The Effect of Wheat Bran on the Total Apparent Digestibility of Dry Matter, NDF, ADF and CP in Goat Diets

The aim of this study was to evaluate the effect of wheat bran in increasing amounts on the total apparent dry matter digestibility (DM), the fiber (NDF, ADF) and the protein (CP) in goat diets. Eight Criollo x Nubian goats were used in a 4x4 Latin square experimental design. Four diets were provided: alfalfa hay (D0); alfalfa hay + wheat bran (WB) (0.5% of BW/day) (D1), alfalfa hay + WB (1% of BW/day) (D2) and alfalfa hay + WB (1.5% of BW/day) (D3). All the treatments consisted of alfalfa hay delivered ad libitum. In vivo total apparent digestibility of the DM intake and its fractions was calculated as a result of the difference between the ingested and excreted amounts in relation to the intake. Forage intake and the relation forage/concentrate decreased linearly (p < 0.05) with the increase of the concentrate. Energy intake increased linearly (p < 0.05) with larger amounts of WB. The total apparent digestibility of the ingested DM showed a significant linear increase (p < 0.05) with the increase of concentrate. The digestibility of NDF, ADF and CP registered no differences (p > 0.05) with the WB increase in the different treatments. We can conclude that the addition of WB in Criollo x Nubian goats improved the total apparent digestibility of the ingested DM by replacing hay for concentrate, without altering NDF, ADF and CP fractions. Introduction Success in ruminant production is explained, to a significant extent, by the animal’s capacity to digest fibrous vegetal materials. Microorganisms being able to degrade this kind of materials constitute a significant advantage over other animals in nature. However, high productivity levels cannot be sustained by forage only, therefore, agriculture products are often used in livestock farming (Russell y Rychlik, 2001). Digestibility is mostly an inherent property of forage, whereas voluntary intake is a function of animals and the forage and environment under which they are fed (Coleman et al., 1999). To know the forage digestibility is not useful unless knowing the amount animals will ingest (Ørskov & Ryle, 1990). The combination of both in vivo apparent digestibility of dry matter and dry matter intake results in the digestible dry matter intake. This value provides a more effective means for the assessment of feed potential than either of them separately (Coleman et al., 1999). The extent to which concentrates affect fiber digestion may depend on their nature and proportion, as well as on the forage quality (Matejovsky y Sanson, 1995). The incorporation of cereals in ruminant diets alters the rumen microflora, causing alterations in the fermentation patterns, and in the rumen and host animal’s health (Russell & Rychlik, 2001). An increase of the total digestibility may be expected as a result of the incorporation of concentrate to the diet. The energy provided by the concentrate (fermentable carbohydrates) may reduce rumen pH, the activity or number of cellulolytic bacteria, the rate of pasture fiber digestion and, therefore, the DM intake (Dixon & Stockdale, 1999). From the nutritional point of view, wheat bran can be considered a protein-energetic feed of intermediate values both in energy and protein. As it is a byproduct of flour extraction (starch), its energetic value fundamentally comes from the fiber of grain hulls. It is also a by-product with a low amount of ADF, due to the low content of lignin and high content of hemicelluloses, compared to hay or other fiber feeds (FEDNA, 2018). The energetic value of wheat bran is 22 % lower than the one found in corn grain; it is also lower in digestibility, for it has a lower amount of starch (Gallardo, 2006). Extensive goat production is based on the use of forage. Alfalfa is considered a valued forage in goat feeding due to its high protein content and lower neutral detergent fiber (NDF) concentration, compared to other forage species. Its high content of high degradability soluble fiber and low content of NDF have a positive effect on dry matter intake The Effect of Wheat Bran on the Total Apparent Digestibility of Dry Matter, NDF, ADF and CP in Goat Diets http://www.ijSciences.com Volume 8 – October 2019 (10) 7 (Rapetti, 2005). However, and due to the emergence of a more technical system, there is a tendency to the intensification and increase in the use of concentrate products to keep up with the high productivity levels (Castel et al., 2003). Goats change their feeding behavior according to forage or concentrate availability, and they have the capacity of selecting food of high protein and digestibility levels (Provenza et al., 2003). When they receive supplements, dry matter intake decreases, and this is known as substitution rate (Kellaway & Porta, 1993; Stock dale, 2000). The incorporation of corn grain to ruminant feed increases the digestibility of the total ingested dry matter (Molina & Alcaide et al., 2000, Fimbres et al., 2002), but it might