Nutrient Digestibility of Preweaning Pasundan Calves Fed Flushing Diets under Extensive Grazing

| In an extensive rearing system, immediately after birth, the calf follows the mother to graze on pasture. This condition certainly affects nutrient digestibility because the digestive system is not yet fully developed. The study aims to reveal nutrient digestibility of preweaning calves fed flushing diets under extensive grazing. The study used a completely randomized factorial design with two factors and five replicates. The first factor is gender and the second one is diet treatment. The total number of calves used in this study was 30, consisting of 15 males and 15 female preweaning Pasundan calves. The dietary treatment included: (1) calves are allowed to graze without feeding flushing diet, (2) calves are allowed to graze and fed a flushing diet without urea-impregnated zeolite (flushing-1), (3) calves are allowed to graze and fed a flushing diets with urea-impregnated zeolite inclusion (flushing-2). The measured variables consisted of feed intake and apparent digestibility of nutrients. The collected data were analyzed by a general linear model univariate analysis. The results showed that compared to the control diet, supplementation of flushing diets increased (P<0.05) dry matter digestibility up to 29.01% (53.89 ± 4.85% in grazing calves vs. 80.94 ± 1.65% in flushing-1 calves or 82.90 ± 1.47% in flushing-2 calves), crude protein digestibility up to 5.71% (86.17 ± 2.91% in grazing calves vs. 90.61 ± 1.65% in flushing-1 calves or 91.88 ± 0.79% in flushing-2 calves), ether extract digestibility up to 12.12% (80.06 ± 7.39% in grazing calves vs. 92.18 ± 1.57% in flushing-1 calves or 90.09 ± 1.20% in flushing-2 calves), neutral detergent fiber up to 28.81% (54.58 ± 4.01% in grazing calves vs. 81.13 ± 3.41% in flushing-1 calves or 83.39 ± 1.75% in flushing-2 calves), acid detergent fiber by up to 24.27% (54.23 ± 4.69% in grazing calves vs. 72.41 ± 6.78% in flushing-1 calves or 78.50 ± 3.49% in flushing-2 calves), and cellulose by up to 22.79% (61.01 ± 5.15% in grazing calves vs. 82.03 ± 6.04% in flushing-1 calves or 83.80 ± 1.92% in flushing-2 calves). In conclusion, supplementing flushing diet to preweaning Pasundan calves under extensive grazing improved most nutrient digestibility parameters (dry matter, crude protein, ether extract, and fiber).


INTRODUCTION
C urrently, the development pattern of beef cattle breeding in Indonesia is still oriented to the pattern of community or family farms where the livestock raising system is carried out extensively or semi-intensively. Extensive maintenance is carried out by leaving the cattle in the pasture all day and night for a certain period without being shed. Semi-intensive maintenance is carried out by herding livestock to a place where there is a lot of grass, then fastening it with a long rope with a radius of 20-30 m from morning to evening. Towards evening, around 05.30 PM, the farmer then drives his cattle back to a certain place, a kind of paddock, which is surrounded by a bamboo fence to ensure that his cattle keep inside the bamboo fence. Cattle control activities in semi-intensive care are carried out throughout the day because the livestock are grazed by one or two herders, depending on the number of the cattle. born calves. The preweaning growth is a critical period because for the first time a calf enters an open environment where everything is out of control. The low quality of field grass in tropical areas worsen the livestock performances grazed extensively. However, in the extensive grazing systems, the utilization of low-quality feed, mainly from crop residues as well as agricultural by-products and other non conventional feedstuffs is a common practice (Agus and Widi, 2018).
In a cow-calf raising system that is grazed extensively, the preweaning calf only gets solid feed from the forage available in grazing areas, such as field grass, rice straw, or other agricultural wastes. All those feeds are almost undigested by the pre-weaned calves because of their rumen system not well developed yet. Maskaľová and Vajda (2015) described that fibrous feed had lower fiber digestibility because its lignin encrusted the fiber. Labussiere et al. (2009) described fibrous feed decreased dry matter digestibility. de Assis Lage et al. (2019) who fed the preweaning heifers with total solid diets (92% concentrates and 8% hay) resulted in higher digestibility of organic matter, crude protein, and fat. To improve the nutrient digestibility of low-quality feed is to reduce the particle size of the feed as recommended by (Ghassemi Nejad et al., 2012) that the small particle size of feed increased the surface area for microbial enzyme to access the feed particles, thus improved the nutrient digestibility.
However, due to the low quality of forage in the tropics (Agus and Widi, 2018), reducing the particle size alone will not be sufficient to meet the nutrient needs of pre-weaned calves during the transition period. The average crude protein content of field grass obtained from grasslands in the coastal areas of West Java is 9.74%. In fact, rumen microbial life requires feed containing at least 1.28% nitrogen or equivalent to 8% crude protein (Van Soest, 1994) and needs greater than 11% crude protein to support the optimal growth (Pathak, 2008). Thus, the crude protein content of field grass is only sufficient to meet the needs of rumen microbes. Therefore, to improve digestibility and fulfil nutrient requirements in pre-weaned calves that are herded extensively with their cows, a concentrate supplement is needed. Supplementation of the small particle size of concentrate as a flushing diet is expected to improve digestibility and fulfil nutrients requirement in the preweaning calves grazed extensively. The study aims to explore the nutrient digestibility of preweaning calves fed flushing diets under extensive grazing.

