Variation in chemical composition and nutritional quality among barley cultivars for ruminants. 1. Steer finishing performance, diet digestibilities and carcass characteristics

Abstract

. 1998. Variation in chemical composition and nutritional quality among barley cultivars for ruminants. 1. Steer finishing performance, diet digestibilities and carcass characteristics. Can. J. Anim. Sci. 78: 369-375. Inherent variability in chemical composition and nutritional value exists among barley (Hordeum vulgare L.) cultivars due to year grown, head morphology, growth habit and intended end use. Two trials were conducted to identify causal factors for variability among barley cultivars in animal performance, carcass characteristics, diet digestibility and digestible energy (DE) content. In feedlot trials, 144 large-frame beef steers (380 ± 1.6 kg in Trial 1, 372 ± 0.8 kg in Trial 2) were assigned within three weight blocks, eight to a pen, in a randomized complete block design and pens to treatments. Steers were fed a diet of 83% steam-rolled barley (Andre, Camelot, Clark, Cougbar, Harrington or Steptoe for 123 d in Trial 1; Boyer, Camelot, Clark, Harrington, Hesk or Steptoe for 119 d in Trial 2), 10% silage (wheat in Trial 1, oat in Trial 2), and 7% supplement on a dry matter (DM) basis. In Trial 1, Cougbar neutral detergent fiber (NDF) digestibility was significantly lower than Clark. Digestibility of other nutrients tended to be lowest for steers fed Cougbar and as a result, diet DE was lower (P < 0.05) for Cougbar than for Clark and Camelot. Diet DE and NDF digestibility were correlated (r = 0.69; P < 0.0001). Lower nutrient utilization by steers fed Cougbar resulted in lower performance. In Trial 2, steers fed Hesk had a poorer (P < 0.05) ratio of feed to gain than steers fed Camelot and Harrington and lower (P < 0.05) digestibility than steers fed Steptoe. In summary, data from these trials suggest that Cougbar and Steptoe are of lower nutritional value than other cultivars under the conditions of these studies. In these studies, digestibility of NDF was a major factor contributing to differences among cultivars. , que ce soit dû à l'année de production, à la morphologie de l'épi, au type de croissance ou à l'utilisation prévue du grain. Deux essais en parc d'engraissement ont été réalisés pour identifier les facteurs en cause de cette variabilité, relativement aux performances zootechniques, aux caractères de carcasse, à la digestibilité de l'aliment et au contenu en ED. Centquarante-quatre bouvillons à viande de grand format (380 ± 1,6 kg dans l'essai 1 et 372 ± 0,8 kg dans l'essai 2) étaient répartis selon trois classes de poids entre les traitements à raison de 8 animaux par parquet selon un dispositif en blocs aléatoires complets. Les bouvillons recevaient un régime composé, en m.s., de 83 % d'orge aplatie à la vapeur, soit les cultivars Andre, Camelot, Clark, Cougbar, Harrington ou Steptoe pendant 123 j dans l'essai 1 et Boyer, Camelot, Clark, Harrington, Hest ou Steptoe pendant 119 j dans l'essai 2, de 10 % d'ensilage (blé dans l'essai 1, avoine dans l'essai 2) et de 7 % de complément. Dans l'essai 1, la digestibilité de la FDN de Cougbar était significativement inférieure à celle de Clark. ...

Variation in chemical composition and nutritional quality among barley cultivars for ruminants. 2. Digestion, ruminal characteristics and in situ disappearance kinetics

“…The calculated NE m and NE g contents averaged 6.8 and 4.3 MJ kg -1 OM in Trial 1, respectively, and 8.1 and 5.4 MJ kg -1 OM in Trial 2, respectively. These values are lower than those calculated from steer finishing performance (Ovenell-Roy et al 1998), possibly due to the low metabolizability (DE/ME) used in National Research Council (1984Council ( , 1996 publications, since Johnson (1972) observed larger ratios with high grain diets. Metabolizability of barley diets should be directly measured.…”

“…In the current study, digestibility of NDF varied 15 percentage units in Trial 1 and 13 percentage units in Trial 2. Simple correlation coefficients indicated that NDF digestibility was correlated with DE content of barley (r = 0.47; P < 0.01), as observed by Ovenell-Roy et al (1998). However, as composition of NDF is not constant, digestibilities of polymeric monosaccharides were measured to eliminate the impact of varying N, minerals and cuticle contents of NDF.…”

“…DISCUSSION Organic matter intake of steers differed among cultivars in Trial 1 but not Trial 2. In a companion finishing study (Ovenell-Roy et al 1998), steers fed Cougbar consumed less (P < 0.10) OM than those fed Clark or Steptoe, but those fed Clark consumed as well or better than those fed other cultivars. These results show variability from one trial to the next, but also suggest differences in rate of digestion among cultivars in Trial 1 but not in Trial 2.…”

“…In a companion steer finishing trial (Ovenell-Roy et al 1998), however, steers fed Hesk and Boyer digested less GE than those fed most spring cultivars due to low NDF digestibility, which was one of the major sources of variation in feeding value among barley cultivars. In the current study, digestibility of NDF varied 15 percentage units in Trial 1 and 13 percentage units in Trial 2.…”

“…In addition, cultivars can be covered or hull-less, have normal or waxy starch, or differ in plant height, disease resistance, and protein and amino acid content (Briggs 1978). This inherent variability leads to differences in animal performance (Hinman 1979;Boss and Bowman 1996;Ovenell-Roy et al 1998) and diet digestibility (Bradshaw et al 1992;Ovenell-Roy et al 1998).…”