dry matter intake per mouthful by grazing dairy goats

Small Ruminant Research, 7 (1992) 215-223 Elsevier Science Publishers B.V., Amsterdam

215

Dry matter intake per mouthful by grazing dairy goats

E. Peinado-Lucena a, M. S~tnchez-Rodriguez b, A.G. G6mez-Castro b, C. Mata- Moreno b and J.A. Gal lego-Barrera c

a Unidad de Producci6n de Alimentos para el Ganado, Instituto de Zootecnia, C.S.I.C., Avda. Medina Azahara, 9, 14005 C6rdoba, Spain

bDepartamento de Produccibn Animal, Facultad de Veterinaria, C6rdoba, Spain CDepartamento de Producci6n Animal, Facultad de Veterinaria, Murcia, Spain

(Accepted 29 May 1991 )

ABSTRACT

Peinado-Lucena, E., S~inchez-Rodriguez, M., G6mez-Castro, A.G., Mata-Moreno, C. and Gailego- Barrera, J.A., 1992. Dry matter intake per mouthful by grazing dairy goats. Small Rumin. Res., 7: 215-223.

Mouthful grass intake varied widely from season to season, with minimal values in winter (0.09 g DM) that increased to 0.51 g DM in Spring and decreased in Summer (0.21 g DM). Mouthful intake for shrubby species ranged between lowest for Cistus salvifolius (0.16-0.33 g DM) to C. ladanifer (0.95-3.57 g DM), followed by C. albidus (0.33-1.46 g DM). Quercus rotundifolia was the most frequently ingested arboreal species throughout the year, although the maximum DM content per mouthful ( 1.58 g) was for Olea europaea. These results show that the greatest weight per mouthful of grass was in spring. The largest amount of DM on a year-round basis was provided by the shrub C. ladanifer, and the tree O. europaea. Differences in DM intake per mouthful for each species suggest that studies of comparative palatability based on grazing time or number of mouthfuls may lead to errors when estimating actual DM intake for different species studied. Such estimates should be corrected in the light of relative weight per mouthful for each food species.

INTRODUCTION

Feed intake during grazing is controlled by animal and plant factors, their interaction, and management strategies. Sibanda (1984) stressed the importance of pasture density, botanical composition and leaf-to-stem ratio. Partic- ular species, variety, vegetative status, composition and occurrence are also significant according to Morand-Fehr and Sauvant ( 1981 ). Isolating the effects of each of these variables is difficult (Sibanda, 1984). However, it is of interest to determine to what extent goats exploit available resources as the production and yield of these ruminants depends on their voluntary intake levels (Crampton et al., 1960). The value of forage may depend more on the

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216 E. PEINADO-LUCENA ET AL.

amount consumed than on its chemical composition, particularly in goats because of their browsing habits (Haas and Horst, 1977 ).

The purpose of the present study was to determine the amount of dry matter per mouthful obtained by goats in grazing different fodder-groups (grass, shrubs, trees) over one year.

MATERIALS A N D M E T H O D S

A herd of 220 Florida dairy goats, 60 kg BW, was used. Goats were farmed semi-extensively, and received a feed supplement of 0.66 kg barley/d/goat in summer, autumn and winter. Milk production was 432 kg (3.22% protein and 4.84% fat) in 216 d of lactation, and one kid was produced per litter. Goats were 4-8 years old. Since there were three kidding periods (March, September and December), the herd comprised animals at different stages of milk production. Florida is a hypermetric, longilineal and cyrtoid dairy breed native to the Guadalquivir Valley, and located in the province of Seville, where there is an estimated population of 30 000 breeding goats, used primarily for milk and cheese production. One of the main characteristics of this breed is its ability to utilise natural resources and agricultural residues in grazing (S~inchez et al., 1990 ). Feeding behaviour was monitored on one day per week over the whole grazing season, using six adult females previously selected as representative of their herd (Meuret et al., 1985 ). Each animal was observed for a 10-min period. Monitoring began each day with the animal nearest the observer, and continued with the remaining animals at 10-min intervals (the time necessary to locate and approach the animals). When all experimental animals had been monitored once, the process was repeated in two more monitoring shifts, always beginning with the same animal. In this way, monitoring covered 50% of grazing time with three observation periods per animal. The species used and the number of mouthfuls taken were recorded.

