Milk production in Sokoto Gudali cows fed legume or elephant grass ensiled with cassava peel

O A Olorunnisomo

Department of Animal Science, University of Ibadan, Ibadan, Nigeria
sholanissomo@yahoo.com

Abstract

Low protein levels in grass-based pastures pose a serious limitation to milk production in many tropical areas. High protein legume silage fed to dairy cattle holds potential for improving milk production in these areas. This study compares milk production and feed conversion efficiency by Sokoto Gudali cows fed silages made from leuceana, gliricidia, enterolobium forages and elephant grass mixed with 50% of cassava peel on a wet basis. Intake, milk yield and feed conversion ratio of four primiparous cows fed different silages were determined in 84 days using a Latin square design.

Protein content of silages varied from 6.7 – 17.1% with legume silages having significantly higher (p < 0.05) values than grass silage. Dry matter (DM) intake of silages ranged from 2.29 to 4.40% of body weight with grass silage having the highest value. Milk yield was 4.31, 5.19, 4.70 and 2.84 kg/d while feed conversion ratio was 2.63, 1.94, 1.78, and 2.09 for cows fed elephant grass, leuceana, gliricidia and enterolobium silage respectively. With the exception of enterolobium treatment which gave lower milk yield than grass silage, legume silages improved milk yield and feed conversion efficiency in zebu cattle.

Key Words: enterolobium, gliricidia, leuceana, silage, zebu cattle

Introduction

The rising demand for milk and its products in Nigeria has made it imperative to find means for increasing local milk production. The traditional dairy subsector is dominated by indigenous cattle breeds whose potential for milk production is largely underexploited. Zebu cattle are by far the most common cattle type found in Nigeria and they provide the bulk of locally produced milk (RIM 1992). Milk production from these animals is low with lactation yields varying from as low as 295 to 650 kg under extensive management, and 800 to 1300 kg with high nutrient intake (Ngere 1985, Das 1999, Boly et al 2001, Bayemi et al 2005, Yilma et al 2006, Idris et al 2011). Although opinions differ on the genetic potential of zebu cows for milk production, high yields of 1183 - 2585 kg/lactation from the Sahiwal breed (Bajwa et al 2004, Zafar et al 2008, Dongre et al 2011) indicates that zebu breeds can be managed for higher milk production with proper selection, adequate nutrition and improved management practices. 

The management system adopted by most farmers in Nigeria is the extensive system where cattle are grazed on poorly managed native pastures. Native pastures in Nigeria are grass-dominated and nutritional problems encountered by zebu cattle are associated with low protein intake, poor digestibility of tropical grasses and scarcity of forage during the dry season (Crowder and Chedda 1982, Adamu et al 1993, Pamo and Pieper 2000). The resultant effect is that grazing cattle are unable to meet their protein and energy needs from pasture, leading to low milk production among these animals. Since scarcity of forage during the dry season poses a serious limitation to cattle production, ensiling excess forage during the wet season will enhance productivity of these animals on a year-round basis.

Legume forages have higher protein content than grass and have greater potential to improve nutrition of grazing animals (Wilkins 2001). Use of legumes as silage materials is expected to improve protein supply to milking cattle. However, tropical grasses and legumes often make poor silage due to low levels of water soluble carbohydrates and high buffering capacity of legume forages. This makes rapid reduction of pH in the ensiled material difficult (Gallaher and Pitman 2001, Wilkins 2001). Addition of cassava peels, a cheap source of readily fermentable carbohydrate in Nigeria, has been shown to improve the ensiling quality of tropical grass and legumes (Olorunnisomo 2011, Olorunnisomo and Fayomi 2012).  This study aimed at evaluating the intake, milk yield and milk composition of zebu cattle fed legume or elephant grass ensiled with cassava peels.

Materials and methods

The experiment was conducted at the Dairy Unit of the Teaching and Research Farm, University of Ibadan, Ibadan, Nigeria (3º45´E, 7º27´N; at 220m above sea level). Annual rainfall ranges from 1150 - 1500mm.

Preparation of silage 

Three legume forages (Leucaena leucocephala, Gliricidia sepium, Enterolobium cyclocarpum) cut at 16 weeks of age and elephant grass cut at 10 weeks were wilted for 24 hours and chopped to 3cm lengths using an automated forage chopper. Chopped forages were mixed with equal proportions of cassava peel on a wet basis. The mixtures were compacted inside 120 litre plastic drums, sealed with polythene sheets, weighted with a sand bag and covered with plastic lid for the milk production study.

Photo 1. Silage being compacted	Photo 2. Silage in 120L plastic drums

Treatments

Treatments corresponded to the following experimental diets:

• Leuceana forage ensiled with 50 % cassava peels (LC)

• Gliricidia forage ensiled with 50 % cassava peels (GL)

• Enterolobium forage ensiled with 50 % cassava peels (ET)

• Elephant grass ensiled with 50% cassava peels (EG)

Silage examination and laboratory analysis 

At 21 days, samples of silage were taken for proximate composition using the general procedures of AOAC (2005). DM concentration in the silage was determined using a forced draught oven at 65^oC and values obtained were corrected for loss of volatile compounds by multiplying with the correction factor of 1.056 (Fox and Fenderson, 1978). Detergent fibre components were determined according to methods of Van Soest and Robertson (1985).  

