Use of the standard cow technique as an aid to problem definition in on-farm evaluations of feeding programmes.

Abstract

Animal Production in Australia Vol. 15 USE OF THE STANDARD COW TECHNIQUE AS AN AID TO PROBLEM DEFINITION IN ON-FARM EVALUATIONS OF FEEDING PROGRAMMES G.K. REASON*, P.N. THURBON* and W.N. ORR** SUMMARY The evaluation of pasture based feeding systems which influence dairy cow production at various stages of lactation is a continuing process which provides herd management information to farmers and research workers. This paper describes a technique for evaluation of farm feeding systems based on a 'standard' or expected lactation curve. Two basic feed systems - dryland and irrigated - have been investigated using this technique. INTRODUCTION ihe shape many investigati used to predict serve as a manag computer based s (Esslemont 1980, prediction of in and a comparison These prediction by Wood (1967, 1 of the lactation cu ons (Johanssen 1961 overall herd milk p ement aid in regula ystems are availabl 'Supercow' 1981). dividual cow yields of actual and pred 1s are all based on 968, 1969, 1970, 19 we 0 f dairy cows has been the subject of ; wo o d 1976). This information has been roduc ting e fatSome (net icted the 1 76). tion performance and therefore farm output. In Britain, several projecting herd production of these systems allow for essary for the farm yield prediction) yields on an individual cow basis. actation curve model as proposed The evaluation of dairy farm feed production and utilization systems is important to both research workers involved in on-farm investigations and to dairy farmers in assessing those factors which appear to be constraints to increased production. This paper provides some results based on a method of assessment of on-farm feed production and utilization systems using the shape of the lactation curve. MATERIALS AND METHODS A study based on 42 herds in three Queensland dairying regions (i.e. Moreton, Darling Downs and Central Queensland) was undertaken. The data available from the production recording scheme operated by the Queensland Department of Primary Industries included individual cow milk production, stage of lactation, number of cows, and calving dates. Cow milk production was recorded on a monthly basis with the stage of lactation recorded as days from calving date to date of production recording. The study was carried out using data on to February 1983 inclusive. In all, 2949 cow production for all cows was 3285 litres. Two investigated - irrigated farms with more than and dryland farms. milk production from January 1982 lactations were used. The average farming systems were 0.1 ha of irrigation per cow, *D.P.I., G.P.O. Box 46, Brisbane, Qld 4001. **D.P.I., P-0. Box 27, Kairi Research Station, Kairi, Qld 4872. 553 Animal Production in Australia Vol. 15 The number of cows in each of 10 stage of lactation sub-classes were calculated for each herd for each month. Using correction factors derived from lactation curves, the number of 'fresh' or 'standard' cow equivalents per month was calculated for each herd. These correction factors were based on a lactation curve which rises to a peak production at 30 - 45 days post partum and then declines at a rate of 10% per month. The complete list of factors used is shown in Table 1 l TABLE 1 Standard cow correction factors RESULTS The mean production per standard cow by months for each farming system is given in Table 2. 554 Animal Production in Australia Vol. 15 TABLE 2 Mean production per standard cow by months for irrigated (22 farms) and dryland (20 farms) systems DISCUSS ION The shape of the lactation curve has been studied and Wood (1967, 1968, 1969, 1970, and 1976) has developed algebraic models tc describe the lactation curve in detail. The shape of the curve is known to be affected by many factors such as age, fertility, and season of calving. Environmental factors also play a major role. Wood (1969) found that daily yield was depressed during the winter months and stimulated during spring to an extent that was independent of stage of lactation. Wood (1972) reported that on 161 completed lactations in a herd kept indoors all year and fed grass silage ad libitum, there was no apparent variation in persistency or weeks to peak yield for animals calving in different months, suggesting that the shape of the curve was substantially the same for all cows irrespective of their calving dates. Wood (1972) concluded that the seasonality of production as previously described was due to changes in feed quality. It is reasonable on the basis of our current knowledge to assume that given adequate feed, a cow would produce milk according to a 'normal' lactation curve; i.e. rise to a peak yield 15-45 days post calving (Wood(1972) found peak yield to occur at 34 days post partum) and then decline at a rate of 10% per month. Variation from this 'normal' curve can then be attributed to changes in the feed supply (quantity and/or quality). 555 Animal Production in Australia Vol. 15 Kumar (1981) evaluated the standard cow technique using the HolsteinFriesian herd at the Queensland Agricultural College. He found that while average milk production per cow did not reliably reflect changes in feed SUPPlY t the removal of stage of lactation effects using the IIstondard' cow corrections clearly showed a mecsure of feed affected fluctuations in milk yield. The use of information on digestible energy intake and stage of pregnancy accounted for 71% of the variation in 'standard' cow milk yield. CONCLUS TONS The 'standard cow' technique is a useful aid to problem definition in dairy herd production investigations. Tn this case the problem areas defined in terms of requirements for further research are late summer and early autumn feed production on irrigated farms, and the late summer-autumn-winter period in dryland farms (See Table 2). The data from Table 2 indicates that feed quality and quantity decline quite rapidly from January. It also indicates that there are substantial deficiencies in the management and utilization of feed supplies during this autumn period. Further work is being done on individual farms to investigate the effects of liveweight changestage of pregnancy and supplementation on the standard cow method. REFERENCES ESSLEMONT, R.J. and STEPHENS, A.J.,(lWO). Reed ing Un iversi tv . 'Daisy - The Manual' ing' JOHANSSEN, 1 ., (1961). 'Genetic Aspects of Dairy Cattle B pub1 ished by University of Illinois, 1961. KUMAR, V., (1981). 'Use of the 'Standard Cow' method for investigating nutritional problems associated with milk production'. School of undergraduate studies, Qld Agric. College, Lawes. SUPERCOW, (1981). Yupercown Upthorpe computer programmes U.K. Nature 216: 164a -= WOOD, P.D.P., (1967). WOOD, P.D.P., (1968). Nature 218: 89.4. 11:(3) 307. - WOOD, P.D.P. ,(1969). Anim. Prod. WOOD, P.D.P. ,(1970). Anim. Prod. 12: 535. _C WOOD, P.D.P. ,( 1972). Anim. Prod. WOOD, P.D.P. ,( 1976). Anim. Prod. 15: T 89t 22: n 35. 556