decrease forage digestibility (Archimède et al., 1995). There is certain controversy on the effect of concentrate incorporation on the digestibility of forage components, according to the kind of concentrate, rumen pH and total and relative amount of different volatile fatty acids. For example, rich NDF feed such as hay and mature pastures induce pH between 6.5 and 8, which is an optimum environment for celluloysis with predominant acetic acid (Aello & Di Marco, 2000). There are numerous studies which prove that the incorporation of concentrate in diets has positive effects on forage digestibility, until it reaches certain proportion at which such effect is lost, or even negative (Chandramoni et al., 2000; Goetsch et al., 2001; Dung et al., 2005; Liu et al., 2005; Lefrileux et al., 2008). Many authors claim that ruminant diets with high content of starch reduce fiber digestion due to a microbial fermentation of nonstructural carbohydrates, a reduction of rumen pH and a lower cellulolytic activity (Mould & Orskov 1984; Kovacik et al., 1986; Grant & Mertens, 1992; Garces-Yepez et al., 1997). Moore et al., (2002) found no significant differences in rumen pH, NDF and ADF digestibility in Boer goats and diets based on orchardgrass hay and a concentrate mixture (wheat bran, soy beans hull and corn gluten) incorporated to 1 % of BW. Cantalapiedra et al., (2009) studied the effect of two diets on Granadina goats. These diets contained different forage/concentrate proportions (70/30 y 30/70) consisting of alfalfa hay and a mixture of barley grain, gluten meal, wheat bran, and soy derivates. Studies showed an increase of total dry matter digestibility from 67 % to 74 % and of NDF from 55 % to 67 %, in those diets with higher relative amount of concentrate. Contrarily, results showed no effect of diets on rumen pH and crude protein digestibility. Additionally, the incorporation of corn in increasing quantities, up to 1.5 % DM/BW, in alfalfa hay diets for crossbreed goats (Criollo x Nubian), decreased rumen pH under 6, affecting rumen degradability of forage fiber (Arias et al., 2013). Moreover, total NDF and ADF digestibility of the ingested diet was affected (Arias et al., 2015). Goat feeding behavior is different from other ruminants’ as regards diet selection and intake (Lu et al, 2005). For this reason, knowledge and information obtained of different species cannot be extrapolated to this particular one. The objective of this study was to evaluate the effect of increasing amounts of wheat bran on the total apparent digestibility of dry matter, NDF, ADF and CP, in goat diets. Method and Materials: This study was carried out in the Experimental Unit of the School of Forest and Agricultural Sciences of the National University of La Plata (UNLP). Animals Eight five year old crossbreed (Criollo x Nubian) non-pregnant and dry goats of 44.64 ± 1.49 kg of average BW were used. The experimental design was a duplicated 4x4 Latin square with 7 days of wash out in between terms. When determinations were carried out, the goats were put in individual boxes (0.80 m x 1.50 m) with slatted wooden flooring, feeding troughs, slow feeders and automatic nipple drinkers with free access to water. Each animal’s weight was registered at the beginning of each term. Treatments Four diets containing alfalfa hay (D0), alfalfa hay + wheat bran (0.5 % of BW/day) (D1), alfalfa hay + wheat bran (1 % of BW/day) (D2) and alfalfa hay + wheat bran (1.5 % of BW/day) (D3) were provided. In all the treatments, alfalfa hay was delivered ad libitum. A 15-day adaptation period was implemented before sampling. The amount of wheat bran was delivered in an increasing manner, starting from 70 g per animal per day, until reaching each treatment’s proportions at the beginning of the second week of the adaptation period. Diets were delivered once a day at 9 am each day. Alfalfa hay and wheat bran DM were determined by drying method (SOMCIC) to 90-95 oC for 24 hours, (AOAC, 1995). Chemical composition of the ingredients used was determined according to AOAC (1995). Determination of DM total intake and in vivo total apparent digestibility of DM and its fractions (NDF, ADF and BW) The individual intake of DM and its fractions (NDF, ADF ME and CP) was determined by means of the difference between the delivered and rejected feed, during the 4 days of waste collection, after the The Effect of Wheat Bran on the Total Apparent Digestibility of Dry Matter, NDF, ADF and CP in Goat Diets http://www.ijSciences.com Volume 8 – October 2019 (10) 8 adaptation period to the different diets. Stool was collected and quantified using a collecting bag system and a harness. Bags were emptied once a day and the total amount of stool was weighed. A subsample consisting of 10 % of each animal’s excreted material was frozen at – 20 oC for further chemical analyses. In vivo total apparent digestibility (IVTAD) of the DM intake and its fractions was calculated from the difference between the ingested and excreted feed in relation to the ingeste