The study area was located in the Sierra Norte in the province of Seville (Spain), at 500-700 m above sea level (lat. 37°56'N; long. 5°28 'W). Mean annual rainfall, 800 mm; mean winter temperature 7.5 ° C (minimum - 9 ° C ) and mean summer temperature 22.9 °C (maximum 38 °C ). The area consists of mixed holm oak-cork oak ranges with areas of shrub cover containing abundant Cistus spp. Weight per bite was recorded for all grassy species and for the following woody species: Quercus rotundifolia Lain., Q. suber L., Olea europaea L., Cistus salvifolius L., C. albidus L., C. ladanifer L., Pistacia lentis- cus L. and P. terebinthus L. However, we did not control others such as Q. faginea Lam., Arbutus unedo L., Phyllirea augustifolia L., C. monspeliensis L., C. populifolium L. or Ulex europaeus L. which, though palatable, accounted for rather a small proportion of the goats' diet (less than 0.1%), consistent with earlier findings by Harrington ( 1978 ) and Rios and Riley ( 1985 ), who

DRY MATTER INTAKE PER MOUTHFUL BY GOATS 217

pointed out that, although goats may consume a large variety of species, most of their diet consists of the 3-8 most common species in the grazing area.

Grass Grass intake per bite was quantified by grouping all herbaceous species in

a single class according to Hoppe et al. (1977), Bourbouze (1980) and Bryant et al. (1979, 1980). Weight per mouthful was estimated by manual simula- tion of grazing using the hand clipping method as described by Meuret et al. (1985) by dividing the weight of samples collected at five different places into the number of bites (500). Samplings were carried out with a variable frequency depending on the vegetative status of the grass and the evolution of animal behaviour. A single sample was considered to be representative of November, December and January, and another of July and August. The greater dynamism of the herbaceous stratum and animal grazing compelled us to carry out monthly samplings between January and July. Data were subjected to analysis of variance (Table 1 ).

Twigs Amounts of arboreal and shrubby species ingested by goats were estimated

individually as, unlike herbaceous species, their browsing depends on the vegetative status of the plants. A method was developed based on the marked correlation between twig weight and diameter, which was investigated in our department by Tovar Andrada ( 1978 ) and Martinez Teruel (1984).

Regression equations were fitted for each control on the basis of about 200 weight and diameter measurements by using material of each species collected at the grazing spots. Potential relation was used, because this type was

TABLE 1

Trend in mouthful weights and grass intake rate

Month Ingested dry N u m b e r of N u m b e r of mat ter (g) mouthfuls per mouthfuls per

day minute

Nov. -Dec . - Jan . 0.09 + 0.005 a 1423 + 102.02 a 4.33 + 0.41 a February 0.14 + 0.005 b 1684 + 218.71 ab 4.94 + 0.74 a'b March 0.24 + 0.006 c 4049 + 576.69 ¢ 10.06 + 1.12 c April 0 .43+0.0060 4879+489.94 c 11.11 +0.75 c May 0.51 + 0.005 e 4232 + 221.34 ~ 8.72 + 0.49 c June 0.35 + 0.005 f 2850 + 432.25 b 6.11 + 0.55 b Jul.-Aug. 0.21 + 0.005 g 1254 + 248.46 a 3.35 + 0.62 a

Mean 0.28 + 0.022 2902 + 258.51 6.96 + 0.53

a'b'cSuperscripts when different, denote statistical difference ( P < 0.001 ) between months .

218 E. PEINADO-LUCENA ET AL.

the most accurate in accounting for weight-diameter relations in all species and control dates, consistent with findings by Rumble (1987).

Stem diameter at the biting point (DBP) as an independent variable in the fitted regression equations for each ligneous species and sampling season were used to calculate weight of a mouthful. DBPs were obtained for each control by a group of observers who followed the herd and measured diameters of browsed stems according to directions given by Tovar Andrada (1978). In both cases, diameters were measured to within 0.05 mm with a slide calliper and weights to within 0.01 g on an electronic balance. Data were subjected to variance analysis (Table 2 ).

R E S U L T S A N D D I S C U S S I O N

Herbaceous material Table 1 reflects the trend in the amounts of dry grass matter ingested per

mouthful. There was a marked seasonal variation, with minimal values during the winter (0.09 g DM), which increased until May (0.51 g DM) and again decreased in summer (0.21 g DM). Average weight of grass mouthfuls estimated for the entire experimental period was 0.28 g DM.

