The evaluation of different protein and energy supplements on milk production in pasture-grazed Friesian cattle

E.M. Kiruiro and V.C. Chemitei

National Agricultural Research Centre, P. O. Box 450, Kitale, Kenya

Abstract

A conventional dairy cattle ration (A) and two locally blended energy-protein supplements (B and C) were compared using Friesian cattle grazing Rhodes grass (Chloris gayana) pastures during the dry season from October 1991 to January 1992 at the National Agricultural Research Centre, Kitale. The two locally blended supplements contained 160–180 g CP/kgDM and consisted of mixtures of maize bran, ground maize-on-the-cob, shredded local fish ("omena") and either sunflower seedcake or ground sunflower seeds (with husks); these were offered at a rate of 4 kg/hd/d as feed.

Pasture was grazed by nine Friesian cattle rotated between two paddocks totalling 2.5 ha for 84 days in a 3 × 3 Latin square design replicated thrice. Milk yield and its butterfat (BF) content, and chemical composition of the feed supplements and pasture, were determined. The daily milk yields between treatments A, B and C were 9.9, 10.6 and 10.7 kg/hd (P<0.005); the corresponding BF contents were 4.1, 3.9 and 4.0%, respectively (P<0.005). The results demonstrated the potential of locally blended concentrates in improving milk production during the dry season. These supplements were cost-effective in the area of the study and can therefore be recommended to smallholder dairy farmers who use improved pastures as the main roughage feed to produce milk from Friesian cows.

Introduction

Ruminant livestock in Kenya continue to rely mainly on natural pastures as their source of feed. However, it is recognised that milk production remains low unless animals grazing these forages are supplemented particularly during dry seasons when herbage quality deteriorates. Commercial dairy meal, as a supplement will no longer be affordable by most farmers due to escalating costs and unavailability. The approach to explore the use of locally available ingredients to formulate substitutes to daily meal therefore becomes necessary.

The objectives of the present study was to compare commercial daily meal with on-farm produced supplements on their effect on milk production and composition by Friesian cattle grazing Rhodes grass pasture during the dry season and to further assess the economics of supplementation.

Materials and methods

Animals and management

Nine cows were selected from the general herd based on milk production, lactation number and stage of lactation. The nine cows within 2–4 months of calving from each other, had an average milk yield of 8.2 kg per day over a two-week pre-experimental period. The cows were divided into three treatment groups to which the three experimental concentrate supplements were randomly assigned. Animals were fed the experimental diets for two weeks before the start of the experiment. Individual milk yields for each cow were recorded daily and aliquot samples taken during the last two days of each period for the analysis of milk fat.

Animals were drenched against internal parasites before the start of the experiment and dipped weekly against external parasites.

Diets and feeding

The basal diet consisted of herbage from a Rhodes grass (Chloris gayana) pasture established in 1985. The pasture was mowed in June 1991 after which it was top-dressed with urea (46% N) a month later. Animals grazed rotationally on the 2.5 ha pastures split into two paddocks. Fresh water was available at all times inside the paddocks.

The physical composition (kg/tonne) of the supplements was as follows:

All the ingredients with the exception of daily meal were mixed on a clean or polythene-lined concrete floor using shovels with constant turning to ensure uniform mixing. A mineral mixture comprising of a commercial mineral formula (Baymix maziwa; Wellcome (K) Ltd) fortified with limestone (CaC0₃) in the ratio 9:1, was added during the mixing. The limestone was excavated locally. Mixture of B and C was prepared in 100 kg batches sufficient to last four to six days to avoid any possible moulding or rancidity due to oil-rich fish in the mixtures.

During the experiment, each diet was offered over three 28 days period (1, 2 and 3) each comprising 14 days of adaptation and 14 days data collection. The supplements were offered in two equal portions during the morning and evening milking at a daily rate of 4 kg per head. Samples of the concentrates and pasture were taken twice in each period, dried at 60°C for 72 h, for dry matter (DM) determination, ground through a 1-mm sieve before bulking for subsequent chemical analyses.

Statistical analysis

Data on milk yield and composition was subjected to standard analyses of variance with means compared for statistical differences using the Least Squares Means (LSM) method.

Results

The experiment lasted for 84 days split into three 28-day periods (Periods 1, 2 and 3) during which pasture was sampled for chemical analyses. The mean contents of crude protein, neutral detergent fibre, and minerals (Ca, Mg, P and Na) of the supplements and pasture herbage are shown in Table 1.

