Evaluating varying dietary energy levels for optimum growth and early puberty in Sahiwal heifers

The study was designed to examine the effect of feeding diets with different energy levels for optimum growth and early puberty of heifers. twenty sahiwal heifers (age = 12 ± 2 months and avg. wt = 125 kg) were assigned to four dietary treatments having five animals on each treatment. iso-nitrogenous (cp=13.7%) diets having varying energy,viz; me 100% (control),me 88%,me 112% and me 124% of nrc (2001) recommended level for small breed non bred heifers were fed to the respective groups until the onset of puberty . dry matter and protein intakes were similar (p>0.05) across the dietary treatments. the optimum average daily gain (adg) was achieved during the period from 13 to 18 months of age. the overall adg was higher (571±15 g/d) in me 124% than of me 100,88 and 112%,whereas adg found to be lowest in me 88% (397±07 g/d). similar trend was observed in feed efficiency for different treatment groups. heifers fed dietary level of me 124% of nrc (2001) acquired higher body length,height and heart girth as compared to those fed other dietary energy levels. the digestibility of nutrients,age at puberty,age at 1st conception and serum progesterone were not influenced by dietary treatments (p>0.05). it is concluded that provision of higher dietary energy level (me 124% of nrc,2001 recommendation) enhanced growth parameters and feed efficiency but adequate reproductive performance of sahiwal heifers in terms of age at puberty was achieved even at lower dietary energy level (me 88% of nrc,2001 recommended level) under local environmental conditions of pakistan. copyright 2012 zoological society of pakistan.