There is little information available in this respect and most data are for sheep, for which Black and Kenney (1984) found 0.04 g DM under conditions of scarce grazing resources and 0.20 g DM under most favourable conditions, i.e. about half the values found in this work in both cases. Allden and Whittaker (1970) found an average 0.08 g DM ingested by sheep in each mouthful, which is consistent with our findings under the lowest herbaceous availability. However, Hodgson ( 1985 ) reported larger figures, more similar to those found by us for goats of 0.13 g DM under conditions of scarce herbaceous resources, equivalent to the results of February, and 0.45 g DM under most favourable conditions (similar to April values). Likewise, Seip and Bunnell (1985) estimated an average mouthful size of 0.08 g DM in Stone mufflons in Canada, which is consistent with our results under low availability conditions. In goats, Yoshimoto et al. (1985) found 0.47 g DM per mouthful under subgrazing conditions, which is similar to our results under conditions of greatest availability (0.43-0.51 g DM, Table 1 ).

According to the literature, mouthful size increased with the amount of available herbaceous material. This was particularly noticeable in May, co- inciding with greatest availability of grass (Table 1 ). However, afterwards, the amount of grass ingested per mouthful decreased until August, which can be ascribed to a gradual increase in selectivity as grass dries, that ends with the exclusive selection of some parts of the plants which are fully developed by then.

As increasing availability allows for selective grazing, it must also result in greater quality and weight of ingested pasture, which has been demonstrated


in intensive grazing (Arnold and Dudzinski, 1966; Greennhalg et al., 1966), and probably bears the same significance under extensive conditions, although there are no conclusive studies in this respect.

According to Allison ( 1985 ), when the amount of available pasture changes, the animal alters its grazing time, mouthfuls per minute and amount ingested in each mouthful in order ot keep a balance in its intake level. Likewise, a number of researchers (Langlands and Bennet, 1973; Young and Newton, 1974; Marsh, 1977; Baker et al., 1981 ) found availability and intake to be highly correlated. However, Seip and Bunnell ( 1985 ) noted opposite trends. This is consistent with our results (Table 1 ): the number and size of the mouthfuls and their frequency per minute increased from November to April as the palatability and availability of grass also increased. However, number of mouthfuls started to decrease in May, and mouthful size, decreased from June as grass dried and lost its palatability, even though ripe grass was still widely available.

The correlation was highly positive and significant between DM ingested per mouthful and number of mouthfuls per minute ( r= 0.70, P < 0.05, maximum error probability=0.013); DM ingested per mouthful and number of mouthfuls per day ( r = 0.83, P < 0.001, maximum error probability = 0.01 ); and number of mouthfuls per minute and number of mouthful per day ( r= 0.9, P < 0.001, maximum error probability = 0.001 ), which contradicts earlier re- ports by other authors on the compensation for low availabilities through the number of mouthfuls.

Thus grass availability may be the limiting factor of size and number of mouthfuls during the plant development period and until ripening, after which it is displaced by palatability.

Ligneous species The amount of ligneous species ingested per mouthful varied within species

throughout the year (Table 2). The literature offers few data for contrast on the species studied here as it only deals with trees of the Quercus genus. Esti- mations for cork and holm oaks are of the same order as those found for Q. pubescens (0.88-1.68 g DM) by Meuret et al. ( 1985); (0.64-1.03 g DM) by Rosenberger and Meuret (1985); for Q. ilex (0.35 g DM) by Bourbouze (1980); and (0.81-0.93 g DM) by Meuret et al. (1985), with exceptions arising from the more limited samplings conducted by these authors.

As far as other shrubby species are concerned (Table 2), mouthful size showed variations probably arising from the plant itself (Rosenberger and Meuret, 1985) and ranged between lowest values found for C. salvifolius (0.16-0.33 g DM) to those of C. ladanifer (0.95-3.57 g DM) and the maxi- mal of C. albidus ( 1.46 g DM) and O. europaea ( 1.58 g DM) on some dates. Figures for Quercus were always smaller than the 1.68 g DM recorded for Q. pubescens by Meuret et al. ( 1985 ).

2 2 0 E. PEINADO-LUCENA ET AI_

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In summary, taking into account average values (Table 2), C ladanifer yielded the largest weights of DM per mouthful (2.54 g DM) , followed by O. europaea ( 1.14 g DM) and C albidus ( 1.05 g DM) , while C salvifolius was the least palatable species, with no seasonal difference in its weight per mouthful (average 0.25 g DM). Quercus spp. (rotundifolia and suber) fea- tured similar consumptions (0.69 and 0.74 g DM, respectively), with no statistical significance except in September, were Q. suber was ingested in greater amounts per mouthful ( 1.21 g DM). Pistacia terebinthus, the only deciduous species studied, was only usable during the summer, when it was avidly consumed by the goats, so much so that it was a quarter of all ligneous species analysed (0.84 g DM ). Hence, its palatability and nutritional value justify its use and spread as a rather interesting grazing contribution in areas where resources are scarce during the summer.

