STOCK THRIFT STUDIES AT WINCHMORE

Press, Volume XCIX, Issue 29401, 31 December 1960, Page 8

STOCK THRIFT STUDIES AT WINCHMORE

Results Similar To Last Year

Hl-thrift trials conducted by the Department of Agriculture’s irrigation research station at Winchmore during the 1959-60 season are being repeated again this season to evaluate the influence of seasons on the various factors capable of limiting the rate of lamb growth.

The results of the trials to date are similar to those obtained last season. The level of feeding ewes in late pregnancy has had little effect on the birth weight of single lambs but some effect on the weight of twin lambs. Selenium has been the only trace element to give a response but once more the availability of feed has been found an over-riding factor in lamb growth rate. At this stage of the season lambs have again been found to do best on their mothers. Early weaning has meant lighter weight lambs.

The trials at Winchmore are designed to assess the importance of trace mineral deficiencies, parasitism, herbage unpalatability, feeding levels, and the value of hormonal growth stimulants. Some of these trials were begun during pregnancy and will continue through until autumn while many short term studies are being initiated after weaning and may be continued for only a few weeks. Just before Christmas several of the experimental groups of ewes and lambs had been weaned and it was an appropriate time to review the effects of the treatments applied to both. the ewes and their lambs. “The current season has undoubtedly been favourable to lamb health as evidenced by the observation that lamb drafts taken before December 1 have been commonly 50 per cent, larger than normal,” says Mr M. K. Hill, a scientific officer at the station, who is in charge of the animal health investigations. Feeding Of Ewes On the station this season the birth weight of single Romney lambs averaged 11.31 b, which was Ub more than last season. As was the case last season, Mr Hill says that the birth weight of single lambs was not influenced by the feeding level of ewes in the last six weeks of pregnancy, but twins at birth weighed on average Vilb more where they were from ewes which had been on a high plane of nutrition compared with lambs from mothers on a low plane of feeding. Ewes on a low plane of nutrition during this period were allowed three-quarters of an

hour daily on autumn-saved pasture while those on a'fcjgh plane had four to five hours a day on this feed. “Considering the Ashburton county lamb crop as a whole, the improvement in the size of the early drafts is probably a reflection of feed abundance,” says Mr Hill. In some of the station trial groups, however, where abundant feed had been deliberately provided both last year and again this year lamb growth rates were remarkably similar in both seasons in lambs of comparable age. Though Down cross lambs had frequently given growth rates of 51b and 61b a week in September to Noyember, Romney lambs under similar conditions and during the same period had averaged 41b a week. “Several breeds of sheep have the milking ability to allow their Down cross lambs to grow at the rate of more than 71b a week over the first six weeks of life,” states Mr Hill. “It is not surprising, therefore, that the New Zealand agricultural colleges are devoting considerable effort to the reorganisation of the sheep industry stratification with the ultimate introduction of superior lamb rearing ewes. Nevertheless, the potential growth rate of Down cross lambs is seldom realised, a fact made abundantly clear by the relatively small proportion—2s per cent—of an average fat lamb crop that does not graze its way into the new year.”

Milk Production In one trial this season Romney ewes which gave birth to twin lambs were treated with the thyroid gland hormone in an effort to stimulate milk production and a female sex hormone was used in the lambs in an attempt to increase the appetite of the lamb. The ewes were treated on the day of lambing and one lamb from each set of twins was treated at marking. The lambs in each of the four groups involved in the trial averaged 9.31 b at birth. At weaning on December 14 lambs from the ewes treated with the thyroid gland hormone, thyroxine, weighed . 59.31 b compared with 57.91 b for the lambs from untreated mothers. At the same time the lambs which had received the appetite stimulating

hormone averaged 59.61 b with the untreated controls averaging 57.61 b. Mr Hill said that the effect of neither hormone was marked but it was considered that the thyroxine used was inactive as there was no post-treatment loss of weight in treated ewes.