Introduction
Success in ruminant production is explained, to a significant extent, by the animal's capacity to digest fibrous vegetal materials. Microorganisms being able to degrade this kind of materials constitute a significant advantage over other animals in nature. However, high productivity levels cannot be sustained by forage only, therefore, agriculture products are often used in livestock farming (Russell y Rychlik, 2001).
Digestibility is mostly an inherent property of forage, whereas voluntary intake is a function of animals and the forage and environment under which they are fed (Coleman et al., 1999). To know the forage digestibility is not useful unless knowing the amount animals will ingest (Ørskov & Ryle, 1990). The combination of both in vivo apparent digestibility of dry matter and dry matter intake results in the digestible dry matter intake. This value provides a more effective means for the assessment of feed potential than either of them separately (Coleman et al., 1999).
The extent to which concentrates affect fiber digestion may depend on their nature and proportion, as well as on the forage quality (Matejovsky y Sanson, 1995). The incorporation of cereals in ruminant diets alters the rumen microflora, causing alterations in the fermentation patterns, and in the rumen and host animal's health (Russell & Rychlik, 2001).
An increase of the total digestibility may be expected as a result of the incorporation of concentrate to the diet. The energy provided by the concentrate (fermentable carbohydrates) may reduce rumen pH, the activity or number of cellulolytic bacteria, the rate of pasture fiber digestion and, therefore, the DM intake (Dixon & Stockdale, 1999).
From the nutritional point of view, wheat bran can be considered a protein-energetic feed of intermediate values both in energy and protein. As it is a byproduct of flour extraction (starch), its energetic value fundamentally comes from the fiber of grain hulls. It is also a by-product with a low amount of ADF, due to the low content of lignin and high content of hemicelluloses, compared to hay or other fiber feeds (FEDNA, 2018). The energetic value of wheat bran is 22 % lower than the one found in corn grain; it is also lower in digestibility, for it has a lower amount of starch (Gallardo, 2006).
Extensive goat production is based on the use of forage. Alfalfa is considered a valued forage in goat feeding due to its high protein content and lower neutral detergent fiber (NDF) concentration, compared to other forage species. Its high content of high degradability soluble fiber and low content of NDF have a positive effect on dry matter intake (Rapetti, 2005). However, and due to the emergence of a more technical system, there is a tendency to the intensification and increase in the use of concentrate products to keep up with the high productivity levels (Castel et al., 2003).
Goats change their feeding behavior according to forage or concentrate availability, and they have the capacity of selecting food of high protein and digestibility levels (Provenza et al., 2003). When they receive supplements, dry matter intake decreases, and this is known as substitution rate (Kellaway & Porta, 1993;Stock dale, 2000).
The incorporation of corn grain to ruminant feed increases the digestibility of the total ingested dry matter (Molina & Alcaide et al., , Fimbres et al., 2002, but it might decrease forage digestibility (Archimède et al., 1995). There is certain controversy on the effect of concentrate incorporation on the digestibility of forage components, according to the kind of concentrate, rumen pH and total and relative amount of different volatile fatty acids. For example, rich NDF feed such as hay and mature pastures induce pH between 6.5 and 8, which is an optimum environment for celluloysis with predominant acetic acid (Aello & Di Marco, 2000). There are numerous studies which prove that the incorporation of concentrate in diets has positive effects on forage digestibility, until it reaches certain proportion at which such effect is lost, or even negative Moore et al., (2002) found no significant differences in rumen pH, NDF and ADF digestibility in Boer goats and diets based on orchardgrass hay and a concentrate mixture (wheat bran, soy beans hull and corn gluten) incorporated to 1 % of BW.
Cantalapiedra et al., (2009) studied the effect of two diets on Granadina goats. These diets contained different forage/concentrate proportions (70/30 y 30/70) consisting of alfalfa hay and a mixture of barley grain, gluten meal, wheat bran, and soy derivates. Studies showed an increase of total dry matter digestibility from 67 % to 74 % and of NDF from 55 % to 67 %, in those diets with higher relative amount of concentrate. Contrarily, results showed no effect of diets on rumen pH and crude protein digestibility. Additionally, the incorporation of corn in increasing quantities, up to 1.5 % DM/BW, in alfalfa hay diets for crossbreed goats (Criollo x Nubian), decreased rumen pH under 6, affecting rumen degradability of forage fiber (Arias et al., 2013). Moreover, total NDF and ADF digestibility of the ingested diet was affected (Arias et al., 2015).
Goat feeding behavior is different from other ruminants' as regards diet selection and intake (Lu et al, 2005). For this reason, knowledge and information obtained of different species cannot be extrapolated to this particular one. The objective of this study was to evaluate the effect of increasing amounts of wheat bran on the total apparent digestibility of dry matter, NDF, ADF and CP, in goat diets.

