Role of body condition score and body weight in the control of seasonal reproduction in Blanca Andaluza goats

Abstract

The reproductive activity of 84 female Blanca Andaluza goats was monitored over 17 months to determine the role of body condition score (BCS) and body weight (BW) in its control. Following a 3 × 2 factorial experimental design, the animals were allocated to three groups: low BCS (≤2.50, n = 24), medium BCS (BCS = 2.75–3.00, n = 31) and high BCS (≥3.25, n = 29). The same animals, irrespective of the BCS group categorization, were also divided into two groups depending on BW: low BW (≤40 kg, n = 44) and high BW (>40 kg, n = 40). Oestrus was evaluated daily using vasectomised males. The ovulation rate was assessed by trans-rectal ultrasonography after the identification of oestrus. Ovulations were determined by monitoring the plasma progesterone concentration weekly. The BCS and BW were recorded once a week and nutritional status adjusted to maintain the initial differences in BW and BCS between the groups. Both BCS and BW had a significant (at least P < 0.05) influence on the onset, the end, and the duration of the breeding season, with longer periods of reproductive activity recorded in does with a BCS of ≥2.75 and BW of >40 kg. No significant interaction between these variables was observed. Some (11.7%) of the does in the groups with animals of BCS ≥ 2.75 had ovulations during seasonal anoestrus. None of the does with a BCS of ≤2.5 had ovulations during seasonal anoestrus. The ovulation rate of the first and last oestrus was influenced by BW (P < 0.01). These results demonstrate that Blanca Andaluza goats show marked reproductive seasonality that is clearly and independently modulated by BCS and BW.