animals anD experimental Design
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.
The study used 30 preweaning Pasundan calves of 3 months consisting of 15 males and 15 females that were extensively grazed. The initial average body weight was 39.44 ± 13.57 kg for male calves and 37.167 ± 7.78 kg for female calves. The study used a completely randomized factorial design with two factors and five replicates. The first factor is gender and the second one is diet treatment. Five of each male or female calf was randomly selected and allocated to the following three treatments: (1) calves are allowed to graze without feeding flushing diet, (2) calves are allowed to graze and fed a flushing diet without urea-impregnated zeolite (flushing-1), (3) calves are allowed to graze and fed a flushing diets with urea impregnated zeolite inclusion (flushing-2). The measured variables consisted of feed intake and apparent digestibility of nutrients.
Flushing diets and drinking water were provided before and after the calves were grazed. Both flushing diets had similar protein and energy contents ( Table 1). The ureaimpregnated zeolite was formulated based on (Kardaya et al., 2018). Either flushing-1 or flushing-2 diet was provided in a coarse mash form. The adaptation period for flushing diet was carried out for 7 days and the feeding trial period was carried out for 7 days. Flushing diet was fed twice a day, i.e. in the morning at 0600-0800h as much as 500 grams before the calves were grazed and in the afternoon at 1700-1900h as much as 500 grams after the calves were driven back into the shed without rooftop from the grazing land. Every morning at 0800 h, the calves were driven out of the shed without rooftop and then led to pasture or areas overgrown with natural grass for grazing. Drinking water for the calves during grazing was available in the ponds around grazing areas. In the afternoon, the calves were driven back into the shed without a rooftop.

measurements anD Data collection
The measured variables consist of feed intake and apparent nutrient digestibility. Flushing diet intake was calculated by subtracting the refusals from the offered. Apparent nutrient digestibility was determined by internal (lignin) indicator and calculated based on the formula of Zewdie (2019) as follows:

Digestion coefficient of nutrient = 100 -100 x (% Indicator in feed x % Nutrient in feces) x (% Indicator in feces x % Nutrient in feed) -1
The refusals of flushing diets from each calf were weighed after the feeding time, put in a polyethylene bag, and airdried on the next day. Field grass samples were collected randomly from 30 points (Cayley and Bird, 1996) where 30 calves grazed on pasture. The grass sample was taken as much as 100 grams from each point where the grass was taken so that the total sample of natural grass collected was 3 kg and air-dried. Fecal samples from each calf

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Journal of Animal Health and Production
January 2021 | Volume 9 | Issue 1 | Page 54 were collected from the pasture every day between 1100 and 1600 h. Daily fecal samples that had been collected were put into polyethylene bags that had been numbered according to the number of each calf and then air-dried on the next day. The dried offer and refusal flushing diets, field grass, and fecal samples were then ground to pass a 1 mm screen mill for proximate analysis. The proximate analysis was carried out according to (AOAC, 2016) procedures. Neutral detergent fiber (NDF), Acid detergent fiber (ADF), cellulose, and lignin contents were analyzed according to (Van Soest et al. 1991). Hemicellulose was calculated by subtracting ADF from NDF.

