Addition of alfalfa (Medicago sativa L.) to lamb diets enhances production and profits in northern China

Y Rong, F Yuan and D A Johnson¹

Department of Grassland Science, Animal Science and Technology College, China Agricultural University, Beijing 100193, China
rongyuping@cau.edu.cn
¹ USDA-ARS, Forage and Range Research Lab, UALF-100 State University, Logan, UT 84322-6300, USA

Abstract

The agro-pastoral transitional zone of northern China is an ecologically fragile area with a short growing season and extensive livestock production, where feed shortage is a key constraint to ruminant production, especially in winter. This study was conducted to evaluate the effects of various ratios of grass hay/crop straw and alfalfa (Medicago sativa L.) hay on lamb growth, feed intake, nutrient digestibility and economics of lamb production. Twenty five three-month-old local cross breed male lambs with initial body weight (IBW) of 23.22 ± 0.41 kg (mean ± SD) were blocked into five groups based on IBW and randomly assigned to diets with various proportions of alfalfa and grass hay/crop straw, including 0:100 (ALF-0), 25:75 (ALF-25), 50:50 (ALF-50), 75:25 (ALF-75) and 100:0 (ALF-100).

Lambs fed alfalfa had higher intake of dry matter (DM), organic matter (OM), crude protein (CP) and fiber than lambs fed only grass hay/crop straw. Average daily gain (ADG) was greatest in lambs fed a diet mixture of 75:25 alfalfa and grass hay/crop straw. Total profit per lamb was also highest with the 75:25 mixture ($27.77), which was 67 % higher than lambs fed only grass hay/crop straw. Given the current cost of alfalfa in northern China and the ADG gains that can be achieved with the addition of alfalfa to lamb diets, it is recommended that household lamb producers in northern China feed their lambs with diets containing 375 g/kg alfalfa to achieve higher profits compared to feeding only grass hay/crop straw.

Keywords: average daily gain, digestibility, feed conversion rate, grass hay, lamb feedlot

Introduction

The agro-pastoral transitional zone of northern China covers 654,564 km² (Zhao et al 2002), has a human population of 41,254,700 and is home to 60% of the livestock population in northern China (China Livestock Statistical Yearbook 2011). Green forage is only available during a short growing season of 3 to 4 months in summer. The remainder of the year from autumn through spring is a long, dry and cold period, which necessitates that fodder be stored for winter use (Kemp et al 2011). Animal losses during winter are typically high in this region because of a lack of feed (Kemp et al 2011). Traditional livestock management practices are often based on survival through the year rather than optimum strategies for market production and economics. Perennial forage and annual forages have been introduced because of large fluctuations in annual cereal production (Lv and Zheng 2009). Alfalfa (Medicago sativa L.) has been recommended for use in feeding animals in this agro-pastoral transition region during winter (Li et al 2007); however, data documenting the effect of alfalfa on animal diets are not available for this region of China. 

Many previous studies have indicated that deficiencies in nitrogen (N), energy or minerals in grass hay/crop straw can be overcome by adding high quality forage to animal diets (McAllan et al 1994; Haddad 2000; Bhatti et al 2008; Feyera and Animut 2011). Addition of alfalfa to low-quality diets has been shown to enhance intake and digestibility (Paterson et al 1982; Hunt et al 1985; Brandt and Klopfenstein 1986a) and animal gain (Brandt and Klopfenstein 1986b). Previous studies concerning the addition of alfalfa to animal diets in northern China have not evaluated the amounts of alfalfa required in the diet to optimize animal performance and economic gain, which is key for livestock production of small households in this region of China.

The objective of this study was to examine the effects of adding various ratios of alfalfa hay to low quality grass hay/crop straw diets and determine its subsequent effects on feed intake, digestibility, live-weight gain and profits for lambs in northern China. The ultimate goal is to help small households improve lamb production in this harsh environment and enhance farmers’ livelihoods.

Materials and methods

Study site

The study was conducted on a typical household sheep farm in Fengning County of Hebei Province in northern China (116.3959°46′ E, 41.8035° N, elevation = 1,302 m). This region has a semi-arid climate with an annual precipitation of 300 to 400 mm of which 60 % falls during June to August. Summer temperatures are warm with very cold winters, and the annual mean temperature is 1℃. Mean temperature in January is -18.6 and in July is 17.6°C. Mean annual evaporation is 1,736 mm, which is more than four times annual precipitation. The average length of the frost-free period is 85 to 95 days.

