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 Grazing Behavior of Cashmere Goat on Artificial Leymus chinensis Grassland in Songnen Plain
Six Inner Mongolia cashmere goats(3 wethers and 3 ewes with similar live weight) were placed in fenced artificial Leymus chinensis grassland of 1hm2 to observe grazing behavior and rhythm in different seasons in whole year.The results showed that the goats preferred to intake grass ear in the heading stage,as there was only 4.4% residual grass ear after spring grazing;the intake rate in summer was the highest,then the autumn,while the intake time in spring and autumn was longer than winter and summer(P0.05);Dry matter intake(DMI) per bite was the lowest in autumn,the daily DMI was the lowest in winter and the highest in summer;however,the daily DMI of wethers were greater than the ewes in the same season.There were three intake peaks per day in spring,summer and autumn,which appeared at 0.5h after grazing beginning,0.5h after noon and 2h before grazing returning,DMI was greater in the afternoon than in the morning.While in winter,there was an intake peak in the morning and a peak in the afternoon,respectively.In the study,the phenomenon of goats digging grass roots was not observed,however,the habits of goats pushing grass and soil aside to clear up area for resting or ruminating existed.There were no significant sex differences in intake time,stand and walk time,lay and ruminant time and intake rate.
The ability of the n-alkane technique to estimate intake and diet choice of sheep
This study assessed the efficacy of the n-alkane technique to estimate intake and diet composition in animals given single foods or a choice of two. In the first experiment intakes of pelleted ryegrass and lucerne, given either alone or as a choice, were measured in lambs housed indoors in individual pens. Each of the three feeding treatments was given to 12 lambs at two degrees of maturity (0·30 and 0·45 of estimated mature sizes). The 12 lambs were constituted as three replicates of the two sexes of each of two breeds. The measured intakes were compared with those estimated using the n-alkanes C 31 and C 33 , found naturally in the foods, and C 32 , which was given as a dose. On the choice treatment diet composition was estimated using a non-negative least squares procedure and data on C 31 and C 33 alone. The agreement between actual and predicted intake was good: R 2 of 0·938 for log-linear regression with a residual standard deviation of 0·0845. Intake of lucerne when offered alone was slightly yet significantly over-predicted. The proportion of ryegrass in the diet was also accurately predicted ( R 2 of 0·950 and residual s.d. of 0·0398). Using the data on C 27 and C 29 , in addition to that on C 31 and C 33 , gave a poorer agreement with the observed diet compositions. The low and similar levels of C 27 in the two foods meant that this n-alkane provided little extra information that could be used to estimate diet composition. In a second experiment faecal samples were collected every 4 hours over a 24-h period in six lambs on ad libitum, and in six lambs on a restricted quantity, of pelleted ryegrass. There was no significant diurnal variation in the ratios of either C 31 or C 33 to C 32 on either ad libitum or restricted feeding. The time of faecal collection within a day should not therefore affect the reliability of the predictions. The study confirmed the value of using n-alkanes in methods to determine the intake of forages by sheep, and that the time of faecal collection within the day does not affect the reliability of these predictions. The results also confirm the utility of the n-alkane method for estimating diet choice, at least with two-component mixtures.