Effect of different levels of fibrolytic enzyme on feed digestibility and production performance in lactating dairy cows

The poor quality conventional feed for the livestock production in Pakistan are wheat straw, tops of sugar cane and tree leaves. To enhance the nutritive value of feed, this study focused on investigating the effects of fibrolytic enzyme (Fibrozyme, Alltech Inc. Company, USA) at different levels i.e. 0, 5, 10, and 15g/kg of total mix ration on feed intake, digestibility, milk yield and composition, and economics of the ration in Holstein Friesians cows. Twelve Holstein Friesians cows of almost the same age, and lactation stage were randomly allocated into 4 equal groups i.e. A, B, C, and D. Four experimental rations supplemented with Fibrozyme 0g, 5g, 10g, and 15g/Kg of total mix ration were assigned to these sets correspondingly. The dry matter intake was linearly and significantly (P<0.05) improved. A significant effect of Fibrozyme was observed for organic matter digestibility, ether extract digestibility, crude fiber digestibility, nitrogen free extract digestibility, and acid detergent fiber digestibility while the results were statistically non-significant for crude protein digestibility, neutral detergent fiber digestibility, and ash digestibility. Milk yield and composition except fat were significantly (P<0.05) increased in all Fibrozyme treated groups. This study concludes that supplementation of Fibrozyme at the rate of 15g/Kg total mix ration improved the dry matter intake, nutrients digestibility, and milk production and constituents like protein, lactose, and solid not fat. Therefore, treatment of total mix ration with Fibrozyme was desirably reasonable and profitable.


Introduction
Pakistan being a tropical country has the major constraints in the form of poor quality and quantity of animal feed resources. The conventional feed for the production of livestock in the country are wheat straw, tops of sugar cane and tree leaves. These feedstuffs despite of their low quality can be better utilized to enhance the profitability of dairy sector in tropical or subtropical countries, especially if their nutritive value is improved by the addition of exogenous enzymes.
The production capacity of a dairy animal can be enhanced with different approaches like fermentation's manipulation in fore stomach [1]. Therefore, exogenous fibrolytic enzymes addition in feed can be used as a tool to manipulate the fermentation in the rumen [2]. The addition of these enzymes in ruminant rations has been considerably studied in dairy cattle and goats, but variable performance responses have been observed [3][4][5]. The enzymes related effects in ruminant animals are the result of different pre-feeding and post-feeding mechanisms [6]. The fibrolytic enzymes potentially increase the breakdown of fiber both in vivo and in vitro [7], while the desirable effects of these enzymes seem to be linked with improvements in nutrient digestibility in the rumen [8], the breakdown of cell wall fraction and nutrient digestibility in lactating cows [8,9]. The hot climate forages are low in energy and their cell wall fraction contains lignin, pectin and silica in a high amount limiting the carbohydrate fermentation. To increase the ability of ruminant fore stomach to get essential nutrients from the feed stuffs, is the main objective of the nutritionists. Therefore, this study was planned to see the impact of Fibrozyme ® (high xylanases activity from Aspergillus niger and Trichoderma viride fermentation extract) on digestive characteristics of feed stuffs, economics, and production performance of exotic cattle breed Holstein Friesian (HF) under prevailing tropical conditions of the country.

Materials and methods Experimental design
The current research study was conducted at the Dairy Farm of the University of Agriculture Peshawar, Pakistan. Twelve animals of almost the same age, milking stage and body weight were selected and randomly divided into 4 equal groups (n=3). Each experimental animal was treated for ecto and endo parasites before the start of feeding trials. Animals were given a 15 days' adaptation period. Fresh drinking water was available ad libitum throughout the experiment lasted for 25 days. Four experimental rations 1, 2, 3, and 4 (Table 1 & 2) were prepared [10], and fed to experimental groups A, B, C, and D respectively.

Statistical analysis
Data were statistically analysed with oneway ANOVA and significance among groups was tested with least significant difference test (LSD). The statistical model used is as under: Yij= µ + βj + Єij Whereas; Yij = yield of treatment, µ = mean of overall treatment, βj = Effect of treatment, Єij = Random error Results

Effect of Fibrozyme ® on nutrients intake and digestibility
The overall dry matter intake (DMI) was significantly (P<0.05) increased by the supplementation of Fibrozyme ® . The peak value of DMI in cows was noted on 15g/kg, followed by 10g/kg of the total mixed ration ( Table 3). Results of the current study showed that organic matter digestibility (OMD), ether extract digestibility (EED), crude fiber digestibility (CFD), nitrogen free extract digestibility (NFED), acid detergent fiber digestibility (ADFD), and neutral detergent fiber digestibility (NDFD) were significantly (P≤0.05) improved by the addition of Fibrozyme ® in experimental rations (Table 3). Generally, it was observed that the nutrients digestibility parallel increased with increase in the level of Fibrozyme ® in total mixed ration (TMR). On the other hand, results indicated that effect of Fibrozyme ® on crude protein digestibility (CPD), and ash digestibility (AD) was not statistically significant ( Table 3).

Effect of Fibrozyme ® on milk yield and composition
Results indicated that the Fibrozyme ® treatments significantly improved the milk yield (MY) in experimental cows in a dose dependent manner (Table 4). Similarly, positive response to Fibrozyme ® supplementation was noted in milk composition in terms of protein, lactose, and solids not fat (SNF) percentages. The data showed that fat percentage linearly decreased with increase in Fibrozyme ® level in TMR ( Table 4).

Economics of the ration
Results of the experiment showed that Fibrozyme ® treatments significantly increased the economic efficiency of the ration. All of the treatments significantly increased economics of the ration as compared to control diet, but there was no significant variation among the Fibrozyme ® treatments (Table 4).

Discussion
In the present study, DMI was significantly (P<0.05) increased with the supplementation of Fibrozyme ® at the rate of 10 and 15g/kg of TMR. These outcomes are consistent with the findings reported in earlier studies [14] in which different levels of fibrolytic enzyme were fed to dairy cattle, and significantly enhanced DMI was noted. Associated with these results, Ware and Zinn [15] added fibrolytic enzyme to the TMR of steers and found the positive impact on DMI of experimental animals. Furthermore, Szasz et al. [16] incorporated fibrolytic enzyme to yearling heifer's ration, and they found higher DMI compared with the ration without the enzyme addition. Previous studies reported increased DMI when dairy cattle were fed with fibrolytic enzymes [17]. Several other researchers noted increased DMI of dairy cattle when fibrolytic enzymes were added to TMR or concentrate ration [18,19]. This improvement in DMI might be credited to the capability of exogenous enzymes (Fibrozyme ® ) to activate the production of fibrolytic, and lactate consuming bacteria in the cattle rumen, which can increase the rumen pH, and fiber digestibility, ultimately increased DMI. Ahn et al. [20] reported that fibrolytic enzyme supplementation to dairy cows at the level of 0.05 and 0.1% of TMR did not increase DMI and no difference was recorded between cows fed with enzymes treated or untreated diet. Increased NDFD by the addition of Fibrozyme ® was observed in experimental cows. These findings are in agreement with the outcomes reported in previous studies