Determining the optimum level of Desho Stylo basal feed combination on feed intake, milk yield and composition of lactating high-grade crossbred cows

Workneh Tezera, Solomon Mengistu², Mengistu Urge¹, Diriba Geleti² and Mitiku Eshetu¹

Ethiopian Institute of Agricultural Research, Holetta Research Center. P O Box 2003 Addis Ababa or 31 Holetta, Ethiopia
workzer@yahoo.com
¹ School of Animal and Range Sciences, College of Agriculture and Environmental Sciences, Haramaya University P O Box 138, Dire Dawa, Ethiopia
² Ethiopian Institute of Agricultural Research (EIAR), P O Box 2003 Addis Ababa, Ethiopia

Abstract

The experiment was conducted at Hollota Agricultural Research Center, Ethiopia with the objective of determining the effect of optimum level of Desho-Stylo basal feed combination on feed and nutrient intake, apparent digestibility, milk yield, milk composition and body weight change of lactating F2 crossbred dairy cows. Eight high grade (75 %) crossbred cows (Holstein Friesian x Boran) with a milk yield at a range of (9-11kg, d ^-1), body weight (380 ± 50 kg) and early lactating cows of different parties were randomly assigned in basal forage treatment sequence in a double 4 x 4 Latin square design with 4 treatments and 4 measuring periods of 22 days each. In each period the first 15 days were adaptation period. The four dietary treatments were; control (100% DGH). SG15 (85% DGH: 15% SG), SG30 (70 % DGH: 30% SG), SG45 (55 % DGH: 45% SG). Total DM intake was greater (p<0.01) for SG45 and SG30 than Control and SH15. With respect to nutrient intake, replacement of ASH with SG at increasing level linearly increased (p<0.001) OMI, CPI, MEI and ADLI. However, intake of Ash, NDF and ADF were similar among diets. Apparent digestibility coefficients of DM, OM, NDF and ADF linearly increased (p < 0.01) as SG replaced DGH at increasing level. However, the apparent digestibility of CP was not influenced by dietary treatments. There was a difference (p<0.01) in daily milk yield between the SG45 and that of control groups(11.55 vs. 10.45 respectively). Similarly, 4 % fat corrected milk and fat yield were significantly different (p<0.001) among treatments. However, milk protein concentration and yield, total solid concentration and yield and feed conversion efficiency were similar for all treatments, while a tendency of increased milk fat concentration was observed with an increase in the level of replacement of DGH for SG. Average daily live weight loss was significantly lower (p<0.05) for SG45 (-172 kg/day) compared to control (-375.00 g/day), SG15 (-196.40 g/day) and SG30 (-202.4 g/day). It is concluded that SG can partially replaces desho grass hay in the diet of lactating dairy cow with improved daily milk yield, milk fat content and yield and without affecting, milk protein content and yield, and feed conversion for milk production. Therefore, using mixed grass and legume feed could be considered as one of the strategies that bring about an efficient utilization of natural pastureland for dairy cow feeding and provides an option for quality forage during the dry season compared to the conventional natural pasture grass hay based diet. In order to supplement the current study, further investigation is recommended on the effect of feeding partial substitution of Desho grass hay with Stylo hay based diets on long term reproduction, lactation, growth trials, degradation characteristics and composition and quantity of ruminal fermentation end products.

Key words: digestibility, hay, intake, legume, substitution

Introduction

Although the livestock sector has a significant contribution to the national economy, production per animal is extremely low. The major constraints limiting livestock production in Ethiopia is inadequate nutrition in terms of quantity and quality (Samson and Frehiwot 2014; Friat and Haben 2020). Natural pasture and fibrous crop residues are the major feed resources that the ruminants, in the smallholder sector in the country, depend for their survival, growth, reproduction and production. Natural pastures and crop residues are characterized by high fiber (>55%), low crude protein (<7%) and metabolizable energy (ME) contents (Zewdie et al 2011; Girma et al 2014). As a result, their intake level is limited and they hardly satisfy even the maintenance requirements of animals

