اثر شکل فیزیکی کنسانتره خوراک بر عملکرد تولیدی، رفتار تغذیه ای و فراسنجه های خونی بزهای شیرده نژاد مورسیانوگرانادینا

Introduction
Human demand for goat milk and its products has been growing mainly because of their exclusive nutritional properties. Goat milk is rich in functional and healthy compounds such as bioactive peptides, conjugated linoleic acids and oligosaccharides. These nutritionally important compounds offer advantages for consumers of goat dairy products. Altered climatic conditions and decreased precipitations in many regions have led goat farmers to intensify and industrialize their production systems. For goat nutrition under intensive production systems, physical form of ration would be of productive and economic significance. The objective of this study was to investigate the effect of feeding various physical forms of concentrate (mash, pelleted and textured) on milk production, nutritional behaviors, and blood parameteres of Murciano_Granadina dairy goats in Iran.
Material and Methods
This experiment was conducted in Magsal Commercial Dairy Goat Farm (4000 dairy goats; Qazvin, Iran) from January through March 2020. Thirty second parity goats in mid lactation (Murciano_Granadina) assigned to 3 treatments (10 goats per treatment). Treatments containing concentrate with form of 1) mash, 2) pelleted, or 3) textured. Feed and milk samples (from a.m. and p.m. milkings) were collected weekly for later analytical measurements. Feed was analyzed for NDF, crude protein, ether extract, and ash. Goats were weighed weekly just before the morning feed delivery. Milk samples were analyzed for fat, protein, lactose, total solids, solids-nonfat, urea nitrogen, and total fatty acids . The data were analyzed using mixed models of SAS program.
Results and Discussion
Raw and 3.5% fat-corrected milk yields were greater (P < 0.01) for T or textured (1653 and 2074 g/d) than for P or pelleted (1372 and 1752 g/d) and M or mashed (1089 and 1439 g/d), respectively. Because of unchanged milk composition (P > 0.10), daily yields of milk fat, protein, lactose, SNF and total solids were also greater (P < 0.01) for T than for other treatments. As a result of increased total milk fat, protein, and solids yields, cheese yield estimates were greater (P < 0.01) for T than for other forms of concentrate. For example, milk fat yield was 17% and 36% greater for T than for P and M, respectively. These results demonstrated that goats fed T had better energy and nutrient balance than goats fed other treatments (Sanz Sampelayo et al., 1998). These data alongside feed sorting results suggest that feeding M (and likely P) might have adversely affected rumen conditions. Pelleting concentrate may increase the likelihood of subacute ruminal acidosis (Ebrahimi et al., 2020), and thus reduce nutrient intake and microbial protein synthesis. The present data for the first time reports that physical form of concentrate affects milk production of lactating dairy goats and that textured concentrate is superior to both pelleted and mashed concentrates.
Feeding P instead of M improved yields of fat-corrected milk and milk protein, lactose, and total solids as well as feed efficiency (P < 0.05). In addition, orts were finer containing more concentrate for M than for P (P < 0.05). These data suggest that feeding P instead of M concentrate resulted in decreased feed sorting and improved nutrient assimilation by lactating dairy goats. Notable, dry matter intake was similar between M and P (P > 0.10), emphasizing the increased orts fineness and improved feed efficiency for P vs. M. It is obvious that because of more sorting, less concentrate (than predicted) was consumed for M than for P. It is also likely that M was degraded more rapidly in the rumen, suggesting induced ruminal acidosis. This cascade could reduce nutrient efficiency in M-fed goats than in other goats.
In dairy cows, feeding steam-flaked corn grains instead of ground or dry-rolled grains have improved (Cooke et al., 2008; Yu et al., 1988), tended to improve (Zhong et al., 2008), or not affected (Shen et al., 2015; Dhiman et al., 2002) milk production. Steam-flaking and texturizing are to some extent similar, as they both produce feeds with larger and more uniform particles, when compared to grinding or dry-rolling. The improved milk production of goats fed T in the current study is consistent with the above-mentioned increases in milk production of cows fed steam-flaked corn grains. Feed efficiency or FCM to DMI ratio was improved by feeding T and P instead of M, which was due to the much improved milk yield in the T and P groups than in the M group. Milk urea N was similar among the treatments, probably suggesting that rumen ammonia and splanchnic urea outputs were not significantly affected by the treatments.
Blood patameters (glucose, albumin, and NEFA) were not affected by treatments.
Murciano-Granadina goats separation less in textured treatment than other treatments. Under the conditions of this experiment, the use of textured concentrate in the diet of Murciano-Granadina lactating goats has more advantages for consumption of mash and pelleted concentrate and leads to increased milk production and composition and improved feed efficiency.
Conclusions
The commercial dairy goat production is expanding worldwide. Improving feed efficiency and farm economics is, thus, a major goal. Findings provided new information that feeding lactating Murciano-Granadina dairy goats TMR with textured concentrates instead of pelleted and mashed concentrates minimized feed sorting, increased dry matter intake and milk production, and improved cheese yield estimates and feed efficiency. Feeding pelleted vs. mashed concentrate improved milk production and feed efficiency. Blood concentrations of glucose, NEFA, albumin and total protein were not affected by the physical form of concentrate. Results confirmed that feeding textured concentrate vs. both pelleted and mashed concentrates can significantly benefit feed efficiency, milk production, and cheese yield in lactating Murciano-Granadina dairy goats. Future studies on optimizing physical form of concentrate in relation to dietary forage source are warranted.