Dairy buffalo is the major source of milk production kept under peri-urban, low input production system. There is no practice of feeding animals according to production requirements; exposing them to nutritional deficiency with the onset of pregnancy. The onset of pregnancy leads to a decline in milk yield, which compels the farmers to keep the animals un-bred. The present work was completed under four studies to investigate the post-conception decline in milk yield in relation to feeding regime and milk progesterone levels. The overall economic losses due to delayed breeding were also investigated.
Study-I, A total of 30912 weekly milk yield records of lactations pertaining to 465 pregnant and 179 non-pregnant buffaloes from three different locations were recorded for 48 weeks. Post conception reduction in milk yield was effected by location, conception season, lactation week, gestation month and parity. Gestation month contributed to the .reduction in milk yield by 1.4%. Parity 3 showed the least reduction followed by parity 2, 4, 1, 5, and 6, indicating it as the best phase for milk production in dairy buffaloes. Under the Study-II reduction in milk yield due to pregnancy was worked out as the difference between milk yield of 23 pregnant and 17 non-pregnant buffaloes, through various models. The buffaloes were provided with three treatments: i) pregnant-ration-traditional (PRT); ii) pregnant-ration-supplemented (PRS) and; iii) non-pregnant-ration-traditional (NPRT). The animals were categorized into HMY; MMY, LMY, producing 66-75, 5665, and 46-55 liters per week, respectively. Milk production was recorded up to 23rd week and the difference in means was worked out. The reduction in milk yield was apparent after 5th week of conception and was significant in 17th week. The line JP8 model (two straight lines with joining point at week 8) gave good fit (R2 = 0.9527) and the predicted values were much closer to the actual. The treatment effect was significant after 6th week post conception. In MMY the supplementation support to milk yield was smaller than the HMY. In LMY buffaloes the decline was drastic in PRT than the other two treatments.
In Study-III, Forty adult lactating dairy buffaloes were investigated from 1st to 23rd weeks post-conception at a peri-urban dairy farm in Pakistan. The animals were assigned to three treatments: PRT (pregnant-ration traditional), PRS (pregnant-ration supplemented), NPRT (non-pregnant- ration traditional) and three milk yielding (MY) groups (HMY, high, 66 to 75 liter/wk, n=12; MMY, moderate, 56 to 65 liter/wk, n=16; LMY, low, 46 to 55 liter/wk, n=12). Milk samples were collected on alternate weeks. Milk composition was determined through ultrasonic milk analyzer. EIA (enzyme immunoassay) was used for MPL .Groups means were compared and correlation analysis was conducted. The trends of milk yield as affected by progesterone concentration were analyzed using a regression model based on joining point of the two phases.
Differences in MPL became significant among the production groups after 8 weeks of conception. Treatment had a significant effect on MPL. Interaction of production groups was significant with treatments during the 2-8 weeks and with weeks post conception during 10-23 weeks. Treatment x week interaction was significant only during 2-8 weeks. MPL increased in a similar pattern with the advancing weeks post-conception in all the three production groups; however the progesterone levels were slightly but constantly higher in LMY followed by MMY and HMY buffaloes. The HMY and LMY buffaloes showed greater MPL in the supplemented than the animals on traditional ration (P<0.001). MPL correlated positively with fat (%) while negatively with milk yield, protein (%) and lactose contents (%). Decrease in milk yield was mild with the increasing progesterone levels up to 6.44 ng/ml but further increase in the MPL decreased the yield drastically. The PRT animals showed a sharp decline in milk yield with increasing progesterone levels. However, in the PRS animals increasing MPL from 2.0 to 5.84 ng/ml did not affect the milk yield while further increase in MPL resulted in a decrease in milk yield.
In Study-IV, Complete milk yield records of 3,304 buffaloes were collected from a group of state farms. Economic traits including lactation yield, lactation length, calving interval (CT), dry period and milk yield per day of calving interval (MYPDCI) were derived from the data. The animals were grouped according to parity number (1-3), service period (GI to G4, conceiving during <150, 150-200, 200-300 and >300 days), respectively and milk yield levels as HMY>2,500; MMY 2,001-2,500; and LMY 1,500-2,000 liters/lactation. The effect of pregnancy on milk composition was investigated in a medium size private dairy farm, using forty lactating buffaloes of three yield levels and four service period groups as described, already. Milk was sampled on the alternate weeks and analyzed for fat and protein contents (%). For quantifying the value of milk produced during a lactation period; the value corrected milk (VCM) was determined and converted to lactation milk value (LMV). Group means were compared for various parameters. Highest milk yield (2,836.50±15.68 liters/lactation) was recorded in the HMY animals of G4 group while lowest milk yield of 1 ,657.04±8.34 liters/lactation was found in LMY of GI. Lactation length was significantly increased with the increasing service period. The shortest dry period was recorded in HMY, parity 1, GI animals and the longest in parity 2, MMY, G4. The CI was shortest in HMY, parity I, and GI animals and longest in LMY, parity 3, G4 buffaloes. The HMY, parity 2, GI buffaloes showed the highest MYPDCT and the lowest value (6.53±0.17 vs 2.76±0.04 liter/day) was recorded for LMY, parity 1, G4 buffaloes. The VCM decreased with the delayed conception. This decreasing trend was higher in respect to the total yield but the decrease in the VCM was smaller due to the increasing levels of fat and protein contents in the milk. The gap among various production classes was reduced while looking at the VCM as compared to the milk yield per day of CI. The LMV showed a consistent decline with the extending service period in all the three production groups.
In conclusion, the onset of pregnancy in dairy buffaloes results a drastic decline in milk yield at an early stage and the high milk producers are more sensitive to this decline. Buffalo does not loose her body condition rather decrease her milk yield rapidly than cattle, after the onset of pregnancy. A pregnant animal, if supplemented at the rate of 1 kg ration for every 2 liters of milk will retain milk yield level for a longer duration post- conception. In high milk producers the cost of this supplementation was ten times less than the loss due to milk yield decline after the onset of pregnancy. Increase in MPL with an almost constant linear trend in dairy buffaloes was reported. Concentrates supplementation raised progesterone levels probably through reducing production stress. The critical level of 6.4 ng/ml of MPL caused drastic decline in milk yield while the two parameters also' showed a constant inverse relationship in buffaloes. An animal conceiving at later stages of lactation showed a decline in financial returns by 24-27% than those conceiving earlier.