Previous research results have indicated that improved fodder species generally have higher herbage yield potential. In addition to their productivity, most of the improved forage crops are also nutritionally superior to that of natural pasture and crop residues (Alemayehu and Getnet 2012). They also have a long growing season and help to extend the green feed period so as to provide useful nutrients mainly in rural areas where availability and accessibility of agro industrial by products is limited. Moreover, improved fodder crops especially the legumes can complement crop production through maintaining soil fertility via fixation and accumulation of nitrogen and also help to prevent soil erosion and replenish degraded land when integrated into natural resource management schemes (Workye et al 2018)

To combat the livestock feed Shortage, the use of indigenous forage plants as a feed source is recommended. Among such types of forage species, which has multifaceted potential, is desho (Pennisetum glaucifolium) grass. This grass received considerable emphasis in the current research and development endeavors. It is a panicoid (tribe Panicae) grass species endemic to the central and the south-western Ethiopian highlands (Hedberg I and S Edwards 1995). It has been traditionally used by Wolayta people in the Southern Nations, Nationalities and Peoples Region (SNNPR), well ahead of its evaluation and release by the Debre Zeit Agricultural Research Center (DZARC) (Solomon M et al 2017). Due to its fast growth and rapid ground cover, desho has been locally used as cut-and-carry fodder and as gully-stabilizing plantings in Wolayta area. The mean fodder yield over locations was the highest for Kindo KoSGa1-DZF-591 (23.59 t/ha DM) followed by Areka-DZF-590 (21.70 t/ha DM). While Kulumsa DZF-592 and Kindo Kosha2-DZF-589 ranked third and fourth in DM yield, giving 20.69 and 17.00 t/ha, respectively. Overall, Desho varieties were reported to perform excellently as was evident from the agronomic performance and nutritional composition.

Herbaceous forage legumes have been identified as potential protein supplements for ruminants since they contain high crude protein (150 -300 g/kg DM), minerals and vitamins needed for the growth of ruminal microbes (Norton and Poppi 1995). Stylosanthes guianensis is the most outstanding out of the numerous forage legumes that is evaluated. It is easy to establish either from cuttings or seed, and is suitable for green manuring (to improve soil fertility), soil cover against erosion and for forage. Its ability to remain green for a large part of the dry season means that cattle could benefit from increased intake of protein-rich feed (Cook et al 2005; Mannetje 1992). This made it a prime candidate for pasture improvement in the sub humid and semi-arid areas of the country.

The incorporation of leguminous forages such as Stylosanthes guianensis, in the diet of ruminants, can stimulate rumen function by providing protein-rich forage (Barros-Rodríguez et al 2012). This increases the availability of compounds such as ammonia, amino acids and peptides as well as branched short-chain fatty acids, which are produced as a result of degradation of proteins. These substances promote fiber breakdown by acting as ruminal growth activators for rumen bacteria, especially cellulolytic bacteria (Hoover and Stokes 1991).

Despite its presence in different parts of the country, information is hardly available on the large scale animal evaluation of desho grass when particularly used in mixture with forage legumes such as Stylosanthes. Therefore, this study was conducted to determining the optimum level of Desho-Stylo basal feed combination on feed intake, milk yield and compositions of lactating high-grade crossbred cows

Experimental animals and management

The study was carried out at Hollota Research Agricultural Center. A total of eight lactating high-grade crossbred cows (75% Friesian and 25% Borana) were used for this experiment. Experimental cows with similar daily milk yield (9-11kg, d ^-1), same stage of lactation (early lactation, i.e. 5^th day after parturition) and average body weight (380 ± 50 kg)), but only differing in parities (one through four) were selected from the total dairy herd available at station. All the cows were weighed and drenched with broad-spectrum anti-helminthic (Albendazole 500mg) prior to the start of the experiment. The calves were separated from their dams five days after parturition and reared according to the standard calf rearing procedures of the research center. The cows were individually stall-fed in a well-ventilated barn with concrete floor and appropriate drainage slope and gutters.