Method and Materials:
This study was carried out in the Experimental Unit of the School of Forest and Agricultural Sciences of the National University of La Plata (UNLP).

Animals
Eight five year old crossbreed (Criollo x Nubian) non-pregnant and dry goats of 44.64 ± 1.49 kg of average BW were used. The experimental design was a duplicated 4x4 Latin square with 7 days of wash out in between terms. When determinations were carried out, the goats were put in individual boxes (0.80 m x 1.50 m) with slatted wooden flooring, feeding troughs, slow feeders and automatic nipple drinkers with free access to water. Each animal's weight was registered at the beginning of each term.

Treatments
Four diets containing alfalfa hay (D 0 ), alfalfa hay + wheat bran (0.5 % of BW/day) (D 1 ), alfalfa hay + wheat bran (1 % of BW/day) (D 2 ) and alfalfa hay + wheat bran (1.5 % of BW/day) (D 3 ) were provided. In all the treatments, alfalfa hay was delivered ad libitum. A 15-day adaptation period was implemented before sampling. The amount of wheat bran was delivered in an increasing manner, starting from 70 g per animal per day, until reaching each treatment's proportions at the beginning of the second week of the adaptation period. Diets were delivered once a day at 9 am each day. Alfalfa hay and wheat bran DM were determined by drying method (SOMCIC) to 90-95 ºC for 24 hours, (AOAC, 1995). Chemical composition of the ingredients used was determined according to AOAC (1995).

Determination of DM total intake and in vivo total apparent digestibility of DM and its fractions (NDF, ADF and BW)
The individual intake of DM and its fractions (NDF, ADF ME and CP) was determined by means of the difference between the delivered and rejected feed, during the 4 days of waste collection, after the adaptation period to the different diets. Stool was collected and quantified using a collecting bag system and a harness. Bags were emptied once a day and the total amount of stool was weighed. A subsample consisting of 10 % of each animal's excreted material was frozen at -20 ºC for further chemical analyses. In vivo total apparent digestibility (IVTAD) of the DM intake and its fractions was calculated from the difference between the ingested and excreted feed in relation to the ingested, expressed in percent (%).

Rumen pH determination
The four goats were put a rumen fistula with permanent Bar Diamond Inc. cannulas of a 5" diameter. Rumen liquor was removed by cannula with vacuum pump at 0, 2 and 4 hours after feed ration. Collected samples were filtered using four cheesecloth layers. pH was determined using a digital pH meter (Silver Cap pH 5045-3B) equipped with puncture electrode and thermoprobe calibrated with buffer solution at pH 4 and 7. The area under the curve was calculated as the sum of partial areas defined by the absolute value of the deviation below pH 6 and the real time interval between subsequent sampling, covering a 4 hours total span, accounted as pH × sampling time / day. The average value of rumen pH and the time in hours with pH below 6 were calculated. Also, the effect of time after feed and the hour/treatment interaction were calculated by means of a repeated measure design.

Chemical analyses
Each stool sample consisted of subsamples from four days of collection later ground using a 1 mm mesh.
To determine ADF and NDF, the technique of Van Soest (1991) later modified by Komarek (1994) was used, with a fiber analyzing equipment Ankom 200. Thermostable α-amylase (Sigma A3306) and sodium sulfite were used for determining NDF. Total nitrogen was determined according to Kjeldahl-N method, (AOAC, 1995) multiplied by 6.25 to obtain the value of CP.

Statistical analyses
To assess the effect of wheat bran increasing levels on the total dry matter intake (TDMI), of forage (DMFI), NDF (TNDFI), ADF (TADFI), metabolizable energy (TMEI), crude protein (TCPI), forage/concentrate relation (F/C), and the IVTAD of DM, NDF, ADF and CP of the different diets, we used the model found below: Y = µ + T + EU + P + e Y: independent variable µ: trials general mean T: treatment EU: experimental unit P: period e: error Data were analyzed by MIXED SAS procedure (SAS, 2004) for a Latin 4x4 replicated square, using a mixed model which included the fixed sampling effect (treatment, period) and the random effect of the animal. Polynomial orthogonal contrasts were used to determine the linear effects (L), quadratic (Q) and cubic (C) of increasing levels of wheat bran. Tuckey test was used for the means comparison analysis. Significant differences were considered with a value p <0.05 and the tendencies with a p value between 0.05 y 0.10.

