Die voedingswaarde van weimielies vir lammerooie in die Noord-Oos Vrystaat

[摘要] English: The nutritive value of maize foggage cultivated on a low yield potential soil in the North Eastem Free State, with special reference to four yellow maize cultivars, was examined in a production study with Dohne Merino ewes and their lambs. Four yellow maize cultivars with the same growth season length, but differing in prolificacy, namely PAN 6364 (high prolific), SNK 2950 (semi high prolific), CRN 4512 (semi low prolific) and CRN 4502 (Iow prolific) were cultivated to be grazed as maize foggage by lactating ewes and their lambs. The experimental plot was fertilized with 35 kg N/ha, according to the planned grain yield of 2.5 t/ha. Normal tilling and production practices were applied during cultivation of the maize. The 120 Dohne Merino ewes used as experimental animals were randomly selected out of the local herd. The maize was grazed at a stocking rate of 15 ewes and lambs/ha during a 90-day grazing period. Dry material yield (DM-yield) and grain yield for cultivars were determined during the first month of the grazing period in order to quantify grazing material available to ewes and their lambs. A determination of residues not utilized by sheep during the grazing period was carried out after completion of the grazing period. The quality of grazing material available to ewes was examined in each of the three months of the grazing period, by use of feed samples collected by esophageal fistulated ewes. The dry material intake (DMI) and organic material intake (OMI) of twenty ewes, five per cultivar, were determined at the end of the first month of the grazing period, by use of the chromium oxide marker technique. The digestible organic material intake (DOMI) and crude protein intake (CPI) of ewes for the first month of the grazing period were calculated from the in vitro digestibility and chemical composition of feed samples collected by fistulated ewes. Ewes were weighed every two weeks and lambs every week from parturition till the end of the grazing period. The milk production of twenty ewes, five per cultivar, was determined during Week 1, 3, 5, 7, 9, 11, 13 and 15 of lactation by use of the oxytocin method. The ewes were introduced tomaize foggage during Week 6 of lactation. The milk composition on percentage basis andproduction of milk components were investigated. Mid-rib wool samples were obtained just beforeparturition and again after completion of the grazing period, to ascertain the influence of quality ofgrazing material on wool fibre diameter of ewes.The estimated DM-yield for PAN 6364, SNK 2950, CRN 4512 and CRN 4502 was 4.996, 6.36,5.126 and 4.381 Vha respectively. The estimated grain yield for PAN 6364, SNK 2950, CRN 4512and CRN 4502 was 2.009, 2.782, 2.146 and 2.423 t/ha respectively. The percentage of availablegrazing material utilized by sheep and which disappeared due to weathering for PAN 6364, SNK2950, CRN 4512 and CRN 4502 was 70.08,67.13,62.52 and 66.44 % respectively.Significant differences occurred in the chemical composition of feed samples collected byfistulated ewes during the first and third month of the grazing period. Significant differencesoccurred in ash content of cultivars during the first month of the grazing period, where ash contentof PAN 6364 (20.12 %) and SNK 2950 (19.81 %) were significantly higher (P < 0.05) than that ofCRN 4502 (5.39 %). Highly significant differences occurred in crude protein content of cultivarsduring the first month of the grazing period, where crude protein content of CRN 4512 (15.67 %)was significantly higher (P < 0.01) than that of CRN 4502 (8.53 %). Highly significant differencesoccurred in ADF-content of cultivars during the first month of the grazing period, where ADFcontentof CRN 4512 (23.54 %) was significantly higher (P < 0.01) than that of CRN 4502 (10.26%). Significant differences occurred in ADF-content of cultivars during the third month of thegrazing period, where ADF-content of CRN 4512 (39.04 %) was significantly higher (P < 0.05)than that of SNK 2950 (22.49 %). Highly significant differences occurred in DOM-content ofcultivars during the first month of the grazing period, where DOM-content of PAN 6364 (76.48 %),SNK 2950 (75.73 %) and CRN 4502 (81.71 %) were significantly higher (P < 0.01) than that ofCRN 4512 (66.6 %).The estimated DMI of ewes grazing PAN 6364, SNK 2950, CRN 4512 and CRN 4502 during thefirst month of the grazing period was 1680.45, 1385.54, 1323.61 and 2663.68 g/day respectively.The estimated DMI of ewes grazing PAN 6364, SNK 2950, CRN 4512 and DRN 4502 during thefirst month of the grazing period was 1342.34, 1111.06, 1113.95 and 2520.1 g/day respectively.The estimated DOMl of ewes grazing PAN 6364, SNK 2950, CRN 4512 and CRN 4502 during thefirst month of the grazing period was 1026.62, 841.41, 741.89 and 2059.17 g/day respectively.The estimated ME-intake of ewes grazing PAN 6364, SNK 2950, CRN 4512 and CRN 4502 was15.9,13.0,11.5 and 31.9 MJ ME/day respectively, compared to the ME requirement of 14.2 MJME/day for ewes in late lactation. The estimated CPI of ewes grazing PAN 6364, SNK 2950, CRN 4512 and CRN 4502 during thefirst month of the grazing