Experimental feeds/diets

Production of experimental forges

Stylo (Stylosanthes guianensis) and Desho grass (Pennisetum glaucifoilium) were established at about one and a half and two hectares of land at Assosa and Hollota research Agricultural Center, respectively in early June/2019 right after the first shower of rain using recommended agronomic practices. Assosa is located at 10°02'05''N latitude and 34°34'09''E longitudes. The total annual average rainfall of Asossa is 1275 mm. The minimum and maximum temperatures are 16.75 and 27.92 °C, respectively. The dominant soil type of Asossa area is Nitosols with the soil pH ranging from 5.0 to 5.3. Hollota Agricultural Research Centers is located at 9º 00’ N longitude and 38º30’ E latitude. The total annual average rainfall of the area is 1144 mm. The minimum and maximum temperatures are 6 and 22 °C, respectively. The dominant soil type of Hollota area is Nitosols with the soil pH ranging from 5.0 to 6. Stylo was harvested at 50% flowering, field-cured, baled and stored in a roofed hay shed whereas desho grass was harvested at appropriate time of harvesting, field cured chopped, baled and stored in a roofed shed. Representative samples from both grasses and legumes were taken for laboratory analysis before and after the hay was baled to confirm proper drying and to note if there is any change during forage handling processes. The Stylo hay produced at Assosa Agricultural research Center transported to the experimental site (Holleta Agricultural Research center) via heavy trucks.

Formulating concentrate mix

A concentrate mix that was assumed to be sufficient for the entire experimental period was formulated on-station taking wheat bran and noug cake as main ingredients in such a way that the formulated ration comprised of 66% wheat bran and 33% nug seed cake and 1% salt. The mix was assumed to fully meet the major nutrient requirements of lactating crossbred cows with milk yield of 9-11 kg /day and a butter fat content of 4.5 % as described in ARC (1990) The cows were given supplement feed at the rate of 0.5 kg/l of milk. Representative samples were taken for laboratory analysis. Chemical compositions in the mix were DM (908.9g/kg DM), CP (225g DM/kg DM), IVOMD (752g/kg DM), and ME (12MJ/kg DM) estimated from in-vitro OMD (DODM*0.016).

Experimental design, treatments and measurements

At the beginning of the experiment, eight cows were randomly blocked in a switch over 4 x 4 double Latin square design in four periods and parities with two squares (square1 and square2). Each period consisting of 22 days; where 15 days were allocated for adaptation and the remaining 7 days were used to collect actual data. Hence the experiment took a total of 88 days (December, 2020 through April, 2021). The lactating cows were selected from the total dairy herd based on daily milk yield, stage of lactation, body weight and parity. The experimental animals were then randomly allotted to one of the four dietary treatments given in Table 1.

The basal feed was offered at 8:00 am with daily adjustment to 20% refusal from previous day’s intake. Water was offered ad-libitum. The concentrate mix was offered with equal portions at 5:00 am and 5:00 pm during the morning and evening milking times. The quantity of concentrate mix offered daily was at the rate of 0.5kg/kg of milk produced by each cow. However, adjustments were made for concentrate offer at the end of each period and for each treatment as per the actual milk produced. Similarly, the quantity of the feed offered and refused was measured and recorded for each cow to determine daily feed and nutrient intake. From the hay shade representative samples were taken every week from each batch (three samples per batch) and dried in an oven at 65⁰C for 72h. Voluntary DM and nutrient intakes and digestibility were calculated from the mean values of chemical and IVOMD values from triplicate values for each batch. Similarly, feed refusals samples taken on a weekly basis for each treatment, after being properly sub sampled, was oven-dried at 65⁰C for 72 h. The samples were then ground using Cyclo-Tec sample mills to 1 mm sieve size for proximate, detergent and in vitro digestibility analysis and at 2mm sieve size for nylon-bag degradability study trial and kept at room temperature in sealed plastic bags until they are ready for analysis.