Results and Discusion
After assessment of the effect of increasing amounts of wheat bran using polynomial orthogonal contrasts, no significant differences were observed on the TDMI, TCPI, TNDFI (p > 0.05). A linear decrease (p < 0.05) of FDMI and TADFI was evidenced. The increase of the concentrate in the ration caused a linear decline (p < 0.05) of the F/C, and registered an evident substitutive effect of alfalfa hay by the flour industry by-product. TMEI increased linearly (p < 0.05) with larger amounts of concentrate. Using the means analysis, we proved that FDMI of D 2 y D 3 was significantly lower (p < 0.05) than D 0. Diets D 1 , D 2 and D 3 registered the highest intake of metabolizable energy (p < 0.05) with respect to D 0 ( Table 2).
As regards the IVTAD of the ingested DM, a significant linear increase (p < 0.05) was observed with the increase of the concentrate. Digestibility of fractions NDF, ADF and CP verified no significant differences (p > 0.05) with the increase of wheat bran amount in the different treatments (Table 3) Average rumen pH decreased linearly (p = 0.001) with wheat bran amounts between 0 and 1.5 % DM/BW. Diet D 3 registered the lowest average pH compared to the rest of the treatments (Figure 1). The areas under the curve of pH threshold 6 and hours with pH below 6 were value 0, because rumen pH values were above 6 in the 4 hour span after feed. By means of a repeated measure in time design, an effect of the hours (p = 0.001) was verified in the daily evolution of rumen pH. From the two hours after the ration intake, a significant interaction was observed (p = 0.04) hour/treatment on rumen pH ( Figure 2).
As Provenza et al., (2003) claimed, goats changed their feeding behavior according to the forage or concentrate availability, accepting and ingesting the total amount of the different quantities of tested bran. Goats receiving supplement caused dry matter intake of the forage to decrease due to a substitutive effect of alfalfa hay by the flour industry waste product, as Kellaway & Porta (1993) and Stockdale (2000) stated. The highest energy intake in diets with increasing amounts of wheat bran is the result of this flour by-product containing a high energy value, given by grain hulls.
From the nutritional point of view, wheat bran can be defined as a protein-energetic type of feed, with intermediate values both in energy and proteins (Gallardo, 2006). For this reason, CP values remained constant. The lowest ADF intake in diets with wheat bran was the result of it containing 62.7 % less of this fraction compared to alfalfa hay (FEDNA, 2018). ). Such effect might explain the lack of negative effects on fiber digestibility, probably by contributing to create an optimum mean for cellulolysis in general, and the predominance of acetic acid in particular (Aello & Di Marco, 2000).

Conclusion
Therefore, we can conclude that the incorporation of wheat bran to an alfalfa hay diet ad libitum in Criollo x Nubian goats, in the tested quantities, has improved the total apparent digestibility of the dry matter intake by an evident substitutive effect of the hay by the concentrate, without affecting NDF, ADF and CP fractions.  L: Probability value associated to a linear effect of the supplementation level with wheat bran in a polynomial orthogonal contrast. Q: Probability value associated to a quadratic effect of the supplementation level with wheat bran in a polynomial orthogonal contrast. C: Probability value associated to a cubic effect of the supplementation level with wheat bran in a polynomial orthogonal contrast. P value: Same letters indicate non-significant differences for a 5 % of probability. IVDMTAD: total apparent digestibility in vivo of dry matter, expressed in percent. IVNFDTAD: total apparent digestibility in vivo of neutral detergent fiber, expressed in percent. IVADFTAD: total apparent digestibility in vivo of acid detergent fiber, expressed in percent.. IVCPTAD: total apparent digestibility in vivo of crude protein, expressed in percent. SE: Standard Error. L: Probability value associated to a linear effect of the supplementation level with wheat bran in a polynomial orthogonal contrast. Q: Probability value associated to a quadratic effect of the supplementation level with wheat bran in a polynomial orthogonal contrast. C: Probability value associated to a cubic effect of the supplementation level with wheat bran in a polynomial orthogonal contrast. P value: Same letters indicate non-significant differences for a 5 % of probability.