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

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 to maize foggage during Week 6 of lactation. The milk composition on percentage basis and production of milk components were investigated. Mid-rib wool samples were obtained just before parturition and again after completion of the grazing period, to ascertain the influence of quality of grazing 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 4512 and CRN 4502 was 2.009, 2.782, 2.146 and 2.423 t/ha respectively. The percentage of available grazing material utilized by sheep and which disappeared due to weathering for PAN 6364, SNK 2950, 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 by fistulated ewes during the first and third month of the grazing period. Significant differences occurred in ash content of cultivars during the first month of the grazing period, where ash content of PAN 6364 (20.12 %) and SNK 2950 (19.81 %) were significantly higher (P < 0.05) than that of CRN 4502 (5.39 %). Highly significant differences occurred in crude protein content of cultivars during 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 differences occurred in ADF-content of cultivars during the first month of the grazing period, where ADFcontent of 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 the grazing 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 of cultivars 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 of CRN 4512 (66.6 %). The estimated DMI of ewes grazing PAN 6364, SNK 2950, CRN 4512 and CRN 4502 during the first 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 the first 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 the first 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 was 15.9,13.0,11.5 and 31.9 MJ ME/day respectively, compared to the ME requirement of 14.2 MJ ME/day for ewes in late lactation. The estimated CPI of ewes grazing PAN 6364, SNK 2950, CRN 4512 and CRN 4502 during the first 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. The difference in crude protein content of selected grazing material of different cultivars, can be exempted as the most important factor which influenced the mass gain of ewes and lambs and the milk production response of ewes. No significant differences occurred in the average mass of lambs grazing different cultivars during the first 49 days of the grazing period. Significant differences occurred in the average mass of lambs at day 61, where the average mass of lambs grazing CRN 4512 (26.36 kg) was significantly higher (P < 0.05) than that of lambs grazing CRN 4502 (22.46 kg). Significant differences occurred in the average mass of lambs at day 72 and 82, where the average mass of lambs grazing CRN 4512 (28.69 and 29.81 kg) and SNK 2950 (27.27 and 30.37 kg) were significantly higher (P < 0.05) than that of lambs grazing CRN 4502 (23.63 and 25.56 kg). Significant differences occurred in the average mass of lambs at day 95, where the average mass of lambs grazing SNK 2950 (29.32 kg) was significantly higher (P < 0.05) than that of lambs grazing CRN 4502 (25.05 kg). The average daily gain (ADG) of lambs on day 82 of the grazing period for PAN 6364, SNK 2950, CRN 4512 and CRN 4502 was 187.32, 211.59, 205.24 and 160.37 g/day respectively. No significant differences (P > 0.05) occurred in the average mass of ewes grazing different cultivars during the grazing period. The ADG of ewes on day 72 of the grazing period for PAN 6364, SNK 2950, CRN 4512 and CRN 4502 was 106.53, 110.69, 131.39 and 96.39 g/day respectively. Milk production of ewes up to Week 13 of lactation did not differ significantly (P > 0.05) amongst cultivars. Significant differences in milk production of ewes only occurred during Week 15 of lactation, where milk production of ewes grazing CRN 4512 (537.49 g/day) was significantly higher (P < 0.05) than that of ewes grazing CRN 4502 (219.97 g/day). The milk production of ewes grazing CRN 4512 was characterized by an immediate increase after introduction to maize foggage, where after it declined gradually, but increased again during Week 15. The milk production of ewes grazing PAN 6364 and SNK 2950 maintained a constant level after introduction to maize foggage, where after it declined gradually. The milk production of ewes grazing 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 differ significantly (P > 0.05) amongst cultivars. Significant differences in milk fat content occurred during 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). No significant differences (P > 0.05) in milk protein content occurred amongst cultivars. Significant differences in milk protein production occurred during Week 15 of lactation, where milk protein production 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 amongst cultivars. 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 that on CRN 4502 (11.13 g/day). No significant differences (P > 0.05) in total solids content of milk occurred amongst cultivars. Significant differences in total solids production occurred during Week 15 of lactation, where total solids production on CRN 4512 (110.47 g/day) was significantly higher (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 different cultivars after completion of the grazing period. Lambs grazing SNK 2950 and CRN 4512 attained the highest mass gain during the grazing period of 17.35 and 16.83 kg/lamb and consequently attained the highest gross margin of R 447.52/ha and R 404.62/ha respectively. Lambs grazing PAN 6364 and CRN 4502 attained a lower mass gain during the grazing period of 15.36 and 13.15 kg/lamb and consequently attained a gross margin 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 the North Eastern Free State, can play a significant role in bridging the gap in fodder flow usually experienced at this time of year. Maize foggage produces fodder of sufficient quantity and quality to ewes and their lambs, which can contribute to excellent growth results, an increase in milk production of ewes and a decrease in the occurrence of tender fleeces. The utilization of maize foggage by ewes and their lambs is economically profitable and only in instances of high grain prices prevailing, will a higher gross margin per hectare be realized.