Effect of sodium bentonite on the productivity of lactating dairy cows fed good quality pasture supplemented with a high energy concentrate.

Abstract

Animal Production in Australia Vol. 15 EFFECT OF SODIUM BENT0NITE ON THE PRODUCTIVITY OF LACTATING DAIRY COWS FED GOOD QUALITY PASTURE SUPPLEMENTED WITH A HIGH ENERGY CONCENTRATE CAROLINE LEMERLE*, C.R. ST0CKDALE* and T.E. TRIGG* Two experiments examined the responses of pasture-fed dairy cows to a high energy supplement that included 4.8% sodium bentonite. The results indicated that bentonite did not affect the productivity of dairy cows in either early or late lactation when fed good quality pasture supplemented with varying amounts of high protein pellets. In addition, the use of four rumen cannulated COWS in late lactation to provide information of the effect of bentonite on rumen parameters showed that bentonite did not result in any marked buftering capacity nor did it influence nitrogen utilization. I~ODUCTION Sodium bentonite (NaBI is a naturally occurring material with a high montmorillonite clay content. It is often used by stockfeed companies as a stockfeed pelletizing agent. NdB commnly used in the United States as an additive to stock feed also has a strong buffering capacity (Dunn et al. 1979) and it my influence rumen fermentation patterns and nitrogen utilization (Coiling and Britton 1975). However, the effects of Australianmined NaB on ruminant nutrition and productivity, particularly of lactating dairy cows, has not been studied. This paper therefore reports the results of two experiments which examined the responses of pasture-fed dairy cows to a high energy supplement that included NaB. MATERIALS AND METHODS Two experiments were done in September/October, 1982. In Experiment 1, cows in either early or late lactation were offered 6.5 kglWcow/day of good quality pasture &olium perenne/Trifolium repens; in vivo DM digestibility in sheep, nitrogen content and neutral detergent fibre of 73.9, 3.31 and 30.6%, respectively). The pasture was supplemented with pellets ranging from 1.8 to 9.6 kgBM/cow/day; the nitrogen content and neutral detergent fibre were 2.50 and 13.0%1 respectively. Of the ten cows in early lactation and five in late lactation that were used in mperiment 1, six in early lactation and three in late lactation were offered pellets consisting of 4.8% NaB. The cows were fed in stalls for a 19-day preliminary period followed by 15 days of data collection. They were offered pasture first, at 08.00 and 16.00 h, and the pellets were offered after the pasture was eaten. Esrperiment 2 involved four rumen-cannulated cows in late lactation. These were used in a cross-over design; each period was of 15 days duration, the last seven of which animal data were collected. Each cow was offered 6.6 kgDM/cow/day of pasture plus 4.5 kgDM/cow/day of pellets. Cows consumed pellets either with or without NaB. The pasture and pellets were similar to that fed in Experiment 1. The main difference was that the pellets in Experiment 1 contained 2.2% limestone while those used in Experiment 2 did not. Measurements (i> Exp&ments 1 and was recorded at each milking, the fat Milk yield 2 content was measured daily and the protein content once each week. RumenpH * Animal and Irrigated Pastures Research Institute, Kyabram, Vic. 3620. 424 Animal Production in Australia Vol. I5 was measured at the beginning and end of the experiment. Samples of the pasture and pellets were collected daily for determinations of DM content, Kjeldahl nitrogen and neutral detergent fibre Goering and van Soest 1970). (ii) Biment 2 consumed and the AIA cow was calculated. bulked, and analysed (1977) . From the acid-insoluble-ash (AIA) content of the diet content of the faeces, digestibility of the diet of each Feed and faeces samples were collected twice each day, for AIA according to the method of van Keulen and Young Rumen ammonia was determined for each animal from samples taken at 16.00 h each day. Chromium digesta to determine was administered to collected at 3, 6, 9, EIYTA (Cr-EIYW was used to mark the liquid phase of the rate of passage (Faichney 1975). A single dose of Cr-WA each cow at 08.00 h on day 9. Samples of rumen fluid were 12, 15, 24, 30, 36 and 48 h after dosing. The nylon bag technique (Mehrez and Orskov 1977) was used to measure nitrogen degradability of the food. Bags were inserted at 09.00 h on day 11 and retrieved at 1, 3, 6, 9, 12, 24, 48 and 72 h from each animal. RESULTS . nt 1 The results of feeding quantities of pellets ranging from 1.8 to 9.6 kgDM/cow/day in early lactation and 1.8 to 6.1 kgDM/cow/day in late lactation, either with or without which were analysed bY regression analysis r indicated that there were no significant effects of tne use of NaB on animal productivity at either stage of lactation. Mean milk yield, fat content and protein content of the