Cows were hand-milked twice a day starting at 5:00 am in the morning and 5:00 pm in the evening. The daily milk yield of individual cows was weighed using a Salter balance. About 100 ml thoroughly mixed composite (morning and afternoon) milk samples were taken using a glass measuring cylinder (100 ml capacity) for each cow twice every week upon completion of the adaptation period. The milk samples were used to determine percentage of fat, protein, lactose and total solids. Body weight (BW) was recorded for two consecutive days at the beginning and end of each experiment period for each treatment to monitor BW change as a result of the intervention diets

Diet apparent digestibility

Apparent digestibility for the total diet DM and nutrient was determined using total collection methods for a period of 5 consecutive days every month, i.e., from day 16 to 21 of each period. To minimize error in faeces collections, farm personnel were assigned around the clock only to scoop faeces into plastic buckets as soon as the animals defecated. Urinal contamination was minimized by frequent washing of the concrete floor with high pressure running water using a plastic water hose. Individual cow’s faeces was weighed every morning before 8:00 am and before fresh feeds was given to the animals. After weighing, the faeces from each cow were thoroughly mixed and a sample taken was placed in polyethylene bag. Composite samples of about 1% of the daily collected samples were mixed and stored as one sample in a deep freezer (-4⁰C) until the end of the collection period. At the end of the collection period, the 5 days pooled samples were subsequently thawed and mixed thoroughly and two sub-samples taken. One sample for estimating DM was oven dried at 105⁰C for 24h, while the other sample was oven dried at 65 ⁰C for 72h, ground to pass a 1mm sieve and stored in sample bottles at room temperature. Composite samples of forage legume hay, Desho grass hay, concentrate, and faecal DM output were analyzed to determine DM, OM, N, NDF, ADF digestibility.

Sample analysis

Composition of feeds and faeces

All samples of feed offered and refusals and faeces were analyzed for DM, OM, N (Kjeldahl-N) according to AOAC (1990) procedures. NDF fibre, ADF and permanganate lignin were determined by the methods of Van Soest and Robertson (1985). In vitro digestibility for feed offered and refusals were determined using procedures outlined by Tilley and Terry (1963).

Milk yield and composition

The amount of milk produced from each cow was measured by using graduated glass cylinder. In the last five days of each period, milk aliquot sample from the morning and evening milk was taken from each individual cow. Milk was sampled in pre-labelled 50 ml plastic vials. Lacto scan ultrasonic milk analyzer was used to determine fat, protein, solid not fat and total solid. Daily yields of milk fat, protein, total solids and solids-not-fat were calculated for the last week of each period, and 4% fat corrected milk yield (FCM) was calculated to standardize treatment comparisons following the NRC (1989) formula:

FCM (kg/day) = 0.4 x milk yield (kg/d) + 15 x fat yield (kg/d)

Feed conversion efficiency (FCE) and feed conversion ratio (FCR) were calculated following Linn (2005) formula;

FCE = (Mean daily milk yield)/ (Mean daily DM intake)

Statistical analysis

Data on milk yield and compositions, feed conversion efficiency, live weight changes, voluntary DM and nutrient intakes and digestibility parameters were subjected to analysis of variance (ANOVA) procedure for double Latin Square Design using Statistical Analysis System (SAS 2004). Treatment means were separated using Least Squares Significant difference (LSD). The model used for the analysis of data was:

Y_ijklm =µ+ S_i + C_j + P_k + T _l + E_ijklm; Where; µ=Over all mean; S_i = Square effects, i=1-2, C_j=Cow effect (parity) j=1-4; P_k =Period effect, k=1-4; T_l = Treatment effect, l=1-4; E_ijklm = Random error

Results and discussion

Chemical composition of the feed samples

The chemical composition of the feeds used in the current study is presented in Table 2. CP content of the Desho grass hay was 8.9 %. This value exceeds maintenance requirement of cattle (7.5 to 8%) as suggested by Van Soest (1982). The CP content of Stylo hay (S.guinansis) and the concentrate mixture (66% wheat bran and 33% nug seed cake) used in this study was 19.7 and 22.5 respectively. Lonsdale (1989), classified feeds as low, medium and high protein sources if they contain less than 12, 12 to 20 and greater than 20% CP, respectively. In this study, the CP content of Desho hay is classified as low and Stylo hay (S.guinansis) lies in a medium range. However, the concentrate mixture feeds are high protein source diets.

