Seasonal Variations in Voluntary Intake and Apparent Digestibility of Forages in Goats Grazing on Introduced Leymus chinensis Pasture
The nutrient composition of pasture, voluntary intake and digestibility of diet ingested by goats grazing on an introduced Leymus chinensis pasture were measured across spring (May), summer (July), autumn (October) and winter (March). In each season, 12 Inner Mongolian Cashmere goats (6 wethers and 6 does with an average live weight of 22.2±1.3 kg and 19.5±0.8 kg, respectively) were used to graze on a 2 hectares size paddock. Diet selection was observed and the plant parts selected by grazing goats and whole plant L. chinensis were sampled simultaneously. The alkane pair C32:C33 and C36 were used to estimate intake and digestibility, respectively. The results showed that the plant parts selected by goats had higher crude protein (CP) and lower acid detergent fiber (ADF) and neutral detergent fiber (NDF) than the whole plant, especially in the autumn and winter. The voluntary intake of dry matter (DM), CP, ADF, NDF, and metabolizable energy (ME) by goats was highest in summer (p<0.05). The goats ingested more CP, ME, and less ADF in spring than in autumn (p<0.05). The intakes of DM, CP, and ME were lowest in winter (p<0.05). There were significant differences in nutrient intake between wethers and does in each season, except for the ADF and ME intake per metabolic weight (LW0.75). The nutrient digestibilities were higher in spring and summer, and decreased significantly during the autumn and winter (p<0.05). Goats, especially wethers, had a relative constant NDF digestibility across seasons, however, the apparent digestibility of CP in both wethers and does, decreased to negative values in winter. The grazing goats experienced relatively sufficient nutrients supply in spring and summer, and a severe deficiency of CP and ME in winter.
Study on Degradation Character of Leymus chinensis and Alfalfa Products in the Cow Rumen
Herbage is indispensable coarse fodder to ruminants.With the development of herbage industry,different herbage products has been applied to production.It directs the change of nutritive value after processing,The ratios of disappearance and degradation of crude protein(CP) and neutral detergent fibre(NDF) of different herbage products(grass powder,grass pellets) were determined in the cow rumen using Nylon Bag method.The results showed:(1) the ratio of disappearance of crude protein(CP)of alfalfa powder was higher than Leymus chinensis cv.Jisheng power,Leymus chinensis powder,Leymus chinensis cv.Jisheng pellet(p0.05),the extent of ascend was distinct after 12h.(2) the ratio of disappearance of NDF of alfalfa powder in 12h,24h,72h was higher than Leymus chinensis cv.Jisheng pellet,Leymus chinensis cv.Jisheng powder,Leymus chinensis powder(p0.05).(3) the ratios of disappearence and degradation of neutral detergent fibre(NDF) of Leymus chinensis cv.Jisheng pellet were higher than Leymus chinensis cv.Jisheng powder,Leymus chinensis powder.The ratios of disappearance and degradation of crude protein(CP) and neutral detergent fibre(NDF) of Leymus chinensis cv.Jisheng powder were higher than Leymus chinensis powder.
Use of N-alkanes to estimate intake and digestibility by beef steers
The objective of the study was to evaluate the use of n-alkanes to estimate DM intake and digestibility by beef cattle. Six steers were blocked (3 blocks, 2 animals/block) according to the body weight (279±19 kg) and randomly allotted within blocks to two diets (3 steers/diet). A second trial was conducted with the same animals (321±18 kg) after 36 days (d), using a switch back design. The diets consisted of two types of chopped sun-cured hay, alfalfa (Medicago sativa L) hay, or fescue (Festuca arundinacea Schreb) and alfalfa mixture, which were fed in equal amounts to steers. Animals were dosed with C32 and C36 alkanes, employing an intra-ruminal controlled-release device at the beginning of each trial. Hay intake per animal was measured from d 6 to 12 and sub samples were taken for chemical analysis. Rectal samples of feces were taken from each animal once/daily from d 8 to 14, freeze dried, and ground prior to alkane analysis. Alkanes were extracted from ground hay and feces. Feed intake was calculated from the dose rate of C32 alkane and, the herbage and fecal concentrations of adjacent odd (C33 or C31) and even (C32) chain length alkanes. Crude Protein, NDF, ADF, ash concentrations and In vitro dry matter digestibility (IVDMD) were 17.7, 42.2, 28.4, 7.9 and 71.7 for alfalfa, and 12.4, 56.5, 30.4, 6.9 and 69.1% for fescue/alfalfa mixture, respectively. For both diets, intake estimated from C33:C32 ratio was not different from the measured intake, but intake estimated from C31:C32 ratio was lower (p<0.05), than the measured intake for both diets. The average estimated forage intake from C33:C32 ratio was 4.86 and 0.69% below than the measured intake for alfalfa and, fescue/alfalfa mixed diets, respectively. The respective estimates with C31:C32 ratio were 9.59 and 11.33% below than the measured intake. According to these results, alkane C33:C32 ratio is better than alkane C31:C32 ratio for the estimation of intake by beef steers. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 11 : 1564-1568)