Document Type : Original Article
Authors
1
Grup de Recerca en Remugants, Universitat Autònoma de Barcelona, Bellaterra, Spain+
2
Sheep & Goat Research Dept., Animal Production Research Institute, Dokki, Giza, Egypt.
3
Grup de Recerca en Remugants, Universitat Autònoma de Barcelona, Bellaterra, Spain.
Abstract
ABSTRACT
Pregnant multiparous Murciano-Granadina dairy goats (n = 17), kept under 1
kidding/year system (milk yield, 577 L in 300 d), were used to study the effects of dry
off period length on performances in the subsequent lactation. Goats were assigned to 2
experimental groups according to dry off treatment: goats that were dried off 56 d
before expected kidding (D56; n = 9) and goats without dry off (D0; n = 8). After
kidding, colostrum samples were obtained and kids were weighed before sucking. Milk
yield was recorded weekly during the preceding and subsequent lactations. Udders were
biopsied at d -65 (late lactation), d -49 d (during dry off) and d 48 (early lactation) to
kidding (d 0). Apoptotic and proliferating cells in mammary tissues were detected
immunohistochemically. Five goats (63%) in the D0 group dried off spontaneously at
27 ± 4 d before kidding, and were considered separately (D27). The rest of the D0 goats
yielded 0.86 L/d from d -56 to kidding. Goats kidded 2.25 kids/goat, but D0 kids had
lesser birth weight (1.7 kg) than D27 (2.2 kg) and D56 (2.1 kg). Colostrum of D0 goats
contained less IgG (5.6 mg/mL) than D27 (32.9 mg/mL) and D56 (42.4 mg/mL). In the
following lactation (210 d), D0 goats produced less milk (1.78 L/d) than D27 (2.51 L/d)
and D56 (2.24 L/d), with no differences between D27 and D56. Apoptosis and
proliferation indices increased from 0.51 and 2.09%, at d -65, to 1.75 and 7.12% at d -
49 (d 7 of dry off) in D56 goats. Despite differences in daily milk yield at early
lactation (d 48) between D0, D27 and D56 groups (1.73, 2.68, and 2.53 L/d;
respectively), no differences in apoptosis or proliferation indices were detected (D0,
0.65 and 2.48%; D27, 0.68 and 1.37%; and, D56, 0.71 and 2.95%), indicating that dry
period length did not affect mammary cell turnover in the subsequent lactation. In
conclusion, omitting the dry period between lactations reduced the quality of
colostrums and had negative effects on milk yield in dairy goats. Goats dried off
spontaneously for 27 d were as productive as goats dried for 56 d.
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