Animals and feed

Twenty-five three-month-old male lambs (Mongolia sheep and small-tail sheep cross breed) were used with an average live-weight (LW) of 23.22 ± 0.41 kg. The lambs were ear tagged and treated against internal and external parasites. A total of 25 feed troughs (made of barrels) were used to feed the lambs. Lambs were housed in sheds that had a cement floor, a roof and one sidewall with no temperature control. The experiment was conducted from 10 Nov. 2011 to 15 Jan. 2012. Ten days were allowed for animal adaptation with the next 56 days for data collection.

The concentrate in the basal diet was purchased from the local market and is widely used for diet supplementation during winter in this region. The maize (Zea mays L.) silage, grass hay/crop straw and alfalfa hay were produced by the household farm. The hay used in this study was air-dried and chopped to about a 5 to 8 cm length before feeding.

Experimental design

The experiment was a complete randomized design with five groups of five lambs each that were randomly grouped based on overnight fasting live-weight, which represented the replications or blocks of the experiment. Each lamb group was randomly placed into one of the five diet treatments that included various ratios of alfalfa and grass hay/crop straw, including total grass hay/crop straw (ALF-0), 75% grass hay/crop straw with 25% alfalfa hay (ALF-25), 50% grass hay/crop straw with alfalfa respectively (ALF-50), 25% grass hay/crop straw with 75% alfalfa hay (ALF-75) and total alfalfa hay (ALF-100) (Table 1).

Feeding management

The basal diet (concentrate plus silage) was offered daily in 2 equal portions at 0800 and 1700. The experimental diet treatments of hay feed (grass hay/crop straw and/or alfalfa hay) was mixed based on the ration and offered four times a day. Lambs had ad libitum access to water and mineral blocks with a mineral content that was 3.5, 0.07, 138.7 and 0.8 g/kg for Ca, P, Na and Mg, respectively, and 109.9, 4.8 and 57 mg/kg, for Fe, Cu and Mn, respectively.

Live-weight, digestibility, and intake

The digestibility study was divided into three phases with 14 days each and 7 days were for adaptation to bags and harnesses and 7 days for faecal data collection. Throughout the experimental period, the amounts of feed offered and correspondingly refused were weighed for each lamb and recorded from 0800 to 1500. Samples of feed were taken on batches of feed offered. Samples were also taken daily from basal feed refused, pooled per treatment and thoroughly mixed and sub-sampled at the end of the experiment for chemical analysis. The daily dry matter (DM) intake (DMI) and nutrient intake of each lamb was determined by the difference between initial diet offered and the corresponding amount refused. Live weights were recorded before the morning feed was offered. Average daily gain (ADG) was calculated as the difference between initial and final body weights divided by the number of feeding days. Feed Conversion Rate (FCR) was calculated by dividing daily DMI by ADG. Fecal output for each lamb was determined by collecting feces in fecal bags daily at 0700 and 1700 during each digestibility period. The fecal samples were pooled by animal and period, thoroughly mixed and sub-sampled for weekly composite fecal samples. The apparent digestibility was calculated as the difference between the amount of feed ingested and fecal weight divided by the amount of ingested feed.

Chemical composition

Samples were oven-dried at 65^oC for 72 h and ground through a 1-mm screen for chemical analysis. DM, ash and N were analyzed according to the procedures of AOAC (2000). The CP content was calculated by multiplying N content by 6.25. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were analyzed according to the method of Van Soest and Robertson (1985).

Statistical analysis

Tests for normality and constant variance were conducted on all data using the Kolmogorov–Smirnov Test. Repeated measure analysis of variables (RMANOVA) in SAS general linear model (GLM) was performed to test the effects of diet composition on feed intake, digestibility and live-weight gain using Type III sum of squares (SAS, 2001). Tukey’s Studentized Range (HSD) Test for multiple comparisons was used with P=0.05.

Results

Chemical composition of grass hay/crop straw and alfalfa

The DM, ash, OM, NDF and ADF contents of grass hay/crop straw and alfalfa hay were similar (Table 2). The CP content of alfalfa was significantly higher (P<0.05) than that of grass hay/crop straw.

DM and nutrient intake

The intake of DM, OM and ADF exhibited the same general trend among the five diet treatments (Table 3) in order ALF-75> ALF-100 > ALF-50> ALF-25> ALF-0. The intake of CP was highest in ALF-100 and consistently decreased as proportion of alfalfa decreased in the diet.

