Effects of herd, year, age, season, and lactation length on milk yield and reproductive efficiency for the Nili-Ravi breed of buffalo were determined by analysis of variance of 5,716 lactation records from two herds in Pakistan. Herds differed in all traits. Herd average milk yields were 1,702 and 2,064 kg. Year, season, herd, parity number, days in milk, days open, age, and sire all influenced milk yield. Herd, year, season, and parity number also had significant effects on days open and calving interval. Month of calving was important for time until return to estrus. Percentages of variance in milk yield attributed to herd, year, sire, cow, and residual were 20.3, 11.4, 4.3, 17.0, and 47.0. Classification of lactation length (greater than 60, greater than 250, or at least 305 days) markedly influenced the sire component of variance suggesting some interdependence of milk yield and lactation length. Total variance for milk yield was 466,911 kg2. Within herd heritability for milk yield was .25, and repeatability was low (.31). Predicted breeding values for sires for 250 to 305-day milk ranged from -172 kg to +260. Cows in Herd 1 completed 5.58 lactations with an average herd life of 12.3 yr; Herd 2 cows completed 4.52 lactations with culling at 10.6 yr. Frequency of termination of lactations because of mastitis, reproductive problems, or health was similar to frequencies for cattle. Factors affecting milk yield in buffaloes are similar to those of cattle.

Monthly fat tests for 895 lactations of Nili-Ravi buffaloes in a Livestock Production Research Institute herd were used to estimate environmental effects on fat percentage. Fat tests rose progressively from 1st to 10th mo of lactation (5.51 to 7.46%). Average lactation fat percent was 6.55 +/- .06. Year effects were significant, but season, age, parity, milk yield, and health status were not. Percent fat increased slightly to maturity (6.54 first parity; 6.65 fifth). Lactations initiated April to September averaged slightly higher (6.60%) than other months (6.50%). There was a slight, although real, decrease in fat percent with increased lactation milk yield (6.60, 6.63, 6.60, 6.43, 6.51 for 1000 to 1500, 1501 to 2000, 2001 to 2500, 2501 to 3000, and greater than 3,000 kg). Effect of treatment for health problems was small (6.51 treated versus 6.59% untreated). Of all fat tests (7,772) 60% were 5.1 to 7.0%, 27% were between 7 and 9%, but only 3% exceeded 9%. Lactation fat percent averaged 1.0 less than most percents for buffaloes because of system of milking and milk yield (2,130 kg). Fat percentage of buffaloes appears to be influenced by environmental factors in the same proportion as for cattle, but buffaloes would be expected to exceed cattle in fat percent by 1 to 3% depending on breed and environmental conditions.

Nineteen pluriparous buffaloes of Nili-Ravi breed which calved during the months of October and November 1983 were studied for the effects of sucking stimulus on the uterine involution, post-partum ovarian functions and fertility. On the day of calving, buffaloes were assigned to either a limited-suckling (LS) or non-suckling (NS) group. Changes in reproductive organs were monitored by rectal palpations at weekly intervals. Buffaloes were observed for oestrus twice daily (04.00 and 18.00 h) with the help of a teaser bull, and were artificially inseminated at the first post-partum and each subsequent oestrus. LS buffaloes had a shorter period to uterine involution (20 days) than NS buffaloes (28 days). Intervals to regression of the corpora lutea of pregnancy and to resumption of post-partum follicular development did not differ in the two groups. LS buffaloes had longer intervals to first post-partum oestrus and conception (54 and 88 days respectively) than NS buffaloes (39 and 68 days respectively). However, the difference in services per conception of LS and NS buffaloes was non-significant (2-05 v. 1·62). These limited data reveal that the suckling stimulus has a negative effect on the post-partum resumption of oestrous activity, and that conception is delayed. Further studies are indicated to verify these observations in a larger sample size and during all seasons of the year.

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