The utilization and supplementation to stubble lands for South African mutton Merino ewes

[摘要] ENGLISH ABSTRACT:An experiment was conducted to determine the effect of the frequency of supplementaryfeeding on the production of South African Mutton Merino (SAMM) ewes grazing wheat stubble.One hundred and sixty ewes were randomly divided into two groups that consisted of four groupseach. Eight camps were grazed for 138 days during which lambing occurred. Four groups of 25ewes each grazed a 17 ha camp at a stocking density of 5.8 ewes/ha and four groups of 15 eweseach grazed a 12 ha camp at a stocking density of 5.0 ewes/ha. A combination energy/proteinsupplement was made available to the ewes as a lick. Two of the groups received no supplementaryfeed (control), two groups received 200 g/ewe/day, two groups received 400 g/ewe every secondday and two groups received 600 g/ewe every third day. The smallest decrease in weight during thefeeding period was observed in the ewe group that received supplementation every day as well asthe ewe group that received supplementation every second day, but no significant differences wereobserved between these two groups. The smallest decrease in weight over the total feeding periodwas observed in the three ewe groups that received supplementation (P < 0.1), while the ewes thatreceived none (control groups) lost the most weight during the same period. All supplementedgroups performed significantly better than the unsupplemented control group in terms of theliveweight change over the feeding as well as the total period. No significant differences occurredin the lambing percentage, weaning percentage, birthweight, 42-day weight and survival rate of thelambs due to the different feeding regimes. It was concluded that supplementation to ewes everythird day or every second day is an economically feasible option and will reduce labour andtransport costs. In the second study the effect of stocking density on canola stubble composition andsubsequently the production of SAMM ewes on this type of stubble was investigated. Forty-eightewes were randomly divided into four groups that grazed canola stubble at a stocking density ofapproximately 1.5, 3.5, 5.5 and 7.5 ewes/ha for 152 days. The ewes did not receive anysupplementation and were weighed every 14 days. Parturition occurred during the last week inMarch 1997 until the first week in May 1997, and the lambs were weighed at birth, and every 14days thereafter. Stubble samples were collected from the paddocks during the first part of the trial(January and February) and at the end of the trial (April and May) by cutting ten replicate quadratesper paddock and were analysed for dry matter (DM), crude protein (CP), acid detergent fibre(ADF), neutral detergent fibre (NDF) and in vitro digestibility of organic matter (IVDOM). Thelive weight of the ewes at a stocking density of 5.5 ewes/ha decreased significantly, while the ewesat a stocking density of 1.5 ewes/ha gained weight. The ewes at a stocking density of 3.5 ewes/hahad the lowest weight loss (P = 0.01). Stocking density did not affect the birthweight of the lambssignificantly. The CP concentration of the stubble decreased with an increase in stocking density,while the ADF and NDF concentration of samples were significantly higher at the higher stockingdensity.In the third study the supplementation of rumen inert fat or starch on the production of ewesgrazing wheat stubble, was investigated. Fifty-six SAMM ewes were randomly divided into fourgroups of 14 ewes each, grazing the wheat stubble at a stocking density of 4.6 ewes/ha. Each groupwas supplemented with 250 gJewe daily for the last six weeks of pregnancy, which was increased to360 gJewe during the first four weeks of lactation. Supplementation was supplied on Mondays,Wednesdays and Fridays for a 70-day period. The CP concentration of the supplement variedbetween 16.7 % and 19.6 %, while the total digestible nutrient (TDN) content varied between52.0 % and 76.7 %. No significant difference (P > 0.05) occurred between the live weights of ewesduring the last six weeks of pregnancy, the first four weeks of lactation, or the total feeding period.The ewes in the 50 % fat plus 50 % maizemeal group lost less weight (P :s; 0.08) during lactationthan the ewes that received maizemeal as their main energy source. The study indicated that therewas no significant advantage in the live weight change of the ewes during the experimental period,when compared to the group that received wheat bran (control group).In the fourth study the economic advantage of supplementation to SAMM ewes grazingwheat- or oat stubble were studied. Three hundred and sixteen ewes were divided into four flocks,of which two grazed oat stubble and two wheat stubble. Each of these four flocks was againsubdivided into four subdivisions of which two subdivisions received supplementation and twonone. Four subdivisions received 200 g/d for 83 days, and the other four subdivisions received 200g/d for 44 days after which it was increased to 300 g/d for 37 days (81 days in total). The eweswere weighed monthly. The final bodyweight of the ewes that received supplementation wassignificantly higher than those that received none. Over the feeding period, the ewes that receivedsupplementation had a significant lower weight loss in comparison to the ewes that did not receivesupplementation. The 42-day weight of the lambs improved significantly due to supplementation,but no significant increase was indicated in the birthweight, weaning weight and survival rate of thelambs whose mothers received supplementation.In the fifth study the influence of supplementary feeding to ewes and creep feeding of theirlambs on the production of both the ewes and lambs were studied. One hundred and sixty eightewes were divided into two groups of 68 and 100 ewes that grazed a 12.9 and 18 ha camprespectively. Each of these ewe groups was subdivided into four groups of which two ewe groupsreceived supplementation and two none. Within each ewe group two groups of lambs receivedcreep feeding and two received none. A two (supplementation of ewes) by two (creep feeding oflambs) factorial design was used. Supplementation was supplied at 200 g/d for the first 69 days and300 g/d for the next 120 days to ewes. Lambs received an average ofO.58 kg creep feed per day for96 days. It was concluded that the live weight change (LWC) of the ewes during the experimentalperiod was not affected significantly by creep feeding of their lambs. Ewes that receivedsupplementation maintained higher live weights than their counterparts for most of the feedingperiod, although final weights at the end of the experimental period did not differ significantly. Theaverage daily gain (ADG) of the lambs whose mothers received supplementation tended to behigher than that of mothers that received no supplementation, while the ADG of the lambs thatreceived creep feeding was significantly higher than the lambs that received none.In the sixth study the carry-over effect of supplementation in the previous year on theproduction of the ewes in the following year was studied. Three hundred and sixteen ewes weredivided into four flocks, of which two grazed oat stubble and two wheat stubble. Each of these fourflocks was again subdivided into four subdivisions of which two subdivisions receivedsupplementation and two none. Four subdivisions received 200 g/d for 83 days, and the other foursubdivisions received 200 g/d for 44 days after which it was increased to 300 g/d for 37 days (81days in total). The ewes were weighed monthly. Results indicated that birth status (lambs born perewes mated) of lambs showed a tendency to increase in 1999 due to supplementation in 1998, whileweaning status was not significantly affected. Due to multiple births in the supplemented groups,the birthweight and weaning weight of lambs was negatively affected by supplementation. Thestudy concluded that supplementary feeding in the previous year did not have significant carry-overeffects in the following year. However, the effect may have been influenced by the fact that matureanimals were used in the study, while the pasture availability during the non-productive stage willalso affect possible carry-over effects.

[发布机构] Stellenbosch University