The NDF and ADF contents of the Desho grass hay in this study were 70.1 and 39 %, respectively. The ADL content was 5.4%. The higher NDF value observed for Desho grass hay may presumably affect the intake and digestibility of dry matter negatively (Beyene 1976). The high fiber content of Desho grass hay in this study might be attributed to the stage of maturity of the hay at harvesting time. It is obvious that, as a plant matures, its cell wall constituents or structural carbohydrates like cellulose, and other compounds such as lignin increases albeit CP content gradually decreases (McDonald et al 2002). Stylo hay (S.guinansis) had higher ADL content compared to Desho grass hay (Table 2). The fiber constituents of the formulated concentrate mixtures were NDF (47.9%), ADF (20.3%) and Lignin (4.8%). These values are lower compared to similar constituents in Desho and stylo grass hay. Rajupreti (2006) revealed that a feed that contained more than 45% ADF and 65% NDF is considered as low quality feed. However, the feed stuffs used in this study, except Desho grass hay can be classified as medium to high quality supplemental feeds.

Dry matter and nutrient intake

The effects of partially substituting basal diet of Desho grass hay (DGH) with Stylo hay on dry matter and nutrient intakes are shown in Table 3. Total dry matter intake (TDMI) linearly increased (p<0.01) as Stylo hay replaced DGH at increasing level. TDMI of SG45 and SG30 were higher (p< 0.05) than control groups and SG15. In this study, cows in SG45, SG30 and SG15 consumed 12.2 %, 3.2 % and 2.8 % more basal diet than cows in control groups. The variation in total DMI among diets is attributed to the difference in forage DMI. Concentrate intake was similar among diets (p >0.05) that averaged 4.78 kg DM per day.

Table 3. Least squares means of dry matter and nutrient intake of lactating crossbred dairy cows fed different proportions of Desho, Stylo legume hay and supplemented with concentrate mix
Parameters	1Dietary Forage Ratio (DGH:SG)				SEM	f>p
	Control	SG15	SG30	SG45		Diet	L
Dry matter intake (kg, d-1)
Basal feed	8.89b	9.14b	9.81a	9.98a	0.16	***	***
Concentrate	4.81	4.69	4.75	4.69	0.10	ns	ns
Total DM	13.71b	13.83b	14.56a	14.67a	0.18	***	***
DMI (% BW)	3.62a	3.55a	3.38b	3.38b	0.05	**	**
DMI, g kg-1 w0.75	113.48	111.95	113.90	114.64	2.08	ns	ns
Nutrient intake (kg, d-1)
OM	9.76b	10.10ab	10.48a	10.47a	0.140	**	**
Ash	1.11	1.11	1.11	1.06	0.017	ns	ns
CP	1.59d	1.73c	1.88b	1.98a	0.025	***	***
ME(MJ/d)	153.2b	158.5ab	164.6a	164.5a	2.240	***	***
NDF	6.52	6.62	6.71	6.54	0.097	ns	ns
ADF	3.41	3.75	3.68	3.68	0.120	ns	ns
ADL	0.68b	0.72ab	0.77a	0.80a	0.010	***	***
1 Dietary forage ratio of Desho grass hay (DGH) and Stylo guianensis hay (SG); Control=100% DGH: 0% SG; SG15=85% DGH:15% SG; SG30=70% DGH: 30% SG; SG45=55% DGH: 45% SG. a, b, c Least squares means in the same row without a common superscript are significantly different (p< 0.05), ** =significant at p< 0.01; *** = significant at p < 0.001; ns=not significant; SEM=standard error of mean; L= linear effect of substituting DGH with SG at increasing level; DMI=dry matter intake; NDF= neutral detergent fiber; ADF = acid detergent fiber; ADL = acid detergent lignin; W0.75 = metabolic body weight; % BW = percent body weight

Ash intake did not vary between treatment diets (p> 0.05) where the average intake was 1.11 kg/day. The organic matter (OM) intake significantly different (p<0.001) among treatment diets. The highest intake was observed in cows receiving SG45 and SG30 compared to control and SG15.

