Effect of hay or grain supplements on the milk protein production from cows grazing green oats.

Abstract

EFFECT OF HAY OR GRAIN SUPPLEMENTS ON THE MILK PROTEIN PRODUCTION FROM COWS GRAZING GREEN OATS B.D. BARTSCH* Summary Friesian cows were grazed on green oats and fed grain and hay All cows received diets estimated to be similar in supplements. The four digestible energy and digestible crude protein content. treatment groups received their digestible energy intakes from the following sources (1) 10% green oats, (2) 8276 green oats and 18% hammermilled barley, (3) 8% gr een oats and 18% pasture hay, and (4) 82% green oats) 9% pasture hay and 9% hammermilled barley. Cows receiving barley compared to cows fed an unsupplemented diet produced similar fat but increased milk protein and solids-not-fat yields, Addition of hay alone to the green oats increased milk protein Treatproduction to a lesser extent than did the feeding of barley. ments had no significant effect on the proportions of casein, whey protein and,+lactoglobulin in the protein fraction or the heat stability and rennet coagulation properties of the milk, Live weights of the cows were not significantly altered by the feeding regimes. I. INTRODUCTION Due to increased demand for milk protein products, the effect of the cows T diet on milk protein production needs investigation. Increased milk protein or solids-not-fat production has been recorded from the inclusion of green oats in the ration of dairy cows (Carter et al. 1965, Newbery 1968) but the green oat intake was not measured. Dietary energy intake alone will influence milk and protein yields (Gordin, Volcani and Birk 1971). This paper describes an experiment in which cows grazing green oats were fed diets estimated tc be of similar digestible energy and digestible crude protein content, with hsy and/or grain substituting for a portion of the green oat intake. Measurements were made of the production of milk, total protein, protein components, solids-not-fat and fat as well as some processing properties of the milk. II. MATERIALS AND METHODS Thirty two grade Friesian cows from the Northfield Research Centre herd were stratified into eigh'L groups an the basis of milk yield, milk composition and stage of lactation.. Cows from each group were assigned to one of four treatment s which received similar digestible energy in-takes supplied by either: (I) 10% green oats; (2) 82% green oats and 18% hammermilled barley; (3) 8f2$ green oats and 1% pasture hay; or (4) 8% green oats, 9% hmmermilled barley and 9% * . Northfield Research Centre, Departmentof Agriculture, Box 1671 G.P.O. Adelaide, South Australia, 5001. r 493 pasture hay. The diets contained in excess of the calculated digestible energy requirement for maintenance and production under grazing conditions (National Research Council 1971)@ During a 14 day preliminary feeding period and a 7 day covariance period, cows were grazed on green oats and fed barley Treatment diets were fed for a 14 day preconcentrate and hay. experimental period followed by the 28 day experimental period. The cows, confined in treatment groups by electric fencing, grazed Swan oats for 3 hours after the morning milking and 1 hour after The oats were initially approximately the afternoon milking each day, 40~x11 in height with the first node of stems just visible. At the completion of the experiment the oats were approximately 6Ocm in height and nearing the T7bootTT stage of d*evelopment. The daily green oat allocation to each treatment group was calculated using the dry matter yield. of the green oats determined on the preceding day and estimates of digestible energy content of green oats from data collected in previous years. During the covariance and experimental periods, eight quadrats (50cm x 5Wm) were cut daily from each treatment area, four before grazing and four after grazing to allow estimation of green oat intake. All samples were washed to remove soil contamination, dried at 100�C for 12 hours, weighed and subsampled. Pasture hay and hammermilled barley samples were taken daily and bulked to give a weekly sample, _ Samples were analysed for in vitro digestible dry matter (Tilley and Terry 1963) from which dig=tmenergy was calculated (Moir 1961). Digestible crude protein was estimated from Kjeldahl nitrogen (Halter and Reid 1959). Milk sampling, recording and analyses and California Mastitis Test procedures were as described by Radcliffe, Home and Chillingworth Once weekly, a daily composite milk sample from each cow was (1972). analysed for casein (McGann, Mathiassen and O'Connell 1972) and /3-lactoglobulin (Fahey and McKelvey 1965). Individual cow samples, bulked proportionately according to treatment, were tested for heat stability (Feagan, Griffin and Lloyd 7966) and rennet coagulation properties (Ellis 1972). Cows were weighed weekly. ' Milk and liveweight data were examined by analyses of covariance, intake data by analyses of variance and California Mastitis Test data by Chi-square heterogeneity tests. III. RESULTS Estimated digestible energy and digestible crude protein intakes did not differ significantly between treatments (Table 1). Digestible energy intakes did not differ between weeks but digestible crude protein intakes declined significantly (PLO.05) from week 1 to week 2 and week 2 to week 3. The average digestible crude protein intake per cow per day (kg) was 3.25, 2.71, 1.87 and 1.97 for weeks I,&3 and 4 respectively. Milk and fat yields did not differ significantly between treatments (Table I). Protein yields were significantly higher (P<O.O5) from cows receiving supplements than from cows receiving only green oats. Cows receiving hammermilled barley produced higher solids-not-fat yields than cows fed only green oats. No significant differences between treatments in milk composition were observed. Treatments showed no effect on casein, and&12ctoglobuli-n percentages or on heat stability and rennet coagulation properties. 494 Analysis of California Mastitis Test data showed no change in the mastitis status of the cows during the experiment. No significant live weight changes were recorded. Final covariance corrected weights (kg) were 510, 5% 9 5% and 532ferunsupplemented, barley supplemented, hay supplemented and barley and hay supplemented groups respectively. TABLE 1 IV. DISCUSSION ' ,Gordin, Volcani and Birk (1971) showed that by increasing the amount of concentrate and consequently energy fed to the dairy cow, milk yield and protein production increased whereas fat production was unaltered. Similar production trends were observed in the present investigations where grain was substituted for green oats in the ration even though the estimated digestible energy and digestible crude protein intakes were similar for all treatments, Ponsef, Huber and Emery (7970) have suggested that energy concentration in the diet as well as level of energy intake is important in milk protein production, Increasing the grain component of the diet increases rumen propionate production with a resultant increase in the protein content of milk. Cows fed green oats ad libitumhave produced more milk of higher solids-not-fat content than wzn fed hay and concentrates (Carter et ale This observed increase in solids-not-fat production may reflect 1965). an increased plane of nutrition due to unrestricted green oat intake rather than any compositional effect of the green oats grazed, In the present experiment, where green oat intake was restricted, solids-not-fat production was lowest from cows fed only green oats, 495 The ratio of protein yield to solids-not-fat yield was similar Since lactose and protein constitute the major for all treatments. portion of solids-not-fat it appears that lactose and protein production were proportionately influenced by the feeding treatments, The proportions of the protein components were unaffected by the feeding regimes in agreement with the results of Gordin, Birk and However, Pousef, Huber and Emery (1970) found that high Volcani (1973). proportions of concentrate in the ration increased the proportion of These conflicting observations are --casein and fi-lactoglobulin. probably due to differences in composition and quantity of feeds offered. These investigations have shown that dietary composition will influence protein and solids-not-fat production when similar quantities Grain of digestible energy and digestible crude protein are fed. concentrate in the diet of grazing dairy cows can increase milk proteins and solids-not-fat production without significantly altering fat production. v. REFERENCES CARTER, O.G., SMITH, Few.9 SMITH, G.J., and McPHILLIPS, J. (7965). Journal of Dairy Science g: 3300. ELLIS, N.J.S. (1972). Australian ?&rnal of Dairy Technology 27: 89. FAHEY, JeL.9 and McKELVEY, E.M. (1965). Journal of Immunology=%: 84. FEAGAN, J.T., GRIFFIN, A.T.9 and LLOYD, G.T. (1966). Journal oFDairy Science 2: 933. GORDIN, S., BIRK,Y. 9 and VOLCANI, R. (1973). Journal of Dairy Science 56: 724. GORDIN, S, VOLCANI, R., and BIRK, Y. (1971). Journal of Dairy Science 38: 287, HOLTER, JZ.9 ad REID, JeTe (1959). Journal of Animal Science 18: 1339. 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