Body weight change and FCR

Initial body weights of lambs were similar (P>0.05) among treatments (Table 4). Replacement of grass hay/crop straw with alfalfa significantly improved final body weight, total live-weight gain and ADG (P<0.05). Lambs with a diet of 75% alfalfa (ALF-75) achieved the highest body weight compared to other diets. Total gain and ADG were highest for ALF-75 compared to those for ALF-100, ALF-50, ALF-25 and ALF-0 (P<0.05), while there were no significant differences between ALF-100 and ALF-50 as well as ALF-25 and ALF-0 (P>0.05). The FCR was lowest for lambs in ALF-75, but was not different for lambs fed the ALF-25, ALF-50 and ALF-100 diets (P>0.05). The highest FCR was observed for the ALF-0 diet, which was 47% higher than that of ALF-75 (P<0.05).

DM and nutrient digestibility

Digestibilities of DM, OM, CP and NDF increased with the addition of alfalfa in the diet (P<0.05) (Table 5). The highest digestibilities of DM, OM, CP and NDF were observed in ALF-75, while the lowest was observed in ALF-0 (P<0.05). No significant differences for DM digestibility were observed between ALF-50 and ALF-75, but both were significantly higher than ALF-0, ALF-25 and ALF-100 (P>0.05). The digestibility of OM was in order ALF-75> ALF-50> ALF-25> ALF-100 > ALF-0, with no significant difference between ALF-50 and ALF-75, and between ALF-0 and ALF-100 (P>0.05). The digestibility of CP did not differ among ALF-50, ALF-75 and ALF-100, but these diets were all significantly higher than ALF-0 and ALF-25. The digestibility of NDF was in order ALF-75> ALF-50> ALF-100 > ALF-25> ALF-0 with no significant difference between ALF-25 and ALF-100. The digestibility of ADF was significantly higher in ALF-0 and ALF-25 than in the other three diets, with the lowest value (0.354) in ALF-100 (P<0.05).

Economic evaluation

Economic evaluation of lamb production for the five diet treatments revealed that feed cost increased with increasing amount of alfalfa in the diet (Table 6). Body weight gain increased from ALF-0 to ALF-75 and then decreased in ALF-100. Total profit per lamb was greatest with the ALF-75 diet at $27.77 per lamb, which was $11.11 per lamb more than ALF-0. However, feed cost/kg gain of the five diets did not show a consistent increase with increasing alfalfa. The highest feed cost/kg gain was observed in ALF-100, while the lowest values were for ALF-0 and ALF-75, both of which were lower than the other three diets. The highest profit/kg gain ($2.83) was in ALF-0 followed by ALF-75 ($2.78), ALF-25 ($2.74), ALF-50 ($2.67) and ALF-100 ($2.43). When evaluating total profit, diets containing alfalfa had higher total profit with the highest profit observed in ALF-75 ($27.77), which was 67 % higher than the profit for the traditional lamb diet (ALF-0, $16.66).

Discussion

DM and nutrient intake

To increase DM intake and digestibility of poor quality forage in lambs, the number or activity of rumen micro-organisms need to be increased to maximize fiber digestion and optimize microbial protein synthesis (Leng 1990; Bhatti et al 2008). However, this process needs sufficient protein, energy and minerals to support the rumen microbial population (Silva and Ørskov 1988). In ruminants fed crop residues or grass hay, intake is relatively low due to their high fiber and low CP content, and nutrients are typically not sufficient to meet animal maintenance requirements (Leng 1990; Savadogo et al 2000). Thus, supplementation with crop residues or forages with higher levels of CP (such as alfalfa) is required. To substantively increase productivity above maintenance, both digestibility and CP supplementation are needed (Nsahlai et al 1998). In this study, alfalfa hay produced by the household farm was supplied to replace grass hay/crop straw (rich in fiber, but low in CP) to meet lamb maintenance requirements (fig. 1). Alfalfa was used to increase the CP content of diets and overcome ruminal N deficiency (Leng 1990), and provide available fermentable fiber (Ørskov et al 1999).

In our study, intake of DM, OM, CP and fiber improved with increasing levels of alfalfa in the diet. Similarly, Hunt et al (1988) found that intake of DM linearly increased with increasing proportions of alfalfa with tall fescue [Schedonorus arundinaceus (Schreb.) Dumort] in the diet when lambs were fed ad libitum. Cherney et al (1990) also reported the interaction between level of intake and forage source for OM and NDF across a variety of lamb diets. The improvements of DM and nutrient intake are presumably limited by CP intake (7 %), which adjusts conditions in the rumen to allow for increased efficiency of feed utilization (Ibrahim and Tibin 2003). Our results were consistent with those of Savadogo et al (2000) and Koralagama et al (2008) who suggested that alfalfa is critical for improving forage utilization. In our study, lambs fed a full diet of alfalfa (ALF-100) did not have the highest intake of DM, OM and CP, which may be because animal growth was more limited by energy than N.