Milk production study 

Four primiparous Sokoto Gudali cows weighing between 285 and 346 kg were used for the milk production trial using a Latin Square design. All cows had calved within one month of each other. They were housed in individual pens and fed one of the four experimental diets for a period of 21 days after which they were switched over to the  next diet for another 21 days such that at the end of 84 days all animals had been placed on each of the four diets. Seven days were allowed for adjustment to the new diet at switch-over periods and experimental measurements were taken within 14 days. Animals were exercised daily by walking to the milking shed which was situated at 100m from the experimental shed. Silages were offered twice daily (ad libitum) while concentrate was offered once daily during milking. Silage intake was measured by deducting remnants from the quantity served. Fresh water was offered free choice on a daily basis.

Photo 3. Sokoto Gudali cow	Photo 4. Stimulating milk let-down

Milking was done by hand twice daily at 7am and 4pm in the presence of the calf. Milk let-down was stimulated by the suckling the calf for 5 minutes after which the cow was milked. Weight of the calves was taken before and immediately after suckling to estimate milk intake by the calf. Calves were separated from cows after milking and part of the milk collected was fed back to the calves using a nipple-bottle. Milk yield was calculated as the summation of milk off-take and intake by the calf.

Photo 5. Hand milking of cow	Photo 6. Calf feeding from bottle

Experimental design/statistical analysis 

The experimental design adopted for this study was the Latin Square design. Data obtained were subjected to analysis of variance and significant means were separated by Duncan’s multiple range tests using the procedures of SAS (1995). 

Results and Discussion

The physical characteristics and pH of legume and elephant grass silages at 21 days of ensiling are summarized in Table 1. Physical attributes of these silages and effects of cassava peel addition have been reported previously (Olorunnisomo and Fayomi 2012).  

Dry matter content of enterolobium and leucaena silage was higher than that of elephant grass and gliricidia silage (Table 2). Gliricidia silage had the least DM content while enterolobium had the highest. As expected, crude protein contents of legume silages were higher than that of grass silage. Among the legume silages, leucaena had the highest protein content while enterolobium had the least. Fibre and ether extract were higher in grass than legume silages. From the chemical composition, legume silages showed a clear advantage over elephant grass silage in terms of CP while there were only slight differences in CP levels among legume silages (leucaena > gliricidia > enterolobium), however, values for ether extract and nitrogen free extract indicate that grass silage may have higher concentration of available energy than legume silage.

The cows consumed more grass silage than legume silage (Table 3). This agrees with earlier observations (Olorunnisomo and Fayomi 2012) that zebu cattle prefer grass silage to legume silage. Protein intake by the cows was, however, higher from legume silage than grass silage.

Highest milk yield was recorded when cows were fed leucaena silage (LC) and least when fed enterolobium silage (ET). Except for ET, milk yield was higher when cows were fed legume silages than grass silage. The lower milk yield from ET was mainly due to the lower DM intake of cows when ET was offered. The sharp and pickled smell of enterolobium forage had an adverse effect on the intake of cattle consuming this forage as observed by Olorunnisomo and Fayomi (2012). Milk yield appeared to be a response to increased intake of DM and protein. Although DM intake was highest for EG-CSP, protein intake was highest for LC-CSP. Since DM intake also represents energy intake, the higher milk yield observed in LC than in EG supports the conclusion by Preston and Leng (2009) that the protein: energy ratio in cattle diets may have greater influence on milk yield than total DM intake.

Among the legume silages the feed conversion ratio was best for gliricidia and poorest for enterolobium silage. In spite of the apparent aversion of cows to enterolobium silage, feed conversion was still better for this silage than elephant grass silage. This shows that legume silage with addition of appropriate fermentable carbohydrate has greater potential than grass silage for producing milk economically.

Total solids, fat and lactose content of the milk was higher when grass ensiled with cassava peel was fed to the cows compared to those fed legume silage (Table 4) . This was expected since fat and NFE levels which represent energy components of the feed were higher in grass silage than legume silages.    Cows fed legume silages had higher protein in their milk compared to those fed grass silage, which could be related to the higher protein content of the legume silages. There were no differences among legume silages in milk composition.

Conclusions

• Legume silages had higher protein but less energy components than elephant grass silage.
  
  
• Feed intakes were highest on grass silage and lowest on the silage made with enterolobium.
  
  
• Milk yield and feed conversion were best on the silages made with leucaea and gliricidia. Poorest results were with enterolobium silage

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Received 7 April 2013; Accepted 10 May 2013; Published 2 June 2013

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