Table 1. The mean chemical composition of grazed herbage and supplements offered to cattle (g/kg)¹

1 Based on two samplings each for both supplements and pasture per period.

The results indicate that the NDF content of the herbage increased while CP level declined with advancing maturity of the pasture (Periods 1 to 3). There were no discernible trends in the mineral contents in the pasture herbage whereas locally made supplements had generally higher mineral levels than the commercial daily meal.

Animals in all treatments were generally in good body condition except for one animal which developed lumpy skin disease and was removed from the experiment. A missing data procedure was employed in the statistical analyses.

Although liveweight measurements were not taken, it was observed that animals at the end of the experiment were generally in better body condition than they started particularly those on fishmeal-based supplements.

The effect of supplementation with the three concentrate formulations on milk yield and butterfat BF is presented in Table 2.

Table 2. The mean daily milk yield (kg/hd) and butterfat content (%) for pasture-grazing cattle offered different supplements.

There were no significant differences in milk yield between supplements A and B or between B and C (P>0.05), but supplements C gave significantly higher (P<0.05) milk yield than A. Differences were not significant (P>0.05).

Discussion

Pasture nutritive value and milk yield

Lactating dairy cattle in Kenya continue to rely on natural pastures whose quality and quantity seasonally varies with rainfall availability. During the dry season crude protein levels in the pasture may fall below the 60 g/kgDM required for grazing animals to meet their maintenance requirements (Minson and Milford 1967) due to reduced feed intake and digestibility (Minson 1982). Lower digestibility results in a decline in available energy, protein (Butterworth 1967) and minerals (McDowell 1985).

Table 3. Chemical composition (g/kg DM) and unit cost of ingredients used in formulating the supplements.

1=Based on prevailing retail prices at Kitale (Oct. 1991) and excludes transportation costs.
nd =not determined.

Except for period 1, crude protein (CP) content of pastures (Table 1) were below that recommended for the level of milk production observed (ARC 1980).

The additional nutrients in the three supplements may have stimulated greater forage intake and more efficient rumen fermentation producing the milk levels recorded. It is noted that CP and minerals content in the commercial dairy meal (A) were lower than in the other diets (Table 1) and may partly explain the lower, milk yield.

Small amounts of fishmeal have been shown to significantly increase animal performance, this being attributed to its low nitrogen solubility and a shorter retention time in the rumen; this increases the flow of ammino acids absorbed post-ruminally (Preston and Leng 1987). Its inclusion in the current study was aimed at exploiting this phenomenon. Apart from the high protein levels, it is possible that the synergestic effect of by-pass nutrients from fishmeal could have caused a more efficient use of absorbed nutrients resulting in a higher milk production in fishmeal-containing diets; this being significant for supplement C with the highest level of fishmeal (100 g/kg) over supplement A (Table 2).

Broster et al (1969) showed that feeding a high plane of nutrition in early lactation led to considerable residual effect later in the lactation thus improving total lactation yield.

This is important in view of the low plane of nutrition dairy cattle in the tropics, including Kenya are often exposed to during the long dry periods which culminates in low milk production and poor body conditions. Supplementation during such critical periods is not only beneficial in maintaining high milk production levels but it could also improve the animals reproductive performance.

Economics of supplementary feeding

The economics of feeding the supplements to grazing cattle will depend on the prevailing prices of the ingredients and milk. Data in Table 4 have been drawn to demonstrate the cost:benefit ratios under different price structures for each supplement during the 84-day period. It can be observed that it was economic to supplement pastures with the tree supplements (A, B and C); return per shilling spent on levels (Table 2) and the unit cost of the supplements (see Table 3), it would appear that supplement B would be the most cost-effective since it has a favourably lower cost than the others and mean milk yield is not significantly lower than that obtained from supplement C.

Table 4. Total milk yield and economic analysis data.

1 For yield recorded over the 84-day period.

2 Unit costs of supplements A, B and C are KSh, 5.10, 3.80 and 4.10, respectively, based on unit prices shown in Table 3.

nd: not determined due to missing value for treatment A.

It must be emphasised that the recorded increase on production is that obtained over a lactation period of 12 weeks during a dry period. However, a consideration of the economics of supplementation should at farm level critically assess the cost of mixing, transportation, and other management costs on animals and pastures.

