Twenty Holstein-Friesian cows, two to four months postpartum, were randomly assigned to two groups. The control group received no monensin, whereas the treatment group received 300 mg monensin per cow per day. Cows grazed kikuyu pasture and received maize-based concentrates (2% of body weight) in two equal feeds after the morning and afternoon milkings. Monensin was supplemented with the concentrates for six weeks. Monensin supplementation reduced the numbers (x 10 5 /cm 3) of small protozoa (9.1 vs. 13.0) and large protozoa (0.37 vs. 1.09) in the rumen. No significant difference was recorded between control and treatment groups for average milk yield (21.6 ± 0.7 vs. 22.1 ± 0.7 kg/day), milk protein (2.91 ± 0.05 vs. 2.84 ± 0.04 %) or milk fat (2.75 ± 0.13 vs. 2.69 ± 0.12 %). The combined morning and afternoon milk urea nitrogen concentrations of the monensin supplemented cows (19.9 ± 1.37 mg/dl) were lower than those of the control group (24.1 ± 1.43 mg/dl). The average daily gain of the treatment group (471.4 ± 87.5 g/day) was higher than that of the control group (193.9 ± 52.8 g/day). No significant difference was observed between the average condition score of the control (1.4 ± 0.1) and treatment (1.7 ± 0.1) groups after six weeks. Although monensin supplementation reduced milk urea nitrogen concentrations, these were still in the critical zone (> 18 mg/dl) which could negatively affect fertility. Monensin can play an important part in ensuring that cows are in a stable or improving condition (i.e. gaining weight) at service time, this being an important prerequisite for improved reproductive efficiency.

Milk production and milk composition responses to supplementation of Holstein-Friesian cows grazing kikuyu pasture in summer and a combination of annual ryegrass and maize silage in winter with 64 mg/d flavophospholipol were determined. There was no difference in the average milk yield over the first 100 days of lactation between the control group (19.8 kg/day) and the Flavomycin supplemented group (20.5 kg/day). Milk production over the full lactation of 300 days was also not influenced by Flavomycin addition (control: 5 525 kg; treatment: 5 627 kg). There was no difference between the control and treatment group in average butterfat percentage (3.55% vs. 3.62%), butterfat yield over 300 days (195.3 kg vs. 201.2 kg), average protein percentage (3.12% vs. 3.14%) or protein yield over 300 days (170.2 kg vs. 178.5 kg). Flavomycin addition only reduced the milk urea nitrogen (MUN) concentrations during the third week of April (treatment: 16.0 ± 0.8 mg MUN/dl; control: 18.6 ± 0.4 mg MUN/dl) and the second week of September (treatment: 16.0 ± 1.2 mg MUN/dl; control: 19.6 ± 0.9 mg MUN/dl). Cows grazing nitrogenfertilized pastures displayed great variation in weekly and monthly milk urea nitrogen concentrations which frequently exceed 18 mg MUN/dl.

Nguni cattle are a Sanga type breed with mixed B. taurus and B. indicus ancestry and proven resistance to ticks, diseases and other harsh conditions of the African geographical landscape. The multi-coloured Nguni coats have found a niche market in the leather industry leading to breeding objectives towards the promotion of such diversity. However, there is limited studies on the genomic architecture underlying the coat colour and patterns hampering any potential breeding and improvement of such trait. This study investigated the genetics of base coat colour, colour-sidedness and the white forehead stripe in Nguni cattle using coat colour phenotyped Nguni cattle and Illumina Bovine HD (770K) genotypes. Base coat colour phenotypes were categorised into eumelanin (n = 45) and pheomelanin (n = 19). Animals were categorised into either colour-sided (n = 46) or non-colour-sided (n = 94) and similarly into presence (n = 15) or absence (n = 67) of white forehead stripe. Genome-wide association tests were conducted using 622,103 quality controlled SNPs and the Efficient Mixed Model Association eXpedited method (EMMAX) implemented in Golden Helix SNP Variation Suite. The genome-wide association studies for base coat colour (eumelanin vs. pheomelanin) resulted into four indicative SNPs on BTA18 and a well-known gene, MC1R, was observed within 1 MB from the indicative SNPs (p < 0.00001) and found to play a role in the melanogenesis (core pathway for melanin production) and the MAPK signalling pathway. GWAS for colour-sidedness resulted in four indicative SNPs, none of which were in close proximity to the KIT candidate gene known for colour-sidedness. GWAS for the white forehead stripe resulted in 17 indicative SNPs on BTA6. Four genes MAPK10, EFNA5, PPP2R3C and PAK1 were found to be associated with the white forehead stripe and were part of the MAPK, adrenergic and Wnt signalling pathways that are synergistically associated with the synthesis of melanin. Overall, our results prove prior knowledge of the role of MC1R in base coat colours in cattle and suggested a different genetic mechanism for forehead stripe phenotypes in Nguni cattle.

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