The availability of grass and woody species was a factor affecting DM intake per bite. This, as well as indicating the palatability of the different species, suggests that studies of comparative palatability based on grazing time or number of bites may lead to errors when estimating the importance of the different species used (measured in terms of real contribution to DM intake). Such estimates should be corrected in the light of relative weight per mouthful for each species.

REFERENCES

Allden, W.G. and Whittaker, I.A., 1970. The determinants of herbage intake by grazing sheep: The interrelationships of factors influencing herbage intake and availability. Aust. J. Agric. Res., 21: 755-766.

Allison, D.C., 1985. Factors affecting forage intake by range ruminants: A review. J. Range manage., 38:305-31 I.

Arnold, G.W. and Dudzinski, M.L., 1966. The behavioural responses controlling the food intake of grazing sheep. Proc. XI Int. Grassld. Cong. Finland, Helsinki, p. 367-370.

Baker, R.D., Le, Du, Y.L. and Alvarez, F., 1981. The herbage intake and performance of set- stocked suckler cows and calves. Grass Forage Sci., 36:201-210.

Black, J.L. and Kenney, P.A., 1984. Factors affecting diet selection by sheep. II. Height and density of pasture. Aust. J. Agric. Res., 35: 565-578.

Bourbouze, A., 1980. Utilisation d'un parcours forestier p/lture par des caprins. (Utilization of one woodland pasture plot by caprines). Fourrages, 82:121-144.

Bryant, F.C., Kothmann, M.M. and Merrill, L.B., 1979. Diets of sheep, Angora goats, Spanish goats and White-tailed deer under excellent range conditions. J. Range Manage., 32:412- 417.

Bryant, F.C., Kothmann, M.M. and Merrill, L.B., 1980. Nutritive content of sheep, goat and White-tailed deer diets on excellent condition rangelands in Texas. J. Range Manage., 33: 410-414.

Crampton, E.W., Donefer, E. and Lloyd, L.E., 1960. A nutritive index for forages. J. Anita. Sci., 19: 538-544.

Greennhalgh, J.F.D., Reid, G.W., Aitken, J.N. and Florence, E., 1966. The effects of grazing

222 i~ PEINADO-LUCENA ET AL.

intensity on herbage consumption and animal production. I. Short-term effects on strip-grazed dairy cows. J. Agric. Sci., 67: 13-23.

Haas, H.J. and Horst, P., 1977. The significance of goat production for covering the protein requirements in developing countries. Federal Ministry of Economic Cooperation. Bonn, pp. 105.

Harrington, G., 1978. The implications of goat, sheep and cattle diet to the management of an Australian semi-arid woodland. Proc. First Int. Rangeland Congr., p. 447-450.

Hodgson, J., 1985. The control of herbage intake in the grazing ruminant. Nutr. Soc., 44: 339- 346.

Hoppe, P.P., Qvortrup, S.A. and Woodford, M.H., 1977. Rumen fermentation and food selection in East African sheep, goats, Thomson's gazelle, Grant's gazelle and Impala. J. Agric. Sci. Camb., 89: 129-135.

Langlands, J.P. and Bennett, I.L., 1973. Stocking intensity and pastoral production. II. Herbage intake of Mexico sheep grazed at different stocking rates. J. Agric. Sci., 81: 205-209.

Marsh, R., 1977. The effect of level of herbage dry matter per animal on efficiency of utilization of pasture by young Friesian cattle. N. Z. Soc. Anim. Prod., 37: 62-66.

Martinez Teruel, A., 1984. Aportaciones al estudio de la biomasa arbustiva y arb6rea del pasti- zal arbustivo meditemineo. (Notes on the study of shrub and tree biomass in Mediterranean shrub pastureland). Ph.D. Thesis, Fac. Vet. Univ. C6rdoba, pp. 314-80.

Meuret, M., Bartiaux-Hill, N. and Bourbouze, A., 1985. I~valuation de la consomation d'un troupean de ch~vres laitieres sur parcours forestier. M6thode d'observation directe des coups de dents. M6thode du marquer oxyde de chrome. (Assessment of intake by a herd of dairy goats grazing woodland pasture. Direct observation of bites taken. Chromium oxide labell- ing). Ann. Zootech., 34:159-180.