Figure 1. Effect on DM intake of replacing desho grass hay with Stylosanthes guianensis hay	Figure 2. Effect on CP intake of replacing desho grass hay with Stylosanthes guianensis hay

The crude protein intake (CPI) expressed as percent of total DM intake was 11.6, 12.51, 12.9 and 13.5% DM for diet control, SG15, SG30, and SG45, respectively. Crude protein intake was significantly different (p<0.05) among treatments and linearly increased with the replacement rate of Stylo hay to DGH. The least CP intake was recorded in the DGH based diet (control diet) compared to SG45, SG30 and SG15. The higher CPI on SG45 (55% DGH: 45 % SG basal diet) compared to control diet alone (100% DGH basal diet) is the result of increasing CP content due to increasing replacement rate of Desho grass hay with stylo hay as shown in Table 2. The crude protein requirement of lactating dairy cows with mean body weight of 450 kg, producing daily milk yield of 13 kg with 4% milk fat content and with a weight gain of 0.3 kg/day at mid-and late lactations was 1.74 kg/day (Kearl 1982; NRC 1989). In the present study, cows assigned in SG30 and SG45 consumed 9 % and 13.8%, respectively in excess of their requirement to support the above level of milk production whereas, cows in diet control diet and SG15 consumed 8.6 % less and almost equal of their requirement to support the above level of milk production.

Intake of ADL was significantly (p<0.05) higher for control than SG15 and SG45, indicating that control (100% DGH) contained more indigestible fractions compared to SG30 (70% DGH: 30 % SG) and SG45 (55% DGH: 45 % SG). However, intake of NDF and ADF were not significantly (p>0.05) varied among treatments.

Apparent feed and nutrient digestibility

The effect of partially substituting basal diet of Desho grass hay (DGH) with Stylo hay (SG) on apparent feed and nutrient digestibility of lactating dairy cows is presented in Table 4. Apparent dry matter digestibility (DMD) and organic matter digestibility (OMD) markedly increased (p<0.001) with the advanced substitution level of SG through control to SG45. DMD was improved by 5.5, 8.1 and 13.4 % in SG15, SG30 and SG45, respectively against control. High DOMI was achieved in SG30 and SG45 while control had the least value. This is related to the higher digestibility of the diet containing SG compared to the Desho grass hay based diet.

Metabolizable energy intake (MEI, MJ/day) had also similar trend with the DOMI. Cows fed on high proportion of stylo based diet (SG45) obtained higher (p<0.001) ME than those on DGH based diet (control). However, the daily MEI of cows fed on the DGH basal diet was below NRC (1989) recommended value of 133 MJ, ME/day for mature cow (450 kg of BW) capable of producing 13kg of milk. Cows fed on 15, 30 and 45 % substitution levels of Stylo hay basal diet consumed 8.1, 15 and 19.65 more MJ ME/day, respectively as compared to cows on the control diet. This is due to the availability of higher (p<0.05) energy concentration in Stylo hay basal diet as compared to DGH basal diet (8.90 vs 10.09 MJ ME/kg DM (Table 4).

Partial replacement of Desho grass hay with stylo hay at increasing level did not affect (p>0.05) crude protein digestibility (CPD) among treatments. CPD was slightly higher (3.1%) on SG45. DCP intake was largely improved with the high proportion stylo hay basal diet than Desho grass hay basal diet alone (control diet), which might be the result of inclusion of additional CP in (SG45) that helps further to enhance rumen bacterial activity.

Fiber fractions of NDFD and ADFD varied (p<0.01) among treatment diets. Digestibility of NDF was improved by 7.83, 13.25 and 19.1% for SG15, SG30 and SG45, respectively compared control groups. Similarly, inclusion of stylo hay increased ADFD by 7.2, 17.8 and 28.2% for SG15, SG30 and SG45, respectively compared to control groups. Cows assigned on SG45 (55% DGH: 45% SG) consumed 18.7% and 37.65% more DNDF and DADF, respectively compared to control groups (DGH based diet).

