الفهرس 
Introduction
Description of the lactation curveOnly 14 pages are availabe for public view
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Abstract
Weekly milk production of 490 buffaloes raised at the subtropical Hawatka farm, some 20 km north of Assiut, wer• used to analyze the shape of 2560 lactations. This study was carried out for:
— Estimating shape of the lactation curve of Egyptian buffaloes using the gamma—type function.
— Studying the factors affecting shape of the lactation curve.
— Estimating the correlation coefficients between
parameters of the lactation curve, total milk yield (THY), 44 wk.ilk yield (NY44) and lactation period (Lp).
— Estimating the repeatability for all the studied tzaits.
The shape of the lactation curve was estimated for each individual lactation, utilizing the gamma—type function that has three coefficients (a, b and c). Week of peak yield (P a b/c), peak yield, kg, (Py a(b/c)beb) and persistency (P
— c(0t14) were estimated for each individual record and were analyzed as dependent variables in two models. One of them was a mixed model (model I) and the other was a fixed model (model II). Fixed effects of parity. year and season of calving as well as the interaction between the last two tens wer. included in the two models. Model (I) included a random cow effect in addition to the previous fixed effects.
Th, results showed that:
— The gamma—type function was suitable for describing the lactation curve of Egyptian buffaloes.
— Averages and standard errors of ln(a), b, C, Pts, Py and
were 3.07±.Ol, .54±.0l, .06±.OOl, l0.17±.12, 45.08±.36, 107.59±1.96, respectively as obtained from model (I) while those obtained from model (II) were 3.04±.01, .56±.01, .06±.00I, 9.69±.12, 43.60±.30 and 101.44±1.92, respectively.
— Averages and standard errors of total milk yield (THY),
44 wlc milk yield (MY44) and lactation period (Lp) were
1363±14 kg, 1290±12 kg and 288±2 d, respectively as obtained
from model (I) while those obtained from model (II) were
1295±11 kg, 1242±10 kg and 281±2 d, respectively.
— Model (I) revealed the cow effect on the lactation curve parameters and traits (p<.05) except R• Parity affected ln(a), w’ Py (p<.0l) and R (p<.0S) while season of calving affected, only, ln(a) and Py (p<.01). Year of calving had an effect on all parameters and traits (p<.05). The interaction between season and year of calving had an effect on ln(a), w’ Py and R (p<.0l). THY, MY44 and Lp were affected by the individual cow effect, parity and season of calving (p<.Ol) Only THY and MY were affected by year of calving and the interaction between season and year of calving (p<.O5) while Lp not affected by either of them.
— Model (II) showed that all lactation curve parameters and traits studied were influenced by parity and year of calving (p<.ool). Season of calving had, only, an effect (p<.Ool) on ln(a) and Py. The interaction between season and year of calving influenced all traits (p<.OOl) with the exception of parameters S and c. Parity and season of calving had an effect (p<.O01) on THY, MY44 and Lp. Year of calving had an effect (p<.001), only, on THY and MY44. THY,
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