The use of a specially prepared feed supplement of high sugar and low protein content in conditions of adequate pasture availability had no measureable influence on the growth rate of suckling lambs. Only Response Of trace minerals used to date, only selenium is producing a response. These trials are running on exactly the same blocks as last season and in one of these, where post lambing to preweaning feeding levels and trace minerals are under investigation, last season’s trends are being observed again. Where five ewes and their lambs were running to the acre weights at weanihg on December 13 were 59.71 b compared with 53.81 b where nine ewes and their lambs were being carried to the acre. Similarly last season there was an average difference of almost 61b between the two groups at the same stage. The weaning weights of lambs from ewes which had been treated with selenium were 57.61 b compared with 55.81 b where the mothers were untreated. Last season the comparable two figures were 55.91 b and 52.41 b. Mr Hill said that the lambs in the trial this year were one week older at weaning than last season’s lambs and this accounted for most of the difference in the two years. This trial was representative of observations on the station which indicated that selenium responses this year were considerably less than last season. In the case for which figures were quoted the less marked selenium response this season was probably not due to selenium return in the dung and urine of treated animals in the preceding season, since another area not selenium responsive in 1959 was now giving indications of being selenium deficient in spite of the dung and urine return last season. An investigation conducted last season indicated that high sulphate and high arsenic intakes would be unlikely to be casual factors in inducing a selenium deficiency. Low plant selenium levels were probably the result of a simple reduction in the rate of selenium uptake and in the light of past experience this could be closely allied to the rate and stage of pasture growth. “Though considerable selenium responses do occur in the months of September to November our experience indicates that the largest responses occur from December to February,’’ states Mr Hill. “Station responses decline during the autumn and reach their lowest levels during the winter.”

The feeding level had however, again dictated growth rates to a greater degree than the use

of selenium, cobalt, copper or bephenium embonate for the control of worm parasites. As last season the weather during November had been conducive to an attack of nematodirus, the parasite for which bephenium was devised, and the use of bephenium had slightly more effect this season than • for the same period last year. Between October 27 and December 12 this year treated lambs gained 19.51 b compared with 17.51 b for untreated lambs, whereas last year the comparable gain for treated lambs was 21.81 b but controls did as well putting on 21.91 b. Weaning Dates Another of the major trials investigating weaning dates and trace mineral usage in both ewes and lambs in various combinations has again shown that there is a growth rate reduction associated with early weaning at eight weeks of age and has indicated a selenium response in an area which was not responsive to the trace element last year. At December 14 this year selenium treated lambs weighed 66.81 b compared with 65.21 b for untreated lambs. Last year at a comparable date there was a variation in favour of the treated lambs between 70.21 b and 69.61 b. Last year the unweaned lambs were nearly 61b heavier than lambs weaned at eight weeks. This season at December 14 the early weaned lambs weighed 64.61 b whereas those still on their mothers averaged 67.41 b. These figures do not give a clear selenium picture, states Mr Hill, as it is only a few weeks since the selenium response started to become apparent in the trial referred to.

In trials yet to be initiated in weaned lambs trace minerals, phenothiazine, high nitrate pasture and carbohydrate supplementation will again be under study. An important deviation this season will b'e the use of three mineral drenches—one containing the eight major elements in the correct proportions for animal requirements, another containing the it trace minerals, and a third the 24 micro elements also known to occur in the animal body but with no known physiological function. These 43 minerals will be used in defining whether or not some forms of illthrift are inorganic or organic. The possibility of a mineral toxicity is under study in an indoor feeding experiment where suspect pastures are being fed to ewes with single lambs and th'' ash of several pounds of the same pasture is to be drenched daily. The main part of the indoor experiments using suspect pasture consists of measuring palatability, voluntary feed consumption, milk production and lamb growth rates.

Unpalatability "The most mysterious fraction of the ill-thrift problem is that of pasture unpalatability,” says Mr Hill. “In most instances of unpalatability intake of feed is restricted to the maintenance of life. In ewes with lambs the first thing to suffer under these conditions is milk production and this is reflected in low lamb weight gains. In the case of weaned lambs little food is consumed in excess of maintenance and consequently little material is available for weight gain. Last season’s indoor feeding experiments clearly demonstrated the marked difference between, consumption of excellent herbage and that of material cut off areas where lamb health had been poor.

“Mineral deficiencies can be easily remedied, mineral imbalances can be corrected, parasites can be controlled, but the question as to why after correcting mineral deficiencies and eliminating parasites an animal consumes 2000 grams of oiie pasture mixture per day and only 300 grams of the same mixture grown under different conditions will only be. resolved by clearer understanding of the complex biochemical changes which make up the growing and maturing phases of pasture plant nutrition,” says Mr Hill.