cows in early lactation were 20.0 (kg/cow/day) 3.72% and 3.02& respectively, and rumen pH was 7.32. Cows in late lactation produced 11.9 kg milk/cow/day which contained 4.44% milk fat and 3.46% protein. Rumen pH for these cows was 7.25. mm3 1. Effect of feeding 4.5 kgDM/cow/d of pellets C+NaB) to dairy cows in late lactation on milk yield (kg/cow/d) I milk composition (%I I diet digestibility (% of dry weight) I rumen mnia (rrgN/lOO ml rumen fluid) I rumen volume (1) I dilution rate of digesta liquid phase (%/h) and flow rate of liquid phase of digesta fram the rumen (l/d). t Values in rows with a common letter do not differ significantly (P<O.OS) 425 Animal Production in Australia Vol. 15 The results of feeding 4.5 kgWcow/day of: pellets (+NaB) to cows in late lactation are presented in Table 1. Analysis of variance revealed that. there were again no significant effects of NaBon dairy cow productivity. As for animal productivity, there were no significant effects of NaB supplementation on any of the rumen parameters measured (Table 1). In addition, nitrogen degradability in nylon bags was not affected @ the use of NaB; 85% of total nitrogen had disappeared after 48 h from the feed in both treatments. DISCUSSION The major result of this experiment productivity of lactating dairy cows when fed with varying amounts of high protein pellets. not show any marked buffering capacity nor indicators of nitrogen utilization. was that NaB did not affect the good quality pasture supplemented The results indicate that NaB did did it influence the measured NaB has been used as a potential buffering material for ruminants fed high concentrate diets, and it has also been implicated in the utilization of nitrogen. Reports on the effect of NaB on productivity have in general been conflicting. While Bringe and Schultz ( 1969) and Rindsig et al. (1969) both noted an increase in milk fat content when NaB was added to the concentrate mixture, these studies, plus that ,of Fisher and NacKay (19831, showed that NdB had no significant effect on intake or milk yield. In addition, data obtained using lambs indicate that benefits from the use of NaB with diets high in concentrates my only occur during the first few weeks of feeding (Huntington et al., 1977a,b; Dunn et al., 1979). These variations in the effect of NaB on productivity may be due to variations in physical and chemical properties of NaB, which may in turn depend on site of origin. Rmen pH may be used to indicate the usefulness of a material as a buffer. Although Dunn et al., (1979) found that 2% NdB effectively prevented rumen acidosis in lambs, Fisher and MacKay (19831 reported that 3% NaB was not an effective buffer in lactating dairy cows because NaB lowered rmen pH. Ha etal., (1983) too found that 2% NaB had no significant effect on rumen pH, again in larrbs. In our experiment, concentrates were introduced gradually and this may have been sufficient to prevent any problems associated with rumen acidosis. Improvements in nitrogen digestibility and nitrogen retention have been noted with la&s Kolling and Britton 19751, when diets have been supplemented with NaB. In contrast, Rindsig and and Schultz (1970) recorded a depression in nitrogen digestibility without changes in dry mtter digestibility or nitrogen retention when NaB was included in the diet of dairy cows. In our study, no significant differences were found in milk protein, rumen ammonia, rumen dilution rate or in nitrogen degradibility, the latter detemined using nylon bags. Differences may be expected if NaB was either having a nitrogen sparing effect or an influence on nitrogen degradibility in the rumen. Even if NaBhad resulted inanitrogen sparing effect in the rumen in our experiment, there still my not have been any productive advantage because of the very high level of nitrogen in the diet (2.98% in Experiment 2). It is suggested -that- improvements in-nitrogen utilization may only be realized in situations in which nitrogen is limiting. 426 Animal Production in Australia Vol. I5 We thank Miss Shirley MacKenzie for technical assistance, Dr. G. Robinson for statistical analysis, Fidelity Feeds, Corowa, for the provision of the pellets and Cudgen R.Z. Limited for supplying the bentonite. We also acknowledge financial assistance from the Australian Dairy Research Committee. REFERENCES BRINSE, A.N. and SCHULTZ, L.H. (1969). J. Jl&v Sci. 2 465. COLLING, D.P. and BRITIOY, R.A. (1975). J. Anim. Sci.& 395. DUNN, B.H., EMEEUCK, R.J. and ENTRY, L.B. (1979). J. An& Sci. 48_= 764. FAICHNEY, G.J. (1975). In 'Digestion and Metabolism in the mt,' p. 277, (University of New England editors I.W. McDonald and A.C.I. Warner. Publishing Unit). . FISHER, L.J. and MACKAY, V.G. (1983) Qn. J. AnlIII. Sc i. & 141. GOERI& H.K. and VAN SOEST, P.J. (1970). Agric. Handbook 379, USIN. 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