The higher fiber (NDF and ADF) digestibility in relative to indicate that there might be a difference in their fiber degradability characteristics. Digestibility of NDF and ADF are important parameters of forage quality as it has an influence on animal performance. Oba and Allen (1998) used silages with similar NDF and CP contents but different NDF digestibility to lactating dairy cows and found significant increases in DMI and milk yield of cows fed silage with high NDF digestibility. The current result reveals that forages with high NDF digestibility improved milk yield by increasing energy intake.

Apparent DM/nutrient digestibility was enhanced in the total diet replaced by different proportion of Stylo hay replacement which in turn improved microbial activity as a result of increasing amount of crude protein available to rumen microbes. Ahvenjarvi et al (2006) stated that cellulolytic microorganisms utilize crude protein as their primary nitrogen source; the relatively higher intake of crude protein in the stylo hay containing diets could also improve fiber digestion. Furthermore, improvements in DM and OM digestibility due to supplemental protein and/or energy have been well documented (Yohannes 2011; Gebreslassie 2012; Hagos 2014). This is partly explained by adequate nutrient supply to rumen microbes for their proliferation and digest more of the DM or OM consumed (Bonsi et al 1995).

Milk yield and milk composition

The effects of substituting DGH basal diet with SG on milk yield, milk composition and production efficiency of dairy cows are shown in Table 5.

Figure 3. Effect on milk yield of replacing Desho grass hay with Stylosanthes guianensis hay	Figure 4. Effect on fat content of milk from replacing Desho grass hay with Stylosanthes guianensis hay

Daily milk yield was significantly different among treatments (p< 0.01) and was higher in SG45 followed by SG30 and SG15. The lowest average daily milk yield was observed in control groups. The difference in milk yield among treatment groups is attributed to the difference in CP and energy contents in the diets (Steinshamn, 2010). Milk fat, Milk protein, solid not fat (SNF) and total solid (TS) contents were not significantly (p>0.05) different among dietary treatments. The feed conversion efficiency (FCE) was significantly (p< 0.001) different and linearly increased from Control to SG45.

Milk production increased (p< 0.01) with increasing Stylo hay proportions in the diet. Cows managed in SG45 produced 1.53 kg/d more milk than cows received control diet. This increase in milk yield is consistent with the higher DM and energy intakes of cows fed stylo hay diets compared with cows fed the 0% Stylo hay diet (Table 3).

Mean daily live weight change

Cows fed sole Desho grass basal diets and other dietary treatments showed significant (p<0.05) variation only for average daily weight gain (DWG) (Table 6). A maximum live weight loss (-375 g/day) was experienced in the control group that fed sole Desho grass hay. While, cows received SG45 on average lost a live weight of 172.6 g/day. In this study, none of the treatment diets have shown positive response for daily live weight gain of lactating crossbred cows.

Loss in BW despite the increased CP intake above the requirement in this study suggests that energy was the most limiting nutrient. Indeed, acetate is the predominant rumen fermentation end product in grass hay based diet (Leng 1982). This limits the molar proportion of propionic acid leading to inadequacy of glucose for milk synthesis. The BW loss of cows during early lactation (60-90 days after calving) was not surprising and has been reported in a similar study (Muinga 1992) with BW loss for the entire lactation period ranging between 20- 90 kg for lactating crossbred cows fed ad libitum Napier grass and supplemented with 0.4 or 8 kg/ d of fresh leucaena forage from day 15-112 of lactation. Garnsworthy (1997) noted that cows in early lactation and those of higher genetic merits partition energy for milk production at the expense of body fat reserve and noted that cows usually lose 0.5-1.0 kg of BW each day for the first eight weeks of lactation and this is mostly body fat. Therefore, increased energy intakes at this stage of lactation is expected to result in further increases in milk yield, if the cow’s genetic potential has not been attained and/or a reduction in body fat mobilization.

Conclusions

Results of this study revealed that stylo hay can partially substitute Desho grass hay in the diet of dairy cows without adverse effects on intake. Compared with the sole Desho grass hay group, cows fed the 45% stylo hay basal diet had higher milk yield feed intake and nutrient digestibility. Thus, these results suggest that feeding 45% stylo hay, replacing a portion of Desho grass hay, improves lactation performance and milk yield and feed intakes for lactating dairy cows.

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