Objectives of the present study were to evaluate the effects of supplementation of bypass fat on milk production and reproductive performance of crossbred cows. Nineteen multiparous crossbred cows (2-4 lactation) were divided in two groups on the basis of most probable production ability (MPPA). The animals in group 1 (nine cows, MPPA 3,441.32 kg, control group G1) were fed chaffed wheat straw, chopped green maize, and concentrate mixture as per requirements while the animals in group 2 (10 cows, MPPA 3,457.2 kg, treatment group G2) were fed the same ration supplemented with 2.5% bypass fat (on DMI basis). The cows of G2 were supplemented bypass fat 40 days prepartum to 90 days postpartum and carry over effect of supplementation on milk production and reproductive parameters was monitored up to 210 days of lactation. Average birth weights of the calves were 24.94 and 27.95 kg in G1 and G2, respectively. The calving per cent in G1 (88.88%) was lower than that of G2 (100%). The time taken for expulsion of fetal membranes was decreased (P<0.05) by 5.4 h in G2 compared to G1. Days required for involution of uterus was less (P<0.05) in G2 (35.40 days) than that of G1 (49.44 days). Less number of cases of retention of fetal membranes (RFM) and metritis were observed in G2 as compared to that of G1. The average milk yield (210 days) in G2 was higher (P<0.05) than that of G1 (18.65 vs 17.57 kg/day). Similarly, the milk yield during the carry over period (90 days) was higher (P<0.05) in G2 than that of G1 (14.81 vs 13.79 kg/day). The time required for onset of cyclicity was reduced (P<0.05) by 6.5 days in G2 as compared to that of G1. The service period and AI per conception were also reduced (P<0.05) in G2 while bypass fat feeding showed no effect on conception rate (P<0.80). There were no differences between the two groups in plasma cholesterol, progesterone and insulin concentrations. Hence, it was concluded that bypass fat supplementation at 2.5% of DMI increased the milk production and reduced the time required for involution of uterus and commencement of cyclicity. AI per conception, incidences of metritis and RFM were also reduced on supplementing bypass fat.

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The seasonal lack of availability of lush green forages can force dairy farmers in developing nations to rely on crop residues such as wheat and rice straw as the major feed source. We tested whether ammonia fiber expansion (AFEX) treatment of wheat straw would increase the energy available to Murrah buffalo and Karan-Fries cattle consuming 70% of their diet as wheat straw in India. Forty lactating animals of each species were blocked by parity and days in milk and randomly assigned to 1 of 4 treatment diets (n = 10). Treatments were a nutrient-rich diet with 0 to 20% straw (positive control; PC) and 3 high-straw diets with various levels of AFEX-treatment: (1) 70% untreated straw (no AFEX), (2) 40 to 45% untreated straw with 25 to 30% AFEX-treated straw (low AFEX), and (3) 20% untreated straw with 50% AFEX-treated straw (high AFEX). The AFEX-treated straw was pelleted. Urea was added to the no and low AFEX diets so they were isonitrogenous with the high AFEX diet. Animals were individually fed the PC diet for 14 d followed by 7 d of adaptation to treatments, full treatments for 28 to 35 d, and finally PC diets for 21 d. Compared with buffalo fed the PC diet, those fed high-straw diets consumed 29% less feed dry matter, put out 16% less milk energy, and lost 0.8 kg/d more body weight; the AFEX treatment of straw did not alter intake or milk production but greatly ameliorated the body weight loss (-1.0 kg/d for no AFEX and -0.07 kg/d for high AFEX). In Karan-Fries cattle, high-straw diets decreased dry matter intake by 39% and milk energy by 24%, and the high AFEX diet increased intake by 42% and milk energy by 18%. The AFEX treatment increased digestibilities of organic matter, dry matter, neutral detergent fiber, acid detergent fiber, and crude protein by 6 to 13 percentage points in buffalo and 5 to 10 points in cattle. In conclusion, AFEX treatment increased the digestibility and energy availability of wheat straw for lactating buffalo and cattle and has commercial potential to improve milk production and feed efficiency when high-quality forages or grains are not available.

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