Role of Nutrition in Body Weight Gain and Early Onset of Puberty and Sexual Maturity in (HF X Kankrej) Crossbred Heifers
Arjan J Dhami Kamlesh K Hadiya Dinesh V Chaudhari Pravin M Lunagariya Nilesh P Sarvaiya Shailesh V Shah
Feeding of high plane of nutrition to growing heifers from early age is expected to economically shorten the age at puberty/sexual maturity and thereby the age at first calving. This experiment was initiated on 24 Holstein x Kankrej crossbred heifers of nearly identical age (7-9 months) and body weight (140-156 kg) at University farm. Twelve heifers were managed under routine farm feeding (control) and the rest 12 under ideal optiumum feeding regime (treatment) that included extra 1 kg concentrate, 30 g min mix and ad lib dry fodder. Body weight at monthly interval and actual age at puberty/first estrus and sexual maturity/conception were recorded for each animal in both the groups. Ovarian ultrasonography together with blood sampling was carried out at monthly interval from 10 to 18 months of age to study the ovarian dynamics and endocrine changes including thyroid hormones profile. There was gradual, consistent and significant (p<0.05) increase in the monthly body weight gain in heifers of treatment group over control group with advancing age till 18 months of age by which nearly 60% heifers had evinced puberty and were bred. The plasma progesterone and estradiol concentrations monitored from 10 months revealed lower or basal levels till 12-13 months of age with follicles <5 mm size, and thereafter most of the heifers showed presence of 2-5 follicles >8 mm in diameter, but ovulatory follicle / CLs were noticed in only a few animals around 15 months, and by about 17-18 months 50 and 75% heifers of control and treatment groups had ovulatory follicles >12 mm or CL >10 mm upon USG examination concurrent with elevated plasma progesterone concentrations. Thyroid hormones also showed rising trend with advancing age and showed almost stable profile from 17 months of age onward. One heifer in each group showed consistent true anestrus with small smooth inactivity ovaries, and one evinced repeat breeding with large flabby flat ovaries, hence were excluded from calculation of pubertal age. The mean age at puberty and sexual maturity (fertile estrus) worked out for remaining 10 animals in each group were 22.23±0.45 and 24.72±0.89 months in control and 20.40±0.45 and 23.17±0.60 months in treatment group, respectively. These data indicated that high plane of nutrition from early age shortened the age at puberty and sexual maturity by nearly two months in HFxK crossbred heifers.
Keywords : Age at puberty/maturity Body weight gain Crossbred heifer Ovarian ultrasonography Plane of nutrition Plasma endocrine profile
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