It would, however, appear from the outset that feeding of locally formulated supplements (B and C) was economic at farm level at least within the prevailing prices and within the Kitale environs. Further, the cost of supplementation may be reduced if the farmer produces and/or processes on the farm some of these ingredients such as maize-on-cob meal and sunflower seeds. These supplements are therefore recommended as replacements to the commercial daily meal.

Conclusions

The results from this study have shown that supplementing pasture grazed cattle during the dry season maintained high milk yield. Additionally, diets formulated from local protein and energy ingredients were cost-effective within the prevailing costs and have potential for use as replacement to the conventional dairy meal in maintaining a high milk production in the dry season. These supplements are therefore recommended for grazing practices at least within the Kitale town environs. A strategic feeding of high milk yielders is, however, recommended to make the system even more economically viable. Their use under zero-grazing Napier-based feeding system should also be investigated.

Acknowledgements

The authors wish to express their thanks to the Director, Kenya Agricultural Research Institute, for providing financial assistance, and to the Director, National Agricultural Research Centre, Kitale for the logistic support. Last but not least, the many hours put in technical assistance by Messrs H. Wanyonyi, M. Khatsasili, C. Mulusa and N. Wekulo, and the ability of handling the animals by other supportive staff from the Animal Production Section is gratefully appreciated.

References

ARC (Agricultural Research Council). 1980. Commonwealth Agricultural Bureaux, Slough, London.

Broster W.H., Broster V.J. and Smith T. 1969. Experiments on the nutrition of the dairy heifer. 8: Effect on milk production of level of feeding at two stages of lactation. Journal of Agricultural Science. (Camb). 72:229–245.

Butterworth M.H. 1967. The digestibility of tropical grasses. Nutr. Abstr. Rev. 37:349–368.

McDowell L.R. 1985. Nutrient requirements of ruminants. In: McDowell L.R. (ed), Nutrition of Grazing Ruminants in Warm Climates. Academic Press, Inc. Harcout Brace Jovanivoch Publ.

Minson D.J. 1982. Effects of chemical and physical composition of herbage upon intake. In: Hacker J.B. (ed), Nutritional Limits to Animal Production from Pastures. Commonwealth Agricultural Bureaux, Slough. pp. 167–182.

Minson D.J. and Milford R. 1967. The voluntary intake and digestibility of diets containing different proportions of legume and mature pangola grass (Digitaria decumbens). Aust. J Agric. Anim. Husb. 7:456–551.

Preston T.R. and Leng R.A. 1987. Ruminant Production Systems. Matching Ruminant Production Systems with Available Resources in the Tropics and Sub-tropics. Penambul Books, Armidale, Australia.

Effet de différents compléments protéiques et énergétiques sur la production laitière de vaches Frisonnes élevées sur pâturage

Résumé

Une ration classique pour vaches laitières (A) et deux rations complémentées avec un mélange protéino-énergétique préparées sur place (B et C) ont été comparées sur des vaches Frisonnes élevées sur pâturage de Chloris gayana pendant la saison sèche, d'octobre 1991 à janvier 1992, au Centre national de recherche agricole de Kitale. Ces deux compléments, qui contenaient 160 à 180 g de protéines brutes/kg de MS et étaient composés de son de maïs, d'épis de maïs broyés, de poisson local broyées ("omena") et soit de tourteau de tournesol, soit de graines de tournesol broyées (non décortiquées), étaient offerts à raison de 4 kg/j/animal.

L'essai a été conduit pendant 84 jours sur 9 vaches Frisonnes tournant sur deux parcelles d'une superficie totale de 2,5 ha, selon la méthode du carré latin (3 × 3) avec 3 répétitions. La production laitière et le taux de matière grasse (MG) du lait ainsi que la composition chimique des compléments alimentaires et du fourrage naturel ont été déterminés. La production laitière des animaux recevant les rations A, B et C était respectivement de 9,9 ; 10,6 et 10,7 kg/j/tête (P<0,005) et les taux correspondants de matière grasse de leur lait étaient de 4,1; 3,9 .et 4 % (P<0,005). Ces résultats montrent que les compléments pioduits sur place permettent d'améliorer la production de saison sèche. Ces concentrés étant rentables dans la zone d'étude, on peut les recommander aux petites exploitations qui produisent du lait à partir de vaches Frisonnes élevées sur des parcours améliorés constituent la principale source de fourrage des animaux.