Body weight variation and FCR

Lambs showed relatively good growth performance throughout the experimental period, which indicated that all diets had nutrient content above the threshold level for maintenance requirement. Although replacing grass hay/crop straw with alfalfa improved final body weight, total gain, ADG and FCR for lambs in the present study, lambs given only a grass hay/crop straw diet were also able to gain body weight. This was likely due to the relatively good quality of the basal diet (concentrate plus maize silage). Although CP content of grass hay/crop straw was relatively low, it was likely higher than the limiting CP level of 7 % required for optimum ruminal microbial synthesis (Ibrahim and Tibin 2003).

DM and nutrient digestibility

The intake of DM, OM, NDF and ADF increased with the proportion of alfalfa hay in the diet up to 75 % (ALF-75), but decreased with 100% alfalfa in the diet (ALF-100). Regression analysis showed that DOMI increased with DCPI until about 100 g/kg and then started to decline (Fig. 2). Supplementation typically improves digestibility of DM and nutrients in low quality forage diets. However, results of supplementation on digestibility of DM and nutrients lack consistency (Lamidi et al 2006; Berhan and Getachew 2009; Feyera and Animut 2011). Low CP digestibility for animals with an all grass hay/crop straw diet in the present study may have been limited by N for rumen microorganisms to support optimal digestion activity (Ibrahim and Tibin 2003). Supplementation of grass hay/crop straw diets in our study did not improve digestibility of ADF, but improved CP digestibility, which was similar to findings of Kusmartono (2007) who fed sheep a rice-straw basal diet and supplemented with jackfruit wastes and Gliricidia or cassava leaf hay. They found that CP intake and digestibility increased significantly (P<0.05) with supplementation.

Tatsapong et al (2010) found that increasing CP level in the total ration improved CP intake and digestibility. In our study, DM and CP digestibility was not linearly related to CP intake, which may be because alfalfa did not change DM and CP digestibility of the grass hay/crop straw. Lagasse et al (1990) also found that alfalfa addition did not change DM and CP digestibility of bermudagrass [Cynodon dactylon (L.) Pers.] (a warm-season grass) or orchardgrass (Dactylis glomerata L.) (a cool-season grass). In addition, they reported that feed intake and digestibility response to alfalfa supplementation varied with characteristics of the particular grass species. Similarly, Bhatti et al (2008) reported that the effect of legume supplementation on digestibility could not be generalized, and variation in results among studies was most likely due to the inherent chemical constituents of the specific grass being tested. The decreased intake of DM and DOM in the total alfalfa diet (ALF-100) in our study was probably related to energy limitation. Owens et al (1991) and Haddad and Husein (2003) reported that improved animal performance as a result of CP supplementation was mediated through either an increased DOM intake or an enhanced efficiency of metabolizable energy utilization. This was also confirmed by Fasae et al (2012) who found that DM intake for sheep fed basal diets of cassava and maize leaves was significantly lower than for sheep given diets containing higher CP.

Economic evaluation

The higher cost per kg live-weight gain for diets containing alfalfa than diets containing only grass hay/crop straw was mainly due to the relatively high price of alfalfa, which increased the cost of the diet (Table 6). The diet that contained no alfalfa (ALF-0) and the diet with 375 g/kg alfalfa (ALF-75) had a similar cost per kg gain. Although grass hay/crop straw had poor digestibility, it cost less. Conversely, alfalfa with its high digestibility cost more. As a result, higher body weight gain or ADG did not necessarily translate into a higher profit per lamb (Table 4).

Conclusions

• Results from the present study indicated that the CP content in lamb diets increased with increasing proportions of alfalfa hay in the diet. The DM, OM, CP and fiber intake of the grass hay/crop straw and alfalfa mixtures was higher than that of grass hay/crop straw alone. The ADG and profit per lamb were highest when lambs were fed a diet containing grass hay/crop straw with 375 g/kg alfalfa (ALF-75). Lambs fed a diet with more than 375 g/kg alfalfa had reduced ADG and profit per lamb. With the concentrate and maize silage basal diet typically used in northern China, local farmers could improve lamb production and profits by adding alfalfa to lamb diets.

Acknowledgements

Authors would like to thank the household farm in northern China for feeding and other help throughout the experiment. This work was supported by grants from the Modern Agro-industry Technology Research System (CARS-35), China Special Public Sector Research Project (Agriculture: 201003019), and National Key Basic Research Program of China (2014CB138805).

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Received 24 May 2014; Accepted 10 November 2014; Published 1 December 2014

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