Infradian rhythmicity in lactogenic hormone (prolactin,growth hormone,cortisol and thyroid hormone) secretion throughout the lactation cycle in mithun cows (Bos frontalis): variation among strains

The role of lactogenic hormones (prolactin, growth hormone, cortisol and thyroid hormone) on lactation yield in Mithun cows as well as their rhythmicity throughout the lactation cycle were studied in Mizoram (n = 4) and Nagaland (n = 7) strain of mithun (Bos frontalis). Blood samples were collected from all the animals from the day of calving to the complete dry off at an interval of 15 days. All the hormones were estimated in the serum by commercially available ELISA kits. Plasma level of cortisol (μg/dl), growth hormone (GH, in ng/ml), prolactin (PRL, in μIU/ml), triiodothyronine (T₃, in nmol/μl) and thyroxin (T₄, in ng/ml) were 20.84 ± 0.29, 28.08 ± 0.56, 9.87 ± 0.20, 27.82 ± 0.56 and 51.33 ± 0.48, respectively, in mithun irrespective of strains during the lactation period. Levels of all the hormones varied significantly (p ≤ 0.01) during different days of lactation cycle but, there was no significant difference among strain. Levels of PRL, GH, cortisol and T₃ were significantly (p < 0.01) higher around calving and declined sharply. The hormones remained in almost steady state during mid-lactation and declined during late lactation. All the hormones stated above were positively correlated with lactational yield thus their role on lactogenesis and galactopoiesis was established.     

Chemical composition and nutritional evaluation of various foliages consumed by mithun (Bos frontalis)

Mithun (Bos frontalis) is primarily reared in free-grazing systems and several tropical foliages are important feed resources for it throughout the year. Inadequate information is available on the nutritive value of most of these foliages. This study aimed to determine the nutrient composition and in situ degradability of dry matter (DM) and crude protein (CP) of the major foliages consumed by mithun. The foliages (n = 16) were collected from different mithun inhabited areas. The DM, CP, ether extract, neutral detergent fibre, acid detergent fibre, lignin(sa), ash and condensed tannin contents of the foliages varied from 236 to 398, 100 to 178, 10 to 40, 397 to 621, 287 to 460, 74 to 169, 92 to 176 and 12 to 68 g/kg DM, respectively. All foliages contained Ca and K at more than 10 g/kg DM and Mg at more than 1.7 g/kg DM, but were deficient in Na (i.e., <0.6 g/kg DM). The P content of the foliages ranged from 1.2 to 4.0 g/kg DM, and contents of Cu, Fe, Mn and Zn were ranged from 7.3 to 19.6, 119 to 460, 32 to 144 and 35 to 430 mg/kg DM, respectively. The degradability of DM and CP was greater in Daubanga grandiflora compared to the other experimental foliages. Among the foliages, the rapidly degradable fraction of DM and CP ranged from 49 to 219 and 86 to 217 g/kg DM, respectively. Simultaneously, the slowly degradable fraction of DM and CP ranged from 319 to 475 and 159 to 325 g/kg DM, respectively. The effective degradability of DM and CP ranged from 291 to 389 and 199 to 338 g/kg DM, respectively. The nutrient contents were adequate in most of the foliage, except Na, which was deficient in all the foliages and may explain observed salt seeking behavior of mithun reared under free grazing systems.