ABSTRACT
This study was conducted to determine the effect of feed supplementation during the postpartum period on the growth and reproductive performance of 40 grazing Sanga and Friesian x Sanga cows in the coastal savannah zone of Ghana. Twenty out of the total of 40 cows (10 Sanga and 10 Friesian x Sanga crossbred cows) were supplemented with 2.5 kg of concentrate per day during the period of study. All cows were weighed weekly and scored for body condition once every week using the 9-point scale (1= very thin to 9 = obese). Also, partial milk yields of all cows were determined daily during the study. Blood samples were taken from cows from week 1 to 16 postpartum and processed for plasma. The concentrations of blood metabolites [glucose, total protein, albumin, globulin, triglycerides, urea, non-esterified fatty acid (NEFA) and beta-hydroxybutyrate (BHB)] were assessed at two-weekly intervals (weeks 1, 3, 5, 7, 9, 11, 13 and 15). Resumption of postpartum ovarian cyclicity was determined by measuring progesterone concentration in the plasma from week 1 to 16 in the cows. Cows were classified as having resumed ovarian activity when a plasma progesterone concentration of ≥ 1.0 ng/mL was recorded for two consecutive weekly samples. In the current study, there was no significant differences (P
> 0.05) in the body weight gain and body condition score of supplemented and non- supplemented cows. Supplemented cows had higher partial milk yield than their non- supplemented counterparts (2.07 versus 1.60 L/day; P < 0.001). Sanga cows tended to have better body condition score (7.50 versus 6.84; P < 0.079), but lower milk yield (1.61 versus 2.05 L/day; P = 0.001) than the Friesian x Sanga cows. Supplemented Sanga cows recorded a lower milk yield than the supplemented Friesian x Sanga cows (1.67 versus 2.50 L/day; P < 0.001). With respect to dietary regime, supplemented cows recorded higher total protein (86.7 versus 81.3 g/L; P = 0.007) and globulin (53.0 versus 47.7 g/L; P = 0.014)
than non-supplemented cows. Sanga cows had higher glucose (4.43 versus 4.09 mmol/L; P = 0.027), total protein (84.0 versus 73.1 g/L; P < 0.001) globulin (47.5 versus 40.1 g/L; P < 0.001), but lower triglycerides (0.25 versus 0.27 mmol/L; P = 0.003) and progesterone (0.58 versus 3.79 ng/mL; P = 0.023) concentrations than Friesian x Sanga cows. Supplemented Sanga cows had lower progesterone concentration than supplemented Friesian x Sanga cows (0.06 versus 6.11 ng/mL; P < 0.001). The interval from calving to resumption of ovarian activity was similar (P > 0.05) in supplemented (53.5 ± 6.27 days) and non-supplemented cows (63.0 ± 8.33 days), however, supplemented cows had lower proportion of non-cycling cows than non-supplemented cows (20 versus 55%; P = 0.022). Also the interval from calving to conception (days open) was shorter in supplemented than non-supplemented cows (95.8 ± 2.96 versus 106 ± 2.83 days; P = 0.032). Friesian x Sanga cows had higher progesterone concentrations at 1st progesterone rise (3.34 ± 1.39 versus
1.32 ± 0.09 ng/mL; P = 0.032) and shorter interval from calving to conception (96.7 ± 2.96 versus 106 ± 2.38 days; P = 0.042) than Sanga cows. Supplemented Friesian x Sanga cows resumed ovarian activity earlier (43.3 versus 67.7 days; P = 0.032) and had shorter interval from calving to conception (92 versus 102.7 days; P = 0.052) than supplemented Sanga cows. In addition, all (100%) the supplemented Friesian x Sanga cows resumed ovarian activity while 40% of the supplemented Sanga cows did not resume cyclicity during the period of study. Based on the resumption of ovarian activity, cows were classified as Early- cycling, Late-cycling and Non-cycling. For Sanga cows, 6 resumed ovarian cyclicity early (by 56 days postpartum), 5 resumed ovarian activity late (within 57-112 days postpartum), and 9 failed to resume ovarian cyclicity (by 112 days postpartum). For Friesian x Sanga cows, 7 resumed ovarian cyclicity early (by 56 days postpartum), 7 resumed ovarian activity late (within 57-112 days postpartum) while 6 failed to resume ovarian cyclicity (by
112 days postpartum). Early (2.54 L/day) and Late (2.01 L/day) cycling Friesian x Sanga cows had higher (P = 0.011) milk yield than Non-cycling (1.61 L/day) cows. Early-cycling Sanga cows had lower total protein than Late-cycling and Non-cycling cows (76.8 versus 89.3, 83.1 g/L; P < 0.05). Globulin concentration was also lower (P < 0.05) in Early (42.6 g/L) than Late (54.2 g/L) and Non-cycling (49.7 g/L) cows. Partial correlation coefficients among concentrations of the plasma metabolites, glucose, total protein, albumin, globulin, triglycerides, BHB, NEFA and urea indicated negative and significant correlation between glucose and total protein (r = -0.255; P < 0.01), globulin (r = -0.200; P < 0.01) and triglyceride (r = – 0.2550; P < 0.01). Total protein was significant and positively correlated with albumin (r = 0.371; P < 0.01), globulin (r = 0.763; P < 0.01) and triglyceride (r = 0.485; P < 0.01). Albumin was significant and negatively correlated with globulin (r = – 0.317; P < 0.01), but significant and positively correlated with triglyceride (r = 0.473; P < 0.01), BHB (r = 0.218; P < 0.01) and NEFA (r = 0.183; P < 0.05). Globulin was positive and significantly correlated with triglyceride (r = 0.166; P < 0.01), while triglyceride was significant and negatively correlated with urea (r = -0.119; P < 0.05) and NEFA (r = -0.188; P < 0.05).
The results from this study indicate the beneficial effects of feed supplementation in terms of increased milk yield, improved metabolic status, less cyclicity problems and less days open. The beneficial effects of feed supplementation to the Friesian x Sanga than Sanga cows in the production environment was also demonstrated.