statistical analysis
All variables (dry matter intake of the flushing diets, apparent digestibility of nutrients,) were analyzed by General Linear Model Univariate Analysis (IBM SPSS Statistics 24, 2018). All dietary treatments and calf gender (male and female) were considered as fixed factors. All dietary treatments and gender main effects were subject to the least significant difference (LSD) test option. The result of each variable analysis was considered as statistically significant if P ≤ 0.05. The statistical model applied for analyses was: Where, Yijk is dependent variable; µ is the overall mean; αi is the effect of gender; βj is the effect of dietary treatment; (αβ)ij is the effect of the interaction between gender and dietary treatment; εijk is the overall error term.

FeeD intaKe
Average flushing concentrates intake (dry matter basis) of the preweaning calves for 60 days ranged within 0.50±0.03 -0.58±0.07 kg/d ( Table 2). Average flushing concentrates intake in the recent study reached 1.44 % and 1.40 % BW of male and female, respectively. There was no significant difference in the concentrate intake between flushing-1 and flushing-2 diets in male and female Pasundan calves reared in a cow-calf system under extensive grazing.

Journal of Animal Health and Production
January 2021 | Volume 9 | Issue 1 | Page 55
Lower DMD in grazing calves was in relation to the low quality of native grass in the grazing area as generally found in tropical pasture regions. This is supported by Labussiere et al. (2009) who described fibrous feed decreased DM digestibility. In addition, preweaning calves have a low capacity to digest fiber, because its rumen development is not yet complete. Lower fiber digestibility (NDFD, ADFD, CELD) in grazing calves as shown in Table 3  The OMD similarity between grazing calves and flushing calves is still not well explained. This was unexpected because it was previously predicted that the grazing calves would have lower OMD than the flushing calves. Presumably, the grazing calves have adapted well to the condition of the grass in the grazing area so that the grazing calves are able to digest the OM as well as the flushing calves. Even if the OM content in native grass is the same as the OM in flushing concentrates, it does not warrant that the grazing calves would have similar OMD to the flushing calves because the OM compositions in native grass differ with the OM compositions in the flushing concentrates.
Ghassemi Nejad et al. (2012) reported that differences in form of calf starter affected nutrients digestibility; calves fed mashed starter indicated lower OMD (78.6%) than the OMD of calves fed pelleted starter (85.0%) or texturized starter (86.6%). The OMD in this study was slightly higher than the OMD (79.80%) obtained by Chapman et al. (2017) who fed a calf starter (20% CP) but it was comparable with the OMD (88% -91.1%) reported by de Assis Lage et al. (2019). Lower fiber (NDF, ADF, cellulose) digestibility in the grazing calves indicates that the fiber less availability for microbial fermentation. One explanation for this occurrence is in relation with lignin content as proposed by Maskaľová and Vajda (2015) who described that lignin encrusting the fiber, complexing with other nutrients, and resulted in lower fiber digestibility. Supplementing flushing-1 or flushing-2 concentrates improve the fiber digestibility. This improvement may associate with a greater surface area of the small particle size of the flushing concentrates. This explanation is in accordance to Ghassemi Nejad et al. (2012) who explained that the small particle size of feed increased the surface area for microbial enzyme to access the feed particles. Apparently, feed grinding not only increases the surface area of feed particle, but also may destroy lignocellulose complex that increases microbial access to digest the fiber contained in the fibrous feeds, thus increases the fiber digestibility. The NDF digestibility in both flushing calves was comparable with the in vitro NDF digestibility (83.5%) obtained by Marumo et al. (2018) who used a commercial pelleted calf meal, but it was higher than the NDF digestibility (40.5 -68.7%) obtained by some authors (Hill et al., 2016;Casper et al., 2017;Chapman et al., 2017;de Assis Lage et al., 2019) who fed the calves with milk replacer or calf starter.

CONCLUSIONS AND RECOMMEDATIONS
Supplementing flushing diet to preweaning Pasundan calves under extensive grazing improved most nutrient digestibility parameters (dry matter, crude protein, ether extract, and fiber). It is recommended that preweaning calves under extensive grazing should be provided flushing diets to improve the nutrient digestibility.