period was 156.11, 138.99, 174.56 and 214.96 g/day respectively,compared to the total crude protein requirement of 175 g/day for ewes in late lactation. Thedifference in crude protein content of selected grazing material of different cultivars, can beexempted as the most important factor which influenced the mass gain of ewes and lambs and themilk production response of ewes.No significant differences occurred in the average mass of lambs grazing different cultivars duringthe first 49 days of the grazing period. Significant differences occurred in the average mass oflambs at day 61, where the average mass of lambs grazing CRN 4512 (26.36 kg) was significantlyhigher (P < 0.05) than that of lambs grazing CRN 4502 (22.46 kg). Significant differencesoccurred in the average mass of lambs at day 72 and 82, where the average mass of lambsgrazing CRN 4512 (28.69 and 29.81 kg) and SNK 2950 (27.27 and 30.37 kg) were significantlyhigher (P < 0.05) than that of lambs grazing CRN 4502 (23.63 and 25.56 kg). Significantdifferences occurred in the average mass of lambs at day 95, where the average mass of lambsgrazing SNK 2950 (29.32 kg) was significantly higher (P < 0.05) than that of lambs grazing CRN4502 (25.05 kg). The average daily gain (ADG) of lambs on day 82 of the grazing period for PAN6364, SNK 2950, CRN 4512 and CRN 4502 was 187.32, 211.59, 205.24 and 160.37 g/dayrespectively.No significant differences (P > 0.05) occurred in the average mass of ewes grazing differentcultivars during the grazing period. The ADG of ewes on day 72 of the grazing period for PAN6364, SNK 2950, CRN 4512 and CRN 4502 was 106.53, 110.69, 131.39 and 96.39 g/dayrespectively.Milk production of ewes up to Week 13 of lactation did not differ significantly (P > 0.05) amongstcultivars. Significant differences in milk production of ewes only occurred during Week 15 oflactation, where milk production of ewes grazing CRN 4512 (537.49 g/day) was significantlyhigher (P < 0.05) than that of ewes grazing CRN 4502 (219.97 g/day). The milk production ofewes grazing CRN 4512 was characterized by an immediate increase after introduction to maizefoggage, where after it declined gradually, but increased again during Week 15. The milkproduction of ewes grazing PAN 6364 and SNK 2950 maintained a constant level afterintroduction to maize foggage, where after it declined gradually. The milk production of ewesgrazing CRN 4502 was characterized by a slight increase after introduction to maize foggage,where after it declined rapidly.Milk composition and production of milk components, accept for a few instances, did not differsignificantly (P > 0.05) amongst cultivars. Significant differences in milk fat content occurredduring Week 9 of lactation, where milk fat content on PAN 6364 (9.42 %) was significantly higher(P < 0.05) than that on CRN 4502 (6.2 %). Significant differences in milk fat production occurred during Week 7 and 9 of lactation, where milk fat production on PAN 6364 (64.51 and 57.51 g/day)were significantly higher (P < 0.05) than that on CRN 4502 (39.39 and 22.35 g/day). Nosignificant differences (P > 0.05) in milk protein content occurred amongst cultivars. Significantdifferences in milk protein production occurred during Week 15 of lactation, where milk proteinproduction on CRN 4512 (40.71 g/day) was significantly higher (P < 0.05) than that on CRN 4502(16.7 g/day). No significant differences (P > 0.05) in lactose content of milk occurred amongstcultivars. Significant differences in lactose production occurred during Week 15 of lactation,where lactose production on CRN 4512 (29.5 g/day) was significantly higher (P < 0.05) than thaton CRN 4502 (11.13 g/day). No significant differences (P > 0.05) in total solids content of milkoccurred amongst cultivars. Significant differences in total solids production occurred duringWeek 15 of lactation, where total solids production on CRN 4512 (110.47 g/day) was significantlyhigher (P < 0.05) than that on CRN 4502 (49.99 g/day).No significant differences (P > 0.05) occurred in wool fibre diameter of ewes grazing differentcultivars after completion of the grazing period.Lambs grazing SNK 2950 and CRN 4512 attained the highest mass gain during the grazing periodof 17.35 and 16.83 kg/lamb and consequently attained the highest gross margin of R 447.52/haand R 404.62/ha respectively. Lambs grazing PAN 6364 and CRN 4502 attained a lower massgain during the grazing period of 15.36 and 13.15 kg/lamb and consequently attained a grossmargin of R 283.34/ha and R 101.02/ha respectively.The utilization of maize foggage by ewes and their lambs during the critical winter months in theNorth Eastern Free State, can play a significant role in bridging the gap in fodder flow usuallyexperienced at this time of year. Maize foggage produces fodder of sufficient quantity and qualityto ewes and their lambs, which can contribute to excellent growth results, an increase in milkproduction of ewes and a decrease in the occurrence of tender fleeces. The utilization of maizefoggage by ewes and their lambs is economically profitable and only in instances of high grainprices prevailing, will a higher gross margin per hectare be realized.

[发布机构] University of the Free State