Milk production performance of dairy goats fed dried grape pomace
Renna M1, Lussiana C2, Malfatto VM2, Calvo E2, Mimosi A2, Cornale P2
1Department of Veterinary Science, University of Turin, Italy; 2Department of Agricultural, Forest and Food
Sciences, University of Turin, Italy. e-mail: [email protected].
Introduction. Grape (Vitis vinifera L.) pomace (GP), a by-product of the winemaking and
juice industries, is a good source of phytochemicals, fatty acids, sugars, and lignocellulosic material [1]. Various studies assessed the use of GP as a potential feed ingredient in ruminant nutrition [2,3], but only scant information is available for goats [4]. We investigated the effect of dried GP inclusion in the diet of dairy goats on their dry matter intake (DMI), milk yield, milk main constituents, and feed efficiency.
Animals, material and methods. Twenty-four Camosciata delle Alpi goats were divided
into two groups. The first group (control, CON) was fed with mixed hay ad libitum and 0.8 kg/head per day of concentrate. In the second group (dried grape pomace, DGP), 0.15 kg/head per day of concentrate were substituted with DGP (on a DM basis: 10.9% CP; 7.9% EE; 49.9% NDF; 22.6% ADL; NEL: 1.27 Mcal/kg). Every ten days individual DMI and milk yield were recorded, and individual milk samples were collected and analyzed for fat, protein, casein, lactose and urea. Feed efficiency was calculated as milk yield (kg)/DMI (kg). Data were statistically treated using a MIXED procedure for repeated measures over time [5].
Results and discussion. As previously observed in dairy cows and ewes [2,3], DGP did
not negatively affect DMI in dairy goats (Table 1). The goats fed DGP showed increased milk yield and higher daily milk protein yield, confirming previous results obtained in dairy cows [2]. Grape by-products contain high concentrations of tannins, which are able to reduce methanogenesis [6] thus limiting dietary energy losses and improving feed efficiency [7]. Tannins are also able to bind with proteins, thus reducing protein solubility and protein ruminal degradation, consequently increasing protein availability at intestinal level [6], with an overall improvement of nitrogen utilization for milk production [8].
Table 1. Milk production performance of dairy goats fed the CON and DGP diets.
Item CON DGP DT# Item CO N DGP DT# DMI (kg/head×day) 2.32 2.39 ns Milk yield (kg/head*day) 2.24 2.71 * Milk composition (g/kg) Component yield (g/day) Fat 29.3 30.4 ns Fat 66.9 69.4 ns Protein 32.2 31.8 ns Protein 70.6 85.4 ** Casein 25.4 25.3 ns Casein 55.7 68.0 ** Lactose 42.7 43.0 ns Lactose 95.2 116.4 **
Urea (mg/dL) 39.2 30.1 *** Feed efficiency 0.97 1.14 *
***p < 0.001; **p < 0.01; *p < 0.05; ns, not significant; # DT, dietary treatment.
Conclusion. DGP can be used as feed ingredient in diets for dairy goats, with favorable
effects on feed efficiency and nitrogen utilization. Benefits may also include reduced feeding costs for the farmers, reduced greenhouse gas emissions by livestock activities, and increased circular economy in the agri-food sector.
References: [1] Muhlack et al. (2018) Waste Manage. 72: 99-118; [2] Gessner et al. (2015) J. Dairy Sci. 98:
8856-68; [3] Manso et al. (2016) J. Dairy Sci. 99: 1111-20; [4] Tsiplakou and Zervas (2008) J. Dairy Res. 75: 270-8; [5] SAS (2008) SAS User’s Guide: Statistics, Version 9·1·3. Cary, NC, USA; [6] Moate et al. (2014) J. Dairy Sci. 97: 5073-87; [7] Haque (2018) J. Anim. Sci. Technol. 60: 15; [8] Molle et al. (2008) Small Rum. Res. 77: 93-112.
