Mammogenesis and induced lactation with or without reserpine in nulliparous dairy goats.
Nulliparous goats were used to evaluate the effects of a standard protocol for inducing lactation with or without using a prolactin-releasing agent (reserpine). Estrus was synchronized and goats were submitted to daily s.c. injections of estradiol-17beta and progesterone (0.5 and 1.25 mg/kg of body weight, respectively) for 7 d. The goats were divided into 2 groups and injected i.m. with 1 mg/d of reserpine (n = 7) or the vehicle (n = 7) on d 12, 14, 16, 18, and 20. Lactation was initiated by i.m. injections of dexamethasone (10 mg/d) from d 18 to 20. Goats were machine milked once daily from d 21 to 120, at which time they were mated with herd sires. Milk was measured and sampled daily during wk 1 of lactation and weekly thereafter. Udder traits were measured in all goats at d -2 (before the induction treatment) and on d 35 and 100 (during lactation). Goats initiated lactation on d 21 (100%) and milk yield increased thereafter. The milk yield of control and reserpine-treated goats increased as lactation advanced, peaking at wk 10 of lactation, when reserpine-treated goats yielded 1,079 +/- 89 mL/d of milk compared with 850 +/- 96 mL/d for control goats. Yet milk yield at the peak was only 55% of the peak milk yield observed in contemporary primiparous goats. The composition of initial milk (d 21) was different from that expected for colostrum. Milk composition stabilized after d 3 of lactation. There were no differences among groups for milk fat, protein, casein, or whey protein, but milk from control goats contained greater nonprotein nitrogen than that from reserpine-treated goats (0.48 +/- 0.02 vs. 0.41 +/- 0.02%). Teat length increased from 24.7 +/- 1.1 to 34.5 +/- 2.4 mm in control goats during mammogenesis (d -2 to 35), but stabilized in reserpine goats (25.2 +/- 2.2 mm). The distance between teats (11.5 +/- 0.4 cm), and the volume (922 +/- 63 mL) and depth (15.6 +/- 0.60 cm) of the udder increased similarly in both groups during mammogenesis and lactation. After mating, 82% of herdmates became pregnant, whereas only 21% of the lactation-induced goats conceived (1 reserpine-treated and 2 control goats). In conclusion, lactation induction was effective in nulliparous goats, but neither milk yield nor the side effects on fertility seem to support its recommendation.
Salama
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Grup de Recerca en Remugants, Departament de Ciència Animal i dels Aliments, Universitat Autònoma de Barcelona, Bellaterra, Spain. ahmed.salama@uab.es
Caja
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Albanell
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Carné
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Casals
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Such
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D018759:Adrenergic Uptake Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D003612:Dairying / Q000379:methods; D003907:Dexamethasone / Q000008:administration & dosage; D004958:Estradiol / Q000008:administration & dosage; D004973:Estrus Synchronization; D005260:Female; D005298:Fertility / Q000187:drug effects; D006041:Goats / Q000502:physiology*; D007273:Injections, Intramuscular / Q000662:veterinary; D007774:Lactation / Q000187:drug effects* / Q000502:physiology; D008321:Mammary Glands, Animal / Q000187:drug effects* / Q000502:physiology; D008892:Milk / Q000737:chemistry / Q000378:metabolism; D011247:Pregnancy; D011374:Progesterone / Q000008:administration & dosage; D012110:Reserpine / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
D018759:Adrenergic Uptake Inhibitors; D011374:Progesterone; D004958:Estradiol; D003907:Dexamethasone; D012110:Reserpine