substituted partly for dry grasses in goats' diets, but did not modify the percent of time goats in either treatment spent browsing lentisk. Our data suggest that PEG has the potential to increase intake of tannin-rich species, even where alternative fodder of better nutritional quality is present. However, self-feeding of PEG may not be the best way to provide PEG because goats may ingest more PEG than needed to annul the aversive effects of tannins on food intake. DOI:10.2458/azu_jrm_v55i6_landau

Polyethylene glycol affects goats' feeding behavior in a tannin-rich environment

High concentrations of condensed tannins in browse impair brush clearing by goats. We studied the effect of polyethylene glycol (PEG, MW 4000), a polymer that binds condensed tannins, on the feeding behavior of Damascus goats (Capra hircas) on a range dominated by tannin-rich lentisk (Pistacia lentiscus L.). This was done with or without a nutritious alternative to browse (alfalfa hay) available at pasture. In phase 1, no hay was provided to goats; in phase 2, hay was distributed daily in the field. In both phases, 6 goats had free access to PEG while at pasture, while 6 goats that grazed separately on another paddock did not. All goats received each night an allowance of concentrate (400 g day-1 of 40% ground corn grain, 40% ground barley, 17% soybean meal and 3% of a mineral-vitamin premix, and contained as fed 16% crude protein (CP) and 2.66 Mcal kg-1 of Metabolizable Energy). The 2 groups of goats alternated daily between paddocks. Goats supplemented with PEG spent more time browsing lentisk than goats in the control group (73 and 41%, respectively, P &lt; 0.0001). Goats in the control group spent more time foraging on dry grasses than their PEG-fed counterparts (28 and 12%, respectively, P &lt; 0.0001). Goats from the PEG group gained body weight at a higher rate than controls. The daily intake of PEG was 450 g, with an intake rate of 1.2 g sec-1. Supplemental alfalfa hay substituted partly for dry grasses in goats' diets, but did not modify the percent of time goats in either treatment spent browsing lentisk. Our data suggest that PEG has the potential to increase intake of tannin-rich species, even where alternative fodder of better nutritional quality is present. However, self-feeding of PEG may not be the best way to provide PEG because goats may ingest more PEG than needed to annul the aversive effects of tannins on food intake.

Effect of protein and energy in the diet of the early-weaned calf on the concentration of free amino acids in the blood plasma

Three experiments were conducted with 108 male Friesian calves to determine the effect of protein and energy in the diet on the concentration of free amino acids in the plasma. In experiments 1 and 2, the diets contained 12 to 21 per cent crude protein, with urea or meat meal as the protein supplement. The diets were fed with and without sulphur supplementation. In experiment 3, the metabolizable energy content of the diets was changed from 2.2 to 1.8 Mcal kg-1 by the addition of 20 to 60 per cent roughage from lucerne meal or ground straw to the diets. Blood samples were collected from all calves at 11 weeks of age, and the concentration of free amino acids in the plasma was measured. As the protein content of the diets increased, the percentage of essential amino acids of the total amino acids in the plasma increased. The percentage of essential amino acids was also greater in the calves fed meat meal than in those fed urea. These changes were mainly due to increased concentrations of the branched chain amino acids and decreased concentrations of glycine and glutamic acid. The supplementation of the diets containing urea with sodium sulphate increased the concentrations of cystine and methionine in the plasma. As the metabolizable energy intake of the calves increased there was an increase in the concentration of total amino acids in the plasma. Hence, the effect of protein and energy in the diet must be considered in studying the concentration of amino acids in the plasma.