Morand-Fehr, P. and Sauvant, D., 1981. Caprino. In: R. Jarrige (Editor), Alimentaci6n de los rum iantes (Caprine. In: Feeding of ruminants ): 485-504. INR. Ed. Mundi Prensa, Madrid, pp. 697.

Rios, G. and Riley, J.A., 1985. Preliminary studies on the utilization of the natural vegetation in the Henequen zone of Yucatan for the production of goats. 1. Selection and nutritive value of native plants. Trop. Anim. Prod., 10: 1-10.

Rosenberger, S. and Meuret, M., 1985. Un histoire de coups de dents. (Bites: a case history). La Ch~vre, 151: 21-27.

Rumble, M.A., 1987.; Using twigs diameters to estimate browse utilization on three shrub species in southeastern Montana. Proc. Symp. Plant-Herbivore Interactions. p. 172-1785.

Sfinchez, M., Herrera, M., S6nchez, J.A. and Alvarez, J.J., 1990. Descripei6n de una nueva raza caprina (Florida Sevillana ). (Description of a new breed of goat: (Florida Sevillana ). Proc. Simp. Int. de Explotaci6n caprina en zonas ~iridas. 23-26 obtubre 1990. Coquimbo, Chile Terra Arida, T. Summary: 23.

Seip, D.R. and Bunnell, F.L., 1985. Foraging behaviour and food habits of Stone's sheep. Can. J. Zool., 63: 1638-1646.

Sibanda, M., 1984. Factors affecting intake of herbage by grazing ruminants. Zimbabwe Agric. J., 81: 65-70.

Tovar Andrada, J., 1978. Estudio experimental de la medida de la producci6n forrajera arbustiva. (Experimental study of shrub forage production measurements). BSc Thesis, Fac. Vet. Univ. C6rdoba, pp. 230.

Yoshimoto, T., Sakaue, Y. and Kawakami, M., 1985. The feeding behaviour of grazing livestock in the forest and effect of grazing on light condition in the forest floor. Bull. Hiroshima Agric. Coll., 7: 467-475.

Young, N.E. and Newton, J.E., 1974. A note on the intake of lactating ewes at pasture. J. Br. Grassld. Soc., 29:117-119.


RESUMEN Peinado-Lucena, E., S~tnchez-Rodriguez, M., G6mez-Castro, A.G., Mata-Moreno, C. and Ga-

llego-Barrera, J.A., 1992. La ingesti6n de materia seca pot bocado durante el pastoreo en un rebafio de cabras de aptitud lechera. Small Rumin. Res., 7:215-223.

Se estudia la evoluci6n de la materia seca por bocado de hierba, arbustivas y arb6reas, en un rebafio caprino de aptitud l~ictea. Se observa una amplia variaci6n estacional en la hierba, con valores minimos en invierno (0.09 g de m.s.), que se incrementa en primavera (0.51 g de m.s.), para descender en verano (0.21 g de m.s.). En las arbustivas, el tamafio de los bocados oscila des de los m~is bajos, en Cistus salvifolius (0.16-0.33 g de m.s. ), hasta los de C ladanifer (0.95- 3.57 g de m.s. ), seguido de C albidus (0.33-1.46 g de m.s.). En las arb6reas, Quercus rotund# folia presenta la mayor regularidad en el consumo a 1o largo del afio, pero es en Olea europaea donde se observan los valores m~iximos de materia seca por bocado ( 1.68 g de m.s.). Estos resultados ponen de manifiesto que el mayor peso por bocado, en la hierba, se produce en primavera, como consecuencia de la mayor disponibilidad herb~lcea. Entre los arbustos y durante todo el afio, la especie C ladanifer es la que aporta mayor cantidad de materia seca a la dieta de la cabra, y entre las arb6reas, O. europaea. Las diferencias en la cantidad de materia seca inge- rida por bocado para cada especie, pone de manifiesto que los estudios de apetecibilidad com- parativa, basados en la consideraci6n de los tiempos de pastoreo o del n6mero de bocados, puede generar errores en la estimaci6n de la ingesti6n real de materia seca, en las distintas es- pecies estudiadas, por 1o que dichas observaciones deber:tn ser corregidas en funci6n de los pesos relativos pot bocado de cada especie.

dry matter intake per mouthful by grazing dairy goats

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